[Anniversaries of the foundation of the dental clinics. II. The dental clinics at the Mikszáth Kálmán Square in Budapest, Hungary].

Science.gov (United States)

Kóbor, András

2010-03-01

After 1952 the building of the Department of Stomatology was no more able to fulfill the increased demands, when the independent dental education had been started at the Medical University of Budapest. The leadership of the new Dental Faculty--officially founded in 1955--was looking for a solution to find a new building for clinical purposes. Finally in 1959 the new dental departments moved to a once residential building at Mikszáth Kálmán Square converted into dental clinics. This site had been in operation until the opening of the New Dental Education Center in 2007.

Clinical anxiety among final year dental students: The trainers and students perspectives

Directory of Open Access Journals (Sweden)

A Obarisiagbon

2013-01-01

Full Text Available Background: The dental clinical setting, which is a significant learning environment for undergraduate dental students, may induce anxiety, which may adversely affect the clinical performance. The purpose of this cross-sectional study was to determine the factors provoking clinical anxiety in dental students from the trainers and students perspectives. Materials and Methods: This cross-sectional study was conducted among 6 th (final year dental students of University of Benin and their clinical trainers between January and March 2012 using the 38-item modified Moss and McManus clinical anxiety questionnaire. Results: Of the 67 participants, 32 (47.8% were 6 th year dental students while 35 (52.2% were clinical trainers. According to the students, the top clinical anxiety provoking situations were inability to meet requirements before exams, inability to pass the final exams, dealing with psychiatric patients, coping with uncooperative children, getting infected by patients, fracturing a tooth during extraction, extracting the wrong tooth, discovering calculus by the supervisor after scaling, accidental pulp exposure, inadvertently hurting patients and using the high speed hand piece. There existed concordance on the top two clinical anxiety provoking situations reported by the students and their clinical trainers. However, measuring blood pressure, taking pulse, presenting in the clinic, handling a syncopal attack, and accidental pulp exposure were statistically significant contrasting clinical anxiety provoking situations from dental students and trainers perspectives. Conclusion: Data from this study revealed that clinical trainers share largely the same perspectives with the dental students on the clinical anxiety provoking situations with slight variations. Fostering a supportive learning environment conducive to dental student learning by strengthen efforts to minimize clinical anxiety is a necessity.

Evaluation of radiological service of Dental Clinic, Uberlandia Federal University (MG-Brazil)

International Nuclear Information System (INIS)

Vieira, C.D.V.T.

1985-01-01

The management related problems and the quality of dental radiographs of the Radiographic Service of the Dental Clinic, Uberlandia Federal University (MG-Brazil) are evaluated. The results are based on the examinations of 404 dental files from patients atending the Dental Clinic in 1983. Frequency distribution, mean and percentages were computed for the variables studied. (M.A.C.) [pt

Campus-Based, Community-Based, and Philanthropic Contributions to Predoctoral Pediatric Dental Clinical Education: Two Years of Experiences at One Dental College.

Science.gov (United States)

Spiritoso, Stephen; Gross, Erin; Bean, Canise Y; Casamassimo, Paul S; Levings, Kevin; Lloyd, Patrick

2015-08-01

The aim of this study was to investigate the contribution of a tiered predoctoral pediatric dentistry clinical education model to competency achievement by dental students over a two-year clinical education. Retrospective data were obtained for academic years 2012-13 and 2013-14 from three sources: a campus-based, dental school-housed clinic; division-directed clinics in community-based pediatric and special needs clinics (DDC); and clinics affiliated with the dental college's community-based dental education (CBDE) program, the OHIO Project (OP). A fourth dataset was obtained for the same two-year period from a biannual clinic event held at the college in conjunction with Give Kids a Smile Day (GKAS). Procedures considered essential to the care of children were sorted by 12 dental codes from all services for patients 18 years of age and younger. The dental school clinic provided 11,060 procedures; the DDC, 28,462; the OP, 17,863; and GKAS, 2,028. The two-year total was 59,433 procedures. Numbers of diagnostic and preventive procedures were 19,441, restorative procedures were 13,958, and pulp and surgical procedures were 7,392. Site contribution ranged from 52.2 to 144.9 procedures per attending student, with the DDC yielding the highest per student average for each year (126.4 and 144.9) and the dental school clinic the lowest (52.2 and 53.1). This study found that a combination of school-based, community-based, and philanthropic pediatric dental experiences offered a large number of essential pediatric dentistry experiences for predoctoral dental students, with CBDE opportunities offering the largest contribution.

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.

Switching Performance Evaluation of Commercial SiC Power Devices (SiC JFET and SiC MOSFET) in Relation to the Gate Driver Complexity

DEFF Research Database (Denmark)

Pittini, Riccardo; Zhang, Zhe; Andersen, Michael A. E.

2013-01-01

and JFETs. The recent introduction of SiC MOSFET has proved that it is possible to have highly performing SiC devices with a minimum gate driver complexity; this made SiC power devices even more attractive despite their device cost. This paper presents an analysis based on experimental results...... of the switching losses of various commercially available Si and SiC power devices rated at 1200 V (Si IGBTs, SiC JFETs and SiC MOSFETs). The comparison evaluates the reduction of the switching losses which is achievable with the introduction of SiC power devices; this includes analysis and considerations...

Inequalities of caries experience in Nevada youth expressed by DMFT index vs. Significant Caries Index (SiC) over time.

Science.gov (United States)

Ditmyer, Marcia; Dounis, Georgia; Mobley, Connie; Schwarz, Eli

2011-04-05

With the increasingly polarized distribution of dental caries among children and adolescents, the usual DMFT measure has become a less meaningful population descriptor. To re-focus on identifying the high caries prevalence group the Significant Caries Index (SiC) was created. The aims of this study were to analyze the prevalence and severity of dental caries in Nevada youth over a period of eight years and to compare its expression by means of DMFT and SiC; analyze the caries trends in the population and their underlying factors, and determine whether Nevada youth were at risk for significantly high levels of dental caries. Retrospective data was analyzed from a series of sequential, standardized oral health surveys across eight years (2001/2002-2008/2009) that included over 62,000 examinations of adolescents 13-19 years of age, attending public/private Nevada schools. Mean Decayed-Missing-Filled Teeth index (DMFT) and Significant Caries Index (SiC) were subsequently computed for each academic year. Descriptive statistics were reported for analysis of comparative DMFT and SiC scores in relation to age, gender, racial background, and residence in a fluoridated/non-fluoridated community. Logistic regression analysis was used to analyze the differential impact of the variables on the probability of being in the high caries prevalence group. Comparison of students' mean DMFT to National (NHANES) data confirmed that dental caries remains a common chronic disease among Nevada youth, presenting higher prevalence rates and greater mean scores than the national averages. Downward trends were found across all demographics compared between survey years 1 and 6 with the exception of survey year 3. An upward trend began in survey year six. Over time, the younger group displayed an increasing proportion of caries free individuals while a decreasing proportion was found among older examinees. As expected, the mean SiC score was significantly higher than DMFT scores within each

Psychosocial Aspects of Dental Anxiety and Clinical Pain Phenomena

DEFF Research Database (Denmark)

Moore, Rod

This Danish Doctoral Dissertation in the science of Odontology contains 7 chapters: 1) Introduction to a social perspective on dental treatment, anxiety and pain throughout time, 2) research models and methods to study dental anxiety and clinical pain phenomena, 3) the fear of dental treatment...... .. what it is and what it is not and how many have it, 4) clinical pain treatment, psychosocial aspects in relation to anxiety, 4) patients and dentists' roles, pain perception and anxiety, 6) psychosocial aspects of managing anxiety and pain phenomena, and 7) Conclusions and proposals for the future...

Infections Disease in the Dental Clinical Nigerian Dentists ...

African Journals Online (AJOL)

The dental clinic is a potential source of transmission of infectious disease due to the invasive nature of many dental procedures. Infectious disease therefore constitutes serious occupational hazards to all oral health care workers. This descriptive study aims to assess the knowledge of dentists on common transmissible ...

Clinical implication of blood glucose monitoring in general dental offices: the Ehime Dental Diabetes Study

OpenAIRE

Harase, Tadahiro; Nishida, Wataru; Hamakawa, Tomohiro; Hino, Satoshi; Shigematsu, Kenji; Kobayashi, Satoru; Sako, Hirofumi; Ito, Shirou; Murakami, Hajime; Nishida, Kei; Inoue, Hiroshi; Fujisawa, Masahito; Yoshizu, Hiroshi; Kawamura, Ryoichi; Takata, Yasunori

2015-01-01

Objective We examined whether general dentists can contribute to the detection of patients with undiagnosed diabetes and prediabetes by monitoring blood glucose in dental clinics. Research design and methods A total of 716 patients who visited clinics for dental treatment were enrolled and classified into 3 groups (mild, moderate, and severe) according to Kornman's criteria for periodontitis. The correlations between the casual blood glucose level, presence or absence of the history of diabet...

A survey of dental treatment under general anesthesia in a Korean university hospital pediatric dental clinic.

Science.gov (United States)

Shin, Bisol; Yoo, Seunghoon; Kim, Jongsoo; Kim, Seungoh; Kim, Jongbin

2016-09-01

In South Korea, the number of cases of dental treatment for the disabled is gradually increasing, primarily at regional dental clinics for the disabled. This study investigated pediatric patients at a treatment clinic for the disabled within a university hospital who received dental treatment under general anesthesia. This data could assist those that provide dental treatment for the disabled and guide future treatment directions and new policies. This study was a retrospective analysis of 263 cases in which patients received dental treatment under general anesthesia from January 2011 to May 2016. The variables examined were gender, age, reason for anesthesia, type of disability, time under anesthesia, duration of treatment, type of procedure, treatment details, and annual trends in the use of general anesthesia. Among pediatric patients with disabilities who received dental treatment under general anesthesia, the most prevalent age group was 5-8 years old (124 patients, 47.1%), and the primary reason for administering anesthesia was dental anxiety or phobia. The mean time under anesthesia was 132.7 ± 77.6 min, and the mean duration of treatment was 101.9 ± 71.2 min. The most common type of treatment was restoration, accounting for 158 of the 380 treatments performed. Due to increasing demand, the number of cases of dental treatment performed under general anesthesia is expected to continue increasing, and it can be a useful method of treatment in patients with dental anxiety or phobia.

A questionnaire study regarding local anesthesia in dentistry and safety measures in dental clinics among dental students

OpenAIRE

オオケ, ハナコ; クドウ, マサル; シンヤ, ノボル; Hanako, OHKE; Masaru, KUDO; Noboru, SHINYA

2005-01-01

This reports the results of a questionnaire study of dental students on the awareness of "local anesthesia" and "use of patient monitoring systems" in dental clinics. Subjects participated in the present study included 96 sixth year dental students (D6) and 93 first year dental students (D1). The results indicate that the majority of respondents including both D6 and D1 support the notion that a "dentist" is the most suitable person to perform local anesthesia in dental treatment. With respec...

Clinical image quality evaluation for panoramic radiography in Korean dental clinics

International Nuclear Information System (INIS)

Choi, Bo Ram; Choi, Da Hye; Huh, Kyung Hoe; Yi, Won Jin; Heo, Min Suk; Choi, Soon Chul; Bae, Kwang Hak; Lee, Sam Sun

2012-01-01

The purpose of this study was to investigate the level of clinical image quality of panoramic radiographs and to analyze the parameters that influence the overall image quality. Korean dental clinics were asked to provide three randomly selected panoramic radiographs. An oral and maxillofacial radiology specialist evaluated those images using our self-developed Clinical Image Quality Evaluation Chart. Three evaluators classified the overall image quality of the panoramic radiographs and evaluated the causes of imaging errors. A total of 297 panoramic radiographs were collected from 99 dental hospitals and clinics. The mean of the scores according to the Clinical Image Quality Evaluation Chart was 79.9. In the classification of the overall image quality, 17 images were deemed 'optimal for obtaining diagnostic information,' 153 were 'adequate for diagnosis,' 109 were 'poor but diagnosable,' and nine were 'unrecognizable and too poor for diagnosis'. The results of the analysis of the causes of the errors in all the images are as follows: 139 errors in the positioning, 135 in the processing, 50 from the radiographic unit, and 13 due to anatomic abnormality. Panoramic radiographs taken at local dental clinics generally have a normal or higher-level image quality. Principal factors affecting image quality were positioning of the patient and image density, sharpness, and contrast. Therefore, when images are taken, the patient position should be adjusted with great care. Also, standardizing objective criteria of image density, sharpness, and contrast is required to evaluate image quality effectively.

Measuring patient safety in a UK dental hospital: development of a dental clinical effectiveness dashboard.

Science.gov (United States)

Pemberton, M N; Ashley, M P; Shaw, A; Dickson, S; Saksena, A

2014-10-01

Patient safety is an important marker of quality for any healthcare organisation. In 2008, the British Government white paper entitled High quality care for all, resulting from a review led by Lord Darzi, identified patient safety as a key component of quality and discussed how it might be measured, analysed and acted upon. National and local clinically curated metrics were suggested, which could be displayed via a 'clinical dashboard'. This paper explains the development of a clinical effectiveness dashboard focused on patient safety in an English dental hospital and how it has helped us identify relevant patient safety issues in secondary dental care.

A Comparison of Urban School- and Community-Based Dental Clinics

Science.gov (United States)

Larsen, Charles D.; Larsen, Michael D.; Handwerker, Lisa B.; Kim, Maile S.; Rosenthal, Murray

2009-01-01

Background: The objective of the study was to quantitatively compare school- and community-based dental clinics in New York City that provide dental services to children in need. It was hypothesized that the school-based clinics would perform better in terms of several measures. Methods: We reviewed billing and visit data derived from encounter…

Palladium transport in SiC

International Nuclear Information System (INIS)

Olivier, E.J.; Neethling, J.H.

2012-01-01

Highlights: ► We investigate the reaction of Pd with SiC at typical HTGR operating temperatures. ► The high temperature mobility of palladium silicides within polycrystalline SiC was studied. ► Corrosion of SiC by Pd was seen in all cases. ► The preferential corrosion and penetration of Pd along grain boundaries in SiC was found. ► The penetration and transport of palladium silicides in SiC along grain boundaries was found. - Abstract: This paper reports on a transmission electron microscopy (TEM) and scanning electron microscopy (SEM) study of Pd corroded SiC. The reaction of Pd with different types of SiC at typical HTGR operating temperatures was examined. In addition the high temperature mobility of palladium silicides within polycrystalline SiC was investigated. The results indicated corrosion of the SiC by Pd in all cases studied. The corrosion leads to the formation of palladium silicides within the SiC, with the predominant phase found being Pd 2 Si. Evidence for the preferential corrosion and penetration of Pd along grain boundaries in polycrystalline SiC was found. The penetration and transport, without significant corrosion, of palladium silicides into polycrystalline SiC along grain boundaries was also observed. Implications of the findings with reference to the use of Tri Isotropic particles in HTGRs will be discussed.

Clinical image quality evaluation for panoramic radiography in Korean dental clinics

Energy Technology Data Exchange (ETDEWEB)

Choi, Bo Ram; Choi, Da Hye; Huh, Kyung Hoe; Yi, Won Jin; Heo, Min Suk; Choi, Soon Chul; Bae, Kwang Hak; Lee, Sam Sun [School of Dentistry, Seoul National University, Seoul (Korea, Republic of)

2012-09-15

The purpose of this study was to investigate the level of clinical image quality of panoramic radiographs and to analyze the parameters that influence the overall image quality. Korean dental clinics were asked to provide three randomly selected panoramic radiographs. An oral and maxillofacial radiology specialist evaluated those images using our self-developed Clinical Image Quality Evaluation Chart. Three evaluators classified the overall image quality of the panoramic radiographs and evaluated the causes of imaging errors. A total of 297 panoramic radiographs were collected from 99 dental hospitals and clinics. The mean of the scores according to the Clinical Image Quality Evaluation Chart was 79.9. In the classification of the overall image quality, 17 images were deemed 'optimal for obtaining diagnostic information,' 153 were 'adequate for diagnosis,' 109 were 'poor but diagnosable,' and nine were 'unrecognizable and too poor for diagnosis'. The results of the analysis of the causes of the errors in all the images are as follows: 139 errors in the positioning, 135 in the processing, 50 from the radiographic unit, and 13 due to anatomic abnormality. Panoramic radiographs taken at local dental clinics generally have a normal or higher-level image quality. Principal factors affecting image quality were positioning of the patient and image density, sharpness, and contrast. Therefore, when images are taken, the patient position should be adjusted with great care. Also, standardizing objective criteria of image density, sharpness, and contrast is required to evaluate image quality effectively.

Nigerian Dental Students' Assessment of their Clinical Learning ...

African Journals Online (AJOL)

Clinical learning in medical and dental education provides students with ... clinical learning opportunities and environment, level of patient care experience and ... the stress of fulfilling procedural requirements were identified as weaknesses of ...

Fluorescence properties of human teeth and dental calculus for clinical applications

Science.gov (United States)

Lee, Yong-Keun

2015-04-01

Fluorescent emission of human teeth and dental calculus is important for the esthetic rehabilitation of teeth, diagnosis of dental caries, and detection of dental calculus. The purposes of this review were to summarize the fluorescence and phosphorescence of human teeth by ambient ultraviolet (UV) light, to investigate the clinically relevant fluorescence measurement methods in dentistry, and to review the fluorescence of teeth and dental calculus by specific wavelength light. Dentine was three times more phosphorescent than enamel. When exposed to light sources containing UV components, the fluorescence of human teeth gives them the quality of vitality, and fluorescent emission with a peak of 440 nm is observed. Esthetic restorative materials should have fluorescence properties similar to those of natural teeth. Based on the fluorescence of teeth and restorative materials as determined with a spectrophotometer, a fluorescence parameter was defined. As to the fluorescence spectra by a specific wavelength, varied wavelengths were investigated for clinical applications, and several methods for the diagnosis of dental caries and the detection of dental calculus were developed. Since fluorescent properties of dental hard tissues have been used and would be expanded in diverse fields of clinical practice, these properties should be investigated further, embracing newly developed optical techniques.

Palladium transport in SiC

Energy Technology Data Exchange (ETDEWEB)

Olivier, E.J., E-mail: jolivier@nmmu.ac.za [Centre for High Resolution Transmission Electron Microscopy, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Neethling, J.H. [Centre for High Resolution Transmission Electron Microscopy, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

2012-03-15

Highlights: Black-Right-Pointing-Pointer We investigate the reaction of Pd with SiC at typical HTGR operating temperatures. Black-Right-Pointing-Pointer The high temperature mobility of palladium silicides within polycrystalline SiC was studied. Black-Right-Pointing-Pointer Corrosion of SiC by Pd was seen in all cases. Black-Right-Pointing-Pointer The preferential corrosion and penetration of Pd along grain boundaries in SiC was found. Black-Right-Pointing-Pointer The penetration and transport of palladium silicides in SiC along grain boundaries was found. - Abstract: This paper reports on a transmission electron microscopy (TEM) and scanning electron microscopy (SEM) study of Pd corroded SiC. The reaction of Pd with different types of SiC at typical HTGR operating temperatures was examined. In addition the high temperature mobility of palladium silicides within polycrystalline SiC was investigated. The results indicated corrosion of the SiC by Pd in all cases studied. The corrosion leads to the formation of palladium silicides within the SiC, with the predominant phase found being Pd{sub 2}Si. Evidence for the preferential corrosion and penetration of Pd along grain boundaries in polycrystalline SiC was found. The penetration and transport, without significant corrosion, of palladium silicides into polycrystalline SiC along grain boundaries was also observed. Implications of the findings with reference to the use of Tri Isotropic particles in HTGRs will be discussed.

Identifying and preparing the next generation of part-time clinical teachers from dental practice.

Science.gov (United States)

Radford, D R; Hellyer, P; Meakin, N; Jones, K A

2015-10-09

Part-time general dental practitioners (GDPs) and dental care professionals (DCPs) working in practice are being increasingly utilised to deliver undergraduate clinical dental education to both dental and hygiene/therapy students. As such, there is a need for appropriate recruitment processes and ongoing staff development in the different and complex role of the clinical teacher. Recently a group of experienced dental practitioners, making a journey from GDP to part-time clinical teacher, identified common themes, experiences, challenges and realisations. These were: 'what is clinical dental education?'; 'me as a clinical teacher'; and 'specific teaching issues'. The themes highlighted the complexity of dental education and the different environment of the teaching clinic from general practice. Some of the themes identified could be a starting point for the induction process to facilitate an easier transition from experienced GDP to clinical teacher. With the current demands from both students and patients alike, the 'three way dynamic of patient, student and teacher' needs to be supported if dental schools are to attract and develop the highest quality clinical teachers. It is of critical importance to give an exceptional experience to students in their clinical education as well as to patients in terms of excellent and appropriate treatment. The challenge for deans and directors of education is to find the resources to properly fund teacher recruitment, induction and the development of part-time GDPs in order to produce the expert teachers of tomorrow.

Clinical experiences of undergraduate dental students in pediatric dentistry at Cork University Dental School and Hospital, Ireland.

LENUS (Irish Health Repository)

Stewart, Christopher J

2010-03-01

The objectives of this study were to evaluate the number and range of clinical procedures completed by undergraduate dental students in pediatric dentistry in Cork University Dental School and Hospital, Ireland, and to compare the number of procedures undertaken with the subsequent examination scores. The work comprised a retrospective audit of clinical logbooks for all of the undergraduate dental students in one cohort through their fourth and fifth clinical years between 2004 and 2006. Thirty-four quantitative logbooks were audited. Students had seen a total of 1,031 patients, and each student had completed a full course of dental treatment for an average of twenty-two children. Students completed means of 30.2 restorative procedures for children, fourteen in deciduous dentition (range six to twenty-eight), and seventeen in permanent dentition (range seven to twenty-eight). Continuity of education and care (measured through children having their treatment fully completed by the same student) was 72 percent. A moderate positive correlation between levels of clinical experience and exam score was identified. All students gained experience in management of child patients with students providing care for an average of thirty children and a minimum of nineteen.

Assessment of blinding success among dental implant clinical trials: A systematic review

Directory of Open Access Journals (Sweden)

Jafar Kolahi

2015-01-01

Full Text Available Introduction: It is widely believed that blinding is a cornerstone of randomized clinical trials and that significant bias may result from unsuccessful blinding. However, it is not enough to claim that a clinical trial is single- or double-blinded and that assessment of the success of blinding is ideal. The aim of this study was to evaluate the prevalence of assessment of blinding success among dental implant clinical trials and to introduce methods of blinding assessment to the implant research community. Methods: In November 2014, PubMed was searched by blinded and experienced researchers with the query "implant AND (blindFNx01 OR maskFNx01" using the following filters: (1 Article type: clinical trial; (2 Journal categories: dental journals; (3 Field: title/abstract. Consequently, title/abstract was reviewed in all relevant articles to find any attempt to assess the success of blinding in dental implant clinical trials. Results: The PubMed search results yielded 86 clinical trials. The point of interest is that when "blindFNx01 OR maskFNx01" was deleted from the query, the number of results increased to 1688 clinical trials. This shows that only 5% of dental implant clinical trials tried to use blinding. Disappointingly, we could not find any dental implant clinical trial reporting any attempt to assess the success of blinding. Conclusion: The current status of turning a blind eye to unblinding in dental implant clinical trials is not tolerable and needs to be improved. Researchers, protocol reviewers, local ethical committees, journal reviewers, and editors should make a concerted effort to incorporate, report, and publish such information to understand its potential impact on study results.

Inequalities of caries experience in Nevada youth expressed by DMFT index vs. Significant Caries Index (SiC over time

Directory of Open Access Journals (Sweden)

Mobley Connie

2011-04-01

Full Text Available Abstract Background With the increasingly polarized distribution of dental caries among children and adolescents, the usual DMFT measure has become a less meaningful population descriptor. To re-focus on identifying the high caries prevalence group the Significant Caries Index (SiC was created. The aims of this study were to analyze the prevalence and severity of dental caries in Nevada youth over a period of eight years and to compare its expression by means of DMFT and SiC; analyze the caries trends in the population and their underlying factors, and determine whether Nevada youth were at risk for significantly high levels of dental caries. Methods Retrospective data was analyzed from a series of sequential, standardized oral health surveys across eight years (2001/2002-2008/2009 that included over 62,000 examinations of adolescents 13-19 years of age, attending public/private Nevada schools. Mean Decayed-Missing-Filled Teeth index (DMFT and Significant Caries Index (SiC were subsequently computed for each academic year. Descriptive statistics were reported for analysis of comparative DMFT and SiC scores in relation to age, gender, racial background, and residence in a fluoridated/non-fluoridated community. Logistic regression analysis was used to analyze the differential impact of the variables on the probability of being in the high caries prevalence group. Results Comparison of students' mean DMFT to National (NHANES data confirmed that dental caries remains a common chronic disease among Nevada youth, presenting higher prevalence rates and greater mean scores than the national averages. Downward trends were found across all demographics compared between survey years 1 and 6 with the exception of survey year 3. An upward trend began in survey year six. Over time, the younger group displayed an increasing proportion of cariesfree individuals while a decreasing proportion was found among older examinees. As expected, the mean SiC score was

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.

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

Prevalence of dental caries and associated factors among 12 years old students in Eritrea.

Science.gov (United States)

Andegiorgish, Amanuel Kidane; Weldemariam, Bizen Weldmicheal; Kifle, Meron Mehari; Mebrahtu, Filmon Gebreysus; Zewde, Henos Keflom; Tewelde, Micheal Gebregziabhir; Hussen, Mohammed Anwar; Tsegay, Winta Kesete

2017-12-29

Dental caries is one of the most prevalent diseases of childhood in developing countries. However, there is a paucity of epidemiological data on the prevalence and associated factors of dental caries in Eritrea. The objective of this study was to assess the prevalence and associated factors of dental caries among 12 years old school children in Eritrea. A school based cross sectional study was conducted among 225 twelve years old students in two selected schools. One school from randomly selected urban and rural subzones of the country were selected. WHO adopted questionnaire and a standard checklist were used to collect relevant data. To assess dental caries, two examiners were calibrated by a certified dentist and inter observer agreement was calculated using the Cohen's Kappa statistic (0.82). All data analysis was done using SPSS version 20. The prevalence of dental caries was 78%, without significant difference between males (78%) and females (79%).The mean DMFT value was 2.50 (±2.21). The decayed component contributed 98.3% of the score as it had 2.44 (±1.2) share to the mean DMFT value. The first molar was the most affected tooth with a DMFT value of 1.55 (±1.36). The mean significant caries index score (SiC) was 4.97 (±1.9) which is higher than the upper limit of SiC value of 3 set by the WHO as a global average. More than half of the respondents had never visited a dentist and out of the students who had utilized a dental health facility, 82% of visits were due to dental pain while visits for regular checkups were cited by only 6.6% of the respondents. Dental caries was found to be a common public health problem among 12 years old Eritrean students. The prevalence of dental caries, mean DMFT and SiC scores were higher than the average score of other developing countries. Gaps in dental health service utilization, dental health practices and suboptimal water fluoride levels contribute to poor dental health among school children in Eritrea.

Collaborative learning in pre-clinical dental hygiene education.

Science.gov (United States)

Mueller-Joseph, Laura J; Nappo-Dattoma, Luisa

2013-04-01

Dental hygiene education continues to move beyond mastery of content material and skill development to learning concepts that promote critical-thinking and problem-solving skills. The purpose of this research was to evaluate the effectiveness of collaborative learning and determine the growth in intellectual development of 54 first-year dental hygiene students. The control group used traditional pre-clinical teaching and the experimental group used collaborative pedagogy for instrument introduction. All students were subjected to a post-test evaluating their ability to apply the principles of instrumentation. Intellectual development was determined using pre- and post-tests based on the Perry Scheme of Intellectual Development. Student attitudes were assessed using daily Classroom Assessment Activities and an end-of-semester departmental course evaluation. Findings indicated no significant difference between collaborative learning and traditional learning in achieving pre-clinical competence as evidenced by the students' ability to apply the principles of instrumentation. Advancement in intellectual development did not differ significantly between groups. Value added benefits of a collaborative learning environment as identified by the evaluation of student attitudes included decreased student reliance on authority, recognition of peers as legitimate sources of learning and increased self-confidence. A significant difference in student responses to daily classroom assessments was evident on the 5 days a collaborative learning environment was employed. Dental hygiene students involved in a pre-clinical collaborative learning environment are more responsible for their own learning and tend to have a more positive attitude toward the subject matter. Future studies evaluating collaborative learning in clinical dental hygiene education need to investigate the cost/benefit ratio of the value added outcomes of collaborative learning.

