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Sample records for dental stress analysis

  1. Viscoelastic finite element analysis of residual stresses in porcelain-veneered zirconia dental crowns.

    Science.gov (United States)

    Kim, Jeongho; Dhital, Sukirti; Zhivago, Paul; Kaizer, Marina R; Zhang, Yu

    2018-06-01

    The main problem of porcelain-veneered zirconia (PVZ) dental restorations is chipping and delamination of veneering porcelain owing to the development of deleterious residual stresses during the cooling phase of veneer firing. The aim of this study is to elucidate the effects of cooling rate, thermal contraction coefficient and elastic modulus on residual stresses developed in PVZ dental crowns using viscoelastic finite element methods (VFEM). A three-dimensional VFEM model has been developed to predict residual stresses in PVZ structures using ABAQUS finite element software and user subroutines. First, the newly established model was validated with experimentally measured residual stress profiles using Vickers indentation on flat PVZ specimens. An excellent agreement between the model prediction and experimental data was found. Then, the model was used to predict residual stresses in more complex anatomically-correct crown systems. Two PVZ crown systems with different thermal contraction coefficients and porcelain moduli were studied: VM9/Y-TZP and LAVA/Y-TZP. A sequential dual-step finite element analysis was performed: heat transfer analysis and viscoelastic stress analysis. Controlled and bench convection cooling rates were simulated by applying different convective heat transfer coefficients 1.7E-5 W/mm 2 °C (controlled cooling) and 0.6E-4 W/mm 2 °C (bench cooling) on the crown surfaces exposed to the air. Rigorous viscoelastic finite element analysis revealed that controlled cooling results in lower maximum stresses in both veneer and core layers for the two PVZ systems relative to bench cooling. Better compatibility of thermal contraction coefficients between porcelain and zirconia and a lower porcelain modulus reduce residual stresses in both layers. Copyright © 2018 Elsevier Ltd. All rights reserved.

  2. An analysis of clinical transition stresses experienced by dental students: A qualitative methods approach.

    Science.gov (United States)

    Botelho, M; Gao, X; Bhuyan, S Y

    2018-04-17

    Stress in dental students is well established with potential psychological distress, emotional exhaustion and burnout-related symptoms. Little attention has been given to the problems encountered by dental students during the transition from theoretical or paraclinical training to the clinical environment. The aim of this study was to adopt a qualitative research methods approach to understand the perceived stressors during students' clinical transition and provide insights for curriculum planners to enhance learning. This study analysed four groups of 2nd- and 3rd-year BDS students' experiences in focus group interviews relating to their pre-clinical and clinical transitions. The interviews were recorded and transcribed verbatim, and a thematic analysis was performed using an inductive qualitative approach. Key overlapping domains identified were the transition gap and stresses. The transition gap was subclassified into knowledge and skill (hard and soft), and stresses was subcategorised into internal and external stresses. On first coming to clinics, students experienced knowledge gaps of unfamiliar clinical treatments with mismatches between knowledge acquisition and clinical exposure. Students felt incompetent owing to the stresses attributable to curriculum design, staff and the patient. This negatively affected their confidence and clinical performance. A range of challenges have been identified that will allow curriculum designer's to plan a more supportive learning experience to help students during their transition to clinical practice giving them timely knowledge, confidence and clinical performance to better prepare them for entering clinics. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  3. Comparative analysis of stress in a new proposal of dental implants.

    Science.gov (United States)

    Valente, Mariana Lima da Costa; de Castro, Denise Tornavoi; Macedo, Ana Paula; Shimano, Antonio Carlos; Dos Reis, Andréa Cândido

    2017-08-01

    The purpose of this study was to compare, through photoelastic analysis, the stress distribution around conventional and modified external hexagon (EH) and morse taper (MT) dental implant connections. Four photoelastic models were prepared (n=1): Model 1 - conventional EH cylindrical implant (Ø 4.0mm×11mm - Neodent®), Model 2 - modified EH cylindrical implant, Model 3 - conventional MT Conical implant (Ø 4.3mm×10mm - Neodent®) and Model 4 - modified MT conical implant. 100 and 150N axial and oblique loads (30° tilt) were applied in the devices coupled to the implants. A plane transmission polariscope was used in the analysis of fringes and each position of interest was recorded by a digital camera. The Tardy method was used to quantify the fringe order (n), that calculates the maximum shear stress (τ) value in each selected point. The results showed lower stress concentration in the modified cylindrical implant (EH) compared to the conventional model, with application of 150N axial and 100N oblique loads. Lower stress was observed for the modified conical (MT) implant with the application of 100 and 150N oblique loads, which was not observed for the conventional implant model. The comparative analysis of the models showed that the new design proposal generates good stress distribution, especially in the cervical third, suggesting the preservation of bone tissue in the bone crest region. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Stress and Reliability Analysis of a Metal-Ceramic Dental Crown

    Science.gov (United States)

    Anusavice, Kenneth J; Sokolowski, Todd M.; Hojjatie, Barry; Nemeth, Noel N.

    1996-01-01

    Interaction of mechanical and thermal stresses with the flaws and microcracks within the ceramic region of metal-ceramic dental crowns can result in catastrophic or delayed failure of these restorations. The objective of this study was to determine the combined influence of induced functional stresses and pre-existing flaws and microcracks on the time-dependent probability of failure of a metal-ceramic molar crown. A three-dimensional finite element model of a porcelain fused-to-metal (PFM) molar crown was developed using the ANSYS finite element program. The crown consisted of a body porcelain, opaque porcelain, and a metal substrate. The model had a 300 Newton load applied perpendicular to one cusp, a load of 30ON applied at 30 degrees from the perpendicular load case, directed toward the center, and a 600 Newton vertical load. Ceramic specimens were subjected to a biaxial flexure test and the load-to-failure of each specimen was measured. The results of the finite element stress analysis and the flexure tests were incorporated in the NASA developed CARES/LIFE program to determine the Weibull and fatigue parameters and time-dependent fracture reliability of the PFM crown. CARES/LIFE calculates the time-dependent reliability of monolithic ceramic components subjected to thermomechanical and/Or proof test loading. This program is an extension of the CARES (Ceramics Analysis and Reliability Evaluation of Structures) computer program.

  5. Stress Among Dental Students

    NARCIS (Netherlands)

    A.M. Alzahem (Abdullah)

    2015-01-01

    markdownabstractAbstract Dental students are facing many stressors in dental education, causing many negative outcomes. The most common are the exams and the clinical requirements. We suggest exposing the dental students to patient care as early as possible in their curriculum. This can help to

  6. Polymerization stresses in low-shrinkage dental resin composites measured by crack analysis.

    Science.gov (United States)

    Yamamoto, Takatsugu; Kubota, Yu; Momoi, Yasuko; Ferracane, Jack L

    2012-09-01

    The objective of this study was to compare several dental restoratives currently advertised as low-shrinkage composites (Clearfil Majesty Posterior, Kalore, Reflexions XLS Dentin and Venus Diamond) with a microfill composite (Heliomolar) in terms of polymerization stress, polymerization shrinkage and elastic modulus. Cracks were made at several distances from the edge of a precision cavity in a soda-lime glass disk. The composites were placed into the cavity and lengths of the cracks were measured before and after light curing. Polymerization stresses generated in the glass at 2 and 10 min after the irradiation were calculated from the crack lengths and K(c) of the glass. Polymerization shrinkage and elastic modulus of the composites also were measured at 2 and 10 min after irradiation using a video-imaging device and a nanoindenter, respectively. The data were statistically analyzed by ANOVAs and Tukey's test (pelastic moduli of Clearfil Majesty Posterior and Reflexions XLS Dentin were greatest at 2 and 10 min, respectively. Among the four low-shrinkage composites, two demonstrated significantly reduced polymerization stress compared to Heliomolar, which has previously been shown in in vitro tests to generate low curing stress. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  7. Stress and strain distribution in three different mini dental implant designs using in implant retained overdenture: a finite element analysis study.

    Science.gov (United States)

    Aunmeungtong, W; Khongkhunthian, P; Rungsiyakull, P

    2016-01-01

    Finite Element Analysis (FEA) has been used for prediction of stress and strain between dental implant components and bone in the implant design process. Purpose of this study was to characterize and analyze stress and strain distribution occurring in bone and implants and to compare stress and strain of three different implant designs. Three different mini dental implant designs were included in this study: 1. a mini dental implant with an internal implant-abutment connection (MDIi); 2. a mini dental implant with an external implant-abutment connection (MDIe); 3. a single piece mini dental implant (MDIs). All implant designs were scanned using micro-CT scans. The imaging details of the implants were used to simulate models for FEA. An artificial bone volume of 9×9 mm in size was constructed and each implant was placed separately at the center of each bone model. All bone-implant models were simulatively loaded under an axial compressive force of 100 N and a 45-degree force of 100 N loading at the top of the implants using computer software to evaluate stress and strain distribution. There was no difference in stress or strain between the three implant designs. The stress and strain occurring in all three mini dental implant designs were mainly localized at the cortical bone around the bone-implant interface. Oblique 45° loading caused increased deformation, magnitude and distribution of stress and strain in all implant models. Within the limits of this study, the average stress and strain in bone and implant models with MDIi were similar to those with MDIe and MDIs. The oblique 45° load played an important role in dramatically increased average stress and strain in all bone-implant models. Mini dental implants with external or internal connections have similar stress distribution to single piece mini dental implants. In clinical situations, the three types of mini dental implant should exhibit the same behavior to chewing force.

  8. Finite element analysis of the stress distributions in peri-implant bone in modified and standard-threaded dental implants

    Directory of Open Access Journals (Sweden)

    Serkan Dundar

    2016-01-01

    Full Text Available The aim of this study was to examine the stress distributions with three different loads in two different geometric and threaded types of dental implants by finite element analysis. For this purpose, two different implant models, Nobel Replace and Nobel Active (Nobel Biocare, Zurich, Switzerland, which are currently used in clinical cases, were constructed by using ANSYS Workbench 12.1. The stress distributions on components of the implant system under three different static loadings were analysed for the two models. The maximum stress values that occurred in all components were observed in FIII (300 N. The maximum stress values occurred in FIII (300 N when the Nobel Replace implant is used, whereas the lowest ones, in the case of FI (150 N loading in the Nobel Active implant. In all models, the maximum tensions were observed to be in the neck region of the implants. Increasing the connection between the implant and the bone surface may allow more uniform distribution of the forces of the dental implant and may protect the bone around the implant. Thus, the implant could remain in the mouth for longer periods. Variable-thread tapered implants can increase the implant and bone contact.

  9. Stress and burnout among Swiss dental residents

    OpenAIRE

    Divaris, Kimon; Lai, Caroline S; Polychronopoulou, Argy; Eliades, Theodore; Katsaros, Christos

    2012-01-01

    Stress and burnout have been well-documented in graduate medical and undergraduate dental education, but studies among dental graduate students and residents are sparse. The purpose of this investigation was to examine perceived stressors and three dimensions of burnout among dental residents enrolled in the University of Bern, Switzerland. Thirty-six residents enrolled in five specialty programmes were administered the Graduate Dental Environment Stress (GDES30) questionnaire and the Maslach...

  10. Perceived stress in dental practice.

    Science.gov (United States)

    Pop-Jordanova, Nada; Radojkova-Nikolovska, Vera; Markovska-Simoska, Silvana

    2013-01-01

    Stress is a normal physiological response to events that make us feel threatened, or upset our balance in some way. In medicine, it is known that stress, as an emotional state, can be a trigger for many psychosomatic disorders. Work stress and burnout are considered to be serious professional risks in dentistry. The dentist should be aware of these stressors and attempt to manage them in order to avoid becoming occupationally dissatisfied. On the other hand, the other common characteristic of modern life is a growing burden of different chronic diseases. Periodontal disease is one of the two most important oral diseases contributing to the global burden of chronic disease. The aim of this study was to assess the perceived stress in patients with periodontal pathologies, and to compare it with the stress in doctors-dentists and students of dentistry as future professionals. Our study confirmed the presence of significant stress in all three groups of examinees (patients, doctors, and students). Surprisingly, the obtained PSQ scores are similar in the examined groups. In addition, no differences between perceived stress in males and females have been found. There is a minimal positive correlation between age and obtained scores. However, stress must be evaluated as a risk factor both for professionals or for chronic dental patients and some response measures must be undertaken.

  11. Depression, anxiety and stress in dental students.

    Science.gov (United States)

    Basudan, Sumaya; Binanzan, Najla; Alhassan, Aseel

    2017-05-24

    To measure the occurrence and levels of depression, anxiety and stress in undergraduate dental students using the Depression, Anxiety and Stress Scale (DASS-21). This cross-sectional study was conducted in November and December of 2014. A total of 289 dental students were invited to participate, and 277 responded, resulting in a response rate of 96%. The final sample included 247 participants. Eligible participants were surveyed via a self-reported questionnaire that included the validated DASS-21 scale as the assessment tool and questions about demographic characteristics and methods for managing stress. Abnormal levels of depression, anxiety and stress were identified in 55.9%, 66.8% and 54.7% of the study participants, respectively. A multiple linear regression analysis revealed multiple predictors: gender (for anxiety b=-3.589, p=.016 and stress b=-4.099, p=.008), satisfaction with faculty relationships (for depression b=-2.318, p=.007; anxiety b=-2.213, p=.004; and stress b=-2.854, prelationships (for depression b=-3.527, panxiety b=-2.213, p=.004; and stress b=-2.854, pstress b=-2.648, p=.045). The standardized coefficients demonstrated the relationship and strength of the predictors for each subscale. To cope with stress, students engaged in various activities such as reading, watching television and seeking emotional support from others. The high occurrence of depression, anxiety and stress among dental students highlights the importance of providing support programs and implementing preventive measures to help students, particularly those who are most susceptible to higher levels of these psychological conditions.

  12. Stress and strain distribution in three different mini dental implant designs using in implant retained overdenture: a finite element analysis study

    Science.gov (United States)

    AUNMEUNGTONG, W.; KHONGKHUNTHIAN, P.; RUNGSIYAKULL, P.

    2016-01-01

    SUMMARY Finite Element Analysis (FEA) has been used for prediction of stress and strain between dental implant components and bone in the implant design process. Purpose Purpose of this study was to characterize and analyze stress and strain distribution occurring in bone and implants and to compare stress and strain of three different implant designs. Materials and methods Three different mini dental implant designs were included in this study: 1. a mini dental implant with an internal implant-abutment connection (MDIi); 2. a mini dental implant with an external implant-abutment connection (MDIe); 3. a single piece mini dental implant (MDIs). All implant designs were scanned using micro-CT scans. The imaging details of the implants were used to simulate models for FEA. An artificial bone volume of 9×9 mm in size was constructed and each implant was placed separately at the center of each bone model. All bone-implant models were simulatively loaded under an axial compressive force of 100 N and a 45-degree force of 100 N loading at the top of the implants using computer software to evaluate stress and strain distribution. Results There was no difference in stress or strain between the three implant designs. The stress and strain occurring in all three mini dental implant designs were mainly localized at the cortical bone around the bone-implant interface. Oblique 45° loading caused increased deformation, magnitude and distribution of stress and strain in all implant models. Conclusions Within the limits of this study, the average stress and strain in bone and implant models with MDIi were similar to those with MDIe and MDIs. The oblique 45° load played an important role in dramatically increased average stress and strain in all bone-implant models. Clinical implications Mini dental implants with external or internal connections have similar stress distribution to single piece mini dental implants. In clinical situations, the three types of mini dental implant

  13. Evaluation of Stress Distribution of Mini Dental Implant-Supported Overdentures in Complete Cleft Palate Models: A Three-Dimensional Finite Element Analysis Study.

    Science.gov (United States)

    Soğancı, Gökçe; Yazıcıoğlu, Hüseyin

    2016-01-01

    Mini dental implants could be an alternative treatment method for prosthetic treatment of edentulous cleft palate. The aim of this study was to analyze stress distribution around the cortical bone and different plans using a varied number of mini dental implants in edentulous unilateral complete cleft palates. Three edentulous maxillary models were modified to create unilateral complete cleft palates. Mini dental implants (2.4 × 15 mm) were located as two mini implants at the premolar region, four mini implants at the premolar and molar region, and six mini implants at the first premolar, second premolar, and first molar regions in the models, respectively. Mucosa, o-ring/ball attachments, and overdentures were simulated. Vertical and horizontal loads of 100 N were applied on both the right and left molar teeth of the overdenture for each model. Maximum and minimum principal stress values and the distribution at cortical bone around the implants and cleft palates were evaluated by finite element analysis. Stress values under vertical loads were lower than values under horizontal loadings for all models. Stress values were found to be lower in the first model than in the second and third models. The highest stress values were found around implants in the second model. The unilateral feature of a complete cleft pattern affected the stress distribution. Stresses occured mostly around implants when the overdenture was supported by six implants; however, the stress distribution around implants was low with two implants because of tissue support.

  14. Occupational Stress in Dental Practice amongst Government ...

    African Journals Online (AJOL)

    Objectives: The aim of this study is to compare the level of occupational stress amongst government-employed and private dental practitioners in eastern Nigeria. Materials and methods: A total of 62 questionnaires were randomly distributed among government-employed and private practicing dental surgeons with five ...

  15. Depression, anxiety and stress in dental students

    OpenAIRE

    Basudan, Sumaya; Binanzan, Najla; Alhassan, Aseel

    2017-01-01

    Objectives To measure the occurrence and levels of depression, anxiety and stress in undergraduate dental students using the Depression, Anxiety and Stress Scale (DASS-21). Methods This cross-sectional study was conducted in November and December of 2014. A total of 289 dental students were invited to participate, and 277 responded, resulting in a response rate of 96%. The final sample included 247 participants. Eligible participants were surveyed via a self-reported questionnaire that includ...

  16. Stress and burnout among Swiss dental residents.

    Science.gov (United States)

    Divaris, Kimon; Lai, Caroline S; Polychronopoulou, Argy; Eliades, Theodore; Katsaros, Christos

    2012-01-01

    Stress and burnout have been well-documented in graduate medical and undergraduate dental education, but studies among dental graduate students and residents are sparse. The purpose of this investigation was to examine perceived stressors and three dimensions of burnout among dental residents enrolled in the University of Bern, Switzerland. Thirty-six residents enrolled in five specialty programmes were administered the Graduate Dental Environment Stress (GDES30) questionnaire and the Maslach Burnout Inventory (MBI). Individual stress items and overall GDES30 scores were used to quantify perceived stress. To measure burnout, proportions of burnout "cases" and MBI subscale scores were computed in the domains of emotional exhaustion (EE), depersonalization (DP) and reduced personal accomplishment (PA). Analyses relied on descriptive and bi-variate methods. The mean GDES30 score was 2.1 (SD = 0.4). "Lack of leisure time", "meeting the research requirement of the programme" and "completing graduation requirements" emerged as the top three stressors. Thirty-six percent of respondents were burnout "cases" on the PA scale, while this proportion was 17% for EE and 8% for DP. Both stress and burnout levels increased according to year of study, whereas younger residents and females had consistently higher stress and burnout scores compared to older ones and males. Overall, low levels of perceived stress and burnout were found among this group of Swiss dental residents.

  17. Professional burnout and work stress among Israeli dental assistants.

    Science.gov (United States)

    Uziel, Nir; Meyerson, Joseph; Birenzweig, Yonatan; Eli, Ilana

    2018-05-16

    Professional burnout and work-related stress are known problems that have been the subject of in-depth examination among dentists. Nevertheless, these issues have not been widely studied among dental assistants. The aims of this study were threefold: to confirm the structure of a Work Stress Inventory (WSI) for Dental Assistants which was originally developed for Jordanian dental assistants (factor analysis); to evaluate work stress and burnout among Israeli dental assistants and to discover the factors predicting Israeli assistants' burnout (regression analyses). The Maslach Burnout Inventory and the WSI were distributed by mail and in person. Varimax factor analysis revealed that the items which contribute to different aspects of work stress are similar among both Jordanian and Israeli populations. Among the 299 Israeli dental assistants who completed the questionnaires, the most stressful work-related factors were income, workload, and work hazards. Eighteen percent of the participants exhibited a high to very high level of burnout. Participants exhibited a moderate level of emotional exhaustion (EE), low level of depersonalization (DP), and high level of personal accomplishment (PA). Most WSI factors were found to correlate positively with EE and DP. Linear stepwise regression analyses revealed that the best predictor of EE was the dentist‒assistant relationship, followed by workload, patient type, and salary. The best predictor of DP was patient suffering followed by dentist‒assistant relationship, years of professional experience, and work hazards. Professional stress and burnout among dental assistants are important factors that can possibly affect the wellbeing of both dental personnel and their patients. Further studies are necessary to better understand these factors in addition to the effects of personal relationships on burnout among dentists and their assistants.

  18. Canadian dental students' perceptions of stress.

    Science.gov (United States)

    Muirhead, Vanessa; Locker, David

    2007-05-01

    In this paper, we report the results of a survey on dental student stress carried out in April 2005. A questionnaire was used to collect data from 171 students (62% response rate). Identified stressors were academic, clinic-related, social and financial. "Examination and grades" produced the most academic stress, and inconsistent feedback from instructors created the most clinic-related stress. Students found that having a dual role--wife or husband and dental student--was the most burdensome social stressor. Approximately 60% of students reported marital problems and stress associated with "relations with members of the opposite sex." Survey results showed that students who expected a high graduating debt had higher total and academic stress scores. Total stress was not related to age, gender or marital status. Students living with parents during term time had significantly higher total stress scores than students living in other arrangements. Students residing with parents also had significantly higher debts on entry to dental school. Students with more predental education had (non-significantly) lower stress scores but also had higher student debts. Undergraduate subject major (biological science or non-science) had no bearing on reported stress. This study highlights the negative effects of student debt, the necessity for staff training and the need for further studies exploring relations among stress, psychological well-being and academic performance.

  19. Stress analysis of different prosthesis materials in implant-supported fixed dental prosthesis using 3D finite element method

    Directory of Open Access Journals (Sweden)

    Pedram Iranmanesh

    2014-01-01

    Full Text Available Introduction: In the present study, the finite element method (FEM was used to investigate the effects of prosthesis material types on stress distribution of the bone surrounding implants and to evaluate stress distribution in three-unit implant-supported fixed dental prosthesis (FDP. Materials and Methods: A three-dimensional (3D finite element FDP model of the maxillary second premolar to the second molar was designed. Three load conditions were statically applied on the functional cusps in horizontal (57.0 N, vertical (200.0 N, and oblique (400.0 N, θ = 120° directions. Four standard framework materials were evaluated: Polymethyl methacrylate (PMMA, base-metal, porcelain fused to metal, andporcelain. Results: The maximum of von Mises stress in the oblique direction was higher than the vertical and horizontal directions in all conditions. In the bone-crestal section, the maximum von Mises stress (53.78 MPa was observed in PMMA within oblique load. In FDPs, the maximum stress was generated at the connector region in all conditions. Conclusion: A noticeable difference was not observed in the bone stress distribution pattern with different prosthetic materials. Although, higher stress value could be seen in polymethyl methacrylate, all types of prosthesis yielded the same stress distribution pattern in FDP. More clinical studies are needed to evaluate the survival rate of these materials.

  20. Reassessment of the psychometric characteristics and factor structure of the 'Perceived Stress Questionnaire' (PSQ: analysis in a sample of dental students.

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    Jesús Montero-Marin

    Full Text Available The training to become a dentist can create psychological distress. The present study evaluates the structure of the 'Perceived Stress Questionnaire' (PSQ, its internal consistency model and interrelatedness with burnout, anxiety, depression and resilience among dental students.The study employed a cross-sectional design. A sample of Spanish dental students (n = 314 completed the PSQ, the 'Goldberg Anxiety and Depression Scale' (GADS, 'Connor-Davidson Resilience Scale' (10-item CD-RISC and 'Maslach Burnout Inventory-Student Survey' (MBI-SS. The structure was estimated using Parallel Analysis from polychoric correlations. Unweighted Least Squares was the method for factor extraction, using the Item Response Theory to evaluate the discriminative power of items. Internal consistency was assessed by squaring the correlation between the latent true variable and the observed variable. The relationships between the PSQ and the other constructs were analysed using Spearman's coefficient.The results showed a PSQ structure through two sub-factors ('frustration' and 'tenseness' with regard to one general factor ('perceived stress'. Items that did not satisfy discriminative capacity were rejected. The model fit were acceptable (GFI = 0.98; RSMR = 0.06; AGFI = 0.98; NFI = 0.98; RFI = 0.98. All the factors showed adequate internal consistency as measured by the congeneric model (≥0.91. High and significant associations were observed between perceived stress and burnout, anxiety, depression and resilience.The PSQ showed a hierarchical bi-factor structure among Spanish dental students. Using the questionnaire as a uni-dimensional scale may be useful in perceived stress level discrimination, while the sub-factors could help us to refine perceived stress analysis and improve therapeutic processes.

  1. Calculation of contraction stresses in dental composites by analysis of crack propagation in the matrix surrounding a cavity.

    Science.gov (United States)

    Yamamoto, Takatsugu; Ferracane, Jack L; Sakaguchi, Ronald L; Swain, Michael V

    2009-04-01

    Polymerization contraction of dental composite produces a stress field in the bonded surrounding substrate that may be capable of propagating cracks from pre-existing flaws. The objectives of this study were to assess the extent of crack propagation from flaws in the surrounding ceramic substrate caused by composite contraction stresses, and to propose a method to calculate the contraction stress in the ceramic using indentation fracture. Initial cracks were introduced with a Vickers indenter near a cylindrical hole drilled into a glass-ceramic simulating enamel. Lengths of the radial indentation cracks were measured. Three composites having different contraction stresses were cured within the hole using one- or two-step light-activation methods and the crack lengths were measured. The contraction stress in the ceramic was calculated from the crack length and the fracture toughness of the glass-ceramic. Interfacial gaps between the composite and the ceramic were expressed as the ratio of the gap length to the hole perimeter, as well as the maximum gap width. All groups revealed crack propagation and the formation of contraction gaps. The calculated contraction stresses ranged from 4.2 MPa to 7.0 MPa. There was no correlation between the stress values and the contraction gaps. This method for calculating the stresses produced by composites is a relatively simple technique requiring a conventional hardness tester. The method can investigate two clinical phenomena that may occur during the placement of composite restorations, i.e. simulated enamel cracking near the margins and the formation of contraction gaps.

  2. A comparative study on the stress distribution around dental implants in three arch form models for replacing six implants using finite element analysis.

    Science.gov (United States)

    Zarei, Maryam; Jahangirnezhad, Mahmoud; Yousefimanesh, Hojatollah; Robati, Maryam; Robati, Hossein

    2018-01-01

    Dental implant is a method to replacement of missing teeth. It is important for replacing the missed anterior teeth. In vitro method is a safe method for evaluation of stress distribution. Finite element analysis as an in vitro method evaluated stress distribution around replacement of six maxillary anterior teeth implants in three models of maxillary arch. In this in vitro study, using ABAQUS software (Simulia Corporation, Vélizy-Villacoublay, France), implant simulation was performed for reconstruction of six maxillary anterior teeth in three models. Two implants were placed on both sides of the canine tooth region (A model); two implants on both sides of the canine tooth region and another on one side of the central incisor region (B model); and two implants on both sides of the canine tooth region and two implants in the central incisor area (C model). All implants evaluated in three arch forms (tapered, ovoid, and square). Data were analyzed by finite analysis software. Von Mises stress by increasing of implant number was reduced. In a comparison of A model in each maxillary arch, the stress created in the cortical and cancellous bones in the square arch was less than ovoid and tapered arches. The stress created in implants and cortical and cancellous bones in C model was less than A and B models. The C model (four-implant) reduced the stress distribution in cortical and cancellous bones, but this pattern must be evaluated according to arch form and cost benefit of patients.

  3. Perceived sources of stress among Malaysian dental students

    OpenAIRE

    Babar, Muneer G.; Hasan, Syed S.; Ooi, Yong J.; Ahmed, Syed I.; Wong, Pei S.; Ahmad, Siti F.; MNM-Rosdy, Nik M.; Malik, Normaliza A.

    2015-01-01

    Objectives The study objectives were to identify the stress levels and to explore the impact of students' year of study and gender on the perceived sources of stress among Malaysian dental students. Methods This was a cross-sectional study involving dental students from year one to year five from private and public universities in Malaysia. The study was formally approved by the Research and Ethics Committee, International Medical University Malaysia. Dental Environment Stress (DES) questionn...

  4. Dental family stress and coping patterns.

    Science.gov (United States)

    Nevin, R S; Sampson, V M

    1986-10-01

    This exploratory study of 28 married male dentists and their families was designed to gain an understanding about the stressors that dentists and their spouses experience, the life events and family strains they incur, the behavioral coping patterns they utilize, and their psychosocial characteristics. The study found that although stable dental families did encounter a significant number of stressors arising from both the dental practice and the family, they maintained their sense of balance through strong family coping skills and family resources. The effect of the dentist's office-related stress was directly felt in the family, especially by the spouse. Strong coping patterns resulted when dentists and spouses maintained a balance of time and responsibility, satisfaction in work and family activity, regular communication, sharing of decision making, good physical health, and the inclusion of an active exercise program within multiple demands on their time.

  5. CONSIDERATIONS UPON CONTACT STRESS MODELLING IN DENTAL ARTICULATOR PAIRS

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    Carmen Ciornei

    2012-05-01

    Full Text Available A dental articulator is a mechanism which simulates the temporo-mandibular joint. The articulator is essential as it replicates the basic motions of the upper and lower mandibles, both revolve and translational motions. In the present paper the stresses from an articulator TMJ modelled as a bronze sphere into a cylindrical steel cavity are analyzed by two methods, first applying the Hertzian contact theory and then numerically, by means of finite element analysis using the simulation module in CATIA.

  6. Effect of the Periodontal Ligament of the Bilateral Support Teeth on the Stress Analysis of Dental Implant

    Directory of Open Access Journals (Sweden)

    Xie Yanhua

    2017-01-01

    Full Text Available The aim of this work is to analyze the function of natural teeth’s periodontal ligament and the effects of periodontal ligament on implants by the finite element method (FEM, when static functional loads occur. The finite element analysis models are established, which consist of fragment of mandible, natural teeth, periodontal ligament, and implant. Finite element software Abaqus is used to analyze the stress transfer in models with or without periodontal ligament, and mandibular first molar is implant. The implant obtained the maximum stress value of 87.71MPa when periodontal ligament of natural tooth is absent, but the maximum value reduces to 38.43 MPa with the action of periodontal ligament. It illustrates that periodontal ligament has significant effects on stress transfer. When the finite element model of single natural tooth or dentition with implant is generated, periodontal ligament should be taken into account.

  7. LIPID PEROXIDATION AND JOB STRESS IN DENTAL HEALTHCARE WORKERS

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    S. V. Melnikova

    2014-04-01

    Full Text Available This study devoted to the lipid peroxidation indices in dentists target group as a marker of psycho-emotional state. We revealed increase in the level of TBA-active products in female and male dentists during job stress. There was strong decrease in level of TBA-active products in control group of dentist that study during the lectures. Activation of lipid peroxidation in dentists during dentist examination can be considered as non-specific component of reactions towards the stressors of professional activities. We also revealed that the initial level of TBA-active products in female and male dentists before the outpatient dental reception was higher than that of dentists that study before lectures. This is indicates the mobilization of sympathetic nervous system before beginning of the working day. The contents of the level of TBA-active products in the oral fluid of female and male dentists after dental examination significantly increased, whereas these indices decreased in the group of dentists that study after the lectures. The increasing of TBA-active products in dentists after outpatient dental reception was by 42.5 % and 77 % higher compared with a group of dentists that study in the lecture classes. The results of correlation analysis suggest the influence of lipid peroxidation processes on the cardiovascular and blood system of dentists during job stress. Activation of lipid peroxidation in dentists during dental examination can be considered as non-specific component of the body's response to stressors influence in professional activities. Key words: dentists, activation of lipid peroxidation, psychoemotional stress, job stress.

  8. Stress Distribution in Single Dental Implant System: Three-Dimensional Finite Element Analysis Based on an In Vitro Experimental Model.

    Science.gov (United States)

    Rezende, Carlos Eduardo Edwards; Chase-Diaz, Melody; Costa, Max Doria; Albarracin, Max Laurent; Paschoeto, Gabriela; Sousa, Edson Antonio Capello; Rubo, José Henrique; Borges, Ana Flávia Sanches

    2015-10-01

    This study aimed to analyze the stress distribution in single implant system and to evaluate the compatibility of an in vitro model with finite element (FE) model. The in vitro model consisted of Brånemark implant; multiunit set abutment of 5 mm height; metal-ceramic screw-retained crown, and polyurethane simulating the bone. Deformations were recorded in the peri-implant region in the mesial and distal aspects, after an axial 300 N load application at the center of the occlusal aspect of the crown, using strain gauges. This in vitro model was scanned with micro CT to design a three-dimensional FE model and the strains in the peri-implant bone region were registered to check the compatibility between both models. The FE model was used to evaluate stress distribution in different parts of the system. The values obtained from the in vitro model (20-587 με) and the finite element analysis (81-588 με) showed agreement among them. The highest stresses because of axial and oblique load, respectively were 5.83 and 40 MPa for the cortical bone, 55 and 1200 MPa for the implant, and 80 and 470 MPa for the abutment screw. The FE method proved to be effective for evaluating the deformation around single implant. Oblique loads lead to higher stress concentrations.

  9. Perceived sources of stress among Malaysian dental students.

    Science.gov (United States)

    Babar, Muneer G; Hasan, Syed S; Ooi, Yong J; Ahmed, Syed I; Wong, Pei S; Ahmad, Siti F; Mnm-Rosdy, Nik M; Malik, Normaliza A

    2015-05-02

    The study objectives were to identify the stress levels and to explore the impact of students' year of study and gender on the perceived sources of stress among Malaysian dental students. This was a cross-sectional study involving dental students from year one to year five from private and public universities in Malaysia. The study was formally approved by the Research and Ethics Committee, International Medical University Malaysia. Dental Environment Stress (DES) questionnaire was used for data collection and the gathered data were analyzed using SPSS® version 18. The Kruskal-Wallis and the Mann-Whitney U tests were used to compare stress items across various academic years and universities. A total of five hundred and twenty nine (529) students participated in this study. Fear of failing the course at the end of year exams (mean stress level=5.57); concerns regarding completion of clinical work (mean=5.30); and examination results and grades (mean=5.27) were found as top stressors among dental students. Female students had higher stress scores than males with respect to personal issues, academic performance, educational environment and learning of clinical skills. Students from public universities had higher stress scores than their counterparts from private universities. The Malaysian dental students reported higher levels of stress. Present study identified stressors affecting dental students' academic life, and highlights the importance of stress management programs and other measures to minimize the impact of stress on both academic and personal lives of the students.

  10. PERSONALITY TRAITS AND STRESS LEVELS AMONG SENIOR DENTAL STUDENTS: EVIDENCE FROM MALAYSIA AND SINGAPORE.

    Science.gov (United States)

    Yusof, Zamros Y M; Hassan, Wan Nurazreena Wan; Razak, Ishak A; Hashim, Siti Marini N; Tahir, Mohd Khairul A M; Keng, Siong Beng

    2016-11-01

    This study aimed to evaluate the association between dental students’ personality traits and stress levels in relation to dental education programs among senior dental students in University Malaya (UM) in Malaysia and National University of Singapore (NUS). A cross-sectional survey using a self-administered questionnaire was conducted on UM and NUS senior dental students. The questionnaire comprised items on demographic background, the Big Five Inventory Personality Traits (BFIPT) test and a modified Dental Environment Stress (DES) scale. Rasch analysis was used to convert raw data to interval scores. Analyses were done by t-test, Pearson correlation, and Hierarchical regression statistics. The response rate was 100% (UM=132, NUS=76). Personality trait Agreeableness (mean=0.30) was significantly more prevalent among UM than NUS students (mean=0.15, p=0.016). In NUS, Neuroticism (mean=0.36) was significantly more prevalent than in UM (mean=0.14, p=0.002). The DES mean score was higher among NUS (mean=0.23) than UM students (mean=0.07). In UM, Neuroticism was significantly correlated with stress levels (r=0.338, ppersonality traits. The correlation was strongest for personality trait Neuroticism in both schools. Hierarchical regression analysis showed that gender and Neuroticism were significant predictors for students’ stress levels (ppersonality trait were significant predictors for stress levels among selected groups of dental students in Southeast Asia. Information on students’ personality may be useful in new students’ intake, stress management counseling and future program reviews.

  11. Effectiveness of a Dental Students Stress Management Program

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    Abdullah M. Alzahem

    2015-12-01

    Full Text Available The dental education stress effects and sources were explored thoroughly in the literature, but the effectiveness of stress management programs received less attention. This study introduced a new stress management program, named Dental Education Stress Management (DESM program. It showed its effectiveness in a quasi-experimental pretest-posttest-follow-up-control group design. The new program was based on the principle of psychoeducation and consisted of three 90-min sessions, to teach dental students how to better deal with their stress symptoms and to reduce their general stress level. Two instruments were used to assess the level of stress of the dental students, namely the Dental Environment Stress questionnaire (DES, and the Psychological Stress Measure (PSM-9. Results show that the DESM program has the desired effect of decreasing the stress levels of its participants, and these effects lasted for at least two weeks. Because of several methodological limitations of the study more research is needed to draw more generalizable conclusions.

  12. [Quality of life, stress management and health promotion in medical and dental students. A comparative study].

    Science.gov (United States)

    Jurkat, H; Höfer, S; Richter, L; Cramer, M; Vetter, A

    2011-06-01

    Which are the differences in health-related quality of life and stress management in medical and dental students? 101 dental and 237 medical students from different years of Justus-Liebig University Giessen were examined during winter term 2008/09 and summer term 2009 using the specific Questionnaire on Health Promotion, Life Satisfaction, and Stress Management in Dental or Medical Students (addressing work satisfaction and choice of subject, private life, relaxation behavior and stress management, and health behavior), Beck Depression Inventory (BDI) and SF-36 Health Survey. For statistical analysis, Mann-Whitney-U-Test, analysis of variance (ANOVA), Pearson correlation and Chi2-Tests were primarily used. Dental and medical students showed considerable mental impairment in SF-36. Every fifth dental student suffered from slight to moderate depression. Though averaging more hours per week, medical students were more satisfied with their studies. More than half of the dental and medical students did not have appropriate strategies of coping with stress. Concerning the mental impairment in both groups and regarding a higher health-related quality of life, specific prevention courses or mentoring programs should already be offered at the beginning of medical training in order to cope with strains of medical school and future job strains in the medical or dental profession. © Georg Thieme Verlag KG Stuttgart · New York.

  13. Environmental and perceived stress in Australian dental undergraduates: Preliminary outcomes

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    Shannon Astill

    2016-12-01

    Full Text Available Background. Dental students have reported a high prevalence of psychological stress and the causes are associated with the challenging dental environmental and demographic factors. This study aimed to conduct a preliminary investigation on dental students’ stress status, using a sample of first-to-third-year Bachelor of Dental Surgery students in an Australian university. Special interests included causes of dental environmental stress and access to help services. Methods. A sample of 145 students was surveyed with a modified Dental Environmental Survey and Depression Anxiety Stress Scale in 2014. The participants’ demographic information was also collected. Results. The response rate was 95.4%. Second-year (P = 0.042, third-year (P < 0.001 and employed students (P = 0.027 were more likely to report stress resulting from transition to clinical learning. Third-year students were more often stressed about communicating and approaching staff (P = 0.023 as well as different opinions between staff (P < 0.001 and reduced holidays (P < 0.001. Students that were younger than 21 years of age (P = 0.001, that were first years (P < 0.001, and that were not in a relationship (P = 0.010 more often found difficulty of course work stressful. Students who were not in a relationship more often considered learning manual dexterity a source of stress (P = 0.034. Students previously seeking professional help were more likely to be stressed (P = 0.010. Conclusion. Causes of dental environment stress varied among years of study and demographic backgrounds. Professional support to stressed students should be enhanced. Further investigation is indicated.

  14. A Cognitive Task Analysis for Dental Hygiene.

    Science.gov (United States)

    Cameron, Cheryl A.; Beemsterboer, Phyllis L.; Johnson, Lynn A.; Mislevy, Robert J.; Steinberg, Linda S.; Breyer, F. Jay

    2000-01-01

    As part of the development of a scoring algorithm for a simulation-based dental hygiene initial licensure examination, this effort conducted a task analysis of the dental hygiene domain. Broad classes of behaviors that distinguish along the dental hygiene expert-novice continuum were identified and applied to the design of nine paper-based cases…

  15. Stress management in dental students: a systematic review

    Science.gov (United States)

    Alzahem, Abdullah M; Van der Molen, Henk T; Alaujan, Arwa H; De Boer, Benjamin J

    2014-01-01

    This study compared the effectiveness of stress management programs in dental education by systematic review of the literature. The number of studies concerning stress management programs for dental students is limited compared with studies discussing sources of stress. Several types of programs for stress management have been reported, and differ in their duration, content, and outcomes. Two main strategies have been used to help stressed students, ie, decreasing the number of stressors and increasing the ability to cope with stress. The first strategy includes several components, such as reducing fear of failure and workload pressure due to examinations and requirements. The second strategy includes coping techniques, such as deep breathing exercises. Although positive effects have been reported for most of the programs, these have mainly been evaluated using subjective self-report measures. There is a need for more research to identify the most effective stress management program. PMID:24904226

  16. Equivalent Young's modulus of composite resin for simulation of stress during dental restoration.

    Science.gov (United States)

    Park, Jung-Hoon; Choi, Nak-Sam

    2017-02-01

    For shrinkage stress simulation in dental restoration, the elastic properties of composite resins should be acquired beforehand. This study proposes a formula to measure the equivalent Young's modulus of a composite resin through a calculation scheme of the shrinkage stress in dental restoration. Two types of composite resins remarkably different in the polymerization shrinkage strain were used for experimental verification: the methacrylate-type (Clearfil AP-X) and the silorane-type (Filtek P90). The linear shrinkage strains of the composite resins were gained through the bonded disk method. A formula to calculate the equivalent Young's moduli of composite resin was derived on the basis of the restored ring substrate. Equivalent Young's moduli were measured for the two types of composite resins through the formula. Those values were applied as input to a finite element analysis (FEA) for validation of the calculated shrinkage stress. Both of the measured moduli through the formula were appropriate for stress simulation of dental restoration in that the shrinkage stresses calculated by the FEA were in good agreement within 3.5% with the experimental values. The concept of equivalent Young's modulus so measured could be applied for stress simulation of 2D and 3D dental restoration. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  17. Psychological stress in undergraduate dental students: baseline results from seven European dental schools.

    Science.gov (United States)

    Humphris, Gerry; Blinkhorn, Andy; Freeman, Ruth; Gorter, Ronald; Hoad-Reddick, Gillian; Murtomaa, Heikki; O'Sullivan, Robin; Splieth, Christian

    2002-02-01

    To determine the degree of psychological distress, the experience of emotional exhaustion, and the extent of stress associated with course work in dental students and to compare these measurements among seven European dental schools. Multi-centred survey. Dental Schools at Amsterdam, Belfast, Cork, Greifswald, Helsinki, Liverpool and Manchester. 333 undergraduate first-year dental students. General Health Questionnaire (GHQ12), Maslach Burnout Inventory (MBI), Dental Environment Stress Questionnaire (DES), demographic variables. Questionnaire administered to all students attending first year course. Completed questionnaires sent to central office for processing. Seventy-nine percent of the sampled students responded. Over a third of the students (36%) reported significant psychological distress (morbidity) at the recommended cut-off point (>3 on GHQ). These scores were similar to those reported for medical undergraduates. Twenty-two percent recorded comparatively high scores on emotional exhaustion. A wide variation in these 2 measurements was found across schools (p'sStress levels indicated by the DES were less variable (p>0.5). Some evidence showed that contact with patients and the level of support afforded by living at home may be protective. Higher than expected levels of emotional exhaustion were found in a large sample of first-year undergraduate dental students in Europe.

  18. Stress management in dental students: a systematic review

    Directory of Open Access Journals (Sweden)

    Alzahem AM

    2014-05-01

    Full Text Available Abdullah M Alzahem,1 Henk T Van der Molen,2 Arwa H Alaujan,3 Benjamin J De Boer4 1King Abdullah International Medical Research Center, King Saud bin Abdulaziz University for Health Sciences, National Guard Health Affairs, Riyadh, Saudi Arabia; 2Institute of Psychology, Faculty of Social Sciences, Erasmus University, Rotterdam, the Netherlands; 3Dental Services, Central Region, King Abdulaziz Medical City, National Guard Health Affairs, Riyadh, Saudi Arabia; 4Clinical Psychology, Princess Nora University, Riyadh, Saudi Arabia Abstract: This study compared the effectiveness of stress management programs in dental education by systematic review of the literature. The number of studies concerning stress management programs for dental students is limited compared with studies discussing sources of stress. Several types of programs for stress management have been reported, and differ in their duration, content, and outcomes. Two main strategies have been used to help stressed students, ie, decreasing the number of stressors and increasing the ability to cope with stress. The first strategy includes several components, such as reducing fear of failure and workload pressure due to examinations and requirements. The second strategy includes coping techniques, such as deep breathing exercises. Although positive effects have been reported for most of the programs, these have mainly been evaluated using subjective self-report measures. There is a need for more research to identify the most effective stress management program. Keywords: students, dentistry, education, management, stress

  19. Effect of implant number and distribution on load transfer in implant-supported partial fixed dental prostheses for the anterior maxilla: A photoelastic stress analysis study.

    Science.gov (United States)

    Lee, Jae-In; Lee, Yoon; Kim, Yu-Lee; Cho, Hye-Won

    2016-02-01

    The 4-, 3- or even 2-implant-supported partial fixed dental prosthesis (PFDP) designs have been used to rehabilitate the anterior edentulous maxilla. The purpose of this in vitro study was to compare the stress distribution in the supporting tissues surrounding implants placed in the anterior maxilla with 5 PFDP designs. A photoelastic model of the human maxilla with an anterior edentulous region was made with photoelastic resin (PL-2; Vishay Micro-Measurements), and 6 straight implants (OsseoSpeed; Astra Tech AB) were placed in the 6 anterior tooth positions. The 5 design concepts based on implant location were as follows: model 6I: 6 implants; model 2C2CI: 4 implants (2 canines and 2 central incisors); model 2C2LI: 4 implants (2 canines and 2 lateral incisors); model 2C1CI: 3 implants (2 canines and 1 central incisor); and model 2C: 2 canines. A load of 127.4 N was applied on the cingulum of 3 teeth at a 30-degree angle to the long axis of the implant. Stresses that developed in the supporting structure were recorded photographically. The 6-implant-supported PFDP exhibited the most even and lowest distribution of stresses in all loading conditions. When the canine was loaded, the 2- or 3-implant-supported PFDP showed higher stresses around the implant at the canine position than did the 4- or 6-implant-supported PFDP. When the central incisor or lateral incisor was loaded, the two 4-implant-supported PFDPs exhibited similar levels of stresses around the implants and showed lower stresses than did the 2- or 3-implant-supported PFDP. Implant number and distribution influenced stress distribution around the implants in the anterior maxilla. With a decrease in implant number, the stresses around the implants increased. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  20. Anxiety, Stress and Coping Patterns in Children in Dental Settings

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    Nadica Pop-Jordanova

    2018-04-01

    CONCLUSION: This study confirmed that moderate stress level and anxiety are present in both groups of patients (orthodontic and dental. Obtained scores are depending on gender and age. As more used coping patterns in both groups are developing self-reliance and optimism; avoiding problems and engaging in demanding activity. Some strategies for managing this problem are discussed.

  1. Association of burnout with stress, coping strategies and vocational satisfaction in Chilean clinical dental students.

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    Francisco Pérez

    2016-12-01

    Full Text Available Objective: Dental students are particularly affected by stress, which can lead to ‘burnout syndrome’ by association with other psychological factors. The aim of this study was to analyse the effect of perceived stress, coping strategies, and vocational satisfaction on the severity of burnout in Chilean dental students in the clinical years. Method: The study population was comprised of clinical dental students of five Chilean dental schools. The following variables were considered: age, gender, year of study, burnout, coping strategies, perceived stress, and vocational satisfaction. Statistical analysis included descriptive measures, correlation tests, and stepwise multiple regression analysis. Results: The final sample included 244 students. Three (1.23% students did not have burnout in any of its factors and 38 (15.57% had severe levels in all three factors. There was a statistically significant greater ‘emotional exhaustion’ in 4th year students. There was a statistically significant correlation of the three factors of burnout with ‘social withdrawal’ coping strategy, high levels of perceived stress, and low levels of present and future vocational satisfaction. Conclusion: Most students presented moderate and high levels of burnout. This situation is associated with dysfunctional coping strategies, high levels of perceived stress, and low levels of present and future vocational satisfaction.

  2. Stress Analysis

    DEFF Research Database (Denmark)

    Burcharth, Hans F.

    The following types of forces contribute to the stresses in a Dolos in a pack exposed to waves: 1)Gravity forces Compaction forces (mainly due to settlements, gravity and flow forces) 2) Flow forces 3) Impact forces (impacts between moving concrete blocks)......The following types of forces contribute to the stresses in a Dolos in a pack exposed to waves: 1)Gravity forces Compaction forces (mainly due to settlements, gravity and flow forces) 2) Flow forces 3) Impact forces (impacts between moving concrete blocks)...

  3. Assessment of the changes in the stress-related salivary cortisol levels to the various dental procedures in children

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    Sharmila J Patil

    2015-01-01

    Full Text Available Background: Fear and pain are the factors producing stress and there is evidence that dental fear acquired in childhood may persist to influence adult behavior. Dental treatment is often considered as anxiety producing and stressful. Aim: To assess the levels of stress displayed by the healthy children undergoing routine dental procedures like oral examination, restoration, and extraction by analyzing salivary levels of cortisol before, during, and after the procedures. Materials and Methods: Twenty healthy children aged between 4 and 8 years having their first dental visit and requiring at least one restoration and one extraction were selected. In each patient, three procedures were carried out: (i Routine dental examination, (ii restoration, and (iii extraction. Unstimulated salivary samples were collected 10 min before, during the procedure, and 30 min after each procedure at three different visits for comparison of cortisol production in response to anxiety and stress over time. Total 180 samples were collected to determine salivary cortisol levels using UBI-MAGIWEL TM kit and the readings were noted. Statistical Analysis Used: Statistical Package for Social Sciences (SPSS software with paired t-test, two independent sample t-tests, and analysis of variance (ANOVA were used to analyze the findings. Results: A correlation between salivary cortisol and stress in dental procedure was noticed. Cavity preparation is more stressful procedure in children, so alternative methods can be used in anxious children. Stress associated with extraction persists to a postoperative period. No correlation exists in between Corah′s anxiety scale and salivary cortisol.

  4. Perceived Stress among French Dental Students and Their Opinion about Education Curriculum and Pedagogy.

    Science.gov (United States)

    Inquimbert, Camille; Tramini, Paul; Alsina, Ivan; Valcarcel, Jean; Giraudeau, Nicolas

    2017-10-01

    The purpose of this study was to identify the major sources of perceived stress and their relation to a student satisfaction questionnaire about the curriculum and the pedagogy among French dental students. All dental students ( n = 178) from years 4 to 6 at the University of Montpellier (France) participated in this exploratory survey. In spring 2016, a 3-part questionnaire was distributed during clinical sessions: the first part asked about sociodemographic and living conditions, the second part aimed to assess the students' perceived stress (Dental Environmental Stress questionnaire), and the third part was a satisfaction questionnaire exploring the clinical organization and the teaching methodologies (Student Course Experience Questionnaire). A Spearman's correlation test and a principal component analysis were used to assess the relation between the variables of the questionnaire. The response rate was 99.4%. The most stressful items were "the number of tasks to be performed during clinical practice," "the waiting time before opinion from teachers," and "the administrative part and computer problems." Fifty-four percent of the students claimed to be satisfied with their studies, showing a score of seven or higher. There was a negative correlation between the level of student satisfaction and the level of perceived stress. Although most of the students were globally satisfied with their curriculum, this study highlighted dysfunctions in the clinical education with a level of stress correlated with the student's dissatisfaction. Most of all, students found that examinations were too stressful and that the clinical requested task quotas were overestimated.

  5. Anxiety, Stress and Coping Patterns in Children in Dental Settings.

    Science.gov (United States)

    Pop-Jordanova, Nadica; Sarakinova, Olivera; Pop-Stefanova-Trposka, Maja; Zabokova-Bilbilova, Efka; Kostadinovska, Emilija

    2018-04-15

    Fear of the dentist and dental treatment is a common problem. It can cause treatment difficulties for the practitioner, as well as severe consequences for the patient. As is known, the level of stress can be evaluated thought electrodermal activity, cortisol measure in saliva, or indirectly by psychometric tests. The present study examined the psychological influence of dental interventions on the child as well as coping patterns used for stress diminution. We examined two matched groups of patients: a) children with orthodontic problems (anomalies in shape, position and function of dentomaxillofacial structures) (N = 31, mean age 10.3 ± 2.02) years; and b) children with ordinary dental problems (N = 31, mean age 10.3 ± 2.4 years). As psychometric instruments, we used: 45 items Sarason's scale for anxiety, 20 items simple Stress - test adapted for children, as well as A - cope test for evaluation coping patterns. Obtained scores confirmed the presence of moderate anxiety in both groups as well as moderate stress level. For Sarason's test obtained scores for the group with dental problems are 20.63 ± 8.37 (from max 45); and for Stress test 7.63 ± 3.45 (from max 20); for the orthodontic group obtained scores are 18.66 ± 6.85 for Sarason's test, while for the Stress test were 7.76 ± 3.78. One way ANOVA confirmed a significant difference in values of obtained scores related to the age and gender. Calculated Student t - test shows non-significant differences in obtained test results for both groups of examinees. Coping mechanisms evaluated by A - cope test shows that in both groups the most important patterns used for stress relief are: developing self-reliance and optimism; avoiding problems and engaging in demanding activity. This study confirmed that moderate stress level and anxiety are present in both groups of patients (orthodontic and dental). Obtained scores are depending on gender and age. As more used coping patterns in both groups are developing self

  6. Stress distribution in dental prosthesis under an occlusal combined dynamic loading

    International Nuclear Information System (INIS)

    Merdji, A.; Bachir Bouiadjra, B.; Ould Chikh, B.; Mootanah, R.; Aminallah, L.; Serier, B.; Muslih, I.M.

    2012-01-01

    Highlights: ► The mechanical stress reaches the highest in areas of cortical bones. ► The mechanical stress in the cancellous bone reaches greatest in the bottom of the dental implant. ► Implant with low-volume bone might cause increased stress concentration in the cortical bone. -- Abstract: The biomechanical behavior of osseointegrated dental prostheses systems plays an important role in its functional longevity inside the bone. Simulation of these systems requires an accurate modeling of the prosthesis components, the jaw bone, the implant–bone interface, and the response of the system to different types of applied forces. The purpose of this study was to develop a new three-dimensional model of an osseointegrated molar dental prosthesis and to carry out finite element analysis to evaluate stress distributions in the bone and the dental prosthesis compounds under an occlusal combined dynamic load was applied to the top of the occlusale face of the prosthesis crown. The jaw bone model containing cortical bone and cancellous bone was constructed by using computer tomography scan pictures and Computer Aided Design tools. The dental prosthesis compounds were constructed, simulating the commercially available cylindrical implant of 4.8 mm diameter and 10 mm length. Both finite element models were created in Abaqus finite element software. All materials used in the models were considered to be isotropic, homogeneous and linearly elastic. The elastic properties, loads and constraints used in the model were taken from published data. Results of our finite element analyses, indicated that the maximum stresses were located around the mesial neck of the implant, in the marginal bone. Thus, this area should be preserved clinically in order to maintain the bone–implant interface structurally and functionally.

  7. Psychometric Properties of the Croatian Language Version of the Dental Environment Stress Questionnaire on Dental Medicine Students.

    Science.gov (United States)

    Laktić, Martina; Kuftinec, Krešimir; Čelebić, Asja; Kovačić, Ines; Alhajj, Mohamed Nasser; Kiršić, Sanja Peršić

    2017-09-01

    To develop the Croatian version of the 41-item Dental Environment Stress questionnaire (DES) for stress assessment of dental students in both, preclinical and clinical years of study and to test its psychometric properties in Croatian dental student population. The English version of the 41-Item DES questionnaire was first translated into the Croatian language. Subsequently, it was set on the google drive and filled out by a total of 202 students from the School of Dental Medicine, University of Zagreb and 30 additional students from other Faculties. Students also assessed their overall level of stress on the Likert scale (1=no stress, 5=highest level of stress). Internal consistency was tested on 202 dental students; test-retest reliability on 30 dental students who filled out the same questionnaire twice; convergent validity on 202 dental students; and divergent validity on 202 dental students and 30 students from faculties not belonging to the biomedicine group. Internal consistency showed high Cronbach alpha coefficient (0.9) and test-retest reliability showed no significant difference (P>0.05) within the period of 14 days when stress level had not changed (vacation). Convergent validity was confirmed by the significant association between the DES summary scores and the self- perceived level of stress (Spearman's rho=0.881; P <0.001). Divergent validity was confirmed by significantly lower DES summary scores in students not belonging to the Biomedicine group (t=7.5, P<0.001). Excellent psychometric properties of the Croatian version of the DES questionnaire enable its utilization for assessment of stress level in Croatian dental students.

  8. Psychometric Properties of the Croatian Language Version of the Dental Environment Stress Questionnaire on Dental Medicine Students

    Directory of Open Access Journals (Sweden)

    Martina Laktić

    2017-01-01

    Full Text Available Objective: To develop the Croatian version of the 41-item Dental Environment Stress questionnaire (DES for stress assessment of dental students in both, preclinical and clinical years of study and to test its psychometric properties in Croatian dental student population. Materials and Methods: The English version of the 41-Item DES questionnaire was first translated into the Croatian language. Subsequently, it was set on the google drive and filled out by a total of 202 students from the School of Dental Medicine, University of Zagreb and 30 additional students from other Faculties. Students also assessed their overall level of stress on the Likert scale (1=no stress, 5=highest level of stress. Internal consistency was tested on 202 dental students; test-retest reliability on 30 dental students who filled out the same questionnaire twice; convergent validity on 202 dental students; and divergent validity on 202 dental students and 30 students from faculties not belonging to the biomedicine group. Results: Internal consistency showed high Cronbach alpha coefficient (0.9 and test-retest reliability showed no significant difference (P>0.05 within the period of 14 days when stress level had not changed (vacation. Convergent validity was confirmed by the significant association between the DES summary scores and the self- perceived level of stress (Spearman’s rho=0.881; P<0.001. Divergent validity was confirmed by significantly lower DES summary scores in students not belonging to the Biomedicine group (t=7.5, P<0.001. Conclusion: Excellent psychometric properties of the Croatian version of the DES questionnaire enable its utilization for assessment of stress level in Croatian dental students.

  9. Does student debt affect dental students' and dentists' stress levels?

    Science.gov (United States)

    Boyles, J D; Ahmed, B

    2017-10-27

    Introduction Many studies have shown financial worries and debt to induce stress in individuals, this combined with the existing stress of being a dentist raises the question of how student debt affects students' and dentists' stress levels.Objectives Determine whether student debt has had any noticeable effect on student stress levels; investigate whether student debt has any effect on dentists' career choice; investigate whether the increase in tuition fees has influenced the number of applicants to study dentistry at the University of Birmingham.Method Anonymous questionnaires were completed by 70 4th year and 38 5th year BDS and 22 Dental Core Trainees (DCTs). Participants circled the response which best fitted their situation regarding statements on their level of stress and future career path. Ethical approval granted. Application figures to study dentistry obtained from head of admissions.Results Forty-two percent of males and 63% of females strongly agreed with the statement that having no debt would reduce their stress levels. Of those with debt >£40,000, 11% strongly agreed and 42% agreed that their total amount of student debt causes them stress. Whereas, those whose debt is stress. Seventy-seven percent of participants who had parental or family financial support reported this reduced their stress levels. Student debt was found to deter females from undertaking further study more than it deters males (P stressed about their total student loan(s) (P stress (P stress; students reporting a higher level of debt also report more stress and concern about paying off their student debt. Having no student debt would reduce stress levels, although to what extent is undetermined. Applications to study dentistry have fallen since the increase in tuition fees.

  10. Failure analysis of various monolithic posterior aesthetic dental crowns using finite element method

    Science.gov (United States)

    Porojan, Liliana; Topală, Florin

    2017-08-01

    The aim of the study was to assess the effect of material stiffness and load on the biomechanical performance of the monolithic full-coverage posterior aesthetic dental crowns using finite element analysis. Three restorative materials for monolithic dental crowns were selected for the study: zirconia; lithium disilicate glass-ceramic, and resin-based composite. Stresses were calculated in the crowns for all materials and in the teeth structures, under different load values. The experiments show that dental crowns made from all this new aesthetic materials processed by CAD/CAM technologies would be indicated as monolithic dental crowns for posterior areas.

  11. 3D space analysis of dental models

    Science.gov (United States)

    Chuah, Joon H.; Ong, Sim Heng; Kondo, Toshiaki; Foong, Kelvin W. C.; Yong, Than F.

    2001-05-01

    Space analysis is an important procedure by orthodontists to determine the amount of space available and required for teeth alignment during treatment planning. Traditional manual methods of space analysis are tedious and often inaccurate. Computer-based space analysis methods that work on 2D images have been reported. However, as the space problems in the dental arch exist in all three planes of space, a full 3D analysis of the problems is necessary. This paper describes a visualization and measurement system that analyses 3D images of dental plaster models. Algorithms were developed to determine dental arches. The system is able to record the depths of the Curve of Spee, and quantify space liabilities arising from a non-planar Curve of Spee, malalignment and overjet. Furthermore, the difference between total arch space available and the space required to arrange the teeth in ideal occlusion can be accurately computed. The system for 3D space analysis of the dental arch is an accurate, comprehensive, rapid and repeatable method of space analysis to facilitate proper orthodontic diagnosis and treatment planning.

  12. Failure analysis of fractured dental zirconia implants.

    Science.gov (United States)

    Gahlert, M; Burtscher, D; Grunert, I; Kniha, H; Steinhauser, E

    2012-03-01

    The purpose of the present study was the macroscopic and microscopic failure analysis of fractured zirconia dental implants. Thirteen fractured one-piece zirconia implants (Z-Look3) out of 170 inserted implants with an average in situ period of 36.75±5.34 months (range from 20 to 56 months, median 38 months) were prepared for macroscopic and microscopic (scanning electron microscopy [SEM]) failure analysis. These 170 implants were inserted in 79 patients. The patient histories were compared with fracture incidences to identify the reasons for the failure of the implants. Twelve of these fractured implants had a diameter of 3.25 mm and one implant had a diameter of 4 mm. All fractured implants were located in the anterior side of the maxilla and mandibula. The patient with the fracture of the 4 mm diameter implant was adversely affected by strong bruxism. By failure analysis (SEM), it could be demonstrated that in all cases, mechanical overloading caused the fracture of the implants. Inhomogeneities and internal defects of the ceramic material could be excluded, but notches and scratches due to sandblasting of the surface led to local stress concentrations that led to the mentioned mechanical overloading by bending loads. The present study identified a fracture rate of nearly 10% within a follow-up period of 36.75 months after prosthetic loading. Ninety-two per cent of the fractured implants were so-called diameter reduced implants (diameter 3.25 mm). These diameter reduced implants cannot be recommended for further clinical use. Improvement of the ceramic material and modification of the implant geometry has to be carried out to reduce the failure rate of small-sized ceramic implants. Nevertheless, due to the lack of appropriate laboratory testing, only clinical studies will demonstrate clearly whether and how far the failure rate can be reduced. © 2011 John Wiley & Sons A/S.

  13. Dental students' perceived sources of stress: a multi-country study.

    Science.gov (United States)

    Polychronopoulou, Argy; Divaris, Kimon

    2009-05-01

    The aim of this study was to identify dental students' self-reported sources of stress and to explore the role of specific curricular and institutional differences in the variation of perceived stressors among dental students in Greece, Ireland, Slovenia, Sweden, Spain, and Croatia. A thirty-item modified version of the Dental Environment Stress (DES) questionnaire was administered to all undergraduate students enrolled at six European dental schools selected to reflect geographical, curricular, and professional environment diversity: Athens, Greece; Dublin, Ireland; Ljubljana, Slovenia; Malmö, Sweden; Santiago de Compostela, Spain; and Zagreb, Croatia. Participation varied from 93 percent in Athens to 65 percent in Dublin. A total of 1,492 questionnaires were available for analysis. Univariate analysis and multivariate modelling were used for data analysis. Performance pressure, workload, and self-efficacy beliefs constituted the students' main concerns. In the univariate analysis, student responses differed by country: Swedish students provided the lowestst scores in five out of six DES factors, Spanish students were the most concerned about "clinical training" and "performance pressure," whereas Greek students were the most concerned about "patient treatment." Multivariate modelling revealed that problem-based learning (PBL) was inversely associated with perceived stress for "self-efficacy beliefs" OR (95% CI): 0.66 (0.52, 0.84), "workload" OR (95% CI): 0.58 (0.41, 0.80); and "clinical training" OR (95% CI): 0.69 (0.50, 0.95) when compared to traditional curricula. Students' perceived stressors differed greatly among the six institutions and were associated with both individual (gender, study level) and educational/institutional (curriculum type, class size, educational costs) parameters.

  14. Does stress in a dental hygiene and dental therapy undergraduate programme contribute to a sense of well-being in the students?

    Science.gov (United States)

    Harris, M; Wilson, J C; Hughes, S; Radford, D R

    2017-07-07

    Aims To use a qualitative approach to further explore the stress and well-being of dental hygiene and dental therapy students (DHDTS) during their undergraduate training.Subjects and methods Semi-structured individual interviews to explore motivation, goals, and perceived stress, were conducted with eight DHDTS from across all three years of study at the University of Portsmouth Dental Academy (UPDA). Thematic analysis of the data was undertaken using Braun and Clarke's (2006) six phases of thematic analysis.Results Three main themes of 'fulfilment', 'the learning environment', and 'perception of stress' were identified. Within these themes, a further 12 sub-themes were identified. Analysis suggested that a strong sense of passion to become a clinician mitigated most, but not all, of the stressful experiences of the DHDTS undergraduate learning environment.Conclusions DHDTS' perceived sources of stress during their undergraduate programme were strongly linked to a sense of meaningfulness.Listen to the author talk about the key findings in this paper in the associated video abstract. Available in the supplementary information online and on the BDJ Youtube channel via http://go.nature.com/bdjyoutube.

  15. Perceived Stress among French Dental Students and Their Opinion about Education Curriculum and Pedagogy

    Science.gov (United States)

    Inquimbert, Camille; Tramini, Paul; Alsina, Ivan; Valcarcel, Jean; Giraudeau, Nicolas

    2017-01-01

    Objectives: The purpose of this study was to identify the major sources of perceived stress and their relation to a student satisfaction questionnaire about the curriculum and the pedagogy among French dental students. Materials and Methods: All dental students (n = 178) from years 4 to 6 at the University of Montpellier (France) participated in this exploratory survey. In spring 2016, a 3-part questionnaire was distributed during clinical sessions: the first part asked about sociodemographic and living conditions, the second part aimed to assess the students' perceived stress (Dental Environmental Stress questionnaire), and the third part was a satisfaction questionnaire exploring the clinical organization and the teaching methodologies (Student Course Experience Questionnaire). A Spearman's correlation test and a principal component analysis were used to assess the relation between the variables of the questionnaire. Results: The response rate was 99.4%. The most stressful items were “the number of tasks to be performed during clinical practice,” “the waiting time before opinion from teachers,” and “the administrative part and computer problems.” Fifty-four percent of the students claimed to be satisfied with their studies, showing a score of seven or higher. There was a negative correlation between the level of student satisfaction and the level of perceived stress. Conclusion: Although most of the students were globally satisfied with their curriculum, this study highlighted dysfunctions in the clinical education with a level of stress correlated with the student's dissatisfaction. Most of all, students found that examinations were too stressful and that the clinical requested task quotas were overestimated. PMID:29184835

  16. Dental Videographic Analysis using Digital Age Media.

    Science.gov (United States)

    Agarwal, Anirudh; Seth, Karan; Parmar, Siddharaj; Jhawar, Rahul

    2016-01-01

    This study was to evaluate a new method of smile analysis using videographic and photographic softwares (as in this study Photoshop Elements X, Windows Movie Maker 2012) as primary assessment tools and to develop an index for malocclusion and treatment plan that could be used in assessing severity of maloc-clussion. Agarwal A, Seth K, Parmar S, Jhawar R. Dental Videographic Analysis using Digital Age Media. Int J Clin Pediatr Dent 2016;9(4):355-363.

  17. EVALUATION OF PERCEIVED STRESS LEVELS AND ITS SOURCE AMONG DENTAL STUDENTS: A CROSS-SECTIONAL STUDY

    OpenAIRE

    Praveen K; Christofer; Purna Singh; Shivanand

    2016-01-01

    CONTEXT Recent reports show high amount of academic stress among the students and chronic stress is shown to have a negative effect on cognitive functioning and learning of students. AIMS The purpose of study was to determine the prevalence of self-perceived stress among dental students and to observe any possible association between the levels of stress and (a) academic year, (b) motivation to study dental science, (c) medium of study at 10+2 level, (d) mother tongue, (e...

  18. Finite element analysis (FEA) of dental implant fixture for mechanical stability and rapid osseointegration

    Science.gov (United States)

    Tabassum, Shafia; Murtaza, Ahmar; Ali, Hasan; Uddin, Zia Mohy; Zehra, Syedah Sadaf

    2017-10-01

    For rapid osseointegration of dental implant fixtures, various surface treatments including plasma spraying, hydroxyapatite coating, acid-etching, and surface grooving are used. However undesirable effects such as chemical modifications, loss of mechanical properties, prolonged processing times and post production treatment steps are often associated with these techniques. The osseointegration rate of the dental implants can be promoted by increasing the surface area of the dental implant, thus increasing the bone cells - implant material contact and allow bone tissues to grow rapidly. Additive Manufacturing (AM) techniques can be used to fabricate dental implant fixtures with desirable surface area in a single step manufacturing process. AM allows the use of Computer Aided Designing (CAD) for customised rapid prototyping of components with precise control over geometry. In this study, the dental implant fixture that replaces the tooth root was designed on commercially available software COMSOL. Nickel - titanium alloy was selected as build materials for dental implant. The geometry of the dental fixture was varied by changing the interspacing distance (thread pitch) and number of threads to increase the total surface area. Three different microstructures were introduced on the surface of dental implant. The designed models were used to examine the effect of changing geometries on the total surface area. Finite Element Analysis (FEA) was performed to investigate the effect of changing geometries on the mechanical properties of the dental implant fixtures using stress analysis.

  19. Stress: a concept analysis.

    Science.gov (United States)

    Goodnite, Patricia M

    2014-01-01

    To analyze the concept of stress and provide an operational definition of stress. Literature review revealed that stress is a commonly used, but often ambiguous, term. Findings supported a definition of stress entailing an individual's perception of a stimulus as overwhelming, which in turn elicits a measurable response resulting in a transformed state. This analysis adopts a dynamic definition of stress that may serve to encourage communication, promote reflection, and enhance concept understanding. This definition may provide direction for future work, as well as enhance efforts to serve patients affected by stress. © 2013 Wiley Periodicals, Inc.

  20. Stress predictors in two Asian dental schools with an integrated curriculum and traditional curriculum.

    Science.gov (United States)

    Nguyen, T T T; Seki, N; Morio, I

    2018-05-01

    This study explored stress predictors and the role of instructional methods and institutional differences in perceived stress levels amongst students at two Asian dental schools. An anonymous questionnaire was distributed to undergraduate dental students at Tokyo Medical and Dental University (TMDU), Japan and the University of Medicine and Pharmacy (UMP), Hochiminh City, Vietnam in 2016. Data concerning the students' demographic information and grades, and responses to the Perceived Stress Scale (PSS) and Dental Environment Stress questionnaire (DES) were collected. The questionnaires were prepared in English and translated into Japanese and Vietnamese following a forward-backward translation process. Altogether 684 students answered the questionnaire with a response rate of 97% for TMDU and 89% for UMP. The mean DES score of UMP students was significantly higher than TMDU (P stress scores in several areas than UMP preclinical students. Having dentistry as their first choice of educational programme was a significant stress predictor for Japanese students whilst the clinical practicum was a significant stress predictor for Vietnamese students. Previous academic performance was not a significant stress predictor for students at either dental school. Dental students of an integrated, active-learning curriculum reported lower stress levels than students of a traditional, discipline-based curriculum. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  1. Effect of year of study on stress levels in male undergraduate dental students

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    Alzahem AM

    2013-10-01

    Full Text Available Abdullah M Alzahem,1 Henk T van der Molen,2 Benjamin J de Boer31Advanced Education in General Dentistry (AEGD Residency Program, King Abdullah International Medical Research Center/King Saud bin Abdulaziz University for Health Sciences/National Guard Health Affairs, Riyadh, Saudi Arabia; 2Institute of Psychology, Faculty of Social Sciences, Erasmus University, Rotterdam, The Netherlands; 3Clinical Psychology, Princess Nora University, Riyadh, Saudi ArabiaObjective: Stress among dental students can be a significant threat, resulting in physical and/or mental illness, and have a negative effect on students' performance and the professional practice of dentistry. Stress can occur from different sources. The purpose of this study is to test whether the year of study has an effect on the stress levels of dental students.Method: Our study consisted of a cross-sectional survey using a modified version of the Dental Environment Stress (DES questionnaire. The questionnaires were filled out by male undergraduate dental students at King Saud University in Riyadh City during the 2010–2011 academic year (n = 214.Results: The results show the most common sources of stress: examinations and completing clinical requirements. Moreover, in the five-year lecture-based traditional curriculum, the third year students reported the highest level of stress, whereas the first year reported the lowest level of stress.Conclusion: Third year undergraduate dental students reported the highest level of stress. This stress could be reduced by reviewing and modifying the dental curriculum by allowing students to have contact with patients more gradually, starting from the first year, in addition to adding stress prevention and intervention programs in dental curricula.Keywords: dental, education, students, stress, study year

  2. Stress shielding and fatigue limits of poly-ether-ether-ketone dental implants.

    Science.gov (United States)

    Lee, Woo-Taek; Koak, Jai-Young; Lim, Young-Jun; Kim, Seong-Kyun; Kwon, Ho-Beom; Kim, Myung-Joo

    2012-05-01

    The poly-ether-ether-ketone (PEEK) polymer is of great interest as an alternative to titanium in orthopedics because of its biocompatibility and low elastic modulus. This study evaluated the fatigue limits of PEEK and the effects of the low elastic modulus PEEK in relation to existing dental implants. Compressive loading tests were performed with glass fiber-reinforced PEEK (GFR-PEEK), carbon fiber-reinforced PEEK (CFR-PEEK), and titanium rods. Among these tests, GFR-PEEK fatigue tests were performed according to ISO 14801. For the finite element analysis, three-dimensional models of dental implants and bone were constructed. The implants in the test groups were coated with a 0.5-mm thick and 5-mm long PEEK layer on the upper intrabony area. The strain energy densities (SED) were calculated, and the bone resorption was predicted. The fatigue limits of GFR-PEEK were 310 N and were higher than the static compressive strength of GFR-PEEK. The bone around PEEK-coated implants showed higher levels of SED than the bone in direct contact with the implants, and the wider diameter and stiffer implants showed lower levels of SED. The compressive strength of the GFR-PEEK and CFR-PEEK implants ranged within the bite force of the anterior and posterior dentitions, respectively, and the PEEK implants showed adequate fatigue limits for replacing the anterior teeth. Dental implants with PEEK coatings and PEEK implants may reduce stress shielding effects. Dental implant application of PEEK polymer-fatigue limit and stress shielding. Copyright © 2012 Wiley Periodicals, Inc.

  3. Basic stress analysis

    CERN Document Server

    Iremonger, M J

    1982-01-01

    BASIC Stress Analysis aims to help students to become proficient at BASIC programming by actually using it in an important engineering subject. It also enables the student to use computing as a means of learning stress analysis because writing a program is analogous to teaching-it is necessary to understand the subject matter. The book begins by introducing the BASIC approach and the concept of stress analysis at first- and second-year undergraduate level. Subsequent chapters contain a summary of relevant theory, worked examples containing computer programs, and a set of problems. Topics c

  4. The stress of clinical dental training: A cross-sectional survey among dental students and dentists of a dental college in India

    Directory of Open Access Journals (Sweden)

    Meena Jain

    2016-01-01

    Full Text Available Introduction: Psychological disturbances in clinical dental students and teachers remain largely unknown. Aim: To describe the psychological health of clinical dental students and their trainers in an institution in India. Materials and Methods: A cross-sectional, questionnaire-based study was conducted among clinical dental students and faculty of an Indian dental college in November 2014. The questionnaire consisted of depression anxiety stress scales-21 (DASS 21, a short version of the original 42-item DASS. Data were compiled on SPSS version 21. Group comparisons were done and P values were obtained. All tests were two-tailed with significance set at P< 0.05. Results: Stress scores were found to be higher in students as compared to trainers (P = 0.040, with the highest scores for undergraduate students. Statistically, significant difference was seen in stress scores between graduate and postgraduate trainers (P = 0.015, undergraduates and postgraduate trainers (P = 0.005, and postgraduate trainers and students (P = 0.029. A significant difference was also observed between depression scores in graduate and postgraduate trainers (P = 0.006 as well as postgraduate trainers and students (P = 0.041. Females had significantly higher level of stress (P = 0.007 and anxiety (P = 0.003 scores as compared to males. Conclusion: Stress, anxiety, and depression scores in dental students are higher than trainers. Undergraduate students among all showed the highest scores for all three parameters. Different approaches to reduce them should be further investigated and utilized at the earliest.

  5. Stress Response Pathways in Ameloblasts: Implications for Amelogenesis and Dental Fluorosis

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    John D. Bartlett

    2012-08-01

    Full Text Available Human enamel development of the permanent teeth takes place during childhood and stresses encountered during this period can have lasting effects on the appearance and structural integrity of the enamel. One of the most common examples of this is the development of dental fluorosis after childhood exposure to excess fluoride, an elemental agent used to increase enamel hardness and prevent dental caries. Currently the molecular mechanism responsible for dental fluorosis remains unknown; however, recent work suggests dental fluorosis may be the result of activated stress response pathways in ameloblasts during the development of permanent teeth. Using fluorosis as an example, the role of stress response pathways during enamel maturation is discussed.

  6. SWOT Analysis of Dental Health Workforce in India: A Dental alarm.

    Science.gov (United States)

    Halappa, Mythri; B H, Naveen; Kumar, Santhosh; H, Sreenivasa

    2014-11-01

    India faces an acute shortage of health personnel. Together with inequalities in distribution of health workers, dental health workers also become a part contributing to it impeding the progress towards achievement of the Millennium Development Goals. To assess dental health-workforce distribution, identify inequalities in dental health-workers provision and report the impact of this mal distribution in India. Situational analysis done by using the primary data from the records of Dental Council of India. In India, 0.088% of dental health worker per 1000 population exists. Inequalities in the distribution of dentists exist in India. Certain states are experiencing an acute shortage of dental health personnel whereas certain cities are over fledged with dentists like Karnataka, Maharastra, Tamilnadu being states with high concentration & Jharkhand, Rajasthan, Uttaranchal being the least. Although the production of health workers has expanded greatly in recent years by increase in number of dental colleges the problems of imbalances in their distribution persist. In the race of increasing dentist population ratio in total, inequitable distribution of appropriately trained, motivated and supported dentists gives a mere feel of saturation in jobs making youngsters to not to choose dentistry as a career giving an alarm.

  7. Psychosocial impact, perceived stress and learning effect in undergraduate dental students during transition from pre-clinical to clinical education.

    Science.gov (United States)

    Frese, C; Wolff, D; Saure, D; Staehle, H J; Schulte, A

    2018-04-10

    This study aimed to develop a suitable instrument for a comprehensive quantitative and qualitative assessment of perceived psychosocial impact, levels of stress and learning effect in undergraduate dental students during the transition from pre-clinical to clinical education. These findings might improve curricular structures and didactic organisation during this period. At the beginning of their first clinical year, undergraduate dental students were asked to complete an anonymous forty-item questionnaire. Two hundred and seventy-six undergraduate dental students were willing to participate and completed the questionnaire and participated during the years 2011-2016. The response rate was between 45% and 96%. Correlational analysis (Spearman-Rho) in the field of psychosocial impact showed the dental teacher to be the most important multiplier of students' feelings. If the students feel that their teacher acts cooperatively, positive items increase and negative items decrease significantly (P < .0001). Also, students who report high levels of stress are affected significantly in their psychosocial interaction (P < .0001). Wilcoxon test yielded highest levels of stress in endodontology during the first weeks (P < .0001). During the same period, the greatest learning increment was seen for diagnostics and caries excavation. In conclusion, teaching of undergraduate dental students during the transition period from pre-clinical to clinical education can be positively influenced by a supportive learning environment and by specific chronological modifications in the curriculum. Students should start their clinical training with diagnostics, preventive dentistry and initial periodontal treatment. Due to high levels of perceived stress, endodontology should be introduced later in the clinical curriculum. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  8. Effect of elasticity on stress distribution in CAD/CAM dental crowns: Glass ceramic vs. polymer-matrix composite.

    Science.gov (United States)

    Duan, Yuanyuan; Griggs, Jason A

    2015-06-01

    Further investigations are required to evaluate the mechanical behaviour of newly developed polymer-matrix composite (PMC) blocks for computer-aided design/computer-aided manufacturing (CAD/CAM) applications. The purpose of this study was to investigate the effect of elasticity on the stress distribution in dental crowns made of glass-ceramic and PMC materials using finite element (FE) analysis. Elastic constants of two materials were determined by ultrasonic pulse velocity using an acoustic thickness gauge. Three-dimensional solid models of a full-coverage dental crown on a first mandibular molar were generated based on X-ray micro-CT scanning images. A variety of load case-material property combinations were simulated and conducted using FE analysis. The first principal stress distribution in the crown and luting agent was plotted and analyzed. The glass-ceramic crown had stress concentrations on the occlusal surface surrounding the area of loading and the cemented surface underneath the area of loading, while the PMC crown had only stress concentration on the occlusal surface. The PMC crown had lower maximum stress than the glass-ceramic crown in all load cases, but this difference was not substantial when the loading had a lateral component. Eccentric loading did not substantially increase the maximum stress in the prosthesis. Both materials are resistant to fracture with physiological occlusal load. The PMC crown had lower maximum stress than the glass-ceramic crown, but the effect of a lateral loading component was more pronounced for a PMC crown than for a glass-ceramic crown. Knowledge of the stress distribution in dental crowns with low modulus of elasticity will aid clinicians in planning treatments that include such restorations. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Relationship between psychological well-being and perceptions of stress among undergraduate dental students in Bengaluru city: A cross-sectional study

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    M Anushri

    2014-01-01

    Full Text Available Introduction: The dental profession has been considered a stressful occupation. The origins of this stress may also lie in the process of dental education. The perception of stress is frequently influenced by one′s personal system of beliefs and attitudes. Aim: The aim was to assess the relationship between psychological well-being and perception of stress among undergraduate dental students in Bangalore city. Materials and Methods: A cross-sectional questionnaire survey was conducted among 800 1-4 th year dental students. Information on demographics, social background, and health behaviors were collected. The psychological general well-being (PGWB index and the dental environment stress (DES questionnaire were used to measure PGWB and perceptions of stress, respectively. Multiple intergroup comparisons were carried out using ANOVA. Correlation analysis was done to find out relationship between PGWB and DES. Regression analysis to find out the strongest predictor of PGWB. P <0.05 was considered as statistically significant. Results: There was no significant difference in PGWB among different year of study. Female students had significantly lower PGWB scores and higher DES scores than male students. The stress differed among different year of study with highest stress in final year students in all domains except for clinical/preclinical training, which was highest among 1 st year students. Correlational analysis showed a negative relationship between PGWB and DES score. Stepwise multiple regression analysis revealed that "workload," "patient treatment," "performance pressure" and "others" domains of stress were significant predictors of PGWB. Conclusion: This study revealed that the perception of stress is influenced by gender and health behaviors which in turn affect PGWB.

  10. Stress Analysis of Composites.

    Science.gov (United States)

    1981-01-01

    8217, Finite Elements in Nonlinear Mechanics, 1., 109-130, Tapir Publishers, Norway (1978). 9. A.J. Barnard and P.W. Sharman, ’Elastic-Plastic Analysis Using...Hybrid Stress Finite Elements,’ Finite Elements in Nonlinear Mechanics, 1, 131-148, Tapir Publishers Norway, (1978). ’.........Pian, ’Variational

  11. Research in dental practice: a 'SWOT' analysis.

    Science.gov (United States)

    Burke, F J T; Crisp, R J; McCord, J F

    2002-03-01

    Most dental treatment, in most countries, is carried out in general dental practice. There is therefore a potential wealth of research material, although clinical evaluations have generally been carried out on hospital-based patients. Many types of research, such as clinical evaluations and assessments of new materials, may be appropriate to dental practice. Principal problems are that dental practices are established to treat patients efficiently and to provide an income for the staff of the practice. Time spent on research therefore cannot be used for patient treatment, so there are cost implications. Critics of practice-based research have commented on the lack of calibration of operative diagnoses and other variables; however, this variability is the stuff of dental practice, the real-world situation. Many of the difficulties in carrying out research in dental practice may be overcome. For the enlightened, it may be possible to turn observations based on the volume of treatment carried out in practice into robust, clinically related and relevant research projects based in the real world of dental practice.

  12. The effect of yoga in stress reduction for dental students performing their first periodontal surgery: A randomized controlled study

    Science.gov (United States)

    Shankarapillai, Rajesh; Nair, Manju Anathakrishnan; George, Roy

    2012-01-01

    Context: The dental students experience a lot of stress, which increase when they perform their first surgical procedure. Yoga as an anxiolytic tool in anxiety reduction has been practiced over centuries in India. Aim: To assess the efficacy of yoga in reducing the state trait anxiety of dental students before their first periodontal surgery performance. Settings and Design: A randomized controlled study using a two-way split plot design (pre-post-test) was conducted in the department of periodontics, Pacific Dental College, Udaipur, India. Materials and Methods: One hundred clinical dental students who were ready to perform their first periodontal surgery were selected. Students were randomly assigned to two groups and were given a 60-min session on stress reduction. Group A, yogic intervention group, were instructed to do yoga and their performances were monitored for a period of one week and Group B, control group, were given a lecture on stress reduction without any yoga instructions. The investigator who was unaware of the groups had taken the state trait anxiety score of the students three times a) before assigning them to each group, b) prior to the surgical procedure and c) immediately after the performance of surgery. Statistical Analysis Used: Analyses of variance (ANOVA) by SPSS V.16. Results: The statistical results showed a significant reduction in the VAS and state trait anxiety of Group A compared to Group B (ANOVA; P<0.001). Conclusions: This study concludes that Yogic breathing has a significant effect on the reduction of state trait anxiety level of dental students. PMID:22346066

  13. Angel or Devil? Dentists and Dental Students Conceptions of Pediatric Dental Patients through Metaphor Analysis.

    Science.gov (United States)

    Buldur, B

    The aim of this qualitative study was to identify the conceptions of dentists and dental students (DSs) about pediatric dental patients (PDPs) using metaphor analysis. The study group (N = 259) consisted of dentists and DSs. Participants completed the sentence "A pediatric dental patient is like ... because …..." in order to reveal the metaphors they use about the concept of PDPs. The data were analyzed using the mixed-methods: qualitative (metaphor analysis) and quantitative (chi-square) data analysis techniques. The dentists and DSs produced 259 metaphors. These metaphors were gathered under six different conceptual categories that define a PDP as unpredictable, dangerous, uncontrollable, requiring care and sensitivity, valuable, and orientable. The most important factors leading to these conceptions were the uncooperativeness of some PDPs and the effectiveness of behavior management. The results of this study indicate that there was no significant difference among DSs, general dentists and specialist dentists with respect to six conceptual categories that identify the conceptions about PDPs.

  14. Ancient DNA analysis of dental calculus.

    Science.gov (United States)

    Weyrich, Laura S; Dobney, Keith; Cooper, Alan

    2015-02-01

    Dental calculus (calcified tartar or plaque) is today widespread on modern human teeth around the world. A combination of soft starchy foods, changing acidity of the oral environment, genetic pre-disposition, and the absence of dental hygiene all lead to the build-up of microorganisms and food debris on the tooth crown, which eventually calcifies through a complex process of mineralisation. Millions of oral microbes are trapped and preserved within this mineralised matrix, including pathogens associated with the oral cavity and airways, masticated food debris, and other types of extraneous particles that enter the mouth. As a result, archaeologists and anthropologists are increasingly using ancient human dental calculus to explore broad aspects of past human diet and health. Most recently, high-throughput DNA sequencing of ancient dental calculus has provided valuable insights into the evolution of the oral microbiome and shed new light on the impacts of some of the major biocultural transitions on human health throughout history and prehistory. Here, we provide a brief historical overview of archaeological dental calculus research, and discuss the current approaches to ancient DNA sampling and sequencing. Novel applications of ancient DNA from dental calculus are discussed, highlighting the considerable scope of this new research field for evolutionary biology and modern medicine. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Comparing Dental Stress in New Child Patients and Returning Patients Using Salivary Cortisol, Immunoglobulin-A and Alpha- Amylase.

    Science.gov (United States)

    Alaki, Sumer M; Safi, Ayman; Ouda, Soliman; Nadhreen, Alaa

    this study was aimed at comparing dental stress in children having their first dental visit to those returning for dental treatment using salivary biomarkers of stress including salivary cortisol (s-cortisol), Immunoglobulin-A (s-IgA) and alpha-amylase (s-α-amylase). Additionally, the study was aimed at monitoring the change in stress in new patients as they progressed from the waiting to the clinical areas. salivary samples were collected from 40 children who had not been to a dentist before and similar samples were collected from 40 children who were returning for completion of dental treatment. Salivary cortisol, s-IgA and s-α-amylase concentrations were obtained by Enzyme-linked Immunosorbent Assay (ELISA). salivary cortisol levels were higher for new patients at the waiting area compared to that at the dental chair (p=0.05). Salivary alpha-amylase significantly increased in new patients while being seated in the dental chair. Returning patients had higher s-α-amylase (p=0.001) and s-IgA (p=0.016) compared to new patients. Returning patients had the lowest level of s-cortisol when providers were faculty pediatric dentists than with students and interns (p=0.035). children coming in for their first dental visit may experience dental stress at the waiting area before being seated for dental examination. Returning children may experience higher levels of stress compared to new child patients possibly due to previous dental exposure.

  16. Cytocompatibility, cytotoxicity and genotoxicity analysis of dental implants

    Science.gov (United States)

    Reigosa, M.; Labarta, V.; Molinari, G.; Bernales, D.

    2007-11-01

    Several types of materials are frequently used for dental prostheses in dental medicine. Different treatments with titanium are the most used. The aim of the present study was to analyze by means of cytotoxicity and cytocompatibility techniques the capacity of dental implants to integrate to the bone tissue. Cultures of UMR 106 cell line derived from an osteosarcoma were used for bioassays mainly because they show many of the properties of osteoblasts. Dental implant samples provided by B&W company were compared with others of recognized trademarks. The first ones contain ASTM titanium (8348 GR2) with acid printing. Cytotoxicity was analyzed by means of lysosome activity, using the neutral red technique and alkaline phosphatase enzyme activity. Cell variability was determined by means of the acridine ethidium-orange bromide technique. One-way ANOVA and Bonferroni and Duncan post-ANOVA tests were used for the statistical analysis. The assays did not show significant differences among the dental implants analyzed. Our findings show that the dental prostheses studied present high biocompatibility, quantified by the bioassays performed. The techniques employed revealed that they can be a useful tool for the analysis of other materials for dental medicine use.

  17. Cytocompatibility, cytotoxicity and genotoxicity analysis of dental implants

    International Nuclear Information System (INIS)

    M, Reigosa; V, Labarta; G, Molinari; D, Bernales

    2007-01-01

    Several types of materials are frequently used for dental prostheses in dental medicine. Different treatments with titanium are the most used. The aim of the present study was to analyze by means of cytotoxicity and cytocompatibility techniques the capacity of dental implants to integrate to the bone tissue. Cultures of UMR 106 cell line derived from an osteosarcoma were used for bioassays mainly because they show many of the properties of osteoblasts. Dental implant samples provided by B and W company were compared with others of recognized trademarks. The first ones contain ASTM titanium (8348 GR2) with acid printing. Cytotoxicity was analyzed by means of lysosome activity, using the neutral red technique and alkaline phosphatase enzyme activity. Cell variability was determined by means of the acridine ethidium-orange bromide technique. One-way ANOVA and Bonferroni and Duncan post-ANOVA tests were used for the statistical analysis. The assays did not show significant differences among the dental implants analyzed. Our findings show that the dental prostheses studied present high biocompatibility, quantified by the bioassays performed. The techniques employed revealed that they can be a useful tool for the analysis of other materials for dental medicine use

  18. Influence of different restorative materials on the stress distribution in dental implants.

    Science.gov (United States)

    Datte, Carlos-Eduardo; Tribst, João-Paulo-Mendes; Dal Piva, Amanda-Maria-de Oliveira; Nishioka, Renato-Sussumu; Bottino, Marco-Antonio; Evangelhista, Alexandre-Duarte M; Monteiro, Fabrício M de M; Borges, Alexandre-Luiz-Souto

    2018-05-01

    To assist clinicians in deciding the most suitable restorative materials to be used in the crowns and abutment in implant rehabilitation. For finite element analysis (FEA), a regular morse taper implant was created using a computer aided design software. The implant was inserted at the bone model with 3 mm of exposed threads. An anatomic prosthesis representing a first maxillary molar was modeled and cemented on the solid abutment. Considering the crown material (zirconia, chromium-cobalt, lithium disilicate and hybrid ceramic) and abutment (Titanium and zirconia), the geometries were multiplied, totaling eight groups. In order to perform the static analysis, the contacts were considered bonded and each material was assigned as isotropic. An axial load (200 N) was applied on the crown and fixation occurred on the base of the bone. Results using Von-Mises criteria and micro strain values were obtained. A sample identical to the CAD model was made for the Strain Gauge (SG) analysis; four SGs were bonded around the implant to obtain micro strain results in bone tissue. FEA results were 3.83% lower than SG. According to the crown material, it is possible to note that the increase of elastic modulus reduces the stress concentration in all system without difference for bone. Crown materials with high elastic modulus are able to decrease the stress values in the abutments while concentrates the stress in its structure. Zirconia abutments tend to concentrate more stress throughout the prosthetic system and may be more susceptible to mechanical problems than titanium. Key words: Finite element analysis, dental implants, ceramic.

  19. Longitudinal behavioral analysis during dental care of children aged 0 to 3 years

    Directory of Open Access Journals (Sweden)

    Robson Frederico Cunha

    2009-09-01

    Full Text Available "When" and "how" the dentist intervenes have repercussions on children's physical and emotional patterns. The objective of the present study was to conduct a longitudinal behavioral analysis during dental care of babies aged 0 to 3 years. A total of 216 patients seen at the Baby Clinic of the School of Dentistry at Araçatuba, São Paulo State University (UNESP, were selected. The selection criterion was attendance at ten dental care sessions at bimonthly intervals for routine procedures such as clinical examination and oral hygiene. There was a predominance of cooperative behavior compared to uncooperative behavior when each visit was analyzed separately. The behavior of the patients must have been directly influenced by their psychomotor development. Constant attendance and exposure of the baby to non-stressful dental stimuli are factors that favor a cooperative behavior.

  20. Correlation between radiographic analysis of alveolar bone density around dental implant and resonance frequency of dental implant

    Science.gov (United States)

    Prawoko, S. S.; Nelwan, L. C.; Odang, R. W.; Kusdhany, L. S.

    2017-08-01

    The histomorphometric test is the gold standard for dental implant stability quantification; however, it is invasive, and therefore, it is inapplicable to clinical patients. Consequently, accurate and objective alternative methods are required. Resonance frequency analysis (RFA) and digital radiographic analysis are noninvasive methods with excellent objectivity and reproducibility. To analyze the correlation between the radiographic analysis of alveolar bone density around a dental implant and the resonance frequency of the dental implant. Digital radiographic images for 35 samples were obtained, and the resonance frequency of the dental implant was acquired using Osstell ISQ immediately after dental implant placement and on third-month follow-up. The alveolar bone density around the dental implant was subsequently analyzed using SIDEXIS-XG software. No significant correlation was reported between the alveolar bone density around the dental implant and the resonance frequency of the dental implant (r = -0.102 at baseline, r = 0.146 at follow-up, p > 0.05). However, the alveolar bone density and resonance frequency showed a significant difference throughout the healing period (p = 0.005 and p = 0.000, respectively). Conclusion: Digital dental radiographs and Osstell ISQ showed excellent objectivity and reproducibility in quantifying dental implant stability. Nonetheless, no significant correlation was observed between the results obtained using these two methods.

  1. Davallialactone reduces inflammation and repairs dentinogenesis on glucose oxidase-induced stress in dental pulp cells.

    Science.gov (United States)

    Lee, Young-Hee; Kim, Go-Eun; Song, Yong-Beom; Paudel, Usha; Lee, Nan-Hee; Yun, Bong-Sik; Yu, Mi-Kyung; Yi, Ho-Keun

    2013-11-01

    The chronic nature of diabetes mellitus (DM) raises the risk of oral complication diseases. In general, DM causes oxidative stress to organs. This study aimed to evaluate the cellular change of dental pulp cells against glucose oxidative stress by glucose oxidase with a high glucose state. The purpose of this study was to test the antioxidant character of davallialactone and to reduce the pathogenesis of dental pulp cells against glucose oxidative stress. The glucose oxidase with a high glucose concentration was tested for hydroxy peroxide (H2O2) production, cellular toxicity, reactive oxygen species (ROS) formation, induction of inflammatory molecules and disturbance of dentin mineralization in human dental pulp cells. The anti-oxidant effect of Davallilactone was investigated to restore dental pulp cells' vitality and dentin mineralization via reduction of H2O2 production, cellular toxicity, ROS formation and inflammatory molecules. The treatment of glucose oxidase with a high glucose concentration increased H2O2 production, cellular toxicity, and inflammatory molecules and disturbed dentin mineralization by reducing pulp cell activity. However, davallialactone reduced H2O2 production, cellular toxicity, ROS formation, inflammatory molecules, and dentin mineralization disturbances even with a long-term glucose oxidative stress state. The results of this study imply that the development of oral complications is related to the irreversible damage of dental pulp cells by DM-induced oxidative stress. Davallialactone, a natural antioxidant, may be useful to treat complicated oral disease, representing an improvement for pulp vital therapy. Copyright © 2013 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  2. Three-dimensional optimization and sensitivity analysis of dental implant thread parameters using finite element analysis.

    Science.gov (United States)

    Geramizadeh, Maryam; Katoozian, Hamidreza; Amid, Reza; Kadkhodazadeh, Mahdi

    2018-04-01

    This study aimed to optimize the thread depth and pitch of a recently designed dental implant to provide uniform stress distribution by means of a response surface optimization method available in finite element (FE) software. The sensitivity of simulation to different mechanical parameters was also evaluated. A three-dimensional model of a tapered dental implant with micro-threads in the upper area and V-shaped threads in the rest of the body was modeled and analyzed using finite element analysis (FEA). An axial load of 100 N was applied to the top of the implants. The model was optimized for thread depth and pitch to determine the optimal stress distribution. In this analysis, micro-threads had 0.25 to 0.3 mm depth and 0.27 to 0.33 mm pitch, and V-shaped threads had 0.405 to 0.495 mm depth and 0.66 to 0.8 mm pitch. The optimized depth and pitch were 0.307 and 0.286 mm for micro-threads and 0.405 and 0.808 mm for V-shaped threads, respectively. In this design, the most effective parameters on stress distribution were the depth and pitch of the micro-threads based on sensitivity analysis results. Based on the results of this study, the optimal implant design has micro-threads with 0.307 and 0.286 mm depth and pitch, respectively, in the upper area and V-shaped threads with 0.405 and 0.808 mm depth and pitch in the rest of the body. These results indicate that micro-thread parameters have a greater effect on stress and strain values.

  3. Meta-Analysis: Application to Clinical Dentistry and Dental Education.

    Science.gov (United States)

    Cohen, Peter A.

    1992-01-01

    Meta-analysis is proposed as an effective alternative to conventional narrative review for extracting trends from research findings. This type of analysis is explained, advantages over more traditional review techniques are discussed, basic procedures and limitations are outlined, and potential applications in dental education and clinical…

  4. Levels of Stress among General Practitioners, Students and Specialists In Pediatric Dentistry during Dental Treatment.

    Science.gov (United States)

    Davidovich, E; Pessov, Y; Baniel, A; Ram, D

    2015-01-01

    To assess self-reported stress during the performance of different procedures in pediatric dentistry, according to the professional experience of the dentists. During the years 2010 to 2011, an anonymous survey was administered by means of an internet link, and by distribution at professional meetings of dentists . No statistically significant differences in stress were reported for maxilla and mandibular procedures. Placement of a rubber dam was rated as the most stressful procedure among dental students. For general practitioners and specialists, injection of local anesthesia to an anxious child was the most stressful procedure, regardless of age, sex, or years of professional experience. A negative correlation was found between years of experience and level of stress for all the procedures surveyed, but not for the use of nitrous oxide. No differences were found between male and female dentists in stress scores for any of the procedures. Higher rates of stress during operative procedures were reported among dental students than among experienced dentists. Anxiety of the pediatric patients, but not the location of the procedure: maxillary or mandibular, affected the dentists' reported level of stress.

  5. Stress, burnout and health in the clinical period of dental education.

    Science.gov (United States)

    Pöhlmann, K; Jonas, I; Ruf, S; Harzer, W

    2005-05-01

    The study examined the extent of stress, burnout and health problems experienced by fourth and fifth year dental students from the three universities of Dresden, Freiburg and Bern. The objectives of the study were to: (i) identify frequent sources of stress and to report the prevalence rates of burnout and health problems in dental students, (ii) determine the rate of students suffering from severe burnout symptoms and (iii) identify stress factors related to the burnout symptoms of emotional exhaustion and depersonalization. A total of 161 dental students from Dresden, Freiburg and Bern participated in the study. They completed the Psychosocial Stress Inventory, the Maslach Burnout Inventory and the Health Survey Questionnaire. Frequent sources of stress were limitation of leisure time, examination anxiety and the transition stress that was related to the adaptation to the demands of the clinical phase of dental education. Few differences existed between the students of the fourth and the fifth study year. Study-related stress was lowest in Bern and considerably higher in Dresden. Differences of mean levels of burnout symptoms were found only for the burnout dimension of emotional exhaustion. Students from Dresden and Freiburg were more emotionally exhausted than students from Bern, students from Dresden also reported more health problems than students from Bern or Freiburg. Ten per cent of the dental students suffered from severe emotional exhaustion, 17% complained about a severe lack of accomplishment and 28% reported severe depersonalization symptoms. Forty-four per cent of the variance of emotional exhaustion was explained by study-related factors such as lack of leisure time, examination anxiety and transition stress. The only predictor of depersonalization was a lack of social integration, accounting for 3% of the variance. A lack of social integration may be an indicator of low social competence which may cause difficulties in dealing with patients

  6. Theory analysis of the Dental Hygiene Human Needs Conceptual Model.

    Science.gov (United States)

    MacDonald, L; Bowen, D M

    2017-11-01

    Theories provide a structural knowing about concept relationships, practice intricacies, and intuitions and thus shape the distinct body of the profession. Capturing ways of knowing and being is essential to any professions' practice, education and research. This process defines the phenomenon of the profession - its existence or experience. Theory evaluation is a systematic criterion-based assessment of a specific theory. This study presents a theory analysis of the Dental Hygiene Human Needs Conceptual Model (DH HNCM). Using the Walker and Avant Theory Analysis, a seven-step process, the DH HNCM, was analysed and evaluated for its meaningfulness and contribution to dental hygiene. The steps include the following: (i) investigate the origins; (ii) examine relationships of the theory's concepts; (iii) assess the logic of the theory's structure; (iv) consider the usefulness to practice; (v) judge the generalizability; (vi) evaluate the parsimony; and (vii) appraise the testability of the theory. Human needs theory in nursing and Maslow's Hierarchy of Need Theory prompted this theory's development. The DH HNCM depicts four concepts based on the paradigm concepts of the profession: client, health/oral health, environment and dental hygiene actions, and includes validated eleven human needs that evolved overtime to eight. It is logical, simplistic, allows scientific predictions and testing, and provides a unique lens for the dental hygiene practitioner. With this model, dental hygienists have entered practice, knowing they enable clients to meet their human needs. For the DH HNCM, theory analysis affirmed that the model is reasonable and insightful and adds to the dental hygiene professions' epistemology and ontology. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  7. Fast XRF analysis of mineral elements in dental composites

    International Nuclear Information System (INIS)

    Preoteasa, E. A.; Constantinescu, B.; Preoteasa, E.

    2001-01-01

    Dental composites, made of particles of glass, ceramics or quartz embedded in an organic polymer matrix, extensively replaced silver amalgam in tooth fillings and enabled new applications for restorative dentistry. Long-term alteration of dental fillings together with market pressure motivates the development of composites at a high rate, largely by progress of materials forming their mineral phase. Therefore, dental composites constantly bring at the interface with enamel and dentine new elements foreign to the organism, whose biological action has not been studied. Atomic and nuclear methods for surface multielemental analysis have been used in dental research but not for composites. X-ray fluorescence (XRF) is suited for the fast microanalytical screening of the elements and of their changes at the biomaterial's surface. The potential of radioisotope-excited XRF for the analysis of dental composites has been examined. Flat disk-shaped samples of composites have been prepared and polymerized chemically or by irradiation with intense 420-500 nm light. The measurements were performed with a spectrometric chain containing a 30 mCi source of 241 Am, a Si(Li) detector, and a multichannel analyzer. The spectra were built up for 2000-6000 sec. The characteristic X lines were integrated and normalized to source lines. The following Z ≥ 20 elements were detected in the studied composites: Ba only in Charisma (Kulzer) and Pekafill (Bayer); Zr, Ba, Yb in Tetric Ceram, and Ca, Ba, Yb together with traces of possibly Ti and Fe in Ariston (both from Vivadent); Zr, Hf in Valux Plus (3M Dental); and Sr, Ba together with some trace element, seemingly Cu, in F2000 Compomer (3M Dental) and with other trace elements like Ca, Fe in Surefil (Dentsply). Among older materials, Concise (3M Dental) contained only light (Z 3 that releases F for protection of enamel and dentine. Yb, Zr, Ba, Hf improve the radiological opacity of the materials. Some elements may accompany others as

  8. Effect of different types of prosthetic platforms on stress-distribution in dental implant-supported prostheses

    Energy Technology Data Exchange (ETDEWEB)

    Minatel, Lurian [Pró-Reitoria de Pesquisa e Pós-graduação (PRPPG), Universidade do Sagrado Coração, USC, 10–50 Irmã Armindal, Jardim Brasil, Bauru, 17011–160, SP (Brazil); Verri, Fellippo Ramos [Department of Dental Materials and Prosthodontics, Araçatuba Dental School, UNESP - Univ Estadual Paulista, 1193 José Bonifácio Street, Vila Mendonça, Araçatuba 16015–050 (Brazil); Kudo, Guilherme Abu Halawa [Pró-Reitoria de Pesquisa e Pós-graduação (PRPPG), Universidade do Sagrado Coração, USC, 10–50 Irmã Armindal, Jardim Brasil, Bauru, 17011–160, SP (Brazil); Faria Almeida, Daniel Augusto de; Souza Batista, Victor Eduardo de; Aparecido Araujo Lemos, Cleidiel; Piza Pellizzer, Eduardo [Department of Dental Materials and Prosthodontics, Araçatuba Dental School, UNESP - Univ Estadual Paulista, 1193 José Bonifácio Street, Vila Mendonça, Araçatuba 16015–050 (Brazil); and others

    2017-02-01

    A biomechanical analysis of different types of implant connections is relevant to clinical practice because it may impact the longevity of the rehabilitation treatment. Therefore, the objective of this study is to evaluate the Morse taper connections and the stress distribution of structures associated with the platform switching (PSW) concept. It will do this by obtaining data on the biomechanical behavior of the main structure in relation to the dental implant using the 3-dimensional finite element methodology. Four models were simulated (with each containing a single prosthesis over the implant) in the molar region, with the following specifications: M1 and M2 is an external hexagonal implant on a regular platform; M3 is an external hexagonal implant using PSW concept; and M4 is a Morse taper implant. The modeling process involved the use of images from InVesalius CT (computed tomography) processing software, which were refined using Rhinoceros 4.0 and SolidWorks 2011 CAD software. The models were then exported into the finite element program (FEMAP 11.0) to configure the meshes. The models were processed using NeiNastram software. The main results are that M1 (regular diameter 4 mm) had the highest stress concentration area and highest microstrain concentration for bone tissue, dental implants, and the retaining screw (P < 0.05). Using the PSW concept increases the area of the stress concentrations in the retaining screw (P < 0.05) more than in the regular platform implant. It was concluded that the increase in diameter is beneficial for stress distribution and that the PSW concept had higher stress concentrations in the retaining screw and the crown compared to the regular platform implant. - Highlights: • The external hexagon implants was unfavorable biomechanical. • The Morse taper implant presented the best biomechanical result. • Platform switching concept increased stress in screw-retained prostheses.

  9. Effect of different types of prosthetic platforms on stress-distribution in dental implant-supported prostheses

    International Nuclear Information System (INIS)

    Minatel, Lurian; Verri, Fellippo Ramos; Kudo, Guilherme Abu Halawa; Faria Almeida, Daniel Augusto de; Souza Batista, Victor Eduardo de; Aparecido Araujo Lemos, Cleidiel; Piza Pellizzer, Eduardo

    2017-01-01

    A biomechanical analysis of different types of implant connections is relevant to clinical practice because it may impact the longevity of the rehabilitation treatment. Therefore, the objective of this study is to evaluate the Morse taper connections and the stress distribution of structures associated with the platform switching (PSW) concept. It will do this by obtaining data on the biomechanical behavior of the main structure in relation to the dental implant using the 3-dimensional finite element methodology. Four models were simulated (with each containing a single prosthesis over the implant) in the molar region, with the following specifications: M1 and M2 is an external hexagonal implant on a regular platform; M3 is an external hexagonal implant using PSW concept; and M4 is a Morse taper implant. The modeling process involved the use of images from InVesalius CT (computed tomography) processing software, which were refined using Rhinoceros 4.0 and SolidWorks 2011 CAD software. The models were then exported into the finite element program (FEMAP 11.0) to configure the meshes. The models were processed using NeiNastram software. The main results are that M1 (regular diameter 4 mm) had the highest stress concentration area and highest microstrain concentration for bone tissue, dental implants, and the retaining screw (P < 0.05). Using the PSW concept increases the area of the stress concentrations in the retaining screw (P < 0.05) more than in the regular platform implant. It was concluded that the increase in diameter is beneficial for stress distribution and that the PSW concept had higher stress concentrations in the retaining screw and the crown compared to the regular platform implant. - Highlights: • The external hexagon implants was unfavorable biomechanical. • The Morse taper implant presented the best biomechanical result. • Platform switching concept increased stress in screw-retained prostheses.

  10. Analysis of dental abfractions by optical coherence tomography

    Science.gov (United States)

    Demjan, Enikö; Mărcăuţeanu, Corina; Bratu, Dorin; Sinescu, Cosmin; Negruţiu, Meda; Ionita, Ciprian; Topală, Florin; Hughes, Michael; Bradu, Adrian; Dobre, George; Podoleanu, Adrian Gh.

    2010-02-01

    Aim and objectives. Abfraction is the pathological loss of cervical hard tooth substance caused by biomechanical overload. High horizontal occlusal forces result in large stress concentrations in the cervical region of the teeth. These stresses may be high enough to cause microfractures in the dental hard tissues, eventually resulting in the loss of cervical enamel and dentin. The present study proposes the microstructural characterization of these cervical lesions by en face optical coherence tomography (eFOCT). Material and methods: 31 extracted bicuspids were investigated using eFOCT. 24 teeth derived from patients with active bruxism and occlusal interferences; they presented deep buccal abfractions and variable degrees of occlusal pathological attrition. The other 7 bicuspids were not exposed to occlusal overload and had a normal morphology of the dental crowns. The dental samples were investigated using an eFOCT system operating at 1300 nm (B-scan at 1 Hz and C-scan mode at 2 Hz). The system has a lateral resolution better than 5 μm and a depth resolution of 9 μm in tissue. OCT images were further compared with micro - computer tomography images. Results. The eFOCT investigation of bicuspids with a normal morphology revealed a homogeneous structure of the buccal cervical enamel. The C-scan and B-scan images obtained from the occlusal overloaded bicuspids visualized the wedge-shaped loss of cervical enamel and damage in the microstructure of the underlaying dentin. The high occlusal forces produced a characteristic pattern of large cracks, which reached the tooth surface. Conclusions: eFOCT is a promising imaging method for dental abfractions and it may offer some insight on the etiological mechanism of these noncarious cervical lesions.

  11. Perceived stress latent factors and the burnout subtypes: a structural model in dental students.

    Science.gov (United States)

    Montero-Marín, Jesús; Piva Demarzo, Marcelo Marcos; Stapinski, Lexine; Gili, Margarita; García-Campayo, Javier

    2014-01-01

    Students of health-professions suffer high levels of stress and burnout. The aim of the present study was to evaluate the relationship between perceived stress latent factors ('tenseness' and 'frustration') and the features ('overload', 'lack of development' and 'neglect') of the three burnout subtypes ('frenetic', 'under-challenged' and 'worn-out', respectively), in a sample of Spanish dental students. The study employed a cross-sectional design. A sample of Spanish dental students (n = 314) completed the 'Perceived Stress Questionnaire' and the 'Burnout Clinical Subtype Questionnaire Student Survey'. The associations among variables were observed by means of structural equation modelling using the unweighted least squares method from polychoric correlations. Strong associations among perceived stress factors and the burnout characteristics were observed, although a distinct pattern of relations was observed for each burnout subtype. The 'overload' was moderately and positively associated with both 'tenseness' (0.45), and 'frustration' (0.38) dimensions of perceived stress; the 'lack of development' was positively associated with the 'frustration' dimension (0.72), but negatively associated with 'tenseness' (-0.69); the 'neglect' showed a weaker positive associated with 'frustration' (0.41), and a small negative association with 'tenseness' (-0.20). The model was a very good fit to the data (GFI  =  0.96; RSMR  =  0.07; AGFI = 0.96; NFI = 0.95; RFI = 0.95). The stress factors of 'frustration' and 'tenseness' seems to be related in a distinct way to the burnout subtypes in Spanish dental students. This finding suggests that intervention programs specifically tailored to these subtypes may be a promising future direction.

  12. Perceived stress latent factors and the burnout subtypes: a structural model in dental students.

    Directory of Open Access Journals (Sweden)

    Jesús Montero-Marín

    Full Text Available Students of health-professions suffer high levels of stress and burnout. The aim of the present study was to evaluate the relationship between perceived stress latent factors ('tenseness' and 'frustration' and the features ('overload', 'lack of development' and 'neglect' of the three burnout subtypes ('frenetic', 'under-challenged' and 'worn-out', respectively, in a sample of Spanish dental students.The study employed a cross-sectional design. A sample of Spanish dental students (n = 314 completed the 'Perceived Stress Questionnaire' and the 'Burnout Clinical Subtype Questionnaire Student Survey'. The associations among variables were observed by means of structural equation modelling using the unweighted least squares method from polychoric correlations.Strong associations among perceived stress factors and the burnout characteristics were observed, although a distinct pattern of relations was observed for each burnout subtype. The 'overload' was moderately and positively associated with both 'tenseness' (0.45, and 'frustration' (0.38 dimensions of perceived stress; the 'lack of development' was positively associated with the 'frustration' dimension (0.72, but negatively associated with 'tenseness' (-0.69; the 'neglect' showed a weaker positive associated with 'frustration' (0.41, and a small negative association with 'tenseness' (-0.20. The model was a very good fit to the data (GFI  =  0.96; RSMR  =  0.07; AGFI = 0.96; NFI = 0.95; RFI = 0.95.The stress factors of 'frustration' and 'tenseness' seems to be related in a distinct way to the burnout subtypes in Spanish dental students. This finding suggests that intervention programs specifically tailored to these subtypes may be a promising future direction.

  13. Dental Workforce Availability and Dental Services Utilization in Appalachia: A Geospatial Analysis

    Science.gov (United States)

    Feng, Xue; Sambamoorthi, Usha; Wiener, R. Constance

    2016-01-01

    Objectives There is considerable variation in dental services utilization across Appalachian counties, and a plausible explanation is that individuals in some geographical areas do not utilize dental care due to dental workforce shortage. We conducted an ecological study on dental workforce availability and dental services utilization in Appalachia. Methods We derived county-level (n = 364) data on demographic, socio-economic characteristics and dental services utilization in Appalachia from the 2010 Behavioral Risk Factor Surveillance System (BRFSS) using person-level data. We obtained county-level dental workforce availability and physician-to-population ratio estimates from Area Health Resource File, and linked them to the county-level BRFSS data. The dependent variable was the proportion using dental services within the last year in each county (ranging from 16.6% to 91.0%). We described the association between dental workforce availability and dental services utilization using ordinary least squares regression and spatial regression techniques. Spatial analyses consisted of bivariate Local Indicators of Spatial Association (LISA) and geographically weighted regression (GWR). Results Bivariate LISA showed that counties in the central and southern Appalachian regions had significant (p dental workforce availability, low percent dental services utilization). GWR revealed considerable local variations in the association between dental utilization and dental workforce availability. In the multivariate GWR models, 8.5% (t-statistics >1.96) and 13.45% (t-statistics >1.96) of counties showed positive and statistically significant relationships between the dental services utilization and workforce availability of dentists and dental hygienists, respectively. Conclusions Dental workforce availability was associated with dental services utilization in the Appalachian region; however, this association was not statistically significant in all counties. The findings suggest

  14. The cost minimization analysis of an outreach dental service: a pilot ...

    African Journals Online (AJOL)

    For people with limited or no access to oral health care services, outreach dental services may be used to reduce oral health inequality. There is however paucity of information on the economic analysis of outreach dental services in sub Saharan Africa. Objective: To report a cost minimization analysis of an outreach dental ...

  15. Key steps in the strategic analysis of a dental practice.

    Science.gov (United States)

    Armstrong, J L; Boardman, A E; Vining, A R

    1999-01-01

    As dentistry is becoming increasingly competitive, dentists must focus more on strategic analysis. This paper lays out seven initial steps that are the foundation of strategic analysis. It introduces and describes the use of service-customer matrices and location-proximity maps as tools in competitive positioning. The paper also contains a brief overview of the role of differentiation and cost-control in determining key success factors for dental practices.

  16. Clinical evaluation of nonsyndromic dental anomalies in Dravidian population: A cluster sample analysis

    OpenAIRE

    Yamunadevi, Andamuthu; Selvamani, M.; Vinitha, V.; Srivandhana, R.; Balakrithiga, M.; Prabhu, S.; Ganapathy, N.

    2015-01-01

    Aim: To record the prevalence rate of dental anomalies in Dravidian population and analyze the percentage of individual anomalies in the population. Methodology: A cluster sample analysis was done, where 244 subjects studying in a dental institution were all included and analyzed for occurrence of dental anomalies by clinical examination, excluding third molars from analysis. Results: 31.55% of the study subjects had dental anomalies and shape anomalies were more prevalent (22.1%), followed b...

  17. Meditation - A Powerful Stress Buster in Dental Care Professionals

    Directory of Open Access Journals (Sweden)

    Rajeev Saxena

    2012-01-01

    Full Text Available Meditation is an umbrella term that encompasses a family of practices. In state of meditation there is total relaxation of body & mind. Control of breathing & doing nothing are the basic steps. The practice of meditation creates a balanced, rhythmic & naturally flowing pulsation of life through every part of the body. It transfers the struggling- stressful & exhausted life into a peaceful one. That life is full of health, creativity, love & compassion. Such type of greatest adventure only ′human mind′ can undertake. For meditation, there is no need to escape from the life. It is a simple technique that does not require sophisticated or complicated amenities.

  18. Inorganic particle analysis of dental impression elastomers.

    Science.gov (United States)

    Carlo, Hugo Lemes; Fonseca, Rodrigo Borges; Soares, Carlos José; Correr, Américo Bortolazzo; Correr-Sobrinho, Lourenço; Sinhoreti, Mário Alexandre Coelho

    2010-01-01

    The aim of this study was to determine quantitatively and qualitatively the inorganic particle fraction of commercially available dental elastomers. The inorganic volumetric fraction of two addition silicones (Reprosil Putty/Fluid and Flexitime Easy Putty/Fluid), three condensation silicones (Clonage Putty/Fluid, Optosil Confort/Xantopren VL and Silon APS Putty/Fluid), one polyether (Impregum Soft Light Body) and one polysulfide (Permlastic Light Body) was accessed by weighing a previously determined mass of each material in water before and after burning samples at 600 ºC, during 3 h. Unsettled material samples were soaked in acetone and chloroform for removal of the organic portion. The remaining filler particles were sputter-coated with gold evaluation of their morphology and size, under scanning electron microscopy (SEM). Flexitime Easy Putty was the material with the highest results for volumetric particle fraction, while Impregum Soft had the lowest values. Silon 2 APS Fluid presented the lowest mean filler size values, while Clonage Putty had the highest values. SEM micrographs of the inorganic particles showed several morphologies - lathe-cut, spherical, spherical-like, sticks, and sticks mixed to lathe-cut powder. The results of this study revealed differences in particle characteristics among the elastometic materials that could lead to different results when testing mechanical properties.

  19. [Symptoms of Depression, Anxiety and Stress Among Dental Students: Prevalence and Related Factors].

    Science.gov (United States)

    Arrieta Vergara, Katherine; Cárdenas, Shyrley Díaz; Martínez, Farith González

    2013-06-01

    To estimate the relationship between depressive symptoms, anxiety and stress and socio-demographic, academic and social factors among dental students. A cross-sectional study was carried out on dental students from a university in Cartagena, selected by simple random sampling. Students answered a self-report anonymous questionnaire of 20 questions that included demographic characteristics, depression, anxiety and stress symptoms (DASS scale 21), family function (APGAR family) and other factors associated with the academic, economic and social context. Data were analyzed computing odds ratios by binomial logistic regression. The prevalence of symptoms of anxiety, depression and stress were 37.4%, 56.6% and 45.4%, respectively. Factors associated with depressive symptoms were lack of support from friends (OR=6.2; 95%CI, 2.6-14.5), family dysfunction (OR=3.6; 95%CI, 1.9-6.6) and economic hardship (OR=2.2; 95%CI, 1.2-3.9). The anxiety symptoms were associated with family dysfunction (OR=3.1; 95%CI, 1.8-5.3) and lack of support from friends (OR=2.1; 95%CI, 1.1-5.8). Also for symptoms of stress factors family dysfunction (OR=2.3; 95%CI, 1.4-4.1), income (OR=2.4; 95%CI, 1.2-4.9) and time to rest (OR=2.3; 95%CI, 1.4-4.0). Dental students report a high prevalence of symptoms of anxiety, depression and stress. Associated factors are economic resources, family function, lack of time for rest, and social support. Copyright © 2013 Asociación Colombiana de Psiquiatría. Publicado por Elsevier España. All rights reserved.

  20. Brain aluminium accumulation and oxidative stress in the presence of calcium silicate dental cements.

    Science.gov (United States)

    Demirkaya, K; Demirdöğen, B Can; Torun, Z Öncel; Erdem, O; Çırak, E; Tunca, Y M

    2017-10-01

    Mineral trioxide aggregate (MTA) is a calcium silicate dental cement used for various applications in dentistry. This study was undertaken to test whether the presence of three commercial brands of calcium silicate dental cements in the dental extraction socket of rats would affect the brain aluminium (Al) levels and oxidative stress parameters. Right upper incisor was extracted and polyethylene tubes filled with MTA Angelus, MTA Fillapex or Theracal LC, or left empty for the control group, were inserted into the extraction socket. Rats were killed 7, 30 or 60 days after operation. Brain tissues were obtained before killing. Al levels were measured by atomic absorption spectrometry. Thiobarbituric acid reactive substances (TBARS) levels, catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were determined using spectrophotometry. A transient peak was observed in brain Al level of MTA Angelus group on day 7, while MTA Fillapex and Theracal LC groups reached highest brain Al level on day 60. Brain TBARS level, CAT, SOD and GPx activities transiently increased on day 7 and then returned to almost normal levels. This in vivo study for the first time indicated that initial washout may have occurred in MTA Angelus, while element leaching after the setting is complete may have taken place for MTA Fillapex and Theracal LC. Moreover, oxidative stress was induced and antioxidant enzymes were transiently upregulated. Further studies to search for oxidative neuronal damage should be done to completely understand the possible toxic effects of calcium silicate cements on the brain.

  1. Voice stress analysis and evaluation

    Science.gov (United States)

    Haddad, Darren M.; Ratley, Roy J.

    2001-02-01

    Voice Stress Analysis (VSA) systems are marketed as computer-based systems capable of measuring stress in a person's voice as an indicator of deception. They are advertised as being less expensive, easier to use, less invasive in use, and less constrained in their operation then polygraph technology. The National Institute of Justice have asked the Air Force Research Laboratory for assistance in evaluating voice stress analysis technology. Law enforcement officials have also been asking questions about this technology. If VSA technology proves to be effective, its value for military and law enforcement application is tremendous.

  2. OCT4B1 Regulates the Cellular Stress Response of Human Dental Pulp Cells with Inflammation

    Directory of Open Access Journals (Sweden)

    Lu Liu

    2017-01-01

    Full Text Available Introduction. Infection and apoptosis are combined triggers for inflammation in dental tissues. Octamer-binding transcription factor 4-B1 (OCT4B1, a novel spliced variant of OCT4 family, could respond to the cellular stress and possess antiapoptotic property. However, its specific role in dental pulpitis remains unknown. Methods. To investigate the effect of OCT4B1 on inflammation of dental pulp cells (DPCs, its expression in inflamed dental pulp tissues and DPCs was examined by in situ hybridization, real-time PCR, and FISH assay. OCT4B1 overexpressed DPCs model was established, confirmed by western blot and immunofluorescence staining, and then stimulated with Lipopolysaccharide (LPS. Apoptotic rate was determined by Hoechst/PI staining and FACS. Cell survival rate was calculated by CCK8 assay. Results. In situ hybridization, real-time PCR, and FISH assay revealed that OCT4B1 was extensively expressed in inflamed dental pulp tissues and DPCs with LPS stimulation. Western blot and immunofluorescence staining showed the expression of OCT4B1 and OCT4B increased after OCT4B1 transfection. Hoechst/PI staining and FACS demonstrated that less red/blue fluorescence was detected and apoptotic percentage decreased (3.45% after transfection. CCK8 demonstrated that the survival rate of pCDH-OCT4B1-flag cells increased. Conclusions. OCT4B1 plays an essential role in inflammation and apoptosis of DPCs. OCT4B might operate synergistically with OCT4B1 to reduce apoptosis.

  3. Salivary levels of SIgA and perceived stress among dental students

    Directory of Open Access Journals (Sweden)

    João Paulo Menck Sangiorgio

    2017-12-01

    Full Text Available Background: Academic stress may impair mucosal immunity and expose dental students to an increased risk of infections. Objective: to assess stress scores in dental students and their relationship with variation in SIgA levels. Methods: All students (n = 289 were invited to take part of the study, and 207 (71.63% effectively participated, being 152 (73.4% females. At the day of data collection, the students answered The Dental Environmental Stress Questionnaire (DES and unstimulated saliva samples were collected for determination of salivary flow rate and SIgA concentration and secretion rate. Results: Mean DES scores were higher in females (78.97 ± 16.42, but no correlations between the sum of DES scores and salivary parameters were observed (P=0.08. A moderate inverse relationship was observed between SIgA secretion rates and the subscales Academic Performance (P=0.01, Interpersonal relationships (P=0.02 and Difficulties and Insecurities about Professional Future (P=0.05. A weak correlation was found between SIgA concentration and the items Amount of assigned classwork (P=0.02, Lack of confidence in self to be a successful dentist (P=0.01, Lack of time for relaxation (P=0.01, Financial responsibilities (P=0.02 and Personal physical health (P=0.005. Weak correlations between SIgA secretion rates and DES items were also found for Lack of cooperation by patient in their home care (P=0.003, Patients being late or not showing up for their appointments (P=0.02, Lack of self confidence to be a successful dentist (P=0.008, Personal physical health (P=0.019, and others. Conclusion: Different sources of stress were observed among first to fifth year students and some of these stressors may negatively impact on salivary SIgA secretion.

  4. Biomechanical Analysis of Individual All-Ceramic Abutments Used in Dental Implantology

    Directory of Open Access Journals (Sweden)

    Ziębowicz B.

    2016-09-01

    Full Text Available The paper presents the results of finite element analysis and experimental testing under simulated physiological loading conditions on issues shaping the functional properties of individual all-ceramic abutments manufactured by CAD/CAM technology. The conducted research have cognitive significance showing the all-ceramic abutment behavior, as a key element of the implantological system, under the action of cyclic load. The aim of this study was evaluation the fatigue behavior of yttria-stabilized zirconia abutment submitted to cyclic stresses, conducted in accordance with EN ISO 14801 applies to dynamic fatigue tests of endosseous dental implants.

  5. Traumatic Dental Injuries in the primary dentition: a 15-year bibliometric analysis of Dental Traumatology.

    Science.gov (United States)

    Kramer, Paulo Floriani; Onetto, Juan; Flores, Marie Therese; Borges, Tássia Silvana; Feldens, Carlos Alberto

    2016-10-01

    To explore the profile of articles on traumatic dental injuries (TDI) in the primary dentition published in Dental Traumatology in the last 15 years using bibliometric analysis. Three researchers read all titles and abstracts of articles published in Dental Traumatology between 2000 and 2014 (excluding editorials and letters) and selected all articles on TDI in the primary dentition. The articles were categorized according to year of publication, country in which the study was conducted, study design, and topics addressed. Divergences were resolved by consensus between the researchers. Among a total of 1257 articles published, 98 were initially excluded. Among the remaining 1159 articles, 152 (13.1%) focused on TDI in the primary dentition. The articles were conducted in 29 countries, with Brazil (38.8%) and Turkey (11.8%) accounting for the largest numbers. Cross-sectional studies (36.2%) and case report/case series (33.6%) were the most frequent study designs. Only two systematic reviews were published. The most commonly addressed topics were frequency/etiology/associated factors (36.8%), treatment (30.9%), and prognosis (19.7%). Among the articles addressing treatment, two-thirds were case reports or case series. The effects of TDI in primary teeth on their permanent successors were addressed in 20.4% of the articles (31/152). The number of articles on TDI in the primary dentition has increased, but remains low. The evaluation of study designs and topics addressed identified gaps that could contribute to the development of new studies on TDI in the primary dentition, especially cohort studies that evaluate risk factors, prognosis, and treatment. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  6. Perceived sources of stress among postgraduate students of a dental college in Karnataka, India

    Directory of Open Access Journals (Sweden)

    M J Mathew

    2017-01-01

    Full Text Available Introduction: Dentistry has for some time been viewed as a profession with high-stress, and usually this begins from the days of dental school onward. Students are subjected to different kinds of stressors, some being the pressure from academics with an obligation to succeed, uncertainty regarding their future and difficulties of integrating into the system. Aim: The aim is to identify the perceived sources of stress among postgraduate students from a dental college in Coorg, Karnataka. Materials and Methods: A cross-sectional questionnaire study was carried out, and the study samples included all the postgraduates of all nine specialties, including all the seventy-seven postgraduate students as samples. Results: Stress was relatively general among all the groups of the study participants, certain factors or stressors such as the amount of assigned work, competition with peers, examination and grades, lack of confidence to be a successful student and fear of facing parents after failure hamper the academic life of these students and had more significance among groups when compared to others. Conclusion: The academic life of students seemed to be hampered due to various potential stressors such as the amount of assigned work, competition with peers, examination and grades, lack of confidence to be a successful student, and fear of facing parents after failure. Such issues that arise in the educational setting need to be addressed which will help improve the academic environment of the students.

  7. On stress/strain shielding and the material stiffness paradigm for dental implants.

    Science.gov (United States)

    Korabi, Raoof; Shemtov-Yona, Keren; Rittel, Daniel

    2017-10-01

    Stress shielding considerations suggest that the dental implant material's compliance should be matched to that of the host bone. However, this belief has not been confirmed from a general perspective, either clinically or numerically. To characterize the influence of the implant stiffness on its functionality using the failure envelope concept that examines all possible combinations of mechanical load and application angle for selected stress, strain and displacement-based bone failure criteria. Those criteria represent bone yielding, remodeling, and implant primary stability, respectively MATERIALS AND METHODS: We performed numerical simulations to generate failure envelopes for all possible loading configurations of dental implants, with stiffness ranging from very low (polymer) to extremely high, through that of bone, titanium, and ceramics. Irrespective of the failure criterion, stiffer implants allow for improved implant functionality. The latter reduces with increasing compliance, while the trabecular bone experiences higher strains, albeit of an overall small level. Micromotions remain quite small irrespective of the implant's stiffness. The current paradigm favoring reduced implant material's stiffness out of concern for stress or strain shielding, or even excessive micromotions, is not supported by the present calculations, that point exactly to the opposite. © 2017 Wiley Periodicals, Inc.

  8. Dental caries and childhood obesity: analysis of food intakes, lifestyle.

    Science.gov (United States)

    Costacurta, M; DiRenzo, L; Sicuro, L; Gratteri, S; De Lorenzo, A; Docimo, R

    2014-12-01

    The aims of this cross-sectional statistical study were to evaluate the association between obesity and dental caries and to assess the impact of food intake, oral hygiene and lifestyle on the incidence of dental caries in obese paediatric patients, analysed by Dual X-ray Absorptiometry (DXA). A sample of 96 healthy patients, aged between 6 and 11 years (mean age 8.58±1.43) was classified in relation to body composition assessment and McCarthy growth charts and cut- offs. Body composition analysis, to obtain body fat mass (FM) and body fat free mass (FFM) measurements, was determined by means of a DXA fan beam scanner. The subjects underwent dental examination to assess the dmft/DMFT, and completed a questionnaire on food intake, oral hygiene habits and lifestyle. The sample was subsequently subdivided into four groups: Group A (normal weight - caries-free), Group B (normal weight with caries), Group C (pre-obese/obese - caries-free), Group D (pre-obese/obese with caries). The statistical analysis was performed using SPSS software (version 16; SPSS Inc., Chicago IL, USA). Spearman's correlation was performed to evaluate the correlation between dmft/DMFT and FM%. The chi-square test was performed to assess the categorical variables, while the non-parametric Kruskal Wallis test and the Mann Whitney test were employed for the quantitive variables. Statististical significance was set at a P-value of 0.05. The preobese-obese children had higher indexes of dental caries than normal weight subjects, both for deciduous teeth (dmft 2.5 ± 0.54 vs 1.4 ± 0.38; p=0.030) and permanent teeth (DMFT 2.8 ± 0.24 vs 1.93 ± 1.79; p=0.039). The correlations between dmft/DMFT indexes and body composition parameters were analysed and a significant correlation between dmft/DMFT indexes and FM% was observed (p=0.031 for dmft, p=0.022 for DMFT). According to the data recorded, there was no statistically significant difference between Groups A, B, C and D in terms of food intake between

  9. SRXRF analysis with spatial resolution of dental calculus

    International Nuclear Information System (INIS)

    Sanchez, Hector Jorge; Perez, Carlos Alberto; Grenon, Miriam

    2000-01-01

    This work presents elemental-composition studies of dental calculus by X-ray fluorescence analysis using synchrotron radiation. The intrinsic characteristics of synchrotron light allow for a semi-quantitative analysis with spatial resolution. The experiments were carried out in the high-vacuum station of the XRF beamline at the Synchrotron Light National Laboratory (Campinas, Brazil). All the measurements were performed in conventional geometry (45 deg. + 45 deg.) and the micro-collimation was attained via a pair of orthogonal slits mounted in the beamline. In this way, pixels of 50 μmx50 μm were obtained keeping a high flux of photons on the sample. Samples of human dental calculus were measured in different positions along their growing axis, in order to determine variations of the compositions in the pattern of deposit. Intensity ratios of minor elements and traces were obtained, and linear profiles and surface distributions were determined. As a general summary, we can conclude that μXRF experiments with spatial resolution on dental calculus are feasible with simple collimation and adequate positioning systems, keeping a high flux of photon. These results open interesting perspectives for the future station of the line, devoted to μXRF, which will reach resolutions of the order of 10 μm

  10. SRXRF analysis with spatial resolution of dental calculus

    Science.gov (United States)

    Sánchez, Héctor Jorge; Pérez, Carlos Alberto; Grenón, Miriam

    2000-09-01

    This work presents elemental-composition studies of dental calculus by X-ray fluorescence analysis using synchrotron radiation. The intrinsic characteristics of synchrotron light allow for a semi-quantitative analysis with spatial resolution. The experiments were carried out in the high-vacuum station of the XRF beamline at the Synchrotron Light National Laboratory (Campinas, Brazil). All the measurements were performed in conventional geometry (45°+45°) and the micro-collimation was attained via a pair of orthogonal slits mounted in the beamline. In this way, pixels of 50 μm×50 μm were obtained keeping a high flux of photons on the sample. Samples of human dental calculus were measured in different positions along their growing axis, in order to determine variations of the compositions in the pattern of deposit. Intensity ratios of minor elements and traces were obtained, and linear profiles and surface distributions were determined. As a general summary, we can conclude that μXRF experiments with spatial resolution on dental calculus are feasible with simple collimation and adequate positioning systems, keeping a high flux of photon. These results open interesting perspectives for the future station of the line, devoted to μXRF, which will reach resolutions of the order of 10 μm.

  11. Concept Analysis: Alzheimer's Caregiver Stress.

    Science.gov (United States)

    Llanque, Sarah; Savage, Lynette; Rosenburg, Neal; Caserta, Michael

    2016-01-01

    The aim of this article was to analyze the concept of caregiver stress in the context of caring for a person with Alzheimer's disease and related dementias. Currently, there are more than 15 million unpaid caregivers for persons suffering from Alzheimer's disease and related dementias. This unpaid care can be stressful for caregivers due to the chronic nature of the disease process, as well as other factors. The paper incorporates the modified method of Wilson's concept analysis procedure to analyze the concept of caregiver stress. A review of the literature was undertaken using the Cumulative Index to Nursing and Allied Health Literature, Google Scholar, and PubMed. A theoretical definition of caregiver stress is provided, and the defining attributes, related concepts, antecedents, and consequences of caregiver stress are proposed, and case studies are presented. The analysis demonstrates that caregiver stress is the unequal exchange of assistance among people who stand in close relationship to one another, which results in emotional and physical stress on the caregiver. Implications for future nursing research and practice conclude the paper. © 2014 Wiley Periodicals, Inc.