Effects of SiC amount on phase compositions and properties of Ti3SiC2-based composites

Institute of Scientific and Technical Information of China (English)

蔡艳芝; 殷小玮; 尹洪峰

2015-01-01

The phase compositions and properties of Ti3SiC2-based composites with SiC addition of 5%−30% in mass fraction fabricated by in-situ reaction and hot pressing sintering were studied. SiC addition effectively prevented TiC synthesis but facilitated SiC synthesis. The Ti3SiC2/TiC−SiC composite had better oxidation resistance when SiC added quantity reached 20% but poorer oxidation resistance with SiC addition under 15%than Ti3SiC2/TiC composite at higher temperatures. There were more than half of the original SiC and a few Ti3SiC2 remaining in Ti3SiC2/TiC−SiC with 20% SiC addition, but all constituents in Ti3Si2/TiC composite were oxidized after 12 h in air at 1500 °C. The oxidation scale thickness of TS30, 1505.78μm, was near a half of that of T, 2715μm, at 1500 °C for 20 h. Ti3SiC2/TiC composite had a flexural strength of 474 MPa, which was surpassed by Ti3SiC2/TiC−SiC composites when SiC added amount reached 15%. The strength reached the peak of 518 MPa at 20%SiC added amount.

Self-induced vomiting and dental erosion--a clinical study.

Science.gov (United States)

Uhlen, Marte-Mari; Tveit, Anne Bjørg; Stenhagen, Kjersti Refsholt; Mulic, Aida

2014-07-29

In individuals suffering from eating disorders (ED) characterized by vomiting (e.g. bulimia nervosa), the gastric juice regularly reaches the oral cavity, causing a possible risk of dental erosion. This study aimed to assess the occurrence, distribution and severity of dental erosions in a group of Norwegian patients experiencing self-induced vomiting (SIV). The individuals included in the study were all undergoing treatment at clinics for eating disorders and were referred to a university dental clinic for examinations. One calibrated clinician registered erosions using the Visual Erosion Dental Examination (VEDE) system. Of 72 referred patients, 66 (63 females and three males, mean age 27.7 years) were or had been experiencing SIV (mean duration 10.6 years; range: 3 - 32 years), and were therefore included in the study. Dental erosions were found in 46 individuals (69.7%), 19 had enamel lesions only, while 27 had both enamel and dentine lesions. Ten or more teeth were affected in 26.1% of those with erosions, and 9% had ≥10 teeth with dentine lesions. Of the erosions, 41.6% were found on palatal/lingual surfaces, 36.6% on occlusal surfaces and 21.8% on buccal surfaces. Dentine lesions were most often found on lower first molars, while upper central incisors showed enamel lesions most frequently. The majority of the erosive lesions (48.6%) were found in those with the longest illness period, and 71.7% of the lesions extending into dentine were also found in this group. However, despite suffering from SIV for up to 32 years, 30.3% of the individuals showed no lesions. Dental erosion commonly affects individuals with ED experiencing SIV, and is more often found on the palatal/lingual surfaces than on the buccal in these individuals, confirming a common clinical assumption.

Solid waste production and its management in dental clinics in Gorgan, northern Iran.

Science.gov (United States)

Nabizadeh, R; Faraji, H; Mohammadi, A A

2014-10-01

Waste produced in dental clinics has been the topic of investigations for many years. These waste materials have important health impacts and are hazardous to humans and the environment. To investigating solid waste production and its management in dental clinics in Gorgan, northern Iran. In this cross-sectional study, 45 of 143 public dental practices and 5 of 25 private dental practices were selected and studied. From each clinic, 3 samples were taken and analyzed at the end of successive working days (Tuesday and Wednesday). Samples were manually sorted into 50 components. The measured components were then classified on the basis of their characteristics, hazard potentials, and WHO classification. The total annual amount of dental waste produced in public and private dental practices in Gorgan was 12 015.1 and 3135.0 kg, respectively. Production percentages of infectious, domestic, chemical and pharmaceutical, and toxic waste in public dental practices were 38.4%, 33.7%, 6.6%, and 0.6%, respectively. The percentages for private practices were 8.7%, 10.6%, 1.1%, and 0.1%, respectively. Dental waste management in Gorgan is inadequate; dental waste is not properly segregated, collected, and disposed, as demanded by the WHO. Employees in dentist offices must be trained in correct handling of waste products and the associated risks.

An Innovative Clinical Skills “Boot Camp” for Dental Medicine Residents

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Jenny Castillo

2017-05-01

Full Text Available During a 1-year hospital-based residency, dental residents are required to rotate through many departments including surgery, medicine, and emergency medicine. It became apparent that there was a gap between clinical skills knowledge taught in dental school curriculum and skills required for hospital-based patient care. In response, a simulation-based intensive clinical skill “boot camp” was created. The boot camp provided an intensive, interactive 3-day session for the dental residents. During the 3 days, residents were introduced to medical knowledge and skills that were necessary for their inpatient hospital rotations but were lacking in traditional dental school curriculum. Effectiveness of the boot camp was assessed in terms of knowledge base and comfort through presession and postsession surveys. According to resident feedback, this intensive introduction for the dental residents improved their readiness for their inpatient hospital-based residency.

Barrier-free dental health care: A situation analysis of the dental care settings and providers' attitudes in private dental clinics for the movement-disabled in Bengaluru City

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Vyoma Grandhi Venkatesh

2017-01-01

Full Text Available Introduction: Movement-disabled individuals require oral health care like everyone else. However, they face a multitude of accessibility issues. Since private dental clinics are the most commonly utilized type of oral health care in India, it becomes pertinent to know how accessible these clinics are for movement-disabled individuals. Aim: To assess the accessibility of private dental clinics in Bengaluru city to movement-disabled people. Materials and Methods: A cross-sectional survey was conducted among a random sample of 250 dentists practicing at private dental clinics in Bengaluru city using a structured questionnaire. The data were entered into the Microsoft Office Excel 2007 and were analyzed. Chi-square test was done to assess the association of dentists' previous experience in treating mobility-disabled patients and their attitude toward treating such patients. Results: In the current study, 81.2% (203 of the respondents expressed willingness to treat mobility-disabled individuals. However, wheelchair provision was present in only 15.6% (39 of the clinic, and only one-fifth of the clinics had a slope or ramp for facilitating entry of wheelchair-bound individuals. Gurneys, stretchers, and ceiling-mounted lifts were present in < 10% of the private dental clinics. The reasons for poor accessibility to movement disabled were reported as lack of financial resources followed by lack of utilization of facilities by movement-disabled individuals. Conclusion: The dentists displayed favorable attitude toward treating movement-disabled individuals. However, only a few private dental clinics met the architectural requirements and were equipped for treating such patients.

Dental caries among children visiting a mobile dental clinic in South Central Kentucky: a pooled cross-sectional study.

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Dawkins, Erika; Michimi, Akihiko; Ellis-Griffith, Gregory; Peterson, Tina; Carter, Daniel; English, Gary

2013-05-02

Dental caries is one of the most common chronic childhood diseases affecting a large portion of children in the United States. The prevalence of childhood dental caries in Kentucky is among the highest in the nation. The purposes of this study are to (1) compare sociodemographic differences between caries and no caries groups and (2) investigate factors associated with untreated dental caries among children who visited a mobile dental clinic in South Central Kentucky. Study subjects were children aged 6 to 15 years who participated in the school-based dental sealant program through the mobile dental clinic operated by the Institute for Rural Health at Western Kentucky University between September 2006 and May 2011 (n = 2,453). Descriptive statistics were calculated for sociodemographic factors (age, gender, race/ethnicity, insurance status, and urban versus rural residential location) and caries status. We used chi-square tests to compare sociodemographic differences of children stratified by caries and no caries status as well as three levels of caries severity. We developed a logistic regression model to investigate factors associated with untreated dental caries while controlling for sociodemographic characteristics. The proportion of children having untreated dental caries was 49.7% and the mean number of untreated dental caries was 2.0. The proportion of untreated dental caries was higher in older children, children with no insurance and living in rural residential locations, and caries severity was also higher in these groups. Odds ratio indicated that older ages, not having private insurance (having only public, government-sponsored insurance or no insurance at all) and rural residential location were associated with having untreated dental caries after controlling for sociodemographic characteristics of children. Untreated dental caries was more likely to be present in older children living in rural areas without insurance. Health interventionists may use

Solid Waste Production and Its Management in Dental Clinics in Gorgan, Northern Iran

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R Nabizadeh

2014-09-01

Full Text Available Background: Waste produced in dental clinics has been the topic of investigations for many years. These waste materials have important health impacts and are hazardous to humans and the environment. Objective: To investigating solid waste production and its management in dental clinics in Gorgan, northern Iran. Methods: In this cross-sectional study, 45 of 143 public dental practices and 5 of 25 private dental practices were selected and studied. From each clinic, 3 samples were taken and analyzed at the end of successive working days (Tuesday and Wednesday. Samples were manually sorted into 50 components. The measured components were then classified on the basis of their characteristics, hazard potentials, and WHO classification. Results: The total annual amount of dental waste produced in public and private dental practices in Gorgan was 12 015.1 and 3135.0 kg, respectively. Production percentages of infectious, domestic, chemical and pharmaceutical, and toxic waste in public dental practices were 38.4%, 33.7%, 6.6%, and 0.6%, respectively. The percentages for private practices were 8.7%, 10.6%, 1.1%, and 0.1%, respectively. Conclusion: Dental waste management in Gorgan is inadequate; dental waste is not properly segregated, collected, and disposed, as demanded by the WHO. Employees in dentist offices must be trained in correct handling of waste products and the associated risks.

Factors influencing patients seeking oral health care in the oncology dental support clinic at an urban university dental school setting.

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Corrigan, Dale M; Walker, Mary P; Liu, Ying; Mitchell, Tanya Villalpando

2014-01-01

The purpose of this study was to identify predictors and/or factors associated with medically compromised patients seeking dental care in the oncology dental support clinic (ODSC) at the University of Missouri-Kansas City (UMKC) School of Dentistry. An 18-item survey was mailed to 2,541 patients who were new patients to the clinic from 2006 to 2011. The response rate was approximately 18% (n = 450). Analyses included descriptive statistics of percentages/frequencies as well as predictors based on correlations. Fifty percent of participants, 100 females and 119 males, identified their primary medical diagnosis as cancer. Total household income (p dental care (p dental health. Perceived overall health (p Care Dentistry Association and Wiley Periodicals, Inc.

Smoking cessation advice: Knowledge, attitude, and practice among clinical dental students'

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Allama Prabhu

2017-01-01

Full Text Available Background: Smoking is the single most important public health challenge facing the National Health Service. The detrimental effects on the general health of tobacco smoking are well documented. Smoking is a primary risk factor for oral cancer and many oral diseases. Dental professional scan plays an important role in preventing adverse health effects by promoting smoking cessation. Objective: To assess the knowledge, attitude, and practice among clinical dental students in giving smoking cessation advice and to explore the barriers to this activity. Materials and Methods: A total of 262 clinical dental trainee of two dental colleges (College of Dental Sciences and Bapuji Dental College of Davangere city were included in the survey. A self-administered questionnaire was administered to assess the knowledge, attitude, and practice toward Tobacco Cessation Advise. Results: Among the 262 participants in the study, around 51% said they know about Nicotine Replacement Therapy, and among them, only 4.6% were aware of the options available in the market. When asked about 5A's of tobacco cessation, only 35.5% were aware of it. Similarly, when asked about 5R's of tobacco cessation, 48.5% were unaware of it. Conclusions: The respondents did not have sufficient knowledge regarding tobacco cessation advice. With patient's disinterest and lack of time being quoted as the important barriers in providing tobacco cessation advice, it is highly recommended that there is need to incorporate few chapters on tobacco, its effect and cessation of habit in the undergraduate dental curriculum with simultaneous application of the same in clinical practice.

Dental Hygienists' Perceptions of Preparedness for Clinical Practice: A Phenomenological Study

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Cantrell, Lezlie M.

2012-01-01

The purpose of this phenomenological study was to identify, compile, and describe how community college graduate dental hygienists perceived their initial dental hygiene curriculum preparation and how they subsequently adapted their curriculum preparation in order to perform their responsibilities in their first clinical dental hygiene job.…

Curriculum content and assessment of pre-clinical dental skills: A survey of undergraduate dental education in Europe.

Science.gov (United States)

Field, J; Stone, S; Orsini, C; Hussain, A; Vital, S; Crothers, A; Walmsley, D

2018-05-01

Since 1981, the qualifications for various healthcare professionals across the European Union have enjoyed mutual recognition in accordance with the EU Directive 81/1057/EEC. Whilst the directive includes dental practitioners, it is recognised that significant variation exists in curriculum structure, content and scope of practice across institutions. This article aimed to explore pan-European practice in relation to curriculum content, teaching and learning strategies and assessment of pre-clinical dental skills. A request to complete an online questionnaire, in English, was sent electronically to skills leads at all Association of Dental Education in Europe member schools. The questionnaire collected information in relation to institution and country, regulatory requirements to demonstrate safety, details of specific pre-clinical skills courses, learning materials and teaching staff. Forty-eight institutions, from 25 European countries responded. Seven countries (n=7, 28%) reported no requirement to demonstrate student operative safety prior to patient treatment. Several core and operative clinical skills are common to the majority of institutions. The most commonly taught core skills related directly to the clinical environment such as cross-infection control and hand washing. The least common were skills that indirectly related to patient care, such as communication skills and working as a team. There are clear differences within European pre-clinical dental education, and greater efforts are needed to demonstrate that all European students are fit to practice before they start treating patients. Learning outcomes, teaching activities and assessment activities of pre-clinical skills should be shared collaboratively to further standardise curricula. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Comparison of clinical practice education in dental hygiene schools in eight countries

DEFF Research Database (Denmark)

Inukai, Junko; Sakurai, Miwa; Nakagaki, Haruo

2012-01-01

OBJECTIVES: The profession of dental hygienist is one of the few in which the primary function of the practitioner is to prevent oral disease and to promote the well-being of patients. The aim of this study was to investigate clinical training conditions in schools of dental hygiene in eight coun...... are trained to perform local anaesthesia and to fill and extract deciduous teeth although the country does not have a specific qualification system. CONCLUSIONS: The contents of clinical training and education in schools of dental hygiene differ greatly among countries....... countries (the USA, Canada, the UK, Sweden, Denmark, Thailand, South Korea and Japan). METHODS: In 2006, we sent out a questionnaire in which we asked dental hygiene schools about how they educate dental hygiene students. RESULTS: The techniques taught to students in schools in Western industrialised...

Student Perceptions of Effective Clinical Teaching Characteristics in Dental Hygiene Programs in Northeastern States

Science.gov (United States)

Bearor, Dawn E.

2012-01-01

The clinical education component provided to dental hygiene students is an essential part of their development as competent practitioners. Instructor approaches to clinical teaching are therefore critical in providing quality clinical learning experiences. This study sought to identify dental hygiene students' perceptions of "best" and…

What is the relationship between emotional intelligence and dental student clinical performance?

Science.gov (United States)

Victoroff, Kristin Zakariasen; Boyatzis, Richard E

2013-04-01

Emotional intelligence has emerged as a key factor in differentiating average from outstanding performers in managerial and leadership positions across multiple business settings, but relatively few studies have examined the role of emotional intelligence in the health care professions. The purpose of this study was to examine the relationship between emotional intelligence (EI) and dental student clinical performance. All third- and fourth-year students at a single U.S. dental school were invited to participate. Participation rate was 74 percent (100/136). Dental students' EI was assessed using the Emotional Competence Inventory-University version (ECI-U), a seventy-two-item, 360-degree questionnaire completed by both self and other raters. The ECI-U measured twenty-two EI competencies grouped into four clusters (Self-Awareness, Self-Management, Social Awareness, and Relationship Management). Clinical performance was assessed using the mean grade assigned by clinical preceptors. This grade represents an overall assessment of a student's clinical performance including diagnostic and treatment planning skills, time utilization, preparation and organization, fundamental knowledge, technical skills, self-evaluation, professionalism, and patient management. Additional variables were didactic grade point average (GPA) in Years 1 and 2, preclinical GPA in Years 1 and 2, Dental Admission Test academic average and Perceptual Ability Test scores, year of study, age, and gender. Multiple linear regression analyses were conducted. The Self-Management cluster of competencies (b=0.448, pintelligence may be an important predictor of clinical performance, which has important implications for students' development during dental school.

Ectodermal Dysplasia: A Clinical Overview for the Dental Practitioner.

Science.gov (United States)

Halai, Tina; Stevens, Claire

2015-10-01

The term ectodermal dysplasia (ED) is used to describe a group of rare congenital disorders characterized by abnormalities of two or more ectodermal structures such as the skin, hair, nails, teeth and sweat glands. This paper will give an overview of the aetiology of ED and describe the manifestations and dental management of this condition. In particular, the important role of the dental practitioner in the identification and management of patients with ED will be highlighted. CPD/Clinical Relevance: Dental practitioners should be aware of the oral features of ectodermal dysplasia and be able to make timely referrals and provide appropriate continuing care for these patients.

Characterization of SiC based composite materials by the infiltration of ultra-fine SiC particles

International Nuclear Information System (INIS)

Lee, J.K.; Lee, S.P.; Byun, J.H.

2010-01-01

The fabrication route of SiC materials by the complex compound of ultra-fine SiC particles and oxide additive materials has been investigated. Especially, the effect of additive composition ratio on the characterization of SiC materials has been examined. The characterization of C/SiC composites reinforced with plain woven carbon fabrics was also investigated. The fiber preform for C/SiC composites was prepared by the infiltration of complex mixture into the carbon fabric structure. SiC based composite materials were fabricated by a pressure assisted liquid phase sintering process. SiC materials possessed a good density higher than about 3.0 Mg/m 3 , accompanying the creation of secondary phase by the chemical reaction of additive materials. C/SiC composites also represented a dense morphology in the intra-fiber bundle region, even if this material had a sintered density lower than that of monolithic SiC materials. The flexural strength of SiC materials was greatly affected by the composition ratio of additive materials.

Clinical characteristics of dental emergencies and prevalence of dental trauma at a university hospital emergency center in Korea.

Science.gov (United States)

Bae, Ji-Hyun; Kim, Young-Kyun; Choi, Yong-Hoon

2011-10-01

The aim of this study was to examine the clinical characteristics of dental emergency patients who visited a university hospital emergency center and to evaluate the incidence of dental trauma. A retrospective chart review of patients with dental complaints and who visited the Seoul National University Bundang Hospital (SNUBH) emergency center in Gyeonggi-do, Korea, from January 2009 to December 2009 was conducted. Information regarding age, gender, the time, day, and month of presentation, diagnosis, treatment, and follow up was collected and analyzed. One thousand four hundred twenty-five patients with dental problems visited the SNUBH emergency center. Dental patients accounted for 1.47% of the total 96,708 patients at the emergency center. The male-to-female ratio was 1.68:1, with a considerably larger number of male patients (62.7%). The age distribution peak was at 0-9 years (27.5%), followed by patients in their forties (14.1%). The number of patients visiting the dental emergency center peaked in May (14.2%), on Sundays (22.4%), and between 2100 and 2400 h (20.8%). The patients' chief complaints were as follows: dental trauma, dental infection, oral bleeding, and temporomandibular joint disorder (TMD). The prevalence of dental trauma was 66%. The reasons for dental emergency visits included the following: dental trauma, dental infection, oral bleeding, and TMD, with 66% of the patients requiring management of dental trauma. It is important that dentists make a prompt, accurate diagnosis and initiate effective treatment in case of dental emergencies, especially dental trauma. © 2011 John Wiley & Sons A/S.

Reflective blogs in clinical education to promote critical thinking in dental hygiene students.

Science.gov (United States)

Wetmore, Ann O'Kelley; Boyd, Linda D; Bowen, Denise M; Pattillo, Robin E

2010-12-01

One challenge facing dental hygiene, as well as dental, education is to identify clinical teaching strategies promoting critical thinking and clinical reasoning. These skills are crucial elements in the practice of dental hygiene. A two-group design (intervention, n=28, and control, n=30) assessed first-year dental hygiene students using pre-and post-Health Science Reasoning Test (HSRT) scores to evaluate the effect of reflective blogging on critical thinking skills. A reflective blog rubric, based on Mezirow's levels of reflection, determined if reflective blogging increased the level of reflection for dental hygiene students. The results suggest within this nonprobability sample that reflective blogging did not produce a significant change in students' HSRT scores (p>0.05). However, analyses of reflective blog rubric scores demonstrated statistically significant improvements (pcritical thinking.

Attitudes and motivations regarding willingness to participate in dental clinical trials

OpenAIRE

Friesen, Lynn Roosa; Williams, Karen B.

2016-01-01

Background: This study examined attitudes about research, knowledge of the research process, reasons for and satisfaction with participation in a dental clinical trial as a function of demographic characteristics. Materials and methods: 180 adults were invited to complete a 47-item survey at the completion of a 10-week dental product study at a Midwestern academic dental center. Seven demographic items included gender, race/ethnicity, age, education, household income, location of usual den...

Clinical and Radiographic Assessment of Reasons for Replacement of Metal- Ceramic Fixed Dental Prostheses in Patients Referring to Dental School.

Science.gov (United States)

Al Refai, Roa'a; Saker, Samah

2018-01-01

The expected length of service and reasons for fixed dental prostheses (FDPs) replacement are a frequent inquiry by patients while the answers were mainly based on studies reports that was conducted outside the middle east region. This clinical and radiographic survey was constructed to assess and survey clinically and radiographically the reasons of replacement of metal-ceramic fixed dental prostheses, amongst patients reporting at dental school in Taibah University. Between January and May 2016, 151 patients were recruited for this study. Interview (include questions pertained to the length of service of the prosthesis, the nature of complaint as told by patient in her own words), clinical examination, intra-oral photographs, and periapical radiographs, were done by the researchers. The parameters assessed were secondary caries, open margins, loss of retention, failure of endodontic treatment of the abutment and periodontal diseases. A total number of 249 failed fixed dental prostheses were evaluated. Of which 180 (39.7%) were single crowns, 159 (35.0%) were retainers and 117 (25.8%) were pontics in 69 fixed partial denture. The most common reason for replacement of fixed restorations was periodontal diseases affecting 92.8% of all types' restorations, followed by defective margin in 90.4% of examined restoration, poor aesthetic in 88% of restorations, while periapical involvement was found in 85.5% of fixed dental prosthesis. The survival rates of fixed prostheses were not predictable, and no association was found between number of years in service and the number of restorations. The most common reasons for replacing single unit fixed dental prostheses are periodontal diseases and periapical involvement, while defective margins and poor aesthetic mainly associated with multi-unit fixed dental prostheses. Key words: Failure, Fixed dental prosthesis, Survival, Replacement.

Dental caries, restorations and extractions by dental caries in first permanent molars. Clinical and radiographic study

International Nuclear Information System (INIS)

Aguiar, Sandra Maria H.C. Avila de; Santos Pinto, Ruy dos

1996-01-01

This research analyse by clinical and radiographic study, dental caries, restorations and extractions in 1.600 first permanent molars, from 400 children, both sexes, aged 5 to 13 years old, assisted in the Children's Clinic, Faculdade de Odontologia de Aracatuba, UNESP, in 1994. (author)

Does Reflective Learning with Feedback Improve Dental Students' Self-Perceived Competence in Clinical Preparedness?

Science.gov (United States)

Ihm, Jung-Joon; Seo, Deog-Gyu

2016-02-01

The value of dental students' self-assessment is often debated. The aim of this study was to explore whether reflective learning with feedback enabled dental students to more accurately assess their self-perceived levels of preparedness on dental competencies. Over 16 weeks, all third- and fourth-year students at a dental school in the Republic of Korea took part in clinical rotations that incorporated reflective learning and feedback. Following this educational intervention, they were asked to assess their perceptions of their clinical competence. The results showed that the students reported feeling most confident about performing periodontal treatment (mean 7.1 on a ten-point scale) and least confident about providing orthodontic care (mean 5.6). The fourth-year students reported feeling more confident on all the competencies than the third-year students. Their self-perceived competence in periodontal treatment and oral medicine significantly predicted the instructors' clinical evaluations. This study offered insights into determining if structured reflective learning with effective feedback helps to increase dental students' self-perceived level of clinical preparedness.

Patient radiation dose in some dental radiography clinics in Khartoum, Sudan

International Nuclear Information System (INIS)

Mohamed, Aziza Hamed Abdelgadir

2016-01-01

Patient dose audit is an important tool for quality control and it is important for monitoring patient exposure. The DAP meter has proved to be an easy and accurate tool for patient dosimetry and for establishment of diagnostic reference levels in dental radiology. The objective of this study was measure patient dose in dental radiography in some dental radiography clinics in Khartoum. The study was performed in five dental clinics comprising six panoramic and six intraoral dental radiography devices in Khartoum state. The incident surface air kerma (k i ) and dose area product were measured for intraoral and panoramic dental examinations, respectively for digital and film imaging modalities. Incident surface air kerma (k i ) was measured using calibrated dose rate meter where dose area product were determined from dose width product (DWP) measured using 3 cc pencil type CT ionization chamber. For intraoral examinations, the maximum, average and minimum, (1.95, 1.48, and 1.24) mGy, (5.84, 4.54, and 3.6) mGy for digital and imaging, respectively. This result was lower in digital in traol and higher in film imaging. The result for panoramic examination calculated dose area product (DAP) mean value for adult and pediatric was (103, 70.42) mGy cm 2 , respectively, where the dose for digital imaging was highest in two centers, compared to previous study. Increased patient dose in intraoral dental radiography could partially be explained by the use of circular collimators. or intraoral x-ray equipment the downward trend in patient dose can only be continue, a through the adoption of digital imaging methods. Our results are relatively higher in digital panoramic dental examinations. It is important to point out that non of the dental units under study were covered by regular quality assurance programme.(Author)

Fire safety in dental clinics: Basics for dentists and dental students

Directory of Open Access Journals (Sweden)

Kalyana Chakravarthy Pentapati

2015-01-01

Full Text Available Fire safety is essential component and requirement in health care sector. It includes components like emergency exits, manual call outs, different types of fire extinguishers, safe assembly area, fire hydrant system with water sprinkler systems etc. We attempt to provide some basics about fire and fire safety that are prerequisite for safe working environment in dental clinics along with some recommendations that can be incorporated in the curriculum.

Phenomenological inelastic constitutive equations for SiC and SiC fibers under irradiation

International Nuclear Information System (INIS)

El-Azab, A.; Ghoniem, N.M.

1994-01-01

Experimental data on irradiation-induced dimensional changes and creep in β-SiC and SiC fibers is analyzed, with the objective of studying the constitutive behavior of these materials under high-temperature irradiation. The data analysis includes empirical representation of irradiation-induced dimensional changes in SiC matrix and SiC fibers as function of time and irradiation temperature. The analysis also includes formulation of simple scaling laws to extrapolate the existing data to fusion conditions on the basis of the physical mechanisms of radiation effects on crystalline solids. Inelastic constitutive equations are then developed for SCS-6 SiC fibers, Nicalon fibers and CVD SiC. The effects of applied stress, temperature, and irradiation fields on the deformation behavior of this class of materials are simultaneously represented. Numerical results are presented for the relevant creep functions under the conditions of the fusion reactor (ARIES IV) first wall. The developed equations can be used in estimating the macro mechanical properties of SiC-SiC composite systems as well as in performing time-dependent micro mechanical analysis that is relevant to slow crack growth and fiber pull-out under fusion conditions

Dental Pulp: Correspondences and Contradictions between Clinical and Histological Diagnosis

Science.gov (United States)

Giuroiu, Cristian Levente; Căruntu, Irina-Draga; Lozneanu, Ludmila; Melian, Anca; Vataman, Maria; Andrian, Sorin

2015-01-01

Dental pulp represents a specialized connective tissue enclosed by dentin and enamel, the most highly mineralized tissues of the body. Consequently, the direct examination as well as pathological evaluation of dental pulp is difficult. Within this anatomical context, our study aimed to evaluate the correlation between dental pulp lesions and clinical diagnosis. Pulpectomies were performed for 54 patients with acute and chronic irreversible pulpitides and for 5 patients (control group) with orthodontic extractions. The morphological features were semiquantitatively assessed by specific score values. The clinical and morphological correspondence was noted for 35 cases (68.62%), whereas inconsistency was recorded for 16 cases (31.38%). The results of the statistical analysis revealed the correlations between clinically and pathologically diagnosed acute/chronic pulpitides. No significant differences were established between the score values for inflammatory infiltrate intensity, collagen depositions, calcifications and necrosis, and acute, respectively chronic pulpitides. We also obtained significant differences between acute pulpitides and inflammatory infiltrate and calcifications and between chronic pulpitides and inflammatory infiltrate, collagen deposition, and calcifications. On the basis of the predominant pathological aspects, namely, acute and chronic pulpitis, we consider that the classification schemes can be simplified by adequately reducing the number of clinical entities. PMID:26078972

Comparison of the clinical examination with the panoramic radiography in the diagnosis of dental caries

Energy Technology Data Exchange (ETDEWEB)

Choi, Hang Moon [Dept. of Oral and Maxillofacial Radiology and Dental Research Institute, College of Dentistry, Seoul National University, Seoul (Korea, Republic of)

1999-02-15

The objective of this study was to compare clinical examination of of dental caries and secondary caries with panoramic examination, and to examine bone lesions and dental anomaly of unerupted state. In this study, clinical records and panoramic radiographs were available for 89 first grade students in elementary school. Dental caries of occlusal surfaces, proximal surfaces, and buccolingual surfaces were examined. Secondary caries was examined too. In addition, the central lesion and dental anomaly of unerupted state were examined in panoramic radiographs. The obtained results were as followed :1. Carious detectability of clinical examination in occlusal and buccolingual surface was higher than that of panoramic examination, but it is statistically insignificant (p>0.05). In proximal surface, carious detectability of panoramic examination was higher than that of clinical examination, and it is statistically significant (p<0.01). 2. In contrast to clinical examination only, when the two examination methods were combined, there was additional detection of dental caries (26.7% in occlusal surface, 48.2% in proximal surface, 33.3% in buccolingual surface, and 38.3% totally). 3. In detection of secondary caries, panoramic examination had lower ability than clinical examination in all three surfaces, but in case that both methods were combined, totally 36.0% extra carious lesions were detected. 4. In panoramic examination, detectability of secondary caries in upper teeth is lower than lower teeth. 5. In panoramic examination, it was possible to detect the central lesions and dental anomalies of unerupted state which cannot be detected in clinical examination. It is useful to combine the panoramic examination with clinical examination in order to increase carious detectability and to evaluate the central lesions and dental anomalies of unerupted state.

Comparison of the clinical examination with the panoramic radiography in the diagnosis of dental caries

International Nuclear Information System (INIS)

Choi, Hang Moon

1999-01-01

The objective of this study was to compare clinical examination of of dental caries and secondary caries with panoramic examination, and to examine bone lesions and dental anomaly of unerupted state. In this study, clinical records and panoramic radiographs were available for 89 first grade students in elementary school. Dental caries of occlusal surfaces, proximal surfaces, and buccolingual surfaces were examined. Secondary caries was examined too. In addition, the central lesion and dental anomaly of unerupted state were examined in panoramic radiographs. The obtained results were as followed :1. Carious detectability of clinical examination in occlusal and buccolingual surface was higher than that of panoramic examination, but it is statistically insignificant (p>0.05). In proximal surface, carious detectability of panoramic examination was higher than that of clinical examination, and it is statistically significant (p<0.01). 2. In contrast to clinical examination only, when the two examination methods were combined, there was additional detection of dental caries (26.7% in occlusal surface, 48.2% in proximal surface, 33.3% in buccolingual surface, and 38.3% totally). 3. In detection of secondary caries, panoramic examination had lower ability than clinical examination in all three surfaces, but in case that both methods were combined, totally 36.0% extra carious lesions were detected. 4. In panoramic examination, detectability of secondary caries in upper teeth is lower than lower teeth. 5. In panoramic examination, it was possible to detect the central lesions and dental anomalies of unerupted state which cannot be detected in clinical examination. It is useful to combine the panoramic examination with clinical examination in order to increase carious detectability and to evaluate the central lesions and dental anomalies of unerupted state.

Effect of Reactant Concentration on the Microstructure of SiC Nano wires Grown In Situ within SiC Fiber Preforms

International Nuclear Information System (INIS)

Kim, Weon Ju; Kang, Seok Min; Park, Ji Yeon; Ryu, Woo Seog

2006-01-01

Silicon carbide fiber-reinforced silicon carbide matrix (SiC f /SiC) composites are considered as advanced materials for control rods and other in-core components of high-temperature gas cooled reactors. Although the carbon fiber-reinforced carbon matrix (C f /C) composites are more mature and have advantages in cost, manufacturability and some thermomechanical properties, the SiC f /SiC composites have a clear advantage in irradiation stability, specifically a lower level of swelling and retention of mechanical properties. This offers a lifetime component for control rod application to HTGRs while the Cf/C composites would require 2-3 replacements over the reactor lifetime. In general, the chemical vapor infiltration (CVI) technique has been used most widely to produce SiC f /SiC composites. Although the technique produces a highly pure SiC matrix, it requires a long processing time and inevitably contains large interbundle pores. The present authors have recently developed 'whisker growing-assisted process,' in which one-dimensional SiC nano structures with high aspect ratios such as whiskers, nano wires and nano rods are introduced into the fiber preform before the matrix infiltration step. This novel method can produce SiC f /SiC composites with a lower porosity and an uniform distribution of pores when compared with the conventional CVI. This would be expected to increase mechanical and thermal properties of the SiC f /SiC composites. In order to take full advantage of the whisker growing strategy, however, a homogeneous growth of long whiskers is required. In this study, we applied the atmospheric pressure CVI process without metallic catalysts for the growth of SiC nano wires within stacked SiC fiber fabrics. We focused on the effect of the concentration of a reactant gas on the growth behavior and microstructures of the SiC nano wires and discussed a controlling condition for the homogenous growth of long SiC nano wires

Cost differentials of dental outpatient care across clinical dentistry branches

Directory of Open Access Journals (Sweden)

Jovana Rančić

2015-03-01

Full Text Available Background: Dental care presents affordability issues in Central & Eastern European transitional economies due to lack of insurance coverage in most countries of the region and almost complete out-of-pocket payments by citizens.Objective: Real world estimates on cost differentials across clinical dentistry branches, ICD-10 diagnostic groups and groups of dental services.Methods: Prospective case-series cost analysis was conducted from the patient perspective. A six months time horizon was adopted. Sample size was 752 complete episodes of treatment in 250 patients, selected in 2012/2013 throughout several specialist state- and private-owned dental clinics in Serbia. All direct costs of dental care were taken into account and expressed in Euros (€.Results: Mean total costs of dental care were € 46 ± 156 per single dentist visit while total costs incurred by this population sample were € 34,424. Highest unit utilization of services belongs to conservative dentistry (31.9%, oral surgery (19.5% and radiology (17.4%, while the resource with the highest monetary value belongs to implantology € 828 ± 392, orthodontics € 706 ± 667 and prosthetics € 555 ± 244. The most frequently treated diagnosis was tooth decay (33.8% unit services provided, pulpitis (11.2% and impacted teeth (8.5%, while most expensive to treat were anomalies of tooth position (€ 648 ± 667, abnormalities of size and form of teeth (€ 508 ± 705 and loss of teeth due to accident, extraction or local periodontal disease (€ 336 ± 339.Conclusion: Although the range of dental costs currently falls behind EU average, Serbia’s emerging economy is likely to expand in the long run while market demand for dental services will grow. Due to threatened financial sustainability of current health insurance patterns in Western Balkans, getting acquainted with true size and structure of dental care costs could essentially support informed decision making in future

Dental Student Hand Hygiene Decreased With Increased Clinical Experience.

Science.gov (United States)

Yaembut, Nanmanas; Ampornaramveth, Ruchanee S; Pisarnturakit, Pagaporn P; Subbalekha, Keskanya

2016-01-01

To investigate the effectiveness, related knowledge, attitudes, and practices of hand hygiene (HH) among dental students with different levels of clinical experience. This was a cross-sectional analytical study. Bacterial samples on the participants' hands were obtained using a swab technique before and after handwashing, for oral surgical procedures. After culturing, the colony-forming units were counted. Self-reported questionnaires reflecting the knowledge, attitudes, and practices related to HH were completed by the participants. This study was performed in a primary oral health care institution, Faculty of Dentistry, Chulalongkorn University (Bangkok, Thailand). Bacterial samples and self-reported questionnaires were collected in the Department of Oral and Maxillofacial Surgery. Bacterial culture was performed in the Department of Microbiology. The 120 participants comprised first, second, third-year clinical training students (CTs), and postgraduate dental students (PGs) (32, 34, 30, and 24 participants, respectively). More than 99% of the bacteria were eliminated from the participants' hands after handwashing. Significantly higher numbers of bacteria were recovered from the hands of the PGs compared with those of the CTs, and the hands of the third-year CTs compared with those of the first-year CTs (p < 0.001), after HH. The first-year CTs had the highest attitude scores, whereas the PGs had the lowest practice scores. The knowledge scores were similar in all groups. HH effectiveness, attitudes, and practices of dental students decreased as students gained more clinical experience, whereas knowledge did not. Our results suggest that HH instruction should be given throughout the duration of dental students' education. Copyright © 2016 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

Assessment of empathy among clinical dental students in a teaching dental institution in Telangana State, India

Directory of Open Access Journals (Sweden)

V Siva Kalyan

2017-01-01

Full Text Available Introduction: The understanding of patient's view is considered as an important component in doctor–patient relationship. The health-care provider with an empathetic understanding may perceive patient's need as more reasonable and thus therapeutic. Aim: To assess empathy among clinical dental students in a teaching dental institution. Materials and Methods: A cross-sectional study was conducted among clinical dental students during the period between June 2016 and July 2016 in a teaching dental institution in Khammam town. Jefferson Scale of Empathy-Health Care Provider Student version was used to assess empathy among the students in this study. Gender differences were analyzed using t-test, and one-way ANOVA was used for comparison of empathy scores across year of study. P< 0.05 was considered statistically significant. Results: A total of 364 students participated in the study with a mean age of 22.76 ± 2.4 years. Males exhibited more empathy (86.54 ± 7 compared to females. The mean empathy level was found to be highest for the postgraduates (85.92 ± 6.5 followed by 3rd year students (P = 0.0943. Conclusion: There is a need to train these students not only from technical point of view but also in “life skills” such as communication, interpersonal relationship and empathy.

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...

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.

Dental diagnostic clinical instrument (Canary) development using photothermal radiometry and modulated luminescence

International Nuclear Information System (INIS)

Jeon, R J; Sivagurunathan, K; Garcia, J; Matvienko, A; Mandelis, A; Abrams, S

2010-01-01

Since 1999, our group at the CADIFT, University of Toronto, has developed the application of Frequency Domain Photothermal Radiometry (PTR) and Luminescence (LUM) to dental caries detection. Various cases including artificial caries detection have been studied and some of the inherent advantages of the adaptation of this technique to dental diagnostics in conjunction with modulated luminescence as a dual-probe technique have been reported. Based on these studies, a portable, compact diagnostic instrument for dental clinic use has been designed, assembled and tested. A semiconductor laser, optical fibers, a thermoelectric cooled mid-IR detector, and a USB connected data acquisition card were used. Software lock-in amplifier techniques were developed to compute amplitude and phase of PTR and LUM signals. In order to achieve fast measurement and acceptable signal-to-noise ratio (SNR) for clinical application, swept sine waveforms were used. As a result sampling and stabilization time for each measurement point was reduced to a few seconds. A sophisticated software interface was designed to simultaneously record intra-oral camera images with PTR and LUM responses. Preliminary results using this instrument during clinical trials in a dental clinic showed this instrument could detect early caries both from PTR and LUM signals.

Esthetic management of anterior dental anomalies: A clinical case.

Science.gov (United States)

Chafaie, Amir

2016-09-01

Many types of dental abnormality can be observed in the anterior sectors, where they can cause genuine esthetic problems for our patients. While conventional prosthetic treatments offer the best solutions in terms of esthetic result and durability, they involve the sacrifice of significant quantities of mineralized dental material and cannot be undertaken before the periodontal tissues are mature. Other less invasive alternatives should be envisaged as transitional, or sometimes even permanent, solutions for the management of these anomalies in children and adolescents. This article discusses these options and presents a clinical case where composite resin veneers and microabrasion of the enamel were used to treat dental agenesis and enamel dysplasia. Copyright © 2016 CEO. Published by Elsevier Masson SAS. All rights reserved.

SIC Industriemonitor najaar 2003

NARCIS (Netherlands)

Brouwer, N.; de Nooij, M.; Pomp, M.

2003-01-01

In juni 2000 publiceerde de Stichting voor Economisch Onderzoek (SEO) van de Universiteit van Amsterdam in opdracht van Stichting voor Industriebeleid en Communicatie (SIC) een ontwerp voor een SIC industriemonitor met een voorstel voor de inhoud en de structuur van een dergelijke monitor. Op dat

Designing the fiber volume ratio in SiC fiber-reinforced SiC ceramic composites under Hertzian stress

International Nuclear Information System (INIS)

Lee, Kee Sung; Jang, Kyung Soon; Park, Jae Hong; Kim, Tae Woo; Han, In Sub; Woo, Sang Kuk

2011-01-01

Highlights: → Optimum fiber volume ratios in the SiC/SiC composite layers were designed under Hertzian stress. → FEM analysis and spherical indentation experiments were undertaken. → Boron nitride-pyrocarbon double coatings on the SiC fiber were effective. → Fiber volume ratio should be designed against flexural stress. -- Abstract: Finite element method (FEM) analysis and experimental studies are undertaken on the design of the fiber volume ratio in silicon carbide (SiC) fiber-reinforced SiC composites under indentation contact stresses. Boron nitride (BN)/Pyrocarbon (PyC) are selected as the coating materials for the SiC fiber. Various SiC matrix/coating/fiber/coating/matrix structures are modeled by introducing a woven fiber layer in the SiC matrix. Especially, this study attempts to find the optimum fiber volume ratio in SiC fiber-reinforced SiC ceramics under Hertzian stress. The analysis is performed by changing the fiber type, fiber volume ratio, coating material, number of coating layers, and stacking sequence of the coating layers. The variation in the stress for composites in relation to the fiber volume ratio in the contact axial or radial direction is also analyzed. The same structures are fabricated experimentally by a hot process, and the mechanical behaviors regarding the load-displacement are evaluated using the Hertzian indentation method. Various SiC matrix/coating/fiber/coating/matrix structures are fabricated, and mechanical characterization is performed by changing the coating layer, according to the introduction (or omission) of the coating layer, and the number of woven fiber mats. The results show that the damage mode changes from Hertzian stress to flexural stress as the fiber volume ratio increases in composites because of the decreased matrix volume fraction, which intensifies the radial crack damage. The result significantly indicates that the optimum fiber volume ratio in SiC fiber-reinforced SiC ceramics should be designed for

Dose reference levels in Spanish intraoral dental radiology: stabilisation of the incorporation of digital systems in dental clinical practices

International Nuclear Information System (INIS)

Alcaraz, M.; Velasco, F.; Olivares, A.; Velasco, E.; Canteras, M.

2016-01-01

A total of 34 044 official quality assurance reports in dental radiodiagnostic surgery from 16 regions of Spain, compiled from 2002 to 2014, were studied in order to determine the progress of diagnostic reference levels (DRLs) for obtaining diagnostic images under normal conditions for clinical practice in Spanish dental clinics. A DRL of 2.8 mGy was set in 2014, which represents a 41.7 % decrease compared with that of 2002 (4.8 mGy). Over the same time period, the mean dose fell by 55.2 %. However, over the last 3 y, the stabilisation of the mean dose administered to patients has been observed with only a 6.7 % reduction in DRLs, which corresponds to the stabilisation of dental radiodiagnostic surgery on replacing the use of radiographic film with digital imaging systems. (authors)

Clinical audit of children with permanent tooth injuries treated at a dental hospital in Ireland.

LENUS (Irish Health Repository)

Stewart, C

2011-02-01

To audit key demographic and clinical factors relating to treatment of trauma to the permanent dentition at the Paediatric Dental Department, Cork University Dental School and Hospital, Ireland and to compare clinical management with guideline recommendations.

Pairing as an instructional strategy to promote soft skills amongst clinical dental students.

Science.gov (United States)

Abu Kasim, N H; Abu Kassim, N L; Razak, A A A; Abdullah, H; Bindal, P; Che' Abdul Aziz, Z A; Sulaiman, E; Farook, M S; Gonzalez, M A G; Thong, Y L; Ahmad, N A; Naimie, Z; Abdullah, M; Lui, J L; Abdul Aziz, A

2014-02-01

Training dentists today is challenging as they are expected to provide a wide range of dental care. In the provision of good dental care, soft skills are equally important as clinical skills. Therefore in dental education the development of soft skills are of prime concern. This study sought to identify the development of soft skills when dental students are paired in their clinical training. In this perception study, four open-ended items were used to elicit students' feedback on the appropriateness of using clinical pairing as an instructional strategy to promote soft skills. The most frequently cited soft skills were teamwork (70%) and communication (25%) skills. However, both negative and positive behaviours were reported. As for critical thinking and problem solving skills, more positive behaviours were reported for abilities such as to explain, analyze, find ideas and alternative solutions, and make decisions. Leadership among peers was not evident as leading without legitimate authority could be a hindrance to its development. If clinical pairing is to be used as an effective instructional strategy to promote soft skills amongst students, clear guidelines need to be developed to prepare students to work in a dental team and the use of appropriate assessment tools can facilitate the development of these soft skills. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Burnout Among the Clinical Dental Students in the Jordanian Universities

Science.gov (United States)

Amin, Wala Majid; Al-Ali, Muna H.; Duaibis, Ramzi B.; Oweis, Tamara; Badran, Darwish H.

2009-01-01

Background The study aimed to evaluate the level of burnout among the clinical dental students in two Jordanian universities. Methods A total of 307 students from the two schools were surveyed using Maslach Burnout Inventory survey. Scores for the inventory’s subscales were calculated and the mean values for the students’ groups were computed separately. Kruskal-Wallis and Mann-Whitney tests were carried out and the results were compared at 95% confidence level. Results The results showed that the dental students in both Jordanian universities suffered high levels of emotional exhaustion and depersonalization compared to reported levels for dental students in other countries. The dental students of the University of Jordan demonstrated a significantly higher (p < 0.05) level of emotional exhaustion than their counterparts in the Jordan University of Science and Technology. Conclusions The findings indicated that dental students in the Jordanian universities presented considerable degrees of burnout manifested by high levels of emotional exhaustion and depersonalization. Studies targeting students health and psychology should be carried out to determine the causes of burnout among dental students. The curricula of the dental schools in the two universities should be accordingly improved to minimize burnout among the students. Keywords Burnout; Emotional exhaustion; Depersonalization; Personal accomplishment; Maslach Burnout Inventory PMID:22461870

Developing an assessment in dental public health for clinical undergraduates attending a primary dental care outreach programme.

Science.gov (United States)

Holmes, R D; Waterhouse, P J; Maguire, A; Hind, V; Lloyd, J; Tabari, D; Lowry, R J

2011-02-01

This paper describes the development and implementation of a Dental Public Health (DPH) assessment within the Primary Dental Care Outreach (PDCO) course at Newcastle University. The assessment was piloted alongside the delivery of the Bachelor of Dental Surgery (BDS) curriculum in accordance with established learning outcomes. To design and implement a pilot summative assessment, incorporating patients' social histories obtained by undergraduate students attending primary dental care outreach clinics. Undergraduates were tasked with obtaining a detailed social history from a patient seen during their two-year outreach attachment. Each student submitted a written account of their patient's social history and placed this in context by researching a number of demographic and social variables centred upon their patient's home residence. The final component involved writing a concise case feature for a nominated newspaper based upon the case history, where students were encouraged to identify one or more public health messages using language appropriate to a lay readership. Seventy one clinical undergraduates (98.6% of the year-group) subsequently submitted all components of the assessment. Eighty six per cent of the year-group was deemed to have passed the assessment with 9.9% achieving a 'Merit' grade and 76% a 'Satisfactory' grade. Following the assessment, students and clinical teachers were asked for their feedback through a focus group for staff, and a brief feedback form for students. Undergraduates subsequently reported greater awareness of the significance and importance of obtaining a detailed social history and its relevance when devising appropriate and realistic treatment plans. © 2011 John Wiley & Sons A/S.

Clinical use of dental classification.

Science.gov (United States)

Jones, Gordon

2008-01-01

The Dental Classification system used by the uniformed services is supposed to predict the incidence of dental emergencies in the operational setting, at least on the unit level. Since most Sailors and Marines are deployed without close dental support, the sea services have adopted a policy of early treatment of class 3 dental conditions during recruit training. The other services are beginning to do the same. Recently, two factors have emerged that are affecting this early dental class 3 treatment. These factors must be considered when planning to provide early dental treatment. First, changing population and dentist provider demographics in the civilian sector are beginning to affect the class 3 treatment needs of incoming military recruits. Second, attrition from recruit training results in treatment provided to recruits who leave military service before finishing their training. Some view this as a waste of resources, others as a cost of doing business. As operational jointness increases, the three services must develop and use a single dental classification terminology, as well as unified standards and guidelines, both for better research in this area and for the readiness and well-being of our patients.

Patients' Perceptions of Dehumanization of Patients in Dental School Settings: Implications for Clinic Management and Curriculum Planning.

Science.gov (United States)

Raja, Sheela; Shah, Raveena; Hamad, Judy; Van Kanegan, Mona; Kupershmidt, Alexandra; Kruthoff, Mariela

2015-10-01

Although the importance of empathy, rapport, and anxiety/pain awareness in dentist-patient relations has been well documented, these factors continue to be an issue with patients in many dental school clinics. The aim of this study was to develop an in-depth understanding of how patients at an urban, university-affiliated medical center and its dental school's clinic experienced oral health care and to generate ideas for improving the dental school's clinical curriculum and management of the clinic. Although patient satisfaction surveys are common, in-depth patient narratives are an underutilized resource for improving dental education. In-depth qualitative interviews were conducted with 20 uninsured or underinsured dental patients at these sites, and the results were analyzed using content analysis. Major phenomena that participants discussed were the importance of empathy and good rapport with their oral health providers and provider awareness of dental pain and anxiety. Many patients also discussed feeling dehumanized during dental visits. Based on their positive and negative experiences, the participants made suggestions for how oral health professionals can successfully engage patients in treatment.

Computer-aided navigation in dental implantology: 7 years of clinical experience.

Science.gov (United States)

Ewers, Rolf; Schicho, Kurt; Truppe, Michael; Seemann, Rudolf; Reichwein, Astrid; Figl, Michael; Wagner, Arne

2004-03-01

This long-term study gives a review over 7 years of research, development, and routine clinical application of computer-aided navigation technology in dental implantology. Benefits and disadvantages of up-to-date technologies are discussed. In the course of the current advancement, various hardware and software configurations are used. In the initial phase, universally applicable navigation software is adapted for implantology. Since 2001, a special software module for dental implantology is available. Preoperative planning is performed on the basis of prosthetic aspects and requirements. In clinical routine use, patient and drill positions are intraoperatively registered by means of optoelectronic tracking systems; during preclinical tests, electromagnetic trackers are also used. In 7 years (1995 to 2002), 55 patients with 327 dental implants were successfully positioned with computer-aided navigation technology. The mean number of implants per patient was 6 (minimum, 1; maximum, 11). No complications were observed; the preoperative planning could be exactly realized. The average expenditure of time for the preparation of a surgical intervention with navigation decreased from 2 to 3 days in the initial phase to one-half day in clinical routine use with software that is optimized for dental implantology. The use of computer-aided navigation technology can contribute to considerable quality improvement. Preoperative planning is exactly realized and intraoperative safety is increased, because damage to nerves or neighboring teeth can be avoided.

Clinical and Individual Variables in Children's Dental Fear: A School-Based Investigation.

Science.gov (United States)

Silveira, Ethieli Rodrigues da; Goettems, Marília Leão; Demarco, Flávio Fernando; Azevedo, Marina Sousa

2017-01-01

This cross-sectional study evaluated the prevalence of dental fear and associated factors in schoolchildren aged 8 to 12 years old, in Pelotas, southern Brazil. Schoolchildren enrolled in 20 public and private schools were selected using a multi-stage sample design. Sociodemographic characteristics, children's dental visit and oral hygiene habits were assessed by questionnaires. The Dental Anxiety Question was used to measure dental fear prevalence. Children's clinical examination evaluated presence of dental caries (DMFT/dmft index) and gingival bleeding. Data were analyzed using Poisson regression with robust variance (prevalence ratio; 95% confidence interval). One thousand two hundred and two children were included. Dental fear prevalence was 24.6%. After the adjustment, girls [PR=1.71 (CI 95%: 1.31-2.22)], children from poorer families [PR=1.96 (CI 95%: 1.36-2.83)], those who had decayed teeth (D/d index>0)[PR=1.32 (CI 95%: 1.01-1.72), and who had never been at the dentist [PR=1.85 (CI 95%: 1.42-2.41) remained significantly associated with dental fear. The prevalence of dental fear indicates that it is a common problem among schoolchildren. Early dental care and dental caries prevention are important factors to prevent dental fear.

Experiences of clinical teaching for dental core trainees working in hospital.

Science.gov (United States)

Mannion, C J; Brotherton, P

2014-07-11

There is recognition that the provision of excellence in education and training results in a skilled and competent workforce. However, the educational experiences of dental core trainees (DCT's) working in the hospital oral and maxillofacial surgery (OMFS) setting have not been previously investigated. In this paper, we examine DCT's learning experiences both 'formal' and 'non-formal' within the hospital setting of ward and clinic-based teaching. Are hospital dental core trainees receiving a meaningful educational experience? To conclude this paper, the authors recommend methods, based upon sound educational principles, to maximise the value of clinical sessions for teaching.

SIC POVMs and Clifford groups in prime dimensions

International Nuclear Information System (INIS)

Zhu Huangjun

2010-01-01

We show that in prime dimensions not equal to 3, each group covariant symmetric informationally complete positive operator valued measure (SIC POVM) is covariant with respect to a unique Heisenberg-Weyl (HW) group. Moreover, the symmetry group of the SIC POVM is a subgroup of the Clifford group. Hence, two SIC POVMs covariant with respect to the HW group are unitarily or antiunitarily equivalent if and only if they are on the same orbit of the extended Clifford group. In dimension 3, each group covariant SIC POVM may be covariant with respect to three or nine HW groups, and the symmetry group of the SIC POVM is a subgroup of at least one of the Clifford groups of these HW groups, respectively. There may exist two or three orbits of equivalent SIC POVMs for each group covariant SIC POVM, depending on the order of its symmetry group. We then establish a complete equivalence relation among group covariant SIC POVMs in dimension 3, and classify inequivalent ones according to the geometric phases associated with fiducial vectors. Finally, we uncover additional SIC POVMs by regrouping of the fiducial vectors from different SIC POVMs which may or may not be on the same orbit of the extended Clifford group.

Clinical reasoning skills in final-year dental students: A qualitative cross-curricula comparison.

Science.gov (United States)

Nafea, E T; Dennick, R

2018-05-01

The aim of this research was to explore the perceptions of undergraduate dental students regarding clinical reasoning skills and also discover the influences of different curriculum designs on the acquisition of these skills by students. Eighteen final-year students from three different dental schools with varied curricula and cultures participated in the current research. The research used qualitative methodology. The study took place in 2013-2014. Interviews captured the participants' own understanding of clinical reasoning and its acquisition plus they "talked through" a clinical problem using a "think-aloud" technique. Thematic analysis was used to analyse the transcripts of the recorded interviews. Results obtained were related to curriculum structure. Unfamiliarity with the term clinical reasoning was common in students. Students from different schools used different strategies to reason when discussing clinical vignettes. Clinical reasoning process was dominated by pattern recognition. Students' behaviours seemed to be influenced by cultural factors. This research contributes to a greater understanding of how students learn, understand and apply dental clinical reasoning which will improve educational practices in the future. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

[Serial clinical examinations as the main approach to dental caries prevention in children].

Science.gov (United States)

Skripkina, G I; Garifullina, A Zh

2015-01-01

Leading scientific and organizational prerequisites for the feasibility of clinical examination of the entire child population of the Russian Federation to the dentist is, above all, the high prevalence and intensity of dental diseases in children of all ages. As a result of many years of research and follow-up of children of preschool and school age we have proved the need to distinguish a group of children with zero activity of dental caries. The referring criteria are determined according to the results of comprehensive clinical and laboratory examination in order to determine the degree of risk of dental caries and individual caries resistance. The age-specific risk group is settled by "Stop caries" software. In order to optimize the preventive activities children are divided in 5 groups for routine preventive dental care. Unfortunately the efforts of modern dental services aimed at eliminating the consequences of caries process by filling cavities. Individualized preventive approach will increase the effectiveness of preventive measures and save public funds allocated in the amount of compulsory health insurance for pediatric dentistry.

Visual presentation of a medical physiology seminar modifies dental students' perception of its clinical significance.