  12. PDX vacuum vessel stress analysis

    International Nuclear Information System (INIS)

    Nikodem, Z.D.

    1975-01-01

    A stress analysis of PDX vacuum vessel is described and the summary of results is presented. The vacuum vessel is treated as a toroidal shell of revolution subjected to an internal vacuum. The critical buckling pressure is calculated. The effects of the geometrical discontinuity at the juncture of toroidal shell head and cylindrical outside wall, and the concavity of the cylindrical wall are examined. An effect of the poloidal field coil supports and the vessel outside supports on the stress distribution in the vacuum vessel is determined. A method evaluating the influence of circular ports in the vessel wall on the stress level in the vessel is outlined

  13. Stress analysis of pressure vessels

    International Nuclear Information System (INIS)

    Kim, B.K.; Song, D.H.; Son, K.H.; Kim, K.S.; Park, K.B.; Song, H.K.; So, J.Y.

    1979-01-01

    This interim report contains the results of the effort to establish the stress report preparation capability under the research project ''Stress analysis of pressure vessels.'' 1978 was the first year in this effort to lay the foundation through the acquisition of SAP V structural analysis code and a graphic terminal system for improved efficiency of using such code. Software programming work was developed in pre- and post processing, such as graphic presentation of input FEM mesh geometry and output deformation or mode shope patterns, which was proven to be useful when using the FEM computer code. Also, a scheme to apply fracture mechanics concept was developed in fatigue analysis of pressure vessels. (author)

  14. The Influence of Water Sorption of Dental Light-Cured Composites on Shrinkage Stress

    Directory of Open Access Journals (Sweden)

    Kinga Bociong

    2017-09-01

    Full Text Available The contraction stress generated during the photopolymerization of resin dental composites is the major disadvantage. The water sorption in the oral environment should counteract the contraction stress. The purpose was to evaluate the influence of the water sorption of composite materials on polymerization shrinkage stress generated at the restoration-tooth interface. The following materials were tested: Filtek Ultimate, Gradia Direct LoFlo, Heliomolar Flow, Tetric EvoCeram, Tetric EvoCeram Bulk Fill, Tetric EvoFlow, Tetric EvoFlow Bulk Fill, X-tra Base, Venus BulkFil, and Ceram.X One. The shrinkage stress was measured immediately after curing and after: 0.5 h, 24 h, 72 h, 96 h, 168 h, 240 h, 336 h, 504 h, 672 h, and 1344 h by means of photoelastic study. Moreover, water sorption and solubility were evaluated. Material samples were weighted on scale in time intervals to measure the water absorbency and the dynamic of this process. The tested materials during polymerization generated shrinkage stresses ranging from 6.3 MPa to 12.5 MPa. Upon water conditioning (56 days, the decrease in shrinkage strain (not less than 48% was observed. The decrease in value stress in time is material-dependent.

  15. Statistical Analysis for Subjective and Objective Evaluations of Dental Drill Sounds.

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    Tomomi Yamada

    Full Text Available The sound produced by a dental air turbine handpiece (dental drill can markedly influence the sound environment in a dental clinic. Indeed, many patients report that the sound of a dental drill elicits an unpleasant feeling. Although several manufacturers have attempted to reduce the sound pressure levels produced by dental drills during idling based on ISO 14457, the sound emitted by such drills under active drilling conditions may negatively influence the dental clinic sound environment. The physical metrics related to the unpleasant impressions associated with dental drill sounds have not been determined. In the present study, psychological measurements of dental drill sounds were conducted with the aim of facilitating improvement of the sound environment at dental clinics. Specifically, we examined the impressions elicited by the sounds of 12 types of dental drills in idling and drilling conditions using a semantic differential. The analysis revealed that the impressions of dental drill sounds varied considerably between idling and drilling conditions and among the examined drills. This finding suggests that measuring the sound of a dental drill in idling conditions alone may be insufficient for evaluating the effects of the sound. We related the results of the psychological evaluations to those of measurements of the physical metrics of equivalent continuous A-weighted sound pressure levels (LAeq and sharpness. Factor analysis indicated that impressions of the dental drill sounds consisted of two factors: "metallic and unpleasant" and "powerful". LAeq had a strong relationship with "powerful impression", calculated sharpness was positively related to "metallic impression", and "unpleasant impression" was predicted by the combination of both LAeq and calculated sharpness. The present analyses indicate that, in addition to a reduction in sound pressure level, refining the frequency components of dental drill sounds is important for creating a

  16. Analysis of terminological literacy of dental lexicon

    Directory of Open Access Journals (Sweden)

    N. N. Fejzrahmanova

    2014-01-01

    Full Text Available The paper contains the quantitative analysis of contextual lexical literacy of 9 magazines and 3 illustrated newspapers (218 articles on stomatology, 9 textbooks, 28 manuals for higher education institutions, 148 theses from the collections of scientific works. Besides, 126 headings of articles and 57 reports, lectures, seminars are analyzed. Calculations of relative and absolute measures were carried out by the formulas offered by authors of the work. Thus the rather high percent of the errors in written and oral speech of dentists was revealed in all tested editions. On the basis of the received results the authors drew the conclusion of the necessary inclusion of lexical and terminological courses in educational process and creation of active forms of standard highly specialized dictionaries which need to be used as manuals in training process.

  17. Tackling stress management, addiction, and suicide prevention in a predoctoral dental curriculum.

    Science.gov (United States)

    Brondani, Mario A; Ramanula, Dhorea; Pattanaporn, Komkhamn

    2014-09-01

    Health care professionals, particularly dentists, are subject to high levels of stress. Without proper stress management, problems related to mental health and addiction and, to a lesser extent, deliberate self-harm such as suicide may arise. There is a lack of information on teaching methodologies employed to discuss stress management and suicide prevention in dental education. The purpose of this article is to describe a University of British Columbia Faculty of Dentistry module designed to address stress management and suicide prevention, using students' personal reflections to illustrate the impact of the pedagogies used. The module enrolls more than 200 students per year and has sessions tailored to the discussion of stress management and suicide prevention. The pedagogies include standardized patients, invited guest lectures, in-class activities, video presentation, and self-reflections. More than 500 students' self-reflections collected over the past five years illustrate the seriousness of the issues discussed and the level of discomfort students experience when pondering such issues. The instructors hope to have increased students' awareness of the stressors in their profession. Further studies are needed to unravel the extent to which such pedagogy influences a balanced practice of dentistry.

  18. Effectiveness of benzocaine in reducing deep cavity restoration and post-extraction stress in dental patients

    Directory of Open Access Journals (Sweden)

    Khalid H. Al-Samadani

    2015-11-01

    Full Text Available Objectives: To investigate the effectiveness of topical anesthetic, 20% benzocaine in relieving pain and stress in patients following deep cavity restoration and extraction of teeth under local anesthesia (LA. Methods: A prospective clinical trial was conducted from October 2014 until April 2015 at Taibah University, Al Madinah Al Munawarah, Kingdom of Saudi Arabia. Forty-five patients were included in the 20% benzocaine group, and 46 in the normal saline group. Evaluation of the dental stress was made pre-operatively and immediately post-operative treatment using the visual analogue scale (VAS. Furthermore, discomfort of the injections were recorded by the patients after each treatment on standard 100 mm VAS, tagged at the endpoints with “no pain” (0 mm and “unbearable pain” (100 mm. Results: There were statistically significant differences between the mean stress scores for patients in the benzocaine and normal saline groups post-operatively (p=0.002. There were significant differences between the mean pain scores for patients in the post buccal injection (p=0.001, post palatal injection (p=0.01, and the post inferior alveolar nerve block groups (p=0.02. Buccal, palatal, and inferior alveolar nerve block injections were more painful for patients in the normal saline group than the benzocaine group. Conclusion: This investigation has demonstrated that post-operative stress associated with deep cavity restoration and dental extractions under LA can be reduced by the application of topical anesthetic (20% benzocaine at the operative site for intra-oral injections.

  19. [Evaluation of dental plaque by quantitative digital image analysis system].

    Science.gov (United States)

    Huang, Z; Luan, Q X

    2016-04-18

    To analyze the plaque staining image by using image analysis software, to verify the maneuverability, practicability and repeatability of this technique, and to evaluate the influence of different plaque stains. In the study, 30 volunteers were enrolled from the new dental students of Peking University Health Science Center in accordance with the inclusion criteria. The digital images of the anterior teeth were acquired after plaque stained according to filming standardization.The image analysis was performed using Image Pro Plus 7.0, and the Quigley-Hein plaque indexes of the anterior teeth were evaluated. The plaque stain area percentage and the corresponding dental plaque index were highly correlated,and the Spearman correlation coefficient was 0.776 (Pchart showed only a few spots outside the 95% consistency boundaries. The different plaque stains image analysis results showed that the difference of the tooth area measurements was not significant, while the difference of the plaque area measurements significant (P<0.01). This method is easy in operation and control,highly related to the calculated percentage of plaque area and traditional plaque index, and has good reproducibility.The different plaque staining method has little effect on image segmentation results.The sensitive plaque stain for image analysis is suggested.

  20. Influence of Preparatory Workshops on Dental Students' Academic Performance and Stress on Their First Operative Dentistry Psychomotor Exam.

    Science.gov (United States)

    Dilbone, Deborah A; Feng, Xiaoying; Su, Yu; Xirau-Probert, Patricia; Behar-Horenstein, Linda S; Nascimento, Marcelle M

    2018-06-01

    Predoctoral dental psychomotor examinations are known to generate high levels of stress among dental students, which may compromise their academic performance. At one U.S. dental school, all 93 first-year dental students were invited to attend a series of three workshop sessions prior to enrollment in their initial operative dentistry course. The workshops were developed to facilitate academic transition from the dental anatomy course to the operative dentistry course; provide early exposure to materials, instruments, and laboratory techniques; support the early development of psychomotor and self-assessment skills; and lessen students' stress and anxiety levels regarding psychomotor examinations. The aim of this study was to assess the impact of the workshops on the students' academic performance and self-reported stress and preparedness. All students who attended the workshop sessions and all who did not were asked to complete a pre-exam survey (immediately preceding the exam) and a post-exam survey (immediately after the exam) on the day of their first operative dentistry psychomotor exam. Of the 93 students, 21 attended one, 34 attended two, and 25 attended three workshop sessions, while 13 students did not attend any. Response rates for the pre- and post-exam surveys were 100% and 98.9%, respectively. Students who attended all three workshop sessions reported being significantly less stressed about taking the exam than the other groups. The mean exam grade of students who attended the workshop sessions was significantly higher than that of students who did not attend the sessions. These findings support the development and implementation of preparatory workshops to improve academic performance and decrease the stress levels of dental students prior to the first operative dentistry psychomotor exam.

  1. Polymerization shrinkage kinetics and shrinkage-stress in dental resin-composites.

    Science.gov (United States)

    Al Sunbul, Hanan; Silikas, Nick; Watts, David C

    2016-08-01

    To investigate a set of resin-composites and the effect of their composition on polymerization shrinkage strain and strain kinetics, shrinkage stress and the apparent elastic modulus. Eighteen commercially available resin-composites were investigated. Three specimens (n=3) were made per material and light-cured with an LED unit (1200mW/cm(2)) for 20s. The bonded-disk method was used to measure the shrinkage strain and Bioman shrinkage stress instrument was used to measure shrinkage stress. The shrinkage strain kinetics at 23°C was monitored for 60min. Maximum strain and stress was evaluated at 60min. The shrinkage strain rate was calculated using numerical differentiation. The shrinkage strain values ranged from 1.83 (0.09) % for Tetric Evoceram (TEC) to 4.68 (0.04) % for Beautifil flow plus (BFP). The shrinkage strain rate ranged from 0.11 (0.01%s(-1)) for Gaenial posterior (GA-P) to 0.59 (0.07) %s(-1) for BFP. Shrinkage stress values ranged from 3.94 (0.40)MPa for TET to 10.45 (0.41)MPa for BFP. The apparent elastic modulus ranged from 153.56 (18.7)MPa for Ever X posterior (EVX) to 277.34 (25.5) MPa for Grandio SO heavy flow (GSO). The nature of the monomer system determines the amount of the bulk contraction that occurs during polymerization and the resultant stress. Higher values of shrinkage strain and stress were demonstrated by the investigated flowable materials. The bulk-fill materials showed comparable result when compared to the traditional resin-composites. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  2. Minimizing inter-microscope variability in dental microwear texture analysis

    Science.gov (United States)

    Arman, Samuel D.; Ungar, Peter S.; Brown, Christopher A.; DeSantis, Larisa R. G.; Schmidt, Christopher; Prideaux, Gavin J.

    2016-06-01

    A common approach to dental microwear texture analysis (DMTA) uses confocal profilometry in concert with scale-sensitive fractal analysis to help understand the diets of extinct mammals. One of the main benefits of DMTA over other methods is the repeatable, objective manner of data collection. This repeatability, however, is threatened by variation in results of DMTA of the same dental surfaces yielded by different microscopes. Here we compare DMTA data of five species of kangaroos measured on seven profilers of varying specifications. Comparison between microscopes confirms that inter-microscope differences are present, but we show that deployment of a number of automated treatments to remove measurement noise can help minimize inter-microscope differences. Applying these same treatments to a published hominin DMTA dataset shows that they alter some significant differences between dietary groups. Minimising microscope variability while maintaining interspecific dietary differences requires then that these factors are balanced in determining appropriate treatments. The process outlined here offers a solution for allowing comparison of data between microscopes, which is essential for ongoing DMTA research. In addition, the process undertaken, including considerations of other elements of DMTA protocols also promises to streamline methodology, remove measurement noise and in doing so, optimize recovery of a reliable dietary signature.

  3. Mechanical and Spectroscopic Analysis of Retrieved/Failed Dental Implants

    Directory of Open Access Journals (Sweden)

    Umer Daood

    2017-11-01

    Full Text Available The purpose of this study was to examine surface alterations and bone formation on the surface of failed dental implants (Straumann [ST] and TiUnite [TiUn] removed due to any biological reason. In addition, failure analysis was performed to test mechanical properties. Dental implants (n = 38 from two manufacturers were collected and subjected to chemical cleaning. The presence of newly formed hydroxyapatite bone around failed implants was evaluated using micro-Raman spectroscopy. Scanning electron microscopy was used to identify surface defects. Mechanical testing was performed using a Minneapolis servo-hydraulic system (MTS along with indentation using a universal testing machine and average values were recorded. A statistical analysis of mechanical properties was done using an unpaired t test, and correlation between observed defects was evaluated using Chi-square (p = 0.05. Apatite-formation was evident in both implants, but was found qualitatively more in the ST group. No significant difference was found in indentation between the two groups (p > 0.05. The percentage of “no defects” was significantly lower in the ST group (71%. Crack-like and full-crack defects were observed in 49% and 39% of TiUn. The ST group showed 11,061 cycles to failure as compared with 10,021 cycles in the TiUnite group. Implant failure mechanisms are complex with a combination of mechanical and biological reasons and these factors are variable with different implant systems.

  4. Stability of tapered and parallel-walled dental implants: A systematic review and meta-analysis.

    Science.gov (United States)

    Atieh, Momen A; Alsabeeha, Nabeel; Duncan, Warwick J

    2018-05-15

    Clinical trials have suggested that dental implants with a tapered configuration have improved stability at placement, allowing immediate placement and/or loading. The aim of this systematic review and meta-analysis was to evaluate the implant stability of tapered dental implants compared to standard parallel-walled dental implants. Applying the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement, randomized controlled trials (RCTs) were searched for in electronic databases and complemented by hand searching. The risk of bias was assessed using the Cochrane Collaboration's Risk of Bias tool and data were analyzed using statistical software. A total of 1199 studies were identified, of which, five trials were included with 336 dental implants in 303 participants. Overall meta-analysis showed that tapered dental implants had higher implant stability values than parallel-walled dental implants at insertion and 8 weeks but the difference was not statistically significant. Tapered dental implants had significantly less marginal bone loss compared to parallel-walled dental implants. No significant differences in implant failure rate were found between tapered and parallel-walled dental implants. There is limited evidence to demonstrate the effectiveness of tapered dental implants in achieving greater implant stability compared to parallel-walled dental implants. Superior short-term results in maintaining peri-implant marginal bone with tapered dental implants are possible. Further properly designed RCTs are required to endorse the supposed advantages of tapered dental implants in immediate loading protocol and other complex clinical scenarios. © 2018 Wiley Periodicals, Inc.

  5. Stress and Academic Performance in Dental Students: The Role of Coping Strategies and Examination-Related Self-Efficacy.

    Science.gov (United States)

    Crego, Antonio; Carrillo-Diaz, María; Armfield, Jason M; Romero, Martín

    2016-02-01

    Academic stress negatively affects students' performance. However, little is known of the processes that may be involved in this association. This study aimed to analyze how other variables such as coping strategies and exam-related self-efficacy could be related to academic stress and performance for dental students. An online survey, including measures of coping strategies, perceived stress, exam-related self-efficacy, and academic performance, was completed by undergraduate dental students in Madrid, Spain. Of the 275 students invited to take the survey, 201 participated (response rate 73.6%). Rational coping strategies (problem-solving, positive reappraisal, seeking social support) were negatively associated with perceived stress (β=-0.25, pemotional coping strategies (venting negative emotions, negative auto-focus) were linked to increased academic stress (β=0.34, prational and emotional coping strategies were, respectively, positively (β=0.16, prational coping) may help to reduce stress for dental students and, through their effect on exam-related self-efficacy appraisals, contribute to improved academic performance.

  6. Surface analysis of titanium dental implants with different topographies

    Directory of Open Access Journals (Sweden)

    Silva M.H. Prado da

    2000-01-01

    Full Text Available Cylindrical dental implants made of commercially pure titanium were analysed in four different surface finishes: as-machined, Al2O3 blasted with Al2O3 particles, plasma-sprayed with titanium beads and electrolytically coated with hydroxyapatite. Scanning electron microscopy (SEM with Energy Dispersive X-ray Analysis (EDX revealed the topography of the surfaces and provided qualitative results of the chemical composition of the different implants. X-ray Photoelectron Spectroscopy (XPS was used to perform chemical analysis on the surface of the implants while Laser Scanning Confocal Microscopy (LSM produced topographic maps of the analysed surfaces. Optical Profilometry was used to quantitatively characterise the level of roughness of the surfaces. The implant that was plasma-sprayed and the hydroxyapatite coated implant showed the roughest surface, followed by the implant blasted with alumina and the as-machined implant. Some remnant contamination from the processes of blasting, coating and cleaning was detected by XPS.

  7. Human dental pulp cells exhibit bone cell-like responsiveness to fluid shear stress.

    Science.gov (United States)

    Kraft, David Christian Evar; Bindslev, Dorth Arenholt; Melsen, Birte; Klein-Nulend, Jenneke

    2011-02-01

    For engineering bone tissue to restore, for example, maxillofacial defects, mechanosensitive cells are needed that are able to conduct bone cell-specific functions, such as bone remodelling. Mechanical loading affects local bone mass and architecture in vivo by initiating a cellular response via loading-induced flow of interstitial fluid. After surgical removal of ectopically impacted third molars, human dental pulp tissue is an easily accessible and interesting source of cells for mineralized tissue engineering. The aim of this study was to determine whether human dental pulp-derived cells (DPC) are responsive to mechanical loading by pulsating fluid flow (PFF) upon stimulation of mineralization in vitro. Human DPC were incubated with or without mineralization medium containing differentiation factors for 3 weeks. Cells were subjected to 1-h PFF (0.7 ± 0.3 Pa, 5 Hz) and the response was quantified by measuring nitric oxide (NO) and prostaglandin E₂ (PGE₂) production, and gene expression of cyclooxygenase (COX)-1 and COX-2. We found that DPC are intrinsically mechanosensitive and, like osteogenic cells, respond to PFF-induced fluid shear stress. PFF stimulated NO and PGE₂ production, and up-regulated COX-2 but not COX-1 gene expression. In DPC cultured under mineralizing conditions, the PFF-induced NO, but not PGE₂, production was significantly enhanced. These data suggest that human DPC, like osteogenic cells, acquire responsiveness to pulsating fluid shear stress in mineralizing conditions. Thus DPC might be able to perform bone-like functions during mineralized tissue remodeling in vivo, and therefore provide a promising new tool for mineralized tissue engineering to restore, for example, maxillofacial defects.

  8. Short dental implants versus standard dental implants placed in the posterior jaws: A systematic review and meta-analysis.

    Science.gov (United States)

    Lemos, Cleidiel Aparecido Araujo; Ferro-Alves, Marcio Luiz; Okamoto, Roberta; Mendonça, Marcos Rogério; Pellizzer, Eduardo Piza

    2016-04-01

    The purpose of the present systematic review and meta-analysis was to compare short implants (equal or less than 8mm) versus standard implants (larger than 8mm) placed in posterior regions of maxilla and mandible, evaluating survival rates of implants, marginal bone loss, complications and prosthesis failures. This review has been registered at PROSPERO under the number CRD42015016588. Main search terms were used in combination: dental implant, short implant, short dental implants, short dental implants posterior, short dental implants maxilla, and short dental implants mandible. An electronic search for data published up until September/2015 was undertaken using the PubMed/Medline, Embase and The Cochrane Library databases. Eligibility criteria included clinical human studies, randomized controlled trials and/or prospective studies, which evaluated short implants in comparison to standard implants in the same study. The search identified 1460 references, after inclusion criteria 13 studies were assessed for eligibility. A total of 1269 patients, who had received a total of 2631 dental implants. The results showed that there was no significant difference of implants survival (P=.24; RR:1.35; CI: 0.82-2.22), marginal bone loss (P=.06; MD: -0.20; CI: -0.41 to 0.00), complications (P=.08; RR:0.54; CI: 0.27-1.09) and prosthesis failures (P=.92; RR:0.96; CI: 0.44-2.09). Short implants are considered a predictable treatment for posterior jaws. However, short implants with length less than 8 mm (4-7 mm) should be used with caution because they present greater risks to failures compared to standard implants. Short implants are frequently placed in the posterior area in order to avoid complementary surgical procedures. However, clinicians need to be aware that short implants with length less than 8mm present greater risk of failures. Copyright © 2016. Published by Elsevier Ltd.

  9. 14 CFR 33.62 - Stress analysis.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Stress analysis. 33.62 Section 33.62... STANDARDS: AIRCRAFT ENGINES Design and Construction; Turbine Aircraft Engines § 33.62 Stress analysis. A stress analysis must be performed on each turbine engine showing the design safety margin of each turbine...

  10. Qualitative PIXE analysis of mineral elements in some dental composites

    International Nuclear Information System (INIS)

    Preoteasa, E.A.; Iordan, Andreea; Harangus, Livia; Ciortea, C.; Gugiu, M.; Moldovan, Maria

    2002-01-01

    Dental composites, made by particles of glass, ceramics and quartz embedded in an organic polymer, develop at a high rate. However, commercial composites are expensive and recently the 'Restacril' biomaterials company became prepared to offer a low-cost alternative. The durability of dental fillings depends not only on biomaterial's gross chemical composition, but also on impurities. These may influence the chemical, mechanical and surface properties of the inorganic particles and modify the composites' clinical behavior. Thus elemental analysis is necessary to improve the biomaterials' quality. Nuclear and atomic methods allow sensitive multielement detection, and we previously analyzed some commercial composites by particle-induced X-ray emission (PIXE). Here we applied PIXE in the qualitative analysis of six new Romanian biomaterials, aiming to compare their nominal and detected composition and paying attention to the impurities. The PIXE measurements were performed with 3 MeV protons at the 8.5 MV NIPNE-HH tandem accelerator, using a hyper pure Ge detector, normal to the beam and connected to a multichannel analyzer and to a computer. Solid samples of composites with a flat surface were fixed at 45 angle, absorber foil of Al 30 mm thick was used, and integration of beam current was done. In all composites PIXE detected mineral elements with Z > 19 down to trace levels. All major nominal elements with Z > 20 - Ca, Sr, Zr, Ba, and Yb - were detected by PIXE. In addition, many minor and trace elements absent from the nominal formulations were seen, including K, Ti, Mn, Fe, Ni, Cu, Zn, Ga, Ag, Cd, Hf, and As/Pb. Such impurities may come from rough materials and preparative technologies. The impurities in Romanian composites are comparable to those in some commercial biomaterials but higher than in other ones. Thus PIXE analysis of mineral elements in Romanian composites, even qualitative, appears useful for quality control and improvement. (authors)

  11. Depression, anxiety, and stress among undergraduate dental students in Hyderabad City, Telangana, India: A cross-sectional study

    Directory of Open Access Journals (Sweden)

    Ambati Sravani

    2018-01-01

    Full Text Available Introduction: Increased levels of psychological disturbances such as depression, anxiety, and stress (DAS among dental students affect the way these students take care of patients. Aim: The aim of this study is to assess DAS among undergraduate dental students in Hyderabad city, Telangana, India. Materials and Methods: A short version of depression, anxiety, and stress scale was distributed to undergraduate dental students in four dental colleges. Comparison among the variables was done using ANOVA and Independent t-test. Results: The study group comprised 200 (23.7% males and 645 (76.3% females. The overall mean DAS score and its dimensions were not significant based on gender. Married students showed significantly more DAS compared to unmarried (P < 0.05. When the year of study was considered for all colleges together, the overall mean DAS score and its individual dimensions score were significantly high among III year students followed by IV, I, and II years (P < 0.05. Conclusion: Clinical years were more stressful than the nonclinical years. This suggests a need for special attention to the structure of the clinical program, particularly at the point of transition from the preclinical to the clinical phase.

  12. Analytical methods for the measurement of polymerization kinetics and stresses of dental resin-based composites: A review

    Directory of Open Access Journals (Sweden)

    Mehrsima Ghavami-Lahiji

    2017-01-01

    Full Text Available Resin-based composites are commonly used restorative materials in dentistry. Such tooth-colored restorations can adhere to the dental tissues. One drawback is that the polymerization shrinkage and induced stresses during the curing procedure is an inherent property of resin composite materials that might impair their performance. This review focuses on the significant developments of laboratory tools in the measurement of polymerization shrinkage and stresses of dental resin-based materials during polymerization. An electronic search of publications from January 1977 to July 2016 was made using ScienceDirect, PubMed, Medline, and Google Scholar databases. The search included only English-language articles. Only studies that performed laboratory methods to evaluate the amount of the polymerization shrinkage and/or stresses of dental resin-based materials during polymerization were selected. The results indicated that various techniques have been introduced with different mechanical/physical bases. Besides, there are factors that may contribute the differences between the various methods in measuring the amount of shrinkages and stresses of resin composites. The search for an ideal and standard apparatus for measuring shrinkage stress and volumetric polymerization shrinkage of resin-based materials in dentistry is still required. Researchers and clinicians must be aware of differences between analytical methods to make proper interpretation and indications of each technique relevant to a clinical situation.

  13. Proteomic analysis of osteogenic differentiation of dental follicle precursor cells

    DEFF Research Database (Denmark)

    Morsczeck, Christian; Petersen, Jørgen; Völlner, Florian

    2009-01-01

    of differentiation. In the present study we applied 2-DE combined with capillary-LC-MS/MS analysis to profile differentially regulated proteins upon differentiation of dental follicle precursor cells (DFPCs). Out of 115 differentially regulated proteins, glutamine synthetase, lysosomal proteinase cathepsin B....... The bioinformatic analyses suggest that proteins associated with cell cycle progression and protein metabolism were down-regulated and proteins involved in catabolism, cell motility and biological quality were up-regulated. These results display the general physiological state of DFPCs before and after osteogenic...... proteins, plastin 3 T-isoform, beta-actin, superoxide dismutases, and transgelin were found to be highly up-regulated, whereas cofilin-1, pro-alpha 1 collagen, destrin, prolyl 4-hydrolase and dihydrolipoamide dehydrogenase were found to be highly down-regulated. The group of up-regulated proteins...

  14. Pneumoconiosis and respiratory problems in dental laboratory technicians: Analysis of 893 dental technicians

    Directory of Open Access Journals (Sweden)

    Dilek Ergün

    2014-10-01

    Full Text Available Objectives: To explore the rate of pneumoconiosis in dental technicians (DTP and to evaluate the risk factors. Material and Methods: Data of 893 dental technicians, who were admitted to our hospital in the period January 2007–May 2012, from 170 dental laboratories were retrospectively examined. Demographic data, respiratory symptoms, smoking status, work duration, working fields, exposure to sandblasting, physical examination findings, chest radiographs, pulmonary function tests and high-resolution computed tomography results were evaluated. Results: Dental technicians’ pneumoconiosis rate was 10.1% among 893 cases. The disease was more common among males and in those exposed to sandblasting who had 77-fold higher risk of DTP. The highest profusion subcategory was 3/+ (according to the International Labour Organization (ILO 2011 standards and the large opacity rate was 13.3%. Conclusions: To the best of our knowledge, it was the largest DTP case series (N = 893/90 in the literature in English. Health screenings should be performed regularly for the early diagnosis of pneumoconiosis, which is an important occupational disease for dental technicians.

  15. Advanced Techniques of Stress Analysis

    Directory of Open Access Journals (Sweden)

    Simion TATARU

    2013-12-01

    Full Text Available This article aims to check the stress analysis technique based on 3D models also making a comparison with the traditional technique which utilizes a model built directly into the stress analysis program. This comparison of the two methods will be made with reference to the rear fuselage of IAR-99 aircraft, structure with a high degree of complexity which allows a meaningful evaluation of both approaches. Three updated databases are envisaged: the database having the idealized model obtained using ANSYS and working directly on documentation, without automatic generation of nodes and elements (with few exceptions, the rear fuselage database (performed at this stage obtained with Pro/ ENGINEER and the one obtained by using ANSYS with the second database. Then, each of the three databases will be used according to arising necessities.The main objective is to develop the parameterized model of the rear fuselage using the computer aided design software Pro/ ENGINEER. A review of research regarding the use of virtual reality with the interactive analysis performed by the finite element method is made to show the state- of- the-art achieved in this field.

  16. Basic emotions evoked by eugenol odor differ according to the dental experience. A neurovegetative analysis.

    Science.gov (United States)

    Robin, O; Alaoui-Ismaïli, O; Dittmar, A; Vernet-Maury, E

    1999-06-01

    Subjective individual experiences seem to indicate that odors may form strong connections with memories, especially those charged with emotional significance. In the dental field, this could be the case with the odorant eugenol, responsible for the typical clinging odor impregnating the dental office. The odor of eugenol could evoke memories of unpleasant dental experiences and, therefore, negative feelings such as anxiety and fear, since eugenates (cements containing eugenol) are used in potentially painful restorative dentistry. This hypothesis was tested by evaluating the emotional impact of the odor of eugenol through autonomic nervous system (ANS) analysis. The simultaneous variations of six ANS parameters (two electrodermal, two thermovascular and two cardiorespiratory), induced by the inhalation of this odorant, were recorded on volunteer subjects. Vanillin (a pleasant odorant) and propionic acid (an unpleasant one) served as controls. After the experiment, subjects were asked to rate the pleasantness versus unpleasantness of each odorant on an 11-point hedonic scale. The patterns of autonomic responses, obtained for each odorant and each subject, were transcribed into one of the six basic emotions defined by Ekman et al. (happiness, surprise, sadness, fear, anger and disgust). Results were compared between two groups of subjects divided according to their dental experience (fearful and non-fearful dental care subjects) and showed significant differences only for eugenol. This odorant was rated as pleasant by non-fearful dental subjects but unpleasant by fearful dental subjects. The evoked autonomic responses were mainly associated with positive basic emotions (happiness and surprise) in non-fearful dental subjects and with negative basic emotions (fear, anger, disgust) in fearful dental subjects. These results suggest that eugenol can be responsible for different emotional states depending on the subjects' dental experience, which seems to confirm the

  17. Practical stress analysis in engineering design

    CERN Document Server

    Huston, Ronald

    2008-01-01

    Presents the application of engineering design and analysis based on the approach of understanding the physical characteristics of a given problem and then modeling the important aspects of the physical system. This book covers such topics as contact stress analysis, singularity functions, gear stresses, fasteners, shafts, and shaft stresses.

  18. Rotors stress analysis and design

    CERN Document Server

    Vullo, Vincenzo

    2013-01-01

    Stress and strain analysis of rotors subjected to surface and body loads, as well as to thermal loads deriving from temperature variation along the radius, constitutes a classic subject of machine design. Nevertheless attention is limited to rotor profiles for which governing equations are solvable in closed form. Furthermore very few actual engineering issues may relate to structures for which stress and strain analysis in the linear elastic field and, even more, under non-linear conditions (i.e. plastic or viscoelastic conditions) produces equations to be solved in closed form. Moreover, when a product is still in its design stage, an analytical formulation with closed-form solution is of course simpler and more versatile than numerical methods, and it allows to quickly define a general configuration, which may then be fine-tuned using such numerical methods. In this view, all subjects are based on analytical-methodological approach, and some new solutions in closed form are presented. The analytical formul...

  19. To reduce the maximum stress and the stress shielding effect around a dental implant-bone interface using radial functionally graded biomaterials.

    Science.gov (United States)

    Asgharzadeh Shirazi, H; Ayatollahi, M R; Asnafi, A

    2017-05-01

    In a dental implant system, the value of stress and its distribution plays a pivotal role on the strength, durability and life of the implant-bone system. A typical implant consists of a Titanium core and a thin layer of biocompatible material such as the hydroxyapatite. This coating has a wide range of clinical applications in orthopedics and dentistry due to its biocompatibility and bioactivity characteristics. Low bonding strength and sudden variation of mechanical properties between the coating and the metallic layers are the main disadvantages of such common implants. To overcome these problems, a radial distributed functionally graded biomaterial (FGBM) was proposed in this paper and the effect of material property on the stress distribution around the dental implant-bone interface was studied. A three-dimensional finite element simulation was used to illustrate how the use of radial FGBM dental implant can reduce the maximum von Mises stress and, also the stress shielding effect in both the cortical and cancellous bones. The results, of course, give anybody an idea about optimized behaviors that can be achieved using such materials. The finite element solver was validated by familiar methods and the results were compared to previous works in the literature.

  20. A birth cohort analysis of dental contact among elderly Americans.

    Science.gov (United States)

    Wolinsky, F D; Arnold, C L

    1989-01-01

    We applied standard cohort and multiple regression techniques to data on the dental utilization rates of 129,191 elderly individuals taken from the 1972, 1973, 1976, 1977, 1980, and 1981 Health Interview Surveys. The results indicate that the marked variation in dental contact rates is a reflection of cohort succession, and not a function of aging per se. Older cohorts having lower dental contact rates are being replaced by younger cohorts having higher dental contact rates. The dental contact rates of the individual birth cohorts themselves are quite stable over time. The results also indicate that economic barriers (especially liquid assets) have become more important than ever before, especially for the oldest-old. These findings have important implications for public policy about the oral health and health care of elderly Americans. PMID:2783297

  1. Baring the teeth. [Dental caries and the analysis of trace elements in dental tissues

    Energy Technology Data Exchange (ETDEWEB)

    Cleaton-Jones, P [University of the Witwatersrand, Johannesburg (South Africa). Dental Research Unit; Retief, H [Alabama Univ., Birmingham (USA); Turkstra, J [Fort Hare Univ. (South Africa). Dept. of Chemistry

    1979-07-01

    To determine whether trace elements other than fluorine play a role in the varying prevalences of dental caries in different South African population groups, neutron activation techniques have been devised to establish the concentrations of trace elements in tooth enamel and dentine.

  2. Measuring the efficiency of dental departments in medical centers: a nonparametric analysis approach.

    Science.gov (United States)

    Wang, Su-Chen; Tsai, Chi-Cheng; Huang, Shun-Te; Hong, Yu-Jue

    2002-12-01

    Data envelopment analysis (DEA), a cross-sectional study design based on secondary data analysis, was used to evaluate the relative operational efficiency of 16 dental departments in medical centers in Taiwan in 1999. The results indicated that 68.7% of all dental departments in medical centers had poor performance in terms of overall efficiency and scale efficiency. All relatively efficient dental departments were in private medical centers. Half of these dental departments were unable to fully utilize available medical resources. 75.0% of public medical centers did not take full advantage of medical resources at their disposal. In the returns to scale, 56.3% of dental departments in medical centers exhibited increasing returns to scale, due to the insufficient scale influencing overall hospital operational efficiency. Public medical centers accounted for 77.8% of the institutions affected. The scale of dental departments in private medical centers was more appropriate than those in public medical centers. In the sensitivity analysis, the numbers of residents, interns, and published papers were used to assess teaching and research. Greater emphasis on teaching and research in medical centers has a large effect on the relative inefficiency of hospital operation. Dental departments in private medical centers had a higher mean overall efficiency score than those in public medical centers, and the overall efficiency of dental departments in non-university hospitals was greater than those in university hospitals. There was no information to evaluate the long-term efficiency of each dental department in all hospitals. A different combination of input and output variables, using common multipliers for efficiency value measurements in DEA, may help establish different pioneering dental departments in hospitals.

  3. Reduced dental calcium expression and dental mass in chronic sleep deprived rats: Combined EDS, TOF-SIMS, and micro-CT analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, Yi-Jie [Department of Orthopedics, Taipei Medical University Hospital, Taipei 110, Taiwan (China); Huang, Yung-Kai [School of Oral Hygiene, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Chou, Hsiu-Chu; Pai, Man-Hui; Lee, Ai-Wei [Department of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Mai, Fu-Der [Department of Biochemistry and Molecular Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Chang, Hung-Ming, E-mail: taiwanzoo@gmail.com [Department of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan (China)

    2015-08-01

    Highlights: • The growth of teeth is closely regulated by the circadian rhythmicity. • Sleep deprivation significantly disrupts the circadian regulation. • Sleep deprivation reduces the dental calcium level and impairs dental intensity. • This study highlights for the first time that sleep is essential for dental structure. • Establishing satisfactory sleep behavior may be a helpful strategy to prevent dental disability. - Abstract: Teeth are the hardest tissue in the body. The growth of teeth is closely regulated by circadian rhythmicity. Considering that sleep deprivation (SD) is a severe condition that disrupts normal circadian rhythmicity, this study was conducted to determine whether calcium expression (the major element participating in teeth constitution), and dental mass would be significantly impaired following SD. Adolescent rats subjected to 3 weeks of SD were processed for energy dispersive spectrum (EDS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and micro-computed tomography (micro-CT) analyses. The EDS and TOF-SIMS results indicated that high calcium intensity was detected in both the upper and lower incisors of untreated rats. Micro-CT analysis corresponded closely with spectral data in which an enhanced dental mass was calculated in intact animals. However, following SD, both calcium expression and the dental mass were remarkably decreased to nearly half those of the untreated values. Because SD plays a detrimental role in impairing dental structure, establishing satisfactory sleep behavior would therefore serve as a crucial strategy for preventing or improving prevalent dental dysfunctions.

  4. Reduced dental calcium expression and dental mass in chronic sleep deprived rats: Combined EDS, TOF-SIMS, and micro-CT analysis

    International Nuclear Information System (INIS)

    Kuo, Yi-Jie; Huang, Yung-Kai; Chou, Hsiu-Chu; Pai, Man-Hui; Lee, Ai-Wei; Mai, Fu-Der; Chang, Hung-Ming

    2015-01-01

    Highlights: • The growth of teeth is closely regulated by the circadian rhythmicity. • Sleep deprivation significantly disrupts the circadian regulation. • Sleep deprivation reduces the dental calcium level and impairs dental intensity. • This study highlights for the first time that sleep is essential for dental structure. • Establishing satisfactory sleep behavior may be a helpful strategy to prevent dental disability. - Abstract: Teeth are the hardest tissue in the body. The growth of teeth is closely regulated by circadian rhythmicity. Considering that sleep deprivation (SD) is a severe condition that disrupts normal circadian rhythmicity, this study was conducted to determine whether calcium expression (the major element participating in teeth constitution), and dental mass would be significantly impaired following SD. Adolescent rats subjected to 3 weeks of SD were processed for energy dispersive spectrum (EDS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and micro-computed tomography (micro-CT) analyses. The EDS and TOF-SIMS results indicated that high calcium intensity was detected in both the upper and lower incisors of untreated rats. Micro-CT analysis corresponded closely with spectral data in which an enhanced dental mass was calculated in intact animals. However, following SD, both calcium expression and the dental mass were remarkably decreased to nearly half those of the untreated values. Because SD plays a detrimental role in impairing dental structure, establishing satisfactory sleep behavior would therefore serve as a crucial strategy for preventing or improving prevalent dental dysfunctions

  5. Influence of the shape of the layers in photo-cured dental restorations on the shrinkage stress peaks-FEM study.

    Science.gov (United States)

    Kowalczyk, Piotr

    2009-12-01

    The aim of the paper is to analyse an influence of the shape of the layers in photo-cured dental restorations of Class I on distribution of shrinkage stresses along the tooth-restoration interface. The study is a continuation of the previous considerations (Kowalczyk and Gambin (2008) [1]), where techniques, which reduce stress concentration at the top of the tooth-restoration interface, were considered. The analysis leads to proposition of new layer forming techniques, which diminish the stress peaks at the interface and prevent the crack propagation process. To find the stress distributions in the dental restoration layers and the tooth tissues the finite element method implemented in the ABAQUS (Simulia, Providence, USA) software is used. For Class I restoration of the premolar tooth, the axisymmetrical model is assumed. The restoration is made of four layers of a photo-cured composite. Between the tooth tissues and the restoration, a layer of bonding agent 0.01mm thick is placed and modeled by FEM with help of the cohesive elements. The assumed model takes into account an influence of changes of elastic properties and viscous effects. For each case of the restoration layers system, the Huber-Mises stresses are analysed. The investigations show that the stresses near the restoration-tooth tissue interface are reduced due to viscous flow of the cured material and due to existence of a thin layer of the bonding agent. However, the stress distribution both, in the restoration and in the tooth tissues, is strongly dependent on a shape of the filling layers. Numerical simulations disclose that stress peaks are located at the top corners of each layer. The top corners of the last layer are the places where microleakage may occur. Stress concentrations at the corners of the preceding layers may lead to a growth of uprising crack. It will be shown that the flat layers in the restoration create relatively high values of the stress peaks. The rounded layers, with shapes

  6. Residual stress analysis in thick uranium films

    International Nuclear Information System (INIS)

    Hodge, A.M.; Foreman, R.J.; Gallegos, G.F.

    2005-01-01

    Residual stress analysis was performed on thick, 1-25 μm, depleted uranium (DU) films deposited on an Al substrate by magnetron sputtering. Two distinct characterization techniques were used to measure substrate curvature before and after deposition. Stress evaluation was performed using the Benabdi/Roche equation, which is based on beam theory of a bi-layer material. The residual stress evolution was studied as a function of coating thickness and applied negative bias voltage (0, -200, -300 V). The stresses developed were always compressive; however, increasing the coating thickness and applying a bias voltage presented a trend towards more tensile stresses and thus an overall reduction of residual stresses

  7. Factors associated with unmet dental care needs in Canadian immigrants: an analysis of the longitudinal survey of immigrants to Canada

    OpenAIRE

    Calvasina, Paola; Muntaner, Carles; Quiñonez, Carlos

    2014-01-01

    Background Immigrants are often considered to have poorer oral health than native born-populations. One possible explanation for immigrants’ poor oral health is lack of access to dental care. There is very little information on Canadian immigrants’ access to dental care, and unmet dental care needs. This study examines predictors of unmet dental care needs among a sample of adult immigrants to Canada over a three-point-five-year post-migration period. Methods A secondary data analysis was con...

  8. Mechanical design, analysis, and laboratory testing of a dental implant with axial flexibility similar to natural tooth with periodontal ligament.

    Science.gov (United States)

    Pektaş, Ömer; Tönük, Ergin

    2014-11-01

    At the interface between the jawbone and the roots of natural teeth, a thin, elastic, shock-absorbing tissue, called the periodontal ligament, forms a cushion which provides certain flexibility under mechanical loading. The dental restorations supported by implants, however, involve comparatively rigid connections to the jawbone. This causes overloading of the implant while bearing functional loading together with neighboring natural teeth, which leads to high stresses within the implant system and in the jawbone. A dental implant, with resilient components in the upper structure (abutment) in order to mimic the mechanical behavior of the periodontal ligament in the axial direction, was designed, analyzed in silico, and produced for mechanical testing. The aims of the design were avoiding high levels of stress, loosening of the abutment connection screw, and soft tissue irritations. The finite element analysis of the designed implant revealed that the elastic abutment yielded a similar axial mobility with the natural tooth while keeping stress in the implant at safe levels. The in vitro mechanical testing of the prototype resulted in similar axial mobility predicted by the analysis and as that of a typical natural tooth. The abutment screw did not loosen under repeated loading and there was no static or fatigue failure. © IMechE 2014.

  9. Automated Dental Epidemiology System. II. Systems Analysis and Functional Design,

    Science.gov (United States)

    1983-08-01

    involvement or debilitating soft tissue pathology (e.g., pericoronitis or periodontal abscess ). Therefore it is desired that urgently needed treatment...through the naval population. Developing this kind of information requires extensive use of dental epidemiology. The incidence of caries and periodontal ...Navy Dental Corps efforts toward reducing the incidence and detrimental effects of caries and periodontal disease in the field and afloat. In this

  10. Stress analysis of shear/compression test

    International Nuclear Information System (INIS)

    Nishijima, S.; Okada, T.; Ueno, S.

    1997-01-01

    Stress analysis has been made on the glass fiber reinforced plastics (GFRP) subjected to the combined shear and compression stresses by means of finite element method. The two types of experimental set up were analyzed, that is parallel and series method where the specimen were compressed by tilted jigs which enable to apply the combined stresses, to the specimen. Modified Tsai-Hill criterion was employed to judge the failure under the combined stresses that is the shear strength under the compressive stress. The different failure envelopes were obtained between the two set ups. In the parallel system the shear strength once increased with compressive stress then decreased. On the contrary in the series system the shear strength decreased monotonicly with compressive stress. The difference is caused by the different stress distribution due to the different constraint conditions. The basic parameters which control the failure under the combined stresses will be discussed

  11. The interpersonal work of dental conscious sedation: A qualitative analysis.

    Science.gov (United States)

    Woolley, Stephen M; Chadwick, Barbara; Pugsley, Lesley

    2017-08-01

    Whilst there is a considerable body of literature examining the pharmacology of conscious sedation, the social tasks required to successfully provide conscious sedation have not been reported. This paper discusses data regarding the interpersonal work integral to effective conscious sedation provision, from a larger qualitative study exploring how patients and clinicians engage with secondary care conscious sedation provided within the UK. Semi-structured interviews were conducted with 13 conscious sedation providers and nine patients within UK-based secondary care sedation settings. Digital audio-recordings were transcribed verbatim and subsequently analysed using a constant comparative method within NVivo Data Analysis Software. Four main themes of interpersonal work were reported by participants: displaying care, containing emotions, demonstrating competence and maximizing the effect. This study shows that performing conscious sedation requires more than technical delivery, and involves the projection of attributes in a literal "performance." The importance of managing outward emotional appearance reflects previous dental research. The need to manage outward appearance, and the emotional impact this has, is of relevance to all clinicians. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  12. Parents' online discussions about children's dental caries: A critical content analysis.

    Science.gov (United States)

    Milne, Avery; Weijs, Cynthia A; Haines-Saah, Rebecca J; McLaren, Lindsay

    2017-09-14

    Through an analysis of postings to an online parenting forum, we aimed to explore the many ways in which parents orient to (i.e., take up, challenge, re-articulate) information about child dental health in the context of their online interactions. Our analysis is anchored in Nettleton's theoretical work on dental authority and power, which we apply in a digital context. We examined discussion threads from the public online forums on BabyCenter Canada. We identified relevant threads using the site search function and keywords related to dental health, with a focus on dental caries (tooth decay), related care behaviours (e.g., toothbrushing), and the controversial issue of fluoride. Following descriptive content coding, we applied a critical lens to unpack themes related to expert knowledge, gender and parenting online cultures. We analyzed 479 relevant threads. Our findings focus on two central themes: the tension between parents' views and those of dental health professionals; and, the gendered, cultural roles and expectations that position mothers as primarily responsible for the care of children's dental health. Though these themes are not new, our findings show that they persist in the digital context where social divisions (e.g., expert/non-expert) may be blurred. Our analysis of online discussions provides an opportunity to think critically about ways in which parents engage with public health, in digital contexts. Although some mothers express disconnect when communicating with dental professionals, they are very engaged and concerned with dental health issues for their children. A challenge for dental public health is to find ways to shift perspective towards recognizing that the target population is empowered and already engaged in discussions of research evidence and clinical encounters on their own terms, facilitated by an online context.

  13. Thermotransduction and heat stress in dental structures during orthodontic debonding : Effectiveness of various cooling strategies.

    Science.gov (United States)

    Kley, Philipp; Frentzen, Matthias; Küpper, Katharina; Braun, Andreas; Kecsmar, Susann; Jäger, Andreas; Wolf, Michael

    2016-05-01

    Recent studies have indicated possible thermal damage to pulpal tissue during orthodontic debonding. This study aimed to analyze the thermal loads acting upon dental structures and their transfer to the pulp during orthodontic debonding. Specific goals were to analyze temperature changes in local dental tissues, thermotransduction to the pulp cavity, and the effectiveness of common cooling strategies and of simulated intrapulpal circulation. Metal brackets were bonded to five extracted human molars and subsequently removed. While a carbide bur was applied to debond the residual composite from the tooth surface, various cooling strategies (no/air/water cooling) were employed with or without simulated intrapulpal circulation, accompanied by temperature measurements with a thermographic infrared camera on the enamel surface and with measuring probes in the pulp cavity. Appropriate evaluation software was used to calculate the enamel-to-pulp temperature gradients and for statistical analysis. Significant differences in temperature rise and heat development over time, both on the enamel surfaces and in the pulp cavities were found. The mean temperature rises associated with no/air/water cooling were 90.7/46.6/9.2 °C on the enamel surface versus 9/8/4.6 °C inside the pulp. However, thermotransduction from enamel to pulp remained below 10 % of the surface measurements in all groups. Simulated intrapulpal microcirculation was found to significantly reduce intrapulpal temperature levels. During debonding of residual bracket adhesives, provided that a carbide bur is properly used, our data indicate a low risk of reaching critical intrapulpal temperatures even in the absence of dedicated cooling and no risk if the instrumentation is accompanied by air or water cooling.

  14. Dosimetric analysis of SMD phototransistor in dental phantom of different geometries

    International Nuclear Information System (INIS)

    Belinato, W.; Magalhaes, C. M. S.; Souza, D. N.; Santos, L. A. P.

    2009-10-01

    A commercial surface mount device (SMD) phototransistor, OP520, was inserted in two dental phantoms for dosimetric analysis. The irradiations were accomplished in a dental x-ray equipment of 80 kV using different exposition times. A standard ionization chamber was irradiated at the same conditions and the air kerma measured with it was compared with the electrical charge evaluated by the phototransistor. The results showed satisfactory correspondence among the detectors readings. Moreover, the phototransistor showed up quite sensitively for dental applications, allowing verifying the variations for the different phantoms configurations. (Author)

  15. Association between developmental defects of enamel and dental caries: A systematic review and meta-analysis.

    Science.gov (United States)

    Vargas-Ferreira, F; Salas, M M S; Nascimento, G G; Tarquinio, S B C; Faggion, C M; Peres, M A; Thomson, W M; Demarco, F F

    2015-06-01

    Dental caries is the main problem oral health and it is not well established in the literature if the enamel defects are a risk factor for its development. Studies have reported a potential association between developmental defects enamel (DDE) and dental caries occurrence. We investigated the association between DDE and caries in permanent dentition of children and teenagers. A systematic review was carried out using four databases (Pubmed, Web of Science, Embase, and Science Direct), which were searched from their earliest records until December 31, 2014. Population-based studies assessing differences in dental caries experience according to the presence of enamel defects (and their types) were included. PRISMA guidelines for reporting systematic reviews were followed. Meta-analysis was performed to assess the pooled effect, and meta-regression was carried out to identify heterogeneity sources. From the 2558 initially identified papers, nine studies fulfilled all inclusion criteria after checking the titles, abstracts, references, and complete reading. Seven of them were included in the meta-analysis with random model. A positive association between enamel defects and dental caries was identified; meta-analysis showed that individuals with DDE had higher pooled odds of having dental caries experience [OR 2.21 (95% CI 1.3; 3.54)]. Meta-regression analysis demonstrated that adjustment for sociodemographic factors, countries' socioeconomic status, and bias (quality of studies) explained the high heterogeneity observed. A higher chance of dental caries should be expected among individuals with enamel defects. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Stress analysis in FRP composites

    Directory of Open Access Journals (Sweden)

    Nitin Jauhari

    2016-09-01

    Full Text Available A composite material, in mechanics sense, is a structure with the ingredients as element transferring forces to adjacent members. The issue of defects and their effect on the mechanical properties of composites is of great concern among high end users. Experimental investigation of failure modes of composite materials requires correlating the fundamentals of composite materials, their mechanical properties as well as their failure characteristics in the presence of defects. In this paper, three formats of defects of hole (single, double and quadruple as a discontinuity were incorporated along with tensile testing. Unique failure modes of these specimens provided overview regarding mechanical behaviour of composite materials containing defects. Certain correlations were observed between defects and resulting properties. Results are in agreement with general behaviour of FRP composite laminates and it can be concluded that for low deformation in composite laminates, number of layers must be increased, which at the same time results in increase of von-Mises stress. Fibres are the main constituents which are responsible for strength of a composite laminate and they along with fibre orientation, play an important role on its load bearing capacity. It can be inferred based on the analysis that cross-ply configuration [0°/90°] has good load bearing capacity as well as least deflection emphasizing more strength.

  17. Articulated dental cast analysis of asymptomatic and symptomatic populations

    Science.gov (United States)

    Cordray, Frank E

    2016-01-01

    Dental instrumentation has long provided insight into the mechanism of musculo-skeletal function of the gnathic system. While large population studies associate dental arch displacement (DAD), especially laterally, with symptoms, mandibular condyle displacement (CD) resulting from DAD has not been targeted as possibly etiologic in the production of common muscle contraction headache (CMCH) and temporo-mandibular dysfunction (TMD). The objective was to evaluate the three-dimensional nature of DAD and CD between the seated condylar position (SCP) and the intercuspal position (ICP) and to compare results derived from large deprogrammed asymptomatic and symptomatic populations. A total of 1 192 sets of dental casts collected from asymptomatic and symptomatic populations were articulated in the SCP. The initial occlusal contact, DAD, and condylar displacement were evaluated for frequency, direction, and magnitude of displacement between the SCP and ICP. The data revealed significant displacement between the SCP and ICP of the condyles (displaced most frequently inferior (down) and posterior (distal)) and substantially increased frequency and magnitude of displacement of the dental arches (with posterior premature occlusal contacts, increased overjet, decreased overbite, midline differences, and occlusal classification changes) in symptomatic subjects. These discrepancies were statistically significant and clinically significant. The data support the concept of increased DAD and CD with dysfunction. Transverse condylar displacement, commonly presenting with dental cross bite, may be associated with CMCH and TMD. Displacement of the mandibular condyle may be an etiologic factor in CMCH and dysfunction of the temporo-mandibular joint. PMID:27357324

  18. Nuclear class 1 piping stress analysis

    International Nuclear Information System (INIS)

    Lucas, J.C.R.; Maneschy, J.E.; Mariano, L.A.; Tamura, M.

    1981-01-01

    A nuclear class 1 piping stress analysis, according to the ASME code, is presented. The TRHEAT computer code has been used to determine the piping wall thermal gradient. The Nupipe computer code was employed for the piping stress analysis. Computer results were compared with the allowable criteria from the ASME code. (Author) [pt

  19. Mini dental implants retaining mandibular overdentures: A dental practice-based retrospective analysis.

    Science.gov (United States)

    Schwindling, Franz Sebastian; Schwindling, Franz-Peter

    2016-07-01

    The purpose of this study was to assess the survival of mini dental implants (MDI) and to measure prosthetic maintenance needs in a dental practice-based setting. Patients with mandibular removable dentures were provided with MDI to improve denture retention. Complications and maintenance were analyzed by use of patient records and evaluated with Kaplan-Meier curves and the log rank test at a significance level of 0.05. Ninety-nine MDI were placed in 25 patients (mean age: 72 years). Two MDI fractured during placement and eight implants failed during the first weeks. No more implants were lost for up to seven years, resulting in 92% survival. Implant survival differed significantly depending on whether the maxilla was provided with complete dentures (94.9%) or with partial dentures (81%). All prostheses were in use at the time of data extraction. Denture base fractures were observed in six cases, an incidence of fractures of 24%. Some minor intervention was necessary: one resin tooth fractured, retention rings were changed in five cases, and repeated relining was required for 16% of the dentures. After mid-term observation, survival of MDI was good. However, the incidence of denture base fractures and of minor prosthetic complications should not be under-estimated. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  20. Potentiometric stripping analysis of lead and cadmium leaching from dental prosthetic materials and teeth

    Directory of Open Access Journals (Sweden)

    GORAN M. NIKOLIC

    2004-07-01

    Full Text Available Potentiometric stipping analysis (PSA was applied for the determination of lead and cadmium leaching from dental prosthetic materials and teeth. The soluble lead content in finished dental implants was found to be much lower than that of the individual components used for their preparation. Cadmium was not detected in dental implants and materials under the defined conditions. The soluble lead and cadmium content of teeth was slightly lower than the lead and cadmium content in whole teeth (w/w reported by other researchers, except in the case of a tooth with removed amalgam filling. The results of this work suggest that PSA may be a good method for lead and cadmium leaching studies for investigation of the biocompatibility of dental prosthetic materials.

  1. Rural and remote dental services shortages: filling the gaps through geo-spatial analysis evidence-based targeting.

    Science.gov (United States)

    Shiika, Yulia; Kruger, Estie; Tennant, Marc

    Australia has a significant mal-distribution of its limited dental workforce. Outside the major capital cities, the distribution of accessible dental care is at best patchy. This study applied geo-spatial analysis technology to locate gaps in dental service accessibility for rural and remote dwelling Australians, in order to test the hypothesis that there are a few key location points in Australia where further dental services could make a significant contribution to ameliorating the immediate shortage crisis. A total of 2,086 dental practices were located in country areas, covering a combined catchment area of 1.84 million square kilometers, based on 50 km catchment zones around each clinic. Geo-spatial analysis technology was used to identify gaps in the accessibility of dental services for rural and remote dwelling Australians. An extraction of data was obtained to analyse the integrated geographically-aligned database. Results: Resolution of the lack of dental practices for 74 townships (of greater than 500 residents) across Australia could potentially address access for 104,000 people. An examination of the socio-economic mix found that the majority of the dental practices (84%) are located in areas classified as less disadvantaged. Output from the study provided a cohesive national map that has identified locations that could have health improvement via the targeting of dental services to that location. The study identified potential location sites for dental clinics, to address the current inequity in accessing dental services in rural and remote Australia.

  2. Analysis of physiological responses associated with emotional changes induced by viewing video images of dental treatments.

    Science.gov (United States)

    Sekiya, Taki; Miwa, Zenzo; Tsuchihashi, Natsumi; Uehara, Naoko; Sugimoto, Kumiko

    2015-03-30

    Since the understanding of emotional changes induced by dental treatments is important for dentists to provide a safe and comfortable dental treatment, we analyzed physiological responses during watching video images of dental treatments to search for the appropriate objective indices reflecting emotional changes. Fifteen healthy young adult subjects voluntarily participated in the present study. Electrocardiogram (ECG), electroencephalogram (EEG) and corrugator muscle electromyogram (EMG) were recorded and changes of them by viewing videos of dental treatments were analyzed. The subjective discomfort level was acquired by Visual Analog Scale method. Analyses of autonomic nervous activities from ECG and four emotional factors (anger/stress, joy/satisfaction, sadness/depression and relaxation) from EEG demonstrated that increases in sympathetic nervous activity reflecting stress increase and decreases in relaxation level were induced by the videos of infiltration anesthesia and cavity excavation, but not intraoral examination. The corrugator muscle activity was increased by all three images regardless of video contents. The subjective discomfort during watching infiltration anesthesia and cavity excavation was higher than intraoral examination, showing that sympathetic activities and relaxation factor of emotion changed in a manner consistent with subjective emotional changes. These results suggest that measurement of autonomic nervous activities estimated from ECG and emotional factors analyzed from EEG is useful for objective evaluation of subjective emotion.

  3. Viscoelastic analysis of a dental metal-ceramic system

    Science.gov (United States)

    Özüpek, Şebnem; Ünlü, Utku Cemal

    2012-11-01

    Porcelain-fused-to-metal (PFM) restorations used in prosthetic dentistry contain thermal stresses which develop during the cooling phase after firing. These thermal stresses coupled with the stresses produced by mechanical loads may be the dominant reasons for failures in clinical situations. For an accurate calculation of these stresses, viscoelastic behavior of ceramics at high temperatures should not be ignored. In this study, the finite element technique is used to evaluate the effect of viscoelasticity on stress distributions of a three-point flexure test specimen, which is the current international standard, ISO 9693, to characterize the interfacial bond strength of metal-ceramic restorative systems. Results indicate that the probability of interfacial debonding due to normal tensile stress is higher than that due to shear stress. This conclusion suggests modification of ISO 9693 bond strength definition from one in terms of the shear stress only to that accounting for both normal and shear stresses.

  4. Fiber optics reflectance spectroscopy (45°x: 45°) for color analysis of dental composite.

    Science.gov (United States)

    Gargano, Marco; Ludwig, Nicola; Federighi, Veronica; Sykes, Ros; Lodi, Giovanni; Sardella, Andrea; Carrassi, Antonio; Varoni, Elena M

    2016-08-01

    To evaluate the application of a fiber optic reflectance spectroscopy (FORS) prototype probe for 45°x: 45° FORS for determining color of dental materials. A portable spectrophotometer with a highly manageable fiber optics co-axial probe was used to apply 45°x: 45° FORS for color matching in restorative dentistry. The color coordinates in CIELAB space of two dental shade guides and of the corresponding photopolymerized composites were collected and compared. The 45°x: 45° FORS with the co-axial probe (test system), the integrating sphere spectroscopy (reference system) and a commercial dental colorimeter (comparator system) were used to collect data and calculate color differences (ΔE and ΔE00). FORS system displayed high repeatability, reproducibility and accuracy. ΔE and ΔE00 values between the shade-guide, each other, and the corresponding composites resulted above the clinically acceptable limit. The 45°x: 45° FORS test system demonstrated suitable in vitro performance for dental composite color evaluation. 45°x: 45° fiber optic reflectance spectroscopy allows reliable color analysis of small surfaces of dental composites, favoring the color matching of material with the closely surrounding dental tissue, and confirming significant color differences between shade guide tabs and photo-polymerized composites.

  5. Dental treatment under general anesthesia for special-needs patients: analysis of the literature.

    Science.gov (United States)

    Mallineni, Sreekanth K; Yiu, Cynthia K Y

    2016-11-01

    The aim of the present review was to identify the studies published on dental treatment under general anesthesia for special-needs patients. A comprehensive search of the reported literature from January 1966 to May 2012 was conducted using PubMed, Medline, and Embase. Keywords used in the search were "dental treatment under general anesthesia", "special-needs patients", "medically-compromised patients", and "children", in various combinations. Studies published only on dental treatment under general anesthesia and in English were included. Only 10 studies were available for final analysis. Age range from 1 to 50 years, and restorative procedures, were most prevalent. Only two studies discussed repeated general anesthesia, with rates of 7.2% and 10.2%. Over time, the provision of general anesthesia for special-needs patients has changed from dental clinics to general hospitals. The demand for dental treatment for special-needs patients under general anesthesia continues to increase. Currently, there are no certain accepted protocols for the provision of dental treatment under general anesthesia. © 2015 Wiley Publishing Asia Pty Ltd.

  6. Coupling image processing and stress analysis for damage identification in a human premolar tooth.

    Science.gov (United States)

    Andreaus, U; Colloca, M; Iacoviello, D

    2011-08-01

    Non-carious cervical lesions are characterized by the loss of dental hard tissue at the cement-enamel junction (CEJ). Exceeding stresses are therefore generated in the cervical region of the tooth that cause disruption of the bonds between the hydroxyapatite crystals, leading to crack formation and eventual loss of enamel and the underlying dentine. Damage identification was performed by image analysis techniques and allowed to quantitatively assess changes in teeth. A computerized two-step procedure was generated and applied to the first left maxillary human premolar. In the first step, dental images were digitally processed by a segmentation method in order to identify the damage. The considered morphological properties were the enamel thickness and total area, the number of fragments in which the enamel is chipped. The information retrieved by the data processing of the section images allowed to orient the stress investigation toward selected portions of the tooth. In the second step, a three-dimensional finite element model based on CT images of both the tooth and the periodontal ligament was employed to compare the changes occurring in the stress distributions in normal occlusion and malocclusion. The stress states were analyzed exclusively in the critical zones designated in the first step. The risk of failure at the CEJ and of crack initiation at the dentin-enamel junction through the quantification of first and third principal stresses, von Mises stress, and normal and tangential stresses, were also estimated. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  7. Lab-Test® 4: Dental caries and bacteriological analysis

    Directory of Open Access Journals (Sweden)

    Francesca Cura

    2012-01-01

    The main factors predisposing the onset of the carious process are: 1 the presence of bacterial species able to lower the pH until critical values of 5.5, 2 the absence of adequate oral hygiene, 3 an inefficient immune response anti-caries, 4 the type of alimentary diet and 5 the structure of the teeth. Among the 200 bacterial species isolated from dental plaque the most pathogenic for dental caries are: Streptococcus mutans, Streptococcus sobrinus, Lactobacillus acidophilus, Actinomices viscusus and Bifidobacterium dentium. Our laboratory (LAB® s.r.l., Codigoro, Ferrara, Italy has developed a test for absolute and relative quantification of the most common oral cariogenic bacteria. The test uses specific primers and probes for the amplification of bacteria genome sequences in Polymerase Chain Reaction Real Time. The results provide a profile of patient infection, helpful for improving the diagnosis and planning of preventive treatment to reduce the bacterial load.

  8. Molecular analysis of the oral microbiota of dental diseases

    OpenAIRE

    Kanasi, Eleni

    2008-01-01

    Traditionally, bacterial culture has been used for bacterial detection, allowing study of living microorganisms. Molecular methods are rapid and allow simultaneous identification of numerous species and uncultivated phylotypes. The objective of this doctoral thesis was to investigate the role of the oral microbiota, including poorly characterized and uncultivated bacteria, in dental caries and periodontitis, by comprehensive molecular, clinical, and statistical methods. The microbiota of 275 ...

  9. Bruxism and Dental Implants: A Meta-Analysis.

    Science.gov (United States)

    Chrcanovic, Bruno Ramos; Albrektsson, Tomas; Wennerberg, Ann

    2015-10-01

    To test the null hypothesis of no difference in the implant failure rates, postoperative infection, and marginal bone loss after the insertion of dental implants in bruxers compared with the insertion in non-bruxers against the alternative hypothesis of a difference. An electronic search was undertaken in June 2014. Eligibility criteria included clinical studies, either randomized or not. Ten publications were included with a total of 760 implants inserted in bruxers (49 failures; 6.45%) and 2989 in non-bruxers (109 failures; 3.65%). Due to lack of information, meta-analyses for the outcomes "postoperative infection" and "marginal bone loss" were not possible. A risk ratio of 2.93 was found (95% confidence interval, 1.48-5.81; P = 0.002). These results cannot suggest that the insertion of dental implants in bruxers affects the implant failure rates due to a limited number of published studies, all characterized by a low level of specificity, and most of them deal with a limited number of cases without a control group. Therefore, the real effect of bruxing habits on the osseointegration and survival of endosteal dental implants is still not well established.

  10. REMIFENTANIL VS FENTANYL DURING DAY CASE DENTAL SURGERY IN PEOPLE WITH SPECIAL NEEDS: A COMPARATIVE, PILOT STUDY OF THEIR EFFECT ON STRESS RESPONSE AND POSTOPERATIVE PAIN.

    Science.gov (United States)

    Sklika, Eirini; Kalimeris, Konstantinos; Perrea, Despina; Stavropoulos, Nikolaos; Kostopanagiotou, Georgia; Matsota, Paraskevi

    2016-06-01

    People with special needs undergoing dental surgery frequently require general anesthesia. We investigated the effect of remifentanil vs fentanyl on stress response and postoperative pain in people with special needs undergoing day-case dental surgery. Forty-six adult patients with cognitive impairment undergoing day-case dental surgery under general anesthesia were allocated to receive intraoperatively either fentanyl 50 μg iv bolus (group F, n = 23) or continuous infusion of remifentanil 0.5-1 μg/kg/min (group R, n = 23). Iintraoperative hemodynamic parameters were recorded and serum inflammatory mediators [tumor necrosis factor-α, substance-P], stress hormons (melatonin, cortisol) and β-endorphin were measured. Postoperative pain was assessed during the first postoperative 12 hours with the Wong-Baker faces pain-rating scale. Demographics were similar in two groups. The two groups did not differ regarding their effects on inflammatory mediators, stress hormons and postoperative pain scores. However, the use of remifentanil prevented intraoperative increases of arterial blood pressure and heart rate. Remifentanil and fentanyl did not affect differently stress and inflammatory hormones during day-case dental surgery, although remifentanil may render intraoperative management of hemodynamic responses easier. Both opioids are equally efficient for postoperative pain management following dental surgery in people with special needs.