Science.gov (United States)

Vuletic, L; Spalj, S; Peros, K

2016-02-01

The primary objective of this study was to assess whether exposing dental students to visual stimuli related to dental profession during the medical physiology seminar could affect their perception of the clinical relevance of the topic. A self-administered questionnaire on attitudes towards medical physiology was conducted amongst 105 students of the School of Dental Medicine in Zagreb, Croatia, aged 19-24 years (80% females) following a seminar on respiratory system physiology. Power-point presentation accompanying the seminar for a total of 52 students (study group) was enriched with pictures related to dental practice in order to assess whether these pictures could make the topic appear more clinically relevant for a future dentist. The results of the survey indicated that dental students in the study group perceived the topic of the seminar as more important for them as future dentists when compared to the perception of the control group (P = 0.025). The results of this survey encourage physiology lecturers to present medical physiology as clinically relevant for dental students whenever possible as this could increase students' interest in the subject and their motivation for learning. Such an approach could be particularly beneficial if there is a significant time gap between basic courses and involvement of students into clinical training for it could promote meaningful learning. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Clinical usefulness of dental X-ray computed tomography for postoperative assessment of secondary alveolar bone grafting

International Nuclear Information System (INIS)

Noguchi, Kazuhide; Hamada, Yoshiki; Kondoh, Toshirou; Ishii, Hiroaki; Sonoyama, Tomoo; Kawarada, Takashi; Seto, Kanichi

2003-01-01

In this study, the clinical usefulness of dental X-ray computed tomography (CT) for postoperative assessment of secondary alveolar bone grafting was investigated. Nineteen bone-grafted alveolar clefts in 15 patients with cleft lip and palate were studied. All bone bridges were examined by dental three-dimensional (3D)-CT (PSR 9000: Asahi Roentgen, Kyoto, Japan). The postoperative 3D morphology of the bone bridges was easily recognized. Dental 3D-CT images were suggested to be useful for assessment before installation of dental implants in bone bridges. In addition, the status of bone surrounding the installed dental implants and the periodontal space of teeth adjacent to the cleft could be clearly evaluated. In conclusion, dental 3D-CT provides clinically valuable information for the postoperative assessment of secondary alveolar bone grafting. (author)

Research on SiC Whisker Prepared by H-PSO

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WANG Yao

2017-10-01

Full Text Available SiC whiskers were prepared on the matrix of graphite by using high hydrogenous silicone oil(PSO as raw material. The effect of surface conditions of graphite and heating temperature on the growth of SiC whisker was mainly studied in this paper. The main factor which affects the nucleation and growth of SiC whisker is the heating temperature, with the heating temperature rising, the production of SiC whisker increases. The surface condition of graphite matrix also influences the growth of SiC whisker. With the nucleation points provided by graphite matrix defects increasing, the production of SiC whisker incleases and SiC whisker starts to overlap with each other. The formation process of SiC whisker includes two steps:nucleation and growth. SiC whisker nucleates at low temperature and grows at high temperature, which follows the VLS (vapor-liquid-solid growth mechanism.

Forensic Luminol Blood Test for Preventing Cross-contamination in Dentistry: An Evaluation of a Dental School Clinic

OpenAIRE

Marcelo Carlos Bortoluzzi; Peterson Cadore; Andrea Gallon; Soraia Almeida Watanabe Imanishi

2014-01-01

Background: More than 200 different diseases may be transmitted from exposure to blood in the dental setting. The aim of this study is to identify possible faults in the cross-contamination chain control in a dental school clinic searching for traces of blood in the clinical contact surfaces (CCS) through forensic luminol blood test. Methods: Traces of invisible blood where randomly searched in CCS of one dental school clinic. Results: Forty eight surfaces areas in the CCS were tes...

Clinical and neurobiological effects of aerobic exercise in dental phobia: A randomized controlled trial.

Science.gov (United States)

Lindenberger, Brigitt L; Plag, Jens; Schumacher, Sarah; Gaudlitz, Katharina; Bischoff, Sophie; Bobbert, Thomas; Dimeo, Fernando; Petzold, Moritz B; Kirschbaum, Clemens; Dudás, Zsuzsa; Ströhle, Andreas

2017-11-01

Physical activity has shown to be effective in anxiety disorders. For specific phobia, no studies are available that systematically examined the effects of an aerobic exercise intervention on phobic fear within a randomized-controlled design. Therefore, we investigated the acute effect of a standardized aerobic training on clinical symptoms of dental phobia as well as on stress-related neurobiological markers. Within a crossover design, 30 patients with dental phobia (mean age: 34.1 years; mean score of the Dental Anxiety Scale: 18.8) underwent two minor dental interventions separated by 7 days. Dental treatment was performed after 30 min of physical activity at either 20% VO 2 max (control) or 70% VO 2 max (intervention), respectively. To control for habituation, patients were randomly assigned to one of the two conditions prior to the first intervention. Moreover, saliva samples were collected at five times in order to determine changes in salivary cortisol (sC) and alpha-amylase (sAA) due to treatment. In comparison to baseline, aerobic exercise within 70% VO 2 max significantly reduced clinical anxiety and sC concentrations before, during, and after the dental treatment. In contrast, the control condition led to decreased sAA levels at different time points of measurement. Habituation occurred at the second study day, independent of the order. Our study provides evidence for an effect of moderate-intense exercise on clinical symptoms and sC in patients with dental phobia. Therefore, acute aerobic exercise might be a simple and low-cost intervention to reduce disorder-specific phobic fear. © 2017 Wiley Periodicals, Inc.

Assessment of anxiety related to dental treatments among patients attending dental clinics and hospitals in Ranga Reddy District, Andhra Pradesh, India.

Science.gov (United States)

Prathima, Vedati; Anjum, M Shakeel; Reddy, P Parthasarathi; Jayakumar, A; Mounica, M

2014-01-01

To assess the levels of dental anxiety among patients anticipating dental treatments in dental clinics/hospitals of Ranga Reddy district. A cross-sectional study was conducted among a representative sample of 1200 subjects (at least 18 years old) in dental clinics/hospitals which were selected from a list obtained through systematic random sampling. The data were collected using a pre-tested and calibrated questionnaire consisting of the Modified Corah Dental Anxiety Scale (MDAS) to assess anxiety levels. The majority (52.4%) of subjects showed a low level of anxiety. Females (11.44 ± 4.41) were found to have higher mean MDAS scores than males, and the highest mean MDAS scores were found among 18- to 34-year-olds (11.28 ± 4.67) (P < 0.05). Significant differences were found among subjects anticipating different treatments, with higher MDAS scores for extraction (11.25 ± 5.4), followed by examination, root canal treatment, gum surgery, scaling, restoration and others, e.g. orthodontic treatment, restoration with crowns, bridges and dentures (7.79 ± 3.80). The highest mean MDAS scores were found among subjects who were apprehensive due to 'past difficult experience in dental treatments', followed by 'drill' and 'injection', with the lowest scores among subjects indicating 'other reasons' (7.82 ± 3.84). The present data show that anxiety levels are higher in patients who have to undergo extractions than those who must be fitted with dentures. Thus, dental health care providers should pay more attention to patients' anxiety levels associated with different types of treatment.

Effects of Rating Training on Inter-Rater Consistency for Developing a Dental Hygiene Clinical Rater Qualification System

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Jeong Ran Park

2007-12-01

Full Text Available We tried to develop itemized evaluation criteria and a clinical rater qualification system through rating training of inter-rater consistency for experienced clinical dental hygienists and dental hygiene clinical educators. A total of 15 clinical dental hygienists with 1-year careers participated as clinical examination candidates, while 5 dental hygienists with 3-year educations and clinical careers or longer participated as clinical raters. They all took the clinical examination as examinees. The results were compared, and the consistency of competence was measured. The comparison of clinical competence between candidates and clinical raters showed that the candidate group?占퐏 mean clinical competence ranged from 2.96 to 3.55 on a 5-point system in a total of 3 instruments (Probe, Explorer, Curet, while the clinical rater group?占퐏 mean clinical competence ranged from 4.05 to 4.29. There was a higher inter-rater consistency after education of raters in the following 4 items: Probe, Explorer, Curet, and insertion on distal surface. The mean score distribution of clinical raters ranged from 75% to 100%, which was more uniform in the competence to detect an artificial calculus than that of candidates (25% to 100%. According to the above results, there was a necessity in the operating clinical rater qualification system for comprehensive dental hygiene clinicians. Furthermore, in order to execute the clinical rater qualification system, it will be necessary to keep conducting a series of studies on educational content, time, frequency, and educator level.

Residual stresses and mechanical properties of Si3N4/SiC multilayered composites with different SiC layers

International Nuclear Information System (INIS)

Liua, S.; Lia, Y.; Chena, P.; Lia, W.; Gaoa, S.; Zhang, B.; Yeb, F.

2017-01-01

The effect of residual stresses on the strength, toughness and work of fracture of Si3N4/SiC multilayered composites with different SiC layers has been investigated. It may be an effective way to design and optimize the mechanical properties of Si3N4/SiC multilayered composites by controlling the properties of SiC layers. Si3N4/SiC multilayered composites with different SiC layers were fabricated by aqueous tape casting and pressureless sintering. Residual stresses were calculated by using ANSYS simulation, the maximum values of tensile and compressive stresses were 553.2MPa and −552.1MPa, respectively. Step-like fracture was observed from the fracture surfaces. Fraction of delamination layers increased with the residual stress, which can improve the reliability of the materials. Tensile residual stress was benefit to improving toughness and work of fracture, but the strength of the composites decreased. [es

Residual stresses and mechanical properties of Si3N4/SiC multilayered composites with different SiC layers; Las tensiones residuales y las propiedades mecánicas de compuestos multicapa de Si3N4/SiC con diferentes capas de SiC

Energy Technology Data Exchange (ETDEWEB)

Liua, S.; Lia, Y.; Chena, P.; Lia, W.; Gaoa, S.; Zhang, B.; Yeb, F.

2017-11-01

The effect of residual stresses on the strength, toughness and work of fracture of Si3N4/SiC multilayered composites with different SiC layers has been investigated. It may be an effective way to design and optimize the mechanical properties of Si3N4/SiC multilayered composites by controlling the properties of SiC layers. Si3N4/SiC multilayered composites with different SiC layers were fabricated by aqueous tape casting and pressureless sintering. Residual stresses were calculated by using ANSYS simulation, the maximum values of tensile and compressive stresses were 553.2MPa and −552.1MPa, respectively. Step-like fracture was observed from the fracture surfaces. Fraction of delamination layers increased with the residual stress, which can improve the reliability of the materials. Tensile residual stress was benefit to improving toughness and work of fracture, but the strength of the composites decreased. [Spanish] Se ha investigado el efecto de las tensiones residuales en la resistencia, dureza y trabajo de fractura de los compuestos multicapa de Si3N4/SiC con diferentes capas de SiC. Puede ser una manera eficaz de diseñar y optimizar las propiedades mecánicas de los compuestos multicapa de Si3N4/SiC mediante el control de las propiedades de las capas de SiC. Los compuestos multicapa de Si3N4/SiC con diferentes capas de SiC se fabricaron por medio de colado en cinta en medio acuoso y sinterización sin presión. Las tensiones residuales se calcularon mediante el uso de la simulación ANSYS, los valores máximos de las fuerzas de tracción y compresión fueron 553,2 MPa y −552,1 MPa, respectivamente. Se observó una fractura escalonada a partir de las superficies de fractura. La fracción de capas de deslaminación aumenta con la tensión residual, lo que puede mejorar la fiabilidad de los materiales. La fuerza de tracción residual era beneficiosa para la mejora de la dureza y el trabajo de fractura, pero la resistencia de los compuestos disminuyó.

Irradiation damage of SiC semiconductor device (I)

International Nuclear Information System (INIS)

Park, Ji Yeon; Kim, Weon Ju

2000-09-01

This report reviewed the irradiation damage of SiC semiconductor devices and examined a irradiation behavior of SiC single crystal as a pre-examination for evaluation of irradiation behavior of SiC semiconductor devices. The SiC single was crystal irradiated by gamma-beam, N+ ion and electron beam. Annealing examinations of the irradiated specimens also were performed at 500 deg C. N-type 6H-SiC dopped with N+ ion was used and irradiation doses of gamma-beam, N+ion and electron beam were up to 200 Mrad, 1x10 16 N + ions/cm 2 and 3.6 x 10 17 e/cm 2 and 1.08 x 10 18 e/cm 2 , respectively. Irradiation damages were analyzed by the EPR method. Additionally, properties of SiC, information about commercial SiC single crystals and the list of web sites with related to the SiC device were described in the appendix

Irradiation damage of SiC semiconductor device (I)

Energy Technology Data Exchange (ETDEWEB)

Park, Ji Yeon; Kim, Weon Ju

2000-09-01

This report reviewed the irradiation damage of SiC semiconductor devices and examined a irradiation behavior of SiC single crystal as a pre-examination for evaluation of irradiation behavior of SiC semiconductor devices. The SiC single was crystal irradiated by gamma-beam, N+ ion and electron beam. Annealing examinations of the irradiated specimens also were performed at 500 deg C. N-type 6H-SiC dopped with N+ ion was used and irradiation doses of gamma-beam, N+ion and electron beam were up to 200 Mrad, 1x10{sup 16} N{sup +} ions/cm{sup 2} and 3.6 x 10{sup 17} e/cm{sup 2} and 1.08 x 10{sup 18} e/cm{sup 2} , respectively. Irradiation damages were analyzed by the EPR method. Additionally, properties of SiC, information about commercial SiC single crystals and the list of web sites with related to the SiC device were described in the appendix.

The knowledge and attitude about HIV/AIDS among Jordanian dental students: (Clinical versus pre clinical students at the University of Jordan

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Shayyab Mohammad H

2011-06-01

Full Text Available Abstract Background The present study aimed to address the suspected deficiency in the level of understanding of HIV/AIDS among clinical and pre clinical dental students at the University of Jordan. In this cross-sectional study, structured questionnaires were distributed to fifth year dental students (n = 121 and to third year dental students (n = 144 in the academic year 2008/2009. Findings Significantly higher percentage of fifth-year students compared to third-year students felt that the teaching they received on cross-infection precautions and barrier dentistry was adequate (P Significantly higher proportion of third-year students compared to fifth-year (39.2% vs. 26.3% thought that HIV patients should be referred to other centers or support groups for treatment (P = 0.04. Conclusions The level of knowledge of Jordanian dental students about HIV and AIDS was generally acceptable; there were inadequacies, however, in their understanding regarding some aspects of AIDS epidemic which demands that dental school curriculum needs some improvement.

Matrix densification of SiC composites by sintering process

International Nuclear Information System (INIS)

Kim, Young-Wook; Jang, Doo-Hee; Eom, Jung-Hye; Chun, Yong-Seong

2007-02-01

The objectives of this research are to develop a process for dense SiC fiber-SiC composites with a porosity of 5% or less and to develop high-strength SiC fiber-SiC composites with a strength of 500 MPa or higher. To meet the above objectives, the following research topics were investigated ; new process development for the densification of SiC fiber-SiC composites, effect of processing parameters on densification of SiC fiber-SiC composites, effect of additive composition on matrix microstructure, effects of additive composition and content on densification of SiC fiber-SiC composites, mechanical properties of SiC fiber-SiC composites, effect of fiber coating on densification and strength of SiC fiber-SiC composites, development of new additive composition. There has been a great deal of progress in the development of technologies for the processing and densification of SiC fiber-SiC composites and in better understanding of additive-densification-mechanical property relations as results of this project. Based on the progress, dense SiC fiber-SiC composites (≥97%) and high strength SiC fiber-SiC composites (≥600 MPa) have been developed. Development of 2D SiC fiber-SiC composites with a relative density of ≥97% and a strength of ≥600 MPa can be counted as a notable achievement

Dental caries experience in 12-year-old schoolchildren in southeastern Brazil

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Silvia Cypriano

2008-08-01

Full Text Available The aim of this study was to evaluate the prevalence of caries-free children using DMFT and significant caries (SiC indexes in different caries prevalence groups in cities of the region of Campinas, São Paulo State, Brazil. The methodology proposed by the World Health Organization (1997 was used for caries diagnosis in 2,378 individuals. According to the DMFT index obtained in each evaluated city, 3 prevalence groups with representative samples were formed, being classified as low, moderate and high. SiC index was used to classify the one third of the population with the highest caries prevalence. In the low prevalence group, 32.4% of the children were caries free (DMFT=0, with mean DMFT of 2.29 and SiC index of 4.93. In the moderate prevalence group, 21.8% of the children were caries free, with mean DMFT of 3.36 and SiC of 6.74. Only 6.9% of the children in the high prevalence group were caries free and the mean DMFT was 5.54 (SiC=9.62. There was a great heterogeneity in dental caries distribution within the studied population, as well as a high caries prevalence considering the 3 classifications. Other indexes besides DMFT could be used to improve oral health assessment during establishment of the treatment plan and intervention.

An audit of dental prescriptions between clinics and dental laboratories.

Science.gov (United States)

Stewart, C A

2011-08-12

To discover the quality of written instructions from dentists to dental technicians and the nature of non-compliant prescriptions. An audit of laboratory prescription compliance was conducted within an NHS Trust Dental Teaching Hospital to determine the level of communication between dentists and dental technicians. One hundred and fifty prescriptions were audited from dental undergraduates and qualified dentists throughout the different departments. A total of two-thirds of prescriptions were considered non-compliant and failed to meet relevant ethical and legal guidelines. This problem was seen throughout all departments and at all professional levels. A breakdown in communication between dentists and technicians through the use of prescriptions is evident even within a close working environment.

Evaluation of Dental Status of Adolescents at Kuwait University Dental Clinic.

Science.gov (United States)

Ali, Dena A

2016-01-01

This study was designed to evaluate the dental status of adolescents initially presenting at Kuwait University Dental Clinic (KUDC). The purpose of this cross-sectional study was to evaluate (a) the prevalence of unrestored caries dentin among 12- to 16-year-old Kuwaiti residents, (b) the frequency of restorations extending into the inner half of the dentin, and (c) tooth loss pattern among this age group. Twelve- to 16-year-old patients who attended KUDC during the period January 2009 to December 2012 were included in this study. The total number of patients included in the study was 486; however, only 409 panoramic radiographs were available for evaluation. The Student t-test and one-way ANOVA were used for statistical analysis. The prevalence of unrestored dentin caries among 12- to 16-year-old patients was 52%. The frequency of deep restorations extending into the inner half of the dentin was 33%. Tooth loss was found in 8.0% of the sampled population. The most common missing tooth was the mandibular first molar followed by the mandibular second premolar and the maxillary first molar. There were no statistical differences between Kuwaiti and non-Kuwaiti residents regardless of gender; however, males had a slightly higher DMFT. The DMFT and DMFS values in this study were higher than in other studies. Despite the tremendous effort by the Kuwaiti government to improve oral health, comprehensive preventive strategies, dental treatment and maintenance of oral health are still necessary and must be reinforced in this age group.

Italian multicentre study on microbial environmental contamination in dental clinics: a pilot study.

Science.gov (United States)

Pasquarella, Cesira; Veronesi, Licia; Castiglia, Paolo; Liguori, Giorgio; Montagna, Maria Teresa; Napoli, Christian; Rizzetto, Rolando; Torre, Ida; Masia, Maria Dolores; Di Onofrio, Valeria; Colucci, Maria Eugenia; Tinteri, Carola; Tanzi, Marialuisa

2010-09-01

The dental practice is associated with a high risk of infections, both for patients and healthcare operators, and the environment may play an important role in the transmission of infectious diseases. A microbiological environmental investigation was carried out in six dental clinics as a pilot study for a larger multicentre study that will be performed by the Italian SItI (Society of Hygiene, Preventive Medicine and Public Health) working group "Hygiene in Dentistry". Microbial contamination of water, air and surfaces was assessed in each clinic during the five working days of the week, before and during treatments. Air and surfaces were also examined at the end of the daily activity. A wide variation was found in microbial environmental contamination, both within the participating clinics and relative to the different sampling times. Microbial water contamination in Dental Unit Water Systems (DUWS) reached values of up to 26x10(4)cfu/mL (colony forming units per millilitre). P. aeruginosa was found in 33% of the sampled DUWS and Legionella spp. in 50%. A significant decrease in the Total Viable Count (TVC) was recorded during the activity. Microbial air contamination showed the highest levels during dental treatments and tended to decrease at the end of the working activity (p<0.05). Microbial buildup on surfaces increased significantly during the working hours. As these findings point out, research on microbial environmental contamination and the related risk factors in dental clinics should be expanded and should also be based on larger collections of data, in order to provide the essential knowledge aimed at targeted preventive interventions. Copyright 2010 Elsevier B.V. All rights reserved.

Improved thermoelectric performance of CdO by adding SiC fibers versus by adding SiC nanoparticles inclusions

Science.gov (United States)

Liang, S.; Li, Longjiang

2018-03-01

We report the improved thermoelectric (TE) performance of CdO by alloying with SiC fibers. In contrast to the lowered thermoelectric figure of merit (ZT) in a CdO matrix with SiC nanoparticle composites, an appreciable ZT value increment of about 36% (from 0.32 to 0.435) at 1000 K was obtained in the CdO matrix with SiC fiber composites. Both kinds of composites show substantially decreased thermal conductivity due to additional phonon scattering by the nano-inclusions. Compared to the very high electrical resistivity (ρ ˜ 140 μΩ m) for 5 at. % SiC nanoparticle composites, SiC fiber composites favorably maintained a very low ρ (˜30 μΩ m) even with 5 at. % SiC at 1000 K. We think the substantial difference of specific surface areas of these two nano-inclusions (30 m2/g for fibers vs 300 m2/g for nanoparticles) might play a crucial role to fine tune the TE performance. Larger interface could be inductive to diffusion and electron acceptor activation, which affect carrier mobility considerably. This work might hint at an alternative approach to improve TE materials' performance.

75 FR 16511 - Pentron Clinical Technologies, a Wholly-Owned Subsidiary of Kerr Dental/Sybron Dental...

Science.gov (United States)

2010-04-01

... produce dental materials such as dental prosthetics, dental composites, dental impressions, dental... materials such as dental prosthetics, dental composites, dental impressions, dental adhesives, and other... Technologies, a Wholly-Owned Subsidiary of Kerr Dental/Sybron Dental Specialities, Formally Known as Customedix...

Dental diagnostic clinical instrument ('Canary') development using photothermal radiometry and modulated luminescence

Energy Technology Data Exchange (ETDEWEB)

Jeon, R J; Sivagurunathan, K; Garcia, J; Matvienko, A; Mandelis, A [Center for Advanced Diffusion Wave Technologies (CADIFT), Department of Mechanical and Industrial Engineering, University of Toronto, 5 King' s College Road, Toronto, Ontario, M5S 3G8 (Canada); Abrams, S, E-mail: mandelis@mie.utoronto.c [Quantum Dental Technologies, 748 Briar Hill Avenue, Toronto, Ontario, M6B 1L3 (Canada)

2010-03-01

Since 1999, our group at the CADIFT, University of Toronto, has developed the application of Frequency Domain Photothermal Radiometry (PTR) and Luminescence (LUM) to dental caries detection. Various cases including artificial caries detection have been studied and some of the inherent advantages of the adaptation of this technique to dental diagnostics in conjunction with modulated luminescence as a dual-probe technique have been reported. Based on these studies, a portable, compact diagnostic instrument for dental clinic use has been designed, assembled and tested. A semiconductor laser, optical fibers, a thermoelectric cooled mid-IR detector, and a USB connected data acquisition card were used. Software lock-in amplifier techniques were developed to compute amplitude and phase of PTR and LUM signals. In order to achieve fast measurement and acceptable signal-to-noise ratio (SNR) for clinical application, swept sine waveforms were used. As a result sampling and stabilization time for each measurement point was reduced to a few seconds. A sophisticated software interface was designed to simultaneously record intra-oral camera images with PTR and LUM responses. Preliminary results using this instrument during clinical trials in a dental clinic showed this instrument could detect early caries both from PTR and LUM signals.

Dynamics of the seasonal airborne propagation of Staphylococcus aureus in academic dental clinics.

Science.gov (United States)

Bernardo, Wagner Luiz de Carvalho; Silva, Jeferson Júnior da; Höfling, José Francisco; Rosa, Edvaldo Antônio Ribeiro; Boriollo, Marcelo Fabiano Gomes

2018-04-05

Staphylococcus aureus strains can be disseminated during dental treatments and occasionally lead to the contamination and infection of patients and dentists, which is an important public health problem. The dynamics of the airborne propagation and the genetic diversity of S. aureus isolated in an academic dental clinic environment were investigated using isoenzyme typing. Materials and MethodsThe isoenzymes of 44 previously reported isolates were obtained from fresh cultures and extracted using glass beads. Nine isoenzymes were investigated using multilocus enzyme electrophoresis (MLEE). The genetic diversity and relationship among the strains (electrophoretic type - ET) were determined using statistics previously described by Nei25 (1972) and the SAHN grouping method (UPGMA algorithm). Clonal pattern analyses indicated a high level of genetic polymorphism occurring among the 33 ETs, which were grouped into five taxa. Each taxon presented one or more clusters that were moderately related and that contained two or more identical/highly related isolates, revealing seasonal airborne propagation in these dental clinic environments. These data suggest the occurrence of active microevolutionary processes in S. aureus as well as the possibility of environmental propagation during a 14-month time span. Such findings are important to show that multiuser academic dental clinics can retain certain strains that are spreadable to different niches.

Trends in dental caries in Indian children for the past 25 years.

Science.gov (United States)

Mehta, Abhishek

2018-01-01

The economic liberalization which was started 25 years back in India has led to a rising gross domestic product and per capita income and a decline in poverty. There has been an improvement in various health status indicators in the Indian population. As oral health is an integral part of general health, a retrospective study was designed to assess the effect of economic liberalization on dental caries experience in Indian children. A systematic literature search was conducted to find studies done on dental caries prevalence in children in India from the year 1992-2016. Mesh and free text terms "child," "dental caries," and "India" were searched in databases - PubMed and PubMed Central. A total of 1468 titles were screened, out of which 191 articles were shortlisted for further inspection. Finally, 69 studies were found suitable for final analysis. The pooled caries prevalence was between 50.84% and 62.41% at 5-year interval. There was a decline in caries prevalence in 2-5 and 11-15 years of age group. The overall weighed mean of 2.4, 2.7, and 1.9 was observed in three different age groups. Significant caries index (SiC) of more than 3 was observed in all the age groups. The present review suggests that more than half of Indian children have been affected by dental caries. High SIC index score suggests a skewed distribution of caries among Indian children. This data may aid in planning further exploratory research and oral health care services for children by the stakeholders.

The Clinical Practice of Traditional and Nontraditional Dental Hygienists. Final Report.

Science.gov (United States)

Boyer, E. Marcia

Information is presented on a study designed to gather details about the services provided by clinical dental hygienists in traditional and nontraditional settings. The 10 research topics addressed include: services provided by the clinical RDH in the traditional and nontraditional setting; time allocated for such services; how patients are…

Clinical performance - a reflection of damage accumulation in ceramic dental crowns

Energy Technology Data Exchange (ETDEWEB)

Rekow, D.E. [Univ. of Medicine and Dentistry of New Jersey, Newark, NJ (United States). Dept. of Orthodontics; Thompson, V.P. [Univ. of Medicine and Dentistry of New Jersey, Newark, NJ (United States). New Jersey Dental School

2001-07-01

All-ceramic dental crowns have tremendous appeal for patients - their esthetics nearly match those of natural teeth. Unfortunately, the most esthetic materials are brittle and, consequently, are vulnerable to damage relating to shaping which is exacerbated during cyclic loading during normal chewing. Clinical performance of all-ceramic dental prostheses are directly dependent on damage introduced during fabrication and during fatigue loading associated with function. The accumulation of damage results in unacceptably high failure rates (where failure is defined as a complete fracture requiring replacement of the prosthesis). The relation between shaping damage and fatigue damage on clinical performance of all-ceramic dental crowns was investigated. Materials used commercially for all-ceramic crowns and investigated in this study included a series of different microstructures of machinable glass ceramics (Corning), aluminas and porcelains (Vita Zahnfabrik), and zirconia (Norton). As monolithic materials, strong, tough, fatigue-resistant materials are not sufficiently esthetic for crowns. Crowns fabricated from monolithic esthetic materials have high failure rates. Layering ceramics could provide acceptable strength through management of damage accumulation. (orig.)

Dental caries risk indicators in early childhood and their association with caries polarization in adolescence: a cross-sectional study.

Science.gov (United States)

Zemaitiene, Migle; Grigalauskiene, Ruta; Andruskeviciene, Vilija; Matulaitiene, Zivile Kristina; Zubiene, Jurate; Narbutaite, Julija; Slabsinskiene, Egle

2016-07-02

Based on the hypothesis that biological and social risks accumulate during life, it is important to identify possible dental caries risk indicators from the life course of early childhood and assess their association with caries polarization in adolescence. A cross-sectional design was applied to the study, and a multistage cluster sampling method used to draw a representative sample of 1063 18-year-old Lithuanian adolescents. The dental examinations were performed according to the methodology for oral status evaluation recommended by the World Health Organization. Parents of the participating adolescents completed a self-administered questionnaire about their children's life course during early childhood. The interdependence of characteristics was evaluated by chi-square (χ (2)) and Student's (t) criteria. A multivariate logistic regression model with the Significant Caries (SiC) index as an outcome was performed. The mean scores for the number of decayed, missing, and filled teeth (DMFT) and decayed teeth (DT) in the SiC positive group were higher than the corresponding values in the SiC negative group (6.14 [SD, 2.30] and 1.67 [SD, 2.02] vs 1.28 [SD, 1.11] and 0.34 [SD, 0.69], p caries risk indicators were identified that were independently associated with a SiC positive outcome: gender(OR = 1.32 [95 % CI: 1.01-1.73]), earlier eruption of the first primary tooth(OR = 1.43 [95 % CI: 1.03-1.97]), and past caries experience in the primary dentition (OR = 1.62 [95 % CI:1.22-2.14]). These study findings provide reliable evidence that gender, earlier eruption of the first primary tooth, and past caries experience in the primary dentition should be considered to be dental caries risk indicators and may have an adverse effect on caries polarization in adolescence.

Knowledge and attitude of Indian clinical dental students towards the dental treatment of patients with human immunodeficiency virus (HIV)/acquired immune-deficiency syndrome (AIDS).

Science.gov (United States)

Oberoi, Sukhvinder Singh; Marya, Charu Mohan; Sharma, Nilima; Mohanty, Vikrant; Marwah, Mohita; Oberoi, Avneet

2014-12-01

Oral health care of patients with human immunodeficiency virus (HIV)/acquired immune-deficiency syndrome (AIDS) is a growing area of concern. Information on HIV- and AIDS-related knowledge among dental students provides a crucial foundation for efforts aimed at developing an appropriate dental curriculum on HIV and AIDS. The purpose of this study was to assess the knowledge and attitude of Indian clinical dental students towards the treatment of patients with HIV/AIDS and perceived sources of information regarding HIV-related issues. Data were collected from clinical dental students (third year, fourth year and internship) from three dental institutions in Delhi National Capital Region (NCR). The questions assessed the knowledge and attitude towards treatment of patients with HIV and the perceived source of information related to HIV. The willingness to treat HIV-positive patients among dental students was 67.0%, and 74.20% were confident of treating a patient with HIV/AIDS. The potential problems in rendering treatment to these patients were effect on the attitude of other patients (49.90%) and staff fears (52.50%). The correct knowledge regarding the infection-control practice (barrier technique) was found among only 15.50% of respondents. The respondents had sufficient knowledge regarding the oral manifestations of HIV/AIDS. There was no correlation between the knowledge and attitude score, demonstrating a gap between knowledge and attitude among dental students regarding treatment of HIV-infected patients. Appropriate knowledge has to be delivered through the dental education curriculum, which can instil confidence in students about their ability to manage HIV-positive patients. © 2014 FDI World Dental Federation.

Forensic Luminol Blood Test for Preventing Cross-contamination in Dentistry: An Evaluation of a Dental School Clinic.

Science.gov (United States)

Bortoluzzi, Marcelo Carlos; Cadore, Peterson; Gallon, Andrea; Imanishi, Soraia Almeida Watanabe

2014-10-01

More than 200 different diseases may be transmitted from exposure to blood in the dental setting. The aim of this study is to identify possible faults in the crosscontamination chain control in a dental school clinic searching for traces of blood in the clinical contact surfaces (CCS) through forensic luminol blood test. Traces of invisible blood where randomly searched in CCS of one dental school clinic. Forty eight surfaces areas in the CCS were tested and the presence of invisible and remnant blood was identified in 28 (58.3%) items. We suggest that the luminol method is suitable for identifying contamination with invisible blood traces and this method may be a useful tool to prevent cross-contamination in the dental care setting.

Effect of inclusion of SiC particulates on the mechanical resistance behaviour of stir-cast AA6063/SiC composites

International Nuclear Information System (INIS)

Balasubramanian, I.; Maheswaran, R.

2015-01-01

Highlights: • AA6063/SiC composites with different weight percent are stir cast. • Resistance properties against indentation, stretching force and sliding force are studied. • Increase in initiation of cleavage facets and reduces the tensile strength for 15% SiC. • Transition from micro ploughing to micro cutting wear mechanism is less due to SiC inclusion. - Abstract: This study investigates the mechanical resistance behaviour of AA6063 particulate composites with the inclusion of micron-sized silicon carbide (SiC) particles with different weight percentages in an AA6063 aluminium matrix. AA6063/SiC particulate composites containing 0, 5, 10, and 15 weight percent of SiC particles were produced by stir casting. Standard mechanical tests were conducted on the composite plates, and the mechanical resistance to indentation, tensile force and sliding force are evaluated. It has been observed that upon addition of SiC particles, the resistance against indentation is increased and the resistance against tensile force is initially increased and then decreased. Furthermore, using scanning electron microscopy (SEM), the fracture appearance of the broken specimen subjected to tensile force and morphological changes in the surface subjected to sliding force are analysed. The SEM images reveal that the addition of SiC particles in the AA6063 aluminium matrix initiates more cleavage facets. This leads to brittle fracture in the specimen subjected to tensile forces and less transition from material displacement to material removal in the specimen subjected to sliding forces

Palladium assisted silver transport in polycrystalline SiC

Energy Technology Data Exchange (ETDEWEB)

Neethling, J.H., E-mail: Jan.Neethling@nmmu.ac.za [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); O' Connell, J.H.; Olivier, E.J. [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa)

2012-10-15

The transport of silver in polycrystalline 3C-SiC and hexagonal 6H-SiC has been investigated by annealing the SiC samples in contact with a Pd-Ag compound at temperatures of 800 and 1000 Degree-Sign C and times of 24 and 67 h. The Pd was added in an attempt to improve the low wetting of SiC by Ag and further because Pd is produced in measurable concentrations in coated particles during reactor operation. Pd is also known to coalesce at the IPyC-SiC interface and to chemically attack the SiC layer. SEM, TEM and EDS were used to show that the Ag penetrates polycrystalline SiC along grain boundaries together with Pd. It is suggested that Ag transport in SiC takes place along grain boundaries in the form of moving nodules consisting of a Ag-Pd mixture. It is assumed that the nodules move along grain boundaries by dissolving the SiC at the leading edge followed by the reprecipitation of SiC at the trailing edge. Since the solubility of Cs in Ag and Pd is extremely low, it is unlikely that Cs will penetrate the SiC together with the Ag-Pd compound if present at the IPyC-SiC interface. If it is assumed that the dominant transport mechanism of Ag in intact polycrystalline SiC is indeed the Pd assisted mechanism, then the stabilization of Pd (and other metallic fission products) in the kernel could be a way of mitigating Ag release from TRISO-coated particles.

Palladium assisted silver transport in polycrystalline SiC

International Nuclear Information System (INIS)

Neethling, J.H.; O’Connell, J.H.; Olivier, E.J.

2012-01-01

The transport of silver in polycrystalline 3C-SiC and hexagonal 6H-SiC has been investigated by annealing the SiC samples in contact with a Pd–Ag compound at temperatures of 800 and 1000 °C and times of 24 and 67 h. The Pd was added in an attempt to improve the low wetting of SiC by Ag and further because Pd is produced in measurable concentrations in coated particles during reactor operation. Pd is also known to coalesce at the IPyC–SiC interface and to chemically attack the SiC layer. SEM, TEM and EDS were used to show that the Ag penetrates polycrystalline SiC along grain boundaries together with Pd. It is suggested that Ag transport in SiC takes place along grain boundaries in the form of moving nodules consisting of a Ag–Pd mixture. It is assumed that the nodules move along grain boundaries by dissolving the SiC at the leading edge followed by the reprecipitation of SiC at the trailing edge. Since the solubility of Cs in Ag and Pd is extremely low, it is unlikely that Cs will penetrate the SiC together with the Ag–Pd compound if present at the IPyC–SiC interface. If it is assumed that the dominant transport mechanism of Ag in intact polycrystalline SiC is indeed the Pd assisted mechanism, then the stabilization of Pd (and other metallic fission products) in the kernel could be a way of mitigating Ag release from TRISO-coated particles.

Stem Cells of Dental Origin: Current Research Trends and Key Milestones towards Clinical Application

Directory of Open Access Journals (Sweden)

Athina Bakopoulou

2016-01-01

Full Text Available Dental Mesenchymal Stem Cells (MSCs, including Dental Pulp Stem Cells (DPSCs, Stem Cells from Human Exfoliated Deciduous teeth (SHED, and Stem Cells From Apical Papilla (SCAP, have been extensively studied using highly sophisticated in vitro and in vivo systems, yielding substantially improved understanding of their intriguing biological properties. Their capacity to reconstitute various dental and nondental tissues and the inherent angiogenic, neurogenic, and immunomodulatory properties of their secretome have been a subject of meticulous and costly research by various groups over the past decade. Key milestone achievements have exemplified their clinical utility in Regenerative Dentistry, as surrogate therapeutic modules for conventional biomaterial-based approaches, offering regeneration of damaged oral tissues instead of simply “filling the gaps.” Thus, the essential next step to validate these immense advances is the implementation of well-designed clinical trials paving the way for exploiting these fascinating research achievements for patient well-being: the ultimate aim of this ground breaking technology. This review paper presents a concise overview of the major biological properties of the human dental MSCs, critical for the translational pathway “from bench to clinic.”

Administrative and clinical denials by a large dental insurance provider

Directory of Open Access Journals (Sweden)

Geraldo Elias MIRANDA

2015-01-01

Full Text Available The objective of this study was to assess the prevalence and the type of claim denials (administrative, clinical or both made by a large dental insurance plan. This was a cross-sectional, observational study, which retrospectively collected data from the claims and denial reports of a dental insurance company. The sample consisted of the payment claims submitted by network dentists, based on their procedure reports, reviewed in the third trimester of 2012. The denials were classified and grouped into ‘administrative’, ‘clinical’ or ‘both’. The data were tabulated and submitted to uni- and bivariate analyses. The confidence intervals were 95% and the level of significance was set at 5%. The overall frequency of denials was 8.2% of the total number of procedures performed. The frequency of administrative denials was 72.88%, whereas that of technical denials was 25.95% and that of both, 1.17% (p < 0.05. It was concluded that the overall prevalence of denials in the studied sample was low. Administrative denials were the most prevalent. This type of denial could be reduced if all dental insurance providers had unified clinical and administrative protocols, and if dentists submitted all of the required documentation in accordance with these protocols.

Clinical Fit of Partial Removable Dental Prostheses Based on Alginate or Polyvinyl Siloxane Impressions.

NARCIS (Netherlands)

Fokkinga, W.A.; Witter, D.J.; Bronkhorst, E.M.; Creugers, N.H.J.

2017-01-01

PURPOSE: The aim of this study was to analyze the clinical fit of metal-frame partial removable dental prostheses (PRDPs) based on custom trays used with alginate or polyvinyl siloxane impression material. MATERIALS AND METHODS: Fifth-year students of the Nijmegen Dental School made 25 correct

A Qualitative Evaluation of Clinical Audit in UK Dental Foundation Training.

Science.gov (United States)

Thornley, Peter; Quinn, Alyson

2017-11-10

Clinical Audit (CA) has been recognized as a useful tool for tool for improving service delivery, clinical governance, and the education and performance of the dental team. This study develops the discussion by investigating its use as an educational tool within UK Dental Foundation Training (DFT). The aim was to investigate the views of Foundation Dentists (FDs) and Training Programme Directors (TPDs) on the CA module in their FD training schemes, to provide insight and recommendations for those supervising and undertaking CA. A literature review was conducted followed by a qualitative research methodology, using group interviews. The interviews were transcribed and thematically analyzed using NVIVO, a Computer-Assisted Qualitative Data Analysis tool. CA was found to be a useful tool for teaching management and professionalism and can bring some improvement to clinical practice, but TPDs have doubts about the long-term effects on service delivery. The role of the Educational Supervisor (ES) is discussed and recommendations are given for those supervising and conducting CA.

A Qualitative Evaluation of Clinical Audit in UK Dental Foundation Training

Directory of Open Access Journals (Sweden)

Peter Thornley

2017-11-01

Full Text Available Clinical Audit (CA has been recognized as a useful tool for tool for improving service delivery, clinical governance, and the education and performance of the dental team. This study develops the discussion by investigating its use as an educational tool within UK Dental Foundation Training (DFT. The aim was to investigate the views of Foundation Dentists (FDs and Training Programme Directors (TPDs on the CA module in their FD training schemes, to provide insight and recommendations for those supervising and undertaking CA. A literature review was conducted followed by a qualitative research methodology, using group interviews. The interviews were transcribed and thematically analyzed using NVIVO, a Computer-Assisted Qualitative Data Analysis tool. CA was found to be a useful tool for teaching management and professionalism and can bring some improvement to clinical practice, but TPDs have doubts about the long-term effects on service delivery. The role of the Educational Supervisor (ES is discussed and recommendations are given for those supervising and conducting CA.

Simulations of Proton Implantation in Silicon Carbide (SiC)

Science.gov (United States)

2016-03-31

Simulations of Proton Implantation in Silicon Carbide (SiC) Jonathan P. McCandless, Hailong Chen, Philip X.-L. Feng Electrical Engineering, Case...of implanting protons (hydrogen ions, H+) into SiC thin layers on silicon (Si) substrate, and explore the ion implantation conditions that are...relevant to experimental radiation of SiC layers. Keywords: silicon carbide (SiC); radiation effects; ion implantation ; proton; stopping and range of

Bulk Thermoelectric Materials Reinforced with SiC Whiskers

Science.gov (United States)

Akao, Takahiro; Fujiwara, Yuya; Tarui, Yuki; Onda, Tetsuhiko; Chen, Zhong-Chun

2014-06-01

SiC whiskers have been incorporated into Zn4Sb3 compound as reinforcements to overcome its extremely brittle nature. The bulk samples were prepared by either hot-extrusion or hot-pressing techniques. The obtained products containing 1 vol.% to 5 vol.% SiC whiskers were confirmed to exhibit sound appearance, high density, and fine-grained microstructure. Mechanical properties such as the hardness and fracture resistance were improved by the addition of SiC whiskers, as a result of dispersion strengthening and microstructural refinement induced by a pinning effect. Furthermore, crack deflection and/or bridging/pullout mechanisms are invoked by the whiskers. Regarding the thermoelectric properties, the Seebeck coefficient and electrical resistivity values comparable to those of the pure compound are retained over the entire range of added whisker amount. However, the thermal conductivity becomes large with increasing amount of SiC whiskers because of the much higher conductivity of SiC relative to the Zn4Sb3 matrix. This results in a remarkable degradation of the dimensionless figure of merit in the samples with addition of SiC whiskers. Therefore, the optimum amount of SiC whiskers in the Zn4Sb3 matrix should be determined by balancing the mechanical properties and thermoelectric performance.

Efficacy of panoramic radiography as a screening procedure in dental examination compared with clinical evaluation

International Nuclear Information System (INIS)

An, Seo Young; An, Chang Hyeon; Choi, Karp Shik

2007-01-01

To evaluate the efficacy of panoramic radiography by comparing the results of clinical examination with radiographic findings. We studied 190 patients (20 men and 170 women; mean age, 40 years; range, 22 to 68 years) who visited the health promotion center of Korea Medical Science Institute and were examined both clinically and by panoramic radiography. We compared results from both examinations. Treatment options by clinical examination were described as 'no treatment indicated', 'treatment of dental caries', 'removal of calculus', 'treatment of periodontal disease'. 'prothodonic treatment' and 'extraction of the third molar'. Findings taken from the panoramic radiography were: dental caries, peroapical lesion, alveolar bone loss, calculus deposition, retained root, impaction of the third molar, disease of maxillary sinus, bony change of mandibular condyle, etc. The prevalence of panoramic findings were: 37.9% of dental caries, 17.4% of periapical lesions, 44.7% of alveolar bone losses, 62.6% of calculi deposition. 7.9% of retained roots, 26.8% of third molar impactions, 6.3% of disease of maxillary sinus, 2.1% of bony changes of mandibular condlye and 35.8% of miscellaneous lesions. Abnormal conditions revealed by panoramic radiography which had not been discovered on clinical examination were: 24.2% of the patients had dental caries, 17.4% had periapical lesions, 7.4% had calculi deposition, 5.3% had retained roots, 15.3% had third molar impactions. The opposite cases were: 5.2% had dental caries, 12.6% had calculi deposition, and 9.5% had third molar impactions. The use of panoramic radiography as a supplement to the clinical examination might be a valuable screening technique

Efficacy of panoramic radiography as a screening procedure in dental examination compared with clinical evaluation

Energy Technology Data Exchange (ETDEWEB)

An, Seo Young; An, Chang Hyeon; Choi, Karp Shik [Kyungpook National Univ. School of Dentistry, Daegu (Korea, Republic of)

2007-06-15

To evaluate the efficacy of panoramic radiography by comparing the results of clinical examination with radiographic findings. We studied 190 patients (20 men and 170 women; mean age, 40 years; range, 22 to 68 years) who visited the health promotion center of Korea Medical Science Institute and were examined both clinically and by panoramic radiography. We compared results from both examinations. Treatment options by clinical examination were described as 'no treatment indicated', 'treatment of dental caries', 'removal of calculus', 'treatment of periodontal disease'. 'prothodonic treatment' and 'extraction of the third molar'. Findings taken from the panoramic radiography were: dental caries, peroapical lesion, alveolar bone loss, calculus deposition, retained root, impaction of the third molar, disease of maxillary sinus, bony change of mandibular condyle, etc. The prevalence of panoramic findings were: 37.9% of dental caries, 17.4% of periapical lesions, 44.7% of alveolar bone losses, 62.6% of calculi deposition. 7.9% of retained roots, 26.8% of third molar impactions, 6.3% of disease of maxillary sinus, 2.1% of bony changes of mandibular condlye and 35.8% of miscellaneous lesions. Abnormal conditions revealed by panoramic radiography which had not been discovered on clinical examination were: 24.2% of the patients had dental caries, 17.4% had periapical lesions, 7.4% had calculi deposition, 5.3% had retained roots, 15.3% had third molar impactions. The opposite cases were: 5.2% had dental caries, 12.6% had calculi deposition, and 9.5% had third molar impactions. The use of panoramic radiography as a supplement to the clinical examination might be a valuable screening technique.

Students' clinical learning in an emerging dental school: an investigation in international collaboration between Michigan and Ghana.

Science.gov (United States)

Peters, Mathilde C; Adu-Ababio, Francis; Jarrett-Ananaba, Nejay P; Johnson, Lynn A

2013-12-01

The dearth of dental faculty members is a widely known problem that is exacerbated in countries that are attempting to begin dental education programs. This collaboration between Kwame Nkrumah University of Science and Technology and the University of Michigan investigated if dental students who have just started their clinical dental education can learn the knowledge and skills required for identifying and restoring cavitated caries lesions through compact course delivery. There were three instructional blocks: 1) didactic seminar; 2) seminar, simulated hands-on skills instruction, and clinical observation/assisting with treatment of schoolchildren; and 3) seminar, simulated skills training, and application to schoolchildren. Each dental student completed a questionnaire measuring knowledge and perceptions of knowledge, experience, and confidence at five points in time. The dental students' knowledge increased significantly as well as their perceived knowledge, experience, and confidence (p<0.0001). In general, the students showed proficiency in delivering simple treatments. The project showed that an integrated compact course delivery model may assist emerging dental schools to cope with the challenging shortage of resident faculty members.

Patients' satisfaction with dental care provided by public dental ...

African Journals Online (AJOL)

Background: In Tanzania, patient satisfaction with dental services has received only minor attention. Objective: To assess patients' satisfaction with public dental health services in Dar es Salaam. Design: A cross-sectional study. Setting: Five public dental clinics randomly selected from a list of all the nine public dental ...

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...

The effect of abrading and cutting instruments on machinability of dental ceramics.

Science.gov (United States)

Sakoda, Satoshi; Nakao, Noriko; Watanabe, Ikuya

2018-03-16

The aim was to investigate the effect of machining instruments on machinability of dental ceramics. Four dental ceramics, including two zirconia ceramics were machined by three types (SiC, diamond vitrified, and diamond sintered) of wheels with a hand-piece engine and two types (diamond and carbide) of burs with a high-speed air turbine. The machining conditions used were abrading speeds of 10,000 and 15,000 r.p.m. with abrading force of 100 gf for the hand-piece engine, and a pressure of 200 kPa and a cutting force of 80 gf for the air-turbine hand-piece. The machinability efficiency was evaluated by volume losses after machining the ceramics. A high-abrading speed had high-abrading efficiency (high-volume loss) compared to low-abrading speed in all abrading instruments used. The diamond vitrified wheels demonstrated higher volume loss for two zirconia ceramics than those of SiC and diamond sintered wheels. When the high-speed air-turbine instruments were used, the diamond points showed higher volume losses compared to the carbide burs for one ceramic and two zirconia ceramics with high-mechanical properties. The results of this study indicated that the machinability of dental ceramics depends on the mechanical and physical properties of dental ceramics and machining instruments. The abrading wheels show autogenous action of abrasive grains, in which ground abrasive grains drop out from the binder during abrasion, then the binder follow to wear out, subsequently new abrasive grains come out onto the instrument surface (autogenous action) and increase the grinding amount (volume loss) of grinding materials.

Grafted SiC nanocrystals

DEFF Research Database (Denmark)

Saini, Isha; Sharma, Annu; Dhiman, Rajnish

2017-01-01

), raman spectroscopy and X-ray diffraction (XRD) measurements. UV–Visible absorption spectroscopy was used to study optical properties such as optical energy gap (Eg), Urbach's energy (Eu), refractive index (n), real (ε1) and imaginary (ε2) parts of dielectric constant of PVA as well as PVA......Polyvinyl alcohol (PVA) grafted SiC (PVA-g-SiC)/PVA nanocomposite was synthesized by incorporating PVA grafted silicon carbide (SiC) nanocrystals inside PVA matrix. In-depth structural characterization of resulting nanocomposite was carried out using fourier transform infrared spectroscopy (FTIR...

Pattern of dental caries in Mulago Dental School clinic, Uganda ...

African Journals Online (AJOL)

Information on dental caries among patients attending Mulago Hospital is scarce. Yet knowledge of the pattern of caries can be used to plan preventive and treatment interventions. This study describes the pattern of dental caries (in terms of age group, tooth and tooth surface and gender) among patients attending the ...

SiC Power MOSFET with Improved Gate Dielectric

Energy Technology Data Exchange (ETDEWEB)

Sbrockey, Nick M. [Structured Materials Industries, Inc., Piscataway, NJ (United States); Tompa, Gary S. [Structured Materials Industries, Inc., Piscataway, NJ (United States); Spencer, Michael G. [Structured Materials Industries, Inc., Piscataway, NJ (United States); Chandrashekhar, Chandra M.V. S. [Structured Materials Industries, Inc., Piscataway, NJ (United States)

2010-08-23

In this STTR program, Structured Materials Industries (SMI), and Cornell University are developing novel gate oxide technology, as a critical enabler for silicon carbide (SiC) devices. SiC is a wide bandgap semiconductor material, with many unique properties. SiC devices are ideally suited for high-power, highvoltage, high-frequency, high-temperature and radiation resistant applications. The DOE has expressed interest in developing SiC devices for use in extreme environments, in high energy physics applications and in power generation. The development of transistors based on the Metal Oxide Semiconductor Field Effect Transistor (MOSFET) structure will be critical to these applications.

Synthesis of whiskers of SiC microwave assisted; Sintesis de whiskers de SiC asistida por microondas

Energy Technology Data Exchange (ETDEWEB)

Garza-Mendez, F. J.; Vanegas, A. J.; Vazquez, B. A.; Garza-Paz, J.

2013-06-01

We developed a new process for the synthesis of SiC whiskers assisted by microwaves; this is based on the mixture of silica xerogels and graphite powder. As energy source were used microwaves of 2.45 GHz and 1.0 kW of power RMS. On the other hand, mesoporous silica was synthesized via sol-gel, the precursors used were TEOS/H{sub 2}O and ethanol. Through analysis of the BET is determined the value of average pore size (3.0 nm) and the surface area (1090 m2/g).By mean of X-Ray diffraction it was demonstrated that the silica obtained is an amorphous solid and, the powders obtained in the microwave synthesis are {beta}-SiC. Synthesized SiC powders were observed using a SEM in secondary electron mode, it was observed that this powders consists of SiC whiskers. The effect of microwaves on the synthesis of whiskers of SiC is discussed in the present work. (Author) 19 refs.

D-region ion-neutral coupled chemistry (Sodankylä Ion Chemistry, SIC) within the Whole Atmosphere Community Climate Model (WACCM 4) - WACCM-SIC and WACCM-rSIC

Science.gov (United States)

Kovács, Tamás; Plane, John M. C.; Feng, Wuhu; Nagy, Tibor; Chipperfield, Martyn P.; Verronen, Pekka T.; Andersson, Monika E.; Newnham, David A.; Clilverd, Mark A.; Marsh, Daniel R.

2016-09-01

This study presents a new ion-neutral chemical model coupled into the Whole Atmosphere Community Climate Model (WACCM). The ionospheric D-region (altitudes ˜ 50-90 km) chemistry is based on the Sodankylä Ion Chemistry (SIC) model, a one-dimensional model containing 307 ion-neutral and ion recombination, 16 photodissociation and 7 photoionization reactions of neutral species, positive and negative ions, and electrons. The SIC mechanism was reduced using the simulation error minimization connectivity method (SEM-CM) to produce a reaction scheme of 181 ion-molecule reactions of 181 ion-molecule reactions of 27 positive and 18 negative ions. This scheme describes the concentration profiles at altitudes between 20 km and 120 km of a set of major neutral species (HNO3, O3, H2O2, NO, NO2, HO2, OH, N2O5) and ions (O2+, O4+, NO+, NO+(H2O), O2+(H2O), H+(H2O), H+(H2O)2, H+(H2O)3, H+(H2O)4, O3-, NO2-, O-, O2, OH-, O2-(H2O), O2-(H2O)2, O4-, CO3-, CO3-(H2O), CO4-, HCO3-, NO2-, NO3-, NO3-(H2O), NO3-(H2O)2, NO3-(HNO3), NO3-(HNO3)2, Cl-, ClO-), which agree with the full SIC mechanism within a 5 % tolerance. Four 3-D model simulations were then performed, using the impact of the January 2005 solar proton event (SPE) on D-region HOx and NOx chemistry as a test case of four different model versions: the standard WACCM (no negative ions and a very limited set of positive ions); WACCM-SIC (standard WACCM with the full SIC chemistry of positive and negative ions); WACCM-D (standard WACCM with a heuristic reduction of the SIC chemistry, recently used to examine HNO3 formation following an SPE); and WACCM-rSIC (standard WACCM with a reduction of SIC chemistry using the SEM-CM method). The standard WACCM misses the HNO3 enhancement during the SPE, while the full and reduced model versions predict significant NOx, HOx and HNO3 enhancements in the mesosphere during solar proton events. The SEM-CM reduction also identifies the important ion-molecule reactions that affect the partitioning of

Predicting Anxiety Among Patients In LPU Clinical Dispensary During Dental Treatment: Towards Student’s Clinical Performance Enhancement

Directory of Open Access Journals (Sweden)

Maribel D. Mayuga-Barrion

2013-12-01

Full Text Available The study aimed to determine the respondents’ profile in terms of age, gender, frequency of dental visit, and type of patient whether dental phobic or not; to determine the dental anxiety of patients in LPU dental dispensary; to identify the causes and severity of anxiety of the patients in LPU dental dispensary; to determine if there is a significant difference between the respondents’ demographic profile and their level of anxiety; and lastly, to propose a program that will help the patients cope with dental anxiety and a program that will enhance the students’ clinical performance. The study used the descriptive research design with the combination of content analysis of documents and related materials. Results showed that majority of the respondents belonged to age range of 14-18 years old range whereas for gender or sex, majority who avail of the clinic’s services are males. This is because women are more afraid than men in terms of dental problems. Further, younger people are more afraid than older ones. The weighted mean distribution of the level of anxiety showed that the level of anxiety of patients varies on moderately to not anxious. Feeling or experiencing pain during dental treatment ranked first followed by the fear or worry of not working the proposed treatment and thirdly, the dentist is in a hurry while treating also made the patients moderately anxious. Overall, the level of anxiety of patients is moderately anxious. Probing to asses gum disease, dislike the numb feeling and injection were the top three causes of dental anxiety. Only type of patient shows significant difference, thus the null hypothesis of no significant difference on the level of anxiety when grouped according to profile variables is rejected. This means that the level of anxiety of both phobic and not phobic differs.