  11. A finite element analysis of novel vented dental abutment geometries for cement-retained crown restorations.

    Science.gov (United States)

    Rodriguez, Lucas C; Saba, Juliana N; Meyer, Clark A; Chung, Kwok-Hung; Wadhwani, Chandur; Rodrigues, Danieli C

    2016-11-01

    Recent literature indicates that the long-term success of dental implants is, in part, attributed to how dental crowns are attached to their associated implants. The commonly utilized method for crown attachment - cementation, has been criticized because of recent links between residual cement and peri-implant disease. Residual cement extrusion from crown-abutment margins post-crown seating is a growing concern. This study aimed at (1) identifying key abutment features, which would improve dental cement flow characteristics, and (2) understanding how these features would impact the mechanical stability of the abutment under functional loads. Computational fluid dynamic modeling was used to evaluate cement flow in novel abutment geometries. These models were then evaluated using 3D-printed surrogate models. Finite element analysis also provided an understanding of how the mechanical stability of these abutments was altered after key features were incorporated into the geometry. The findings demonstrated that the key features involved in improved venting of the abutment during crown seating were (1) addition of vents, (2) diameter of the vents, (3) location of the vents, (4) addition of a plastic screw insert, and (5) thickness of the abutment wall. This study culminated in a novel design for a vented abutment consisting of 8 vents located radially around the abutment neck-margin plus a plastic insert to guide the cement during seating and provide retrievability to the abutment system.Venting of the dental abutment has been shown to decrease the risk of undetected residual dental cement post-cement-retained crown seating. This article will utilize a finite element analysis approach toward optimizing dental abutment designs for improved dental cement venting. Features investigated include (1) addition of vents, (2) diameter of vents, (3) location of vents, (4) addition of plastic screw insert, and (5) thickness of abutment wall.

  12. A finite element analysis of novel vented dental abutment geometries for cement‐retained crown restorations

    Science.gov (United States)

    Rodriguez, Lucas C.; Saba, Juliana N.; Meyer, Clark A.; Chung, Kwok‐Hung; Wadhwani, Chandur

    2016-01-01

    Abstract Recent literature indicates that the long‐term success of dental implants is, in part, attributed to how dental crowns are attached to their associated implants. The commonly utilized method for crown attachment – cementation, has been criticized because of recent links between residual cement and peri‐implant disease. Residual cement extrusion from crown‐abutment margins post‐crown seating is a growing concern. This study aimed at (1) identifying key abutment features, which would improve dental cement flow characteristics, and (2) understanding how these features would impact the mechanical stability of the abutment under functional loads. Computational fluid dynamic modeling was used to evaluate cement flow in novel abutment geometries. These models were then evaluated using 3D‐printed surrogate models. Finite element analysis also provided an understanding of how the mechanical stability of these abutments was altered after key features were incorporated into the geometry. The findings demonstrated that the key features involved in improved venting of the abutment during crown seating were (1) addition of vents, (2) diameter of the vents, (3) location of the vents, (4) addition of a plastic screw insert, and (5) thickness of the abutment wall. This study culminated in a novel design for a vented abutment consisting of 8 vents located radially around the abutment neck‐margin plus a plastic insert to guide the cement during seating and provide retrievability to the abutment system.Venting of the dental abutment has been shown to decrease the risk of undetected residual dental cement post‐cement‐retained crown seating. This article will utilize a finite element analysis approach toward optimizing dental abutment designs for improved dental cement venting. Features investigated include (1) addition of vents, (2) diameter of vents, (3) location of vents, (4) addition of plastic screw insert, and (5) thickness of abutment wall. PMID

  13. Protective effect of lycopene on fluoride-induced ameloblasts apoptosis and dental fluorosis through oxidative stress-mediated Caspase pathways.

    Science.gov (United States)

    Li, Weishan; Jiang, Binghua; Cao, Xianglin; Xie, Yongjiang; Huang, Ting

    2017-01-05

    Fluoride is an environmental toxicant and induces dental fluorosis and oxidative stress. Lycopene (LYC) is an effective antioxidant that is reported to attenuate fluoride toxicity. To determine the effects of LYC on sodium fluoride (NaF) -induced teeth and ameloblasts toxicity, rats were treated with NaF (10 mg/kg) and/or LYC (10 mg/kg) by orally administration for 5 weeks; ameloblasts were treated with NaF (5 mM) and/or LYC (2 μM) for 6 h. We found that the concentrations of fluoride, malondialdehyde (MDA) and reactive oxygen species (ROS), gene expressions and activities of Caspase-9 and Caspase-3, and the gene expressions of Bax were significantly decreased, while the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPX), the gene expression of Bcl-2 were significantly increased in the LYC + NaF-treated rats group; concentrations of MDA and ROS, gene expressions and activities of Caspase-9 and Caspase-3, and the gene expression of Bax, and ameloblasts apoptosis rate were significantly decreased, while the activities of SOD and GPX, the gene expression of Bcl-2 were significantly increased in the LYC + NaF-treated ameloblasts group. These results suggest that LYC significantly combated NaF-induced ameloblasts apoptosis and dental fluorosis by attenuation oxidative stress and down-regulation Caspase pathway. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  14. Residual stress concerns in containment analysis

    International Nuclear Information System (INIS)

    Costantini, F.; Kulak, R. F.; Pfeiffer, P. A.

    1997-01-01

    The manufacturing of steel containment vessels starts with the forming of flat plates into curved plates. A steel containment structure is made by welding individual plates together to form the sections that make up the complex shaped vessels. The metal forming and welding process leaves residual stresses in the vessel walls. Generally, the effect of metal forming residual stresses can be reduced or virtually eliminated by thermally stress relieving the vesseL In large containment vessels this may not be practical and thus the residual stresses due to manufacturing may become important. The residual stresses could possibly tiect the response of the vessel to internal pressurization. When the level of residual stresses is significant it will affect the vessel's response, for instance the yielding pressure and possibly the failure pressure. The paper will address the effect of metal forming residual stresses on the response of a generic pressure vessel to internal pressurization. A scoping analysis investigated the effect of residual forming stresses on the response of an internally pressurized vessel. A simple model was developed to gain understanding of the mechanics of the problem. Residual stresses due to the welding process were not considered in this investigation

  15. Microarray analysis of the gene expression profile in triethylene glycol dimethacrylate-treated human dental pulp cells.

    Science.gov (United States)

    Torun, D; Torun, Z Ö; Demirkaya, K; Sarper, M; Elçi, M P; Avcu, F

    2017-11-01

    Triethylene glycol dimethacrylate (TEGDMA) is an important resin monomer commonly used in the structure of dental restorative materials. Recent studies have shown that unpolymerized resin monomers may be released into the oral environment and cause harmful biological effects. We investigated changes in the gene expression profiles of TEGDMA-treated human dental pulp cells (hDPCs) following short- (1-day) and long-term (7-days) exposure. HDPCs were exposed to a noncytotoxic concentration of TEGDMA, and gene expression profiles were evaluated by microarray analysis. The results were confirmed by quantitative reverse-transcriptase PCR (qRT PCR). In total, 1282 and 1319 genes (up- or down-regulated) were differentially expressed compared with control group after the 1- and 7-day incubation periods, respectively. Biological ontology-based analyses revealed that metabolic, cellular, and developmental processes constituted the largest groups of biological functional processes. qRT-PCR analysis on bone morphogenetic protein-2 (BMP-2), BMP-4, secreted protein, acidic, cysteine-rich, collagen type I alpha 1, oxidative stress-induced growth inhibitor 1, MMP3, interleukin-6, and heme oxygenase-1 genes confirmed the changes in expression observed in the microarray analysis. Our results suggest that TEGDMA can change the many functions of hDPCs through large changes in gene expression levels and complex interactions with different signaling pathways.

  16. Waardenburg syndrome type I: Dental phenotypes and genetic analysis of an extended family.

    Science.gov (United States)

    Sólia-Nasser, L; de Aquino, S-N; Paranaíba, L-M R; Gomes, A; Dos-Santos-Neto, P; Coletta, R-D; Cardoso, A-F; Frota, A-C; Martelli-Júnior, H

    2016-05-01

    The aim of this study was to describe the pattern of inheritance and the clinical features in a large family with Waardenburg syndrome type I (WS1), detailing the dental abnormalities and screening for PAX3 mutations. To characterize the pattern of inheritance and clinical features, 29 family members were evaluated by dermatologic, ophthalmologic, otorhinolaryngologic and orofacial examination. Molecular analysis of the PAX3 gene was performed. The pedigree of the family,including the last four generations, was constructed and revealed non-consanguineous marriages. Out of 29 descendants, 16 family members showed features of WS1, with 9 members showing two major criteria indicative of WS1. Five patients showed white forelock and iris hypopigmentation, and four showed dystopia canthorum and iris hypopigmentation. Two patients had hearing loss. Dental abnormalities were identified in three family members, including dental agenesis, conical teeth and taurodontism. Sequencing analysis failed to identify mutations in the PAX3 gene. These results confirm that WS1 was transmitted in this family in an autosomal dominant pattern with variable expressivity and high penetrance. The presence of dental manifestations, especially tooth agenesis and conical teeth which resulted in considerable aesthetic impact on affected individuals was a major clinical feature. This article reveals the presence of well-defined dental changes associated with WS1 and tries to establish a possible association between these two entities showing a new spectrum of WS1.

  17. The evolution of dental journals from 2003 to 2012: a bibliometric analysis.

    Science.gov (United States)

    Jayaratne, Yasas Shri Nalaka; Zwahlen, Roger Arthur

    2015-01-01

    Bibliometrics are a set of methods, which can be used to analyze academic literature quantitatively and its changes over time. The objectives of this study were 1) to evaluate trends related to academic performance of dental journals from 2003 to 2012 using bibliometric indices, and 2) monitor the changes of the five dental journals with the highest and lowest impact factor (IF) published in 2003. Data for the subject category "Dentistry, Oral Surgery & Medicine" was retrieved from the Journal Citation Reports (JCR) published from 2003 to 2012. Linear regressions analysis was used to determine statistical trends over the years with each bibliometric indicator as the dependent variable and the JCR year as the predictor variable. Statistically significant rise in the total number of dental journals, the number of all articles with the steepest rise observed for research articles, the number of citations and the aggregate IF was observed from 2003 to 2012. The analysis of the five top and five bottom-tire dental journals revealed a rise in IF however, with a wide variation in relation to the magnitude of this rise. Although the IF of the top five journals remained relatively constant, the percentile ranks of the four lowest ranking journals in 2003 increased significantly with the sharpest rise being noted for the British Journal of Oral & Maxillofacial Surgery. This study revealed significant growth of dental literature in absolute terms, as well as upward trends for most of the citation-based bibliometric indices from 2003 to 2012.

  18. The evolution of dental journals from 2003 to 2012: a bibliometric analysis.

    Directory of Open Access Journals (Sweden)

    Yasas Shri Nalaka Jayaratne

    Full Text Available Bibliometrics are a set of methods, which can be used to analyze academic literature quantitatively and its changes over time. The objectives of this study were 1 to evaluate trends related to academic performance of dental journals from 2003 to 2012 using bibliometric indices, and 2 monitor the changes of the five dental journals with the highest and lowest impact factor (IF published in 2003. Data for the subject category "Dentistry, Oral Surgery & Medicine" was retrieved from the Journal Citation Reports (JCR published from 2003 to 2012. Linear regressions analysis was used to determine statistical trends over the years with each bibliometric indicator as the dependent variable and the JCR year as the predictor variable. Statistically significant rise in the total number of dental journals, the number of all articles with the steepest rise observed for research articles, the number of citations and the aggregate IF was observed from 2003 to 2012. The analysis of the five top and five bottom-tire dental journals revealed a rise in IF however, with a wide variation in relation to the magnitude of this rise. Although the IF of the top five journals remained relatively constant, the percentile ranks of the four lowest ranking journals in 2003 increased significantly with the sharpest rise being noted for the British Journal of Oral & Maxillofacial Surgery. This study revealed significant growth of dental literature in absolute terms, as well as upward trends for most of the citation-based bibliometric indices from 2003 to 2012.

  19. The Evolution of Dental Journals from 2003 to 2012: A Bibliometric Analysis

    Science.gov (United States)

    Jayaratne, Yasas Shri Nalaka; Zwahlen, Roger Arthur

    2015-01-01

    Bibliometrics are a set of methods, which can be used to analyze academic literature quantitatively and its changes over time. The objectives of this study were 1) to evaluate trends related to academic performance of dental journals from 2003 to 2012 using bibliometric indices, and 2) monitor the changes of the five dental journals with the highest and lowest impact factor (IF) published in 2003. Data for the subject category "Dentistry, Oral Surgery & Medicine" was retrieved from the Journal Citation Reports (JCR) published from 2003 to 2012. Linear regressions analysis was used to determine statistical trends over the years with each bibliometric indicator as the dependent variable and the JCR year as the predictor variable. Statistically significant rise in the total number of dental journals, the number of all articles with the steepest rise observed for research articles, the number of citations and the aggregate IF was observed from 2003 to 2012. The analysis of the five top and five bottom-tire dental journals revealed a rise in IF however, with a wide variation in relation to the magnitude of this rise. Although the IF of the top five journals remained relatively constant, the percentile ranks of the four lowest ranking journals in 2003 increased significantly with the sharpest rise being noted for the British Journal of Oral & Maxillofacial Surgery. This study revealed significant growth of dental literature in absolute terms, as well as upward trends for most of the citation-based bibliometric indices from 2003 to 2012. PMID:25781486

  20. Clinical evaluation of nonsyndromic dental anomalies in Dravidian population: A cluster sample analysis.

    Science.gov (United States)

    Yamunadevi, Andamuthu; Selvamani, M; Vinitha, V; Srivandhana, R; Balakrithiga, M; Prabhu, S; Ganapathy, N

    2015-08-01

    To record the prevalence rate of dental anomalies in Dravidian population and analyze the percentage of individual anomalies in the population. A cluster sample analysis was done, where 244 subjects studying in a dental institution were all included and analyzed for occurrence of dental anomalies by clinical examination, excluding third molars from analysis. 31.55% of the study subjects had dental anomalies and shape anomalies were more prevalent (22.1%), followed by size (8.6%), number (3.2%) and position anomalies (0.4%). Retained deciduous was seen in 1.63%. Among the individual anomalies, Talon's cusp (TC) was seen predominantly (14.34%), followed by microdontia (6.6%) and supernumerary cusps (5.73%). Prevalence rate of dental anomalies in the Dravidian population is 31.55% in the present study, exclusive of third molars. Shape anomalies are more common, and TC is the most commonly noted anomaly. Varying prevalence rate is reported in different geographical regions of the world.

  1. Mobile dental units: leasing or buying? A dollar-cost analysis.

    Science.gov (United States)

    Arevalo, Oscar; Saman, Daniel M; Bonaime, Alice; Skelton, Judy

    2010-01-01

    The decision to acquire a mobile dental unit is based on a standard capital budgeting analysis. The next step is to determine whether to obtain the use of the mobile dental unit by borrowing and purchasing or by leasing. As a financing mechanism, leases are simply another way of borrowing money to pay for the asset. To compare lease vs. debt as financial vehicles to acquiring a mobile dental unit. An estimate for a new mobile unit was obtained. Lease and loan proposals from financial lenders were collected. A cost of capital rate was chosen for comparison. Cash flows associated with borrowing and leasing vs. buying were determined fortwo different scenarios: for profit (FP) vs. not-for-profit (NFP), at 5 years. A dollar-cost analysis was utilized to determine the option with the lowest capitalized value. There was a net advantage to buying vs. leasing for both for FP and NFP organizations. Due to tax advantages, owning and leasing were substantially less expensive for FP than for NFP. Slight decreases in the monthly lease payments would make leasing competitive to the buying approach. Exploring alternative financing vehicles may allow dental programs to expand their services through the acquisition of a mobile unit. Though programs generally own assets, it is the use of the asset which is important rather than the ownership. Dental programs can find leasing an attractive alternative by offering access to capital with cash-flow advantages.

  2. The Effect of Dental Insurance on the Use of Dental Care For Older Adults: A Partial Identification Analysis*

    Science.gov (United States)

    Kreider, Brent; Moeller, John; Manski, Richard J.; Pepper, John

    2014-01-01

    We evaluate the impact of dental insurance on the use of dental services using a potential outcomes identification framework designed to handle uncertainty created by unknown counterfactuals – that is, the endogenous selection problem – as well as uncertainty about the reliability of self-reported insurance status. Using data from the Health and Retirement Study, we estimate that utilization rates of adults older than 50 would increase from 75% to around 80% under universal dental coverage. PMID:24890257

  3. Analysis of a radiation incident with intraoral dental radiological equipment

    International Nuclear Information System (INIS)

    Malone, J.F.

    1996-01-01

    A case is described involving a serious incident with dental radiological equipment, containing many lessons that may be applied to the preparation of other cases. The description includes an account of the incident, the circumstances surrounding it, the dosimetry, risk estimates and the medical consequences of the incident. In addition, some aspects of the associated legal proceedings are reviewed and assessed. As a result of the incident described, a number of conclusions are drawn with respect to important practices in ensuring the safety of installations and the value of evidence brought forward by expert witnesses. (author)

  4. Applied behavior analysis: behavior management of children with autism spectrum disorders in dental environments.

    Science.gov (United States)

    Hernandez, Purnima; Ikkanda, Zachary

    2011-03-01

    There are a limited number of studies addressing behavior management techniques and procedural modifications that dentists can use to treat people with an autism spectrum disorder (ASD). The authors conducted a search of the dental and behavioral analytic literature to identify management techniques that address problem behaviors exhibited by children with ASDs in dental and other health-related environments. Applied behavior analysis (ABA) is a science in which procedures are based on the principles of behavior through systematic experimentation. Clinicians have used ABA procedures successfully to modify socially significant behaviors of people with ASD. Basic behavior management techniques currently used in dentistry may not encourage people with cognitive and behavioral disabilities, such as ASD, to tolerate simple in-office dental procedures consistently. Instead, dental care providers often are required to use advanced behavior management techniques to complete simple in-office procedures such as prophylaxis, sealant placement and obtaining radiographs. ABA procedures can be integrated in the dental environment to manage problem behaviors often exhibited by children with an ASD. The authors found no evidence-based procedural modifications that address the behavioral characteristics and problematic behaviors of children with an ASD in a dental environment. Further research in this area should be conducted. Knowledge and in-depth understanding of behavioral principles is essential when a dentist is concerned with modifying behaviors. Using ABA procedures can help dentists manage problem behaviors effectively and systematically when performing routine dental treatment. Being knowledgeable about each patient's behavioral characteristics and the parents' level of involvement is important in the successful integration of the procedures and reduction of in-office time.

  5. Concept Analysis: Alzheimer’s Caregiver Stress

    Science.gov (United States)

    Llanque, Sarah; Savage, Lynette; Rosenburg, Neal; Honor’s, BA; Caserta, Michael

    2015-01-01

    AIM The aim of this article was to analyze the concept of caregiver stress in the context of caring for a person with Alzheimer’s disease and related dementias. BACKGROUND Currently, there are more than 15 million unpaid care-givers for persons suffering from Alzheimer’s disease and related dementias. This unpaid care can be stressful for caregivers due to the chronic nature of the disease process, as well as other factors. METHOD The paper incorporates the modified method of Wilson’s concept analysis procedure to analyze the concept of caregiver stress. DATA SOURCES A review of the literature was undertaken using the Cumulative Index to Nursing and Allied Health Literature, Google Scholar, and PubMed. RESULTS A theoretical definition of caregiver stress is provided, and the defining attributes, related concepts, antecedents, and consequences of caregiver stress are proposed, and case studies are presented. CONCLUSIONS The analysis demonstrates that caregiver stress is the unequal exchange of assistance among people who stand in close relationship to one another, which results in emotional and physical stress on the caregiver. Implications for future nursing research and practice conclude the paper. PMID:24787468

  6. Legal analysis of information displayed on dental material packages: An exploratory research

    Directory of Open Access Journals (Sweden)

    Bhumika Rathore

    2016-01-01

    Full Text Available Introduction: Some of the dental materials possess occupational hazards, preprocedural errors, and patient allergies as suggested by evidence. With due consideration to safety of the patients and dental professionals, it is essential that the trade of these materials is in conformity with the law. Aim: To perform the legal analysis of the information displayed on the packaging of dental materials. Materials and Methods: The Bureau of Indian Standards sets guidelines for packaging and marketing of dental products in India. An exploratory cross-sectional study was performed using various search engines and websites to access the laws and regulations existing pertaining to dental materials packaging. Based on the data obtained, a unique packaging standardization checklist was developed. Dental laboratory and impression plasters, alginates, and endodontic instruments were surveyed for all the available brands. This study considered 16 brands of plasters and alginates and 42 brands of endodontic instruments for legal analysis. Legal analysis was performed using the direct observation checklist. Descriptive statistics were obtained using SPSS version 19. Results: The guidelines set by the Bureau of Indian Standards do exist but are not updated and stand as oblivious guards for marketing standards. Overall compliance to the guidelines was reported to be 18.5% by brands of alginates, 4.1% by plaster of Paris, and 11.11% by endodontic instruments. Wave One™ File reported maximum adherence with the guidelines as 66.7%. Conclusion: This study found lower rate of adherence to the guidelines, thus indicating insufficient information being disclosed to the consumers.

  7. Assessment of Various Risk Factors for Success of Delayed and Immediate Loaded Dental Implants: A Retrospective Analysis.

    Science.gov (United States)

    Prasant, M C; Thukral, Rishi; Kumar, Sachin; Sadrani, Sannishth M; Baxi, Harsh; Shah, Aditi

    2016-10-01

    Ever since its introduction in 1977, a minimum of few months of period is required for osseointegration to take place after dental implant surgery. With the passage of time and advancements in the fields of dental implant, this healing period is getting smaller and smaller. Immediate loading of dental implants is becoming a very popular procedure in the recent time. Hence, we retrospectively analyzed the various risk factors for the failure of delayed and immediate loaded dental implants. In the present study, retrospective analysis of all the patients was done who underwent dental implant surgeries either by immediate loading procedure or by delayed loading procedures. All the patients were divided broadly into two groups with one group containing patients in which delayed loaded dental implants were placed while other consisted of patients in whom immediate loaded dental implants were placed. All the patients in whom follow-up records were missing and who had past medical history of any systemic diseases were excluded from the present study. Evaluation of associated possible risk factors was done by classifying the predictable factors as primary and secondary factors. All the results were analyzed by Statistical Package for the Social Sciences (SPSS) software. Kaplan-Meier survival analyses and chi-square test were used for assessment of level of significance. In delayed and immediate group of dental implants, mean age of the patients was 54.2 and 54.8 years respectively. Statistically significant results were obtained while comparing the clinical parameters of the dental implants in both the groups while demographic parameters showed nonsignificant correlation. Significant higher risk of dental implant failure is associated with immediate loaded dental implants. Tobacco smoking, shorter implant size, and other risk factors play a significant role in predicting the success and failure of dental implants. Delayed loaded dental implant placement should be preferred

  8. Analysis of select facial and dental esthetic parameters.

    Science.gov (United States)

    Nold, Sarah L; Horvath, Sebastian D; Stampf, Susanne; Blatz, Markus B

    2014-01-01

    This clinical study examined objective smile parameters in the natural anterior dentition. Standardized intraoral and extraoral photographs were taken of 106 Caucasian adults (54 women, 52 men) with a healthy dentition. The following parameters were analyzed: correlation of dental and facial midline, upper lip position and curvature, relationship of the maxillary anterior incisal curve with lower lip, number of teeth displayed in a smile, distance between maxillary anterior teeth and lower lip, slope of tooth, and lip arc. The simple frequency distribution of measured variables revealed an average smile with coinciding dental and facial midlines, an average smile line, and a straight upper lip curvature. With an average smile, the maxillary anterior teeth did not touch the lower lip, teeth were displayed up to the second premolar, and the maxillary anterior incisal curve was parallel to the lower lip. Oval was the most prevalent tooth form. A slope of 9 degrees was detected for the mean tooth arc and 13 degrees for the mean lip arc. The outcomes of this clinical study provide a quantifiable frame for esthetic evaluation, treatment planning, and restoration fabrication.

  9. Effect of lubricant on the reliability of dental implant abutment screw joint: An in vitro laboratory and three-dimension finite element analysis.

    Science.gov (United States)

    Wu, Tingting; Fan, Hongyi; Ma, Ruiyang; Chen, Hongyu; Li, Zhi; Yu, Haiyang

    2017-06-01

    Biomechanical factors play a key role in the success of dental implants. Fracture and loosening of abutment screws are major issues. This study investigated the effect of lubricants on the stability of dental implant-abutment connection. As lubricants, graphite and vaseline were coated on the abutment screw surface, respectively, and a blank without lubricant served as the control. The total friction coefficient (μ tot ), clamping force, fatigue behavior and detorque of the joint combined with dynamic cyclic loading were measured under different lubricating conditions. Further, a three-dimensional finite element analysis was used to investigate stress distribution, in conjunction with experimental images. The results showed that the lubricant reduced μ tot , which in turn led to an increase in clamping force. Decrease in loading increased the fatigue life of the screw. However, use of lubricant at high load reduced the fatigue life. Ductile fracture at the first thread of the screw was the chief failure mode, which was due to maximum von Mises stress. Higher stress levels occurred in the lubricant groups. Lubricated screws resulted in lower detorque which made the joint easier to loosen. In conclusion, the lubricant cannot effectively improve the reliability of dental implant-abutment connection. Keeping the interfaces of implant-screw uncontaminated and strengthening the surface of the screw may be recommend for clinical operation and future design. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Stress analysis for robot arm version 2

    International Nuclear Information System (INIS)

    Anwar Abdul Rahman; Fikri, A.; Salleh, M. S.; Mohd Arif Hamzah; Azraf Azman; Rosli Darmawan; Mohd Rizal Mamat

    2010-01-01

    The design of a robot needs to be analyzed to ensure the specification and requirement by the user is full filled. Therefore, stress analysis has been performed on the robot arm version 2 after its complete fabrication. This paper discusses the result of the analysis and proposed measures to improve the future design of robot arm. (author)

  11. Food advertisements on UK television popular with children: a content analysis in relation to dental health.

    Science.gov (United States)

    Al-Mazyad, M; Flannigan, N; Burnside, G; Higham, S; Boyland, E

    2017-02-10

    Objective To quantify the prevalence of advertising for foods and beverages potentially detrimental to dental health on UK television watched by children.Design Content analysis of pre-recorded television advertisements (adverts).Materials and methods Three hundred and fifty-two hours of television were recorded (one weekday and one weekend day, 6 am - 10 pm) from the main commercial channel (ITV1). All adverts were coded using pre-defined criteria.Setting UK television recorded between January and December 2012.Results Of 9,151 adverts, foods and beverages were the second most commonly advertised products (16.7%; n = 1,532). Nearly two-thirds of food adverts were for items that are potentially harmful to dental health (61%; n = 934). Of these, 96.6% were cariogenic and 11% were acidogenic foods. During peak children's viewing hours, the proportion of foods that are potentially harmful to dental health was significantly higher than for non-harmful foods (65.9% vs. 34.1%; p = 0.011). Adverts for foods potentially harmful to dental health were rare around children's programmes, but significantly more frequent during other programmes watched by children (p <0.001).Conclusion UK children are exposed to a particularly high proportion of advertisements for foods that are potentially detrimental to their dental health during their peak viewing hours and around the programmes they watch the most.

  12. Biomechanics of the press-fit phenomenon in dental implantology: an image-based finite element analysis

    Directory of Open Access Journals (Sweden)

    Frisardi Gianni

    2012-05-01

    Full Text Available Abstract Background A fundamental pre-requisite for the clinical success in dental implant surgery is the fast and stable implant osseointegration. The press-fit phenomenon occurring at implant insertion induces biomechanical effects in the bone tissues, which ensure implant primary stability. In the field of dental surgery, the understanding of the key factors governing the osseointegration process still remains of utmost importance. A thorough analysis of the biomechanics of dental implantology requires a detailed knowledge of bone mechanical properties as well as an accurate definition of the jaw bone geometry. Methods In this work, a CT image-based approach, combined with the Finite Element Method (FEM, has been used to investigate the effect of the drill size on the biomechanics of the dental implant technique. A very accurate model of the human mandible bone segment has been created by processing high resolution micro-CT image data. The press-fit phenomenon has been simulated by FE analyses for different common drill diameters (DA = 2.8 mm, DB = 3.3 mm, and DC = 3.8 mm with depth L = 12 mm. A virtual implant model has been assumed with a cylindrical geometry having height L = 11 mm and diameter D = 4 mm. Results The maximum stresses calculated for drill diameters DA, DB and DC have been 12.31 GPa, 7.74 GPa and 4.52 GPa, respectively. High strain values have been measured in the cortical area for the models of diameters DA and DB, while a uniform distribution has been observed for the model of diameter DC . The maximum logarithmic strains, calculated in nonlinear analyses, have been ϵ = 2.46, 0.51 and 0.49 for the three models, respectively. Conclusions This study introduces a very powerful, accurate and non-destructive methodology for investigating the effect of the drill size on the biomechanics of the dental implant technique. Further studies could aim at understanding how different drill

  13. Age, period, and cohort analysis of regular dental care behavior and edentulism: A marginal approach

    Science.gov (United States)

    2011-01-01

    Background To analyze the regular dental care behavior and prevalence of edentulism in adult Danes, reported in sequential cross-sectional oral health surveys by the application of a marginal approach to consider the possible clustering effect of birth cohorts. Methods Data from four sequential cross-sectional surveys of non-institutionalized Danes conducted from 1975-2005 comprising 4330 respondents aged 15+ years in 9 birth cohorts were analyzed. The key study variables were seeking dental care on an annual basis (ADC) and edentulism. For the analysis of ADC, survey year, age, gender, socio-economic status (SES) group, denture-wearing, and school dental care (SDC) during childhood were considered. For the analysis of edentulism, only respondents aged 35+ years were included. Survey year, age, gender, SES group, ADC, and SDC during childhood were considered as the independent factors. To take into account the clustering effect of birth cohorts, marginal logistic regressions with an independent correlation structure in generalized estimating equations (GEE) were carried out, with PROC GENMOD in SAS software. Results The overall proportion of people seeking ADC increased from 58.8% in 1975 to 86.7% in 2005, while for respondents aged 35 years or older, the overall prevalence of edentulism (35+ years) decreased from 36.4% in 1975 to 5.0% in 2005. Females, respondents in the higher SES group, in more recent survey years, with no denture, and receiving SDC in all grades during childhood were associated with higher probability of seeking ADC regularly (P dental health policy was demonstrated by a continued increase of regular dental visiting habits and tooth retention in adults because school dental care was provided to Danes in their childhood. PMID:21410991

  14. Implications of stress range for inelastic analysis

    International Nuclear Information System (INIS)

    Karabin, M.E.; Dhalla, A.K.

    1981-01-01

    The elastic stress range over a complete load cycle is routinely used to formulate simplified rules regarding the inelastic behavior of structures operating at elevated temperature. For example, a 300 series stainless steel structure operating at elevated temperature, in all probability, would satisfy the ASME Boiler and Pressure Vessel Code criteria if the linearized elastic stress range is less than three times the material yield strength. However, at higher elastic stress ranges it is difficult to judge, a priori, that a structural component would comply with inelastic Code criteria after a detailed inelastic analysis. The purpose of this paper is to illustrate that it is not the elastic stress range but the stress intensities at specific times during a thermal transient which provide a better insight into the inelastic response of the structure. The specific example of the CRBRP flued head design demonstrates that the temperature differential between various parts of the structure can be changed by modifying the insulation pattern and heat flow path in the structure, without significantly altering the elastic stress range over a complete load cycle. However, the modified design did reduce the stress intensity during steady state elevated temperature operation. This modified design satisfied the inelastic Code criteria whereas the initial design failed to comply with the strain accumulation criterion

  15. Stress analysis of PCV nozzle junction

    International Nuclear Information System (INIS)

    Uchiyama, Shoichi; Oikawa, Tsuneo; Hoshino, Seizo

    1976-01-01

    Most of various pressure vessels comprise each one cylindrical shell and one or more nozzles. In this study, in order to analyze the stress in the structures of this type as minutely and exactly as possible, the program for stress analysis by the finite element method was made, which is required for the strength analysis for three-dimensional structures. Especially, the problem of the stress distribution around nozzle junctions was solved theoretically with the program. The program for the analysis developed in this study is provided with various functions, such as the input generator for cylindrical, conical and spherical shells, and plotter, and is very covenient. The accuracy of analysis is very good. The method of analysis and the calculation of the rigidity matrices for the deformation in plane and bending are explained. The result of the stress analysis around the nozzle junctions of a containment vessel with this program was in good agreement with experimental data and the result with SAP-4 code, therefore the propriety of the calculated result with this program was proved. Also calculations were carried out on three cases, namely a flat plate fixed at one end with distributed load, a cylinder fixed at one end with internal pressure, and an I-beam fixed at one end with concentrated load. The calculated results agreed well with theoretical solutions in all cases. (Kako, I.)

  16. Fracture analysis of randomized implant-supported fixed dental prostheses

    Science.gov (United States)

    Esquivel-Upshaw, Josephine F.; Mehler, Alex; Clark, Arthur E.; Neal, Dan; Anusavice, Kenneth J.

    2014-01-01

    Objective Fractures of posterior fixed dental all-ceramic prostheses can be caused by one or more factors including prosthesis design, flaw distribution, direction and magnitude of occlusal loading, and nature of supporting infrastructure (tooth root/implant), and presence of adjacent teeth. This clinical study of implant-supported, all-ceramic fixed dental prostheses, determined the effects of (1) presence of a tooth distal to the most distal retainer; (2) prosthesis loading either along the non-load bearing or load bearing areas; (3) presence of excursive contacts or maximum intercuspation contacts in the prosthesis; and (4) magnitude of bite force on the occurrence of veneer ceramic fracture. Methods 89 implant-supported FDPs were randomized as either a three-unit posterior metal-ceramic (Au-Pd-Ag alloy and InLine POM, Ivoclar, Vivadent) FDP or a ceramic-ceramic (ZirCAD and ZirPress, Ivoclar, Vivadent) FDP. Two implants (Osseospeed, Dentsply) and custom abutments (Atlantis, Dentsply) supported these FDPs, which were cemented with resin cement (RelyX Universal Cement). Baseline photographs were made with markings of teeth from maximum intercuspation (MI) and excursive function. Patients were recalled at 6 months and 1 to 3 years. Fractures were observed, their locations recorded, and images compared with baseline photographs of occlusal contacts. Conclusion No significant relationship exists between the occurrence of fracture and: (1) the magnitude of bite force; (2) a tooth distal to the most distal retainer; and (3) contacts in load-bearing or non-load-bearing areas. However, there was a significantly higher likelihood of fracture in areas with MI contacts only. Clinical Significance This clinical study demonstrates that there is a need to evaluate occlusion differently with implant-supported prostheses than with natural tooth supported prostheses because of the absence of a periodontal ligament. Implant supported prostheses should have minimal occlusion and

  17. Bioengineering of Dental Tissues: Bibliometric Analysis 2000-2011.

    Directory of Open Access Journals (Sweden)

    Sebastián Zamorano

    2014-03-01

    Full Text Available Introduction: There has been a noticeable increase in experimental use and therapies based on stem cells over recent years. Nevertheless, there is a lack of information about this progress in the dental field, which makes it difficult to trace development and design policies. The purpose of this study, as a first approach to the subject, is to determine a bibliometric profile for the investigation related to bioengineering of dental tissue at a worldwide scale, based on the MEDLINE database, for the period 2000-2011. Methodology: A bibliometric study was carried out. Every article indexed in the MEDLINE database and associated with the terms “stem cells” and “tooth regeneration” for the period 2000-2011 was included. The analyzed variables were publishing date, country of origin, language and publication type (original or review, journal, author, associated university and tissue source (human or animal. Results: For the entire period included in the study, 257 articles were found. Of these, 149 corresponded to original Works published in English; 5 in other languages; 92 comprised literature reviews in English, 9 in other languages and 2 publications were included in the “others” category. The countries with the highest research productivity were the United States (24.51%, Japan (20.62% and China (17.90%, while Brazil (3.9% was the only Latin-American country found in the list. Animal tissues were used in 59.09% of them. The most productive authors were Ueda M (17 and Jin Y (11, whereas Fourth Military University (13, University of Tokyo (12 and Capital Medical University (10 had the largest number of publications. Conclusion: The United States, Japan and China concentrate about two thirds of the production. Latin-America was represented only by Brazil.

  18. Effectiveness of problem-based learning in Chinese dental education: a meta-analysis.

    Science.gov (United States)

    Huang, Beilei; Zheng, Liwei; Li, Chunjie; Li, Li; Yu, Haiyang

    2013-03-01

    This article provides a critical overview of problem-based learning (PBL) practice in dental education in China. Because the application of PBL has not been carried out on a large scale in Chinese dental education, this review was performed to investigate its effectiveness. Databases were searched for studies that met the inclusion criteria, with study identification and data extraction performed by two reviewers independently. Meta-analysis was done with Revman 5.1. Eleven randomized controlled trials were included. The meta-analysis found that PBL had a positive effect on gaining higher theoretical (SMD=0.88, 95% CI [0.46, 1.31], peffect on gaining higher pass rates (RR=1.06, 95% CI [0.97, 1.16], p=0.21). This meta-analysis suggests that the PBL pedagogy is considered superior to the traditional lecture-based teaching in this setting. PBL methods could be an optional supplementary method of dental teaching models in China. However, Chinese dental schools should devise PBL curricula according to their own conditions. The effectiveness of PBL should be optimized maximally with all these limitations.

  19. Influence of tooth bleaching on dental enamel microhardness: a systematic review and meta-analysis.

    Science.gov (United States)

    Zanolla, J; Marques, Abc; da Costa, D C; de Souza, A S; Coutinho, M

    2017-09-01

    Several studies have investigated the effect of bleaching on dental tissues. The evaluation of the effect of home bleaching with 10% carbamide peroxide is important for assessing alterations in enamel microhardness that may affect dental health in terms of resistance to masticatory forces. This meta-analysis was performed in order to determine scientific evidence regarding the effects of home vital bleaching with 10% carbamide peroxide gel on the microhardness of human dental enamel. A systematic electronic literature search was conducted in the PubMed and Web of Science databases using search terms. Two independent researchers evaluated the information and methodological quality of the studies. Inclusion and exclusion criteria were established for article selection; further, only studies published in English were selected. Thirteen studies that met all of the inclusion and exclusion criteria were selected and underwent statistical analysis. The results of this meta-analysis showed no significant changes in enamel microhardness when using the 10% carbamide peroxide bleaching gel over periods of 7, 14 and 21 days. © 2016 Australian Dental Association.

  20. Does Bruxism Contribute to Dental Implant Failure? A Systematic Review and Meta-Analysis.

    Science.gov (United States)

    Zhou, Yi; Gao, Jinxia; Luo, Le; Wang, Yining

    2016-04-01

    Bruxism was usually considered as a contraindication for oral implanting. The causal relationship between bruxism and dental implant failure was remained controversial in existing literatures. This meta-analysis was performed to investigate the relationship between them. This review conducted an electronic systematic literature search in MEDLINE (PubMed) and EmBase in November 2013 without time and language restrictions. Meanwhile, a hand searching for all the relevant references of included studies was also conducted. Study information extraction and methodological quality assessments were accomplished by two reviewers independently. A discussion ensued if any disagreement occurred, and unresolved issues were solved by consulting a third reviewer. Methodological quality was assessed by using the Newcastle-Ottawa Scale tool. Odds ratio (OR) with 95% confidence interval (CI) was pooled to estimate the relative effect of bruxism on dental implant failures. Fixed effects model was used initially; if the heterogeneity was high, random effects model was chosen for meta-analysis. Statistical analyses were carried out by using Review Manager 5.1. In this meta-analysis review, extracted data were classified into two groups based on different units. Units were based on the number of prostheses (group A) and the number of patients (group B). In group A, the total pooled OR of bruxers versus nonbruxers for all subgroups was 4.72 (95% CI: 2.66-8.36, p = .07). In group B, the total pooled OR of bruxers versus nonbruxers for all subgroups was 3.83 (95% CI: 2.12-6.94, p = .22). This meta-analysis was performed to evaluate the relationship between bruxism and dental implant failure. In contrast to nonbruxers, prostheses in bruxers had a higher failure rate. It suggests that bruxism is a contributing factor of causing the occurrence of dental implant technical/biological complications and plays a role in dental implant failure. © 2015 Wiley Periodicals, Inc.

  1. Exploring factors associated with traumatic dental injuries in preschool children: a Poisson regression analysis.

    Science.gov (United States)

    Feldens, Carlos Alberto; Kramer, Paulo Floriani; Ferreira, Simone Helena; Spiguel, Mônica Hermann; Marquezan, Marcela

    2010-04-01

    This cross-sectional study aimed to investigate the factors associated with dental trauma in preschool children using Poisson regression analysis with robust variance. The study population comprised 888 children aged 3- to 5-year-old attending public nurseries in Canoas, southern Brazil. Questionnaires assessing information related to the independent variables (age, gender, race, mother's educational level and family income) were completed by the parents. Clinical examinations were carried out by five trained examiners in order to assess traumatic dental injuries (TDI) according to Andreasen's classification. One of the five examiners was calibrated to assess orthodontic characteristics (open bite and overjet). Multivariable Poisson regression analysis with robust variance was used to determine the factors associated with dental trauma as well as the strengths of association. Traditional logistic regression was also performed in order to compare the estimates obtained by both methods of statistical analysis. 36.4% (323/888) of the children suffered dental trauma and there was no difference in prevalence rates from 3 to 5 years of age. Poisson regression analysis showed that the probability of the outcome was almost 30% higher for children whose mothers had more than 8 years of education (Prevalence Ratio = 1.28; 95% CI = 1.03-1.60) and 63% higher for children with an overjet greater than 2 mm (Prevalence Ratio = 1.63; 95% CI = 1.31-2.03). Odds ratios clearly overestimated the size of the effect when compared with prevalence ratios. These findings indicate the need for preventive orientation regarding TDI, in order to educate parents and caregivers about supervising infants, particularly those with increased overjet and whose mothers have a higher level of education. Poisson regression with robust variance represents a better alternative than logistic regression to estimate the risk of dental trauma in preschool children.

  2. Risk factors for dental caries in childhood: a five-year survival analysis.

    Science.gov (United States)

    Lee, Hyo-Jin; Kim, Jin-Bom; Jin, Bo-Hyoung; Paik, Dai-Il; Bae, Kwang-Hak

    2015-04-01

    The purpose of this study was to examine the risk factors of dental caries at the level of an individual person with survival analysis of the prospective data for 5 years. A total of 249 first-grade students participated in a follow-up study for 5 years. All participants responded to a questionnaire inquiring about socio-demographic variables and oral health behaviors. They also received an oral examination and were tested for Dentocult SM and LB. Over 5 years, the participants received yearly oral follow-up examinations to determine the incidence of dental caries. The incidence of one or more dental caries (DC1) and four or more dental caries (DC4) were defined as one or more and four or more decayed, missing, and filled permanent teeth increments, respectively. Socio-demographic variables, oral health behaviors, and status and caries activity tests were assessed as risk factors for DC1 and DC4. The adjusted hazard ratios (HRs) of risk factors for DC1 and DC4 were calculated using Cox proportional hazard regression models. During the 5-year follow-up period, DC1 and DC4 occurred in 87 and 25 participants, respectively. In multivariate hazard models, five or more decayed, missing, and filled primary molar teeth [HR 1.93, 95% confidence interval (CI) 1.19-3.13], and Dentocult LB of two or three (HR 2.21, 95% CI 1.37-3.56) were independent risk factors of DC1. For DC4, only Dentocult LB of two or three was an independent risk factor (HR 2.95, 95% CI 1.11-7.79). Our results suggest that dental caries incidence at an individual level can be associated with the experience of dental caries in primary teeth and Dentocult LB based on the survival models for the 5-year prospective data. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  3. Plant stress analysis technology deployment

    Energy Technology Data Exchange (ETDEWEB)

    Ebadian, M.A.

    1998-01-01

    Monitoring vegetation is an active area of laser-induced fluorescence imaging (LIFI) research. The Hemispheric Center for Environmental Technology (HCET) at Florida International University (FIU) is assisting in the transfer of the LIFI technology to the agricultural private sector through a market survey. The market survey will help identify the key eco-agricultural issues of the nations that could benefit from the use of sensor technologies developed by the Office of Science and Technology (OST). The principal region of interest is the Western Hemisphere, particularly, the rapidly growing countries of Latin America and the Caribbean. The analysis of needs will assure that the focus of present and future research will center on economically important issues facing both hemispheres. The application of the technology will be useful to the agriculture industry for airborne crop analysis as well as in the detection and characterization of contaminated sites by monitoring vegetation. LIFI airborne and close-proximity systems will be evaluated as stand-alone technologies and additions to existing sensor technologies that have been used to monitor crops in the field and in storage.

  4. Electromagnetic field and mechanical stress analysis code

    International Nuclear Information System (INIS)

    1978-01-01

    Analysis TEXMAGST is a two stage linear finite element code for the analysis of static magnetic fields in three dimensional structures and associated mechanical stresses produced by the anti J x anti B forces within these structures. The electromagnetic problem is solved in terms of magnetic vector potential A for a given current density anti J as curl 1/μ curl anti A = anti J considering the magnetic permeability as constant. The Coulombian gauge (div anti A = o) was chosen and was implemented through the use of Lagrange multipliers. The second stage of the problem - the calculation of mechanical stresses in the same three dimensional structure is solved by using the same code with few modifications - through a restart card. Body forces anti J x anti B within each element are calculated from the solution of the first stage run and represent the input to the second stage run which will give the solution for the stress problem

  5. Blended learning for reinforcing dental pharmacology in the clinical years: A qualitative analysis.

    Science.gov (United States)

    Eachempati, Prashanti; Kiran Kumar, K S; Sumanth, K N

    2016-10-01

    Blended learning has become the method of choice in educational institutions because of its systematic integration of traditional classroom teaching and online components. This study aims to analyze student's reflection regarding blended learning in dental pharmacology. A cross-sectional study was conducted in Faculty of Dentistry, Melaka-Manipal Medical College among 3 rd and 4 th year BDS students. A total of 145 dental students, who consented, participate in the study. Students were divided into 14 groups. Nine online sessions followed by nine face-to-face discussions were held. Each session addressed topics related to oral lesions and orofacial pain with pharmacological applications. After each week, students were asked to reflect on blended learning. On completion of 9 weeks, reflections were collected and analyzed. Qualitative analysis was done using thematic analysis model suggested by Braun and Clarke. The four main themes were identified, namely, merits of blended learning, skill in writing prescription for oral diseases, dosages of drugs, and identification of strengths and weakness. In general, the participants had a positive feedback regarding blended learning. Students felt more confident in drug selection and prescription writing. They could recollect the doses better after the online and face-to-face sessions. Most interestingly, the students reflected that they are able to identify their strength and weakness after the blended learning sessions. Blended learning module was successfully implemented for reinforcing dental pharmacology. The results obtained in this study enable us to plan future comparative studies to know the effectiveness of blended learning in dental pharmacology.

  6. Reduced dental calcium expression and dental mass in chronic sleep deprived rats: Combined EDS, TOF-SIMS, and micro-CT analysis

    Science.gov (United States)

    Kuo, Yi-Jie; Huang, Yung-Kai; Chou, Hsiu-Chu; Pai, Man-Hui; Lee, Ai-Wei; Mai, Fu-Der; Chang, Hung-Ming

    2015-08-01

    Teeth are the hardest tissue in the body. The growth of teeth is closely regulated by circadian rhythmicity. Considering that sleep deprivation (SD) is a severe condition that disrupts normal circadian rhythmicity, this study was conducted to determine whether calcium expression (the major element participating in teeth constitution), and dental mass would be significantly impaired following SD. Adolescent rats subjected to 3 weeks of SD were processed for energy dispersive spectrum (EDS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and micro-computed tomography (micro-CT) analyses. The EDS and TOF-SIMS results indicated that high calcium intensity was detected in both the upper and lower incisors of untreated rats. Micro-CT analysis corresponded closely with spectral data in which an enhanced dental mass was calculated in intact animals. However, following SD, both calcium expression and the dental mass were remarkably decreased to nearly half those of the untreated values. Because SD plays a detrimental role in impairing dental structure, establishing satisfactory sleep behavior would therefore serve as a crucial strategy for preventing or improving prevalent dental dysfunctions.

  7. PIXE analysis of trace and other mineral elements in Romanian dental composites

    International Nuclear Information System (INIS)

    Preoteasa, E. A.; Iordan, Andreea; Harangus, Livia; Ciortea, C.; Moldovan, Maria

    2002-01-01

    Dental composites made of silicates and oxides particles embedded in an organic polymer, show a dynamic evolution but are rather expensive. Recently, the Romanian biomaterial 'Restacril' offered a low-cost alternative. Because the durability of the composite dental fillings depends both on the main chemical composition and on the impurities that may influence the inorganic particles' properties and thus modifying the bio material clinical behaviour, the elemental analysis of the material is necessary for improving its quality. Particle-induced X-ray emission (PIXE), a sensitive method for multielemental trace detection widely used in biomedical applications, allowed us to evidence 21 mineral elements with Z > 14 in some commercial dental composites. Here we evaluate the performances of PIXE for the control of dental composites by carrying out qualitative analysis of three Romanian biomaterials. PIXE measurements on thick composite samples with a flat surface were done with 3 MeV protons at the NIPNE-HH (Horia Hulubei National Institute for Physics and Nuclear Engineering) tandem accelerator, using a hyper-pure Ge detector, 30 mm thick Al absorber foil and integration of beam current. Up to 21 elements with Z > 19 were detected: K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Ga, Sr, Zr, Nb, Ru, Ag, Ba, Yb, Nd, Hf, Au, As and Pb. The orders of magnitude of relative concentrations were evaluated using X-ray yields obtained for another light element thick composite target. The Romanian composites have specific and diverse compositions, containing a great number of minor and trace elements, many of whom are impurities. Use of higher purity raw materials is suggested to reduce the latter and improve the materials' quality. Refinement of X-ray yields by better matching matrixes calculations and use of concentration standards are proposed for quantitative PIXE analysis of the dental composites. (authors)

  8. Undergraduate degree projects in the Swedish dental schools: a documentary analysis.

    Science.gov (United States)

    Franzén, C; Brown, G

    2013-05-01

    Undergraduate degree projects have currently been introduced into courses in the four Swedish dental schools. The rationale for research projects is that they enable students to develop research expertise skills and to show their ability to apply and develop knowledge relevant to professional practice. This paper reports a qualitative analysis of the curriculum documents and handbooks including the criteria used to assess the students' research reports. The aim was to investigate commonalities and differences in the design of degree projects between the four Swedish dental schools and to explore any inconsistencies within the documents. The documentary analysis was based on the constant comparison method. Four overarching themes emerged from the analysis: (i) developing scientific expertise, (ii) developing professional expertise, (iii) following rules and (iv) fostering creativity. The documents from the four dental schools revealed similar views on the purposes of the projects and provided similar assessment criteria. The students were requested to formulate an odontological problem, apply a relevant scientific method, analyse texts and empirical data, express critical reflections and write a short thesis. The students were free to choose topics. There were differences between the dental schools on the emphasis placed on practical uses of the projects and theoretical background of the projects. Two of the schools insisted on rigid rules of completing and writing the project yet paradoxically emphasised creativity. There were wide variations in the required length of the project report. The report may prove useful to dental schools in other countries who are about to design undergraduate research projects. © 2013 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd.

  9. Analysis of Biaxially Stressed Bridge Deck Plates

    DEFF Research Database (Denmark)

    Jönsson, Jeppe; Bondum, Tommi Højer

    2012-01-01

    The ultimate state analysis of bridge deck plates at the intersection zone between main girders and transverse beams is complicated by biaxial membrane stresses, which may be in compression or tension in either direction depending on the bridge configuration and the specific location. This paper...

  10. Stress analysis of a rupture disk

    International Nuclear Information System (INIS)

    Werne, R.W.

    1975-04-01

    The results of an elastic stress analysis of the rupture disk for an internal pressure of 45.5 MPa (6600 psi) indicate that the maximum von Mises stresses occur in the membrane and are on the order of 483 to 690 MPa (70,000 psi). This far exceeds the yield of the membrane material of 207 MPa (30,000 psi). These high stresses are expected since the membrane is designed to burst at that design pressure. The von Mises stresses in the rest of the body are less than 138 MPa (20,000 psi). An elastic-plastic analysis of the membrane alone subjected to the 45.5 MPa (6600 psi) pressure indicates that it becomes plastically unstable, i.e., it continues to deform under constant load. A second load case with a constant 6.9 MPa (1000 psi) pressure throughout the entire body (i.e., after release of pressure by burst of the membrane) was analyzed. The results indicate that the elastic von Mises stresses are less than 26.7 MPa (3880 psi) throughout the body. (U.S.)

  11. Mineral elements in dental composites by atomic and nuclear analytical methods. II. Improved analysis by PIXE

    International Nuclear Information System (INIS)

    Preoteasa, E.A.; Ciortea, C.; Fluerasu, D.; Enescu, S.E.; Preoteasa, Elena

    2000-01-01

    In the corrosive environment of the mouth, a diversity of interactions take place at the solid-solid and solid-liquid interfaces of a tooth's filling. Moreover, the mineral elements of the restorative material may induce a complex response of the organism. The approach of these problems requires sensitive surface elemental analysis of the composite and of the dental enamel and dentine. Particle-induced X-ray emission (PIXE) is such a method and has been applied in investigations of hard dental tissues; however, it was not used so far in the study of dental composites. We continue our study by evaluating the potential of PIXE for analysis of these materials. Three types of composites with two color shades each have been studied. The measurements were performed with 3 MeV protons, using a hyperpure Ge detector in a spectroscopic chain connected to a computer. The spectra were processed with the dedicated program Leone. PIXE without additional Al absorbent foil allowed the detection of Z > 14 elements in composites. In two glass- and ceramics-based materials we found: Ca, Zr, Ba, Yb and traces of Sr and In in Tetric Ceram (Vivadent); and Ca, Zr, Ba, Hf, possibly Mn, and traces of Ni, Ho, Ti, Fe, Cr in Valux Plus (3M Dental), after elimination of the escape peaks. In quartz-based Evicrol (Spofa), Si, Ca, Ti, Fe and traces of K, Cr, Ni, Cu, Zn were seen. Materials with different color shades showed variations of Ti, Cr, Fe, Ni and Cu in Evicrol, as contrasted to Tetric Ceram and Valux Plus whose spectra were color-invariant. By its sensitivity and low background, PIXE enables the detection of many trace elements in dental composites; it could serve also in new materials' development and forensic expertise. (authors)

  12. Analysis of oral microbiota in children with dental caries by PCR-DGGE and barcoded pyrosequencing.

    Science.gov (United States)

    Ling, Zongxin; Kong, Jianming; Jia, Peng; Wei, Chaochun; Wang, Yuezhu; Pan, Zhiwen; Huang, Wujing; Li, Lanjuan; Chen, Hui; Xiang, Charlie

    2010-10-01

    Oral microbiota plays a vital role in maintaining the homeostasis of oral cavity. Dental caries are among the most common oral diseases in children and pathogenic bacteria contribute to the development of the disease. However, the overall structure of bacterial communities in the oral cavity from children with dental caries has not been explored deeply heretofore. We used high-throughput barcoded pyrosequencing and PCR-denaturing gradient gel electrophoresis (DGGE) to examine bacterial diversity of oral microbiota in saliva and supragingival plaques from 60 children aged 3 to 6 years old with and without dental caries from China. The multiplex barcoded pyrosequencing was performed in a single run, with multiple samples tagged uniquely by multiplex identifiers. As PCR-DGGE analysis is a conventional molecular ecological approach, this analysis was also performed on the same samples and the results of both approaches were compared. A total of 186,787 high-quality sequences were obtained for evaluating bacterial diversity and 41,905 unique sequences represented all phylotypes. We found that the oral microbiota in children was far more diverse than previous studies reported, and more than 200 genera belonging to ten phyla were found in the oral cavity. The phylotypes in saliva and supragingival plaques were significantly different and could be divided into two distinct clusters (p oral microbiome analyzed by PCR-DGGE and barcoded pyrosequencing was employed to cross validate the data sets. The genera of Streptococcus, Veillonella, Actinomyces, Granulicatella, Leptotrichia, and Thiomonas in plaques were significantly associated with dental caries (p oral microbiota allowed for a better understanding of oral microecosystem, and these pathogenic populations in plaque provide new insights into the etiology of dental caries and suggest new targets for interventions of the disease.

  13. A comparative analysis of exposure doses between the radiation workers in dental and general hospital

    International Nuclear Information System (INIS)

    Yang, Nam Hee; Chung, Woon Kwan; Dong, Kyung Rae; Ju, Yong Jin; Song, Ha Jin; Choi, Eun Jin

    2015-01-01

    Research and investigation is required for the exposure dose of radiation workers to work in the dental hospital as increasing interest in exposure dose of the dental hospital recently accordingly, study aim to minimize radiation exposure by making a follow-up study of individual exposure doses of radiation workers, analyzing the status on individual radiation exposure management, prediction the radiation disability risk levels by radiation, and alerting the workers to the danger of radiation exposure. Especially given the changes in the dental hospital radiation safety awareness conducted the study in order to minimize radiation exposure. This study performed analyses by a comparison between general and dental hospital, comparing each occupation, with the 116,220 exposure dose data by quarter and year of 5,811 subjects at general and dental hospital across South Korea from January 1, 2008 through December 31, 2012. The following are the results obtained by analyzing average values year and quarter. In term of hospital, average doses were significantly higher in general hospitals than detal ones. In terms of job, average doses were higher in radiological technologists the other workers. Especially, they showed statistically significant differences between radiological technologists than dentists. The above-mentioned results indicate that radiation workers were exposed to radiation for the past 5 years to the extent not exceeding the dose limit (maximum 50 mSv y -1 ). The limitation of this study is that radiation workers before 2008 were excluded from the study. Objective evaluation standards did not apply to the work circumstance or condition of each hospital. Therefore, it is deemed necessary to work out analysis criteria that will be used as objective evaluation standard. It will be necessary to study radiation exposure in more precise ways on the basis of objective analysis standard in the future. Should try to minimize the radiation individual dose of

  14. A comparative analysis of exposure doses between the radiation workers in dental and general hospital

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Nam Hee; Chung, Woon Kwan; Dong, Kyung Rae; Ju, Yong Jin; Song, Ha Jin [Dept. of Nuclear Engineering, Chosun University, Gwangju (Korea, Republic of); Choi, Eun Jin [Dept. of Public Health and Medicine, Dongshin University, Naju (Korea, Republic of)

    2015-02-15

    Research and investigation is required for the exposure dose of radiation workers to work in the dental hospital as increasing interest in exposure dose of the dental hospital recently accordingly, study aim to minimize radiation exposure by making a follow-up study of individual exposure doses of radiation workers, analyzing the status on individual radiation exposure management, prediction the radiation disability risk levels by radiation, and alerting the workers to the danger of radiation exposure. Especially given the changes in the dental hospital radiation safety awareness conducted the study in order to minimize radiation exposure. This study performed analyses by a comparison between general and dental hospital, comparing each occupation, with the 116,220 exposure dose data by quarter and year of 5,811 subjects at general and dental hospital across South Korea from January 1, 2008 through December 31, 2012. The following are the results obtained by analyzing average values year and quarter. In term of hospital, average doses were significantly higher in general hospitals than detal ones. In terms of job, average doses were higher in radiological technologists the other workers. Especially, they showed statistically significant differences between radiological technologists than dentists. The above-mentioned results indicate that radiation workers were exposed to radiation for the past 5 years to the extent not exceeding the dose limit (maximum 50 mSv y{sup -1}). The limitation of this study is that radiation workers before 2008 were excluded from the study. Objective evaluation standards did not apply to the work circumstance or condition of each hospital. Therefore, it is deemed necessary to work out analysis criteria that will be used as objective evaluation standard. It will be necessary to study radiation exposure in more precise ways on the basis of objective analysis standard in the future. Should try to minimize the radiation individual dose of

  15. Dental Amalgam

    Science.gov (United States)

    ... Products and Medical Procedures Dental Devices Dental Amalgam Dental Amalgam Share Tweet Linkedin Pin it More sharing options Linkedin Pin it Email Print Dental amalgam is a dental filling material which is ...

  16. Curing kinetics of visible light curing dental resin composites investigated by dielectric analysis (DEA).

    Science.gov (United States)

    Steinhaus, Johannes; Hausnerova, Berenika; Haenel, Thomas; Großgarten, Mandy; Möginger, Bernhard

    2014-03-01

    During the curing process of light curing dental composites the mobility of molecules and molecule segments is reduced leading to a significant increase of the viscosity as well as the ion viscosity. Thus, the kinetics of the curing behavior of 6 different composites was derived from dielectric analysis (DEA) using especially redesigned flat sensors with interdigit comb electrodes allowing for irradiation at the top side and measuring the ion viscosity at the bottom side. As the ion viscosities of dental composites change 1-3 orders of magnitude during the curing process, DEA provides a sensitive approach to evaluate their curing behavior, especially in the phase of undisturbed chain growth. In order to determine quantitative kinetic parameters a kinetic model is presented and examined for the evaluation of the ion viscosity curves. From the obtained results it is seen that DEA might be employed in the investigation of the primary curing process, the quality assurance of ingredients as well as the control of processing stability of the light curing dental composites. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  17. Do sensation differences exist between dental implants and natural teeth?: a meta-analysis.

    Science.gov (United States)

    Higaki, Nobuaki; Goto, Takaharu; Ishida, Yuichi; Watanabe, Megumi; Tomotake, Yoritoki; Ichikawa, Tetsuo

    2014-11-01

    The purpose of this systematic review was to survey evidence pertaining to the sensation differences between natural teeth and osseointegrated dental implants. Using the MEDLINE (online PubMed) database, Cochrane Library, and Scientific Citation index, we performed a systematic search of articles. We used the following search terms: "perception or sensation and dental implant." The systematic review of the extracted articles was performed to see the sensation differences between natural teeth and dental implants. A total of six studies on oral sensation, "tactile sensibility," and "thickness discrimination" were included in the meta-analysis. As to the "tactile sensibility", all studies indicated the threshold levels of the implants were about 4-20 times higher than that of natural teeth. The tactile sensibility of an implant was significantly higher than that of a natural tooth, with an standardized mean difference (SMD) of 8.3619 (95% CI, 6.3920-10.3317) and a P sensation differences between dental implants and natural teeth exist. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  18. Factors associated with unmet dental care needs in Canadian immigrants: an analysis of the longitudinal survey of immigrants to Canada.

    Science.gov (United States)

    Calvasina, Paola; Muntaner, Carles; Quiñonez, Carlos

    2014-12-03

    Immigrants are often considered to have poorer oral health than native born-populations. One possible explanation for immigrants' poor oral health is lack of access to dental care. There is very little information on Canadian immigrants' access to dental care, and unmet dental care needs. This study examines predictors of unmet dental care needs among a sample of adult immigrants to Canada over a three-point-five-year post-migration period. A secondary data analysis was conducted on the Longitudinal Survey of Immigrants to Canada (LSIC). Sampling and bootstrap weights were applied to make the data nationally representative. Simple descriptive analyses were conducted to describe the demographic characteristics of the sample. Bivariate and multiple logistic regression analyses were applied to identify factors associated with immigrants' unmet dental care needs over a three-point-five-year period. Approximately 32% of immigrants reported unmet dental care needs. Immigrants lacking dental insurance (OR = 2.63; 95% CI: 2.05-3.37), and those with an average household income of $20,000 to $40,000 per year (OR = 1.62; 95% CI: 1.01-2.61), and lower than $20,000 (OR = 2.25; 95% CI: 1.31-3.86), were more likely to report unmet dental care needs than those earning more than $60,000 per year. In addition, South Asian (OR = 1.85; CI: 1.25-2.73) and Chinese (OR = 2.17; CI: 1.47-3.21) immigrants had significantly higher odds of reporting unmet dental care needs than Europeans. Lack of dental insurance, low income and ethnicity predicted unmet dental care needs over a three-point-five-year period in a sample of immigrants to Canada.

  19. Time and cost analysis: pediatric dental rehabilitation with general anesthesia in the office and the hospital settings.

    Science.gov (United States)

    Rashewsky, Stephanie; Parameswaran, Ashish; Sloane, Carole; Ferguson, Fred; Epstein, Ralph

    2012-01-01

    Pediatric dental patients who cannot receive dental care in the clinic due to uncooperative behavior are often referred to receive dental care under general anesthesia (GA). At Stony Brook Medicine, dental patients requiring treatment with GA receive dental care in our outpatient facility at the Stony Brook School of Dental Medicine (SDM) or in the Stony Brook University Hospital ambulatory setting (SBUH). This study investigates the time and cost for ambulatory American Society of Anesthesiologists (ASA) Class I pediatric patients receiving full-mouth dental rehabilitation using GA in these 2 locations, along with a descriptive analysis of the patients and dental services provided. In this institutional review board-approved cross-sectional retrospective study, ICD-9 codes for dental caries (521.00) were used to collect patient records between July 2009 and May 2011. Participants were limited to ASA I patients aged 36-60 months. Complete records from 96 patients were reviewed. There were significant differences in cost, total anesthesia time, and recovery room time (P average total time (anesthesia end time minus anesthesia start time) to treat a child at SBUH under GA was 222 ± 62.7 minutes, and recovery time (time of discharge minus anesthesia end time) was 157 ± 97.2 minutes; the average total cost was $7,303. At the SDM, the average total time was 175 ± 36.8 minutes, and recovery time was 25 ± 12.7 minutes; the average total cost was $414. After controlling for anesthesia time and procedures, we found that SBUH cost 13.2 times more than SDM. This study provides evidence that ASA I pediatric patients can receive full-mouth dental rehabilitation utilizing GA under the direction of dentist anesthesiologists in an office-based dental setting more quickly and at a lower cost. This is very promising for patients with the least access to care, including patients with special needs and lack of insurance.

  20. INTERFACE RESIDUAL STRESSES IN DENTAL ZIRCONIA USING LAUE MICRO-DIFFRACTION

    International Nuclear Information System (INIS)

    Bale, H. A.; Tamura, N.; Coelho, P.G.; Hanan, J. C.

    2009-01-01

    Due to their aesthetic value and high compressive strength, dentists have recently employed ceramics for restoration materials. Among the ceramic materials, zirconia provides high toughness and crack resistant characteristics. Residual stresses develop in processing due to factors including grain anisotropy and thermal coefficient mismatch. In the present study, polychromatic X-ray (Laue) micro-diffraction provided grain orientation and residual stresses on a clinically relevant zirconia model ceramic disk. A 0.5 mm x 0.024 mm region on zirconia was examined on a 500 nm scale for residual stresses using a focused poly-chromatic synchrotron X-ray beam. Large stresses ranging from - to + 1GPa were observed at some grains. On average, the method suggests a relatively small compressive stress at the surface between 47 and 75 MPa depending on direction

  1. The Stress and Stiffness Analysis of Diaphragm

    Directory of Open Access Journals (Sweden)

    Qu Dongyue

    2017-01-01

    Full Text Available Diaphragm coupling with its simple structure, small size, high reliability, which can compensate for its input and output displacement deviation by its elastic deformation, is widely used in aerospace, marine, and chemical etc. This paper uses the ANSYS software and its APDL language to analysis the stress distribution when the diaphragm under the load of torque, axial deviation, centrifugal force, angular deviation and multiple loads. We find that the value of maximum stress usually appears in the outer or inner transition region and the axial deviation has a greater influence to the distribution of the stress. Based on above, we got three kinds of stiffness for axial, angular and torque, which the stiffness of diaphragm is nearly invariable. The results can be regard as an important reference for design and optimization of diaphragm coupling.

  2. PDX toroidal field coils stress analysis

    International Nuclear Information System (INIS)

    Nikodem, Z.D.; Smith, R.A.