How a modified approach to dental coding can benefit personal and professional development with improved clinical outcomes.

Science.gov (United States)

Lam, Raymond; Kruger, Estie; Tennant, Marc

2014-12-01

One disadvantage of the remarkable achievements in dentistry is that treatment options have never been more varied or confusing. This has made the concept of Evidenced Based Dentistry more applicable to modern dental practice. Despite merit in the concept whereby clinical decisions are guided by scientific evidence, there are problems with establishing a scientific base. This is no more challenging than in modern dentistry where the gap between rapidly developing products/procedures and its evidence base are widening. Furthermore, the burden of oral disease continues to remain high at the population level. These problems have prompted new approaches to enhancing research. The aim of this paper is to outline how a modified approach to dental coding may benefit clinical and population level research. Using publically assessable data obtained from the Australian Chronic Disease Dental Scheme and item codes contained within the Australian Schedule of Dental Services and Glossary, a suggested approach to dental informatics is illustrated. A selection of item codes have been selected and expanded with the addition of suffixes. These suffixes provided circumstantial information that will assist in assessing clinical outcomes such as success rates and prognosis. The use of item codes in administering the CDDS yielded a large database of item codes. These codes are amenable to dental informatics which has been shown to enhance research at both the clinical and population level. This is a cost effective method to supplement existing research methods. Copyright © 2014 Elsevier Inc. All rights reserved.

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.

Influence of defects in SiC (0001) on epitaxial graphene

International Nuclear Information System (INIS)

Guo Yu; Guo Li-Wei; Lu Wei; Huang Jiao; Jia Yu-Ping; Sun Wei; Li Zhi-Lin; Wang Yi-Fei

2014-01-01

Defects in silicon carbide (SiC) substrate are crucial to the properties of the epitaxial graphene (EG) grown on it. Here we report the effect of defects in SiC on the crystalline quality of EGs through comparative studies of the characteristics of the EGs grown on SiC (0001) substrates with different defect densities. It is found that EGs on high quality SiC possess regular steps on the surface of the SiC and there is no discernible D peak in its Raman spectrum. Conversely, the EG on the SiC with a high density of defects has a strong D peak, irregular stepped morphology and poor uniformity in graphene layer numbers. It is the defects in the SiC that are responsible for the irregular stepped morphology and lead to the small domain size in the EG. (rapid communication)

Surgical templates for dental implant positioning; current knowledge and clinical perspectives

Directory of Open Access Journals (Sweden)

Mohammed Zaheer Kola

2015-01-01

Full Text Available Dental implants have been used in a variety of different forms for many years. Since the mid-20 th century, there has been an increase in interest in the implant process for the replacement of missing teeth. Branemark was one of the initial pioneers who applied scientifically based research techniques to develop an endosseous implant that forms an immobile connection with bone. The need for a dental implant to completely address multiple physical and biological factors imposes tremendous constraints on the surgical and handling protocol. Metallic dental implants have been successfully used for decades, but they have serious shortcomings related to their bony union and the fact that their mechanical properties do not match those of bone. However, anatomic limitation and restorative demands encourage the surgeon to gain precision in planning and surgical positioning of dental implants. Ideal placement of the implant facilitates the establishment of favorable forces on the implants and the prosthetic component as well as ensures an aesthetic outcome. Therefore, it is advisable to establish a logical continuity between the planned restoration and the surgical phases, it is essential to use a transfer device that for sure increases the predictability of success. The surgical guide template is fabricated by a dental technician after the presurgical restorative appointments that primarily include determination of occlusal scheme and implant angulations. Here, authors genuinely attempted to review the evolution and clinical applicability of surgical templates used in the placement of dental implants.

Impact of the University of Colorado's Advanced Clinical Training and Service (ACTS) Program on dental students' clinical experience and cognitive skills, 1994-2006.

Science.gov (United States)

Berg, Rob; Call, Richard L; Maguire, Kerry; Berkey, Douglas B; Karshmer, Bernard A; Guyton, Brad; Tawara-Jones, Karen

2010-04-01

The University of Colorado Denver School of Dental Medicine has operated a community-based dental education program for all of its students since 1985. A database of student productivity has been maintained in a standardized format, capable of multiyear compilation, since 1994. This study utilizes twelve years of these data to profile the type and amount of clinical treatment that can be provided by a typical fourth-year dental student during a 100-day community-based training experience. Between 1994 and 2006, the school's 423 graduates provided a mean of 922 treatment procedures per student at a mean of 498 patient visits per student. During a typical four-week clinical affiliation, each student provided a mean of approximately twenty-seven restorations on permanent teeth, sixteen restorations on primary teeth, and twenty-four oral surgery procedures (extractions). Students also gained considerable experience in periodontics, fixed and removable prosthodontics, and endodontics. Self-assessed competency ratings tended to increase after completing the program, as did willingness to treat underserved populations after graduation. About 16 percent of graduates reported planning to practice in the public sector after completing dental school. A community-based experience such as this appears to offer an opportunity to substantially augment dental students' clinical training experiences.

A community of learners in the evidence-based dental clinic

NARCIS (Netherlands)

Schoonheim-Klein, M.; Wesselink, P.R.; Vervoorn, J.M.

2012-01-01

An increasing emphasis has been placed on the need for an evidence-based approach in dentistry. This calls for effort in dental education to develop and implement tools for the application of evidence in clinical decision-making (evidence-based decision-making, EBDM). Aim:  To evaluate whether the

Some insights for a relationship marketing model integrating SERVQUAL and customer loyalty in dental clinics

OpenAIRE

Vargas Perez, Ana Maria; Grijalvo Martin, Maria Mercedes; Mercado Idoeta, Carmelo

2012-01-01

The demand of new services, the emergence of new business models, insufficient innovation, underestimation of customer loyalty and reluctance to adopt new management are evidence of the deficiencies and the lack of research about the relations between patients and dental clinics. In this article we propose the structure of a model of Relationship Marketing (RM) in the dental clinic that integrates information from SERVQUAL, Customer Loyalty (CL) and activities of RM and combines the vision of...

Awareness of dental implants among dental patients in Nigeria ...

African Journals Online (AJOL)

The aim of this study was to determine the level of awareness of dental implant in Nigerian patients and their willingness to choose dental implant as a tooth replacement option. A survey was conducted among patients presenting for dental treatment in 3 teaching hospitals and private dental clinics in 3 urban cities of ...

[Application of Raman spectroscopy to investigation of CVD-SIC fiber].

Science.gov (United States)

Liu, Bin; Yang, Yan-Qing; Luo, Xian; Huang, Bin

2011-11-01

The CVD-SiC fiber was studied by using laser Raman spectra. It was found that the sharp TO peak exists in the first SiC deposit layer, indicating the larger SiC grains. But the second SiC deposit layer is with small grains. Raman peak of carbon and silicon was detected respectively in the first and second layer. Compared with that of the single SiC fiber, the TO peaks move to the high wave number for the SiC fiber in SiC(f)/Ti-6Al-4V composite. It indicates that the compressive thermal residual stress is present in the SiC fiber during the fabrication of the composite because of the mismatched coefficient of thermal expansion between Ti-6Al-4V matrix and SiC fiber. The average thermal residual stress of the SiC fiber in SiC(f)/Ti-6Al-4V composite was calculated to be 318 MPa and the residual stress in first deposit layer is 436 MPa which is much higher than that in the second layer.

Clinical aspects and conservative dental management of a patient with fibrodysplasia ossificans progressiva.

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Oliveira, Francisco Artur Forte; Fernandes, Clarissa Pessoa; Araujo, Kenia Samara Barbosa; Alves, Ana Paula Negreiros Nunes; Sousa, Fabrício Bitu; Mota, Mário Rogério Lima

2014-01-01

T o present the clinical findings of a patient with fibrodysplasia ossificans progressiva (FOP), highlighting peculiarities of dental treatment in patients with this condition. FOP is a rare genetic disease characterized by skeletal malformations and ectopic ossifications in skeletal muscles, tendons, ligaments and aponeurosis. Exacerbation of these ossifications can be caused by dental treatment, resulting in disease progression. A 26-year-old male patient with a diagnosis of FOP was referred to our service for dental treatment. The patient presented decreased mobility in peripheral joints (knees and elbows), postural disability (ankylosis of the vertebral column), lateral deviation and shortness of the hallux, as well as heterotopic ossifications on the hands and back. The implementation of conservative dental procedures, such as oral hygiene instructions and recurrent topical fluoride applications, were performed in addition to endodontic and restorative treatments. Brief dental appointments were conducted without using regional anesthesia or dental dam clamps. The dental chair was positioned at 45° to provide more comfort and to avoid exacerbating the disease. The patient has now completed 6 months of follow-up and is free of heterotopic ossifications resulting from dental treatment. The dental treatment modifications implemented for the present case were sufficient to establish good oral health and to prevent the formation of heterotopic ossifications in the maxillofacial region. FOP is a rare disease dentists must familiarize themselves with to provide adequate, personalized treatment, which minimizes traumas that may exacerbate the disease.

Dental anxiety reduction and dental attendance after treatment in a dental fear clinic: A follow-up study.

NARCIS (Netherlands)

Aartman, I.H.A.; de Jongh, A.; Makkes, P.C.; Hoogstraten, J.

2000-01-01

The aim of the present study was to assess treatment outcome in terms of dental anxiety reduction at a post-treatment assessment and dental anxiety reduction and dental attendance one year later. Furthermore, it was determined to what extent psychopathological characteristics were related to

Instructor and Dental Student Perceptions of Clinical Communication Skills via Structured Assessments.

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McKenzie, Carly T

2016-05-01

The aim of this study was to use structured assessments to assess dental students' clinical communication skills exhibited during patient appointments. Fourth-year dental students (n=55) at the University of Alabama at Birmingham evaluated their own interpersonal skills in a clinical setting utilizing the Four Habits Coding Scheme. An instructor also assessed student-patient clinical communication. These assessments were used to identify perceived strengths and weaknesses in students' clinical communication. Both instructor assessments and student self-assessments pinpointed the following clinical communication skills as effective the most often: patient greeting, avoidance of jargon, and non-verbal behavior. There was also relative agreement between instructor assessments and student self-assessments regarding clinical communication skills that were rated as not effective most frequently: ensuring patient comprehension, identification of patient feelings, and exploration of barriers to treatment. These resulted pointed to strengths and weaknesses in the portion of the curriculum designed to prepare students for effective provider-patient communication. These results may suggest a need for the school's current behavioral science curriculum to better address discussion of potential treatment barriers and patient feelings as well as techniques to ensure patient comprehension.

Dental anomalies in 14 patients with IP: clinical and radiological analysis and review.

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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.

Cultural competency and communication skills of dental students: clinical supervisors' perceptions.

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Mariño, R; Ghanim, A; Morgan, M; Barrow, S

2017-11-01

This study explored clinical supervisor's (CS) views and experiences of dental students' cultural competence (CC) at the Melbourne Dental School, The University of Melbourne, Australia. Additionally, this study explored CS insights into how CC could be taught. Semi-structured one-to-one interviews were organised with consenting CS. Interview topics included the following: the importance of CC, communication and rapport, the role of culture in oral health and the need for curriculum enhancement. Interviews were recorded, transcribed and thematically analysed to identify key areas using NVivo software. A total of 12 CS participated in this study. CS acknowledged the importance of CC and felt that it was important for good patient management. CS's definition of CC focused primarily on language and communication skills. CS felt that dental students were generally able to manage culturally diverse patients. However, CS indicated that additional training in this area would be beneficial. Concerns were raised about the students' ability to establish good rapport and communication, with CS highlighting areas such as misuse of interpreters and use of jargon. CS felt that clinical experience, confidence and a positive attitude are effective tools for overcoming cultural barriers. Furthermore, some CS also felt that cultural competency was a skill that is learnt through experience. For most CS, cultural competence was an important part of the clinician-patient exchange which would benefit from enhanced curriculum. They also highlighted areas where transcultural education could be improved. The majority of CS believed dental students managed culturally diverse patients well. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Important considerations for designing and reporting epidemiologic and clinical studies in dental traumatology

DEFF Research Database (Denmark)

Andersson, Lars; Andreasen, Jens O

2011-01-01

The purpose of this article is to suggest important considerations for epidemiologic and clinical studies in the field of dental traumatology. The article is based on the authors' experiences from research in this field and editorial board work for the scientific journal Dental Traumatology....... Examples are given of issues where development is important. The importance of planning ahead of the study and consulting with experts in other fields is emphasized....

SiC as an oxidation-resistant refractory material. Pt. 1

International Nuclear Information System (INIS)

Schlichting, J.

1979-01-01

Uses his own investigations and gives a literature survey on the oxidation and corrosion behaviour of SiC (in the form of a pure SiC powder, hot-pressed and reaction-sintered materials). The excellent stability of SiC in oxidizing atmosphere is due to the development of protective SiO 2 coatings. Any changes in these protective coatings (e.g. due to impurities with corrosive media, high porosity of SiC, etc.) lead in most cases to increased rates of oxidation and thus restrict the field of application of SiC. (orig.) [de

Predicting academic performance and clinical competency for international dental students: seeking the most efficient and effective measures.

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Stacey, D Graham; Whittaker, John M

2005-02-01

Measures used in the selection of international dental students to a U.S. D.D.S. program were examined to identify the grouping that most effectively and efficiently predicted academic performance and clinical competency. Archival records from the International Dental Program (IDP) at Loma Linda University provided data on 171 students who had trained in countries outside the United States. The students sought admission to the D.D.S. degree program, successful completion of which qualified them to sit for U.S. licensure. As with most dental schools, competition is high for admission to the D.D.S. program. The study's goal was to identify what measures contributed to a fair and accurate selection process for dental school applicants from other nations. Multiple regression analyses identified National Board Part II and dexterity measures as significant predictors of academic performance and clinical competency. National Board Part I, TOEFL, and faculty interviews added no significant additional help in predicting eventual academic performance and clinical competency.

Effect of length of dental resident clinical rotations on patient behavior.

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Lau, Agnes

2018-01-01

The purpose of this retrospective chart review study was to determine if the length of residents' comprehensive dental care rotations in a general practice residency affected late cancellations, broken appointments, completion of treatment, timeliness of recall visits, emergency visits, and the need for redo of restorations and prostheses. Patients who presented for comprehensive care from 2010 to 2013, during which residents had 3- to 4-month dental clinic rotations, comprised Group 1, and patients who presented for comprehensive care from 2013 to 2016, during which residents had 11-month dental clinic rotations, comprised Group 2. Subjects were excluded if they only presented for emergency care, they had only one visit, or their care was delivered in both time periods. There were 105 patients in Group 1 and 55 patients in Group 2. The statistically significant results were that Group 1 patients had more late cancellations and broken appointments and failed to reach recall status more often than Group 2 patients, and that Group 1 patients had fewer emergency visits. Within the limitations of this retrospective study, the results suggest that short block rotations have an adverse effect on resident experience and outcomes of patient care in a hospital outpatient setting. © 2018 Special Care Dentistry Association and Wiley Periodicals, Inc.

Quality management and job related factors predicting satisfaction of dental clinic staff in Estonia.

Science.gov (United States)

Merisalu, Eda; Männik, Georg; Põlluste, Kaja

2014-01-01

The aim of the study was to explore the role of managerial style, work environment factors and burnout in determining job satisfaction during the implementation of quality improvement activities in a dental clinic. Quantitative research was carried out using a prestructured anonymous questionnaire to survey 302 respondents in Kaarli Dental Clinic, Estonia. Dental clinic staff assessed job satisfaction, managerial style, work stress and burnout levels through the implementation period of ISO 9000 quality management system in 2003 and annually during 2006-2009. Binary logistic regression was used to explain the impact of satisfaction with management and work organisation, knowledge about managerial activities, work environment and psychosocial stress and burnout on job satisfaction. The response rate limits were between 60% and 89.6%. Job satisfaction increased significantly from 2003 to 2006 and the percentage of very satisfied staff increased from 17 to 38 (pwork organisation and working environment, as well as factors related to career, security and planning. The average scores of emotional exhaustion showed significant decrease, correlating negatively with job satisfaction (pwork environment by decreasing burnout symptoms and increased job satisfaction in staff.

Structural and thermal characterization of polyvinylalcohol grafted SiC nanocrystals

DEFF Research Database (Denmark)

Saini, Isha; Sharma, Annu; Dhiman, Rajnish

2017-01-01

introduced in the characteristic TO and LO mode of vibration of SiC nanocrystals after grafting procedure.XRD analysis confirmed that the grafting procedure did not alter the crystalline geometry of SiC nanocrystals. TEM and SEM images further support the FTIR and Raman spectroscopic results and confirm...... of semiconducting SiC nanocrystals using a novel method. FTIR spectroscopy reveals the introduction of new peaks corresponding to various functional groups of PVA alongwith the presence of characteristic Si-C vibrational peak in the spectra of grafted SiC nanocrystals. Raman spectra depict the presence of changes...... the presence of PVA layer around SiC nanocrystals. Thermal degradation behavior of PVA-g-SiC nanocrystals has been studied using TGA analysis....

SiC Nanoparticles Toughened-SiC/MoSi2-SiC Multilayer Functionally Graded Oxidation Protective Coating for Carbon Materials at High Temperatures

Science.gov (United States)

Abdollahi, Alireza; Ehsani, Naser; Valefi, Zia; Khalifesoltani, Ali

2017-05-01

A SiC nanoparticle toughened-SiC/MoSi2-SiC functionally graded oxidation protective coating on graphite was prepared by reactive melt infiltration (RMI) at 1773 and 1873 K under argon atmosphere. The phase composition and anti-oxidation behavior of the coatings were investigated. The results show that the coating was composed of MoSi2, α-SiC and β-SiC. By the variations of Gibbs free energy (calculated by HSC Chemistry 6.0 software), it could be suggested that the SiC coating formed at low temperatures by solution-reprecipitation mechanism and at high temperatures by gas-phase reactions and solution-reprecipitation mechanisms simultaneously. SiC nanoparticles could improve the oxidation resistance of SiC/MoSi2-SiC multiphase coating. Addition of SiC nanoparticles increases toughness of the coating and prevents spreading of the oxygen diffusion channels in the coating during the oxidation test. The mass loss and oxidation rate of the SiC nanoparticle toughened-SiC/MoSi2-SiC-coated sample after 10-h oxidation at 1773 K were only 1.76% and 0.32 × 10-2 g/cm3/h, respectively.

Survey of the sevoflurane sedation status in one provincial dental clinic center for the disabled

Science.gov (United States)

Park, Chang-hyun

2016-01-01

Background Sevoflurane sedation in pediatric and disabled patients has the advantage of faster induction and recovery compared to general anesthesia, as well as minimum influence on the respiratory and cardiovascular functions, and airway protective reflexes. This study aimed to evaluate the clinical efficacy of sevoflurane sedation used in dental treatment at one provincial dental clinic center for the disabled. Methods We investigated patients' gender, age, reasons for undergoing sedation, medication history prior to treatment, duration of anesthesia, treatment length, type of treatment, and yearly patterns, for 387 cases of dental treatment performed using sevoflurane sedation from January 2013 to October 2016. Results We analyzed 387 cases (215 male patients, 172 female patients). Male patients aged 20 year or older accounted for 39.0% of all patients, marking the highest proportion. Patient's lack of cooperation was the most common reason for performing dental sedation. Prosthetic treatment was the most frequently practiced, accounting for 174 treatment cases. The mean lengths of the entire treatment and of the dental procedure were 55.2 min and 39.8 min, respectively. Conclusions Sevoflurane sedation has the advantage of fast anesthesia induction and recovery compared to general anesthesia; therefore, it can be used efficiently to induce anesthesia in pediatric and disabled patients during short dental procedures, enabling stable treatment of these patients. PMID:28879316

The Effect of an Extramural Program on the Perceived Clinical Competence of Dental Hygiene Students.

Science.gov (United States)

Butters, Janice M.; Vaught, Randall L.

1999-01-01

A study investigated the effect of an extramural rotation on dental-hygiene students' self-perceptions of competence in specific clinical areas. Results indicate student perceptions of competence improved significantly on six of 19 dimensions of dental-hygiene practice over the course of the rotation, suggesting that rotation is a valuable…

SiC Seeded Crystal Growth

Science.gov (United States)

Glass, R. C.; Henshall, D.; Tsvetkov, V. F.; Carter, C. H., Jr.

1997-07-01

The availability of relatively large (30 mm) SiC wafers has been a primary reason for the renewed high level of interest in SiC semiconductor technology. Projections that 75 mm SiC wafers will be available in 2 to 3 years have further peaked this interest. Now both 4H and 6H polytypes are available, however, the micropipe defects that occur to a varying extent in all wafers produced to date are seen by many as preventing the commercialization of many types of SiC devices, especially high current power devices. Most views on micropipe formation are based around Frank's theory of a micropipe being the hollow core of a screw dislocation with a huge Burgers vector (several times the unit cell) and with the diameter of the core having a direct relationship with the magnitude of the Burgers vector. Our results show that there are several mechanisms or combinations of these mechanisms which cause micropipes in SiC boules grown by the seeded sublimation method. Additional considerations such as polytype variations, dislocations and both impurity and diameter control add to the complexity of producing high quality wafers. Recent results at Cree Research, Inc., including wafers with micropipe densities of less than 1 cm - 2 (with 1 cm2 areas void of micropipes), indicate that micropipes will be reduced to a level that makes high current devices viable and that they may be totally eliminated in the next few years. Additionally, efforts towards larger diameter high quality substrates have led to production of 50 mm diameter 4H and 6H wafers for fabrication of LEDs and the demonstration of 75 mm wafers. Low resistivity and semi-insulating electrical properties have also been attained through improved process and impurity control. Although challenges remain, the industry continues to make significant progress towards large volume SiC-based semiconductor fabrication.

Dentoalveolar abscess among children attending a dental clinic in Nigeria.

Science.gov (United States)

Azodo, C C; Chukwumah, N M; Ezeja, E B

2012-09-01

To determine the incidence and causes of dentoalveolar abscess among children attending an outpatient dental clinic in Nigeria. This is a retrospective study of paediatric dental patients treated in University of Benin Teaching Hospital, Benin City from October 2010 to September 2011. The incidence of dentoalveolar abscess was 6.4% (53/824). However only 42 cases had their case notes retrieved for final research analysis. It occurred mostly in the lower right quadrant of the mouth. The affected children were majorly males and first or second child of monogamous family. A total 17 (40.5%) of the affected children were in the 6-11 years age group. This was the first dentist consultation among 35 (83.3%) of the children. The presenting complaint was toothache among two-thirds of the children. History of asthma, tonsillitis, peptic ulcer disease and previous surgery were medical history elicited from 6 (14.3) of the patients. The most implicated tooth was deciduous first molar. The causes of abscess include untreated dental caries 35 (83.3%), trauma 5 (11.9%), failed restoration 1 (2.4%) and periodontal diseases 1 (2.4%). Periapical radioluscency was predominant radiological finding among affected children. Tooth extraction was commonest treatment done. The incidence of dentoalveolar abscess among children was significant. The high frequency of untreated dental caries as the cause of dentoalveolar abscess indicates the need for school and community-based preventive strategies like encouraging infant oral health and preventive dentistry programs and early treatment intervention and dental health education.

Dental Students' Perceived Value of Peer-Mentoring Clinical Leadership Experiences.

Science.gov (United States)

Sheridan, Rachel A; Hammaker, Daniel J; de Peralta, Tracy L; Fitzgerald, Mark

2016-03-01

This pilot study compared second- and fourth-year dental students' perceived values of newly implemented clinical leadership experiences (CLEs) at one U.S. dental school during the 2012-13 academic year. In the CLEs, fourth-year (D4) students mentored second-year (D2) dental students during faculty-supervised patient treatment. The two cohorts' perceived value of the experiences was measured with questionnaires consisting of five-point Likert scale questions and open text responses. Out of a total of 114 D2 and 109 D4 students, 46 D2 students and 35 D4 students participated (response rates of 40.4% and 32.1%, respectively). While responses from both cohorts showed they highly valued the CLEs, the D2s perceived greater value: 4.07 (0.53) v. 3.51 (0.95), pmentor D2s, that the CLEs had educational benefits, and that the CLEs increased their comfort with peer communication. Theme analysis of open text questions revealed that the respondents perceived the D4s were more accessible than faculty and provided guidance and individual attention; the CLEs increased student comfort; the CLEs reinforced D4 skills, knowledge, and confidence; and the CLEs provided management, leadership, and collaborative work experience. Theme analysis also highlighted student concerns about a lack of program structure. Overall, the majority of both groups valued CLEs in their dental education. Particular advantages they perceived were increased comfort, guidance, and attention. Further program development should address student concerns. These results suggest that similar programs should be considered and/or expanded in other dental schools' curricula.

Stability analysis of SiO2/SiC multilayer coatings

International Nuclear Information System (INIS)

Fu Zhiqiang; Jean-Charles, R.

2006-01-01

The stability behaviours of SiC coatings and SiO 2 /SiC coatings in helium with little impurities are studied by HSC Chemistry 4.1, the software for analysis of Chemical reaction and equilibrium in multi-component complex system. It is found that in helium with a low partial pressure of oxidative impurities under different total pressure, the key influence factor controlling T cp of SiC depends is the partial pressure of oxidative impurities; T cp of SiC increases with the partial pressure of oxidative impurities. In helium with a low partial pressure of different impurities, the key influence factor of T cs of SiO 2 are both the partial pressure of impurities and the amount of impurities for l mol SiO 2 ; T cs of SiO 2 increases with the partial pressure of oxidative impurities at the same amount of the impurities for 1 mol SiO 2 while it decreases with the amount of the impurities for 1 mm SiO 2 at the same partial pressure of the impurities. The influence of other impurities on T cp of SiC in He-O 2 is studied and it is found that CO 2 , H 2 O and N-2 increase T cp of SiC in He-O 2 while H 2 , CO and CH 4 decrease T cp of SiC He-O 2 . When there exist both oxidative impurities and reductive impurities, their effect on T cs of SiO 2 can be suppressed by the other. In HTR-10 operation atmosphere, SiO 2 /SiC coatings can keep stable status at higher temperature than SiC coatings, so SiO 2 /SiC coatings is more suitable to improve the oxidation resistance of graphite in HTR-10 operation atmosphere compared with SiC coatings. (authors)

Comparative evaluation of the effectiveness of electronic dental anesthesia with 2% lignocaine in various minor pediatric dental procedures: A clinical study

Directory of Open Access Journals (Sweden)

Abhishek Dhindsa

2011-01-01

Full Text Available One of the most distressing aspects of dentistry for pediatric patients is the fear and anxiety caused by the dental environment, particularly the dental injection. The application and induction of local anesthetics has always been a difficult task, and this demands an alternative method that is convenient and effective. Electronic dental anesthesia, based on the principal of transcutaneous electric nerve stimulation (TENS, promises to be a viable mode of pain control during various pediatric clinical procedures. Therefore, the aim of the present study was to evaluate the effectiveness of TENS and to compare its efficacy with 2% lignocaine during various minor pediatric dental procedures. Pain, comfort and effectiveness of both the anesthetics were evaluated using various scales and no significant difference was observed between 2% lignocaine and TENS in the various pain scales, while TENS was perceived to be significantly effective in comfort and efficacy as judged by the operator and quite comfortable as judged by the patient himself/herself.

Patients' Willingness to Participate in Rapid HIV Testing: A pilot study in three New York City dental hygiene clinics.

Science.gov (United States)

Davide, Susan H; Santella, Anthony J; Furnari, Winnie; Leuwaisee, Petal; Cortell, Marilyn; Krishnamachari, Bhuma

2017-12-01

Purpose: One in eight people living with an HIV infection in the United States is unaware of their status. Rapid HIV testing (RHT) is an easily used and accepted screening tool that has been introduced in a limited number of clinical settings. The purpose of this study was to investigate patient acceptability, certainty of their decision, and willingness to pay for screening if RHT was offered in university-based dental hygiene clinics. Methods: A cross-sectional survey was administered to 426 patients at three dental hygiene clinics in New York City over a period of four months. The survey questionnaire was based on the decisional conflict scale measuring personal perceptions; with zero indicating extremely high conflict to four indicating no conflict. Patients were assessed for their acceptance of RHT, provider preference for administration of the test and their willingness to pay for RHT. Results: Over half (72.2%) indicated acceptance of HIV testing in a dental hygiene clinic setting; with 85.3% choosing oral RHT, 4.9% fingerstick RHT, and 8.8% venipuncture. Respondents were amenable to testing when offered by dental hygienists (71.7%) and dentists (72.4%). Over 30% indicated their willingness to receive HIV testing in the dental setting when offered at no additional cost. The mean decisional conflict score was 3.42/4.0 indicating no decisional conflict. Conclusions: Patients are willing to undergo oral RHT when offered as a service and provided by dental hygienists in the dental setting. Patients appear to be aware of the benefits and risks associated with RHT. Further research is needed to evaluate the public health benefits and logistical challenges facing the delivery of RHT within in the dental setting. Copyright © 2017 The American Dental Hygienists’ Association.