    1975-01-01

    A method used in the stress analysis of the PDX toroidal field coil is developed. A multilayer coil design of arbitrary dimensions in the shape of either a circle or an oval is considered. The analytical model of the coil and the supporting coil case with connections to the main support structure is analyzed using the finite element technique. The three dimensional magnetic fields and the non-uniform body forces which are a loading condition on a coil due to toroidal and poloidal fields are calculated. The method of analysis permits rapid and economic evaluations of design changes in coil geometry as well as in coil support structures. Some results pertinent to the design evolution and their comparison are discussed. The results of the detailed stress analysis of the final coil design due to toroidal field, poloidal field and temperature loads are presented

  3. Finite element analysis of maxillary bone stress caused by Aramany Class IV obturator prostheses.

    Science.gov (United States)

    Miyashita, Elcio Ricardo; Mattos, Beatriz Silva Câmara; Noritomi, Pedro Yoshito; Navarro, Hamilton

    2012-05-01

    The retention of an Aramany Class IV removable partial dental prosthesis can be compromised by a lack of support. The biomechanics of this obturator prosthesis result in an unusual stress distribution on the residual maxillary bone. This study evaluated the biomechanics of an Aramany Class IV obturator prosthesis with finite element analysis and a digital 3-dimensional (3-D) model developed from a computed tomography scan; bone stress was evaluated according to the load placed on the prosthesis. A 3-D model of an Aramany Class IV maxillary resection and prosthesis was constructed. This model was used to develop a finite element mesh. A 120 N load was applied to the occlusal and incisal platforms corresponding to the prosthetic teeth. Qualitative analysis was based on the scale of maximum principal stress; values obtained through quantitative analysis were expressed in MPa. Under posterior load, tensile and compressive stresses were observed; the tensile stress was greater than the compressive stress, regardless of the bone region, and the greatest compressive stress was observed on the anterior palate near the midline. Under an anterior load, tensile stress was observed in all of the evaluated bone regions; the tensile stress was greater than the compressive stress, regardless of the bone region. The Aramany Class IV obturator prosthesis tended to rotate toward the surgical resection when subjected to posterior or anterior loads. The amount of tensile and compressive stress caused by the Aramany Class IV obturator prosthesis did not exceed the physiological limits of the maxillary bone tissue. (J Prosthet Dent 2012;107:336-342). Copyright © 2012 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  4. Photoelastic stress analysis in mitred bend under internal pressure

    International Nuclear Information System (INIS)

    Sawa, Yoshiaki

    1987-01-01

    The stress analysis and stress relaxation in mitred bend subjected to internal pressure have been studied by means of the photoelastic stress freezing method. The experimental results show that stress concentration occurs in the wedge tip of the intersectional plane and it is considerably influenced by the bent angle. Then, the stress relaxation was obtained by planing the wedge tip. (author)

  5. Complete stress tensor determination by microearthquake analysis

    Science.gov (United States)

    Slunga, R.

    2010-12-01

    the depth based on the assumptions of a fractured crust, widely vary ing stress field, and a general closeness to instability as found by stress measurements (Jamison and Cook 1976). Wheather this approach is working or not is best answered by applying it to real data. This was provided by the IMO network in Iceland. Along Southern Iceland Seismic Zone (SISZ) more than 200,000 microearthquakes and a few M 5 EQs and 2 M=6.6 EQs have been recorded. The results will be presented it is obvious that the use of the stresses determined from the microearthquake recordings may significa ntly improve earthquake warnings and will make it possible to use the absolute C FS method for more deterministic predictions. Note that the microearthquake meth od only shows the part of the stress field that has caused slip. Volumes with st able stress will not show up. However stress measurements (Brown and Hoek 1978, Slunga 1988) have shown that the crustal stresses in general are close to instabi lity and microearthquake source analysis has shown that a large number of differ ent fractures become unstable within longer time windows. This may explain the e xcellent results given by the Icelandic tests of the absolute stress tensor fiel d as given by the microearthquakes. However I prefer to call this stress apparen t.

  6. Repeat film analysis and its implications for quality assurance in dental radiology: An institutional case study

    Directory of Open Access Journals (Sweden)

    Shruthi Acharya

    2015-01-01

    Full Text Available Context: The goal of any radiologist is to produce the highest quality diagnostic radiographs, while keeping patient exposure as low as reasonably achievable (ALARA. Aims: The aim of this study was to describe the reasons for radiograph rejections through a repeat film analysis in an Indian dental school. Settings and Design: An observational study conducted in the Department of Oral Medicine and Radiology, Manipal College of Dental Sciences, Manipal. Materials and Methods: During a 6-month study period, a total of 9,495 intra-oral radiographs and 2339 extraoral radiographs taken in the Radiology Department were subjected to repeat film analysis. Statistical Analysis Used: SPSS Version 16. Descriptive analysis used. Results: The results showed that the repeat rates were 7.1% and 5.86% for intraoral and extraoral radiographs, respectively. Among the causes for errors reported, positioning error (38.7% was the most common, followed by improper angulations (26.1%, and improper film placement (11.2% for intra-oral radiographs. The study found that the maximum frequency of repeats among extraoral radiographs was for panoramic radiographs (49% followed by lateral cephalogram (33%, and paranasal sinus view (14%. It was also observed that repeat rate of intraoral radiographs was highest for internees (44.7%, and undergraduate students (28.2%. Conclusions: The study pointed to a need for more targeted interventions to achieve the goal of keeping patient exposure ALARA in a dental school setting.

  7. A three-dimensional finite element analysis for overdenture attachments supported by teeth and/or mini dental implants.

    Science.gov (United States)

    Fatalla, Abdalbseet A; Song, Ke; Du, Tianfeng; Cao, Yingguang

    2012-12-01

    The aim of this study was to establish the optimum design and attachment combination to support an overdenture with minimal stress and flexing produced in the alveolar bone surrounding any natural teeth and/or mini dental implants. Twelve models were included in the study: the six main models (A, B, C, D, E, and F) were categorized according to the support designs of the overdenture prosthesis, and each model was further subdivided according to the attachment combinations into model 1: with Dalbo elliptic and/or O-ring attachments only and model 2: with flexible acrylic attachments. Vertical loads (35 N) and 17.5 N lateral loads under static conditions were applied to the models to simulate the occlusal forces following the concept of lingualized occlusion. All conditions were created using a finite element software program. Maximum von Mises stress at the level of the attachments and at the bone support foundation interfaces were compared in all 12 models. The flexing of the mandible and the attachments were also compared qualitatively. Stress on these models was analyzed after the given loading condition. The results showed that the model with three freestanding mini dental implants and flexible acrylic attachments showed the lowest von Mises stress and flexing, while the models with four freestanding mini dental implants and O-ring attachments showed the highest von Mises stress. Three freestanding mini dental implants with flexible acrylic attachment systems supporting an overdenture were better choices than four mini dental implants with O-ring attachment systems, which showed the maximum flexing and stress values in this qualitative comparison. © 2012 by the American College of Prosthodontists.

  8. An analysis of moderate sedation protocols used in dental specialty programs: a retrospective observational study.

    Science.gov (United States)

    Setty, Madhavi; Montagnese, Thomas A; Baur, Dale; Aminoshariae, Anita; Mickel, Andre

    2014-09-01

    Pain and anxiety control is critical in dental practice. Moderate sedation is a useful adjunct in managing a variety of conditions that make it difficult or impossible for some people to undergo certain dental procedures. The purpose of this study was to analyze the sedation protocols used in 3 dental specialty programs at the Case Western Reserve University School of Dental Medicine, Cleveland, OH. A retrospective analysis was performed using dental school records of patients receiving moderate sedation in the graduate endodontic, periodontic, and oral surgery programs from January 1, 2010, to December 31, 2012. Information was gathered and the data compiled regarding the reasons for sedation, age, sex, pertinent medical conditions, American Society of Anesthesiologists physical status classifications, routes of administration, drugs, dosages, failures, complications, and other information that was recorded. The reasons for the use of moderate sedation were anxiety (54%), local anesthesia failures (15%), fear of needles (15%), severe gag reflex (8%), and claustrophobia with the rubber dam (8%). The most common medical conditions were hypertension (17%), asthma (15%), and bipolar disorder (8%). Most patients were classified as American Society of Anesthesiologists class II. More women (63.1%) were treated than men (36.9%). The mean age was 45 years. Monitoring and drugs varied among the programs. The most common tooth treated in the endodontic program was the mandibular molar. There are differences in the moderate sedation protocols used in the endodontic, periodontic, and oral surgery programs regarding monitoring, drugs used, and record keeping. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  9. Quantitative Analysis of Diverse Lactobacillus Species Present in Advanced Dental Caries

    OpenAIRE

    Byun, Roy; Nadkarni, Mangala A.; Chhour, Kim-Ly; Martin, F. Elizabeth; Jacques, Nicholas A.; Hunter, Neil

    2004-01-01

    Our previous analysis of 65 advanced dental caries lesions by traditional culture techniques indicated that lactobacilli were numerous in the advancing front of the progressive lesion. Production of organic acids by lactobacilli is considered to be important in causing decalcification of the dentinal matrix. The present study was undertaken to define more precisely the diversity of lactobacilli found in this environment and to quantify the major species and phylotypes relative to total load o...

  10. A three-dimensional finite element study on the effect of hydroxyapatite coating thickness on the stress distribution of the surrounding dental implant-bone interface

    Directory of Open Access Journals (Sweden)

    Hadi Asgharzadeh Shirazi

    2014-06-01

    Full Text Available   Background and Aims: Hydroxyapatite coating has allocated a special place in dentistry due to its biocompatibility and bioactivity. The purpose of this study was to evaluate the relation between the hydroxyapatite thickness and stress distribution by using finite element method.   Materials and Methods: In this paper, the effect of hydroxyapatite coating thickness on dental implants was studied using finite element method in the range between 0 to 200 microns. A 3D model including one section of mandible bone was modeled by a thick layer of cortical surrounding dense cancellous and a Nobel Biocare commercial brand dental implant was simulated and analyzed under static load in the Abaqus software.   Results The diagram of maximum von Mises stress versus coating thickness was plotted for the cancellous and cortical bones in the range between 0 to 200 microns. The obtained results showed that the magnitude of maximum von Mises stress of bone decreased as the hydroxyapatite coating thickness increased. Also, the thickness of coating exhibited smoother stress distribution and milder variations of maximum von Mises stress in a range between 60 to 120 microns.   Conclusion: In present study, the stress was decreased in the mandible bone where hydroxyapatite coating was used. This stress reduction leads to a faster stabilization and fixation of implant in the mandible bone. Using hydroxyapatite coating as a biocompatible and bioactive material could play an important role in bone formation of implant- bone interface.

  11. Chemical Differentiation of Osseous, Dental, and Non-skeletal Materials in Forensic Anthropology using Elemental Analysis.

    Science.gov (United States)

    Zimmerman, Heather A; Meizel-Lambert, Cayli J; Schultz, John J; Sigman, Michael E

    2015-03-01

    Forensic anthropologists are generally able to identify skeletal materials (bone and tooth) using gross anatomical features; however, highly fragmented or taphonomically altered materials may be problematic to identify. Several chemical analysis techniques have been shown to be reliable laboratory methods that can be used to determine if questionable fragments are osseous, dental, or non-skeletal in nature. The purpose of this review is to provide a detailed background of chemical analysis techniques focusing on elemental compositions that have been assessed for use in differentiating osseous, dental, and non-skeletal materials. More recently, chemical analysis studies have also focused on using the elemental composition of osseous/dental materials to evaluate species and provide individual discrimination, but have generally been successful only in small, closed groups, limiting their use forensically. Despite significant advances incorporating a variety of instruments, including handheld devices, further research is necessary to address issues in standardization, error rates, and sample size/diversity. Copyright © 2014 Forensic Science Society. Published by Elsevier Ireland Ltd. All rights reserved.

  12. Does audiovisual distraction reduce dental anxiety in children under local anesthesia? A systematic review and meta-analysis.

    Science.gov (United States)

    Zhang, Cai; Qin, Dan; Shen, Lu; Ji, Ping; Wang, Jinhua

    2018-03-02

    To perform a systematic review and meta-analysis on the effects of audiovisual distraction on reducing dental anxiety in children during dental treatment under local anesthesia. The authors identified eligible reports published through August 2017 by searching PubMed, EMBASE, and Cochrane Central Register of Controlled Trials. Clinical trials that reported the effects of audiovisual distraction on children's physiological measures, self-reports and behavior rating scales during dental treatment met the minimum inclusion requirements. The authors extracted data and performed a meta-analysis of appropriate articles. Nine eligible trials were included and qualitatively analyzed; some of these trials were also quantitatively analyzed. Among the physiological measures, heart rate or pulse rate was significantly lower (p=0.01) in children subjected to audiovisual distraction during dental treatment under local anesthesia than in those who were not; a significant difference in oxygen saturation was not observed. The majority of the studies using self-reports and behavior rating scales suggested that audiovisual distraction was beneficial in reducing anxiety perception and improving children's cooperation during dental treatment. The audiovisual distraction approach effectively reduces dental anxiety among children. Therefore, we suggest the use of audiovisual distraction when children need dental treatment under local anesthesia. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  13. Piping stress analysis with personal computers

    International Nuclear Information System (INIS)

    Revesz, Z.

    1987-01-01

    The growing market of the personal computers is providing an increasing number of professionals with unprecedented and surprisingly inexpensive computing capacity, which if using with powerful software, can enhance immensely the engineers capabilities. This paper focuses on the possibilities which opened in piping stress analysis by the widespread distribution of personal computers, on the necessary changes in the software and on the limitations of using personal computers for engineering design and analysis. Reliability and quality assurance aspects of using personal computers for nuclear applications are also mentioned. The paper resumes with personal views of the author and experiences gained during interactive graphic piping software development for personal computers. (orig./GL)

  14. In vitro fatigue tests and in silico finite element analysis of dental implants with different fixture/abutment joint types using computer-aided design models.

    Science.gov (United States)

    Yamaguchi, Satoshi; Yamanishi, Yasufumi; Machado, Lucas S; Matsumoto, Shuji; Tovar, Nick; Coelho, Paulo G; Thompson, Van P; Imazato, Satoshi

    2018-01-01

    The aim of this study was to evaluate fatigue resistance of dental fixtures with two different fixture-abutment connections by in vitro fatigue testing and in silico three-dimensional finite element analysis (3D FEA) using original computer-aided design (CAD) models. Dental implant fixtures with external connection (EX) or internal connection (IN) abutments were fabricated from original CAD models using grade IV titanium and step-stress accelerated life testing was performed. Fatigue cycles and loads were assessed by Weibull analysis, and fatigue cracking was observed by micro-computed tomography and a stereomicroscope with high dynamic range software. Using the same CAD models, displacement vectors of implant components were also analyzed by 3D FEA. Angles of the fractured line occurring at fixture platforms in vitro and of displacement vectors corresponding to the fractured line in silico were compared by two-way ANOVA. Fatigue testing showed significantly greater reliability for IN than EX (pimplant fixture platforms. FEA demonstrated that crack lines of both implant systems in vitro were observed in the same direction as displacement vectors of the implant fixtures in silico. In silico displacement vectors in the implant fixture are insightful for geometric development of dental implants to reduce complex interactions leading to fatigue failure. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  15. Visualizing the dental biofilm matrix by means of fluorescence lectin-binding analysis

    DEFF Research Database (Denmark)

    Tawakoli, Pune Nina; Neu, Thomas R; Busck, Mette Marie

    2017-01-01

    lectins to visualize and quantify extracellular glycoconjugates in dental biofilms. Lectin binding was screened on pooled supragingival biofilm samples collected from 76 subjects using confocal microscopy. FLBA was then performed with 10 selected lectins on biofilms grown in situ for 48 h in the absence......The extracellular matrix is a poorly studied, yet important component of dental biofilms. Fluorescence lectin-binding analysis (FLBA) is a powerful tool to characterize glycoconjugates in the biofilm matrix. This study aimed to systematically investigate the ability of 75 fluorescently labeled......-biofilms: Aleuria aurantia (AAL), Calystega sepiem (Calsepa), Lycopersicon esculentum (LEA), Morniga-G (MNA-G) and Helix pomatia (HPA). No significant correlation between the binding of specific lectins and bacterial composition was found. Fluorescently labeled lectins enable the visualization of glycoconjugates...

  16. Atomic force microscopy analysis of different surface treatments of Ti dental implant surfaces

    International Nuclear Information System (INIS)

    Bathomarco, R.V.; Solorzano, G.; Elias, C.N.; Prioli, R.

    2004-01-01

    The surface of commercial unalloyed titanium, used in dental implants, was analyzed by atomic force microscopy. The morphology, roughness, and surface area of the samples, submitted to mechanically-induced erosion, chemical etching and a combination of both, were compared. The results show that surface treatments strongly influence the dental implant physical and chemical properties. An analysis of the length dependence of the implant surface roughness shows that, for scan sizes larger than 50 μm, the average surface roughness is independent of the scanning length and that the surface treatments lead to average surface roughness in the range of 0.37 up to 0.48 μm. It is shown that the implant surface energy is sensitive to the titanium surface area. As the area increases there is a decrease in the surface contact angle

  17. Atomic force microscopy analysis of different surface treatments of Ti dental implant surfaces

    Science.gov (United States)

    Bathomarco, Ti R. V.; Solorzano, G.; Elias, C. N.; Prioli, R.

    2004-06-01

    The surface of commercial unalloyed titanium, used in dental implants, was analyzed by atomic force microscopy. The morphology, roughness, and surface area of the samples, submitted to mechanically-induced erosion, chemical etching and a combination of both, were compared. The results show that surface treatments strongly influence the dental implant physical and chemical properties. An analysis of the length dependence of the implant surface roughness shows that, for scan sizes larger than 50 μm, the average surface roughness is independent of the scanning length and that the surface treatments lead to average surface roughness in the range of 0.37 up to 0.48 μm. It is shown that the implant surface energy is sensitive to the titanium surface area. As the area increases there is a decrease in the surface contact angle.

  18. Analysis of gene expression during odontogenic differentiation of cultured human dental pulp cells

    Directory of Open Access Journals (Sweden)

    Min-Seock Seo

    2012-08-01

    Full Text Available Objectives We analyzed gene-expression profiles after 14 day odontogenic induction of human dental pulp cells (DPCs using a DNA microarray and sought candidate genes possibly associated with mineralization. Materials and Methods Induced human dental pulp cells were obtained by culturing DPCs in odontogenic induction medium (OM for 14 day. Cells exposed to normal culture medium were used as controls. Total RNA was extracted from cells and analyzed by microarray analysis and the key results were confirmed selectively by reverse-transcriptase polymerase chain reaction (RT-PCR. We also performed a gene set enrichment analysis (GSEA of the microarray data. Results Six hundred and five genes among the 47,320 probes on the BeadChip differed by a factor of more than two-fold in the induced cells. Of these, 217 genes were upregulated, and 388 were down-regulated. GSEA revealed that in the induced cells, genes implicated in Apoptosis and Signaling by wingless MMTV integration (Wnt were significantly upregulated. Conclusions Genes implicated in Apoptosis and Signaling by Wnt are highly connected to the differentiation of dental pulp cells into odontoblast.

  19. Mineral elements in dental composites by atomic and nuclear analytical methods. I. Fast analysis by XRY

    International Nuclear Information System (INIS)

    Preoteasa, E.A.; Constantinescu, B.; Preoteasa, Elena

    2000-01-01

    Composite materials replaced silver amalgam in many applications for restorative dentistry. Among biomaterials their production develops at a high rate, due especially to the progress of materials forming their mineral filling. However they bring at the interface with enamel and dentine elements foreign to the organism, of whom not all are specified by manufacturers; also, some of these elements' biological action has not been studied. Due to its ability to analyze the elemental composition at the biomaterial's surface, as well as the concentration changes that may occur in the mouth or in model systems, X-ray fluorescence (XRF) is a method suited to approach such problems. Here we examined the potential of XRF for fast analysis of some dental composite materials. Flat disk-shaped samples have been prepared by polymerization and the measurements have been performed with a spectrometric chain containing a 241 Am source, a Si(Li) detector and a multichannel analyzer. The radioisotope-excited XRF detected the following Z > 20 elements in the studied composite materials: Ba in Charisma (Kulzer) and Pekafill (Bayer); Zr, Ba, Yb [and traces of In] in Tetric Ceram (Vivadent); Zr, Hf in Valux Plus and Sr, Ba and traces of Cu in F2000 compomer (both from 3M Dental). Among older materials, Evicrol (Spofa) and Alphaplast (DGM) showed Ca and Fe, while Concise (3M Dental) contained only undetectable (Z < 20) elements. XRF proved valuable especially for analysis of major and minor inorganic elements in the dental composite materials. The method could be used also in fast expertise of these biomaterials (e.g. in customs and commercial applications). (authors)

  20. Analysis of clinical characteristics, dental treatment performed, and postoperative complications of 200 patients treated under general anesthesia in a special needs dental clinic in northern Taiwan

    Directory of Open Access Journals (Sweden)

    Yi-Chia Wang

    2015-06-01

    Conclusion: Both IGA and NIGA are effective and relatively safe methods for dental patients who need dental treatment in a special needs dental clinic, but anesthesia itself still carries certain risks.

  1. Stress analysis of cylinder to cylinder intersections

    International Nuclear Information System (INIS)

    Revesz, Z.

    1983-01-01

    Cylinder to cylinder intersections have numerous applications in the power industry from different piping junctions to pressure vessel nozzles. A specific purpose computer program has been installed at the author's establishment for finite element analysis of such geometries. Some of the experiences are presented giving a short overview of the analysis of unreinforced man-holes, demonstrating how a more economical design has been verified by analysis. The program installed has linear-elastic and elasto-plastic capabilities. Further, it is prepared for heat transfer analysis with subsequent thermal stress computation. An efficient pre- and post-processor has also been installed and enhanced by the author. The software used is at its present stage capable for problem definition with input data such as outside/ inside diameters, length and number of subdivisions. Similarly simple is the load definition and the graphic representation of the full output. (author)

  2. Psychological stress and health in undergraduate dental students: fifth year outcomes compared with first year baseline results from five European dental schools

    NARCIS (Netherlands)

    Gorter, R.C.; Freeman, R.; Hammen, S.; Murtomaa, H.; Blinkhorn, A.; Humphris, G.

    2008-01-01

    Objective: To compare the levels of a series of health-related indicators from a cohort of fifth year dental students from five European schools with their first year scores, and to investigate the relationship between these follow-up measures. Methods: Burnout was measured using the Maslach Burnout

  3. Fourier Transform Infrared Imaging analysis of dental pulp inflammatory diseases.

    Science.gov (United States)

    Giorgini, E; Sabbatini, S; Conti, C; Rubini, C; Rocchetti, R; Fioroni, M; Memè, L; Orilisi, G

    2017-05-01

    Fourier Transform Infrared microspectroscopy let characterize the macromolecular composition and distribution of tissues and cells, by studying the interaction between infrared radiation and matter. Therefore, we hypothesize to exploit this analytical tool in the analysis of inflamed pulps, to detect the different biochemical features related to various degrees of inflammation. IR maps of 13 irreversible and 12 hyperplastic pulpitis, together with 10 normal pulps, were acquired, compared with histological findings and submitted to multivariate (HCA, PCA, SIMCA) and statistical (one-way ANOVA) analysis. The fit of convoluted bands let calculate meaningful band area ratios (means ± s.d., P < 0.05). The infrared imaging analysis pin-pointed higher amounts of water and lower quantities of type I collagen in all inflamed pulps. Specific vibrational markers were defined for irreversible pulpitis (Lipids/Total Biomass, PhII/Total Biomass, CH 2 /CH 3 , and Ty/AII) and hyperplastic ones (OH/Total Biomass, Collagen/Total Biomass, and CH 3 Collagen/Total Biomass). The study confirmed that FTIR microspectroscopy let discriminate tissues' biological features. The infrared imaging analysis evidenced, in inflamed pulps, alterations in tissues' structure and composition. Changes in lipid metabolism, increasing amounts of tyrosine, and the occurrence of phosphorylative processes were highlighted in irreversible pulpitis, while high amounts of water and low quantities of type I collagen were detected in hyperplastic samples. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  4. Systemic assessment of patients undergoing dental implant surgeries: A trans- and post-operative analysis

    OpenAIRE

    Sanjay Byakodi; Sachin Kumar; Rajesh Kumar Reddy; Vipin Kumar; Shipra Sepolia; Shivangi Gupta; Harkanwal Preet Singh

    2017-01-01

    Background: Procedure-related and patient-related factors influence the prognosis of dental implants to a major extent. Hence, we aimed to evaluate and analyze various systemic factors in patients receiving dental implants. Materials and Methods: Fifty-one patients were included in the study, in which a total of 110 dental implants were placed. Complete examination of the subjects was done before and after placement of dental implants. Implant surgery was planned, and osseointegrated dental i...

  5. Pyrosequencing analysis of oral microbiota in children with severe early childhood dental caries.

    Science.gov (United States)

    Jiang, Wen; Zhang, Jie; Chen, Hui

    2013-11-01

    Severe early childhood caries are a prevalent public health problem among preschool children throughout the world. However, little is known about the microbiota found in association with severe early childhood caries. Our study aimed to explore the bacterial microbiota of dental plaques to study the etiology of severe early childhood caries through pyrosequencing analysis based on 16S rRNA gene V1-V3 hypervariable regions. Forty participants were enrolled in the study, and we obtained twenty samples of supragingival plaque from caries-free subjects and twenty samples from subjects with severe early childhood caries. A total of 175,918 reads met the quality control standards, and the bacteria found belonged to fourteen phyla and sixty-three genera. Our results show the overall structure and microbial composition of oral bacterial communities, and they suggest that these bacteria may present a core microbiome in the dental plaque microbiota. Three genera, Streptococcus, Granulicatella, and Actinomyces, were increased significantly in children with severe dental cavities. These data may facilitate improvements in the prevention and treatment of severe early childhood caries.

  6. Importance-performance analysis of dental satisfaction among three ethnic groups in malaysia.

    Science.gov (United States)

    Dewi, Fellani Danasra; Gundavarapu, Kalyan C; Cugati, Navaneetha

    2013-01-01

    To find the differences in patient satisfaction related to dental services among three ethnic groups - Chinese, Indian and Malay - at AIMST University Dental Centre and analyse them with an importance-performance grid, identifying the weak and strong points, in order to provide better service. This questionnaire-based study consisted of convenience samples of 174 patients of Chinese, Indian and Malay ethnicity. Importance-performance analysis for 20 attributes were compared using Likert's scale. The data obtained were statistically analysed using the Kruskal-Wallis test. Chinese and Indians both emphasised low performance on the interpersonal relationship attribute in terms of the receptionist's courtesy, whereas the Malay participants were concerned with convenience attributes. All the ethnic groups favoured maintaining existing major attributes towards technical competency, interpersonal relationship and facility factors. This study demonstrated priority differences between the ethnic groups' perception of the quality of dental services, where ethnic Chinese showed the highest gap (measure of dissatisfaction) between importance and performance compared to ethnic Malays, followed by ethnic Indians. The patients from the three major ethnic groups of Malaysia were generally well satisfied. Perhaps more priority should be placed on improving the interpersonal relationship attribute, especially with the receptionists.

  7. Dental microwear texture analysis of late Pliocene Procynocephalus subhimalayanus (Primates: Cercopithecidae) of the Upper Siwaliks, India

    Science.gov (United States)

    Williams, Frank L'Engle; Holmes, Noelle A.

    2012-09-01

    Late Pliocene Procynocephalus subhimalayanus from the Upper Siwaliks, India is known from only three specimens. The dietary proclivities of this taxon have implications for reconstructing the paleoecology of the Upper Siwaliks. The dental microwear texture properties of Procynocephalus are compared to those from extant tropical forest primates including Alouatta palliata (n = 11), Cebus apella (n = 13), Gorilla gorilla (n = 9), Lophocebus albigena (n = 15) and Trachypithecus cristatus (n = 12). Dental microwear textures are generated by scanning the surface enamel of Facet 9 using white-light confocal microscopy at 100x. Four variables were extracted from scale-sensitive fractal analysis, and the data were ranked before ANOVA with post-hoc tests of significance and multivariate analyses were performed. Procynocephalus clusters closest to Lophocebus, Cebus and some Gorilla specimens suggesting hard-object feeding characterized a portion of its diet. The dental microwear texture of Procynocephalus supports interpretations of widespread grasslands of the Late Pliocene Kansal Formation (Pinjor zone). The extreme enamel complexity characterizing Procynocephalus may derive from consumption of underground storage organs, or other foods with high grit loads. Foods consumed near ground level carry a heavy load of abrasive minerals possibly contributing to greater enamel surface complexity and textural fill volume.

  8. Measurement of Primary and Secondary Stability of Dental Implants by Resonance Frequency Analysis Method in Mandible

    Science.gov (United States)

    Shokri, Mehran; Daraeighadikolaei, Arash

    2013-01-01

    Background. There is no doubt that the success of the dental implants depends on the stability. The aim of this work was to measure the stability of dental implants prior to loading the implants, using a resonance frequency analysis (RFA) by Osstell mentor device. Methods. Ten healthy and nonsmoker patients over 40 years of age with at least six months of complete or partial edentulous mouth received screw-type dental implants by a 1-stage procedure. RFA measurements were obtained at surgery and 1, 2, 3, 4, 5, 7, and 11 weeks after the implant surgery. Results. Among fifteen implants, the lowest mean stability measurement was for the 4th week after surgery in all bone types. At placement, the mean ISQ obtained with the magnetic device was 77.2 with 95% confidence interval (CI) = 2.49, and then it decreased until the 4th week to 72.13 (95% CI = 2.88), and at the last measurement, the mean implant stability significantly (P value implant placement. These suggestions need to be further assessed through future studies. PMID:23737790

  9. Can conditional health policies be justified? A policy analysis of the new NHS dental contract reforms.

    Science.gov (United States)

    Laverty, Louise; Harris, Rebecca

    2018-06-01

    Conditional policies, which emphasise personal responsibility, are becoming increasingly common in healthcare. Although used widely internationally, they are relatively new within the UK health system where there have been concerns about whether they can be justified. New NHS dental contracts include the introduction of a conditional component that restricts certain patients from accessing a full range of treatment until they have complied with preventative action. A policy analysis of published documents on the NHS dental contract reforms from 2009 to 2016 was conducted to consider how conditionality is justified and whether its execution is likely to cause distributional effects. Contractualist, paternalistic and mutualist arguments that reflect notions of responsibility and obligation are used as justification within policy. Underlying these arguments is an emphasis on preserving the finite resources of a strained NHS. We argue that the proposed conditional component may differentially affect disadvantaged patients, who do not necessarily have access to the resources needed to meet the behavioural requirements. As such, the conditional component of the NHS dental contract reform has the potential to exacerbate oral health inequalities. Conditional health policies may challenge core NHS principles and, as is the case with any conditional policy, should be carefully considered to ensure they do not exacerbate health inequities. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

  10. An analysis of the phenomenon of increased parental participation during the child's dental experience.

    Science.gov (United States)

    Pinkham, J R

    1991-01-01

    The role of the parent during their child's dental experience, in contemporary society, has changed during the past decade and should be addressed by pediatric dentists. Included in this matter are issues regarding risk management and practice management. Behavioral pediatric dentistry is in flux, much like the world that it serves; there appear to be schisms within the profession regarding one aspect of this: the presence of parents in the dental operatory. Presented here is an analysis of the paradigm-shifts in society since World War II, when a postfigurative parenting strategy was in vogue. An explication of noted anthropologist Margaret Mead's descriptions of this and two subsequent parenting styles, including configurative (or transitional) and prefigurative (contemporary) are presented. They are analyzed in terms of parental attitudes concerning trusting their child to authority figures, including the dental clinician. This emerging protective instinct is termed "social hypertrophy", based on social biologist Edward O. Wilson's work. Dentists are encouraged to understand parental attitudes and avoid unnecessary conflict.

  11. A Naval Postgraduate Dental School Analysis of Initial Endodontic Treatment

    Science.gov (United States)

    2013-06-01

    to prevent or heal disease , i.e. apical periodontitis . Accordingly, endodontic treatment outcomes can better be defined in reference to healing and...Janket S, Baird AE, Chuang S, Jones JA. Meta-analysis of periodontal disease risk and risk of coronary heart disease and stroke. Oral Surg Oral Med Oral...appointment endodontic therapy in dogs ’ teeth with apical periodontitis . J Endod 2003;29:121-4. 27. Penesis VA, Fitzgerald PI, Fayad MI, Wenckus

  12. Investigating the "inverse care law" in dental care: A comparative analysis of Canadian jurisdictions.

    Science.gov (United States)

    Dehmoobadsharifabadi, Armita; Singhal, Sonica; Quiñonez, Carlos

    2017-03-01

    To compare physician and dentist visits nationally and at the provincial/territorial level and to assess the extent of the "inverse care law" in dental care among different age groups in the same way. Publicly available data from the 2007 to 2008 Canadian Community Health Survey were utilized to investigate physician and dentist visits in the past 12 months in relation to self-perceived general and oral health by performing descriptive statistics and binary logistic regression, controlling for age, sex, education, income, and physician/dentist population ratios. Analysis was conducted for all participants and stratified by age groups - children (12-17 years), adults (18-64 years) and seniors (65 years and over). Nationally and provincially/territorially, it appears that the "inverse care law" persists for dental care but is not present for physician care. Specifically, when comparing to those with excellent general/oral health, individuals with poor general health were 2.71 (95% confidence interval [CI]: 2.70-2.72) times more likely to visit physicians, and individuals with poor oral health were 2.16 (95% CI: 2.16-2.17) times less likely to visit dentists. Stratified analyses by age showed more variability in the extent of the "inverse care law" in children and seniors compared to adults. The "inverse care law" in dental care exists both nationally and provincially/territorially among different age groups. Given this, it is important to assess the government's role in improving access to, and utilization of, dental care in Canada.

  13. Analysis of clinical records of dental patients attending Jordan University Hospital: Documentation of drug prescriptions and local anesthetic injections

    Directory of Open Access Journals (Sweden)

    Najla Dar-Odeh

    2008-08-01

    Full Text Available Najla Dar-Odeh1, Soukaina Ryalat1, Mohammad Shayyab1, Osama Abu-Hammad21Department of Oral and Maxillofacial Surgery Oral Medicine and Periodontics, Faculty of Dentistry, University of Jordan, Jordan; 2Department of Prosthetic Dentistry, Faculty of Dentistry, University of Jordan, JordanObjectives: The aim of this study was to analyze clinical records of dental patients attending the Dental Department at the University of Jordan Hospital: a teaching hospital in Jordan. Analysis aimed at determining whether dental specialists properly documented the drug prescriptions and local anesthetic injections given to their patients.Methods: Dental records of the Dental Department at the Jordan University Hospital were reviewed during the period from April 3rd until April 26th 2007 along with the issued prescriptions during that period.Results: A total of 1000 records were reviewed with a total of 53 prescriptions issued during that period. Thirty records documented the prescription by stating the category of the prescribed drug. Only 13 records stated the generic or the trade names of the prescribed drugs. Of these, 5 records contained the full elements of a prescription. As for local anesthetic injections, the term “LA used” was found in 22 records while the names and quantities of the local anesthetics used were documented in only 13 records. Only 5 records documented the full elements of a local anesthetic injection.Conclusion: The essential data of drug prescriptions and local anesthetic injections were poorly documented by the investigated group of dental specialists. It is recommended that the administration of the hospital and the dental department implement clear and firm guidelines for dental practitioners in particular to do the required documentation procedure.Keywords: dental records, documentation, prescriptions, local anesthesia

  14. A national analysis of dental waiting lists and point-in-time geographic access to subsidised dental care: can geographic access be improved by offering public dental care through private dental clinics?

    Science.gov (United States)

    Dudko, Yevgeni; Kruger, Estie; Tennant, Marc

    2017-01-01

    Australia is one of the least densely populated countries in the world, with a population concentrated on or around coastal areas. Up to 33% of the Australian population are likely to have untreated dental decay, while people with inadequate dentition (fewer than 21 teeth) account for up to 34% of Australian adults. Historically, inadequate access to public dental care has resulted in long waiting lists, received much media coverage and been the subject of a new federal and state initiative. The objective of this research was to gauge the potential for reducing the national dental waiting list through geographical advantage, which could arise from subcontracting the delivery of subsidised dental care to the existing network of private dental clinics across Australia. Eligible population data were collected from the Australian Bureau of Statistics website. Waiting list data from across Australia were collected from publicly available sources and confirmed through direct communication with each individual state or territory dental health body. Quantum geographic information system software was used to map distribution of the eligible population across Australia by statistical area, and to plot locations of government and private dental clinics. Catchment areas of 5 km for metropolitan clinics and 5 km and 50 km for rural clinics were defined. The number of people on the waiting list and those eligible for subsidised dental care covered by each of the catchment areas was calculated. Percentage of the eligible population and those on the waiting list that could benefit from the potential improvement in geographic access was ascertained for metropolitan and rural residents. Fifty three percent of people on the waiting list resided within metropolitan areas. Rural and remote residents made up 47% of the population waiting to receive care. The utilisation of both government and private dental clinics for the delivery of subsidised dental care to the eligible population

  15. Turned versus anodised dental implants: a meta-analysis.

    Science.gov (United States)

    Chrcanovic, B R; Albrektsson, T; Wennerberg, A

    2016-09-01

    The aim of this meta-analysis was to test the null hypothesis of no difference in the implant failure rates, marginal bone loss (MBL)and post-operative infection for patients being rehabilitated by turned versus anodised-surface implants, against the alternative hypothesis of a difference. An electronic search without time or language restrictions was undertaken in November 2015. Eligibility criteria included clinical human studies, either randomised or not. Thirty-eight publications were included. The results suggest a risk ratio of 2·82 (95% CI 1·95-4·06, P implants, when compared to anodised-surface implants. Sensitivity analyses showed similar results when only the studies inserting implants in maxillae or mandibles were pooled. There were no statistically significant effects of turned implants on the MBL (mean difference-MD 0·02, 95%CI -0·16-0·20; P = 0·82) in comparison to anodised implants. The results of a meta-regression considering the follow-up period as a covariate suggested an increase of the MD with the increase in the follow-up time (MD increase 0·012 mm year(-1) ), however, without a statistical significance (P = 0·813). Due to lack of satisfactory information, meta-analysis for the outcome 'post-operative infection' was not performed. The results have to be interpreted with caution due to the presence of several confounding factors in the included studies. © 2016 John Wiley & Sons Ltd.

  16. Developmental defects of enamel and dental caries in the primary dentition: A systematic review and meta-analysis.

    Science.gov (United States)

    Costa, Francine S; Silveira, Ethieli R; Pinto, Gabriela S; Nascimento, Gustavo G; Thomson, William Murray; Demarco, Flávio F

    2017-05-01

    This systematic review and meta-analysis evaluated the association between developmental defects of enamel and dental caries in the primary dentition. Electronic searches were performed in PubMed, Web of Knowledge, Scopus and Scielo for the identification of relevant studies. Observational studies that examined the association between developmental defects of enamel and dental caries in the deciduous dentition were included. Additionally, meta-analysis, funnel plots and sensitivity analysis were employed to synthesize the available evidence. Multivariable meta-regression analysis was performed to explore heterogeneity among studies. A total of 318 articles were identified in the electronic searches. Of those, 16 studies were included in the meta-analysis. Pooled estimates revealed that children with developmental defects of enamel had higher odds of having dental caries (OR 3.32; 95%CI 2.41-4.57), with high heterogeneity between studies (I 2 80%). Methodological characteristic of the studies, such as where it was conducted, the examined teeth and the quality of the study explained about 30% of the variability. Concerning type of defect, children with hypoplasia and diffuse opacities had higher odds of having dental caries (OR 4.28; 95%CI 2.24-8.15; OR1.42; 95%CI 1.15-1.76, respectively). This systematic review and meta-analysis demonstrates a clear association between developmental defects of enamel and dental caries in the primary dentition. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Modeling the Residual Stresses in Reactive Resins-Based Materials: a Case Study of Photo-Sensitive Composites for Dental Applications

    International Nuclear Information System (INIS)

    Grassia, Luigi; D'Amore, Alberto

    2010-01-01

    Residual stresses in reactive resins-based composites are associated to the net volumetric contraction (shrinkage) arising during the cross-linking reactions. Depending on the restoration geometry (the ratio of the free surface area to the volume of the cavity) the frozen-in stresses can be as high as the strength of the dental composites. This is the main reason why the effectiveness and then the durability of restorations with composites remains quite lower than those realized with metal alloys based materials. In this paper we first explore the possibility to circumvent the mathematical complexity arising from the determination of residual stresses in reactive systems three-dimensionally constrained. Then, the results of our modeling approach are applied to a series of commercially available composites showing that almost all samples develop residual stresses such that the restoration undergoes failure as soon as it is realized.

  18. An investigation into the dental health of children with obesity: an analysis of dental erosion and caries status.

    Science.gov (United States)

    Tong, H J; Rudolf, M C J; Muyombwe, T; Duggal, M S; Balmer, R

    2014-06-01

    To investigate whether children with obesity experienced more erosion and caries than children with normal weight. This study involved children aged 7-15 years. The study and control group comprised 32 children with BMI > 98th centile and 32 healthy children with normal BMI-for-age, respectively. O'Sullivan Erosion Index and WHO Caries Index were used in the examination of erosion and caries, respectively. Stimulated salivary flow rate, buffering capacity, Streptococcus mutans and lactobacilli counts (CFU/ml) were evaluated. A cross-sectional questionnaire survey was employed to collect information on participant's demographic background, oral health history and habits, and utilisation of dental care services. Children with obesity were more likely to have erosion than healthy children (p erosion in terms of severity (p erosion (OR 0.32, 95 % CI 0.012-0.082). Gender had no effect on erosion. There were no statistically significant differences in the DMFT, saliva profiles or questionnaire responses between the groups. Children with obesity may have high risk of dental erosion, but do not necessarily have higher risk of dental caries than children with normal weight.

  19. Stress Analysis for Mobile Hot Cell Design

    International Nuclear Information System (INIS)

    Muhammad Hannan Bahrin; Anwar Abdul Rahman; Mohd Arif Hamzah

    2015-01-01

    Prototype and Plant Development Centre (PDC) is developing a Mobile Hot Cell (MHC) to handle and manage Spent High Activity Radioactive Sources (SHARS), such as teletherapy heads and dry irradiators. At present, there are two units of MHC in the world, one in South Africa and the other one in China. Malaysian Mobile MHC is developed by Malaysian Nuclear Agency with the assistance of IAEA expert, based on the design of South Africa and China, but with improved features. Stress analysis has been performed on the design to fulfill the safety requirement in MHC operation. This paper discusses the loading effect analysis from the radiation shielding materials to the MHC wall structure, roof supporting column and window structure. (author)

  20. Spartan Release Engagement Mechanism (REM) stress and fracture analysis

    Science.gov (United States)

    Marlowe, D. S.; West, E. J.

    1984-01-01

    The revised stress and fracture analysis of the Spartan REM hardware for current load conditions and mass properties is presented. The stress analysis was performed using a NASTRAN math model of the Spartan REM adapter, base, and payload. Appendix A contains the material properties, loads, and stress analysis of the hardware. The computer output and model description are in Appendix B. Factors of safety used in the stress analysis were 1.4 on tested items and 2.0 on all other items. Fracture analysis of the items considered fracture critical was accomplished using the MSFC Crack Growth Analysis code. Loads and stresses were obtaind from the stress analysis. The fracture analysis notes are located in Appendix A and the computer output in Appendix B. All items analyzed met design and fracture criteria.

  1. Occupational risk for Legionella infection among dental healthcare workers: meta-analysis in occupational epidemiology.

    Science.gov (United States)

    Petti, Stefano; Vitali, Matteo

    2017-07-13

    The occupational risk for Legionella infection among dental healthcare workers (DHCWs) is conjectured because of the risk of routine inhalation of potentially contaminated aerosols produced by the dental instruments. Nevertheless, occupational epidemiology studies are contrasting. This meta-analysis assessed the level of scientific evidence regarding the relative occupational risk for Legionella infection among DHCWs. Literature search was performed without time and language restrictions, using broad data banks (PubMed, Scopus, Web of Science, GOOGLE Scholar) and generic keywords ('legionella' AND 'dent*'). Analytical cross-sectional studies comparing prevalence of high serum Legionella antibody levels in DHCWs and occupationally unexposed individuals were considered. The relative occupational risk was assessed through prevalence ratio (PR) with 95% CI. Between-study heterogeneity was assessed (Cochran's Q test) and was used to choose the meta-analytic method. Study quality (modified Newcastle-Ottawa Scale) and publication bias (Begg and Mazumdar's test, Egger and colleagues' test, trim and fill R 0 method) were assessed formally and considered for the sensitivity analysis. Sensitivity analysis to study inclusion, subgroup analyses (dental staff categories; publication year, before vs after 1998, ie, 5 years after the release by the Centers for Disease Control and Prevention of the infection control guidelines in dental healthcare setting) were performed. Seven studies were included (2232 DHCWs, 1172 occupationally unexposed individuals). No evidence of publication bias was detected. The pooled PR estimate was statistically non-significant at 95% level (1.7; 95% CI 0.8 to 3.2), study-quality adjustment did not change the PR considerably (PR, 1.5; 95% CI 0.5 to 4.1). PR was statistically significant before 1998 and no longer significant after 1998. Subgroup analysis according to DHCW categories was inconclusive. There is no scientific evidence that DHCWs are

  2. Improved PIXE analysis of micro- and trace elements in dental composites

    International Nuclear Information System (INIS)

    Preoteasa, E. A.; Ciortea, C.; Fluerasu, D.; Enescu, S. E.; Preoteasa, E.

    2001-01-01

    Due to the interactions occurring at the solid-solid and solid-liquid interfaces of a tooth's filling, the mineral elements of the restorative composite may induce a complex response of the organism. To study such problems, sensitive surface trace element analysis is required. Particle-induced X-ray emission (PIXE) has a detection limit one order of magnitude lower than XRF and has been used for hard dental tissues, but not yet for dental composites. We evaluated the potential of PIXE in a study of ten types of composites used in restorative dentistry, some of them with two color shades each. The samples were prepared as described for XRF. The measurements were performed with 3 MeV protons from a van de Graaff tandem linear accelerator, using a hyper pure Ge detector and collecting the spectra for 1.5-4 hours. The spectra were processed with the program Leone. The proton route in the sample calculated with the Trim program (∼ 50-100 μm) exceeded the size of mineral particles (0.02-30 μm), thus granularity did not affect the analysis. The PIXE analysis detected Z ≥ 19 elements in all composites, and Z≥14 elements in only one low Z material. PIXE detected generally the same dominant elements, but many more trace elements than XRF. Thus both Charisma (Kulzer) and Pekafill (Bayer) contained Ba as the major element, but trace elements were Ni, Zn, In, in the first, and Fe, Cu, Zn, Sr, Ag in the second. In other glass- and ceramics-based materials we found: Ca, Zr, Ba, Yb and traces of Sr, In, and possibly Ti in Tetric Ceram and in Ariston (both from Vivadent); Ca, Zr, Ba, Hf, possibly Mn, and traces of Ni, Ho, Ti, Fe, Cr in Valux Plus (3M Dental); Sr, Ba (major), K, Fe, Mn (minor), and traces of Ni, Zn, In, in F2000 Compomer (3M Dental); Ba (major) and traces of Fe, Ni, Sr in Surefil (Dentsply). In quartz-based materials we detected: Si, Ca, Ti, Fe and traces of K, Cl, Cr, Ni, Cu, Zn in Evicrol (Spofa); low and trace levels of Ca, Ti, Cr, Mn, Fe, Cu in

  3. Performance of dental impression materials: Benchmarking of materials and techniques by three-dimensional analysis.

    Science.gov (United States)

    Rudolph, Heike; Graf, Michael R S; Kuhn, Katharina; Rupf-Köhler, Stephanie; Eirich, Alfred; Edelmann, Cornelia; Quaas, Sebastian; Luthardt, Ralph G

    2015-01-01

    Among other factors, the precision of dental impressions is an important and determining factor for the fit of dental restorations. The aim of this study was to examine the three-dimensional (3D) precision of gypsum dies made using a range of impression techniques and materials. Ten impressions of a steel canine were fabricated for each of the 24 material-method-combinations and poured with type 4 die stone. The dies were optically digitized, aligned to the CAD model of the steel canine, and 3D differences were calculated. The results were statistically analyzed using one-way analysis of variance. Depending on material and impression technique, the mean values had a range between +10.9/-10.0 µm (SD 2.8/2.3) and +16.5/-23.5 µm (SD 11.8/18.8). Qualitative analysis using colorcoded graphs showed a characteristic location of deviations for different impression techniques. Three-dimensional analysis provided a comprehensive picture of the achievable precision. Processing aspects and impression technique were of significant influence.

  4. Prospective analysis of factors associated with dental behavior management problems, in children aged 7-11 years

    Directory of Open Access Journals (Sweden)

    Ramya Pai

    2015-01-01

    Full Text Available Aim: To determine the prevalence of child behavior management problems (BMP and to analyze the influence and predictive power of nondental and dental background variables on BMP. Study Design: Prospective analytical study. Materials and Methods: The study group included 165 children aged 7-11 years who received comprehensive dental treatment, after obtaining written informed consent. Parents/guardians were interviewed using standardized questionnaire to obtain background information. Each child′s treatment was carried out and was recorded with a fixed digital video (DV recorder. The treatments were classified into three levels of invasiveness: Noninvasive (NI, moderately invasive (MI, and highly invasive (HI. The entire DV record of each treatment was observed, and child′s dental behavior was rated independently by two precalibrated examiners using modified Venham′s behavior rating scale. Then, the background factors obtained through the questionnaire data were analyzed for its association with child′s dental behavior. Results: Statistical tests used were Chi-square test and multiple logistic regression analysis to determine the relationship of multiple variables with dental behavior. Comparison of child′s behavior during different visits was done by Wilcoxan matched pairs test. The prevalence of BMP in children aged 7-11 years in the study sample was 0%, 4.2%, and 15.76% for NI, MI, and HI procedures, respectively. Three variables were significant predictors of behavior; order of birth that is, first born, history of hospitalization, and unpleasant past dental experience (P < 0.05. Conclusions: Direct conditioning pathway is the major factor in determining child′s behavior. Dental experiences, duration of treatment, and complexity of treatment have greater impact on how the child behaves in a dental setup.

  5. Comparative Evaluation of Pediatric Patients with Mental Retardation undergoing Dental Treatment under General Anesthesia: A Retrospective Analysis.

    Science.gov (United States)

    Ahuja, Ravish; Jyoti, Bhuvan; Shewale, Vinod; Shetty, Shridhar; Subudhi, Santosh Kumar; Kaur, Manpreet

    2016-08-01

    Behavioral management of patients forms one of the foremost components of pediatric dental treatment. Some children readily cooperate with dental treatment, while others require general anesthesia as a part of treatment protocol for carrying out various dental procedures. Hence, we evaluated the pediatric patients with and without mental retardation, who underwent dental treatment under general anesthesia. The present study analyzed the record of 480 pediatric patients reporting in the department of pedodontics from 2008 to 2014. Analysis of the records of the patients who underwent dental treatment under general anesthesia was done and all the patients were divided into two study groups depending upon their mental level. For the purpose of evaluation, the patients were also grouped according to their age; 4 to 7 years, 8 to 12 years, and 13 to 18 years. Measurement of decayed, missing, and filled teeth and scores for both deciduous and permanent dentition was done before and after the commencement of the dental treatment. Chi-square test and independent t-test were used for evaluating the level of significance. While comparing the patients in the two groups, maximum number of patients is present in the age group of 13 to 18 years. While comparing the indices' score between the two study groups in various age intervals, no statistically significant results were obtained. Restorative treatment and dental extractions were the most common dental treatments that were seen at a higher frequency in the intellectual disability study group. In patients with mental retardation, a higher frequency of restorative treatment and extractions occurs as compared to healthy subjects of similar age group. Therefore, they require special attention regarding maintenance of their oral health. Special attention should be given for maintaining the oral health of patients with special health care needs as compared to their physically and mentally normal counterparts.

  6. A review of residual stress analysis using thermoelastic techniques

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, A F; Dulieu-Barton, J M; Quinn, S [University of Southampton, School of Engineering Sciences, Highfield, Southampton, SO17 1BJ (United Kingdom); Burguete, R L [Airbus UK Ltd., New Filton House, Filton, Bristol, BS99 7AR (United Kingdom)

    2009-08-01

    Thermoelastic Stress Analysis (TSA) is a full-field technique for experimental stress analysis that is based on infra-red thermography. The technique has proved to be extremely effective for studying elastic stress fields and is now well established. It is based on the measurement of the temperature change that occurs as a result of a stress change. As residual stress is essentially a mean stress it is accepted that the linear form of the TSA relationship cannot be used to evaluate residual stresses. However, there are situations where this linear relationship is not valid or departures in material properties due to manufacturing procedures have enabled evaluations of residual stresses. The purpose of this paper is to review the current status of using a TSA based approach for the evaluation of residual stresses and to provide some examples of where promising results have been obtained.

  7. A review of residual stress analysis using thermoelastic techniques

    International Nuclear Information System (INIS)

    Robinson, A F; Dulieu-Barton, J M; Quinn, S; Burguete, R L

    2009-01-01

    Thermoelastic Stress Analysis (TSA) is a full-field technique for experimental stress analysis that is based on infra-red thermography. The technique has proved to be extremely effective for studying elastic stress fields and is now well established. It is based on the measurement of the temperature change that occurs as a result of a stress change. As residual stress is essentially a mean stress it is accepted that the linear form of the TSA relationship cannot be used to evaluate residual stresses. However, there are situations where this linear relationship is not valid or departures in material properties due to manufacturing procedures have enabled evaluations of residual stresses. The purpose of this paper is to review the current status of using a TSA based approach for the evaluation of residual stresses and to provide some examples of where promising results have been obtained.

  8. X-ray stress analysis of residual stress gradients in surface layers of steel

    International Nuclear Information System (INIS)

    Ganev, N.; Kraus, I.; Gosmanova, G.; Pfeiffer, L.; Tietz, H.-D.

    2001-01-01

    The aim of the contribution is to present the theoretical possibilities of X-ray non-destructive identification of stress gradients within the penetration depth of used radiation and its utilization for experimental stress analysis. Practical usefullness of outlined speculations is illustrated with results of stress measurements on cut and shot-penned steel samples. (author)

  9. Dental caries in Arab League countries: a systematic review and meta-analysis.

    Science.gov (United States)

    Khan, Soban Qadir

    2014-08-01

    The aim of this review was to determine prevalence of dental caries in primary and permanent teeth in the 2-20-year-old population of the Arab league. A literature search was performed on Pubmed, Summon and Google Scholar using the key words 'Dental caries', 'dmft' and 'DMFT'. A total of 293 articles were found, of which 35 passed our inclusion criteria and were included in analysis. Tables were made separately for primary and permanent teeth; the age group for primary teeth was 2-12 years and for permanent teeth 6-20 years. A meta-analysis was run by using data extracted from the studies included. Heterogeneity was tested by forest plot and chi-square test, and considerable heterogeneity was found. Mean decayed, missing and filled teeth (dmft) was 4.341 (95% CI 3.714, 4.969) and in permanent teeth (DMFT) was 2.469 (95% CI 2.019, 2.919) from a random effect model. Publication bias diagnostics suggested missing of four studies of primary teeth caries data and eight studies of permanent teeth caries data to obtain symmetry in the funnel plot. The incidence of caries in primary teeth was found to be high compared with caries in permanent teeth in the Arab League. This study does not provide a comprehensive picture of caries prevalence in the Arab League because in many of these countries only a few studies were performed. Therefore, these data cannot provide a complete picture of the prevalence of caries in those countries. Additional studies are needed to better evaluate the prevalence of caries in children and young adults in Arab League countries. © 2014 FDI World Dental Federation.

  10. FEA stress analysis for SAFKEG 2863B

    International Nuclear Information System (INIS)

    Puckett, A.

    1997-01-01

    This report covers the evaluation of the structural design of the two stainless steel containment vessels in CROFT SAFKEG Model Number 2863B, for conformance to the design criteria of the NRC Regulatory Guide 7.6, NRC Regulatory Guide 7.8, and the applicable requirements of the ASME Boiler and Pressure Vessel Code, Section 3, and Section 8. The two containment vessels are designated Cans 2870 and 2871. Each of these containment vessels was analyzed for the loadings specified in chapter 2, Section 2.1.2 of the SARP. Structural assessment of Cans 2870 and 2871 due to loading considerations beyond the evaluation of pressure and temperature are presented. This report is organized as follows: (1) overview of the design of each containment vessel and pressure boundary; (2) brief description of both containment vessels; (3) discussion of normal and accident conditions; (4) analysis assumptions; (5) detailed structural evaluation of each component of each containment vessel; (6) demonstration of compliance to Regulatory Guide 7.6 stress evaluations; (7) demonstration of compliance to Regulatory Guide 7.8 loading combinations; and (8) summary of the calculated stresses, comparison with design allowables, estimates of margins of safety and a summary of results and conclusions

  11. Community-Based Dental Education Models: An Analysis of Current Practices at U.S. Dental Schools.

    Science.gov (United States)

    Mays, Keith A

    2016-10-01

    Community-based dental education (CBDE) enhances students' clinical expertise, improves their cultural competence, increases access to care, and fosters community engagement. As emphasis on CBDE has increased over the last decades, the aim of this survey study was to determine how CBDE is currently being implemented in U.S. dental schools. The study used a 20-item, author-designed survey emailed in April to August 2015 to 60 of the 65 U.S. dental schools, excluding those that had been recently established. Of the 60 schools, representatives of 33 responded, resulting in a 55% response rate: 70% public and 30% private. These respondents reported that the extramural sites being used the most were community clinics (90.9%), Federally Qualified Health Clinics (66.7%), public health clinics (54.5%), and Indian Health Service clinics (42.4%). The majority of responding schools (63.6%) had ten or more sites available for rotations, and the rotation lengths were 1-2 weeks (29%), 2-4 weeks (25%), 4-6 weeks (29%), 6-8 weeks (3.2%), and 8-10 weeks (12.9%). Most of the respondents (78.8%) reported that their students were unable to be assessed for clinical competencies at external clinical sites, but roughly half allowed students to receive clinical credit. After students completed their rotations, the majority of the respondents (81.8%) reported that students were required to produce a reflection, and 87.9% reported that students completed a post-rotation survey. Considering the benefits of CBDE for students' education and for improving access to oral health care, it is encouraging that over 45% of the responding schools required their students to spend four weeks or longer on external rotations.

  12. An Instrument to Measure Dental Students' Communication Skills With Patients in Six Specific Circumstances: An Exploratory Factor Analysis.

    Science.gov (United States)

    Aalboe, Joanna A; Schumacher, Mitzi M

    2016-01-01

    The aim of this study was to explore the internal structure of an instrument assessing dental students' confidence in their ability to communicate with patients in six specific circumstances (anxious, in pain, etc.) using exploratory factor analysis. In a Communication in the Dental Health Care Setting course at a U.S. dental school, second-year dental students in two years (2013 and 2014) responded to the six items on a survey instrument. Of the total 123 students, 122 fully completed the instrument, for a response rate of 99%. Analysis of the results identified a unidimensional scale with regards to patient-specific communication self-efficacy and explained 74% of the total variance. The scale had good internal consistency reflected by high Cronbach's alpha (α=0.929, 95% CI [0.907, 0.947]). These findings suggest the instrument may be a useful tool in assessing the development of patient communication skills in second-year dental students following a course in communication. Further exploration utilizing confirmatory analysis, determining predictive validity, and assessing convergent and discriminant evidence is warranted.

  13. Privacy and Psychosomatic Stress: An Empirical Analysis.

    Science.gov (United States)

    Webb, Stephen D.

    1978-01-01

    Examines the supposition that insufficient privacy is stressful to the individual. Data were obtained from urban centers in New Zealand. Findings support the hypothesis that a percieved lack of privacy is associated with psychosomatic stress. The relationship is specified by measures of stress and sex of respondents. (Author)

  14. Yield stress fluids slowly yield to analysis

    NARCIS (Netherlands)

    Bonn, D.; Denn, M.M.

    2009-01-01

    We are surrounded in everyday life by yield stress fluids: materials that behave as solids under small stresses but flow like liquids beyond a critical stress. For example, paint must flow under the brush, but remain fixed in a vertical film despite the force of gravity. Food products (such as

  15. Understanding the management and teaching of dental restoration repair: Systematic review and meta-analysis of surveys.

    Science.gov (United States)

    Kanzow, Philipp; Wiegand, Annette; Göstemeyer, Gerd; Schwendicke, Falk

    2018-02-01

    Repair instead of complete replacement is recommended to manage partially defective restorations. It is unclear if and why such treatment is taught at dental schools or practiced by dentists. We aimed to identify barriers and facilitators for repairs using a systematic review and meta- and qualitative analysis. Electronic databases (PubMed, CENTRAL, Embase, PsycINFO) were searched. Quantitative studies reporting on the proportion of (1) dentists stating to perform repairs, (2) dental schools teaching repairs, (3) failed restorations having been repaired were included. We also included qualitative studies on barriers/facilitators for repairs. Random-effects meta-analyses, meta-regression and a thematic analysis using the theoretical domains framework were conducted. 401 articles were assessed and 29, mainly quantitative, studies included. 7228 dentists and 276 dental schools had been surveyed, and treatment data of 30,172 restorations evaluated. The mean (95% CI) proportion of dentists stating to perform repairs was 71.5% (49.7-86.4%). 83.3% (73.6-90.0%) of dental schools taught repairs. 31.3% (26.3-36.7%) of failed restorations had been repaired. More recent studies reported significantly more dentists to repair restorations (p=0.004). Employment in public health practices and being the dentist who placed the original restoration were facilitators for repairs. Amalgam restorations were repaired less often, and financial aspects and regulations came as barriers. While most dentists state to perform repairs and the vast majority of dental schools teach repairs, the proportion of truly repaired restorations was low. A number of interventions to implement repair in dental practice can be deduced from our findings. Partially defective restorations are common in dental practice. While repairs are taught and dentists are aware of the recommendation towards repairs, the actually performed proportion of repairs seems low. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. A geometric morphometric analysis of hominin lower molars: Evolutionary implications and overview of postcanine dental variation.

    Science.gov (United States)

    Gómez-Robles, Aida; Bermúdez de Castro, José María; Martinón-Torres, María; Prado-Simón, Leyre; Arsuaga, Juan Luis

    2015-05-01

    Lower molars have been extensively studied in the context of hominin evolution using classic and geometric morphometric analyses, 2D and 3D approaches, evaluations of the external (outer enamel surface) and internal anatomy (dentine, pulp chamber, and radicular canals), and studies of the crown and root variation. In this study, we present a 2D geometric morphometric analysis of the crown anatomy of lower first, second, and third molars of a broad sample of hominins, including Pliocene and Lower, Middle, and Upper Pleistocene species coming from Africa, Asia, and Europe. We show that shape variability increases from first to second and third molars. While first molars tend to retain a relatively stable 5-cusped conformation throughout the hominin fossil record, second and third molars show marked distal reductions in later Homo species. This trend to distal reduction is similar to that observed in previous studies of premolars and upper second and third molars, and points to a correlated reduction of distal areas across the whole postcanine dentition. Results on lower molar variation, as well as on other postcanine teeth, show certain trends in European Pleistocene populations from the Atapuerca sites. Middle Pleistocene hominins from Sima de los Huesos show Neanderthal affinities and strong dental reduction, especially in the most distal molars. The degree of dental reduction in this population is stronger than that observed in classic Neanderthals. Homo antecessor hominins from Gran Dolina-TD6 have primitive lower teeth that contrast with their more derived upper teeth. The evolutionary implications of these dental affinities are discussed in light of recent paleogenetic studies. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Bruxism and dental implant failures: a multilevel mixed effects parametric survival analysis approach.

    Science.gov (United States)

    Chrcanovic, B R; Kisch, J; Albrektsson, T; Wennerberg, A

    2016-11-01

    Recent studies have suggested that the insertion of dental implants in patients being diagnosed with bruxism negatively affected the implant failure rates. The aim of the present study was to investigate the association between the bruxism and the risk of dental implant failure. This retrospective study is based on 2670 patients who received 10 096 implants at one specialist clinic. Implant- and patient-related data were collected. Descriptive statistics were used to describe the patients and implants. Multilevel mixed effects parametric survival analysis was used to test the association between bruxism and risk of implant failure adjusting for several potential confounders. Criteria from a recent international consensus (Lobbezoo et al., J Oral Rehabil, 40, 2013, 2) and from the International Classification of Sleep Disorders (International classification of sleep disorders, revised: diagnostic and coding manual, American Academy of Sleep Medicine, Chicago, 2014) were used to define and diagnose the condition. The number of implants with information available for all variables totalled 3549, placed in 994 patients, with 179 implants reported as failures. The implant failure rates were 13·0% (24/185) for bruxers and 4·6% (155/3364) for non-bruxers (P bruxism was a statistically significantly risk factor to implant failure (HR 3·396; 95% CI 1·314, 8·777; P = 0·012), as well as implant length, implant diameter, implant surface, bone quantity D in relation to quantity A, bone quality 4 in relation to quality 1 (Lekholm and Zarb classification), smoking and the intake of proton pump inhibitors. It is suggested that the bruxism may be associated with an increased risk of dental implant failure. © 2016 John Wiley & Sons Ltd.

  18. Proteomic analysis of cold stress responses in tobacco seedlings ...

    African Journals Online (AJOL)

    Cold stress is one of the major abiotic stresses limiting the productivity and the geographical distribution of many important crops. To gain a better understanding of cold stress responses in tobacco (Nicotiana tabacum), we carried out a comparative proteomic analysis. Five-week-old tobacco seedlings were treated at 4°C ...

  19. Finite element stress analysis of brick-mortar masonry under ...

    African Journals Online (AJOL)

    Stress analysis of a brick-mortar couplet as a substitute for brick wall structure has been performed by finite element method, and algorithm for determining the element stiffness matrix for a plane stress problem using the displacement approach was developed. The nodal displacements were derived for the stress in each ...

  20. Dental computed tomographic imaging as age estimation: morphological analysis of the third molar of a group of Turkish population.

    Science.gov (United States)

    Cantekin, Kenan; Sekerci, Ahmet Ercan; Buyuk, Suleyman Kutalmis

    2013-12-01

    Computed tomography (CT) is capable of providing accurate and measurable 3-dimensional images of the third molar. The aims of this study were to analyze the development of the mandibular third molar and its relation to chronological age and to create new reference data for a group of Turkish participants aged 9 to 25 years on the basis of cone-beam CT images. All data were obtained from the patients' records including medical, social, and dental anamnesis and cone-beam CT images of 752 patients. Linear regression analysis was performed to obtain regression formulas for dental age calculation with chronological age and to determine the coefficient of determination (r) for each sex. Statistical analysis showed a strong correlation between age and third-molar development for the males (r2 = 0.80) and the females (r2 = 0.78). Computed tomographic images are clinically useful for accurate and reliable estimation of dental ages of children and youth.

  1. Vocational satisfaction, coping strategies, and perceived stress as factors of ‘burnout’ in clinical dental students.

    Directory of Open Access Journals (Sweden)

    Francisco Pérez

    2013-12-01

    Full Text Available Having discussed different factors contributing towards “Burnout Syndrome” (BOS in dentistry students, the aim of this project is to analyze the existing relationship between vocational satisfaction, coping strategies and perceived stress as determining factors of burnout in 4th and 5th year dentistry students. Methods: Prospective cohort study (March-December. The relationship between vocational satisfaction, coping strategies and perceived stress as factors towards BOS in 4th and 5th year dentistry students will be determined. All participants will be required to sign a consent form the project will be evaluated by the Ethics Committee. The sociodemographic variables to be measured are: age, gender and socioeconomic status; the psychological variables are: Burnout Syndrome severity, using Maslach Burnout Inventory (MBI, coping strategies by Copyng Strategies Inventory (CSI, perceived stress with Perceived Stress Scale Questionnaire (PSS. All versions above have been validated in Spanish, and vocational satisfaction of the Dentistry Degree will be measured using a questionnaire, with 6 questions for 3 parameters: career choice, current feeling and predicted feeling after graduation. The data collection will be carried out in 4 stages: informed consent obtainment; MBI, CSI, PSS scales and vocational satisfaction questionnaire in March. In the second (June, third (September and fourth (November stages, the questionnaires will be repeated: MBI, PSS and vocational satisfaction. The findings and analysis will be processed in STATA 10/SE including descriptive statistics, regression models, measures and tests of association.

  2. ANALYSIS OF THE OPINIONS EXPRESSED BY THE DENTAL AID CONSUMERS IN THE REPUBLIC OF BULGARIA

    Directory of Open Access Journals (Sweden)

    Evelina Perchinska–Poptodorova

    2017-09-01

    Full Text Available Purpose: In the Republic of Bulgaria dental disorders concern the prevailing population. They are cumulative, progressive and are not self-healing. The present paper examines the patient's opinions about the dental care. Materials and Methods: The paper is based on a research realized in June-December 2016. The research was conducted among patients with dental care using dental services in the capital. The authors investigate their knowledge of the dental package by NHIF, how often they use it, whether their needs have been satisfied, how many of them have additional voluntary health insurance package for dental services and is there any financial benefit. Results and conclusions: The study shows that the dental healthcare system doesn’t meet the needs of the patients.

  3. Factor analysis for exercise stress radionuclide ventriculography

    International Nuclear Information System (INIS)

    Hirota, Kazuyoshi; Yasuda, Mitsutaka; Oku, Hisao; Ikuno, Yoshiyasu; Takeuchi, Kazuhide; Takeda, Tadanao; Ochi, Hironobu

    1987-01-01

    Using factor analysis, a new image processing in exercise stress radionuclide ventriculography, changes in factors associated with exercise were evaluated in 14 patients with angina pectoris or old myocardial infarction. The patients were imaged in the left anterior oblique projection, and three factor images were presented on a color coded scale. Abnormal factors (AF) were observed in 6 patients before exercise, 13 during exercise, and 4 after exercise. In 7 patients, the occurrence of AF was associated with exercise. Five of them became free from AF after exercise. Three patients showing AF before exercise had aggravation of AF during exercise. Overall, the occurrence or aggravation of AF was associated with exercise in ten (71 %) of the patients. The other three patients, however, had disappearance of AF during exercise. In the last patient, none of the AF was observed throughout the study. In view of a high incidence of AF associated with exercise, the factor analysis may have the potential in evaluating cardiac reverse from the viewpoint of left ventricular wall motion abnormality. (Namekawa, K.)