Computational Modeling of Radiation Phenomenon in SiC for Nuclear Applications

Science.gov (United States)

Ko, Hyunseok

Silicon carbide (SiC) material has been investigated for promising nuclear materials owing to its superior thermo-mechanical properties, and low neutron cross-section. While the interest in SiC has been increasing, the lack of fundamental understanding in many radiation phenomena is an important issue. More specifically, these phenomena in SiC include the fission gas transport, radiation induced defects and its evolution, radiation effects on the mechanical stability, matrix brittleness of SiC composites, and low thermal conductivities of SiC composites. To better design SiC and SiC composite materials for various nuclear applications, understanding each phenomenon and its significance under specific reactor conditions is important. In this thesis, we used various modeling approaches to understand the fundamental radiation phenomena in SiC for nuclear applications in three aspects: (a) fission product diffusion through SiC, (b) optimization of thermodynamic stable self-interstitial atom clusters, (c) interface effect in SiC composite and their change upon radiation. In (a) fission product transport work, we proposed that Ag/Cs diffusion in high energy grain boundaries may be the upper boundary in unirradiated SiC at relevant temperature, and radiation enhanced diffusion is responsible for fast diffusion measured in post-irradiated fuel particles. For (b) the self-interstitial cluster work, thermodynamically stable clusters are identified as a function of cluster size, shape, and compositions using a genetic algorithm. We found that there are compositional and configurational transitions for stable clusters as the cluster size increases. For (c) the interface effect in SiC composite, we investigated recently proposed interface, which is CNT reinforced SiC composite. The analytical model suggests that CNT/SiC composites have attractive mechanical and thermal properties, and these fortify the argument that SiC composites are good candidate materials for the cladding

Zirconia Dental Implants: Investigation of Clinical Parameters, Patient Satisfaction, and Microbial Contamination.

Science.gov (United States)

Holländer, Jens; Lorenz, Jonas; Stübinger, Stefan; Hölscher, Werner; Heidemann, Detlef; Ghanaati, Shahram; Sader, Robert

2016-01-01

In recent years, dental implants made from zirconia have been further developed and are considered a reliable treatment method for replacing missing teeth. The aim of this study was to analyze dental implants made from zirconia regarding their clinical performance compared with natural teeth (control). One hundred six zirconia implants in 38 adults were analyzed in a clinical study after 1 year of loading. The plaque index (PI), bleeding on probing (BOP), probing pocket depth (PPD), probing attachment level (PAL), and creeping or recession (CR/REC) of the gingiva were detected and compared with natural control teeth (CT). Furthermore, the papilla index (PAP), Periotest values (PTV), microbial colonization of the implant/dental sulcus fluid, and patient satisfaction were assessed. The survival rate was 100%. No statistical significance was observed between implants and teeth regarding BOP, PPD, and PAL. A statistical significance was detected regarding PI and CR/REC with significantly less plaque accumulation and recession in the study group. Mean PAP was 1.76 ± 0.55, whereas the mean PTV was -1.31 ± 2.24 (range from -5 to +6). A non-statistically significant higher colonization of periodontitis/peri-implantitis bacteria was observed in the implant group. The questionnaire showed that the majority of the patients were satisfied with the overall treatment. One-piece zirconia dental implants exhibited similar clinical results (BOP, PPD, and PAL) compared with natural teeth in regard to adhesion of plaque (PI) and creeping attachment (CR/REC); zirconia implants performed even better. The favorable results for PAL and CR/REC reflect the comparable low affinity of zirconia for plaque adhesion. Patient satisfaction indicated a high level of acceptance for zirconia implants. However, a long-term follow-up is needed to support these findings.

High density plasma via hole etching in SiC

International Nuclear Information System (INIS)

Cho, H.; Lee, K.P.; Leerungnawarat, P.; Chu, S.N.G.; Ren, F.; Pearton, S.J.; Zetterling, C.-M.

2001-01-01

Throughwafer vias up to 100 μm deep were formed in 4H-SiC substrates by inductively coupled plasma etching with SF 6 /O 2 at a controlled rate of ∼0.6 μm min-1 and use of Al masks. Selectivities of >50 for SiC over Al were achieved. Electrical (capacitance-voltage: current-voltage) and chemical (Auger electron spectroscopy) analysis techniques showed that the etching produced only minor changes in reverse breakdown voltage, Schottky barrier height, and near surface stoichiometry of the SiC and had high selectivity over common frontside metallization. The SiC etch rate was a strong function of the incident ion energy during plasma exposure. This process is attractive for power SiC transistors intended for high current, high temperature applications and also for SiC micromachining

Change in stated clinical practice associated with participation in the Dental Practice-Based Research Network

DEFF Research Database (Denmark)

Gilbert, Gregg H; Richman, Joshua S; Qvist, Vibeke

2010-01-01

Clinical researchers have attempted many methods to translate scientific evidence into routine clinical practice, with varying success. Practice-based research networks (PBRNs) provide an important, practitioner-friendly venue to test these methods. Dentist practitioner-investigators from...... the Dental Practice-Based Research Network (DPBRN) completed a detailed questionnaire about how they diagnose and treat dental caries. Next, they received a customized report that compared their answers to those from all other practitioner-investigators. Then, 126 of them attended the DPBRN's first network......-wide meeting of practitioner-investigators from all five of its regions. During that meeting, certain questions were repeated and new ones were asked about the dentist's intention to change the way that he or she diagnosed or treated dental caries. Less than one-third of practitioner-investigators intended...

A direct bonded fixed partial dental prosthesis: A clinical report

OpenAIRE

Tanoue, Naomi; Tanaka, Takuo

2015-01-01

A direct bonded fixed partial dental prosthesis, with a composite resin denture tooth as a pontic, a tri-n-butylborane initiated adhesive resin, and screw posts for reinforcement, was still functioning after an observation period of 20 years. The prosthesis was found to be reliable for long-term clinical use when chemically and mechanically reinforced.

Clinical Diagnosis of Dental Caries in the 21st Century: Introductory Paper - ORCA Saturday Afternoon Symposium, 2016.

Science.gov (United States)

Machiulskiene, Vita; Carvalho, Joana Christina

2018-03-05

Classifications employed to measure dental caries should first of all reflect the dynamics of the disease, in order to provide a solid basis for subsequent treatment decisions and for further monitoring of dental health of individual patients and populations. The contemporary philosophy of dental caries management implies that nonoperative treatment of caries lesions should be implemented whenever possible, limiting operative interventions to the severe and irreversible cases. The ORCA Saturday Afternoon Symposium 2016, held back-to-back to the 63rd ORCA Congress in Athens, Greece, was intended to provide an update on general requirements for clinical caries diagnosis and to overview caries diagnostic classifications including their rationale, validation, advantages, and limitations. Clinical caries diagnostic criteria and caries management outcomes are interrelated, and any diagnostic classification disregarding this concept is outdated, according to the current understanding of oral health care. Choosing clinical caries diagnostic classifications that assess the activity status of detected lesions should be a priority for dental professionals since these classifications favor the best clinical practice directed towards nonoperative interventions. The choice of clinical caries diagnostic classifications in research, in clinical practice, and in public health services should be guided by the best available scientific evidence. The clinical caries diagnostic classifications should be universally applicable in all these fields. Policy making in oral health care and the underlying policy analyses should follow the same standards. Any clinical caries diagnostic classification disregarding the universality of its use is of limited or no interest in the context of the clinical caries diagnosis of today. © 2018 S. Karger AG, Basel.

Impact of Atraumatic Restorative Treatment (ART) on the treatment profile in pilot government dental clinics in Tanzania.

Science.gov (United States)

Kikwilu, Emil Namakuka; Frencken, Jo; Mulder, Jan

2009-06-08

The predominant mode of treatment in government dental clinics in Tanzania has been tooth extraction because the economy could not support the conventional restorative care which depends on expensive equipment, electricity and piped water systems. Atraumatic Restorative Treatment (ART) was perceived as a suitable alternative. A 3.5-year study was designed to document the changes in the treatment profiles ascribed to the systematic introduction of ART in pilot government dental clinics. Dental practitioners who were working in 13 government dental clinics underwent a 7-day ART training. Treatment record data on teeth extracted and teeth restored by the conventional and ART approaches were collected from these clinics for the three study periods. The mean percentage of ART restorations to total treatment, ART restorations to total restorations, and total restorations to total treatments rendered were computed. Differences between variables were determined by ANOVA, t-test and Chi-square. The mean percentage of ART restorations to total treatment rendered was 0.4 (SE = 0.5) and 11.9 (SE = 1.1) during the baseline and second follow-up period respectively (ANOVA mixed model; P ART restorations to total restorations rendered at baseline and 2nd follow-up period was 8.4% and 88.9% respectively (ANOVA mixed model; P ART restorations, 96.6% willing to receive ART restoration again in future, and 94.9% willing to recommend ART treatment to their close relatives. ART introduction in pilot government dental clinics raised the number of teeth saved by restorative care. Countrywide introduction of the ART approach in Tanzania is recommended.

Eliciting students′ perceptions of integrated clinical dental education in Saudi Arabia: A cross-sectional study

Directory of Open Access Journals (Sweden)

Mahmoud Al-Dajani

2016-01-01

Conclusion: In the integrated curriculum, our study highlights the importance of clinical training not only in making dental students competent but also in increasing their confidence in performing clinical procedures.

Comparative study of SiC- and Si-based photovoltaic inverters

Science.gov (United States)

Ando, Yuji; Oku, Takeo; Yasuda, Masashi; Shirahata, Yasuhiro; Ushijima, Kazufumi; Murozono, Mikio

2017-01-01

This article reports comparative study of 150-300 W class photovoltaic inverters (Si inverter, SiC inverter 1, and SiC inverter 2). In these sub-kW class inverters, the ON-resistance was considered to have little influence on the efficiency. The developed SiC inverters, however, have exhibited an approximately 3% higher direct current (DC)-alternating current (AC) conversion efficiency as compared to the Si inverter. Power loss analysis indicated a reduction in the switching and reverse recovery losses of SiC metal-oxide-semiconductor field-effect transistors used for the DC-AC converter is responsible for this improvement. In the SiC inverter 2, an increase of the switching frequency up to 100 kHz achieved a state-of-the-art combination of the weight (1.25 kg) and the volume (1260 cm3) as a 150-250 W class inverter. Even though the increased switching frequency should cause the increase of the switching losses, the SiC inverter 2 exhibited an efficiency comparable to the SiC inverter 1 with a switching frequency of 20 kHz. The power loss analysis also indicated a decreased loss of the DC-DC converter built with SiC Schottky barrier diodes led to the high efficiency for its increased switching frequency. These results clearly indicated feasibility of SiC devices even for sub-kW photovoltaic inverters, which will be available for the applications where compactness and efficiency are of tremendous importance.

The relationship between the quality of education and the poor dental practice: Clinical case report

Directory of Open Access Journals (Sweden)

Cléa Adas Saliba Garbin

2013-01-01

Full Text Available The activities developed in health area are of great importance, because they have the aim to preserve the life of the men, and therefore, must be performed by authorized persons. The increase of the number of dental schools, the decline at the education quality and a higher admission of students with low ability to exercise their profession, are facts that bring disastrous consequences for society. These facts are, also, reflected at the moral, ethical and technical-scientific performance of the professional. The purpose of this clinic case is to show that although there is a significant suplly of education institutions, there is a lack of scientific and adequate technical knowledgement from the graduated dentals surgeons. The patient MSL, 17 year old, female, went to a dental clinic presenting a tray type Vernis, attached to the lower arch. After clinical evaluation, it was showed that an incorrect material was used for the impression technique, being impossible to take out the tray by the conventional mann r. The planning for the removal of the tray was through the divide of it. Thus, the consequence of the lack of knowledge in the use of impression materials had caused a great incovinience to the patient. It can be concluded that the rate of malpractice is directly related to the professional preparation, highlighting the importance of quality dental education for a responsible clinical practice.

Important considerations for designing and reporting epidemiologic and clinical studies in dental traumatology.

Science.gov (United States)

Andersson, Lars; Andreasen, Jens O

2011-08-01

The purpose of this article is to suggest important considerations for epidemiologic and clinical studies in the field of dental traumatology. The article is based on the authors' experiences from research in this field and editorial board work for the scientific journal Dental Traumatology. Examples are given of issues where development is important. The importance of planning ahead of the study and consulting with experts in other fields is emphasized. © 2011 John Wiley & Sons A/S.

Use of dental clinics and oral hygiene practices in the Kingdom of Saudi Arabia, 2013.

Science.gov (United States)

El Bcheraoui, Charbel; Tuffaha, Marwa; Daoud, Farah; Kravitz, Hannah; AlMazroa, Mohammad A; Al Saeedi, Mohammad; Memish, Ziad A; Basulaiman, Mohammed; Al Rabeeah, Abdullah A; Mokdad, Ali H

2016-04-01

We conducted a large household survey in 2013 to determine the current status of oral health practices and use of oral health services in the Kingdom of Saudi Arabia (KSA). The Saudi Health Information Survey is a national multistage survey of individuals ≥ 15 years of age. We used a backward elimination multivariate logistic regression model to measure the association between having been to a dental clinic during the last year, and sex, age, marital status, education, time since last routine medical examination, history of diagnosis with a cardiovascular chronic condition, brushing or flossing teeth and use of Miswak (a chewing stick). Between April and June 2013, 10,735 participants completed the survey (89.4% of the households contacted). An estimated 1.5 million (11.5%) and 6.3 million (48.6%) Saudi Arabian people, ≥ 15 years of age, had visited a dental clinic for a routine check-up and for a complaint during the last year, respectively. In total, 16.3%, 85.0% and 52% of Saudi Arabian people never brush their teeth, never floss their teeth or never use Miswak, respectively. The probability of visiting a dental clinic increased with education, among individuals who brushed or flossed their teeth and who used Miswak. Oral hygiene practices are not common among Saudi Arabian people, and use of health care for prevention of oral disease is limited. Hence, the need for oral health promotion is pressing. The KSA Ministry of Health should develop and implement programmes, through its primary health clinics, to increase the awareness of the importance of good oral health. © 2016 The Authors. International Dental Journal published by John Wiley & Sons Ltd on behalf of World Dental Federation.

Effectiveness of Standardized Patient Simulations in Teaching Clinical Communication Skills to Dental Students.

Science.gov (United States)

McKenzie, Carly T; Tilashalski, Ken R; Peterson, Dawn Taylor; White, Marjorie Lee

2017-10-01

The aim of this study was to investigate dental students' long-term retention of clinical communication skills learned in a second-year standardized patient simulation at one U.S. dental school. Retention was measured by students' performance with an actual patient during their fourth year. The high-fidelity simulation exercise focused on clinical communication skills took place during the spring term of the students' second year. The effect of the simulation was measured by comparing the fourth-year clinical performance of two groups: those who had participated in the simulation (intervention group; Class of 2016) and those who had not (no intervention/control group; Class of 2015). In the no intervention group, all 47 students participated; in the intervention group, 58 of 59 students participated. Both instructor assessments and students' self-assessments were used to evaluate the effectiveness of key patient interaction principles as well as comprehensive presentation of multiple treatment options. The results showed that students in the intervention group more frequently included cost during their treatment option presentation than did students in the no intervention group. The instructor ratings showed that the intervention group included all key treatment option components except duration more frequently than did the no intervention group. However, the simulation experience did not result in significantly more effective student-patient clinical communication on any of the items measured. This study presents limited evidence of the effectiveness of a standardized patient simulation to improve dental students' long-term clinical communication skills with respect to thorough presentation of treatment options to a patient.

New constructions of approximately SIC-POVMs via difference sets

Science.gov (United States)

Luo, Gaojun; Cao, Xiwang

2018-04-01

In quantum information theory, symmetric informationally complete positive operator-valued measures (SIC-POVMs) are related to quantum state tomography (Caves et al., 2004), quantum cryptography (Fuchs and Sasaki, 2003) [1], and foundational studies (Fuchs, 2002) [2]. However, constructing SIC-POVMs is notoriously hard. Although some SIC-POVMs have been constructed numerically, there does not exist an infinite class of them. In this paper, we propose two constructions of approximately SIC-POVMs, where a small deviation from uniformity of the inner products is allowed. We employ difference sets to present the first construction and the dimension of the approximately SIC-POVMs is q + 1, where q is a prime power. Notably, the dimension of this framework is new. The second construction is based on partial geometric difference sets and works whenever the dimension of the framework is a prime power.

Development of the fabrication process of SiC composite by polycarbosilane

International Nuclear Information System (INIS)

Park, Ji Yeon; Kim, Weon Ju; Kim, Jung Il; Ryu, Woo Seog

2004-11-01

This technical report reviewed the fabrication process of fiber reinforced ceramic composites, characteristics of the PIP process, and applications of SiC f /SiC composite to develop a silicon carbide composite by PIP method. Additionally, characteristics and thermal behaviors of a PCS+SiC powder slurry and infiltration behaviors of slurry into the SiC fabric was evaluated. The stacking behaviors of SiC fabrics infiltrated a PCS+SiC powder slurry was also investigated. Using this stacked preforms, SiC f /SiC composites were fabricated by the electron beam curing and pyrolysis process and the thermal oxidation curing and pyrolysis process, respectively. And the characteristics of both composites were compared

Near-surface and bulk behavior of Ag in SiC

International Nuclear Information System (INIS)

Xiao, H.Y.; Zhang, Y.; Snead, L.L.; Shutthanandan, V.; Xue, H.Z.; Weber, W.J.

2012-01-01

Highlights: ► Ag release from SiC poses problems in safe operation of nuclear reactors. ► Near-surface and bulk behavior of Ag are studied by ab initio and ion beam methods. ► Ag prefers to adsorb on the surface rather than in the bulk SiC. ► At high temperature Ag desorbs from the surface instead of diffusion into bulk SiC. ► Surface diffusion may be a dominating mechanism accounting for Ag release from SiC. - Abstract: The diffusive release of fission products, such as Ag, from TRISO particles at high temperatures has raised concerns regarding safe and economic operation of advanced nuclear reactors. Understanding the mechanisms of Ag diffusion is thus of crucial importance for effective retention of fission products. Two mechanisms, i.e., grain boundary diffusion and vapor or surface diffusion through macroscopic structures such as nano-pores or nano-cracks, remain in debate. In the present work, an integrated computational and experimental study of the near-surface and bulk behavior of Ag in silicon carbide (SiC) has been carried out. The ab initio calculations show that Ag prefers to adsorb on the SiC surface rather than in the bulk, and the mobility of Ag on the surface is high. The energy barrier for Ag desorption from the surface is calculated to be 0.85–1.68 eV, and Ag migration into bulk SiC through equilibrium diffusion process is not favorable. Experimentally, Ag ions are implanted into SiC to produce Ag profiles buried in the bulk and peaked at the surface. High-temperature annealing leads to Ag release from the surface region instead of diffusion into the interior of SiC. It is suggested that surface diffusion through mechanical structural imperfection, such as vapor transport through cracks in SiC coatings, may be a dominating mechanism accounting for Ag release from the SiC in the nuclear reactor.

Conversion of wood flour/SiO2/phenolic composite to porous SiC ceramic containing SiC whiskers

Directory of Open Access Journals (Sweden)

Li Zhong

2013-01-01

Full Text Available A novel wood flour/SiO2/phenolic composite was chosen to be converted into porous SiC ceramic containing SiC whiskers via carbothermal reduction. At 1550°C the composite is converted into porous SiC ceramic with pore diameters of 10~40μm, and consisting of β-SiC located at the position of former wood cell walls. β-SiC wire-like whiskers of less than 50 nm in diameter and several tens to over 100 μm in length form within the pores. The surface of the resulting ceramic is coated with β-SiC necklace-like whiskers with diameters of 1~2μm.

Microwave joining of SiC ceramics and composites

Energy Technology Data Exchange (ETDEWEB)

Ahmad, I.; Silberglitt, R.; Tian, Y.L. [FM Technologies, Inc., Fairfax, VA (United States); Katz, J.D. [Los Alamos National Lab., NM (United States)

1997-04-01

Potential applications of SiC include components for advanced turbine engines, tube assemblies for radiant burners and petrochemical processing and heat exchangers for high efficiency electric power generation systems. Reliable methods for joining SiC are required in order to cost-effectively fabricate components for these applications from commercially available shapes and sizes. This manuscript reports the results of microwave joining experiments performed using two different types of SiC materials. The first were on reaction bonded SiC, and produced joints with fracture toughness equal to or greater than that of the base material over an extended range of joining temperatures. The second were on continuous fiber-reinforced SiC/SiC composite materials, which were successfully joined with a commercial active brazing alloy, as well as by using a polymer precursor.

Delimitation of work areas and classification of workers in the current practice of dental 'endo-buccal' radiography in dental clinic: some personal reflections

International Nuclear Information System (INIS)

Ariscon, J.M.

2008-01-01

Addressing exclusively the use of retro-alveolar-type dental radiology apparatus in dental clinics, the author presents the instrumentation used to measure ambient exposure levels, presents the zoning approach based on the NF C 15-163 standard (definition of a monitored area, a controlled area, and a specifically regulated area), and that based on an analogical mode. He comments the assessment of the practitioner global external exposure, discusses the interpretation issues, and proposes some recommendations

Evaluating complications of local anesthesia administration and reversal with phentolamine mesylate in a portable pediatric dental clinic.

Science.gov (United States)

Boynes, Sean G; Riley, Amah E; Milbee, Sarah; Bastin, Meghan R; Price, Maylyn E; Ladson, Andrea

2013-08-01

This study sought to identify and quantify complications with local anesthetic administration and reversal on consecutive patients seen for comprehensive dental care in a school-based, portable dental clinic, and includes data on the patients seen by the participating portable dental providers. In 923 dental visits where local anesthetic was administered, a standardized form was used to gain further information and identify any complications; this was accompanied by a questionnaire for the student's teacher, in order to quantify the student's distraction and disruption ratings following the dental visit. After statistical analysis of the 923 consecutive cases, the overall complication rate was 5.3%. All of the complications were considered to be mild or moderate, and there were no severe event reports. The complications encountered most frequently (n = 49) were associated with self-inflicted soft tissue injury. The results of this study indicate that comprehensive care with local anesthesia delivered by a school-based portable dental clinic has a low risk of complications. Whereas safe administration of dental care is achievable with or without phentolamine mesylate as a local anesthetic reversal agent, its use was determined to improve safety outcomes. Three factors appeared to directly increase the incidence of complications: the administration of an inferior alveolar nerve block, attention deficit disorder, and obesity. Teacher evaluations demonstrated that children receiving care by a portable dental team were able to reorient back to classwork and were not disruptive to classmates.

Clinical usefulness of teleradiology in general dental practice

Energy Technology Data Exchange (ETDEWEB)

Choi, Jin Woo [Dept. of Oral and Maxillofacial Radiology, Dankook University College of Dentistry, Cheonan (Korea, Republic of)

2013-06-15

This study was performed to investigate the clinical usefulness of teleradiology in general dental practice. Two hundred and seventy five cases were submitted for inquiry to the case presentation board of the website of The Korean Academy of Oral and Maxillofacial Radiology for a 5 year periods. The diagnosis results of those cases were analyzed according to the disease classification, the correlation with the patient's chief complaint, the necessity of additional examinations or treatments, the image modalities, and the number of dentists inquiring. Differential diagnoses of normal anatomic structures were the most frequently submitted cases, covering 15.6% of all cases. Among 275 cases, 164 cases required no additional treatments or examinations. Panoramic radiographs were the most frequently submitted images, accounting for 248 inquiries. The 275 cases were submitted by 96 dentists. Fifty-two dentists wrote one inquiry, and 44 inquired 2 or more times. The average inquiry number of the latter group was 5.0 cases. A teleradiology system in general dental practice could be helpful in the differential diagnosis of common lesions and reduce unnecessary costs.

Access to and use of computers among clinical dental students of ...

African Journals Online (AJOL)

Access to and use of computers among clinical dental students of the University of Lagos. PO Ayanbadejo, OO Sofola, OG Uti. Abstract. No Abstract. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. Article Metrics. No metrics found. Metrics powered by PLOS ALM

Introduction of nano-laminate Ti3SiC2 and SiC phases into Cf-C composite by liquid silicon infiltration method

Directory of Open Access Journals (Sweden)

Omid Yaghobizadeh

2017-03-01

Full Text Available The material Cf-C-SiC-Ti3SiC2 is promising for high temperature application. Due to the laminated structure and special properties, the Ti3SiC2 is one of the best reinforcements for Cf-C-SiC composites. In this paper, Cf-C-SiC-Ti3SiC2 composites were fabricated by liquid silicon infiltration (LSI method; the effect of the TiC amount on the various composites properties were studied. For samples with 0, 50 and 90 vol.% of TiC, the results show that bending strength are 168, 190, and 181 MPa; porosities are 3.2, 4.7, and 9%; the fracture toughness are 6.1, 8.9, and 7.8 MPa∙m1/2; interlaminar shear strength are 27, 36, and 30 MPa; the amount of the MAX phase are 0, 8.5, and 5.6 vol.%, respectively. These results show that amount of TiC is not the main effective parameter in synthesis of Ti3SiC2. The existence of carbon promotes the synthesis of Ti3SiC2 indicating that only sufficient carbon content can lead to the appearance of Ti3SiC2 in the LSI process.

Clinical significance of dental root canal microflora.

Science.gov (United States)

Gomes, B P; Lilley, J D; Drucker, D B

1996-01-01

Previous work by this group has shown that a significant association exists between pain and the presence of either Prevotella or Peptostreptococcus spp. in dental root canals. The aim of this study was to examine a more extensive series of canals microbiologically, to determine whether any other particular endodontic symptoms or clinical signs showed specific associations with individual bacterial species. Seventy root canals were examined microbiologically and clinical data collected to investigate in detail such associations. Of the canals studied, 37 were associated with pain, 49 with tenderness to percussion, 23 with swelling, six with purulent exudate and 57 presented with wet root canals. Anaerobes were isolated from 70.3% of painful canals and from 29.7% of pain-free canals. Significant associations were found between (a) pain and either Prevotella spp. or peptostreptococci, both with P spp. (P Eubacterium spp. (P spp. or Pstr. micros, both with P spp. (each P Eubacterium, Peptostreptococcus, Prevotella or Propionibacterium (each P < 0.05). It was concluded that several different endodontic clinical signs and symptoms are significantly associated with specific bacterial species.

Homoepitaxial VPE growth of SiC active layers

Energy Technology Data Exchange (ETDEWEB)

Burk, A.A. Jr. [Northrop Grumman Electron. Sensors and Syst. Div., Baltimore, MD (United States); Rowland, L.B. [Northrop Grumman Sci. and Technol. Center, Pittsburgh, PA (United States)

1997-07-01

SiC active layers of tailored thickness and doping form the heart of all SiC electronic devices. These layers are most conveniently formed by vapor phase epitaxy (VPE). Exacting requirements are placed upon the SiC-VPE layers` material properties by both semiconductor device physics and available methods of device processing. In this paper, the current ability of the SiC-VPE process to meet these requirements is described along with continuing improvements in SiC epitaxial reactors, processes and materials. (orig.) 48 refs.

Portable digital assistants (PDAs) in dentistry: part II--pilot study of PDA use in the dental clinic.

Science.gov (United States)

Reynolds, P A; Harper, J; Dunne, S; Cox, M; Myint, Y K

2007-04-28

To describe a simple technical evaluation of the access, security issues and uses of wireless networked PDAs in a dental clinic and report a pilot study investigating students' educational use of PDAs to access a Virtual Learning Environment (VLE) in a dental clinic. To undertake a technical evaluation of wireless networking to PDAs focusing on security issues, robustness of the system and accessibility particularly to educational resources. To evaluate the impact of using a PDA on undergraduate students in the dental clinic and at home. Part II describes the technical and educational evaluation of PDAs used by one group of 12 undergraduate fourth year students in the Primary Dental Care clinic. A cross over trial of six students with PDAs and six without was carried out during one semester of 12 weeks. Technical issues such as secure internet access using wireless connectivity were addressed. An assessment of the general and educational use and the students' attitudes towards using PDAs was undertaken using online questionnaires and focus group discussions. Over 90% of participants wanted PDAs as part of their dental kit. The potential of PDA use in dental training was demonstrated by a good to excellent response by over 75% of participants to having access to online support materials, particularly videos, being able to make notes for individual study and to keep a diary of their commitments to teaching sessions. Recreational use included a 100% good to excellent response to playing games and keeping a diary. The PDA proved to be a convenient and versatile mode of access to online education. Technical solutions enabled a substantial proportion of the functionality of WebCT (Web Course Tools) to be accessed by the students in a clinical environment. Both novice and experienced users were able to appreciate the use of the PDA and the less able considered that their ICT skills had improved. However, further research is needed to determine how students use a range of

Calculus detection calibration among dental hygiene faculty members utilizing dental endoscopy: a pilot study.