  4. What do patients think about dental services in Quebec? Analysis of a dentist rating website.

    Science.gov (United States)

    Macdonald, Mary Ellen; Beaudin, Anne; Pineda, Carolina

    2015-01-01

    Disparity exists between the public view of the "ideal" dentist and patient experiences of dental practice: dentists are expected to be altruistic and patient-centred, yet patient surveys suggest that the profession is overly motivated by profit. To determine how the public views dental care in Quebec. A random sample of comments about Quebec dentists made in 2011 was extracted from the public website RateMDs.com. Dentist characteristics and patient comments were analyzed using descriptive statistics and qualitative deductive and inductive thematic analysis. Eighty-six entries from a random sample of 47 of a possible 750 dentists were extracted and analyzed. Most dentists were men (66%) and worked in Montreal (51%). Patient comments were mainly positive (83%). Themes included overall impressions, communication and care, clinical competence, professionalism and office environment. Positive comments focused on patient-centred communication, in which the patient felt respected and involved in treatment planning; competence, seen as comprehensive, efficient and long-lasting treatment; and professionalism, which included ethical behaviour such as knowing professional limits. Negative comments focused on reticent communication styles that did not encourage patient input; incompetence, which included poor pain management and unnecessary treatment; and unprofessional conduct, such as lack of transparency in pricing. In contrast with the negative image of dentists reported from patient surveys, comments on one public website were primarily positive. Our findings reinforce the importance of patient-centred education and communication training for students and continuing education.

  5. HPLC analysis of potentially harmful substances released from dental filing aterials available on the EU market

    Directory of Open Access Journals (Sweden)

    Konrad Małkiewicz

    2014-03-01

    Full Text Available Introduction. Incomplete cross-linking of composite dental materials leads to their susceptibility to degradation in the environment of non-organic and organic solvents, contributing to the release of chemical compounds which are potentially harmful to living organisms. Objective. The aim of the study was an evaluation in in vitro conditions of releasing of potentially toxic substances from six dental composite materials available in EU countries. Materials and methods. The following compounds released from the samples stored in water were analyzed: bisphenol A (BPA, triethylene glycol-dimethacrylate (TEGDMA, urethane dimethacrylate (UDMA and ethylene glycol dimethacrylate (EDGMA. Analysis of the substances was performed with the use of high performance liquid chromatography, after the following incubation periods: 1 hour, 24 hours, 7 days and 30 days. Results. Among the analyzed substances, after 1 hour of incubation, the highest average concentration was found for TEGDMA – 2045 μg cm-3 (in Herculite XRV material, after 24 hours – for UDMA 4.402 μg cm-3 (in Gradia Direct Anterior material and after 7 and 30 days for TEGDMA: 8.112 and 6.458 μg•cm-3 respectively (in Charisma material. Conclusions. The examined composites used for reconstruction of hard tissues of teeth remain chemically unstable after polymerization, and release potentially harmful substances in conditions of the present study. The dynamics of the releasing of potentially harmful substances is correlated with the period of sample storage in water.

  6. A new approach for interexaminer reliability data analysis on dental caries calibration

    Directory of Open Access Journals (Sweden)

    Andréa Videira Assaf

    2007-12-01

    Full Text Available Objectives: a to evaluate the interexaminer reliability in caries detection considering different diagnostic thresholds and b to indicate, by using Kappa statistics, the best way of measuring interexaminer agreement during the calibration process in dental caries surveys. Methods: Eleven dentists participated in the initial training, which was divided into theoretical discussions and practical activities, and calibration exercises, performed at baseline, 3 and 6 months after the initial training. For the examinations of 6-7-year-old schoolchildren, the World Health Organization (WHO recommendations were followed and different diagnostic thresholds were used: WHO (decayed/missing/filled teeth - DMFT index and WHO + IL (initial lesion diagnostic thresholds. The interexaminer reliability was calculated by Kappa statistics, according to WHO and WHO+IL thresholds considering: a the entire dentition; b upper/lower jaws; c sextants; d each tooth individually. Results: Interexaminer reliability was high for both diagnostic thresholds; nevertheless, it decreased in all calibration sections when considering teeth individually. Conclusion: The interexaminer reliability was possible during the period of 6 months, under both caries diagnosis thresholds. However, great disagreement was observed for posterior teeth, especially using the WHO+IL criteria. Analysis considering dental elements individually was the best way of detecting interexaminer disagreement during the calibration sections.

  7. Diabetes an inducing factor for dental caries: A case control analysis in Jammu.

    Science.gov (United States)

    Singh, Iqbal; Singh, Paramjeet; Singh, Amarpreet; Singh, Tara; Kour, Robindera

    2016-01-01

    Diabetes mellitus (DM) is a common chronic disease and it has emerged as a major health-care problem. There are more chances of dentinal caries among diabetics than nondiabetics. DM is responsible for causing ascendancy in the proportion and activity of saliva that impacts the oral health. The objective of the present study is to evaluate the impact of various factors present in saliva on tooth decay amid type-II DM in Jammu. The subjects in our analysis comprises of 50 patients with type-II DM and 50 controls within the age group of 30-60 years. Diabetic status was assessed by estimating random blood glucose levels. Dental findings were recorded using modified World Health Organization (WHO) Oral health survey-basic method 2013. Salivary samples from all the subjects were collected and sent to the laboratory for interpretation of pH, flow rate, and salivary calcium. The analysis of salivary components decayed tooth was carried using analysis of variance (ANOVA) and Pearson's correlation test. All the parameters were subjected to statistical analysis using Statistical Package for the Social Sciences (SPSS) version 20.0. The results have shown a significantly lower values of salivary pH, flow rate, and calcium levels in diabetics than in nondiabetics. Within the limits of the present study, the results indicated that patients with type-II DM have high rate of dental caries and are at high risk of caries development. The decline in the salivary components will reduce capability of supporting the mineral compartment of tooth structure to resist the demineralization process by cariogenic potentials thereby creating a favorable environment for caries progression.

  8. The analysis of cost-effectiveness of implant and conventional fixed dental prosthesis.

    Science.gov (United States)

    Chun, June Sang; Har, Alix; Lim, Hyun-Pil; Lim, Hoi-Jeong

    2016-02-01

    This study conducted an analysis of cost-effectiveness of the implant and conventional fixed dental prosthesis (CFDP) from a single treatment perspective. The Markov model for cost-effectiveness analysis of the implant and CFDP was carried out over maximum 50 years. The probabilistic sensitivity analysis was performed by the 10,000 Monte-Carlo simulations, and cost-effectiveness acceptability curves (CEAC) were also presented. The results from meta-analysis studies were used to determine the survival rates and complication rates of the implant and CFDP. Data regarding the cost of each treatment method were collected from University Dental Hospital and Statistics Korea for 2013. Using the results of the patient satisfaction survey study, quality-adjusted prosthesis year (QAPY) of the implant and CFDP strategy was evaluated with annual discount rate. When only the direct cost was considered, implants were more cost-effective when the willingness to pay (WTP) was more than 10,000 won at 10(th) year after the treatment, and more cost-effective regardless of the WTP from 20(th) year after the prosthodontic treatment. When the indirect cost was added to the direct cost, implants were more cost-effective only when the WTP was more than 75,000 won at the 10(th) year after the prosthodontic treatment, more than 35,000 won at the 20(th) year after prosthodontic treatment. The CFDP was more cost-effective unless the WTP was more than 75,000 won at the 10(th) year after prosthodontic treatment. But the cost-effectivenss tendency changed from CFDP to implant as time passed.

  9. Stress analysis on a PWR pressure vessel support structure

    International Nuclear Information System (INIS)

    Cruz, J.R.B.; Mattar Neto, M.; Jesus Miranda, C.A. de.

    1992-01-01

    The paper presents the stress analysis of a research PWR vessel support structure. Different geometries and thermal boundary conditions are evaluated. The finite element analysis is performed using ANSYS program. The ASME Section III criteria are applied for the stress verification and the following points are discussed: stress classification and linearization; jurisdictional boundary between ASME Subsection NB (Class 1 Components) and Subsection NF (Component Supports). (author)

  10. [Analysis of the interaction of genotypic and paratypic factors in the development of maxillo-dental anomalies in ontogeny].

    Science.gov (United States)

    Lil'in, E T; Persin, L S; Titov, V I; Danilina, O A

    1996-09-01

    Component analysis of total phenotypic variance was used to analyze data on 80 pairs of twins aged 3 to 18 years, examined in the Stupino outpatient dental clinic, Moscow oblast. Genotypic and environmental factors are shown to play different roles in the development of abnormalities of teeth, dental arches, and occlusion at different ontogenetic periods of deciduous, mixed, and permanent dentition. Periods when paratypic factors prevailed were revealed. This made it possible to identity periods when prophylaxis and orthodontic treatment are the most advisable.

  11. Stress analysis of HLW containers. Compas project

    International Nuclear Information System (INIS)

    1989-01-01

    This document reports the work carried out for the Compas project which looked at the performance of various computer codes in a selected benchmark exercise. This exercise consisted of several analyses on simplified models which have features typical of HLW containers. These analyses comprise two groups; one related to thick walled, stressed shell overpacks, the other related to thin walled, supported shell overpacks with a lead filler. The first set of analyses looked at an elastic-plastic behaviour and large deformation of a cylinder representative of the main body of thick walled containers). The second set looked at creep behaviour of the lead filler, and the shape the base of thin walled containers will take up, after hundreds of years in the repository. On the thick walled analyses with the cylinder subject to an external pressure all the codes gave consistent results in the elastic region and there is good agreement in the yield pressures. Once in the plastic region there is more divergence in the results although a consistent trend is predicted. One of the analyses predicted a non-axisymmetric mode of deformation as would be expected in reality. Fewer results were received for the creep analysis, however the transient creep results showed consistency, and were bounded by the final-state results

  12. Local stress analysis in devices by FIB

    NARCIS (Netherlands)

    Kregting, R.; Gielen, A.W.J.; Driel, W. van; Alkemade, P.; Miro, H.; Kamminga, J.-D.

    2010-01-01

    Intrinsic stresses in bondpads may lead to early failure of IC's. In order to determine the intrinsic stresses in semiconductor structures, a new procedure is set up. This procedure is a combined experimental/numerical approach which consists of the following steps: First, a conductive gold layer

  13. Analysis of stress-strain relationships in silicon ribbon

    Science.gov (United States)

    Dillon, O. W., Jr.

    1984-01-01

    An analysis of stress-strain relationships in silicon ribbon is presented. A model to present entire process, dynamical Transit Analysis is developed. It is found that knowledge of past-strain history is significant in modeling activities.

  14. Stress Analysis in Polymeric Coating Layer Deposited on Rigid Substrate

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Soon Lee [Korea University of Technology and Education, School of Mechatronics Engineering, Chonan (Korea, Republic of)

    2015-08-15

    This paper presents an analysis of thermal stress induced along the interface between a polymeric coating layer and a steel substrate as a result of uniform temperature change. The epoxy layer is assumed to be a linear viscoelastic material and to be theromorheologically simple. The viscoelastic boundary element method is employed to investigate the behavior of interface stresses. The numerical results exhibit relaxation of interface stresses and large stress gradients, which are observed in the vicinity of the free surface. Since the exceedingly large stresses cannot be borne by the polymeric coating layer, local cracking or delamination can occur at the interface corner.

  15. Analysis of four dental alloys following torch/centrifugal and induction/ vacuum-pressure casting procedures.

    Science.gov (United States)

    Thompson, Geoffrey A; Luo, Qing; Hefti, Arthur

    2013-12-01

    Previous studies have shown casting methodology to influence the as-cast properties of dental casting alloys. It is important to consider clinically important mechanical properties so that the influence of casting can be clarified. The purpose of this study was to evaluate how torch/centrifugal and inductively cast and vacuum-pressure casting machines may affect the castability, microhardness, chemical composition, and microstructure of 2 high noble, 1 noble, and 1 base metal dental casting alloys. Two commonly used methods for casting were selected for comparison: torch/centrifugal casting and inductively heated/ vacuum-pressure casting. One hundred and twenty castability patterns were fabricated and divided into 8 groups. Four groups were torch/centrifugally cast in Olympia (O), Jelenko O (JO), Genesis II (G), and Liberty (L) alloys. Similarly, 4 groups were cast in O, JO, G, and L by an inductively induction/vacuum-pressure casting machine. Each specimen was evaluated for casting completeness to determine a castability value, while porosity was determined by standard x-ray techniques. Each group was metallographically prepared for further evaluation that included chemical composition, Vickers microhardness, and grain analysis of microstructure. Two-way ANOVA was used to determine significant differences among the main effects. Statistically significant effects were examined further with the Tukey HSD procedure for multiple comparisons. Data obtained from the castability experiments were non-normal and the variances were unequal. They were analyzed statistically with the Kruskal-Wallis rank sum test. Significant results were further investigated statistically with the Steel-Dwass method for multiple comparisons (α=.05). The alloy type had a significant effect on surface microhardness (Pcasting did not affect the microhardness of the test specimen (P=.465). Similarly, the interaction between the alloy and casting technique was not significant (P=.119). A high

  16. Three-Dimensional Nonlinear Finite Element Analysis and Microcomputed Tomography Evaluation of Microgap Formation in a Dental Implant Under Oblique Loading.

    Science.gov (United States)

    Jörn, Daniela; Kohorst, Philipp; Besdo, Silke; Borchers, Lothar; Stiesch, Meike

    2016-01-01

    Since bacterial leakage along the implant-abutment interface may be responsible for peri-implant infections, a realistic estimation of the interface gap width during function is important for risk assessment. The purpose of this study was to compare two methods for investigating microgap formation in a loaded dental implant, namely, microcomputed tomography (micro-CT) and three-dimensional (3D) nonlinear finite element analysis (FEA); additionally, stresses to be expected during loading were also evaluated by FEA. An implant-abutment complex was inspected for microgaps between the abutment and implant in a micro-CT scanner under an oblique load of 200 N. A numerical model of the situation was constructed; boundary conditions and external load were defined according to the experiment. The model was refined stepwise until its load-displacement behavior corresponded sufficiently to data from previous load experiments. FEA of the final, validated model was used to determine microgap widths. These were compared with the widths as measured in micro-CT inspection. Finally, stress distributions were evaluated in selected regions. No microgaps wider than 13 μm could be detected by micro-CT for the loaded implant. FEA revealed gap widths up to 10 μm between the implant and abutment at the side of load application. Furthermore, FEA predicted plastic deformation in a limited area at the implant collar. FEA proved to be an adequate method for studying microgap formation in dental implant-abutment complexes. FEA is not limited in gap width resolution as are radiologic techniques and can also provide insight into stress distributions within the loaded complex.

  17. Morphological and mineral analysis of dental enamel after erosive challenge in gastric juice and orange juice.

    Science.gov (United States)

    Braga, Sheila Regina Maia; De Faria, Dalva Lúcia Araújo; De Oliveira, Elisabeth; Sobral, Maria Angela Pita

    2011-12-01

    This study evaluated and compared in vitro the morphology and mineral composition of dental enamel after erosive challenge in gastric juice and orange juice. Human enamel specimens were submitted to erosive challenge using gastric juice (from endoscopy exam) (n = 10), and orange juice (commercially-available) (n = 10), as follows: 5 min in 3 mL of demineralization solution, rinse with distilled water, and store in artificial saliva for 3 h. This cycle was repeated four times a day for 14 days. Calcium (Ca) loss after acid exposure was determined by atomic emission spectroscopy. The presence of carbonate (CO) and phosphate (PO) in the specimens was evaluated before and after the erosive challenge by FT-Raman spectroscopy. Data were tested using t-tests (P enamel was observed in scanning electron microscopy (SEM). The mean loss of Ca was: 12.74 ± 3.33 mg/L Ca (gastric juice) and 7.07 ± 1.44 mg/L Ca (orange juice). The analysis by atomic emission spectroscopy showed statistically significant difference between erosive potential of juices (P = 0.0003). FT-Raman spectroscopy found no statistically significant difference in the ratio CO/PO after the erosive challenge. The CO/PO ratios values before and after the challenge were: 0.16/0.17 (gastric juice) (P = 0.37) and 0.18/0.14 (orange juice) (P = 0.16). Qualitative analysis by SEM showed intense alterations of enamel surface. The gastric juice caused more changes in morphology and mineral composition of dental enamel than orange juice. The atomic emission spectroscopy showed to be more suitable to analyze small mineral loss after erosive challenge than FT-Raman. Copyright © 2011 Wiley Periodicals, Inc.

  18. Orthostatic Dysregulation during Postural Change on the Dental Chair and Intraoperative Monitoring by Heart Rate Variability Analysis

    Directory of Open Access Journals (Sweden)

    Yukihiro Momota

    2014-01-01

    Full Text Available This is the first case report of orthostatic dysregulation (OD manifested during postural change on the dental chair and intraoperatively monitored by heart rate variability (HRV analysis. OD-associated autonomic dysfunction is induced by postural changes and easily leads to disturbance in circulatory dynamics; however, most dental practices have not yet realized the importance of managing OD. We measured autonomic activity in a patient with OD during dental therapy and assessed the clinical significance of HRV analysis for OD. The patient was a 17-year-old Japanese female. She was diagnosed with impacted wisdom teeth and had no previous history of a distinct systemic disease. A surgical procedure to extract the teeth was safely performed under both local anesthesia and sedation with nitrous oxide and midazolam. After the surgery, her postural change to sitting induced orthostatic hypotension. HRV variables showed parasympathetic dominance due to the upright position. Subsequently, her posture was returned to supine, and atropine sulfate administration for the immediate treatment of OD returned her blood pressure to normal levels. HRV variables showed relative sympathetic dominance due to an atropine-derived parasympathetic blockade. HRV analysis revealed OD-associated autonomic dysfunction and should become a standard tool for safe and secure dental management of OD.

  19. Analysis of pipe stress using CAESAR II code

    International Nuclear Information System (INIS)

    Sitandung, Y.B.; Bandriyana, B.

    2002-01-01

    Analysis of this piping stress with the purpose of knowing stress distribution piping system in order to determine pipe supports configuration. As an example of analysis, Gas Exchanger to Warm Separator Line was chosen with, input data was firstly prepared in a document, i.e. piping analysis specification that its content named as pipe characteristics, material properties, operation conditions, guide equipment's and so on. Analysis result such as stress, load, displacement and the use support type were verified based on requirements in the code, standard, and regularities were suitable with piping system condition analyzed. As the proof that piping system is in safety condition, it can be indicated from analysis results (actual loads) which still under allowable load. From the analysis steps that have been done CAESAR II code fulfill requirements to be used as a tool of piping stress analysis as well as nuclear and non nuclear installation piping system

  20. Economic impact of dental hygienists on solo dental practices.

    Science.gov (United States)

    Lazar, Vickie F; Guay, Albert H; Beazoglou, Tryfon J

    2012-08-01

    The fact that a significant percentage of dentists employ dental hygienists raises an important question: Are dental practices that utilize a dental hygienist structurally and operationally different from practices that do not? This article explores differences among dental practices that operate with and without dental hygienists. Using data from the American Dental Association's 2003 Survey of Dental Practice, a random sample survey of U.S. dentists, descriptive statistics were used to compare selected characteristics of solo general practitioners with and without dental hygienists. Multivariate regression analysis was used to estimate the effect of dental hygienists on the gross billings and net incomes of solo general practitioners. Differences in practice characteristics--such as hours spent in the practice and hours spent treating patients, wait time for a recall visit, number of operatories, square feet of office space, net income, and gross billings--were found between solo general practitioners who had dental hygienists and those who did not. Solo general practitioners with dental hygienists had higher gross billings. Higher gross billings would be expected, as would higher expenses. However, net incomes of those with dental hygienists were also higher. In contrast, the mean waiting time for a recall visit was higher among dentists who employed dental hygienists. Depending on personal preferences, availability of qualified personnel, etc., dentists who do not employ dental hygienists but have been contemplating that path may want to further research the benefits and opportunities that may be realized.

  1. Loss of idealism or realistic optimism? A cross-sectional analysis of dental hygiene students' and registered dental hygienists' professional identity perceptions.

    Science.gov (United States)

    Champine, J M; Inglehart, M R; Furgeson, D; Halaris, J F; Fitzgerald, M; Danciu, T E; Kinney, J S

    2018-02-01

    The dental hygiene profession in the U.S. is in the process of establishing a direct access model of care and contributing to the creation of the profession of a dental therapist. The objectives were to analyse the professional role perceptions of dental hygiene students and registered dental hygienists in these times of change. Specifically, it was explored whether dental hygiene students' current professional identities differ (i) from their expected future identities, and (ii) from dental hygienists' current and (iii) past identities. Survey data were collected from 215 dental hygiene students concerning their present and future role perceptions, and from 352 registered dental hygienists concerning their present and past professional identity perceptions. Students' future professional identity perceptions were even more positive than their very positive current perceptions of their professional role components. Students' current perceptions of professional pride, professional ambition, work ethic and patient relations were more positive than dental hygienists' current perceptions of these professional role components. A comparison of students' current perceptions with dental hygienists' current and retrospective descriptions showed that students were more positive than dental hygienists in each case. The fact that dental hygienists had less positive role perceptions than dental hygiene students might lead to the conclusion that a loss of idealism occurs over the course of a professional lifespan. However, dental hygienists actually improved their role perceptions over time and students' future descriptions were more positive than their current descriptions, supporting the interpretation that realistic optimism dominates professional role perceptions in these times of change. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  2. Problems of stress analysis of fuelling machine head components

    International Nuclear Information System (INIS)

    Mathur, D.D.

    1975-01-01

    The problem of stress analysis of fuelling machine head components are discussed. To fulfil the functional requirements, the components are required to have certain shapes where stress problems cannot be matched to a catalogue of pre-determined solutions. The areas where complex systems of loading due to hydrostatic pressure, weight, moments and temperature gradients coupled with the intricate shapes of the components make it difficult to arrive at satisfactory solutions. Particularly, the analysis requirements of the magazine housing, end cover, gravloc clamps and centre support are highlighted. An experimental stress analysis programme together with a theoretical finite element analysis is perhaps the answer. (author)

  3. Stress analysis for nuclear power plant components

    International Nuclear Information System (INIS)

    Mueller, R.A.

    1981-09-01

    The general procedure for a meaningful stress evaluation will be outlined. The extremely aggravated conditions prevailing at elevated temperatures, at which creep effects can no longer be neglected, will also be touched upon briefly. (E.G.) [pt

  4. The stress and strain analysis research of class 1 eqnipments

    International Nuclear Information System (INIS)

    Ye Yuanwu; Tang Long; Wang Yueying; Qi Min; Yu Huajin

    2008-01-01

    The class 1 equipment is very important in the nuclear device, in the design and testing process required to carry out their stress and strain analysis, so as to ensure their safety. There are two ways to get stress and strain analysis of the class 1 equipment, the theoretical and experimental methods. Through theoretical method can get the stress and strain of the class 1 equipment, so as to provide a basis for the design of the equipment; through the experimental method to verify the accuracy of the theoretical methods and provide a basis for the safety assessment of the equipment. The main ressel of CEFR (China Experimental Fast Reactor) is the class 1 equipment. In this paper, according to the stress and strain analysis research of CEFR main vessel, the theories and expperimental methods of nuclear class 1 equipments stress and strain analysis has been described. (authors)

  5. DEVELOPMENT OF COILED TUBING STRESS ANALYSIS

    Directory of Open Access Journals (Sweden)

    Davorin Matanović

    1998-12-01

    Full Text Available The use of coiled tubing is increasing rapidly with drilling of horizontal wells. To satisfy all requirements (larger mechanical stresses, larger fluid capacities the production of larger sizes and better material qualities was developed. Stresses due to axial forces and pressures that coiled tubing is subjected are close to its performance limits. So it is really important to know and understand the behaviour of coiled tubing to avoid its break, burst or collapse in the well.

  6. Initial stress and nonlinear material behavior in patient-specific AAA wall stress analysis

    NARCIS (Netherlands)

    Speelman, L.; Bosboom, E.M.H.; Schurink, G.W.H.; Buth, J.; Breeuwer, M.; Jacobs, M.J.; Vosse, van de F.N.

    2009-01-01

    Rupture risk estimation of abdominal aortic aneurysms (AAA) is currently based on the maximum diameter of the AAA. A more critical approach is based on AAA wall stress analysis. For that, in most cases, the AAA geometry is obtained from CT-data and treated as a stress free geometry. However, during

  7. Correlation and comparative analysis of the CPQ8-10 and child-OIDP indexes for dental caries and malocclusion.

    Science.gov (United States)

    Duarte-Rodrigues, Lucas; Ramos-Jorge, Joana; Drumond, Clarissa Lopes; Diniz, Priscilla Barboza; Marques, Leandro Silva; Ramos-Jorge, Maria Letícia

    2017-12-18

    The aim of this study was to evaluate the correlation between the Child Perceptions Questionnaire 8 to 10 (CPQ8-10) and child-Oral Impact on Daily Performances (child-OIDP) indexes according to their total and item scores, as well as assess the discriminative validity of these assessment tools regarding dental caries and malocclusion among schoolchildren. A sample of 300 children aged between 8 and 10 years answered the questionnaires in two distinct steps. First, half of the sample (G1 = 150) answered the CPQ8-10 and the other half (G2 = 150) answered the child-OIDP. A week after, G1 answered the child-OIDP and G2 answered the CPQ8-10. Dental Aesthetic Index and WHO criteria were used to categorize malocclusion and dental caries, respectively. Descriptive analysis, Spearman's correlation and Mann-Whitney test were performed in this study. The CPQ8-10 and child-OIDP demonstrated a statistically significant and moderate correlation between their total scores. Regarding the discriminative validity, CPQ8-10 demonstrated a significant association between the "emotional status" daily activity and dental caries, and between the "eating", "sleeping", and "studying" daily activities and malocclusion. Concerning the child-OIDP, a significant difference was found only between the "social contact" activity and presence of dental caries. Both instruments were not capable of distinguishing children with and without dental caries and/or malocclusion by their total scores. However, the instruments were able to discriminate between children with and without those oral disorders in different dimensions. Thus, the CPQ8-10 and the child-OIDP demonstrated a different capacity to assess the impact on OHRQoL among schoolchildren.

  8. Finite Element Residual Stress Analysis of Planetary Gear Tooth

    Directory of Open Access Journals (Sweden)

    Jungang Wang

    2013-01-01

    Full Text Available A method to simulate residual stress field of planetary gear is proposed. In this method, the finite element model of planetary gear is established and divided to tooth zone and profile zone, whose different temperature field is set. The gear's residual stress simulation is realized by the thermal compression stress generated by the temperature difference. Based on the simulation, the finite element model of planetary gear train is established, the dynamic meshing process is simulated, and influence of residual stress on equivalent stress of addendum, pitch circle, and dedendum of internal and external meshing planetary gear tooth profile is analyzed, according to non-linear contact theory, thermodynamic theory, and finite element theory. The results show that the equivalent stresses of planetary gear at both meshing and nonmeshing surface are significantly and differently reduced by residual stress. The study benefits fatigue cracking analysis and dynamic optimization design of planetary gear train.

  9. Contextual and individual factors associated with dental services utilisation by Brazilian adults: A multilevel analysis.

    Science.gov (United States)

    Herkrath, Fernando José; Vettore, Mario Vianna; Werneck, Guilherme Loureiro

    2018-01-01

    Inequalities in the utilisation of dental services in Brazil are remarkable. The aim of this study was to evaluate the association of contextual and individual factors with the utilisation of dental services by Brazilian adults using the Andersen's behavioural model. Individual-level data from 27,017 adults residents in the State capitals who were interviewed in the 2013 Brazilian National Health Survey were pooled with contextual city-level data. The outcomes were non-utilisation of dental services and last dental visit over 12 months ago. Individual predisposing variables were age, sex, race/skin colour, schooling and social network. Individual enabling variables included income, health insurance and registration in primary health care. Individual need variables were self-perceived dental health and self-reported missing teeth. Multilevel logistic regression models were performed to estimate odds ratio (OR) and 95% confidence intervals (95% CIs) of the association of contextual and individual predisposing, enabling and need-related variables with dental services outcomes. Predisposing (OR = 0.89; 95% CI 0.81-0.97) and enabling (OR = 0.90; 95% CI 0.85-0.96) contextual factors were associated with non-utilisation of dental services. Individual predisposing (sex, race/skin colour, schooling), enabling (income, health insurance) and need (self-perceived oral health, missing teeth) were associated with non-utilisation of dental services and last dental visit over 12 months ago. The latter was also associated with other individual predisposing (age, social network) and need (eating difficulties due to oral problems) characteristics. Individual and contextual determinants influenced dental services utilisation in Brazilian adults. These factors should be on the policy agenda and considered in the organisation of health services aiming to reduce oral health inequalities related to access and utilisation of dental services.

  10. PIPE STRESS and VERPIP codes for stress analysis and verifications of PEC reactor piping

    International Nuclear Information System (INIS)

    Cesari, F.; Ferranti, P.; Gasparrini, M.; Labanti, L.

    1975-01-01

    To design LMFBR piping systems following ASME Sct. III requirements unusual flexibility computer codes are to be adopted to consider piping and its guard-tube. For this purpose PIPE STRESS code previously prepared by Southern-Service, has been modified. Some subroutine for detailed stress analysis and principal stress calculations on all the sections of piping have been written and fitted in the code. Plotter can also be used. VERPIP code for automatic verifications of piping as class 1 Sct. III prescriptions has been also prepared. The results of PIPE STRESS and VERPIP codes application to PEC piping are in section III of this report

  11. Probabilistic analysis of structures involving random stress-strain behavior

    Science.gov (United States)

    Millwater, H. R.; Thacker, B. H.; Harren, S. V.

    1991-01-01

    The present methodology for analysis of structures with random stress strain behavior characterizes the uniaxial stress-strain curve in terms of (1) elastic modulus, (2) engineering stress at initial yield, (3) initial plastic-hardening slope, (4) engineering stress at point of ultimate load, and (5) engineering strain at point of ultimate load. The methodology is incorporated into the Numerical Evaluation of Stochastic Structures Under Stress code for probabilistic structural analysis. The illustrative problem of a thick cylinder under internal pressure, where both the internal pressure and the stress-strain curve are random, is addressed by means of the code. The response value is the cumulative distribution function of the equivalent plastic strain at the inner radius.

  12. Analysis of dental erosion induced by different beverages and validity of equipment for identifying early dental erosion, in vitro study.

    Science.gov (United States)

    Jameel, Rafey Ahmad; Khan, Shah Salman; Abdul Rahim, Zubaidah Hj; Bakri, Marina Mohd; Siddiqui, Saima

    2016-07-01

    To understand early dental erosion induced by different beverages and the equipment for its detection. The study was conducted at the University Malaya Medical Centre, Kuala Lumpur, Malaysia, from June to September 2014, and comprised single-rooted, unpolished teeth divided into six groups. Electron micrographs and other baseline readings for further analyses were taken before and after the exposure to different beverages. The teeth were exposed to the beverages using a modified Nordini's artificial mouth model. The positioning of the teeth on the motorised stage of the equipment was standardised. Of the several beverages used, CocaCola had the lowest pH value of 2.53, while tap water had the highest pH of 5.4. Deionised distilled water, which was used as a reference, had a pH near to neutral /alkaline of 7.3. The fluoride content ranged between 9.38ppm in tea and 0.005ppm in orange juice. Teeth exposed to beverages with low pH and considerably high fluoride underwent slight remineralisation (roughness increase 8% from tea), while beverages with no fluoride content and low pH roughened the enamel surface (Coca Cola roughened upto 37%). Quantitative analyses of tooth erosion, micro-hardness, surface-roughness, and surface-height showed that all beverages exhibited positive erosive effect on the tooth enamel surface (pCocaCola was found to be the most erosive agent among both hot and cold beverages (37%), while coffee was more erosive among the hot beverages (29%).

  13. Diagnostic Value of Manual and Computerized Methods of Dental Casts Analysis

    Directory of Open Access Journals (Sweden)

    H. Rahimi

    2009-06-01

    Full Text Available Objective: The aim of this study was to evaluate the validity of computerized and manual methods of dental cast analysis.Materials and Methods: Twenty set-ups of upper and lower casts using artificial teeth corresponding to various malocclusions were created for a diagnostic in vitro study. Values of tooth size were calculated from the isolated artificial teeth out of the set-ups, results were considered as a gold standard for the tooth size. Arch width was calculated from the existing set-ups on the dentins.Impressions were taken of the casts with alginate and duplicated with dental stone. Models were measured with digital caliper manually. Then images were taken from the occlusal views of the casts by a digital camera. Measurements were done on digital images with the AutoCAD software.The results of the computerized and manual methods were compared with the gold standard.Intra class correlation coefficient of reliability was used to measure the accuracy ofthe methods and the Friedman technique used to evaluate the significance of differences.Results: Results indicated that all measurements were highly correlated, e.g. gold standard and manual (0.9613-0.9991, gold standard and computerized (0.7118-0.9883, manual and computerized (0.6734-0.9914. Statistically significant differences were present between these methods (P<0.05, but they proved not to be clinically significant.Conclusion: Manual measurement is still the most accurate method when compared to the computerized measurements and the results of measurement by computer should be interpreted with caution.

  14. Thermographic Analysis of Stress Distribution in Welded Joints

    Directory of Open Access Journals (Sweden)

    Domazet Ž.

    2010-06-01

    Full Text Available The fatigue life prediction of welded joints based on S-N curves in conjunction with nominal stresses generally is not reliable. Stress distribution in welded area affected by geometrical inhomogeneity, irregular welded surface and weld toe radius is quite complex, so the local (structural stress concept is accepted in recent papers. The aim of this paper is to determine the stress distribution in plate type aluminum welded joints, to analyze the reliability of TSA (Thermal Stress Analysis in this kind of investigations, and to obtain numerical values for stress concentration factors for practical use. Stress distribution in aluminum butt and fillet welded joints is determined by using the three different methods: strain gauges measurement, thermal stress analysis and FEM. Obtained results show good agreement - the TSA mutually confirmed the FEM model and stresses measured by strain gauges. According to obtained results, it may be stated that TSA, as a relatively new measurement technique may in the future become a standard tool for the experimental investigation of stress concentration and fatigue in welded joints that can help to develop more accurate numerical tools for fatigue life prediction.

  15. Thermographic Analysis of Stress Distribution in Welded Joints

    Science.gov (United States)

    Piršić, T.; Krstulović Opara, L.; Domazet, Ž.

    2010-06-01

    The fatigue life prediction of welded joints based on S-N curves in conjunction with nominal stresses generally is not reliable. Stress distribution in welded area affected by geometrical inhomogeneity, irregular welded surface and weld toe radius is quite complex, so the local (structural) stress concept is accepted in recent papers. The aim of this paper is to determine the stress distribution in plate type aluminum welded joints, to analyze the reliability of TSA (Thermal Stress Analysis) in this kind of investigations, and to obtain numerical values for stress concentration factors for practical use. Stress distribution in aluminum butt and fillet welded joints is determined by using the three different methods: strain gauges measurement, thermal stress analysis and FEM. Obtained results show good agreement - the TSA mutually confirmed the FEM model and stresses measured by strain gauges. According to obtained results, it may be stated that TSA, as a relatively new measurement technique may in the future become a standard tool for the experimental investigation of stress concentration and fatigue in welded joints that can help to develop more accurate numerical tools for fatigue life prediction.

  16. Long-term patterns of dental attendance and caries experience among British adults: a retrospective analysis.

    Science.gov (United States)

    Aldossary, Arwa; Harrison, Victoria E; Bernabé, Eduardo

    2015-02-01

    There is inconclusive evidence on the value of regular dental attendance. This study explored the relationship between long-term patterns of dental attendance and caries experience. We used retrospective data from 3,235 adults, ≥ 16 yrs of age, who participated in the Adult Dental Health Survey in the UK. Participants were classified into four groups (always, current, former, and never regular-attenders) based on their responses to three questions on lifetime dental-attendance patterns. The association between dental-attendance patterns and caries experience, as measured using the decayed, missing, or filled teeth (DMFT) index, was tested in negative binomial regression models, adjusting for demographic (sex, age, and country of residence) and socio-economic (educational attainment, household income, and social class) factors. A consistent pattern of association between long-term dental attendance and caries experience was found in adjusted models. Former and never regular-attenders had a significantly higher DMFT score and numbers of decayed and missing teeth, but fewer filled teeth, than always regular-attenders. No differences in DMFT or its components were found between current and always regular-attenders. The findings of this study show that adults with different lifetime trajectories of dental attendance had different dental statuses. © 2014 Eur J Oral Sci.

  17. MATHEMATICAL ANALYSIS OF DENTAL ARCH OF CHILDREN IN NORMAL OCCLUSION: A LITERATURE REVIEW

    Directory of Open Access Journals (Sweden)

    M. Abu-Hussein DDS, MScD, MSc, DPD

    2012-03-01

    Full Text Available AIM. This paper is an attempt to compare and analyze the various mathematical models for defining the dental arch curvature of children in normal occlusion based upon a review of available literature. Background. While various studies have touched upon ways to cure or prevent dental diseases and upon surgical ways for teeth reconstitution to correct teeth anomalies during childhood, a substantial literature also exists, attempting to mathematically define the dental arch of children in normal occlusion. This paper reviews these dental studies and compares them analytically. Method. The paper compares the different mathematical approaches, highlights the basic assumptions behind each model, underscores the relevancy and applicability of the same, and also lists applicable mathematical formulae. Results. Each model has been found applicable to specific research conditions, as a universal mathematical model for describing the human dental arch still eludes satisfactory definition. The models necessarily need to include the features of the dental arch, such as shape, spacing between teeth and symmetry or asymmetry, but they also need substantial improvement. Conclusions. While the paper shows that the existing models are inadequate in properly defining the human dental arch, it also acknowledges that future research based on modern imaging techniques and computeraided simulation could well succeed in deriving an allinclusive definition for the human dental curve till now eluding the experts.

  18. Survey and Analysis of Dental Caries in Students at a Deaf-Mute High School

    Science.gov (United States)

    Wei, Hong; Wang, Yan-Ling; Cong, Xiao-Na; Tang, Wan-Qin; Wei, Ping-Min

    2012-01-01

    The present cross-sectional study was conducted to assess and compare the prevalence of dental caries of 229 deaf adolescents in a special senior high school and to identify factors related to dental caries, with a match group of 196 healthy adolescents in a normal senior high school, in Jiangsu province of East China. In this study the prevalence…

  19. Ceramic ball grid array package stress analysis

    Science.gov (United States)

    Badri, S. H. B. S.; Aziz, M. H. A.; Ong, N. R.; Sauli, Z.; Alcain, J. B.; Retnasamy, V.

    2017-09-01

    The ball grid array (BGA), a form of chip scale package (CSP), was developed as one of the most advanced surface mount devices, which may be assembled by an ordinary surface ball bumps are used instead of plated nickel and gold (Ni/Au) bumps. Assembly and reliability of the BGA's printed circuit board (PCB), which is soldered by conventional surface mount technology is considered in this study. The Ceramic Ball Grid Array (CBGA) is a rectangular ceramic package or square-shaped that will use the solder ball for external electrical connections instead of leads or wire for connections. The solder balls will be arranged in an array or grid at the bottom of the ceramic package body. In this study, ANSYS software is used to investigate the stress on the package for 2 balls and 4 balls of the CBGA package with the various force range of 1-3 Newton applied to the top of the die, top of the substrate and side of the substrate. The highest maximum stress was analyzed and the maximum equivalent stress was observed on the solder ball and the die. From the simulation result, the CBGA package with less solder balls experience higher stress compared to the package with many solder balls. Therefore, less number of solder ball on the CBGA package results higher stress and critically affect the reliability of the solder balls itself, substrate and die which can lead to the solder crack and also die crack.

  20. Which antibiotic regimen prevents implant failure or infection after dental implant surgery? A systematic review and meta-analysis.

    Science.gov (United States)

    Rodríguez Sánchez, Fabio; Rodríguez Andrés, Carlos; Arteagoitia, Iciar

    2018-04-01

    To assess which antibiotic regimen prevents dental implant failures or postoperative infections following dental implant placement. Systematic review and meta-analysis. Pubmed, Cochrane, Science Direct, and EMBASE via OVID were searched up to August 2017. Only randomized controlled clinical trials (RCT) using antibiotics were included. Outcome measures were set on dental implant failures or postoperative infection incidence after dental implant surgery. Three reviewers independently undertook risk of bias assessment and data extraction. Stratified meta-analyses of binary data using fixed-effects models were performed using Stata 14.0. The risk ratio (RR) and 95% confidence interval (CI) were estimated. Nine articles were included corresponding to 15 RCTs. All RCTs tested only oral amoxicillin. Implant-failure analysis: overall RR = 0.53 (P = .005, 95% CI: 0.34-0.82) and overall NNT = 55 (95% CI, 33-167). Single-dose oral amoxicillin preoperatively (SDOAP) is beneficial (RR = 0.50, CI: 0.29-0.86. P = .012), when compared to postoperative oral amoxicillin (POA): RR = 0.60, CI: 0.28-1.30. P = .197. Postoperative-infection analysis: overall RR = 0.76 (P = 0.250, 95% CI: 0.47-1.22). Neither SDOAP (RR = 0.82, CI = 0.46-1.45, P = .488) nor POA (RR = 0.64, CI = 0.27-1.51, P = .309) are beneficial. I 2  = 0.0%, chi-squared tests P ≈ 1. Only SDOAP is effective and efficacious at preventing implant failures, but it was not significant for postoperative infections following dental implant surgeries. Copyright © 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

  1. SLAC divertor channel entrance thermal stress analysis

    International Nuclear Information System (INIS)

    Johnson, G.L.; Stein, W.; Lu, S.C.; Riddle, R.A.

    1985-01-01

    X-ray beams emerging from the new SLAC electron-positron storage ring (PEP) impinge on the entrance to tangential divertor channels causing highly localized heating in the channel structure. Analyses were completed to determine the temperatures and thermally-induced stresses due to this heating. These parts are cooled with water flowing axially over them at 30 0 C. The current design and operating conditions should result in the entrance to the new divertor channel operating at a peak temperature of 123 0 C with a peak thermal stress at 91% of yield. Any micro-cracks that form due to thermally-induced stresses should not propagate to the coolant wall nor form a path for the coolant to leak into the storage ring vacuum. 34 figs., 4 tabs

  2. Analysis of primary teacher stress' sources

    Directory of Open Access Journals (Sweden)

    Katja Depolli Steiner

    2011-12-01

    Full Text Available Teachers are subject to many different work stressors. This study focused on differences in intensity and frequency of potential stressors facing primary schoolteachers and set the goal to identify the most important sources of teacher stress in primary school. The study included 242 primary schoolteachers from different parts of Slovenia. We used Stress Inventory that is designed for identification of intensity and frequency of 49 situations that can play the role of teachers' work stressors. Findings showed that the major sources of stress facing teachers are factors related to work overload, factors stemming from pupils' behaviour and motivation and factors related to school system. Results also showed some small differences in perception of stressors in different groups of teachers (by gender and by teaching level.

  3. Dental arch changes associated with rapid maxillary expansion: A retrospective model analysis study

    Directory of Open Access Journals (Sweden)

    Ivor M D′Souza

    2015-01-01

    Full Text Available Introduction: Transverse deficiency of the maxilla is a common clinical problem in orthodontics and dentofacial orthopedics. Transverse maxillary deficiency, isolated or associated with other dentofacial deformities, results in esthetic and functional impairment giving rise to several clinical manifestations such as asymmetrical facial growth, positional and functional mandibular deviations, altered dentofacial esthetics, adverse periodontal responses, unstable dental tipping, and other functional problems. Orthopedic maxillary expansion is the preferred treatment approach to increase the maxillary transverse dimension in young patients by splitting of the mid palatal suture. This orthopedic procedure has lately been subject of renewed interest in orthodontic treatment mechanics because of its potential for increasing arch perimeter to alleviate crowding in the maxillary arch without adversely affecting facial profile. Hence, the present investigation was conducted to establish a correlation between transverse expansion and changes in the arch perimeter, arch width and arch length. Methods: For this purpose, 10 subjects (five males, five females were selected who had been treated by rapid maxillary expansion (RME using hyrax rapid palatal expander followed by fixed mechanotherapy (PEA. Pretreatment (T1, postexpansion (T2, and posttreatment (T3 dental models were compared for dental changes brought about by RME treatment and its stability at the end of fixed mechanotherapy. After model measurements were made, the changes between T1-T2, T2-T3 and T1-T3 were determined for each patient. The mean difference between T1-T2, T2-T3 and T1-T3 were compared to assess the effects of RME on dental arch measurements. Results are expressed as mean ± standard deviation and are compared by repeated measures analysis of variance followed by a post-hoc test. Arch perimeter changes are correlated with changes in arch widths at the canine, premolar and molar

  4. Systemic Assessment of Patients Undergoing Dental Implant Surgeries: A Trans- and Post-operative Analysis.

    Science.gov (United States)

    Byakodi, Sanjay; Kumar, Sachin; Reddy, Rajesh Kumar; Kumar, Vipin; Sepolia, Shipra; Gupta, Shivangi; Singh, Harkanwal Preet

    2017-01-01

    Procedure-related and patient-related factors influence the prognosis of dental implants to a major extent. Hence, we aimed to evaluate and analyze various systemic factors in patients receiving dental implants. Fifty-one patients were included in the study, in which a total of 110 dental implants were placed. Complete examination of the subjects was done before and after placement of dental implants. Implant surgery was planned, and osseointegrated dental implants were placed in the subjects. Postoperative evaluation of the dental implant patients was done after 3 weeks. Anxiety levels were determined using State-Trait Anxiety Inventory (STAI) questionnaire on the surgery day and after 1 week of surgery. The participant describes how they feel at the moment by responding to twenty items as follows: (1) absolutely not, (2) slightly, (3) somewhat, or (4) very much. All the results were recorded and statistical analyzed by SPSS software. Out of 51, 29 patients were males while 22 were females, with ratio of 1.32:1. Female patients' mean age was 50.18 years while male patients' mean age was 52.71 years, with statistically nonsignificant difference between them. Functional rehabilitation was the main purpose of choosing dental implants in more than 90% of the subjects. Diameter of 3.75 mm was the shortest implants to be placed in the present study, whereas in terms of length, 8.5 mm was the shortest length of dental implant used in the present study. Tooth area in which maximum implants were placed in our study was 36 tooth region. Maximum implants were placed in Type II bone quality ( n = 38). Implants installed in the mandible were clamped more efficiently than implants placed in the maxilla ( P < 0.001). The difference of average STAI-State subscore before and after the surgery was statistically significant ( P < 0.05; significant). Mandibular dental implants show more clamping (torque) than maxillary dental implants.

  5. Bioinspired design of dental multilayers.

    Science.gov (United States)

    Huang, M; Wang, R; Thompson, V; Rekow, D; Soboyejo, W O

    2007-01-01

    This paper considers the use of bioinspired functionally graded structures in the design of dental multi-layers that are more resistant to sub-surface crack nucleation. Unlike existing dental crown restorations that give rise to high stress concentration, the functionally graded layers (between crown materials and the joins that attach them to dentin) are shown to promote significant reductions in stress and improvements in the critical crack size. Special inspiration is drawn from the low stress concentrations associated with the graded distributions in the dentin-enamel-junction (DEJ). The implications of such functionally graded structures are also discussed for the design of dental restorations.

  6. Stress determination and geomechanical stability analysis of an oil ...

    Indian Academy of Sciences (India)

    Practical data including geomechanical parameters along with drilling data from one of Iranian oilfields, Mansouri-54 well have been utilized in this analysis. in situ stress was determined using stress polygon method and conducting hydraulic fracturing data in the field. Analytical solution using the Mogi–Coulomb and the ...

  7. Thermal stresses in the space shuttle orbiter: Analysis versus test

    International Nuclear Information System (INIS)

    Grooms, H.R.; Gibson, W.F. Jr.; Benson, P.L.

    1984-01-01

    Significant temperature differences occur between the internal structure and the outer skin of the Space Shuttle Orbiter as it returns from space. These temperature differences cause important thermal stresses. A finite element model containing thousands of degrees of freedom is used to predict these stresses. A ground test was performed to verify the prediction method. The analysis and test results compare favorably. (orig.)

  8. Preliminary thermal and stress analysis of the SINQ window

    International Nuclear Information System (INIS)

    Heidenreich, G.

    1991-01-01

    Preliminary results of a finite element analysis for the SINQ proton beam window are presented. Temperatures and stresses are calculated in an axisymmetric model. As a result of these calculations, the H 2 O-cooled window (safety window) could be redesigned in such a way that plastic deformation resulting from excessive stress in some areas is avoided. (author)

  9. Internal stress analysis by acoustic polarimetry

    International Nuclear Information System (INIS)

    Rouge, Jean; Robert, Andre

    The associated improvements of acoustics and electronics allow the field of applications relative to the ultrasonic methods to be extended to the non destructive control of materials and structures. Thus, the acoustical polarimetry is a new method allowing the measurement in orientation and intensity of residual or induced internal stresses in metals or other materials [fr

  10. Analysis of residual stresses in welded joints

    International Nuclear Information System (INIS)

    Lemos, F.L. de.

    1984-01-01

    The study of two stress measurements techniques is presented showing experimental results that allows to evaluate its reliability. These two methods are 'The Center Hole Drilling Method' and 'The Overcoring' and they are considered semi-destructive methods. (E.G.) [pt

  11. What is dental ecology?

    Science.gov (United States)

    Cuozzo, Frank P; Sauther, Michelle L

    2012-06-01

    Teeth have long been used as indicators of primate ecology. Early work focused on the links between dental morphology, diet, and behavior, with more recent years emphasizing dental wear, microstructure, development, and biogeochemistry, to understand primate ecology. Our study of Lemur catta at the Beza Mahafaly Special Reserve, Madagascar, has revealed an unusual pattern of severe tooth wear and frequent tooth loss, primarily the result of consuming a fallback food for which these primates are not dentally adapted. Interpreting these data was only possible by combining our areas of expertise (dental anatomy [FC] and primate ecology [MS]). By integrating theoretical, methodological, and applied aspects of both areas of research, we adopted the term "dental ecology"-defined as the broad study of how teeth respond to the environment. Specifically, we view dental ecology as an interpretive framework using teeth as a vehicle for understanding an organism's ecology, which builds upon earlier work, but creates a new synthesis of anatomy and ecology that is only possible with detailed knowledge of living primates. This framework includes (1) identifying patterns of dental pathology and tooth use-wear, within the context of feeding ecology, behavior, habitat variation, and anthropogenic change, (2) assessing ways in which dental development and biogeochemical signals can reflect habitat, environmental change and/or stress, and (3) how dental microstructure and macro-morphology are adapted to, and reflect feeding ecology. Here we define dental ecology, provide a short summary of the development of this perspective, and place our new work into this context. Copyright © 2012 Wiley Periodicals, Inc.

  12. Residual Stress Analysis Based on Acoustic and Optical Methods

    Directory of Open Access Journals (Sweden)

    Sanichiro Yoshida

    2016-02-01

    Full Text Available Co-application of acoustoelasticity and optical interferometry to residual stress analysis is discussed. The underlying idea is to combine the advantages of both methods. Acoustoelasticity is capable of evaluating a residual stress absolutely but it is a single point measurement. Optical interferometry is able to measure deformation yielding two-dimensional, full-field data, but it is not suitable for absolute evaluation of residual stresses. By theoretically relating the deformation data to residual stresses, and calibrating it with absolute residual stress evaluated at a reference point, it is possible to measure residual stresses quantitatively, nondestructively and two-dimensionally. The feasibility of the idea has been tested with a butt-jointed dissimilar plate specimen. A steel plate 18.5 mm wide, 50 mm long and 3.37 mm thick is braze-jointed to a cemented carbide plate of the same dimension along the 18.5 mm-side. Acoustoelasticity evaluates the elastic modulus at reference points via acoustic velocity measurement. A tensile load is applied to the specimen at a constant pulling rate in a stress range substantially lower than the yield stress. Optical interferometry measures the resulting acceleration field. Based on the theory of harmonic oscillation, the acceleration field is correlated to compressive and tensile residual stresses qualitatively. The acoustic and optical results show reasonable agreement in the compressive and tensile residual stresses, indicating the feasibility of the idea.

  13. The economic costs and benefits of dental education: an empirical analysis.

    Science.gov (United States)

    Stafford, Gary L; Nourzad, Farrokh; Lobb, William K; Beall, Jason R

    2014-11-01

    The rising costs associated with obtaining a dental education have caused some to question the financial benefit of pursuing a dental degree. There is a concern that recent graduates may have difficulty finding professional opportunities that provide the income necessary to service their accumulated educational debt. The aim of this study was to evaluate the trends in educational costs to aid in making an accurate appraisal of the financial benefit of a dental education. Adjusted into constant dollar terms, data from a variety of sources were collected for economic variables such as tuition, fees, student indebtedness, and dentists' earnings. These variables were then analyzed to determine the true costs and benefits of obtaining a dental education. The results showed that, over the course of the last decade, educational costs increased faster than the real net income of practicing dentists, which led to a decline in the return on investment in dental education. However, regardless of an applicant's choice of public or private dental school, there continues to be a positive economic return on students' commitment of both financial resources and time to receive a dental education.

  14. Materials properties, loads, and stress analysis, Spartan REM: Appendix A

    Science.gov (United States)

    Marlowe, D. S.; West, E. J.

    1984-01-01

    The mechanical properties, load tests, and stress analysis of the Spartan Release Engagement Mechanism (REM) is presented. The fracture properties of the components of the unit are also discussed. Detailed engineering drawings are included.

  15. Finite element analysis of thermal stress distribution in different ...

    African Journals Online (AJOL)

    Nigerian Journal of Clinical Practice • Jan-Feb 2016 • Vol 19 • Issue 1. Abstract ... Key words: Amalgam, finite element method, glass ionomer cement, resin composite, thermal stress ... applications for force analysis and assessment of different.

  16. Role stress amongst nurses at the workplace: concept analysis.

    Science.gov (United States)

    Riahi, Sanaz

    2011-09-01

    The present study explicates the concept of role stress amongst nurses through an analysis adopted from Walker and Avant; Strategies for Theory Construction in Nursing, 4th edn, Prentice Hall, New Jersey, NY. Role stress has become a significant problem amongst nurses and has created much distress leading to burnout among many in the nursing profession. It is significant to analyse the concept of role stress and its relative attributes and consequences, in order to recognize the necessary antecedents needed to create better conditions for nurses at the workplace. A modified method developed by Walker and Avant was used for this concept analysis. A model representing the concept of role stress was developed through careful consideration of the attributes, consequences, antecedents and empirical referents of role stress. The concept analysis of role stress among nurses at the workplace recognized the vulnerability of the nursing discipline towards burnout and distress in general. It is critical to be aware of the current state of health care and note the increased workload created for nurses. Nurses are at a greater vulnerability for role stress, making it imperative for health care organizations to critically evaluate and establish preventative measures for the concept of role stress. 2011 Blackwell Publishing Ltd.

  17. Use of quality measurement across US dental delivery systems: a qualitative analysis.

    Science.gov (United States)

    Alrqiq, Hosam M; Edelstein, Burton L

    2016-03-01

    Dentistry is increasingly challenged by payers and the public to demonstrate quality measurement (QM) activities that substantiate value. Unknown is how various components of the US oral health-care financing and delivery systems have adopted QM. The objective of this study is to explore QM activities by US dental delivery, management, financing, and related organizations. Using a structured interview guide based on a novel conceptual framework that incorporates factors influencing QM intention, adoption, and implementation, 19 key informant interviews were conducted. Informants represented safety net delivery programs (health center, nonprofit mobile, hospital-based, Veterans Administration, and tribal dental programs), private delivery organizations (private practice, closed panel HMO, and for-profit mobile dental programs), training programs that deliver care (dental and dental therapy programs), management organizations (private and Medicaid group practice management companies), care financing organizations (Medicaid managed care plan, state Medicaid program, dental benefits companies), and dental quality organizations (institute and dental professional organization). Interviews were transcribed and analyzed qualitatively. Informants report wide variation in the intensity of QM efforts with organizational leadership cited as most influential. Motivation to adopt QM efforts is more often internal than imposed. Data management and information technology both facilitate and limit QM activities. QM activities are associated with operational improvements including use of guidelines and refinements of mission. Organizational type and size appear to influence QM programs. The current status of QM is highly variable across dental organizations because organizational leadership, needs, and requirements vary according to mission and structure. © 2015 American Association of Public Health Dentistry.

  18. Hypnotic approach during dental treatment: analysis of descriptive data of a case series.

    Science.gov (United States)

    Ferdeghini, R; Lauritano, D; Tagliabue, A; Tettamanti, L

    2018-01-01

    Anxiety and worry are important components that affect the patient’s behaviour during dental sessions and influence the effectiveness of dental treatment. Psychological approach and hypnotic approach (HA) have in recent years assumed increasing prominence as effective treatment regimes. Dentists have used a number of methods in the management of dental phobic disorders through HA. However the efficacy of HA in controlling anxiety and worry is controversial. The aim of the present study is to describe the response of patient to HA during dental treatment. The study of the population consisted of 42 patients, these being 50% random sample of consecutive patients presenting to a private practise over an 8-year period. In 38 patients HA was induced. 4 patients were not susceptible to HA. There were 20 women (52.6%) and 18 men (47.3%) with a mean age of 47.2 years (range 30-69 years). At the end of dental sessions with HA all the patients were asked to answer the following questions: 1) Have you been hypnotized in the past? 2) Were you aware of dental applications of HA? 3) How do you evaluate the use of this technique in the field of dental care? 4) Do you think that you can use this procedure in the future too? The answers were as follows: question 1: 34 patients answered yes, 4 no; question 2: 34 answered yes, 4 no; question 3: the choice was between “very useful”, “useful”, “Indifferent”, “to avoid”. Twenty-nine patients indicated “very useful”, and 9 “useful”; question 4: the choice was between yes and no. All patients answered yes. This study adds further support to a growing body of evidence relating HA to a better compliance to dental treatment. The dental situation in particular lends itself to carefully controlled investigation providing further evidence to support a robust theory.

  19. Information system analysis of an e-learning system used for dental restorations simulation.

    Science.gov (United States)

    Bogdan, Crenguţa M; Popovici, Dorin M

    2012-09-01

    The goal of using virtual and augmented reality technologies in therapeutic interventions simulation, in the fixed prosthodontics (VirDenT) project, is to increase the quality of the educational process in dental faculties, by assisting students in learning how to prepare teeth for all-ceramic restorations. Its main component is an e-learning virtual reality-based software system that will be used for the developing skills in grinding teeth, needed in all-ceramic restorations. The complexity of the domain problem that the software system dealt with made the analysis of the information system supported by VirDenT necessary. The analysis contains the following activities: identification and classification of the system stakeholders, description of the business processes, formulation of the business rules, and modelling of business objects. During this stage, we constructed the context diagram, the business use case diagram, the activity diagrams and the class diagram of the domain model. These models are useful for the further development of the software system that implements the VirDenT information system. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  20. Quantitative analysis of diverse Lactobacillus species present in advanced dental caries.

    Science.gov (United States)

    Byun, Roy; Nadkarni, Mangala A; Chhour, Kim-Ly; Martin, F Elizabeth; Jacques, Nicholas A; Hunter, Neil

    2004-07-01

    Our previous analysis of 65 advanced dental caries lesions by traditional culture techniques indicated that lactobacilli were numerous in the advancing front of the progressive lesion. Production of organic acids by lactobacilli is considered to be important in causing decalcification of the dentinal matrix. The present study was undertaken to define more precisely the diversity of lactobacilli found in this environment and to quantify the major species and phylotypes relative to total load of lactobacilli by real-time PCR. Pooled DNA was amplified by PCR with Lactobacillus genus-specific primers for subsequent cloning, sequencing, and phylogenetic analysis. Based on 16S ribosomal DNA sequence comparisons, 18 different phylotypes of lactobacilli were detected, including strong representation of both novel and gastrointestinal phylotypes. Specific PCR primers were designed for nine prominent species, including Lactobacillus gasseri, L. ultunensis, L. salivarius, L. rhamnosus, L. casei, L. crispatus, L. delbrueckii, L. fermentum, and L. gallinarum. More than three different species were identified as being present in most of the dentine samples, confirming the widespread distribution and numerical importance of various Lactobacillus spp. in carious dentine. Quantification by real-time PCR revealed various proportions of the nine species colonizing carious dentine, with higher mean loads of L. gasseri and L. ultunensis than of the other prevalent species. The findings provide a basis for further characterization of the pathogenicity of Lactobacillus spp. in the context of extension of the carious lesion.

  1. CT interpretation of craniofacial anomalies: a comparative analysis by undergraduate dental students

    International Nuclear Information System (INIS)

    Gaia, Bruno Felipe; Perella, Andreia; Cara, Ana Claudia Ballet de; Antunes, Jose Leopoldo Ferreira; Cavalcanti, Marcelo Gusmao Paraiso

    2005-01-01

    The aim of this study was to evaluate the accuracy and reproducibility of computed tomography (CT) image interpretation made in axial slices (2D-CT) and 3D reconstructed images (3D-CT) of patients with craniofacial anomalies. The analyses were made by undergraduate dental students, and compared with the diagnoses considered upon surgical intervention. Computed tomography of 43 patients were analyzed independently by three calibrated examiners (undergraduate students) with, respectively, one, two, and three semesters of experience in craniofacial CT training and interpretation. The analysis of 2D-CT and 3D-CT images were performed at distinct times using an independent workstation associated with a specific computer graphics software for volumetric images. The analysis of inter-examiner agreement and of the agreement between observers and the gold standard was performed using the Kappa test. The accuracy evaluation presented a progressively higher value for examiners with progressively broader experience in 2D-CT and 3D-CT image interpretation. 3D-CT analyses allowed a higher inter-examiner agreement (1 - 0.896) than 2D-CT analyses (1 - 0.614). 3D-CT was considered more precise and accurate than 2D-CT for all students' evaluations. The reproducibility and accuracy varied according to the experience in CT interpretation, and the most experienced student achieved results closer to the gold standard. (author)

  2. Computer-aided analysis of digital dental impressions obtained from intraoral and extraoral scanners.

    Science.gov (United States)

    Bohner, Lauren Oliveira Lima; De Luca Canto, Graziela; Marció, Bruno Silva; Laganá, Dalva Cruz; Sesma, Newton; Tortamano Neto, Pedro

    2017-11-01

    The internal and marginal adaptation of a computer-aided design and computer-aided manufacturing (CAD-CAM) prosthesis relies on the quality of the 3-dimensional image. The quality of imaging systems requires evaluation. The purpose of this in vitro study was to evaluate and compare the trueness of intraoral and extraoral scanners in scanning prepared teeth. Ten acrylic resin teeth to be used as a reference dataset were prepared according to standard guidelines and scanned with an industrial computed tomography system. Data were acquired with 4 scanner devices (n=10): the Trios intraoral scanner (TIS), the D250 extraoral scanner (DES), the Cerec Bluecam intraoral scanner (CBIS), and the Cerec InEosX5 extraoral scanner (CIES). For intraoral scanners, each tooth was digitized individually. Extraoral scanning was obtained from dental casts of each prepared tooth. The discrepancy between each scan and its respective reference model was obtained by deviation analysis (μm) and volume/area difference (μm). Statistical analysis was performed using linear models for repeated measurement factors test and 1-way ANOVA (α=.05). No significant differences in deviation values were found among scanners. For CBIS and CIES, the deviation was significantly higher (PDentistry. Published by Elsevier Inc. All rights reserved.

  3. Non-Destructive Analysis of Basic Surface Characteristics of Titanium Dental Implants Made by Miniature Machining

    Science.gov (United States)

    Babík, Ondrej; Czán, Andrej; Holubják, Jozef; Kameník, Roman; Pilc, Jozef

    2016-12-01

    One of the most best-known characteristic and important requirement of dental implant is made of biomaterials ability to create correct interaction between implant and human body. The most implemented material in manufacturing of dental implants is titanium of different grades of pureness. Since most of the implant surface is in direct contact with bone tissue, shape and integrity of said surface has great influence on the successful osseointegration. Among other characteristics of titanium that predetermine ideal biomaterial, it shows a high mechanical strength making precise machining miniature Increasingly difficult. The article is focused on evaluation of the resulting quality, integrity and characteristics of dental implants surface after machining.

  4. Responses to Fiscal Stress: A Comparative Analysis

    Science.gov (United States)

    2013-12-01

    of “a significant decline in market share by the middle of the 20th century as travelers and shippers turned increasingly to airlines, trucks, and...1995). Intercity passenger rail: Financial and operating conditions threaten Amtrak’s long-term viability (GAO-95-71). Washington, DC: U.S...I. (1980). Retrenchment and flexibility in public organizations. Fiscal Stress and Public Policy, 159–178. Scheinberg, P. F. (1998). Intercity

  5. Municipal solid waste effective stress analysis

    International Nuclear Information System (INIS)

    Shariatmadari, Nader; Machado, Sandro Lemos; Noorzad, Ali; Karimpour-Fard, Mehran

    2009-01-01

    The mechanical behavior of municipal solid waste (MSW) has attracted the attention of many researchers in the field of geo-environmental engineering in recent years and several aspects of waste mechanical response under loading have been elucidated. However, the mechanical response of MSW materials under undrained conditions has not been described in detail to date. The knowledge of this aspect of the MSW mechanical response is very important in cases involving MSW with high water contents, seismic ground motion and in regions where landfills are built with poor operation conditions. This paper presents the results obtained from 26 large triaxial tests performed both in drained and undrained conditions. The results were analyzed taking into account the waste particles compressibility and the deformation anisotropy of the waste samples. The waste particles compressibility was used to modify the Terzaghi effective stress equation, using the Skempton (1961) proposition. It is shown that the use of the modified effective stress equation led to much more compatible shear strength values when comparing Consolidated-Drained (CD) and Consolidated-Undrained (CU), results, explaining the high shear strength values obtained in CU triaxial tests, even when the pore pressure is almost equal to the confining stress.

  6. Assessment of the stress transmitted to dental implants connected to screw-retained bars using different casting techniques.

    Science.gov (United States)

    Haselhuhn, Klaus; Marotti, Juliana; Tortamano, Pedro; Weiss, Claudia; Suleiman, Lubna; Wolfart, Stefan

    2014-12-01

    Passive fit of the prosthetic superstructure is important to avoid complications; however, evaluation of passive fit is not possible using conventional procedures. Thus, the aim of this study was to check and locate mechanical stress in bar restorations fabricated using two casting techniques. Fifteen patients received four implants in the interforaminal region of the mandible, and a bar was fabricated using either the cast-on abutment or lost-wax casting technique. The fit accuracy was checked according to the Sheffield's test criteria. Measurements were recorded on the master model with a gap-free, passive fit using foil strain gauges both before and after tightening the prosthetic screws. Data acquisition and processing was analyzed with computer software and submitted to statistical analysis (ANOVA). The greatest axial distortion was at position 42 with the cast-on abutment technique, with a mean distortion of 450 μm/m. The lowest axial distortion occurred at position 44 with the lost-wax casting technique, with a mean distortion of 100 μm/m. The minimal differences between the means of axial distortion do not indicate any significant differences between the techniques (P = 0.2076). Analysis of the sensor axial distortion in relation to the implant position produced a significant difference (P casting techniques, with no significant difference between the sides.

  7. Longitudinal Analysis of Student Performance in a Dental Hygiene Distance Education Program.

    Science.gov (United States)

    Olmsted, Jodi L.

    2002-01-01

    Examined over the course of five years whether learners who receive face-to-face instruction in a dental hygiene program performed statistically better on established benchmark assessments than learners at a distance. Found no significant differences. (EV)

  8. A Descriptive Analysis of Dental Conditions Occurring During Conflicts, Deployments, and Field Training Exercises

    National Research Council Canada - National Science Library

    Roberts, Janet

    1999-01-01

    This study was designed to determine the types and incidence of dental conditions that occur in a variety of operational scenarios and to identify the appropriate mix of supplies for treating those conditions...

  9. X-ray stress analysis in textured polycrystalline materials

    International Nuclear Information System (INIS)

    Yokoyama, Ryouichi; Harada, Jimpei

    2010-01-01

    The relationship between stress and strain in polycrystalline materials with fibre texture is examined on the basis of the strain analysis in the constituent crystallites within the Reuss approximation. By introducing the symmetry of reciprocal lattices for the constituent crystallites, the physical meaning of taking an average of the strains observed by X-ray diffraction (XRD) is made clear. By using formulae obtained by the present treatment for the stress-strain relation in cubic specimens with fibre texture in the Laue classes m3-bar m hkl Bragg reflections with h≠k≠l split into doublets owing to the existence of crystallites with two different orientations under the stress field. This technique was confirmed by the profile analysis in XRD data observed for reflections of 222 and 420 in a cubic TiN thin film sputtered on a polyimide film. The technique of the stress analysis and its confirmation are introduced. (author)

  10. Association between Dental Caries and BMI in Children: A Systematic Review and Meta-Analysis.

    Science.gov (United States)

    Chen, Dongru; Zhi, Qinghui; Zhou, Yan; Tao, Ye; Wu, Liping; Lin, Huancai

    2018-01-01

    Research on the association between dental caries and body mass index (BMI) in children has shown contradictory results; thus we aimed to examine the association between dental caries and the full range of BMI classes among children. We comprehensively searched PubMed, Embase, and the Cochrane Library for studies published prior to March 2017. Articles comparing dental caries among the full range of BMI classes for children below 18 years of both genders were included. Fourteen studies were eligible for this study. Basic information - i.e., first author, published year, study design, country, sample size, age, type of dental caries index and BMI, main results and conclusions, and means and standard deviations of the dental caries indexes used - was pooled. The weighted mean differences and corresponding 95% confidence intervals for dental caries between children with abnormal weight and those with normal weight were analyzed. Generally, no significant differences in caries were found between any abnormal-weight group and the normal-weight group for both primary and permanent teeth. Sensitivity analyses showed that the obese group had more caries than the normal-weight group in their primary teeth. Significantly more caries was found among the overweight and obese children in both primary and permanent teeth in high-income countries, but not in low- and middle-income countries. We recommend that further studies use suitable sample sizes, unify the criteria for BMI categorization and the dental caries index, and investigate the confounding factors that might influence dental caries and BMI. © 2018 S. Karger AG, Basel.

  11. Individual and contextual factors influencing dental health care utilization by preschool children: a multilevel analysis

    Science.gov (United States)

    Piovesan, Chaiana; Ardenghi, Thiago Machado; Mendes, Fausto Medeiros; Agostini, Bernardo Antonio; Michel-Crosato, Edgard

    2017-03-30

    The effect of contextual factors on dental care utilization was evaluated after adjustment for individual characteristics of Brazilian preschool children. This cross-sectional study assessed 639 preschool children aged 1 to 5 years from Santa Maria, a town in Rio Grande do Sul State, located in southern Brazil. Participants were randomly selected from children attending the National Children's Vaccination Day and 15 health centers were selected for this research. Visual examinations followed the ICDAS criteria. Parents answered a questionnaire about demographic and socioeconomic characteristics. Contextual influences on children's dental care utilization were obtained from two community-related variables: presence of dentists and presence of workers' associations in the neighborhood. Unadjusted and adjusted multilevel logistic regression models were used to describe the association between outcome and predictor variables. A prevalence of 21.6% was found for regular use of dental services. The unadjusted assessment of the associations of dental health care utilization with individual and contextual factors included children's ages, family income, parents' schooling, mothers' participation in their children's school activities, dental caries, and presence of workers' associations in the neighborhood as the main outcome covariates. Individual variables remained associated with the outcome after adding contextual variables in the model. In conclusion, individual and contextual variables were associated with dental health care utilization by preschool children.

  12. Individual and contextual factors influencing dental health care utilization by preschool children: a multilevel analysis

    Directory of Open Access Journals (Sweden)

    Chaiana PIOVESAN

    2017-03-01

    Full Text Available Abstract The effect of contextual factors on dental care utilization was evaluated after adjustment for individual characteristics of Brazilian preschool children. This cross-sectional study assessed 639 preschool children aged 1 to 5 years from Santa Maria, a town in Rio Grande do Sul State, located in southern Brazil. Participants were randomly selected from children attending the National Children’s Vaccination Day and 15 health centers were selected for this research. Visual examinations followed the ICDAS criteria. Parents answered a questionnaire about demographic and socioeconomic characteristics. Contextual influences on children’s dental care utilization were obtained from two community-related variables: presence of dentists and presence of workers’ associations in the neighborhood. Unadjusted and adjusted multilevel logistic regression models were used to describe the association between outcome and predictor variables. A prevalence of 21.6% was found for regular use of dental services. The unadjusted assessment of the associations of dental health care utilization with individual and contextual factors included children’s ages, family income, parents’ schooling, mothers’ participation in their children’s school activities, dental caries, and presence of workers’ associations in the neighborhood as the main outcome covariates. Individual variables remained associated with the outcome after adding contextual variables in the model. In conclusion, individual and contextual variables were associated with dental health care utilization by preschool children.

  13. Comparative analysis of rationale used by dentists and patient for final esthetic outcome of dental treatment.

    Science.gov (United States)

    Reddy, S Varalakshmi; Madineni, Praveen Kumar; Sudheer, A; Gujjarlapudi, Manmohan Choudary; Sreedevi, B; Reddy, Patelu Sunil Kumar

    2013-05-01

    To compare and evaluate the perceptions of esthetics among dentists and patients regarding the final esthetic outcome of a dental treatment. Esthetics is a matter of perception and is associated with the way different people look at an object. What constitutes esthetic for a particular person may not be acceptable for another. Hence it is subjective in nature. This becomes more obvious during the post-treatment evaluation of esthetics by dentist and the concerned patient. Opinion seldom matches. Hence, the study is a necessary part of the process of understanding the mind of dentist and patient regarding what constitutes esthetics. A survey has been conducted by means of a questionnaire consisting of 10 questions, on two groups of people. First group consists of 100 dentists picked at random in Kanyakumari district of Tamil Nadu, India. Second group consisted of 100 patients who required complete denture prosthesis. The second group was divided into two subgroups A and B. Subgroup A consisting of 50 men and subgroup B consisting of 50 women. In each subgroup 25 patients were selected in age group of 40 to 50 and 25 patients were selected in the age group of 50 to 60. The questionnaire was given to both the groups and asked to fill up, which was then statistically analyzed to look for patterns of thought process among them. Results were subjected to statistical analysis by Student's t-test. Perceptions of esthetics differs from dentist who is educated regarding esthetic principles of treatment and a patient who is not subjected to such education. Since, the questions were formulated such that patients could better understand the underlying problem, the final outcome of survey is a proof that dentists need to take into account what the patient regards as esthetics in order to provide a satisfactory treatment. CLINICAL AND ACADEMIC SIGNIFICANCE: The current study helps the dentist to better educate the patient regarding esthetics so that patient appreciates the final

  14. Analysis of risk factors for cluster behavior of dental implant failures.

    Science.gov (United States)

    Chrcanovic, Bruno Ramos; Kisch, Jenö; Albrektsson, Tomas; Wennerberg, Ann

    2017-08-01

    Some studies indicated that implant failures are commonly concentrated in few patients. To identify and analyze cluster behavior of dental implant failures among subjects of a retrospective study. This retrospective study included patients receiving at least three implants only. Patients presenting at least three implant failures were classified as presenting a cluster behavior. Univariate and multivariate logistic regression models and generalized estimating equations analysis evaluated the effect of explanatory variables on the cluster behavior. There were 1406 patients with three or more implants (8337 implants, 592 failures). Sixty-seven (4.77%) patients presented cluster behavior, with 56.8% of all implant failures. The intake of antidepressants and bruxism were identified as potential negative factors exerting a statistically significant influence on a cluster behavior at the patient-level. The negative factors at the implant-level were turned implants, short implants, poor bone quality, age of the patient, the intake of medicaments to reduce the acid gastric production, smoking, and bruxism. A cluster pattern among patients with implant failure is highly probable. Factors of interest as predictors for implant failures could be a number of systemic and local factors, although a direct causal relationship cannot be ascertained. © 2017 Wiley Periodicals, Inc.

  15. Disilicate Dental Ceramic Surface Preparation by 1070 nm Fiber Laser: Thermal and Ultrastructural Analysis

    Directory of Open Access Journals (Sweden)

    Carlo Fornaini

    2018-01-01

    Full Text Available Lithium disilicate dental ceramic bonding, realized by using different resins, is strictly dependent on micro-mechanical retention and chemical adhesion. The aim of this in vitro study was to investigate the capability of a 1070 nm fiber laser for their surface treatment. Samples were irradiated by a pulsed fiber laser at 1070 nm with different parameters (peak power of 5, 7.5 and 10 kW, repetition rate (RR 20 kHz, speed of 10 and 50 mm/s, and total energy density from 1.3 to 27 kW/cm2 and the thermal elevation during the experiment was recorded by a fiber Bragg grating (FBG temperature sensor. Subsequently, the surface modifications were analyzed by optical microscope, scanning electron microscope (SEM, and energy dispersive X-ray spectroscopy (EDS. With a peak power of 5 kW, RR of 20 kHz, and speed of 50 mm/s, the microscopic observation of the irradiated surface showed increased roughness with small areas of melting and carbonization. EDS analysis revealed that, with these parameters, there are no evident differences between laser-processed samples and controls. Thermal elevation during laser irradiation ranged between 5 °C and 9 °C. A 1070 nm fiber laser can be considered as a good device to increase the adhesion of lithium disilicate ceramics when optimum parameters are considered.

  16. Construct Validity of the Korean Dental Licensing Examination using Confirmatory Factor Analysis

    Directory of Open Access Journals (Sweden)

    Mi Kyoung Yim

    2005-06-01

    Full Text Available Confirmatory factor analysis based on a measurement model of a structural equation model was used to test the construct validity of 13 subjects in the Korean Dental Licensing Examination (KDLE. The results of 1,086 examinees who wrote the KDLE in 2004 were analyzed. The thirteen subjects were classified into 62 major categories and 122 intermediate categories. There were 364 items. A hierarchical model was constructed, including major and intermediate categories. The impact of the variables was determined by the standardized regression coefficient that related latent and measured variables in the measurement model. The KDLE showed a high goodness-of-fit with a root mean square error of approximation of 0.030 and a non-normed fit index of 0.998. When the latent variables for the major and intermediate categories were analyzed, the standardized regression coefficients of all of the subjects, with the exception of Health and Medical Legislation, were significant. From the result, we concluded that the 13 subjects showed constructive validity. In addition, the study model and data were very compatible. The subject Health and Medical Legislation had a low explanatory impact with respect to testing the ability of dentists to perform their jobs. This study suggests that similar psychometric studies are needed before integrating or deleting subjects on the KDLE, and to improve item development.

  17. Raman spectroscopy analysis of dental enamel treated with whitening product - Influence of saliva in the remineralization

    Science.gov (United States)

    Silveira, J.; Coutinho, S.; Marques, D.; Castro, J.; Mata, A.; Carvalho, M. L.; Pessanha, S.

    2018-06-01

    In this work we present the analysis of dental enamel treated with an over-the-counter whitening product, bought in e-commerce at a very low cost, used without medical supervision in an abusive manner, in order to evaluate its demineralization action. Moreover, we studied the influence of renewal or non-renewal of saliva solution in which the specimens were stored throughout the study. The Degree of Demineralization was determined through the evaluation of the PO43- symmetric stretching band ( 959 cm-1) in Raman spectra of the specimens in different days during the course of the study. Results showed that a maximum of demineralization occurred between days 27 and 34 of application. Titration of the whitening product revealed a content of hydrogen peroxide 170-fold higher than what is allowed in Europe, according with legislation. Despite this extreme concentration of hydrogen peroxide, the demineralization was not as great as could be expected suggesting an important role of the pH of the solution in this demineralization mechanism.

  18. Reliability analysis of offshore structures using OMA based fatigue stresses

    DEFF Research Database (Denmark)

    Silva Nabuco, Bruna; Aissani, Amina; Glindtvad Tarpø, Marius

    2017-01-01

    focus is on the uncertainty observed on the different stresses used to predict the damage. This uncertainty can be reduced by Modal Based Fatigue Monitoring which is a technique based on continuously measuring of the accelerations in few points of the structure with the use of accelerometers known...... points of the structure, the stress history can be calculated in any arbitrary point of the structure. The accuracy of the estimated actual stress is analyzed by experimental tests on a scale model where the obtained stresses are compared to strain gauges measurements. After evaluating the fatigue...... stresses directly from the operational response of the structure, a reliability analysis is performed in order to estimate the reliability of using Modal Based Fatigue Monitoring for long term fatigue studies....

  19. Interlaminar stress analysis for carbon/epoxy composite space rotors

    Directory of Open Access Journals (Sweden)

    C Lian

    2016-09-01

    Full Text Available This paper extends the previous works that appears in the International Journal of Multiphysics, Varatharajoo, Salit and Goh (2010. An approach incorporating cohesive zone modelling technique is incorporated into an optimized flywheel to properly simulate the stresses at the layer interfaces. Investigation on several fiber stacking sequences are also conducted to demonstrate the effect of fiber orientations on the overall rotor stress as well as the interface stress behaviour. The results demonstrated that the rotor interlaminar stresses are within the rotor materials' ultimate strength and that the fiber direction with a combination of 45°/-45°/0° offers the best triple layer rotor among the few combinations selected for this analysis. It was shown that the present approach can facilitate also further investigation on the interface stress behaviour of rotating rotors.

  20. About Dental Amalgam Fillings

    Science.gov (United States)

    ... and Medical Procedures Dental Devices Dental Amalgam About Dental Amalgam Fillings Share Tweet Linkedin Pin it More ... should I have my fillings removed? What is dental amalgam? Dental amalgam is a dental filling material ...

  1. Dental anxiety and salivary cortisol levels before urgent dental care.

    Science.gov (United States)

    Kanegane, Kazue; Penha, Sibele S; Munhoz, Carolina D; Rocha, Rodney G

    2009-12-01

    Dental anxiety is still prevalent, despite advances in treatment, and affects the utilization of health care services. The purpose of this cross-sectional study was to determine if patients with different degrees of dental anxiety and pain undergoing emergency dental care have different stress reactions as measured by salivary cortisol. Seventy three patients completed the modified dental anxiety scale (MDAS), and described any previous dental traumatic experience. Their socio-demographic characteristics were also recorded. They also rated pain intensity on a 100 mm visual analogue scale (VAS). A saliva sample was collected before the procedure, and analyzed by enzyme immunoassay. Thirty patients were dentally anxious and forty one complained of pain. In this sample, dental anxiety was not related to gender, age, educational level and family income; however, a previous traumatic event was related to dental anxiety. There was no association between salivary cortisol concentrations and gender or dental anxiety. Patients with pain showed higher cortisol levels. When gathering patient information, the dentist should note patients' negative dental experiences in order to provide more effective, less traumatic treatment.

  2. Dental cavities

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/001055.htm Dental cavities To use the sharing features on this page, please enable JavaScript. Dental cavities are holes (or structural damage) in the ...

  3. Dental sealants

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/patientinstructions/000779.htm Dental sealants To use the sharing features on this ... case a sealant needs to be replaced. How Dental Sealants are Applied Your dentist applies sealants on ...

  4. Systemic assessment of patients undergoing dental implant surgeries: A trans- and post-operative analysis

    Directory of Open Access Journals (Sweden)

    Sanjay Byakodi

    2017-01-01

    Full Text Available Background: Procedure-related and patient-related factors influence the prognosis of dental implants to a major extent. Hence, we aimed to evaluate and analyze various systemic factors in patients receiving dental implants. Materials and Methods: Fifty-one patients were included in the study, in which a total of 110 dental implants were placed. Complete examination of the subjects was done before and after placement of dental implants. Implant surgery was planned, and osseointegrated dental implants were placed in the subjects. Postoperative evaluation of the dental implant patients was done after 3 weeks. Anxiety levels were determined using State-Trait Anxiety Inventory (STAI questionnaire on the surgery day and after 1 week of surgery. The participant describes how they feel at the moment by responding to twenty items as follows: (1 absolutely not, (2 slightly, (3 somewhat, or (4 very much. All the results were recorded and statistical analyzed by SPSS software. Results: Out of 51, 29 patients were males while 22 were females, with ratio of 1.32:1. Female patients' mean age was 50.18 years while male patients' mean age was 52.71 years, with statistically nonsignificant difference between them. Functional rehabilitation was the main purpose of choosing dental implants in more than 90% of the subjects. Diameter of 3.75 mm was the shortest implants to be placed in the present study, whereas in terms of length, 8.5 mm was the shortest length of dental implant used in the present study. Tooth area in which maximum implants were placed in our study was 36 tooth region. Maximum implants were placed in Type II bone quality (n = 38. Implants installed in the mandible were clamped more efficiently than implants placed in the maxilla (P < 0.001. The difference of average STAI-State subscore before and after the surgery was statistically significant (P < 0.05; significant. Conclusion: Mandibular dental implants show more clamping (torque than maxillary

  5. Analysis of rock stress and rock stress measurements with application to Aespoe HRL

    International Nuclear Information System (INIS)

    Lundholm, Beatrice

    2000-11-01

    the opening where no influence from the openings can be expected. Since the magnitudes of the rock stresses differ between overcoring and hydraulic fracturing, some efforts have been made to find possible causes for this. The rock stresses when conducting overcoring gave higher values overall, which could be explained by high Poisson's ratios and a minor influence from the opening as the stress measurements might have been done in the disturbed zone. The high Poisson's ratio may depend on the stress-induced microcracks, which might be initiated during the overcoring of the cell, during the drilling of the pilot borehole, in which the cell is installed, and during biaxial testing. Statistical analysis showed that there is significant differences between the mean values of Poisson's ratio obtained from biaxial tests of cores containing the CSIRO HI-cell and the SSPB-cell. Poisson's ratio is about 0.34 for CSIRO HI-cell while the SSPB-cell gave a Poisson's ratio of 0.23. The analysis also showed that Young's modulus does not differ between the techniques. The modelling in FLAC was made to simulate the overcoring and biaxial testing. The result show that it is possible to obtain extensional strain in the core during overcoring if the major principal stress is perpendicular to the borehole axis. This may lead to microcracking occurring in the core causing high Poisson's ratio, which results in higher stresses. It can also be seen from the simulation of the biaxial testing that extensional strain is achieved even if the hollow core is not damaged during overcoring. The analyses using UDEC was made to study the effect of different properties of a discontinuity, such as the dip angle, Young's modulus, Poisson's ratio, density and the normal and shear stiffness. The analyses showed that an inclined discontinuity affects the stresses especially if sliding occurs. So, the dip angle does not solely, determine the amount of disturbance of the state of stress around a discontinuity

  6. Analysis of residual stresses in a long hollow cylinder

    International Nuclear Information System (INIS)

    Tokovyy, Yuriy V.; Ma, Chien-Ching

    2011-01-01

    This paper presents an analytical method for solving the axisymmetric stress problem for a long hollow cylinder subjected to locally-distributed residual (incompatible) strains. This method is based on direct integration of the equilibrium and compatibility equations, which thereby have been reduced to the set of two governing equations for two key functions with corresponding boundary and integral conditions. The governing equations were solved by making use of the Fourier integral transformation. Application of the method is illustrated with an analysis of the welding residual stresses in a butt-welded thick-walled pipe. - Highlights: → A solution to the axisymmetric stress problem for a hollow cylinder is constructed. → The cylinder is subjected to a field of locally-distributed residual strains. → The method is based on direct integration of the equilibrium equations. → An application of our solution to analysis of welding residual stresses is considered.

  7. Stress analysis and life prediction of gas turbine blade

    Science.gov (United States)

    Hsiung, H. C.; Dunn, A. J.; Woodling, D. R.; Loh, D. L.

    1988-01-01

    A stress analysis procedure is presented for a redesign of the Space Shuttle Main Engine high pressure fuel turbopump turbine blades. The analysis consists of the one-dimensional scoping analysis to support the design layout and the follow-on three-dimensional finite element analysis to confirm the blade design at operating loading conditions. Blade life is evaluated based on high-cycle fatigue and low-cycle fatigue.

  8. CANDIDATE GENE ANALYSIS IN ISRAELI SOLDIERS WITH STRESS FRACTURES

    Directory of Open Access Journals (Sweden)

    Ran Yanovich

    2012-03-01

    Full Text Available To investigate the association of polymorphisms within candidate genes which we hypothesized may contribute to stress fracture predisposition, a case-control, cross- sectional study design was employed. Genotyping 268 Single Nucleotide Polymorphisms- SNPs within 17 genes in 385 Israeli young male and female recruits (182 with and 203 without stress fractures. Twenty-five polymorphisms within 9 genes (NR3C1, ANKH, VDR, ROR2, CALCR, IL6, COL1A2, CBG, and LRP4 showed statistically significant differences (p < 0.05 in the distribution between stress fracture cases and non stress fracture controls. Seventeen genetic variants were associated with an increased stress fracture risk, and eight variants with a decreased stress fracture risk. None of the SNP associations remained significant after correcting for multiple comparisons (false discovery rate- FDR. Our findings suggest that genes may be involved in stress fracture pathogenesis. Specifically, the CALCR and the VDR genes are intriguing candidates. The putative involvement of these genes in stress fracture predisposition requires analysis of more cases and controls and sequencing the relevant genomic regions, in order to define the specific gene mutations

  9. Stresses, fatigue and fracture analysis in the tube sheets

    International Nuclear Information System (INIS)

    Billon, F.

    1986-05-01

    The purpose of the present work is to study the behaviour of the nuclear PWR steam generator tube sheet. But the methods developed in this field can easily be generalized in order to study tube sheets from any other type of heat exchangers. The aim of the stress analysis of these sheets is to verify their correct design, to quantify the risk of fatigue damage in the areas submitted to a high stress concentration and through the fracture mechanic, to make sure there is no risk of fast fracture resulting from initiated or pre-existing defects. This analysis necessarily relates to the calculation of stresses in all parts of the multidrilled area, mainly around the holes where they are concentrated. However the tube sheets are so complexe structures that their direct modelization cannot be envisaged within the context of the finite element method. We then must refer to the concept of equivalent medium in order to calculate the nominal stresses. Then using the stresses multiple fonctions appropriate to the net geometry, we can calculate the actual stresses concentrated around the holes. The method depends on the behaviour of the elementary volume which represents the behaviour of the multidrilled medium. This approach must allow to correctly take account of the ''thermal skin effect'', which is a phenomenon particular to the tube sheets with thermal loads. It must as well be generalized in order to analyse the irregular ligaments which affect the periodical stresses distribution and locally overconcentrate them [fr

  10. Oil prices and financial stress: A volatility spillover analysis

    International Nuclear Information System (INIS)

    Nazlioglu, Saban; Soytas, Ugur; Gupta, Rangan

    2015-01-01

    This paper examines whether there is a volatility transmission between oil prices and financial stress by means of the volatility spillover test. We employ WTI crude oil prices and Cleveland financial stress index for the period 1991–2014 and divide the sample into pre-crisis, in-crisis, and post-crisis periods due to the downward trend in oil price in 2008. The volatility model estimations indicate that oil prices and financial stress index are dominated by long-run volatility. The volatility spillover causality test supports evidence on risk transfer from oil prices to financial stress before the crisis and from financial stress to oil prices after the crisis. The impulse response analysis shows that the volatility transmission pattern has similar dynamics before and after the crisis and is characterized by higher and long-lived effects during the crisis. Our results have implications for both policy makers and investors, and for future work. -- Highlights: •Volatility spillover between oil prices and financial stress index is examined. •Analysis is conducted for sub-periods: pre-crisis, in-crisis, and post-crisis •Oil prices spill on financial stress before the crisis, but spillover reversed after the crisis. •Volatility transmission pattern has similar dynamics before and after the crisis. •Implications for investors and policy makers are discussed

  11. Drug-Induced Dental Caries: A Disproportionality Analysis Using Data from VigiBase.

    Science.gov (United States)

    de Campaigno, Emilie Patras; Kebir, Inès; Montastruc, Jean-Louis; Rueter, Manuela; Maret, Delphine; Lapeyre-Mestre, Maryse; Sallerin, Brigitte; Despas, Fabien

    2017-12-01

    Dental caries is defined as a pathological breakdown of the tooth. It is an infectious phenomenon involving a multifactorial aetiology. The impact of drugs on cariogenic risk has been poorly investigated. In this study, we identified drugs suspected to induce dental caries as adverse drug reactions (ADRs) and then studied a possible pathogenic mechanism for each drug that had a statistically significant disproportionality. We extracted individual case safety reports of dental caries associated with drugs from VigiBase ® (the World Health Organization global individual case safety report database). We calculated disproportionality for each drug with a reporting odds ratio (ROR) and 99% confidence interval. We analysed the pharmacodynamics of each drug that had a statistically significant disproportionality. In VigiBase ® , 5229 safety reports for dental caries concerning 733 drugs were identified. Among these drugs, 88 had a significant ROR, and for 65 of them (73.9%), no information about dental caries was found in the summaries of the product characteristics, the Micromedex ® DRUGDEX, or the Martindale databases. Regarding the pharmacological classes of drugs involved in dental caries, we identified bisphosphonates, atropinic drugs, antidepressants, corticoids, immunomodulating drugs, antipsychotics, antiepileptics, opioids and β 2 -adrenoreceptor agonist drugs. Regarding possible pathogenic mechanisms for these drugs, we identified changes in salivary flow/composition for 54 drugs (61.4%), bone metabolism changes for 31 drugs (35.2%), hyperglycaemia for 32 drugs (36.4%) and/or immunosuppression for 23 drugs (26.1%). For nine drugs (10.2%), the mechanism was unclear. We identified 88 drugs with a significant positive disproportionality for dental caries. Special attention has to be paid to bisphosphonates, atropinic drugs, immunosuppressants and drugs causing hyperglycaemia.

  12. Dental negligence.

    Science.gov (United States)

    Tay, C S

    2000-02-01

    Medical and dental errors and negligence are again in the spotlight in recent news report. Dead because of doctor's bad handwriting Prescribing drug overdoses Germ-infested soap pumps--infections in hospitals This articles explains dental negligence including dental duty of care and the standard of care expected of dentists in relation to the Bolam principle.

  13. An Integrated Analysis of Changes in Water Stress in Europe

    DEFF Research Database (Denmark)

    Henrichs, T.; Lehner, B.; Alcamo, J.

    2002-01-01

    Future changes in water availability with climate change and changes in water use due to socio-economic development are to occur in parallel. In an integrated analysis we bring together these aspects of global change in a consistent manner, and analyse the water stress situation in Europe. We find...... that today high water stress exists in one-fifth of European river basin area. Under a scenario projection, increases in water use throughout Eastern Europe are accompanied by decreases in water availability in most of Southern Europe--combining these trends leads to a marked increase in water stress...

  14. Numerical analysis of interacting cracks in biaxial stress field

    International Nuclear Information System (INIS)

    Kovac, M.; Cizelj, L.

    1999-01-01

    The stress corrosion cracks as seen for example in PWR steam generator tubing made of Inconel 600 usually produce highly irregular kinked and branched crack patterns. Crack initialization and propagation depends on stress state underlying the crack pattern. Numerical analysis (such as finite element method) of interacting kinked and branched cracks can provide accurate solutions. This paper discusses the use of general-purpose finite element code ABAQUS for evaluating stress fields at crack tips of interacting complex cracks. The results obtained showed reasonable agreement with the reference solutions and confirmed use of finite elements in such class of problems.(author)

  15. Stress analysis of the tokamak engineering test breeder blanket

    International Nuclear Information System (INIS)

    Huang Zhongqi

    1992-01-01

    The design features of the hybrid reactor blanket and main parameters are presented. The stress analysis is performed by using computer codes SAP5p and SAP6 with the three kinds of blanket module loadings, i.e, the pressure of coolant, the blanket weight and the thermal loading. Numerical calculation results indicate that the stresses of the blanket are smaller than the allowable ones of the material, the blanket design is therefore reasonable

  16. Temperature and thermal stress analysis of a switching tube anode

    International Nuclear Information System (INIS)

    Sutton, S.B.

    1979-01-01

    In the design of high power density switching tubes which are subjected to cyclic thermal loads, the temperature induced stresses must be minimized in order to maximize the life expectancy of the tube. Following are details of an analysis performed for the Magnetic Fusion Program at the Lawrence Livermore Laboratory on a proposed tube. The tube configuration is given. The problem was simplified to one-dimensional approximations for both the thermal and stress analyses. The underlying assumptions and their implications are discussed

  17. Clinical evaluation of a dental color analysis system: the Crystaleye Spectrophotometer®.

    Science.gov (United States)

    Odaira, Chikayuki; Itoh, Sozo; Ishibashi, Kanji

    2011-10-01

    To evaluate the clinical performance of the Crystaleye Spectrophotometer(®), a dental color analysis system. Three color-measuring devices (Crystaleye Spectrophotometer(®), CAS-ID1, MSC-2000) were tested and the differences in color measurements among them were evaluated using Scheffe's F-test. Color measurements with the Crystaleye Spectrophotometer(®) were repeated 10 times by the same operator. The color difference (ΔE) between the first and tenth measurements was calculated. The Crystaleye Spectrophotometer(®) was used to measure the color of the maxillary left central incisor under two conditions (light and dark) and the effect of exterior lighting was analyzed to assess the accuracy of measurements. Furthermore, five different operators performed color measurements, and ΔE among the three devices was calculated. The ΔE between the target tooth and the crown of a single maxillary central incisor crown fabricated using data from the Crystaleye Spectrophotmeter(®) was calculated. Color differences between prebleaching and postbleaching were also analyzed with the Crystaleye Spectrophotometer(®) using the parameters ΔE, ΔL*, Δa*, and Δb*. The data from the three spectrophotometers were not significantly different. The ΔE during repeated color measurements by the same operator was 0.6. The ΔE between light and dark conditions was 0.9. The data from the five operators were not significantly different. The mean ΔE value between the target tooth and the fabricated crown was 1.2 ± 0.4, and the mean ΔE value between prebleaching and postbleaching was 3.7 ± 1.0. The Crystaleye Spectrophotometer(®) is an easy-to-use color analysis system producing accurate color measurements under clinical conditions. Copyright © 2011 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  18. Prophylactic antibiotic regimen and dental implant failure: a meta-analysis.

    Science.gov (United States)

    Chrcanovic, B R; Albrektsson, T; Wennerberg, A

    2014-12-01

    The aim of this meta-analysis was to investigate whether there are any positive effects of prophylactic antibiotic regimen on implant failure rates and post-operative infection when performing dental implant treatment in healthy individuals. An electronic search without time or language restrictions was undertaken in March 2014. Eligibility criteria included clinical human studies, either randomised or not. The search strategy resulted in 14 publications. The I(2) statistic was used to express the percentage of the total variation across studies due to heterogeneity. The inverse variance method was used with a fixed- or random-effects model, depending on the heterogeneity. The estimates of relative effect were expressed in risk ratio (RR) with 95% confidence interval. Six studies were judged to be at high risk of bias, whereas one study was considered at moderate risk, and six studies were considered at low risk of bias. The test for overall effect showed that the difference between the procedures (use versus non-use of antibiotics) significantly affected the implant failure rates (P = 0.0002), with a RR of 0.55 (95% CI 0.41-0.75). The number needed to treat (NNT) to prevent one patient having an implant failure was 50 (95% CI 33-100). There were no apparent significant effects of prophylactic antibiotics on the occurrence of post-operative infections in healthy patients receiving implants (P = 0.520). A sensitivity analysis did not reveal difference when studies judged as having high risk of bias were not considered. The results have to be interpreted with caution due to the presence of several confounding factors in the included studies. © 2014 John Wiley & Sons Ltd.

  19. Comparing the influence of crestal cortical bone and sinus floor cortical bone in posterior maxilla bi-cortical dental implantation: a three-dimensional finite element analysis.

    Science.gov (United States)

    Yan, Xu; Zhang, Xinwen; Chi, Weichao; Ai, Hongjun; Wu, Lin

    2015-05-01

    This study aimed to compare the influence of alveolar ridge cortical bone and sinus floor cortical bone in sinus areabi-cortical dental implantation by means of 3D finite element analysis. Three-dimensional finite element (FE) models in a posterior maxillary region with sinus membrane and the same height of alveolar ridge of 10 mm were generated according to the anatomical data of the sinus area. They were either with fixed thickness of crestal cortical bone and variable thickness of sinus floor cortical bone or vice versa. Ten models were assumed to be under immediate loading or conventional loading. The standard implant model based on the Nobel Biocare implant system was created via computer-aided design software. All materials were assumed to be isotropic and linearly elastic. An inclined force of 129 N was applied. Von Mises stress mainly concentrated on the surface of crestal cortical bone around the implant neck. For all the models, both the axial and buccolingual resonance frequencies of conventional loading were higher than those of immediate loading; however, the difference is less than 5%. The results showed that bi-cortical implant in sinus area increased the stability of the implant, especially for immediately loading implantation. The thickness of both crestal cortical bone and sinus floor cortical bone influenced implant micromotion and stress distribution; however, crestal cortical bone may be more important than sinus floor cortical bone.

  20. Trend Analysis of Studies on Water Fluoridation Related to Dental Caries in PubMed.

    Science.gov (United States)

    Oh, Hyo-Jung; Choi, Hyeon-Mi; Kim, Chonghyuck; Jeon, Jae-Gyu

    2018-04-04

    Water fluoridation has been cited as one of the top 10 public health achievements of the 20th century. Herein, we analyzed water fluoridation articles related to dental caries published in PubMed between 1950 and 2016 using informetrics and linguistic methods to investigate trends in the studies. To this aim, queries such as "dental caries and (water fluoridation or fluoridated water)," "dental caries and (fluoride or fluoridation)," and "dental caries" were submitted to PubMed to retrieve information about articles on water fluoridation within the area of dental caries and fluoride - their titles, abstracts, publication dates, author affiliations, and publication journals. This article information was then collected by an automatic web crawler and examined through informetrics and linguistic analyses. It was found that the number of articles concerned with water fluoridation and dental caries was 3,381 and declined over time after 1970. The articles were published by 750 journals - most notably, Community Dentistry and Oral Epidemiology and Caries Research. With regard to the geographic distribution of the authors, Europe and North America, especially the USA and UK, accounted for 59.9% of the articles published during the years 1987 to 2015, though there was a sharp increase in the number of authors in Oceania and Asia in recent years. In the titles and abstracts of the articles, "community" and "fluorosis" were mentioned more frequently than the other key terms selected in this study, regardless of the period examined. Our findings may allow one to assess how the research on water fluoridation has evolved over the past several decades. © 2018 S. Karger AG, Basel.

  1. Dental anomalies in 14 patients with IP: clinical and radiological analysis and review.

    Science.gov (United States)

    Santa-Maria, Fernanda D; Mariath, Luiza Monteavaro; Poziomczyk, Cláudia S; Maahs, Marcia A P; Rosa, Rafael F M; Zen, Paulo R G; Schüller-Faccini, Lavínia; Kiszewski, Ana Elisa

    2017-06-01

    Current knowledge on dental anomalies in patients with incontinentia pigmenti (IP) has been obtained by examining case reports; however, an overall characterization of such alterations remains lacking. The objective of this study was to determine the frequency, type and location of dental alterations in IP using a case series. Fourteen patients (9 children and 5 adults) with a clinical diagnosis of IP who presented dental anomalies were included in this study. All patients were administered a clinical questionnaire, dental examination and radiological investigation. In the present case series, agenesis of primary dentition was present in 60 % of patients and agenesis of permanent tooth was present in 92.8 % of patients. Most cases were missing at least 6 teeth. Second molar agenesis was present in 13 patients (92.8 %). Anomalies in dental crowns occurred in 71.4 % of cases, and the central incisor was most frequently affected. Two adult patients still had primary teeth. Malocclusion was found in 10 patients (71.4 %). High-arched palate was observed in 7 (50 %) patients. Patients with IP present alterations in both primary and permanent dentition. Because the agenesis of permanent teeth is more common, primary teeth are not always replaced. In addition, the durability of primary dentition appears to be greater in IP. This study shows that patients with IP experience significant loss of teeth, especially in permanent dentition, and have an increased risk of high-arched palate compared to the general population. Prophylactic care of primary teeth in IP is relevant for improving functional and aesthetic outcomes until dental prostheses are implanted.

  2. Lessons from a pilot project in cognitive task analysis: the potential role of intermediates in preclinical teaching in dental education.

    Science.gov (United States)

    Walker, Judith; von Bergmann, HsingChi

    2015-03-01

    The purpose of this study was to explore the use of cognitive task analysis to inform the teaching of psychomotor skills and cognitive strategies in clinical tasks in dental education. Methods used were observing and videotaping an expert at one dental school thinking aloud while performing a specific preclinical task (in a simulated environment), interviewing the expert to probe deeper into his thinking processes, and applying the same procedures to analyze the performance of three second-year dental students who had recently learned the analyzed task and who represented a spectrum of their cohort's ability to undertake the procedure. The investigators sought to understand how experts (clinical educators) and intermediates (trained students) overlapped and differed at points in the procedure that represented the highest cognitive load, known as "critical incidents." Findings from this study and previous research identified possible limitations of current clinical teaching as a result of expert blind spots. These findings coupled with the growing evidence of the effectiveness of peer teaching suggest the potential role of intermediates in helping novices learn preclinical dentistry tasks.

  3. A three-dimensional analysis of skeletal and dental characteristics in skeletal class III patients with facial asymmetry.

    Science.gov (United States)

    Yu, Jinfeng; Hu, Yun; Huang, Mingna; Chen, Jun; Ding, Xiaoqian; Zheng, Leilei

    2018-03-15

    To evaluate the skeletal and dental characteristics in skeletal class III patients with facial asymmetry and to analyse the relationships among various parts of the stomatognathic system to provide a theoretical basis for clinical practice. Asymmetric cone-beam computed tomography data acquired from 56 patients were evaluated using Mimics 10.0 and 3-Matic software. Skeletal and dental measurements were performed to assess the three-dimensional differences between two sides. Pearson correlation analysis was used to determine the correlations among measurements. Linear measurements, such as ramal height, mandible body length, ramal height above the sigmoid notch (RHASN), maxillary height, condylar height, buccal and total cancellous bone thickness, and measurements of condylar size, were significantly larger on the nondeviated side than on the deviated side (P orthodontic camouflage has limitations and potential risks. A combination of orthodontics and orthognathic surgery may be the advisable choice in patients with a menton deviation greater than 4 mm. An important association between vertical skeletal disharmony and dental compensation was also observed.

  4. Transcriptome Analysis of Sunflower Genotypes with Contrasting Oxidative Stress Tolerance Reveals Individual- and Combined- Biotic and Abiotic Stress Tolerance Mechanisms.

    Directory of Open Access Journals (Sweden)

    Vemanna S Ramu

    Full Text Available In nature plants are often simultaneously challenged by different biotic and abiotic stresses. Although the mechanisms underlying plant responses against single stress have been studied considerably, plant tolerance mechanisms under combined stress is not understood. Also, the mechanism used to combat independently and sequentially occurring many number of biotic and abiotic stresses has also not systematically studied. From this context, in this study, we attempted to explore the shared response of sunflower plants to many independent stresses by using meta-analysis of publically available transcriptome data and transcript profiling by quantitative PCR. Further, we have also analyzed the possible role of the genes so identified in contributing to combined stress tolerance. Meta-analysis of transcriptomic data from many abiotic and biotic stresses indicated the common representation of oxidative stress responsive genes. Further, menadione-mediated oxidative stress in sunflower seedlings showed similar pattern of changes in the oxidative stress related genes. Based on this a large scale screening of 55 sunflower genotypes was performed under menadione stress and those contrasting in oxidative stress tolerance were identified. Further to confirm the role of genes identified in individual and combined stress tolerance the contrasting genotypes were individually and simultaneously challenged with few abiotic and biotic stresses. The tolerant hybrid showed reduced levels of stress damage both under combined stress and few independent stresses. Transcript profiling of the genes identified from meta-analysis in the tolerant hybrid also indicated that the selected genes were up-regulated under individual and combined stresses. Our results indicate that menadione-based screening can identify genotypes not only tolerant to multiple number of individual biotic and abiotic stresses, but also the combined stresses.

  5. Stress analysis of longwall top coal caving

    Energy Technology Data Exchange (ETDEWEB)

    Alehossein, H.; Poulsen, B.A. [CSIRO Exploration & Mining, Brisbane, Qld. (Australia)

    2010-01-15

    Longwall top coal caving (LTCC) is a relatively new method of mining thick coal seams that is currently achieving high productivity and efficiency. The technique is similar to traditional longwall mining in that a cutting head slices coal from the lower section of the coal seam onto a conveyor belt installed in front of the hydraulic support near the cutting face. In modern LTCC an additional rear conveyor belt is located behind the support, to which the flow of the caved coal from the upper part of the seam can be controlled by a moveable flipper attached to the canopy of the support. The mining method relies on the fracturing of the top coal by the front abutment pressure to achieve satisfactory caving into the rear conveyor. This paper develops a yield and caveability criterion based on in situ conditions in the top coal in advance of the mining face (yield) and behind the supports (caveability). Yielding and caving effects are combined into one single number called caving number (CN), which is the multiplication result of caving factor (CF) and yield factor (YF). Analytical derivations are based on in situ stress conditions, Mohr-Coulomb and/or Hoek-Brown rock failure criteria and an on-associated elastoplastic strain softening material behaviour. The yield and caveability criteria are in agreement with results from both numerical studies and mine data. The caving number is normalised to mining conditions of a reference Chinese mine (LMX mine) and is used to assess LTCC performance at fourteen other Chinese working longwalls that have had varying success with the LTCC technology. As a predictive model, results of this analytical/numerical study are useful to assess the potential success of caving in new LTCC operations and in different mining conditions.

  6. Digitization of simulated clinical dental impressions: virtual three-dimensional analysis of exactness.

    Science.gov (United States)

    Persson, Anna S K; Odén, Agneta; Andersson, Matts; Sandborgh-Englund, Gunilla

    2009-07-01

    To compare the exactness of simulated clinical impressions and stone replicas of crown preparations, using digitization and virtual three-dimensional analysis. Three master dies (mandibular incisor, canine and molar) were prepared for full crowns, mounted in full dental arches in a plane line articulator. Eight impressions were taken using an experimental monophase vinyl polysiloxane-based material. Stone replicas were poured in type IV stone (Vel-Mix Stone; Kerr). The master dies and the stone replicas were digitized in a touch-probe scanner (Procera) Forte; Nobel Biocare AB) and the impressions in a laser scanner (D250, 3Shape A/S), to create virtual models. The resulting point-clouds from the digitization of the master dies were used as CAD-Reference-Models (CRM). Discrepancies between the points in the pointclouds and the corresponding CRM were measured by a matching-software (CopyCAD 6.504 SP2; Delcam Plc). The distribution of the discrepancies was analyzed and depicted on color-difference maps. The discrepancies of the digitized impressions and the stone replicas compared to the CRM were of similar size with a mean+/-SD within 40microm, with the exception of two of the digitized molar impressions. The precision of the digitized impressions and stone replicas did not differ significantly (F=4.2; p=0.053). However, the shape affected the digitization (F=5.4; p=0.013) and the interaction effect of shape and digitization source (impression or stone replica) was pronounced (F=28; pimpressions varied with shape. Both impressions and stone replicas can be digitized repeatedly with a high reliability.

  7. Neurosensory analysis of tooth sensitivity during at-home dental bleaching: a randomized clinical trial

    Science.gov (United States)

    Briso, André Luiz Fraga; Rahal, Vanessa; de Azevedo, Fernanda Almeida; Gallinari, Marjorie de Oliveira; Gonçalves, Rafael Simões; dos Santos, Paulo Henrique; Cintra, Luciano Tavares Angelo

    2018-01-01

    Abstract Objective The objective of this study was to evaluate dental sensitivity using visual analogue scale, a Computerized Visual Analogue Scale (CoVAS) and a neurosensory analyzer (TSA II) during at-home bleaching with 10% carbamide peroxide, with and without potassium oxalate. Materials and Methods Power Bleaching 10% containing potassium oxalate was used on one maxillary hemi-arch of the 25 volunteers, and Opalescence 10% was used on the opposite hemi-arch. Bleaching agents were used daily for 3 weeks. Analysis was performed before treatment, 24 hours later, 7, 14, and 21 days after the start of the treatment, and 7 days after its conclusion. The spontaneous tooth sensitivity was evaluated using the visual analogue scale and the sensitivity caused by a continuous 0°C stimulus was analyzed using CoVAS. The cold sensation threshold was also analyzed using the TSA II. The temperatures obtained were statistically analyzed using ANOVA and Tukey's test (α=5%). Results The data obtained with the other methods were also analyzed. 24 hours, 7 and 14 days before the beginning of the treatment, over 20% of the teeth presented spontaneous sensitivity, the normal condition was restored after the end of the treatment. Regarding the cold sensation temperatures, both products sensitized the teeth (p0.05). In addition, when they were compared using CoVAS, Power Bleaching caused the highest levels of sensitivity in all study periods, with the exception of the 14th day of treatment. Conclusion We concluded that the bleaching treatment sensitized the teeth and the product with potassium oxalate was not able to modulate tooth sensitivity. PMID:29742258

  8. Dental Blogs, Podcasts, and Associated Social Media: Descriptive Mapping and Analysis.

    Science.gov (United States)

    Melkers, Julia; Hicks, Diana; Rosenblum, Simone; Isett, Kimberley R; Elliott, Jacqueline

    2017-07-26

    Studies of social media in both medicine and dentistry have largely focused on the value of social media for marketing to and communicating with patients and for clinical education. There is limited evidence of how dental clinicians contribute to and use social media to disseminate and access information relevant to clinical care. The purpose of this study was to inventory and assess the entry, growth, sources, and content of clinically relevant social media in dentistry. We developed an inventory of blogs, podcasts, videos, and associated social media disseminating clinical information to dentists. We assessed hosts' media activity in terms of their combinations of modalities, entry and exit dates, frequency of posting, types of content posted, and size of audience. Our study showed that clinically relevant information is posted by dentists and hygienists on social media. Clinically relevant information was provided in 89 blogs and podcasts, and topic analysis showed motives for blogging by host type: 55% (49 hosts) were practicing dentists or hygienists, followed by consultants (27 hosts, 30%), media including publishers and discussion board hosts (8 hosts, 9%), and professional organizations and corporations. We demonstrated the participation of and potential for practicing dentists and hygienists to use social media to share clinical and other information with practicing colleagues. There is a clear audience for these social media sites, suggesting a changing mode of information diffusion in dentistry. This study was a first effort to fill the gap in understanding the nature and potential role of social media in clinical dentistry. ©Julia Melkers, Diana Hicks, Simone Rosenblum, Kimberley R Isett, Jacqueline Elliott. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 26.07.2017.

  9. Stress analysis program system for nuclear vessel: STANSAS

    International Nuclear Information System (INIS)

    Okamoto, Asao; Michikami, Shinsuke

    1979-01-01

    IHI has developed a computer system of stress analysis and evaluation for nuclear vessels: STANSAS (STress ANalysis System for Axi-symmetric Structure). The system consists of more than twenty independent programs divided into the following six parts. 1. Programs for opening design by code rule. 2. Calculation model generating programs. 3. Load defining programs. 4. Structural analysis programs. 5. Load data/calculation results plotting programs. 6. Stress evaluation programs. Each program is connected with its pre- or post-processor through three data-bases which enable automatic data transfer. The user can make his choice of structural analysis programs in accordance with the problem to be solved. The interface to STANSAS can be easily installed in generalized structural analysis programs such as NASTRAN and MARC. For almost all tables and figures in the stress report, STANSAS has the function to print or plot out. The complicated procedures of ''Design by Analysis'' for pressure vessels have been well standardized by STANSAS. The system will give a high degree of efficiency and confidence to the design work. (author)

  10. Analysis of health services cost at the dental clinic of the San Marcos University.

    OpenAIRE

    Madrid Chumacero, Marco Tulio; Echeandía Arellano, Juana V.

    2014-01-01

    The objectives of this study were: To establish the unitary services cost in Dentistry, To describe simplest way to determine the costs structure approximated for each dental service offered at the clinic. They it was compared with the welfare rates at the dental clinic of the UNMSM, the results were the following ones: 1. Diagnosis: in the four cost activities is higher compared with the official rates, demonstrating "minimum utilities" that goes up from 0,21 to s. 15.96. 2. Radiology: in th...

  11. Preoperative CT analysis of the mandible and maxilla for permanent dental prosthetic implantation

    International Nuclear Information System (INIS)

    Rothman, S.L.G.; Rhodes, M.L.; Schwarz, M.; Chafetz, N.I.

    1987-01-01

    The Branemark technique for permanently implanting dental prostheses is becoming universally accepted. The surgeon requires detailed knowledge of the cross-sectional anatomy of the alveolar ridges and inferior alveolar nerve for safe placement of the titanium fixtures. Axial CT scans of the mandible and maxilla, with oblique and panoramic CT reformations, were obtained in more than 100 patients. This report describes the anatomic variations in the maxilla and mandible as they relate to dental implantation surgery. The authors demonstrate the utility of this technique in preoperative surgical planning and postoperative evaluation

  12. Stress Analysis for the Critical Metal Structure of Bridge Crane

    Science.gov (United States)

    Ling, Zhangwei; Wang, Min; Xia, Junfang; Wang, Songhua; Guo, Xiaolian

    2018-01-01

    Based on the type of connection between the main girder and end beam of electrical single beam crane, the finite element analysis model of a full portal crane was established. The stress distribution of the critical structure under different loading conditions was analyzed. The results shown that the maximum Mises stress and deflection of the main girder were within the allowable range. And the connecting location between end beam web and main girder had higher stress than other region, especially at the lower edge and upper edge of the end beam web and the area near the bolt hole of upper wing panel. Therefore it is important to inspect the connection status, the stress condition and the crack situation nearing connection location during the regular inspection process to ensure the safety of the connection between the main girder and end beam.

  13. Non-linear elastic thermal stress analysis with phase changes

    International Nuclear Information System (INIS)

    Amada, S.; Yang, W.H.

    1978-01-01

    The non-linear elastic, thermal stress analysis with temperature induced phase changes in the materials is presented. An infinite plate (or body) with a circular hole (or tunnel) is subjected to a thermal loading on its inner surface. The peak temperature around the hole reaches beyond the melting point of the material. The non-linear diffusion equation is solved numerically using the finite difference method. The material properties change rapidly at temperatures where the change of crystal structures and solid-liquid transition occur. The elastic stresses induced by the transient non-homogeneous temperature distribution are calculated. The stresses change remarkably when the phase changes occur and there are residual stresses remaining in the plate after one cycle of thermal loading. (Auth.)

  14. Thermal stratification and fatigue stress analysis for pressurizer surge line

    International Nuclear Information System (INIS)

    Yu Xiaofei; Zhang Yixiong

    2011-01-01

    Thermal stratification of pressurizer surge line induced by the inside fluid results in the global bending moments, local thermal stresses, unexpected displacements and support loadings of the pipe system. In order to avoid a costly three-dimensional computation, a combined 1D/2D technique has been developed and implemented to analyze the thermal stratification and fatigue stress of pressurize surge line of QINSHAN Phase II Extension Nuclear Power Project in this paper, using the computer codes SYSTUS and ROCOCO. According to the mechanical analysis results of stratification, the maximum stress and cumulative usage factor are obtained. The results indicate that the stress and fatigue intensity considering thermal stratification satisfies RCC-M criterion. (authors)

  15. Blade dynamic stress analysis of rotating bladed disks

    Directory of Open Access Journals (Sweden)

    Kellner J.

    2007-10-01

    Full Text Available The paper deals with mathematical modelling of steady forced bladed disk vibrations and with dynamic stress calculation of the blades. The blades are considered as 1D kontinuum elastic coupled with three-dimensional elastic disk centrally clamped into rotor rotating with constant angular speed. The steady forced vibrations are generated by the aerodynamic forces acting along the blade length. By using modal synthesis method the mathematical model of the rotating bladed disk is condensed to calculate steady vibrations. Dynamic stress analysis of the blades is based on calculation of the time dependent reduced stress in blade cross-sections by using Hubert-Misses-Hencky stress hypothesis. The presented method is applied to real turbomachinery rotor with blades connected on the top with shroud.

  16. Stress analysis of aspherical coated particle with inner pressure

    Energy Technology Data Exchange (ETDEWEB)

    Liu Bing, E-mail: bingliu@tsinghua.edu.cn [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084 (China); Yang Lin; Liang Tongxiang; Tang Chunhe [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084 (China)

    2012-10-15

    Coated particles used in HTR fuel element sustain the inner pressure during irradiation as a pressure vessel. In actually the coated particle is not real spherical but with some asphericity, the stress distribution in the vessel is not uniform, coated layer in aspherical particle sustain more additional stress due to the asphericity. In this paper, the geometric shape distribution is summarized based on actual coated particle statistic. A mechanical analysis model is proposed for SiC layer by geometric combinations, and stress distribution of coated particle with a flat is calculated. The results show that the local maximum stress of aspherical particle increased two times than that of ideal spherical coated particle, which increase the failure probability under irradiation and high temperature.

  17. Image decomposition as a tool for validating stress analysis models

    Directory of Open Access Journals (Sweden)

    Mottershead J.

    2010-06-01

    Full Text Available It is good practice to validate analytical and numerical models used in stress analysis for engineering design by comparison with measurements obtained from real components either in-service or in the laboratory. In reality, this critical step is often neglected or reduced to placing a single strain gage at the predicted hot-spot of stress. Modern techniques of optical analysis allow full-field maps of displacement, strain and, or stress to be obtained from real components with relative ease and at modest cost. However, validations continued to be performed only at predicted and, or observed hot-spots and most of the wealth of data is ignored. It is proposed that image decomposition methods, commonly employed in techniques such as fingerprinting and iris recognition, can be employed to validate stress analysis models by comparing all of the key features in the data from the experiment and the model. Image decomposition techniques such as Zernike moments and Fourier transforms have been used to decompose full-field distributions for strain generated from optical techniques such as digital image correlation and thermoelastic stress analysis as well as from analytical and numerical models by treating the strain distributions as images. The result of the decomposition is 101 to 102 image descriptors instead of the 105 or 106 pixels in the original data. As a consequence, it is relatively easy to make a statistical comparison of the image descriptors from the experiment and from the analytical/numerical model and to provide a quantitative assessment of the stress analysis.

  18. Development and Validation of a Constitutive Model for Dental Composites during the Curing Process

    Science.gov (United States)

    Wickham Kolstad, Lauren

    Debonding is a critical failure of a dental composites used for dental restorations. Debonding of dental composites can be determined by comparing the shrinkage stress of to the debonding strength of the adhesive that bonds it to the tooth surface. It is difficult to measure shrinkage stress experimentally. In this study, finite element analysis is used to predict the stress in the composite during cure. A new constitutive law is presented that will allow composite developers to evaluate composite shrinkage stress at early stages in the material development. Shrinkage stress and shrinkage strain experimental data were gathered for three dental resins, Z250, Z350, and P90. Experimental data were used to develop a constitutive model for the Young's modulus as a function of time of the dental composite during cure. A Maxwell model, spring and dashpot in series, was used to simulate the composite. The compliance of the shrinkage stress device was also taken into account by including a spring in series with the Maxwell model. A coefficient of thermal expansion was also determined for internal loading of the composite by dividing shrinkage strain by time. Three FEA models are presented. A spring-disk model validates that the constitutive law is self-consistent. A quarter cuspal deflection model uses separate experimental data to verify that the constitutive law is valid. Finally, an axisymmetric tooth model is used to predict interfacial stresses in the composite. These stresses are compared to the debonding strength to check if the composite debonds. The new constitutive model accurately predicted cuspal deflection data. Predictions for interfacial bond stress in the tooth model compare favorably with debonding characteristics observed in practice for dental resins.

  19. Is the Level of Nitric Oxide in the Dental Follicular Tissues of Impacted Third Molars With a History of Recurrent Pericoronitis a True Marker of Oxidative Stress?

    Science.gov (United States)

    Hendek, Meltem Karsiyaka; Şenses, Fatma; Kisa, Üçler; Aksoy, Nurkan; Tekin, Umut

    2017-10-01

    Nitric oxide (NO) is an indicator of oxidative stress in several tissues. Its role in dental follicular (DF) tissues of impacted third molars with a history of recurrent pericoronitis is not well elucidated. The present study compared NO levels between inflamed and noninflamed DF tissues of impacted third molars with a history of recurrent pericoronitis. A cross-sectional study was designed. The study sample included inflamed DF tissues (test group) with certain local inflammatory symptoms, such as pain, tenderness, swelling, and erythema and noninflamed DF tissues (control group) without local inflammatory symptoms of impacted mandibular third molars. Each patient contributed only 1 specimen to the samples. All tissues samples were biochemically investigated for NO levels as an indicator of oxidative stress. The primary predictor variable was inflammatory status; secondary predictor variables were age and gender. The primary outcome variable was NO level. Descriptive and comparative analyses were conducted. The test group consisted of 57 patients (28 men, 29 women; mean age, 23.28 ± 5.16 yr) and the control group consisted of 57 patients (30 men, 27 women; mean age, 23.02 ± 5.42 yr). No relevant intergroup differences were noted for demographic findings such as age and gender. NO levels were significantly higher in inflamed DF tissues of impacted third molars than in noninflamed DF tissues (P stress and the necessity to remove impacted mandibular third molars with a history of recurrent pericoronitis. Copyright © 2017 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

  20. Análisis del comportamiento mecánico de una aleación Ni-Cr-Mo para pilares dentales/Analysis of Mechanical Behavior of Ni-Cr-Mo alloy for Dental Abutments

    Directory of Open Access Journals (Sweden)

    Luis Alberto Laguado Villamizar

    2012-12-01

    Full Text Available El presente estudio caracteriza una aleación aplicable al diseño de pilares para implantes dentales. Se propone un material biocompatible y de alta resistencia mecánica como alternativa a las aleaciones de Titanio, disminuyendo los costos de materia prima y procesamiento. Se realizan pruebas mecánicas de tracción y de compresión a la aleación de Ni-Cr-Mo, posteriormente se realiza modelado 3D y simulación de sus propiedades mecánicas por medio de análisis de elementos finitos. Como resultado se obtiene que el material disminuye su resistencia mecánica después del proceso de fundición empleado. El modelo de simulación es válido para análisis de resistencia en pilares dentales.This study presents the characterization of a dental implant alloy for abutments. It proposes a biocompatible material and high mechanical resistance as an alternative to Titanium alloys, lowering costs of raw materials and processing. Mechanical testing of the Ni-Cr-Mo alloy and subsequently perform simulations of its mechanical properties by means of finite element analysis. As a result is obtained that the material reduces its mechanical strength after the casting for electric induction molding process. The simulation model is valid to make analysis of resistance to this type of dental devices.

  1. Experimental stress analysis for determination of residual stresses and integrity monitoring of components and systems

    International Nuclear Information System (INIS)

    1993-01-01

    For an analysis of the safety-related significance of residual stresses, mechanical, magnetic as well as ultrasonic and diffraction methods can be applied as testing methods. The results of an interlaboratory test concerning the experimental determination of residual stresses in a railway track are included. Further, questions are analyzed concerning the in-service inspections of components and systems with regard to their operational safety and life. Measurement methods are explained by examples from power plant engineering, nuclear power plant engineering, construction and traffic engineering as well as aeronautics. (DG) [de

  2. Community analysis of dental plaque and endotracheal tube biofilms from mechanically ventilated patients.

    Science.gov (United States)

    Marino, Poala J; Wise, Matt P; Smith, Ann; Marchesi, Julian R; Riggio, Marcello P; Lewis, Michael A O; Williams, David W

    2017-06-01

    Mechanically ventilated patients are at risk for developing ventilator-associated pneumonia, and it has been reported that dental plaque provides a reservoir of respiratory pathogens that may aspirate to the lungs and endotracheal tube (ETT) biofilms. For the first time, metataxonomics was used to simultaneously characterize the microbiome of dental plaque, ETTs, and non-directed bronchial lavages (NBLs) in mechanically ventilated patients to determine similarities in respective microbial communities and therefore likely associations. Bacterial 16S rRNA gene sequences from 34 samples of dental plaque, NBLs, and ETTs from 12 adult mechanically ventilated patients were analyzed. No significant differences in the microbial communities of these samples were evident. Detected bacteria were primarily oral species (e.g., Fusobacterium nucleatum, Streptococcus salivarius, Prevotella melaninogenica) with respiratory pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcuspneumoniae, and Haemophilus influenzae) also in high abundance. The high similarity between the microbiomes of dental plaque, NBLs, and ETTs suggests that the oral cavity is indeed an important site involved in microbial aspiration to the lower airway and ETT. As such, maintenance of good oral hygiene is likely to be highly important in limiting aspiration of bacteria in this vulnerable patient group. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Immediate placement of dental implants in the esthetic zone : a systematic review and pooled analysis

    NARCIS (Netherlands)

    Slagter, Kirsten W; den Hartog, Laurens; Bakker, Nicolaas A; Vissink, Arjan; Meijer, Henny J A; Raghoebar, Gerry M

    Background: Research interest on immediate placement of dental implants has shifted from implant survival toward optimal preservation of soft and hard tissues. The aim of this study is to systematically assess the condition of implant survival, peri-implant hard and soft tissue changes, esthetic

  4. Analysis of the causes of dental implant fracture: A retrospective clinical study.

    Science.gov (United States)

    Stoichkov, Biser; Kirov, Dimitar

    2018-01-01

    Fracture of osseointegrated dental implants is the most severe mechanical complication. The aim of the present study was to analyze possible causative factors for implant body fracture. One hundred and one patients with 218 fitted implants and a follow-up period of 3 to 10 years were studied. Factors associated with biomechanical and physiologic overloading such as parafunctional activity (eg, bruxism), occlusion, and cantilevers, and factors related to the planning of the dental prosthesis, available bone volume, implant area, implant diameter, number of implants, and their inclination were tracked. The impact of their effect was analyzed using the Bonferroni-corrected post-hoc Mann-Whitney test for each group. The incidence of dental implant fracture was 2.3% in the investigated cases. Improper treatment planning, bruxism, and time of the complication setting in were the main factors leading to this complication. Typical size effect was established only for available bruxism, occlusal errors, and their activity duration. These complications were observed most often with single crown prostheses, and in combination with parafunctional activities such as bruxism and lack of implant-protected occlusion. Occlusal overload due to bruxism or inappropriate or inadequate occlusion as a single factor or a combination of these factors during the first years after the functional load can cause implant fracture. Fracture of the implant body more frequently occurred with single crowns than with other implant-supported fixed dental prostheses.

  5. Analysis of dental caries using generalized linear and count regression models

    Directory of Open Access Journals (Sweden)

    Javali M. Phil

    2013-11-01

    Full Text Available Generalized linear models (GLM are generalization of linear regression models, which allow fitting regression models to response data in all the sciences especially medical and dental sciences that follow a general exponential family. These are flexible and widely used class of such models that can accommodate response variables. Count data are frequently characterized by overdispersion and excess zeros. Zero-inflated count models provide a parsimonious yet powerful way to model this type of situation. Such models assume that the data are a mixture of two separate data generation processes: one generates only zeros, and the other is either a Poisson or a negative binomial data-generating process. Zero inflated count regression models such as the zero-inflated Poisson (ZIP, zero-inflated negative binomial (ZINB regression models have been used to handle dental caries count data with many zeros. We present an evaluation framework to the suitability of applying the GLM, Poisson, NB, ZIP and ZINB to dental caries data set where the count data may exhibit evidence of many zeros and over-dispersion. Estimation of the model parameters using the method of maximum likelihood is provided. Based on the Vuong test statistic and the goodness of fit measure for dental caries data, the NB and ZINB regression models perform better than other count regression models.

  6. Diffraction stress analysis of thin films; investigating elastic grain interaction

    International Nuclear Information System (INIS)

    Kumar, A.

    2005-12-01

    This work is dedicated to the investigation of specimens exhibiting anisotropic microstructures (and thus macroscopic elastic anisotropy) and/or inhomogeneous microstructures, as met near surfaces and in textured materials. The following aspects are covered: (i) Analysis of specimens with direction-dependent (anisotropic) elastic grain-interaction. Elastic grain-interaction determines the distribution of stresses and strains over the (crystallographically) differently oriented grains of a mechanically stressed polycrystal and the mechanical and diffraction (X-ray) elastic constants (relating (diffraction) lattice strains to mechanical stresses). Grain interaction models that allow for anisotropic, direction-dependent grain interaction have been developed very recently. The notion 'direction-dependent' grain-interaction signifies that different grain-interaction constraints prevail along different directions in a specimen. Practical examples of direction-dependent grain interaction are the occurrence of surface anisotropy in thin films and the surface regions of bulk polycrystals and the occurrence of grain-shape (morphological) texture. In this work, for the first time, stress analyses of thin films have been performed on the basis of these newly developed grain-interaction models. It has also been demonstrated that the identification of the (dominant) source of direction-dependent grain interaction is possible. The results for the grain interaction have been discussed in the light of microstructural investigations of the specimens by microscopic techniques. (ii) Analysis of specimens with depth gradients: Diffraction stress analysis can be hindered if gradients of the stress state, the composition or the microstructure occur in the specimen under investigation, as the so-called information depth varies in the course of a traditional stress measurement: Ambiguous results are thus generally obtained. In this work, a strategy for stress measurements at fixed

  7. Stress analysis and evaluation of a rectangular pressure vessel

    International Nuclear Information System (INIS)

    Rezvani, M.A.; Ziada, H.H.; Shurrab, M.S.

    1992-10-01

    This study addresses structural analysis and evaluation of an abnormal rectangular pressure vessel, designed to house equipment for drilling and collecting samples from Hanford radioactive waste storage tanks. It had to be qualified according to ASME boiler and pressure vessel code, Section VIII; however, it had the cover plate bolted along the long face, a configuration not addressed by the code. Finite element method was used to calculate stresses resulting from internal pressure; these stresses were then used to evaluate and qualify the vessel. Fatigue is not a concern; thus, it can be built according to Section VIII, Division I instead of Division 2. Stress analysis was checked against the code. A stayed plate was added to stiffen the long side of the vessel

  8. Stress analysis of HTR-10 steam generator heat exchanging tubes

    International Nuclear Information System (INIS)

    Dong Jianling; Zhang Xiaohang; Yin Dejian; Fu Jiyang

    2001-01-01

    Steam Generator (SG) heat exchanging tubes of 10 MW High Temperature Gas Cooled Reactor (HTR-10) are protective screens between the primary loop of helium with radioactivity and the secondary loop of feeding water and steam without radioactivity. Water and steam will enter into the primary loop when rupture of the heat exchanging tubes occurs, which lead to increase of the primary loop pressure and discharge of radioactive materials. Therefore it is important to guarantee the integrity of the tubes. The tube structure is spiral tube with small bending radius, which make it impossible to test with volumetric in-service detection. For such kind of spiral tube, using LBB concept to guarantee the integrity of the tubes is an important option. The author conducts stress analysis and calculation of HTR-10 SG heat exchanging tubes using the FEM code of piping stress analysis, PIPESTRESS. The maximum stress and the dangerous positions are obtained

  9. Stress

    Science.gov (United States)

    ... can be life-saving. But chronic stress can cause both physical and mental harm. There are at least three different types of stress: Routine stress related to the pressures of work, family, and other daily responsibilities Stress brought about ...

  10. Dental students' self-assessment of operative preparations using CAD/CAM: a preliminary analysis.

    Science.gov (United States)

    Mays, Keith A; Levine, Eric

    2014-12-01

    The Commission on Dental Accreditation (CODA)'s accreditation standards for dental schools state that "graduates must demonstrate the ability to self-assess." Therefore, dental schools have developed preclinical and clinical self-assessment (SA) protocols aimed at fostering a reflective process. This study comparing students' visual SA with students' digital SA and with faculty assessment was designed to test the hypothesis that higher agreement would occur when utilizing a digital evaluation. Twenty-five first-year dental students at one dental school participated by preparing a mesial occlusal preparation on tooth #30 and performing both types of SAs. A faculty evaluation was then performed both visually and digitally using the same evaluation criteria. The Kappa statistic was used to measure agreement between evaluators. The results showed statistically significant moderate agreement between the faculty visual and faculty digital modes of evaluation for occlusal shape (K=0.507, p=0.002), proximal shape (K=0.564, p=0.001), orientation (K=0.425, p=0.001), and definition (K=0.480, p=0.001). There was slight to poor agreement between the student visual and faculty visual assessment, except for preparation orientation occlusal shape (K=0.164, p=0.022), proximal shape (K=-0.227, p=0.032), orientation (K=0.253, p=0.041), and definition (K=-0.027, p=0.824). This study showed that the students had challenges in self-assessing even when using CAD/CAM and the digital assessment did not improve the amount of student/faculty agreement.

  11. Dental caries and preterm birth: a systematic review and meta-analysis.

    Science.gov (United States)

    Wagle, Madhu; D'Antonio, Francesco; Reierth, Eirik; Basnet, Purusotam; Trovik, Tordis A; Orsini, Giovanna; Manzoli, Lamberto; Acharya, Ganesh

    2018-03-02

    The primary objective of this systematic review was to evaluate the association between dental caries and preterm birth (PTB). The secondary objective was ascertaining the difference between women with dental caries who experienced PTB and those who did not with regard to decayed, missing and filled teeth (DMFT), and decayed, missing and filled surfaces (DMFS) indices. MEDLINE, Embase, CINAHL and Cochrane databases were searched initially in November 2015 and repeated in December 2016. We included observational cohort and case-control studies. Only studies reporting the risk of PTB in women affected compared with those not affected by dental caries in pregnancy were included. Random-effect meta-analyses were used to compute the summary OR of PTB among women with caries versus women without caries, and the mean difference in either DMFT or DMFS indices between women experiencing PTB and those without PTB. Nine observational studies (4826 pregnancies) were included. Women affected by dental caries during pregnancy did not show a significantly higher risk of PTB (OR: 1.16, 95% CI 0.90 to 1.49, P=0.25, I 2 =35%). Also, the women with PTB did not show significantly higher DMFT or DMFS indices (summary mean differences: 1.56, P=0.10; I 2 =92% and -0.15, P=0.9, I 2 =89%, respectively). Dental caries does not appear to be a substantial risk factor for PTB. NCT01675180; Pre-results. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  12. Residual stress analysis of drive shafts after induction hardening

    Energy Technology Data Exchange (ETDEWEB)

    Lemos, Guilherme Vieira Braga; Rocha, Alexandre da Silva; Nunes, Rafael Menezes, E-mail: lemos_gl@yahoo.com.br [Universidade Federal do Rio Grande do Sul (UFRS), Porto Algre, RS (Brazil); Hirsch, Thomas Karl [Stiftung Institut für Werkstofftechnik (IWT), Bremen (Germany)

    2014-08-15

    Typically, for automotive shafts, shape distortion manifests itself in most cases after the induction hardening by an effect known as bending. The distortion results in a boost of costs, especially due to machining parts in the hardened state to fabricate its final tolerances. In the present study, residual stress measurements were carried out on automotive drive shafts made of DIN 38B3 steel. The samples were selected in consequence of their different distortion properties by an industrial manufacturing line. One tested shaft was straightened, because of the considerable dimensional variation and the other one not. Firstly, the residual stress measurements were carried out by using a portable diffractometer, in order to avoid cutting the shafts and evaluate the original state of the stresses, and afterwards a more detailed analysis was realized by a conventional stationary diffractometer. The obtained results presented an overview of the surface residual stress profiles after induction hardening and displayed the influence of the straightening process on the redistribution of residual stresses. They also indicated that the effects of the straightening in the residual stresses cannot be neglected. (author)

  13. Heat transfer and thermal stress analysis in grooved tubes

    Indian Academy of Sciences (India)

    Heat transfer and thermal stresses, induced by temperature differencesin the internally grooved tubes of heat transfer equipment, have been analysed numerically. The analysis has been conducted for four different kinds of internally grooved tubes and three different mean inlet water velocities. Constant temperature was ...

  14. Analysis of stress and deformation in non-stationary creep

    International Nuclear Information System (INIS)

    Feijoo, R.A.; Taroco, E.; Guerreiro, J.N.C.

    1980-12-01

    A variational method and its algorithm are presented; they permit the analysis of stress and deformation in non-stationary creep. This algorithm is applied to an infinite cylinder submitted to an internal pressure. The solution obtained is compared with the solution of non-stationary creep problems [pt

  15. ITER vacuum vessel dynamic stress analysis of a disruption

    International Nuclear Information System (INIS)

    Riemer, B.W.; Conner, D.L.; Strickler, D.J.; Williamson, D.E.

    1994-01-01

    Dynamic stress analysis of the International Thermonuclear Experimental Reactor vacuum vessel loaded by disruption forces was performed. The deformation and stress results showed strong inertial effects when compared to static analyses. Maximum stress predicted dynamically was 300 MPa, but stress shown by static analysis from loads at the same point in time reached only 80 MPa. The analysis also provided a reaction load history in the vessel's supports which is essential in evaluating support design. The disruption forces were estimated by assuming a 25-MA plasma current decaying at 1 MA/ms while moving vertically. In addition to forces developed within the vessel, vertical loadings from the first wall/strong back assemblies and the divertor were applied to the vessel at their attachment points. The first 50 natural modes were also determined. The first mode's frequency was 6.0 Hz, and its shape is characterized by vertical displacement of the vessel inner leg. The predicted deformation of the vessel appeared similar to its first mode shape combined with radial contraction. Kinetic energy history from the analysis also correlated with the first mode frequency

  16. Contact stress analysis of involute spur gear by Finite Element ...

    African Journals Online (AJOL)

    In this paper the contact stress in rolling-sliding contact of involute spur gear and the effect of coefficient of friction was analyzed. To achieve this, first, three dimensional involute spur gear pairs were developed in Solid works 2012 Premium and the 3D model was exported to ANSYS workbench 14.5. Next, the analysis was ...

  17. The Psychophysiology of Posttraumatic Stress Disorder: A Meta-Analysis

    Science.gov (United States)

    Pole, Nnamdi

    2007-01-01

    This meta-analysis of 58 resting baseline studies, 25 startle studies, 17 standardized trauma cue studies, and 22 idiographic trauma cue studies compared adults with and without posttraumatic stress disorder (PTSD) on psychophysiological variables: facial electromyography (EMG), heart rate (HR), skin conductance (SC), and blood pressure.…

  18. Stress analysis in oral obturator prostheses, part II: photoelastic imaging

    Science.gov (United States)

    Pesqueira, Aldiéris Alves; Goiato, Marcelo Coelho; da Silva, Emily Vivianne Freitas; Haddad, Marcela Filié; Moreno, Amália; Zahoui, Abbas; dos Santos, Daniela Micheline

    2014-06-01

    In part I of the study, two attachment systems [O-ring; bar-clip (BC)] were used, and the system with three individualized O-rings provided the lowest stress on the implants and the support tissues. Therefore, the aim of this study was to assess the stress distribution, through the photoelastic method, on implant-retained palatal obturator prostheses associated with different attachment systems: BOC-splinted implants with a bar connected to two centrally placed O-rings, and BOD-splinted implants with a BC connected to two distally placed O-rings (cantilever). One photoelastic model of the maxilla with oral-sinus-nasal communication with three parallel implants was fabricated. Afterward, two implant-retained palatal obturator prostheses with the two attachment systems described above were constructed. Each assembly was positioned in a circular polariscope and a 100-N axial load was applied in three different regions with implants by using a universal testing machine. The results were obtained through photograph record analysis of stress. The BOD system exhibited the highest stress concentration, followed by the BOC system. The O-ring, centrally placed on the bar, allows higher mobility of the prostheses and homogeneously distributes the stress to the region of the alveolar ridge and implants. It can be concluded that the use of implants with O-rings, isolated or connected with a bar, to rehabilitate maxillectomized patients allows higher prosthesis mobility and homogeneously distributes the stress to the alveolar ridge region, which may result in greater chewing stress distribution to implants and bone tissue. The clinical implication of the augmented bone support loss after maxillectomy is the increase of stress in the attachment systems and, consequently, a higher tendency for displacement of the prosthesis.

  19. Transcriptomic analysis of salt stress responsive genes in Rhazya stricta.

    Directory of Open Access Journals (Sweden)

    Nahid H Hajrah

    Full Text Available Rhazya stricta is an evergreen shrub that is widely distributed across Western and South Asia, and like many other members of the Apocynaceae produces monoterpene indole alkaloids that have anti-cancer properties. This species is adapted to very harsh desert conditions making it an excellent system for studying tolerance to high temperatures and salinity. RNA-Seq analysis was performed on R. stricta exposed to severe salt stress (500 mM NaCl across four time intervals (0, 2, 12 and 24 h to examine mechanisms of salt tolerance. A large number of transcripts including genes encoding tetrapyrroles and pentatricopeptide repeat (PPR proteins were regulated only after 12 h of stress of seedlings grown in controlled greenhouse conditions. Mechanisms of salt tolerance in R. stricta may involve the upregulation of genes encoding chaperone protein Dnaj6, UDP-glucosyl transferase 85a2, protein transparent testa 12 and respiratory burst oxidase homolog protein b. Many of the highly-expressed genes act on protecting protein folding during salt stress and the production of flavonoids, key secondary metabolites in stress tolerance. Other regulated genes encode enzymes in the porphyrin and chlorophyll metabolic pathway with important roles during plant growth, photosynthesis, hormone signaling and abiotic responses. Heme biosynthesis in R. stricta leaves might add to the level of salt stress tolerance by maintaining appropriate levels of photosynthesis and normal plant growth as well as by the participation in reactive oxygen species (ROS production under stress. We speculate that the high expression levels of PPR genes may be dependent on expression levels of their targeted editing genes. Although the results of PPR gene family indicated regulation of a large number of transcripts under salt stress, PPR actions were independent of the salt stress because their RNA editing patterns were unchanged.

  20. Thermal stress analysis of a planar SOFC stack

    Science.gov (United States)

    Lin, Chih-Kuang; Chen, Tsung-Ting; Chyou, Yau-Pin; Chiang, Lieh-Kwang

    The aim of this study is, by using finite element analysis (FEA), to characterize the thermal stress distribution in a planar solid oxide fuel cell (SOFC) stack during various stages. The temperature profiles generated by an integrated thermo-electrochemical model were applied to calculate the thermal stress distributions in a multiple-cell SOFC stack by using a three-dimensional (3D) FEA model. The constructed 3D FEA model consists of the complete components used in a practical SOFC stack, including positive electrode-electrolyte-negative electrode (PEN) assembly, interconnect, nickel mesh, and gas-tight glass-ceramic seals. Incorporation of the glass-ceramic sealant, which was never considered in previous studies, into the 3D FEA model would produce more realistic results in thermal stress analysis and enhance the reliability of predicting potential failure locations in an SOFC stack. The effects of stack support condition, viscous behavior of the glass-ceramic sealant, temperature gradient, and thermal expansion mismatch between components were characterized. Modeling results indicated that a change in the support condition at the bottom frame of the SOFC stack would not cause significant changes in thermal stress distribution. Thermal stress distribution did not differ significantly in each unit cell of the multiple-cell stack due to a comparable in-plane temperature profile. By considering the viscous characteristics of the glass-ceramic sealant at temperatures above the glass-transition temperature, relaxation of thermal stresses in the PEN was predicted. The thermal expansion behavior of the metallic interconnect/frame had a greater influence on the thermal stress distribution in the PEN than did that of the glass-ceramic sealant due to the domination of interconnect/frame in the volume of a planar SOFC assembly.

  1. Stress analysis of closure bolts for shipping casks

    International Nuclear Information System (INIS)

    Mok, G.C.; Fischer, L.E.; Hsu, S.T.

    1993-01-01

    This report specifies the requirements and criteria for stress analysis of closure bolts for shipping casks containing nuclear spent fuels or high level radioactive materials. The specification is based on existing information conceming the structural behavior, analysis, and design of bolted joints. The approach taken was to extend the ASME Boiler and Pressure Vessel Code requirements and criteria for bolting analysis of nuclear piping and pressure vessels to include the appropriate design and load characteristics of the shipping cask. The characteristics considered are large, flat, closure lids with metal-to-metal contact within the bolted joint; significant temperature and impact loads; and possible prying and bending effects. Specific formulas and procedures developed apply to the bolt stress analysis of a circular, flat, bolted closure. The report also includes critical load cases and desirable design practices for the bolted closure, an in-depth review of the structural behavior of bolted joints, and a comprehensive bibliography of current information on bolted joints

  2. Comparative proteomic analysis in Miscanthus sinensis exposed to antimony stress

    International Nuclear Information System (INIS)

    Xue, Liang; Ren, Huadong; Li, Sheng; Gao, Ming; Shi, Shengqing; Chang, Ermei; Wei, Yuan; Yao, Xiaohua; Jiang, Zeping; Liu, Jianfeng

    2015-01-01

    To explore the molecular basis of Sb tolerance mechanism in plant, a comparative proteomic analysis of both roots and leaves in Miscanthus sinensis has been conducted in combination with physiological and biochemical analyses. M. sinensis seedlings were exposed to different doses of Sb, and both roots and leaves were collected after 3 days of treatment. Two-dimensional gel electrophoresis (2-DE) and image analyses found that 29 protein spots showed 1.5-fold change in abundance in leaves and 19 spots in roots, of which 31 were identified by MALDI-TOF-MS and MALDI-TOF-TOF-MS. Proteins involved in antioxidant defense and stress response generally increased their expression all over the Sb treatments. In addition, proteins relative to transcription, signal transduction, energy metabolism and cell division and cell structure showed a variable expression pattern over Sb concentrations. Overall these findings provide new insights into the probable survival mechanisms by which M. sinensis could be adapting to Sb phytotoxicity. - Highlights: • Proteomics in Miscanthus sinensis leaves and roots exposed to Sb stress were studied. • There were 31 spots that were identified by mass spectrometry. • Most of these proteins were involved in antioxidant defense and stress response. • Our findings provide new insights into the tolerant mechanisms to Sb stress. - Miscanthus sinensis proteomic analysis under Sb stress reveals probable molecular mechanisms on Sb detoxification

  3. Dental hygiene habits and oral health status of seafarers.

    Science.gov (United States)

    Mahdi, Syed Sarosh; Sibilio, Fabio; Amenta, Francesco

    2016-01-01

    This study has assessed the dental hygiene habits and problems of seafarers and their attitudes/ perceptions regarding oral hygiene using a dental hygiene/habits questionnaire. A research questionnaire on oral hygiene habits was prepared along with a summary of all the questions and sent to ships via e-mail by Centro Internazionale Radio Medico (CIRM) networks. CIRM, is the Italian Telemedical Maritime Assistance Service (TMAS), and represents the Centre with the largest number of seafarers assisted on board ships worldwide. CIRM proposed the questionnaire to all ships (n = 1,198) asking for medical advice from 1 July 2014 till 31 October 2014. Two dental professionals were involved in the development and analysis of the questionnaire. Seafarers are at risk of several dental health problems due to their oral hygiene and dietary habits, smoking and alcohol consumption, poor oral hygiene knowledge and motivation. Dietary habits during voyages were also questionable and seafarers consume food rich in fermentable carbohydrates, which is a major risk factor for dental caries. Seafarers need better oral hygiene education and care to enable them to manage their oral health in a better way. Life at the sea, under challenging circumstances is not without stress, that is why it is important that seafarers are given complete information about correct oral hygiene protocols and dental hygiene and the advantages for their health of keeping a healthy mouth.

  4. Dynamical System Analysis of Reynolds Stress Closure Equations

    Science.gov (United States)

    Girimaji, Sharath S.

    1997-01-01

    In this paper, we establish the causality between the model coefficients in the standard pressure-strain correlation model and the predicted equilibrium states for homogeneous turbulence. We accomplish this by performing a comprehensive fixed point analysis of the modeled Reynolds stress and dissipation rate equations. The results from this analysis will be very useful for developing improved pressure-strain correlation models to yield observed equilibrium behavior.

  5. Stress analysis of heated concrete using finite elements

    International Nuclear Information System (INIS)

    Majumdar, P.; Gupta, A.; Marchertas, A.

    1994-01-01

    Described is a finite element analysis of concrete, which is subjected to rapid heating. Using thermal mass transport calculation, the moisture content, temperature and pore pressure distribution over space and time is obtained first. From these effects, stress at various points of the concrete are computed using the finite element method. Contribution to the stress formulation comes from three components, namely the thermal expansion, pore pressure, and the shrinkage of concrete due to moisture loss (from dehydration). The material properties of concrete are assumed to be homogeneous, elastic, and cracking is not taken into consideration. (orig.)

  6. A multimodal stress monitoring system with canonical correlation analysis.

    Science.gov (United States)

    Unsoo Ha; Changhyeon Kim; Yongsu Lee; Hyunki Kim; Taehwan Roh; Hoi-Jun Yoo

    2015-08-01

    The multimodal stress monitoring headband is proposed for mobile stress management system. It is composed of headband and earplugs. Electroencephalography (EEG), hemoencephalography (HEG) and heart-rate variability (HRV) can be achieved simultaneously in the proposed system for user status estimation. With canonical correlation analysis (CCA) and temporal-kernel CCA (tkCCA) algorithm, those different signals can be combined for maximum correlation. Thanks to the proposed combination algorithm, the accuracy of the proposed system increased up to 19 percentage points than unimodal monitoring system in n-back task.

  7. Exploring Dental Providers' Workflow in an Electronic Dental Record Environment.

    Science.gov (United States)

    Schwei, Kelsey M; Cooper, Ryan; Mahnke, Andrea N; Ye, Zhan; Acharya, Amit

    2016-01-01

    A workflow is defined as a predefined set of work steps and partial ordering of these steps in any environment to achieve the expected outcome. Few studies have investigated the workflow of providers in a dental office. It is important to understand the interaction of dental providers with the existing technologies at point of care to assess breakdown in the workflow which could contribute to better technology designs. The study objective was to assess electronic dental record (EDR) workflows using time and motion methodology in order to identify breakdowns and opportunities for process improvement. A time and motion methodology was used to study the human-computer interaction and workflow of dental providers with an EDR in four dental centers at a large healthcare organization. A data collection tool was developed to capture the workflow of dental providers and staff while they interacted with an EDR during initial, planned, and emergency patient visits, and at the front desk. Qualitative and quantitative analysis was conducted on the observational data. Breakdowns in workflow were identified while posting charges, viewing radiographs, e-prescribing, and interacting with patient scheduler. EDR interaction time was significantly different between dentists and dental assistants (6:20 min vs. 10:57 min, p = 0.013) and between dentists and dental hygienists (6:20 min vs. 9:36 min, p = 0.003). On average, a dentist spent far less time than dental assistants and dental hygienists in data recording within the EDR.

  8. Radiographic Assessment of Dental Maturation in Children With Dental Agenesis.

    Science.gov (United States)

    Medina, Aida Carolina; Pozo, Rodrigo Del; de Cedres, Lucila Blanco

    Dental agenesis is the most common developmental anomaly in humans, frequently associated with disorders in dental development and maturation. The purpose of this study is to determine radiographic variations in dental maturation in a group of Venezuelan children with dental agenesis. 1,188 panoramic radiographs, from healthy patients ages 5 to 12 years old were studied for agenesis of permanent teeth. Dental maturation was assessed by relative eruption and dental age according to Nolla, comparing children affected with dental agenesis to a stratified control group selected from the same population, excluding children with premature loss of primary teeth in the left quadrants and unclear radiographs. Descriptive analysis, and differences between means and medians (Student t test, Kruskall-Wallis p=0.05) were performed. Medians for Nolla stages were similar between groups, with delay in tooth formation in the agenesis group for second molars (p<0.05) and maxillary lateral incisors and second premolars. Dental age was significantly underestimated for both groups, -0.89 (±0.78) for the control group and -1.20 (±0.95) for the study group. Tooth eruption was similar between groups. Dental age was significantly delayed in Venezuelan children with dental agenesis, with variable significance for tooth formation of studied teeth.

  9. Fracture toughness of esthetic dental coating systems by nanoindentation and FIB sectional analysis.

    Science.gov (United States)

    Pecnik, Christina Martina; Courty, Diana; Muff, Daniel; Spolenak, Ralph

    2015-07-01

    Improving the esthetics of Ti-based dental implants is the last challenge remaining in the optimization process. The optical issues were recently solved by the application of highly and selectively reflective coatings on Ti implants. This work focuses on the mechanical durability of these esthetic ceramic based coating systems (with and without adhesion layers). The coating systems (Ti-ZrO2, Ti-Al-ZrO2, Ti-Ti-Al-ZrO2, Ti-Ag-ZrO2, Ti-Ti-Ag-ZrO2, Ti-Bragg and Ti-TiO2-Bragg) were subjected to nanoindentation experiments and examined using scanning electron microscopy and focused ion beam cross sectional analysis. Three coating systems contained adhesion layers (10nm of Ti or 60nm of TiO2 layers). The fracture toughness of selected samples was assessed applying two different models from literature, a classical for bulk materials and an energy-based model, which was further developed and adjusted. The ZrO2 based coating systems (total film thickness<200nm) followed a circumferential cracking behavior in contrast to Bragg coated samples (total film thickness around 1.5μm), which showed radial cracking emanating from the indent corners. For Ti-ZrO2 samples, a fracture toughness between 2.70 and 3.70MPam(1/2) was calculated using an energy-based model. The classical model was applied to Bragg coated samples and their fracture toughness ranged between 0.70 and 0.80MPam(1/2). Furthermore, coating systems containing an additional layer (Ti-Ti-Al-ZrO2, Ti-Ti-Ag-ZrO2 and Ti-TiO2-Bragg) showed an improved adhesion between the substrate and the coating. The addition of a Ti or TiO2 layer improved the adhesion between substrate and coating. The validity of the models for the assessment of the fracture toughness depended on the layer structure and fracture profile of the samples investigated here (classical model for thick coatings and energy-based model for thin coatings). Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Dielectric analysis of depth dependent curing behavior of dental resin composites.

    Science.gov (United States)

    Steinhaus, Johannes; Moeginger, Bernhard; Grossgarten, Mandy; Rosentritt, Martin; Hausnerova, Berenika

    2014-06-01

    The aim of this study is to investigate depth dependent changes of polymerization process and kinetics of visible light-curing (VLC) dental composites in real-time. The measured quantity - "ion viscosity" determined by dielectric analysis (DEA) - provides the depth dependent reaction rate which is correlated to the light intensity available in the corresponding depths derived from light transmission measurements. The ion viscosity curves of two composites (VOCO Arabesk Top and Grandio) were determined during irradiation of 40s with a light-curing unit (LCU) in specimen depths of 0.5/0.75/1.0/1.25/1.5/1.75 and 2.0mm using a dielectric cure analyzer (NETZSCH DEA 231 with Mini IDEX sensors). The thickness dependent light transmission was measured by irradiation composite specimens of various thicknesses on top of a radiometer setup. The shape of the ion viscosity curves depends strongly on the specimen thickness above the sensor. All curves exhibit a range of linear time dependency of the ion viscosity after a certain initiation time. The determined initiation times, the slopes of the linear part of the curves, and the ion viscosities at the end of the irradiation differ significantly with depth within the specimen. The slopes of the ion viscosity curves as well as the light intensity values decrease with depth and fit to the Lambert-Beer law. The corresponding attenuation coefficients are determined for Arabesk Top OA2 to 1.39mm(-1) and 1.48mm(-1), respectively, and for Grandio OA2 with 1.17 and 1.39mm(-1), respectively. For thicknesses exceeding 1.5mm a change in polymerization behavior is observed as the ion viscosity increases subsequent to the linear range indicating some kind of reaction acceleration. The two VLC composites and different specimen thicknesses discriminate significantly in their ion viscosity evolution allowing for a precise characterization of the curing process even with respect to the polymerization mechanism. Copyright © 2014. Published by

  11. Correlation Between Resonance Frequency Analysis and Bone Quality Assessments at Dental Implant Recipient Sites.

    Science.gov (United States)

    Fu, Min-Wen; Fu, Earl; Lin, Fu-Gong; Chang, Wei-Jeng; Hsieh, Yao-Dung; Shen, E-Chin

    To evaluate whether primary implant stability could be used to predict bone quality, the association between the implant stability quotient (ISQ) value and the bone type at the implant site was evaluated. Ninety-five implant sites in 50 patients were included. Bone type (categorized by Lekholm and Zarb) at the implant site was initially assessed using presurgical dental radiography. During the preparation of the implant site, a bone core specimen was carefully obtained. The bone type was assessed by tactile sensation during the drilling operation, according to the Misch criteria. The primary stability of the inserted implant was evaluated by resonance frequency analysis (RFA). The ISQ value was recorded. The bone core specimen was then examined by stereomicroscopy or microcomputed tomography (micro-CT), and the bone type was determined by the surface characteristics of the specimen, based on Lekholm and Zarb classification. Agreement between the bone quality assessed by the four methods (ie, presurgical radiography, tactile sensation, stereomicroscopy, and micro-CT) was tested by Cohen's kappa statistics, whereas the association between the ISQ value and the bone type was evaluated by the generalized linear regression model. The mean ISQ score was 72.6, and the score was significantly influenced by the maxillary or mandibular arch (P = .001). The bone type at the implant sites varied according to the assessment method. However, a significant influence of the arch was repeatedly noted when using radiography or tactile sensation. Among the four bone-quality assessment methods, a weak agreement existed only between stereomicroscopy and micro-CT, especially in the maxilla (κ = 0.469). A negative association between the ISQ value and the bone type assessed by stereomicroscopy or by micro-CT was significant in the maxilla, but not in the mandible, after adjustments for sex, age, and right/left side (P = .013 and P = .027 for stereomicroscopy and micro-CT, respectively

  12. The rise and fall of dental therapy in Canada: a policy analysis and assessment of equity of access to oral health care for Inuit and First Nations communities.

    Science.gov (United States)

    Leck, Victoria; Randall, Glen E

    2017-07-20

    Inequality between most Canadians and those from Inuit and First Nations communities, in terms of both access to oral health care services and related health outcomes, has been a long-standing problem. Efforts to close this equity gap led to the creation of dental therapy training programs. These programs were designed to produce graduates who would provide services in rural and northern communities. The closure of the last dental therapy program in late 2011 has ended the supply of dental therapists and governments do not appear to have any alternative solutions to the growing gap in access to oral health care services between most Canadians and those from Inuit and First Nations communities. A policy analysis of the rise and fall of the dental therapy profession in Canada was conducted using historical and policy documents. The analysis is framed within Kingdon's agenda-setting framework and considers why dental therapy was originally pursued as an option to ensure equitable access to oral health care for Inuit and First Nations communities and why this policy has now been abandoned with the closure of Canada's last dental therapy training school. The closure of the last dental therapy program in Canada has the potential to further reduce access to dental care in some Inuit and First Nations communities. Overlaps between federal and provincial jurisdiction have contributed to the absence of a coordinated policy approach to address the equity gap in access to dental care which will exacerbate the inequalities in comparison to the general population. The analysis suggests that while a technically feasible policy solution is available there continues to be no politically acceptable solution and thus it remains unlikely that a window of opportunity for policy change will open any time soon. In the absence of federal government leadership, the most viable option forward may be incremental policy change. Provincial governments could expand the scope of practice for

  13. Regular and platform switching: bone stress analysis varying implant type.

    Science.gov (United States)

    Gurgel-Juarez, Nália Cecília; de Almeida, Erika Oliveira; Rocha, Eduardo Passos; Freitas, Amílcar Chagas; Anchieta, Rodolfo Bruniera; de Vargas, Luis Carlos Merçon; Kina, Sidney; França, Fabiana Mantovani Gomes

    2012-04-01

    This study aimed to evaluate stress distribution on peri-implant bone simulating the influence of platform switching in external and internal hexagon implants using three-dimensional finite element analysis. Four mathematical models of a central incisor supported by an implant were created: External Regular model (ER) with 5.0 mm × 11.5 mm external hexagon implant and 5.0 mm abutment (0% abutment shifting), Internal Regular model (IR) with 4.5 mm × 11.5 mm internal hexagon implant and 4.5 mm abutment (0% abutment shifting), External Switching model (ES) with 5.0 mm × 11.5 mm external hexagon implant and 4.1 mm abutment (18% abutment shifting), and Internal Switching model (IS) with 4.5 mm × 11.5 mm internal hexagon implant and 3.8 mm abutment (15% abutment shifting). The models were created by SolidWorks software. The numerical analysis was performed using ANSYS Workbench. Oblique forces (100 N) were applied to the palatal surface of the central incisor. The maximum (σ(max)) and minimum (σ(min)) principal stress, equivalent von Mises stress (σ(vM)), and maximum principal elastic strain (ε(max)) values were evaluated for the cortical and trabecular bone. For cortical bone, the highest stress values (σ(max) and σ(vm) ) (MPa) were observed in IR (87.4 and 82.3), followed by IS (83.3 and 72.4), ER (82 and 65.1), and ES (56.7 and 51.6). For ε(max), IR showed the highest stress (5.46e-003), followed by IS (5.23e-003), ER (5.22e-003), and ES (3.67e-003). For the trabecular bone, the highest stress values (σ(max)) (MPa) were observed in ER (12.5), followed by IS (12), ES (11.9), and IR (4.95). For σ(vM), the highest stress values (MPa) were observed in IS (9.65), followed by ER (9.3), ES (8.61), and IR (5.62). For ε(max) , ER showed the highest stress (5.5e-003), followed by ES (5.43e-003), IS (3.75e-003), and IR (3.15e-003). The influence of platform switching was more evident for cortical bone than for trabecular bone, mainly for the external hexagon

  14. Composite Analysis of Concrete - Creep, Relaxation and Eigenstrain/stress

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1996-01-01

    approach.The model is successfully justified comparing predicted results with recent experimental data obtained in tests made at the Danish Technological Institute and at the Technical University of Denmark on creep, relaxation, and shrinkage of very young concretes (hours) - and also with experimental...... results on creep, shrinkage, and internal stresses caused by drying shrinkage reported in the literature on the mechanical behavior of mature concretes.Shrinkage (autogeneous or drying) of mortar and concrete and associated internal stress states are examples of analysis made in this report......A composite-rheological model of concrete is presented by which consistent predictions of creep, relaxation, and internal stresses can be made from known concrete composition, age at loading, and climatic conditions. No other existing "creep prediction method" offers these possibilities in one...

  15. Quality image analysis and radiation protection in dental radiodiagnosis in Sobral city, BA, Brazil

    International Nuclear Information System (INIS)

    Menezes, Francisca L.; Ferreira, Fernanda C.L.; Paschoal, Cinthia M.M.; Belinato, Walmir

    2015-01-01

    The radiographic processing is one of the steps to acquire radiographic images and requires appropriate quality control. The image should allow an accurate diagnosis and avoid repetition of examinations, which is consistent with the principles of radiation protection. This study aimed to verify the quality of periapical radiographic imaging and to investigate the suitability of dental X-ray equipment on the principles of radiation protection established by the Health Ministry Decree 453/98, by applying radiation field test and application questionnaires to dentists professionals. The result showed that it takes greater care professionals about the treatment radiographic and radiation protection, requiring that inspection agencies require compliance with the rules so that there is maintaining the quality of dental diagnostic radiology services. (author)

  16. Micromechanical combined stress analysis: MICSTRAN, a user manual

    Science.gov (United States)

    Naik, R. A.

    1992-01-01

    Composite materials are currently being used in aerospace and other applications. The ability to tailor the composite properties by the appropriate selection of its constituents, the fiber and matrix, is a major advantage of composite materials. The Micromechanical Combined Stress Analysis (MICSTRAN) code provides the materials engineer with a user-friendly personal computer (PC) based tool to calculate overall composite properties given the constituent fiber and matrix properties. To assess the ability of the composite to carry structural loads, the materials engineer also needs to calculate the internal stresses in the composite material. MICSTRAN is a simple tool to calculate such internal stresses with a composite ply under combined thermomechanical loading. It assumes that the fibers have a circular cross-section and are arranged either in a repeating square or diamond array pattern within a ply. It uses a classical elasticity solution technique that has been demonstrated to calculate accurate stress results. Input to the program consists of transversely isotropic fiber properties and isotropic matrix properties such as moduli, Poisson's ratios, coefficients of thermal expansion, and volume fraction. Output consists of overall thermoelastic constants and stresses. Stresses can be computed under the combined action of thermal, transverse, longitudinal, transverse shear, and longitudinal shear loadings. Stress output can be requested along the fiber-matrix interface, the model boundaries, circular arcs, or at user-specified points located anywhere in the model. The MICSTRAN program is Windows compatible and takes advantage of the Microsoft Windows graphical user interface which facilitates multitasking and extends memory access far beyond the limits imposed by the DOS operating system.

  17. Factors associated with dental implant survival: a 4-year retrospective analysis.

    Science.gov (United States)

    Zupnik, Jamie; Kim, Soo-woo; Ravens, Daniel; Karimbux, Nadeem; Guze, Kevin

    2011-10-01

    Dental implants are a predictable treatment option for replacing missing teeth and have strong survival and success outcomes. However, previous research showed a wide array of potential risk factors that may have contributed to dental implant failures. The objectives of this study are to study if implant survival rates were affected by known risk factors and risk indicators that may have contributed to implant failures. The secondary outcome measures were whether the level of expertise of the periodontal residents affected success rates and how the rate of implant success at the Harvard School of Dental Medicine (HSDM) compared to published standards. A retrospective chart review of patients at the HSDM who had one of two types of rough-surface implants (group A or B) placed by periodontology residents from 2003 to 2006 was performed. Demographic, health, and implant data were collected and analyzed by multimodel analyses to determine failure rates and any factors that may have increased the likelihood of an implant failure. The study cohort included 341 dental implants. The odds ratio for an implant failure was most clearly elevated for diabetes (2.59 implant surface group B (7.84), and male groups (4.01). There was no significant difference regarding the resident experience. The success rate for HSDM periodontology residents was 96.48% during the 4-year study period. This study demonstrates that implant success rates at HSDM fell within accepted published standards, confirmed previously identified risk factors for a failure, and potentially suggested that other acknowledged risk factors could be controlled for. Furthermore, the level of experience of the periodontology resident did not have an impact on survival outcomes.

  18. Panographic Survey of U. S. Army Recruits: Analysis of Dental Health Status.

    Science.gov (United States)

    1981-09-16

    pathoses which may not be evident on a routine periapical survey.3-6 The advantages of panoramic radiography make it particularly attractive for mass...perlapical radiolucencles. Radiolucent lesions, other than periapical or anatomical, were recorded separately. Folli- cular enlargements (over 3 m) surrounding...retention cysts . RESULTS Table I summarizes the findings. Dental Caries. A 58 percent incidence of carious lesions was noted overall. Many of these lesions

  19. Stress analysis in a non axisymmetric loaded reactor pressure vessel

    International Nuclear Information System (INIS)

    Albuquerque, Levi Barcelos; Assis, Gracia Menezes V. de; Miranda, Carlos Alexandre J.; Cruz, Julio Ricardo B.; Mattar Neto, Miguel

    1995-01-01

    In this work we intend to present the stress analysis of a PWR vessel under postulated concentrated loads. The vessel was modeled with Axisymmetric solid 4 nodes harmonic finite elements with the use of the ANSYS program, version 5.0. The bolts connecting the vessel flanges were modeled with beam elements. Some considerations were made to model the contact between the flanges. The perforated part of the vessel tori spherical head was modeled (with reduced properties due to its holes) to introduce its stiffness and loads but was not within the scope of this work. The loading consists of some usual ones, as pressure, dead weight, bolts preload, seismic load and some postulated ones as concentrated loads, over the vessel, modeled by Fourier Series. The results in the axisymmetric model are taken in terms of linearized stresses, obtained in some circumferential positions and for each position, in some sections along the vessel. Using the ASME Code (Section III, Division 1, Sub-section NB) the stresses are within the allowable limits. In order to draw some conclusions about stress linearization, the membrane plus bending stresses (Pl + Pb) are obtained and compared in some sections, using three different methods. (author)

  20. Numerical Analysis of Masticatory Forces on a Lower First Molar considering the Contact between Dental Tissues

    Directory of Open Access Journals (Sweden)

    Rosa Alicia Hernández-Vázquez

    2018-01-01

    Full Text Available The aim of the present work is to identify the reactions of the dental organs to the different forces that occur during chewing and the transcendence of the union and contact maintained by the dental tissues. The study used a lower first molar biomodel with a real morphology and morphometry and consisting of the three dental tissues (enamel, dentin, and pulp each with its mechanical properties. In it, two simulations were carried out, as would the process of chewing a food. One of the simulations considers the contact between the enamel and the dentin, and the other does not take it into account. The results obtained differ significantly between the simulations that consider contact and those that do not, establishing the importance of taking this contact into account. In this way, the theories that establish horizontal and lateral occlusion forces are present during the functional chewing process which are viable to be correct. The case studies carried out present not only the reasons for the failure of enamel but also the failure of the restoration materials used. This reflection will allow the development of more adequate materials, mechanical design of prostheses, implants, and treatment.

  1. Failure analysis of the ball bearings of dental air turbine handpieces.

    Science.gov (United States)

    Wei, M; Dyson, J E; Darvell, B W

    2013-12-01

    The aim of this study was to identify the nature and causes of deterioration and failure in dental handpiece ball bearings and thus provide guidance for clinical handling for service longevity. The bearings of 36 turbine assemblies were dismantled for visual inspection, documented using a digital camera, and examined using scanning electron microscopy, as appropriate. For the metal parts of the ball bearing assembly, defects observed were mainly wear arising from the running load and corrosion. This was in the form of scratches and discoloured circumferential bands on the balls, and dull or worn surfaces extending around the circumference of the raceways. Cage damage including cracking, fracture, surface rubbing and distortion occurred, in varying degrees, in every failed turbine. Dental ball bearing failure modes have been identified. Cumulative effects of damage from corrosion and mechanical factors lead to handpiece deterioration. The cage was found to be very vulnerable to damage, and this may be the key limitation on bearing lifetime. Autoclaving may contribute to that, as it does to corrosion in the absence of adequate lubrication, but this seems to be minor in comparison to the effects of abuse. There is no justification for failing to observe usage and sterilization instructions. © 2013 Australian Dental Association.

  2. Analysis of optical transmission by 400-500 nm visible light into aesthetic dental biomaterials.

    Science.gov (United States)

    Watts, D C; Cash, A J

    1994-04-01

    The penetration of visible light into dental biomaterials is an essential factor in photoinitiation of setting reactions and in the optical aspects of dental aesthetics. Light of visible blue wavelengths, 400-500 nm, has been applied at normal angles to 0.2-5.0 mm sections of human dentine and representative ceramic, polymerceramic composites and hybrid glass-polyalkenoate materials. The integrated optical transmission has been determined for each material section. The data have been converted to absorbance values and analysed to check for mathematical conformity to the Beer-Lambert Law. It is found that conformity (typically, P ratio. This factor ranges from 30% to 90% in the materials investigated. It follows that there is a high degree of inefficiency in the transmission of visible light into and through aesthetic biomaterials for the purposes of photoactivation using existing technology. Means by which this limitation and inefficiency may be reduced are discussed. While the reflectivity of aesthetic biomaterials has been perceived by dental practitioners, the magnitude of this effect and its implications in connection with light-cured materials have not been analysed and emphasized hitherto.

  3. Structural, Surface, in vitro Bacterial Adhesion and Biofilm Formation Analysis of Three Dental Restorative Composites

    Directory of Open Access Journals (Sweden)

    Maria T. Azam

    2015-06-01

    Full Text Available This study was conducted to investigate the relationship between dental materials and bacterial adhesion on the grounds of their chemical composition and physical properties. Three commercially available dental restorative materials (Filtek™Z350, Filtek™P90 and Spectrum®TPH® were structurally analyzed and their wettability and surface roughness were evaluated by using Fourier Transform Infrared Spectroscopy, Contact Angle Measurement and Atomic Force Microscopy, respectively. These materials were molded into discs and tested with three bacterial strains (Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia for microbial attachment. The bacterial adhesion was observed at different time intervals, i.e., 0 h, 8 h, 24 h, 48 h and 72 h, along with Colony Forming Unit Count and Optical Density measurement of the media. It was found that all materials showed a degree of conversion with time intervals, i.e., 0 h, 8 h, 24 h, 48 h and 72 h, which led to the availability of functional groups (N–H and C–H that might promote adhesion. The trend in difference in the extent of bacterial adhesion can be related to particle size, chemical composition and surface wettability of the dental materials.

  4. Joining U.S. NRC international round robin for weld residual stress analysis. Stress analysis and validation in PWSCC mitigation program

    International Nuclear Information System (INIS)

    Maekawa, Akira; Serizawa, Hisashi; Murakawa, Hidekazu

    2012-01-01

    It is necessary to establish properly reliable weld residual stress analysis methods for accurate crack initiation and growth assessment of primary water stress corrosion cracking (PWSCC), which may occur in nickel-based dissimilar metal welds in pressurized water reactors. The U.S. Nuclear Regulatory Commission conducted an international round robin for weld residual stress analysis to improve stress analysis methods and to examine the uncertainties involved in the calculated stress values. In this paper, the results from the authors' participation in the round robin were reported. In the round robin, the weld residual stress in a nickel-based dissimilar metal weld of a pressurizer surge nozzle mock-up was computed under various analysis conditions. Based on these residual stress analysis results, a welding simulation code currently being developed that uses the iterative substructure method was validated and affecting factors on the analysis results were identified. (author)

  5. Use of Shark Dental Protein to Estimate Trophic Position via Amino Acid Compound-Specific Isotope Analysis

    Science.gov (United States)

    Hayes, M.; Herbert, G.; Ellis, G.

    2017-12-01

    The diets of apex predators such as sharks are expected to change in response to overfishing of their mesopredator prey, but pre-anthropogenic baselines necessary to test for such changes are lacking. Stable isotope analysis (SIA) of soft tissues is commonly used to study diets in animals based on the bioaccumulation of heavier isotopes of carbon and nitrogen with increasing trophic level. In specimens representing pre-anthropogenic baselines, however, a modified SIA approach is needed to deal with taphonomic challenges, such as loss of soft tissues or selective loss of less stable amino acids (AAs) in other sources of organic compounds (e.g., teeth or bone) which can alter bulk isotope values. These challenges can be overcome with a compound-specific isotope analysis of individual AAs (AA-CSIA), but this first requires a thorough understanding of trophic enrichment factors for individual AAs within biomineralized tissues. In this study, we compare dental and muscle proteins of individual sharks via AA-CSIA to determine how trophic position is recorded within teeth and whether that information differs from that obtained from soft tissues. If skeletal organics reliably record information about shark ecology, then archaeological and perhaps paleontological specimens can be used to investigate pre-anthropogenic ecosystems. Preliminary experiments show that the commonly used glutamic acid/phenylalanine AA pairing may not be useful for establishing trophic position from dental proteins, but that estimated trophic position determined from alternate AA pairs are comparable to those from muscle tissue within the same species.

  6. Effects of holmium laser on dental structure in vivo: thermal evaluation and histological analysis on pulpal tissue

    International Nuclear Information System (INIS)

    Strefezza, Claudia

    2001-01-01

    Previous in vitro studies have demonstrated that Ho:YLF laser is capable of inducing physical and chemical changes on dental surfaces treated for caries prevention. The temperature in the pulp chamber was in vitro evaluated to as a function of the power and frequency of the laser irradiation. The purpose of this work is to verify the occurrence of pulp inflammation after Ho:YLF laser irradiation using different parameters in rabbits' teeth. The premolars and molars of ten rabbits (NZB) were divided in two groups according to the irradiation energy values of a Ho:YLF laser prototype operating at 2.065μm wave length, frequency of O,5Hz and pulse length of 250μs. An group A teeth were irradiated with using ten pulses of 334mJ/pulse of a Ho:YLF laser prototype operating at O.5Hz, and group B, with 512mJ/pulse. Animals were killed by transcardiac perfusion and the samples were prepared for histopathological analysis. The in vitro temperature monitoring revealed an increase of 1 deg C for the 334mJ/pulse energy and 4.5 deg C for the 512mJ/pulse energy. SEM observations showed the occurrence of melting and resolidification in dental surface. From the in vivo analysis it can be concluded that both employed laser parameters did not induce to any inflammatory response from the pulp. (author)

  7. [Occupational stress situation analysis of different types of train drivers].

    Science.gov (United States)

    Zhou, Wenhui; Gu, Guizhen; Wu, Hui; Yu, Shanfa

    2014-11-01

    To analyze the status of occupational stress in different types of train drivers. By using cluster sampling method, a cross-sectional study was conducted in 1 339 train drivers (including 289 passenger train drivers, 637 freight trains drivers, 339 passenger shunting train drivers, and 74 high speed rail drivers) from a Railway Bureau depot. The survey included individual factors, occupational stress factors, stress response factors and stress mitigating factors. The occupational stress factors, stress response factors and mitigating factors were measured by the revised effort-reward imbalance (ERI) model questionnaires and occupational stress measurement scale. By using the method of covariance analysized the difference of occupational stress factors of all types train drivers, the method of Stepwise regression was used to analyze the effection (R(2)) of occupational stress factors and stress mitigating factors on stress response factors. Covariance analysis as covariates in age, education level, length of service and marital status showed that the scores of ERI (1.58 ± 0.05), extrinsic effort (19.88 ± 0.44), rewards (23.43 ± 0.43), intrinsic effort (17.86 ± 0.36), physical environment (5.70 ± 0.22), social support (30.51 ± 0.88) and daily tension (10.27 ± 0.38 ) of high speed rail drivers were higher than other drivers (F values were 6.06, 11.32, 7.05, 13.25, 5.20, 9.48 and 6.14 respectively, P occupational stress factors and mitigating factors to depressive symptoms of train drivers was high speed rail drivers (R(2) = 0.64), passenger train drivers (R(2) = 0.44), passenger shunting train drivers (R(2) = 0.39), freight trains drivers (R(2) = 0.38); job satisfaction of train drivers was high speed rail drivers (R(2) = 0.68), passenger train drivers (R(2) = 0.62), freight trains drivers (R(2) = 0.43), passenger shunting train drivers(R(2) = 0.38); to daily tension of train drivers was high speed rail drivers (R(2) = 0.54), passenger train drivers (R(2) = 0

  8. Dental implants in growing children

    Directory of Open Access Journals (Sweden)

    S K Mishra

    2013-01-01

    Full Text Available The replacement of teeth by implants is usually restricted to patients with completed craniofacial growth. The aim of this literature review is to discuss the use of dental implants in normal growing patients and in patients with ectodermal dysplasia and the influence of maxillary and mandibular skeletal and dental growth on the stability of those implants. It is recommended that while deciding the optimal individual time point of implant insertion, the status of skeletal growth, the degree of hypodontia, and extension of related psychological stress should be taken into account, in addition to the status of existing dentition and dental compliance of a pediatric patient.

  9. Advancing education in dental hygiene.

    Science.gov (United States)

    Battrell, Ann; Lynch, Ann; Steinbach, Pam; Bessner, Sue; Snyder, Josh; Majeski, Jean

    2014-06-01

    The changing health care environment and societal imperatives indicate the need for transformative change within the dental hygiene profession to serve the emerging needs of the public. The American Dental Hygienists' Association is leading the way toward meaningful change. The American Dental Hygienists' Association (ADHA) has as its vision the integration of dental hygienists into the health care delivery system as essential primary care providers to expand access to oral health care. This article provides data on current dental hygiene education programs and those in development. Also included is a discussion regarding how the dental hygiene profession can better serve the health and wellness needs of society by transforming the way graduates are prepared for the future. ADHA's dental hygiene survey center data, policies and a futuristic analysis plus a review of the professional literature describe the current state of dental hygiene education and the profession. A discussion of societal, health care and educational trends that creates the imperative for transformation of the dental hygiene profession is provided. Ultimately, the purpose of advancing education in dental hygiene is to achieve better oral and overall health for more people. The profession's responsibility to the public includes evaluating its own ability to provide care and taking the steps necessary to ensure its maximum effectiveness. ADHA is leading this process for dental hygienists in diverse ways. It is imperative that the dental hygiene profession understands and embraces the changing health care environment. Through open dialog and the sharing of evidence the professional path will be determined along with forward movement for the benefit of society and the dental hygiene profession. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. Influence of retainer design on two-unit cantilever resin-bonded glass fiber reinforced composite fixed dental prostheses: an in vitro and finite element analysis study.

    Science.gov (United States)

    Keulemans, Filip; De Jager, Niek; Kleverlaan, Cornelis J; Feilzer, Albert J

    2008-10-01

    The aim of this study was to evaluate in vitro the influence of retainer design on the strength of two-unit cantilever resin-bonded glass fiber-reinforced composite (FRC) fixed dental prostheses (FDP). Four retainer designs were tested: a proximal box, a step-box, a dual wing, and a step-box-wing. Of each design on 8 human mandibular molars, FRC-FDPs of a premolar size were produced. The FRC framework was made of resin impregnated unidirectional glass fibers (Estenia C&B EG Fiber, Kuraray) and veneered with hybrid resin composite (Estenia C&B, Kuraray). Panavia F 2.0 (Kuraray) was used as resin luting cement. FRC-FDPs were loaded to failure in a universal testing machine. One-way ANOVA and Tukey's post-hoc test were used to evaluate the data. The four designs were analyzed with finite element analysis (FEA) to reveal the stress distribution within the tooth/restoration complex. Significantly lower fracture strengths were observed with inlay-retained FDPs (proximal box: 300 +/- 65 N; step-box: 309 +/- 37 N) compared to wing-retained FDPs (p optimal design for replacement of a single premolar by means of a two-unit cantilever FRC-FDPs.

  11. Stress analysis of fuelling machine magazine housing of PHWR

    International Nuclear Information System (INIS)

    Singh, R.K.; Mehra, V.K.; Charan, J.J.; Kakodkar, A.

    1983-01-01

    PWR has fuelling machines for on-line refuelling of the core. Magazine housing of this fuelling machine is a thick pressure vessel. It has a cylindrical vessel with flat head on one side and reservable flange closure on the other side. The vessel has many small and big openings. This paper describes the two sets of experiments conducted for its stress analysis. First set of experiment was conducted on a 1:5 photoelastic model which was stress frozen under load of internal pressure. The second set of experiment involved strain gauge measurements at some important locations of the magazine housing. The paper summarises results of the experiments. In conclusion comparison is made between the experimental results and the results of finite element analysis. (orig.)

  12. Thermoelastic stress analysis system developed for industrial applications

    DEFF Research Database (Denmark)

    Haldorsen, Lars Magne

    The thesis is divided into three parts. The first part describes an extensive evaluation of the existing thermoelastic theory. The second part describes the development and results af a reliable numerical simulation code of the thermoelastic effect and the associated heat transfer effects. Finall......, theories, methods and additional equipment are developed in order to adopt a commercial IR-imaging system to preform Termoelastic Stress Analysis (TSA)....

  13. Analysis of the Citrullus colocynthis transcriptome during water deficit stress.

    Directory of Open Access Journals (Sweden)

    Zhuoyu Wang

    Full Text Available Citrullus colocynthis is a very drought tolerant species, closely related to watermelon (C. lanatus var. lanatus, an economically important cucurbit crop. Drought is a threat to plant growth and development, and the discovery of drought inducible genes with various functions is of great importance. We used high throughput mRNA Illumina sequencing technology and bioinformatic strategies to analyze the C. colocynthis leaf transcriptome under drought treatment. Leaf samples at four different time points (0, 24, 36, or 48 hours of withholding water were used for RNA extraction and Illumina sequencing. qRT-PCR of several drought responsive genes was performed to confirm the accuracy of RNA sequencing. Leaf transcriptome analysis provided the first glimpse of the drought responsive transcriptome of this unique cucurbit species. A total of 5038 full-length cDNAs were detected, with 2545 genes showing significant changes during drought stress. Principle component analysis indicated that drought was the major contributing factor regulating transcriptome changes. Up regulation of many transcription factors, stress signaling factors, detoxification genes, and genes involved in phytohormone signaling and citrulline metabolism occurred under the water deficit conditions. The C. colocynthis transcriptome data highlight the activation of a large set of drought related genes in this species, thus providing a valuable resource for future functional analysis of candidate genes in defense of drought stress.

  14. Heat Transfer and Thermal Stress Analysis of a Mandibular Molar Tooth Restored by Different Indirect Restorations Using a Three-Dimensional Finite Element Method.

    Science.gov (United States)

    Çelik Köycü, Berrak; İmirzalıoğlu, Pervin

    2017-07-01

    Daily consumption of food and drink creates rapid temperature changes in the oral cavity. Heat transfer and thermal stress caused by temperature changes in restored teeth may damage the hard and soft tissue components, resulting in restoration failure. This study evaluates the temperature distribution and related thermal stress on mandibular molar teeth restored via three indirect restorations using three-dimensional (3D) finite element analysis (FEA). A 3D finite element model was constructed of a mandibular first molar and included enamel, dentin, pulp, surrounding bone, and indirect class 2 restorations of type 2 dental gold alloy, ceramic, and composite resin. A transient thermal FEA was performed to investigate the temperature distribution and the resulting thermal stress after simulated temperature changes from 36°C to 4 or 60°C for a 2-second time period. The restoration models had similar temperature distributions at 2 seconds in both the thermal conditions. Compared with 60°C exposure, the 4°C condition resulted in thermal stress values of higher magnitudes. At 4ºC, the highest stress value observed was tensile stress (56 to 57 MPa), whereas at 60°C, the highest stress value observed was compressive stress (42 to 43 MPa). These stresses appeared at the cervical region of the lingual enamel. The thermal stress at the restoration surface and resin cement showed decreasing order of magnitude as follows: composite > gold > ceramic, in both thermal conditions. The properties of the restorative materials do not affect temperature distribution at 2 seconds in restored teeth. The pulpal temperature is below the threshold for vital pulp tissue (42ºC). Temperature changes generate maximum thermal stress at the cervical region of the enamel. With the highest thermal expansion coefficient, composite resin restorations exhibit higher stress patterns than ceramic and gold restorations. © 2015 by the American College of Prosthodontists.

  15. Structural and stress analysis of nuclear piping systems

    International Nuclear Information System (INIS)

    Hata, Hiromichi

    1982-01-01

    The design of the strength of piping system is important in plant design, and its outline on the example of PWRs is reported. The standards and guides concerning the design of the strength of piping system are shown. The design condition for the strength of piping system is determined by considering the requirements in the normal operation of plants and for the safety design of plants, and the loads in normal operation, testing, credible accident and natural environment are explained. The methods of analysis for piping system are related to the transient phenomena of fluid, piping structure and local heat conduction, and linear static analysis, linear time response analysis, nonlinear time response analysis, thermal stress analysis and fluid transient phenomenon analysis are carried out. In the aseismatic design of piping system, it is desirable to avoid the vibration together with a building supporting it, and as a rule, to make it into rigid structure. The piping system is classified into high temperature and low temperature pipings. The formulas for calculating stress and the allowable condition, the points to which attention must be paid in the design of piping strength and the matters to be investigated hereafter are described. (Kako, I.)

  16. Shaping dental contract reform: a clinical and cost-effective analysis of incentive-driven commissioning for improved oral health in primary dental care

    Science.gov (United States)

    Hulme, C; Robinson, P G; Saloniki, E C; Vinall-Collier, K; Baxter, P D; Douglas, G; Gibson, B; Godson, J H; Meads, D; Pavitt, S H

    2016-01-01

    Objective To evaluate the clinical and cost-effectiveness of a new blended dental contract incentivising improved oral health compared with a traditional dental contract based on units of dental activity (UDAs). Design Non-randomised controlled study. Setting Six UK primary care dental practices, three working under a new blended dental contract; three matched practices under a traditional contract. Participants 550 new adult patients. Interventions A new blended/incentive-driven primary care dentistry contract and service delivery model versus the traditional contract based on UDAs. Main outcome measures Primary outcome was as follows: percentage of sites with gingival bleeding on probing. Secondary outcomes were as follows: extracted and filled teeth (%), caries (International Caries Detection and Assessment System (ICDAS)), oral health-related quality of life (Oral Health Impact Profile-14 (OHIP-14)). Incremental cost-effective ratios used OHIP-14 and quality adjusted life years (QALYs) derived from the EQ-5D-3L. Results At 24 months, 291/550 (53%) patients returned for final assessment; those lost to follow-up attended 6.46 appointments on average (SD 4.80). The primary outcome favoured patients in the blended contract group. Extractions and fillings were more frequent in this group. Blended contracts were financially attractive for the dental provider but carried a higher cost for the service commissioner. Differences in generic health-related quality of life were negligible. Positive changes over time in oral health-related quality of life in both groups were statistically significant. Conclusions This is the first UK study to assess the clinical and cost-effectiveness of a blended contract in primary care dentistry. Although the primary outcome favoured the blended contract, the results are limited because 47% patients did not attend at 24 months. This is consistent with 39% of adults not being regular attenders and 27% only visiting their dentist when

  17. Analysis of health behaviour change interventions for preventing dental caries delivered in primary schools.

    Science.gov (United States)

    Adair, P M; Burnside, G; Pine, C M

    2013-01-01

    To improve oral health in children, the key behaviours (tooth brushing and sugar control) responsible for development of dental caries need to be better understood, as well as how to promote these behaviours effectively so they become habitual; and, the specific, optimal techniques to use in interventions. The aim of this paper is to describe and analyse the behaviour change techniques that have been used in primary school-based interventions to prevent dental caries (utilizing a Cochrane systematic review that we have undertaken) and to identify opportunities for improving future interventions by incorporating a comprehensive range of behaviour change techniques. Papers of five interventions were reviewed and data were independently extracted. Results indicate that behaviour change techniques were limited to information-behaviour links, information on consequences, instruction and demonstration of behaviours. None of the interventions were based on behaviour change theory. We conclude that behaviour change techniques used in school interventions to reduce dental caries were limited and focused around providing information about how behaviour impacts on health and the consequences of not developing the correct health behaviours as well as providing oral hygiene instruction. Establishing which techniques are effective is difficult due to poor reporting of interventions in studies. Future design of oral health promotion interventions using behaviour change theory for development and evaluation (and reporting results in academic journals) could strengthen the potential for efficacy and provide a framework to use a much wider range of behaviour change techniques. Future studies should include development and publication of intervention manuals which is becoming standard practice in other health promoting programmes. © 2013 S. Karger AG, Basel.

  18. Analysis of the spatial rates dose rates during dental panoramic radiography

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Jong Kyung [Dept. of Radiation Safety Management Commission, Daegu Health College, Daegu (Korea, Republic of); Park, Myeong Hwan [Dept. of Radiologic Technology, Daegu Health College, Daegu (Korea, Republic of); Kim, Yong Min [Dept. of Radiological Science, Catholic University of Daegu, Daegu (Korea, Republic of)

    2016-12-15

    A dental panoramic radiography which usually uses low level X-rays is subject to the Nuclear Safety Act when it is installed for the purpose of education. This paper measures radiation dose and spatial dose rate by usage and thereby aims to verify the effectiveness of radiation safety equipment and provide basic information for radiation safety of radiation workers and students. After glass dosimeter (GD-352M) is attached to direct exposure area, the teeth, and indirect exposure area, the eye lens and the thyroid, on the dental radiography head phantom, these exposure areas are measured. Then, after dividing the horizontal into a 45°, it is separated into seven directions which all includes 30, 60, 90, 120 cm distance. The paper shows that the spatial dose rate is the highest at 30 cm and declines as the distance increases. At 30 cm, the spatial dose rate around the starting area of rotation is 3,840 μSv/h, which is four times higher than the lowest level 778 μSv/h. Furthermore, the spatial dose rate was 408 μSv/h on average at the distance of 60 cm where radiation workers can be located. From a conservative point of view, It is possible to avoid needless exposure to radiation for the purpose of education. However, in case that an unintended exposure to radiation happens within a radiation controlled area, it is still necessary to educate radiation safety. But according to the current Medical Service Act, in medical institutions, even if they are not installed, the equipment such as interlock are obliged by the Nuclear Safety Law, considering that the spatial dose rate of the educational dental panoramic radiography room is low. It seems to be excessive regulation.

  19. In silico analysis of the competition between Streptococcus sanguinis and Streptococcus mutans in the dental biofilm.

    Science.gov (United States)

    Valdebenito, B; Tullume-Vergara, P O; González, W; Kreth, J; Giacaman, R A

    2018-04-01

    During dental caries, the dental biofilm modifies the composition of the hundreds of involved bacterial species. Changing environmental conditions influence competition. A pertinent model to exemplify the complex interplay of the microorganisms in the human dental biofilm is the competition between Streptococcus sanguinis and Streptococcus mutans. It has been reported that children and adults harbor greater numbers of S. sanguinis in the oral cavity, associated with caries-free teeth. Conversely, S. mutans is predominant in individuals with a high number of carious lesions. Competition between both microorganisms stems from the production of H 2 O 2 by S. sanguinis and mutacins, a type of bacteriocins, by S. mutans. There is limited evidence on how S. sanguinis survives its own H 2 O 2 levels, or if it has other mechanisms that might aid in the competition against S. mutans, nonetheless. We performed a genomic and metabolic pathway comparison, coupled with a comprehensive literature review, to better understand the competition between these two species. Results indicated that S. sanguinis can outcompete S. mutans by the production of an enzyme capable of metabolizing H 2 O 2 . S. mutans, however, lacks the enzyme and is susceptible to the peroxide from S. sanguinis. In addition, S. sanguinis can generate energy through gluconeogenesis and seems to have evolved different communication mechanisms, indicating that novel proteins may be responsible for intra-species communication. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  20. Retrospective analysis of dental implants placed and restored by advanced prosthodontic residents.

    Science.gov (United States)

    Barias, Pamela A; Lee, Damian J; Yuan, Judy Chia-Chun; Sukotjo, Cortino; Campbell, Stephen D; Knoernschild, Kent L

    2013-02-01

    The purposes of this retrospective clinical review were to: (1) describe the demographics of implant patients, types of implant treatment and implant-supported prostheses in an Advanced Education in Prosthodontic Program, (2) evaluate the survival rate of dental implants placed by prosthodontic residents from 2006 to 2008, and (3) analyze the relationship between resident year of training and implant survival rate. All patients who received dental implants placed by prosthodontic residents from January 2006 to October of 2008 in the Advanced Prosthodontic Program at the University of Illinois at Chicago College of Dentistry were selected for this study. Age, gender, implant diameter, length, implant locations, surgical and restorative detail, and year of prosthodontic residency training were collected and analyzed. Life-table and Kaplan-Meier survival analyses were performed based on implants overall, locations, year of training, and use of a computer-generated surgical guide. A Logrank statistic was performed between implant survival and year of prosthodontic residency training, location, and use of computer-generated surgical guide (α= 0.05). Three hundred and six implants were placed, and of these, seven failed. Life-table and Kaplan-Meier analyses computed a cumulative survival rate (CSR) of 97% for overall implants and implants placed with a computer-generated surgical guide. No statistical difference was found in implant survival rates as a function of year of training (P= 0.85). Dental implants placed by prosthodontic residents had a CSR comparable to previously published studies by other specialties. The year of prosthodontic residency training and implant failure rate did not have any significant relationship. © 2012 by the American College of Prosthodontists.

  1. A cumulative analysis of odontogenic cysts from major dental institutions of Bangalore city: A study of 252 cases.

    Science.gov (United States)

    Ramachandra, Prashanth; Maligi, Prathima; Raghuveer, Hp

    2011-01-01

    The objective of this study was to perform a cumulative analysis of odontogenic cysts obtained from the data of major dental institutions of Bangalore city, as well as to evaluate their distribution during a 5-year period and compare the results with other international studies. Data for the study were obtained from the reports of patients diagnosed with odontogenic cysts between 2005 and 2010 from different dental institutions of Bangalore. Case records of patients that fit the histological classification of the World Health Organization (WHO) (2005) were included in the study and the following variables were analyzed: age, gender, anatomic location, and histological type. In a total of 252 cyst specimens diagnosed, 79.76% were odontogenic cysts and 20.24% were nonodontogenic cysts. Among the odontogenic cysts most frequent lesions were radicular cysts (50.25%), followed by keratocysts (27.36%) and dentigerous cysts (22.39%). Our study provides a cumulative data of odontogenic cysts in the population of Bangalore city. The results of our study showed a similar frequency of odontogenic cysts as compared to other populations of the world, with radicular cyst being identified as the most frequent odontogenic cyst. Keratocyst was the second most common cyst followed by dentigerous cyst.

  2. Significant improvement of the osseointegration of zirconia dental implants by HS-LEIS analysis

    International Nuclear Information System (INIS)

    Beekmans, H.; Breitenstein, D.; Brongersma, H.H.; Ridder, M. de; Tromp, Th.J.

    2010-01-01

    The use of sintered yttria stabilized zirconia dental implants is a recent development. After initial successes with these new implants a pattern of erratic results emerged. Reliable osseointegration would not always occur. High-sensitivity low energy ion scattering (HS-LEIS) is used to investigate both virgin and rejected implants. The surfaces of the implant are found to be covered with both an organic and inorganic contamination layer. Sterilization does not remove this contamination. Using LEIS as analytic tool a new cleaning process has been developed. Since this cleaning process is in use, the failure rate has dropped to a very low value.

  3. Structural Stress Analysis of an Engine Cylinder Head

    Directory of Open Access Journals (Sweden)

    R. Tichánek

    2005-01-01

    Full Text Available This paper deals with a structural stress analysis of the cylinder head assembly of the C/28 series engine. A detailed FE model was created for this purpose. The FE model consists of the main parts of the cylinder head assembly, and it includes a description of the thermal and mechanical loads and the contact interaction between their parts. The model considers the temperature dependency of the heat transfer coefficient on wall temperature in cooling passages. The paper presents a comparison of computed and measured temperature. The analysis was carried out using the FE program ABAQUS. 

  4. Residual stress analysis on materials with steep stress gradient by using X-ray incidence at higher angles

    International Nuclear Information System (INIS)

    Ohya, Shin-ichi; Yoshioka, Yasuo; Maeno, Shigeki

    1996-01-01

    X-ray stress measurements for isotropic polycrystalline are materials are usually carried out by the sin 2 ψ method under the assumption of no stress gradient in X-ray penetration depth. When a steep stress gradient exists in the vicinity of surface layer, however, non-linear sin 2 ψ relation is observed and the sin 2 ψ method cannot be applied on such cases. Although several X-ray stress analyzers have been developed for materials with steep stress gradient in the surface layer, it is desirable to use diffraction data at higher incident angles of ψ 0 as possible as close on 90 degrees in order to determine the both values of surface stress and stress gradient with high accuracy. In the present study, an X-ray stress analyzer based on Ω geometry was fabricated to enable X-ray incidence at higher angle of ψ 0 . The X-ray detector was positioned on -η side against X-ray incident beam. Both of the residual surface stress and stress gradient were determined by use of the COSψ method on shot-peened steel and silicon nitride specimens. This prototype stress analyzer was found effective to perform a biaxial or triaxial stress analysis. (author)

  5. Comparative photoelastic study of dental and skeletal anchorages in the canine retraction

    Directory of Open Access Journals (Sweden)

    Cristiane Aparecida de Assis Claro

    2014-01-01

    Full Text Available OBJECTIVE: To compare dental and skeletal anchorages in mandibular canine retraction by means of a stress distribution analysis. METHODS: A photoelastic model was produced from second molar to canine, without the first premolar, and mandibular canine retraction was simulated by a rubber band tied to two types of anchorage: dental anchorage, in the first molar attached to adjacent teeth, and skeletal anchorage with a hook simulating the mini-implant. The forces were applied 10 times and observed in a circular polariscope. The stresses located in the mandibular canine were recorded in 7 regions. The Mann-Whitney test was employed to compare the stress in each region and between both anchorage systems. The stresses in the mandibular canine periradicular regions were compared by the Kruskal-Wallis test. RESULTS: Stresses were similar in the cervical region and the middle third. In the apical third, the stresses associated with skeletal anchorage were higher than the stresses associated with dental anchorage. The results of the Kruskal-Wallis test showed that the highest stresses were identified in the cervical-distal, apical-distal, and apex regions with the use of dental anchorage, and in the apical-distal, apical-mesial, cervical-distal, and apex regions with the use of skeletal anchorage. CONCLUSIONS: The use of skeletal anchorage in canine retraction caused greater stress in the apical third than the use of dental anchorage, which indicates an intrusive component resulting from the direction of the force due to the position of the mini-implant and the bracket hook of the canine.

  6. Assessment of Oral Status in Pediatric Patients with Special Health Care Needs receiving Dental Rehabilitation Procedures under General Anesthesia: A Retrospective Analysis.

    Science.gov (United States)

    Solanki, Neeraj; Kumar, Anuj; Awasthi, Neha; Kundu, Anjali; Mathur, Suveet; Bidhumadhav, Suresh

    2016-06-01

    Dental problems serve as additional burden on the children with special health care needs (CSHCN) because of additional hospitalization pressure, they face for the treatment of various serious medical problems. These patients have higher incidence of dental caries due to increased quantity of sugar involved in the drug therapies and lower salivary flow in the oral cavity. Such patients are difficult to treat with local anesthesia or inhaled sedatives. Single-sitting dental treatment is possible in these patients with general anesthesia. Therefore, we conducted this retrospective analysis of oral health status of CSHCN receiving various dental treatments in a given population. A total of 200 CSHCN of age 14 years or less reporting in the pediatric wing of the general hospital from 2005 to 2014 that underwent comprehensive dental treatment under general anesthesia were included in the study. Patients with history of any additional systemic illness, any malignancy, any known drug allergy, or previous history of any dental treatment were excluded from the study. Complete mouth rehabilitation was done in these patients under general anesthesia following standard protocols. Data regarding the patient's disability, type, duration, and severity of disability was collected and analyzed. All the results were analyzed by Statistical Package for the Social Sciences (SPSS) software. Chi-square test, Student's t-test, and one-way analysis of variance were used to assess the level of significance. Statistically significant results were obtained while analyzing the subject's decayed missing filled/decayed extracted filled teeth indices divided based on age. Significant difference was observed only in cases where patients underwent complete crown placement even when divided based on type of disability. While analyzing the prevalence, statistically significant results were observed in patients when divided based on their age. In CSHCN, dental pathologies and caries indices are

  7. Research in a dental practice setting.

    Science.gov (United States)

    Fardal, Oystein

    2004-09-01

    There is a shortage of research from dental practice. The aim of this article is to stimulate more interest in dental research. This is done by explaining the basic principles of doing research in a dental practice setting. Examples are taken from the author's own practice. Emphasis is placed on the following points: how to develop and research ideas; factors specific to dental practice; how articles and journals are rated; making a protocol for the study; examiners' reliability and statistical analysis.

  8. Dental OCT

    Science.gov (United States)

    Wilder-Smith, Petra; Otis, Linda; Zhang, Jun; Chen, Zhongping

    This chapter describes the applications of OCT for imaging in vivo dental and oral tissue. The oral cavity is a diverse environment that includes oral mucosa, gingival tissues, teeth and their supporting structures. Because OCT can image both hard and soft tissues of the oral cavity at high resolution, it offers the unique capacity to identity dental disease before destructive changes have progressed. OCT images depict clinically important anatomical features such as the location of soft tissue attachments, morphological changes in gingival tissue, tooth decay, enamel thickness and decay, as well as the structural integrity of dental restorations. OCT imaging allows for earlier intervention than is possible with current diagnostic modalities.

  9. Fighting for territories: time-lapse analysis of dental pulp and dental follicle stem cells in co-culture reveals specific migratory capabilities

    Directory of Open Access Journals (Sweden)

    C Schiraldi

    2012-11-01

    Full Text Available Stem cell migration is a critical step during the repair of damaged tissues. In order to achieve appropriate cell-based therapies for tooth and periodontal ligament repair it is necessary first to understand the dynamics of tissue-specific stem cell populations such as dental pulp stem cells (DPSC and dental follicle stem cells (DFSC. Using time-lapse imaging, we analysed migratory and proliferative capabilities of these two human stem cell lines in vitro. When cultured alone, both DPSC and DFSC exhibited low and irregular migration profiles. In co-cultures, DFSC, but not DPSC, spectacularly increased their migration activity and velocity. DFSC rapidly surrounded the DPSC, thus resembling the in vivo developmental process, where follicle cells encircle both dental epithelium and pulp. Cell morphology was dependent on the culture conditions (mono-culture or co-culture and changed over time. Regulatory genes involved in dental cell migration and differentiation such as TWIST1, MSX1, RUNX2, SFRP1 and ADAM28, were also evaluated in co-cultures. MSX1 up-regulation indicates that DPSC and DFSC retain their odontogenic potential. However, DPSC lose their capacity to differentiate into odontoblasts in the presence of DFSC, as suggested by RUNX2 up-regulation and TWIST1 down-