Science.gov (United States)

Partido, Brian B; Jones, Archie A; English, Dana L; Nguyen, Carol A; Jacks, Mary E

2015-02-01

Dental and dental hygiene faculty members often do not provide consistent instruction in the clinical environment, especially in tasks requiring clinical judgment. From previous efforts to calibrate faculty members in calculus detection using typodonts, researchers have suggested using human subjects and emerging technology to improve consistency in clinical instruction. The purpose of this pilot study was to determine if a dental endoscopy-assisted training program would improve intra- and interrater reliability of dental hygiene faculty members in calculus detection. Training included an ODU 11/12 explorer, typodonts, and dental endoscopy. A convenience sample of six participants was recruited from the dental hygiene faculty at a California community college, and a two-group randomized experimental design was utilized. Intra- and interrater reliability was measured before and after calibration training. Pretest and posttest Kappa averages of all participants were compared using repeated measures (split-plot) ANOVA to determine the effectiveness of the calibration training on intra- and interrater reliability. The results showed that both kinds of reliability significantly improved for all participants and the training group improved significantly in interrater reliability from pretest to posttest. Calibration training was beneficial to these dental hygiene faculty members, especially those beginning with less than full agreement. This study suggests that calculus detection calibration training utilizing dental endoscopy can effectively improve interrater reliability of dental and dental hygiene clinical educators. Future studies should include human subjects, involve more participants at multiple locations, and determine whether improved rater reliability can be sustained over time.

Dental, Dental Hygiene, and Graduate Students' and Faculty Perspectives on Dental Hygienists' Professional Role and the Potential Contribution of a Peer Teaching Program.

Science.gov (United States)

McComas, Martha J; Inglehart, Marita R

2016-09-01

The changing role of dental hygienists deserves dental and dental hygiene educators' attention. The first aim of this survey study was to assess University of Michigan dental, dental hygiene, and graduate students' and faculty members' perceptions of dental hygienists' roles; their attitudes and behaviors related to clinical interactions between dental and dental hygiene students; and perceived benefits of engaging dental hygiene students as peer teachers for dental students. The second aim was to assess whether one group of dental students' experiences with dental hygiene student peer teaching affected their perceptions of the dental hygiene profession. Survey respondents were 57 dental hygiene students in all three years of the program (response rate 60% to 100%); 476 dental students in all four years (response rate 56% to 100%); 28 dental and dental hygiene graduate students (response rate 28%); and 67 dental and dental hygiene faculty members (response rate 56%). Compared to the other groups, dental students reported the lowest average number of services dental hygienists can provide (p≤0.001) and the lowest average number of patient groups for which dental hygienists can provide periodontal care (ppeer teaching (ppeer teaching. After experiencing dental hygiene student peer teaching, the dental students' perceptions of dental hygienists' roles, attitudes about clinical interactions with dental hygienists, and perceived benefits of dental hygiene student peer teachers improved and were more positive than the responses of their peers with no peer teaching experiences. These results suggest that dental hygiene student peer teaching may improve dental students' perceptions of dental hygienists' roles and attitudes about intraprofessional care.

Rare earth element abundances in presolar SiC

Science.gov (United States)

Ireland, T. R.; Ávila, J. N.; Lugaro, M.; Cristallo, S.; Holden, P.; Lanc, P.; Nittler, L.; Alexander, C. M. O'D.; Gyngard, F.; Amari, S.

2018-01-01

Individual isotope abundances of Ba, lanthanides of the rare earth element (REE) group, and Hf have been determined in bulk samples of fine-grained silicon carbide (SiC) from the Murchison CM2 chondrite. The analytical protocol involved secondary ion mass spectrometry with combined high mass resolution and energy filtering to exclude REE oxide isobars and Si-C-O clusters from the peaks of interest. Relative sensitivity factors were determined through analysis of NIST SRM reference glasses (610 and 612) as well as a trace-element enriched SiC ceramic. When normalised to chondrite abundances, the presolar SiC REE pattern shows significant deficits at Eu and Yb, which are the most volatile of the REE. The pattern is very similar to that observed for Group III refractory inclusions. The SiC abundances were also normalised to s-process model predictions for the envelope compositions of low-mass (1.5-3 M⊙) AGB stars with close-to-solar metallicities (Z = 0.014 and 0.02). The overall trace element abundances (excluding Eu and Yb) appear consistent with the predicted s-process patterns. The depletions of Eu and Yb suggest that these elements remained in the gas phase during the condensation of SiC. The lack of depletion in some other moderately refractory elements (like Ba), and the presence of volatile elements (e.g. Xe) indicates that these elements were incorporated into SiC by other mechanisms, most likely ion implantation.

Oral Health Status and Behaviour of Mauritians Visiting Private Dental Clinics

Science.gov (United States)

Gunsam, P. Pugo; Banka, S.

2011-01-01

Purpose: This paper seeks to assess the oral health status and behaviour of a sample of the Mauritian population visiting private dental clinics. Design/methodology/approach: Oral health status was determined using the World Health Organization (Decayed, Missing, Filled Teeth (DMFT) index indicating the prevalence of caries, and factors associated…

Access to dental care-parents' and caregivers' views on dental treatment services for people with disabilities.

LENUS (Irish Health Repository)

Prabhu, Neeta T

2010-03-01

The goal of this study was to elicit the views of patients or parents\\/caregivers of patients with disabilities regarding access to dental care. A questionnaire was generated both from interviews with patients\\/parents\\/caregivers already treated under sedation or general anesthesia as well as by use of the Delphi technique with other stakeholders. One hundred thirteen patients from across six community dental clinics and one dental hospital were included. Approximately, 38% of the subjects used a general dental practitioner and 35% used the community dental service for their dental care, with only 27% using the hospital dental services. Overall waiting time for an appointment at the secondary care setting was longer than for the primary care clinics. There was a high rate of parent\\/caregiver satisfaction with dental services and only five patients reported any difficulty with travel and access to clinics. This study highlights the need for a greater investment in education and training to improve skills in the primary dental care sector.

SiC Conversion Coating Prepared from Silica-Graphite Reaction

Directory of Open Access Journals (Sweden)

Back-Sub Sung

2017-01-01

Full Text Available The β-SiC conversion coatings were successfully synthesized by the SiO(v-graphite(s reaction between silica powder and graphite specimen. This paper is to describe the effects on the characteristics of the SiC conversion coatings, fabricated according to two different reaction conditions. FE-SEM, FE-TEM microstructural morphologies, XRD patterns, pore size distribution, and oxidation behavior of the SiC-coated graphite were investigated. In the XRD pattern and SAD pattern, the coating layers showed cubic SiC peak as well as hexagonal SiC peak. The SiC coatings showed somewhat different characteristics with the reaction conditions according to the position arrangement of the graphite samples. The SiC coating on graphite, prepared in reaction zone (2, shows higher intensity of beta-SiC main peak (111 in XRD pattern as well as rather lower porosity and smaller main pore size peak under 1 μm.

About SIC POVMs and discrete Wigner distributions

International Nuclear Information System (INIS)

Colin, Samuel; Corbett, John; Durt, Thomas; Gross, David

2005-01-01

A set of d 2 vectors in a Hilbert space of dimension d is called equiangular if each pair of vectors encloses the same angle. The projection operators onto these vectors define a POVM which is distinguished by its high degree of symmetry. Measures of this kind are called symmetric informationally complete, or SIC POVMs for short, and could be applied for quantum state tomography. Despite its simple geometrical description, the problem of constructing SIC POVMs or even proving their existence seems to be very hard. It is our purpose to introduce two applications of discrete Wigner functions to the analysis of the problem at hand. First, we will present a method for identifying symmetries of SIC POVMs under Clifford operations. This constitutes an alternative approach to a structure described before by Zauner and Appleby. Further, a simple and geometrically motivated construction for an SIC POVM in dimensions two and three is given (which, unfortunately, allows no generalization). Even though no new structures are found, we hope that the re-formulation of the problem may prove useful for future inquiries

Fabrication of mullite-bonded porous SiC ceramics from multilayer-coated SiC particles through sol-gel and in-situ polymerization techniques

Science.gov (United States)

Ebrahimpour, Omid

In this work, mullite-bonded porous silicon carbide (SiC) ceramics were prepared via a reaction bonding technique with the assistance of a sol-gel technique or in-situ polymerization as well as a combination of these techniques. In a typical procedure, SiC particles were first coated by alumina using calcined powder and alumina sol via a sol-gel technique followed by drying and passing through a screen. Subsequently, they were coated with the desired amount of polyethylene via an in-situ polymerization technique in a slurry phase reactor using a Ziegler-Natta catalyst. Afterward, the coated powders were dried again and passed through a screen before being pressed into a rectangular mold to make a green body. During the heating process, the polyethylene was burnt out to form pores at a temperature of about 500°C. Increasing the temperature above 800°C led to the partial oxidation of SiC particles to silica. At higher temperatures (above 1400°C) derived silica reacted with alumina to form mullite, which bonds SiC particles together. The porous SiC specimens were characterized with various techniques. The first part of the project was devoted to investigating the oxidation of SiC particles using a Thermogravimetric analysis (TGA) apparatus. The effects of particle size (micro and nano) and oxidation temperature (910°C--1010°C) as well as the initial mass of SiC particles in TGA on the oxidation behaviour of SiC powders were evaluated. To illustrate the oxidation rate of SiC in the packed bed state, a new kinetic model, which takes into account all of the diffusion steps (bulk, inter and intra particle diffusion) and surface oxidation rate, was proposed. Furthermore, the oxidation of SiC particles was analyzed by the X-ray Diffraction (XRD) technique. The effect of different alumina sources (calcined Al2O 3, alumina sol or a combination of the two) on the mechanical, physical, and crystalline structure of mullite-bonded porous SiC ceramics was studied in the

Research Progress of Optical Fabrication and Surface-Microstructure Modification of SiC

Directory of Open Access Journals (Sweden)

Fang Jiang

2012-01-01

Full Text Available SiC has become the best candidate material for space mirror and optical devices due to a series of favorable physical and chemical properties. Fine surface optical quality with the surface roughness (RMS less than 1 nm is necessary for fine optical application. However, various defects are present in SiC ceramics, and it is very difficult to polish SiC ceramic matrix with the 1 nm RMS. Surface modification of SiC ceramics must be done on the SiC substrate. Four kinds of surface-modification routes including the hot pressed glass, the C/SiC clapping, SiC clapping, and Si clapping on SiC surface have been reported and reviewed here. The methods of surface modification, the mechanism of preparation, and the disadvantages and advantages are focused on in this paper. In our view, PVD Si is the best choice for surface modification of SiC mirror.

New Possibilities of Power Electronic Structures Using SiC Technology

Directory of Open Access Journals (Sweden)

Robert Sul

2006-01-01

Full Text Available This paper is dedicated to the recent unprecedented boom of SiC electronic technology. The contribution deals with brief survey of those properties. In particular, the differences (both good and bad between SiC electronics technology and well-known silicon VLSI technology are highlighted. Projected performance benefits of SiC electronics are given for several large-scale applications on the end of the contribution. The basic properties of SiC material have been discussed already on the beginning of 80’s, also at our university.

Effects of a proposed rural dental school on regional dental workforce and access to care.

Science.gov (United States)

Wanchek, Tanya N; Rephann, Terance J

2013-01-01

Southwest Virginia is a rural, low-income region with a relatively small dentist workforce and poor oral health outcomes. The opening of a dental school in the region has been proposed by policy-makers as one approach to improving the size of the dentist workforce and oral health outcomes. A policy simulation was conducted to assess how a hypothetical dental school in rural Southwest Virginia would affect the availability of dentists and utilization levels of dental services. The simulation focuses on two channels through which the dental school would most likely affect the region. First, the number of graduates who are expected to remain in the region was varied, based on the extensiveness of the education pipeline used to attract local students. Second, the number of patients treated in the dental school clinic under different dental school clinical models, including the traditional model, a patient-centered clinic model and a community-based clinic model, was varied in the simulation to obtain a range of additional dentists and utilization rates under differing dental school models. Under a set of plausible assumptions, the low yield scenario (ie private school with a traditional clinic) would result in three additional dentists residing in the region and a total of 8090 additional underserved patients receiving care. Under the high yield scenario (ie dental pipeline program with community based clinics) nine new dentists would reside in the region and as many as 18 054 underserved patients would receive care. Even with the high yield scenario and the strong assumption that these patients would not otherwise access care, the utilization rate increases to 68.9% from its current 60.1%. While the new dental school in Southwest Virginia would increase the dentist workforce and utilization rates, the high cost combined with the continued low rate of dental utilization suggests that there may be more effective alternatives to improving oral health in rural areas

SiC nanoparticles as potential carriers for biologically active substances

Science.gov (United States)

Guevara-Lora, Ibeth; Czosnek, Cezary; Smycz, Aleksandra; Janik, Jerzy F.; Kozik, Andrzej

2009-01-01

Silicon carbide SiC thanks to its many advantageous properties has found numerous applications in diverse areas of technology. In this regard, its nanosized forms often with novel properties have been the subject of intense research in recent years. The aim of this study was to investigate the binding of biologically active substances onto SiC nanopowders as a new approach to biomolecule immobilization in terms of their prospective applications in medicine or for biochemical detection. The SiC nanoparticles were prepared by a two-stage aerosol-assisted synthesis from neat hexamethyldisiloxane. The binding of several proteins (bovine serum albumin, high molecular weight kininogen, immunoglobulin G) on SiC particle surfaces was demonstrated at the levels of 1-2 nanograms per mg of SiC. These values were found to significantly increase after suitable chemical modifications of nanoparticle surfaces (by carbodiimide or 3-aminopropyltrietoxysilane treatment). The study of SiC biocompatibility showed a lack of cytotoxicity against macrophages-like cells below the concentration of 1 mg nanoparticles per mL. In summary, we demonstrated the successful immobilization of the selected substances on the SiC nanoparticles. These results including the cytotoxicity study make nano-SiC highly attractive for potential applications in medicine, biotechnology or molecular detection.

Dentoalveolar abscess: A case of poor dental visit and unawareness of dental treatment ?

Science.gov (United States)

Osaghae, I P

2014-12-01

Dentoalveolar abscess is a serious complication that may arise from untreated dental caries, periodontal disease, pericoronitis and facial fractures. The objective of study was to ascertain the dental visit pattern and awareness of dental treatment among patients attending a secondary oral health facility in Benin-City with dentoalveolar abscess. A total of 50 patients that presented with dentoalveolar abscess in the Dental Clinic of Central Hospital between September, 2012 and July, 2013 constituted the study population. Data was collected using unstructured in-depth interview, following a topic guide. Of the 50 patients, 29 (58%) were females, while 21 (42%) were males. Age range was between 3-67 years and the educational status of the patients ranged from illiterate to graduates of tertiary institution. Time interval between onset of pain and presentation of swelling was 1 day to 10 years. Forty-five patients (90%) have heard of dentists. A total of 27 (60%) reported teeth extraction as the only treatment carried out by dentists, 12 (27%) extraction/restoration replacement/treatment and 5 (13%) treatment only. Thirty-seven patients (74%) were first time clinic attendees, 7 (14%) were second time clinic attendees and 6 (12%) were three times and more clinic attendees. This study revealed that patients attending secondary oral health facility with dentoalveolar abscess were dominantly first time dental clinic attendees and exhibited low awareness of treatments offered by dentists. There is need to further investigate the barriers to preventive visits and to improve of awareness of dental treatment among previous dental clinic attendees.

A Blended Learning Course Design in Clinical Pharmacology for Post-graduate Dental Students

Science.gov (United States)

Rosenbaum, Paul-Erik Lillholm; Mikalsen, Øyvind; Lygre, Henning; Solheim, Einar; Schjøtt, Jan

2012-01-01

Postgraduate courses in clinical pharmacology are important for dentists to be updated on drug therapy and information related to their clinical practice, as well as knowledge of relevant adverse effects and interactions. A traditional approach with classroom delivery as the only method to teaching and learning has shortcomings regarding flexibility, individual learning preferences, and problem based learning (PBL) activities compared to online environments. This study examines a five week postgraduate course in clinical pharmacology with 15 hours of lectures and online learning activities, i.e. blended course design. Six postgraduate dental students participated and at the end of the course they were interviewed. Our findings emphasize that a blended learning course design can be successfully used in postgraduate dental education. Key matters for discussion were time flexibility and location convenience, change in teacher’s role, rein-forced learning strategies towards professional needs, scarcity in online communication, and proposed future utilization of e-learning components. PMID:23248716

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

Influence of microstructure on hydrothermal corrosion of chemically vapor processed SiC composite tubes

Science.gov (United States)

Kim, Daejong; Lee, Ho Jung; Jang, Changheui; Lee, Hyeon-Geun; Park, Ji Yeon; Kim, Weon-Ju

2017-08-01

Multi-layered SiC composites consisting of monolithic SiC and a SiCf/SiC composite are one of the accident tolerant fuel cladding concepts in pressurized light water reactors. To evaluate the integrity of the SiC fuel cladding under normal operating conditions of a pressurized light water reactor, the hydrothermal corrosion behavior of multi-layered SiC composite tubes was investigated in the simulated primary water environment of a pressurized water reactor without neutron fluence. The results showed that SiC phases with good crystallinity such as Tyranno SA3 SiC fiber and monolithic SiC deposited at 1200 °C had good corrosion resistance. However, the SiC phase deposited at 1000 °C had less crystallinity and severely dissolved in water, particularly the amorphous SiC phase formed along grain boundaries. Dissolved hydrogen did not play a significant role in improving the hydrothermal corrosion resistance of the CVI-processed SiC phases containing amorphous SiC, resulting in a significant weight loss and reduction of hoop strength of the multi-layered SiC composite tubes after corrosion.

Success and Survival Rates of Dental Implants Restored at an Undergraduate Dental Clinic: A 13-Year Retrospective Study with a Mean Follow-up of 5.8 Years.

Science.gov (United States)

Daneshvar, Shahrzad S; Matthews, Debora C; Michuad, Pierre-Luc; Ghiabi, Edmond

2016-01-01

The purpose of this study was to evaluate the clinical, radiographic, and patient-based outcomes of dental implants placed at an undergraduate student dental clinic. A retrospective study was performed to determine the success and survival rates of dental implants placed at the undergraduate dental clinic at Dalhousie University between January 1999 and January 2012. Only patients with a minimum of 1-year follow-up were included. Clinical and radiographic assessments determined implant success and survival rates. Questionnaires recorded patients' satisfaction with esthetics, comfort, and ease of hygiene. Of the 352 patients (n = 591 implants) who received implants over 13 years, 165 patients completed the clinical and radiographic examinations. By the end of the study period, demographic information and implant characteristics were collected for 111 (n = 217 implants; 47.5% in the maxilla, 52.6% in the mandible) of these patients. Of those assessed clinically, 36.4% were males and 63.6% females, with a mean age of 56.1 ± 14.15 years (range, 17 to 86 years) at the time of implant placement. The mean follow-up period was 5.8 years (range, 1 to 13 years). The overall implant success and survival rates were 88.0% and 97.2%, respectively. No observable bone loss was evident in 88.0% of the surviving implants. There were no implant fractures. Most patients (91.2%) were very satisfied with the implant restoration appearance, 88.0% were very comfortable with the implant, 92.6% were very satisfied with their ability to chew, and 84.8% reported easy hygiene maintenance at the implant sites. Implant success and survival in an undergraduate student clinic were comparable to those reported in the literature. It seems that inexperienced students were able to provide restorations that were very satisfying to the patients.

Challenges in Switching SiC MOSFET without Ringing

DEFF Research Database (Denmark)

Li, Helong; Munk-Nielsen, Stig

2014-01-01

Switching SiC MOSFET without ringing in high frequency applications is important for meeting the EMI (ElectroMagnetic Interference) standard. Achieving a clean switching waveform of SiC MOSFET without additional components is becoming a challenge. In this paper, the switching oscillation mechanis...

MAX Phase Modified SiC Composites for Ceramic-Metal Hybrid Cladding Tubes

International Nuclear Information System (INIS)

Jung, Yang-Il; Kim, Sun-Han; Park, Dong-Jun; Park, Jeong-Hwan; Park, Jeong-Yong; Kim, Hyun-Gil; Koo, Yang-Hyun

2015-01-01

A metal-ceramic hybrid cladding consists of an inner zirconium tube, and an outer SiC fiber-matrix SiC ceramic composite with surface coating as shown in Fig. 1 (left-hand side). The inner zirconium allows the matrix to remain fully sealed even if the ceramic matrix cracks through. The outer SiC composite can increase the safety margin by taking the merits of the SiC itself. In addition, the outermost layer prevents the dissolution of SiC during normal operation. On the other hand, a ceramic-metal hybrid cladding consists of an outer zirconium tube, and an inner SiC ceramic composite as shown in Fig. 1 (right-hand side). The outer zirconium protects the fuel rod from a corrosion during reactor operation, as in the present fuel claddings. The inner SiC composite, additionally, is designed to resist the severe oxidation under a postulated accident condition of a high-temperature steam environment. Reaction-bonded SiC was fabricated by modifying the matrix as the MAX phase. The formation of Ti 3 SiC 2 was investigated depending on the compositions of the preform and melt. In most cases, TiSi 2 was the preferential phase because of its lowest melting point in the Ti-Si-C system. The evidence of Ti 3 SiC 2 was the connection with the pressurizing

DENTAL SCHOOL PLANNING.

Science.gov (United States)

GALAGAN, DONALD J.

THIS DISCUSSION PRESENTS A COMPLETE PICTURE OF THE CURRENT STATE OF DENTAL EDUCATION WITH SUGGESTIONS FOR MEETING THE DEMANDS FOR DENTAL STAFF AND FACILITIES. THE AREAS INVESTIGATED ARE (1) OBJECTIVES IN DENTAL EDUCATION--COURSES, TEACHING MODES, INNOVATIONS IN CURRICULUM, COORDINATION OF BASIC AND CLINICAL INSTRUCTION, (2) FACILITY…

Packaging Technologies for 500C SiC Electronics and Sensors

Science.gov (United States)

Chen, Liang-Yu

2013-01-01

Various SiC electronics and sensors are currently under development for applications in 500C high temperature environments such as hot sections of aerospace engines and the surface of Venus. In order to conduct long-term test and eventually commercialize these SiC devices, compatible packaging technologies for the SiC electronics and sensors are required. This presentation reviews packaging technologies developed for 500C SiC electronics and sensors to address both component and subsystem level packaging needs for high temperature environments. The packaging system for high temperature SiC electronics includes ceramic chip-level packages, ceramic printed circuit boards (PCBs), and edge-connectors. High temperature durable die-attach and precious metal wire-bonding are used in the chip-level packaging process. A high temperature sensor package is specifically designed to address high temperature micro-fabricated capacitive pressure sensors for high differential pressure environments. This presentation describes development of these electronics and sensor packaging technologies, including some testing results of SiC electronics and capacitive pressure sensors using these packaging technologies.

Implementing tobacco use treatment guidelines in public health dental clinics in New York City.

Science.gov (United States)

Shelley, Donna; Anno, Jaime; Tseng, Tuo-Yen; Calip, Greg; Wedeles, John; Lloyd, Madeleine; Wolff, Mark S

2011-04-01

In this study we evaluated the effect of a multicomponent intervention to implement the Public Health Service (PHS) guideline Treating Tobacco Use and Dependence in six randomly selected dental clinics in New York University's College of Dentistry. The main outcome measure-provider adherence to tobacco use treatment guidelines-was assessed by auditing a random selection of patient charts pre (698) and post (641) intervention. The intervention components included a chart reminder and referral system, free nicotine replacement therapy (NRT), and provider training and feedback. The results showed that rates of screening for tobacco use did not change between pre and post test chart audits. However, providers were significantly more likely to offer advice (28.4 percent pre, 49 percent post), assess readiness to quit (17.8 percent pre, 29.9 percent post), and offer assistance (6.5 percent pre and 15.6 percent post) in the post test period. Increases in NRT distribution were associated with booster training sessions but declined in the time periods between those trainings. Research is needed to further define sustainable strategies for implementing tobacco use treatment in dental clinics. The results of this study suggest the feasibility and effectiveness of using a tailored multicomponent approach to implement tobacco use treatment guidelines in dental clinics.

SiC for microwave power transistors

Energy Technology Data Exchange (ETDEWEB)

Sriram, S.; Siergiej, R.R.; Clarke, R.C.; Agarwal, A.K.; Brandt, C.D. [Northrop Grumman Sci. and Technol. Center, Pittsburgh, PA (United States)

1997-07-16

The advantages of SiC for high power, microwave devices are discussed. The design considerations, fabrication, and experimental results are described for SiC MESFETs and SITs. The highest reported f{sub max} for a 0.5 {mu}m MESFET using semi-insulating 4H-SiC is 42 GHz. These devices also showed a small signal gain of 5.1 dB at 20 GHz. Other 4H-SiC MESFETs have shown a power density of 3.3 W/mm at 850 MHz. The largest SiC power transistor reported is a 450 W SIT measured at 600 MHz. The power output density of this SIT is 2.5 times higher than that of comparable silicon devices. SITs have been designed to operate as high as 3.0 GHz, with a 3 cm periphery part delivering 38 W of output power. (orig.) 28 refs.

Formation mechanism of SiC in C-Si system by ion irradiation

International Nuclear Information System (INIS)

Hishita, Shunichi; Aizawa, Takashi; Suehara, Shigeru; Haneda, Hajime

2003-01-01

The irradiation effects of 2 MeV He + , Ne + , and Ar + ions on the film structure of the C-Si system were investigated with RHEED and XPS. The ion dose dependence of the SiC formation was kinetically analyzed. The SiC formation at moderate temperature was achieved by 2 MeV ion irradiation when the thickness of the initial carbon films was appropriate. The evolution process of the SiC film thickness consisted of the 3 stages. The first stage was the steep increase of the SiC, and was governed by the inelastic collision. The second was the gentle increase of the SiC, and was governed by the diffusion. The last was the decrease of the SiC, and was caused by the sputtering. The formation mechanism of the SiC was discussed. (author)

Residual stress and mechanical properties of SiC ceramic by heat treatment

International Nuclear Information System (INIS)

Yoon, H.K.; Kim, D.H.; Shin, B.C.

2007-01-01

Full text of publication follows: Silicon carbide is a compound of relatively low density, high hardness, elevated thermal stability and good thermal conductivity, resulting in good thermal shock resistance. Because of these properties, SiC materials are widely used as abrasives and refractories. In this study, SiC single and poly crystals was grown by the sublimation method using the SiC seed crystal and SiC powder as the source material. Mechanical properties of SiC single and poly crystals are carried out by using the nano-indentation method and small punch test after the heat treatment. As a result, mechanical properties of SiC poly crystal had over double than single. And SiC single and poly crystals were occurred residual stress, but residual stress was shown relaxant properties by the effect of heat treatment. (authors)

Irradiation damages in Ti3SiC2

International Nuclear Information System (INIS)

Nappe, J.C.; Grosseau, Ph.; Guilhot, B.; Audubert, F.; Beauvy, M.

2007-01-01

Carbides, by their remarkable properties, are considered as possible materials (fuel cans) in reactor of generation IV. Among those studied, Ti 3 SiC 2 is particularly considered because it joins both the ceramics and metals properties. Nevertheless, its behaviour under irradiation is not known. Characterizations have been carried out on samples irradiated at 75 MeV krypton ions. They have revealed that TiO 2 (formed at the surface of Ti 3 SiC 2 ) is pulverized by the irradiation and that the crystal lattice of Ti 3 SiC 2 dilates with c. (O.M.)

TRISO coated fuel particles with enhanced SiC properties

International Nuclear Information System (INIS)

Lopez-Honorato, E.; Tan, J.; Meadows, P.J.; Marsh, G.; Xiao, P.

2009-01-01

The silicon carbide (SiC) layer used for the formation of TRISO coated fuel particles is normally produced at 1500-1650 deg. C via fluidized bed chemical vapor deposition from methyltrichlorosilane in a hydrogen environment. In this work, we show the deposition of SiC coatings with uniform grain size throughout the coating thickness, as opposed to standard coatings which have larger grain sizes in the outer sections of the coating. Furthermore, the use of argon as the fluidizing gas and propylene as a carbon precursor, in addition to hydrogen and methyltrichlorosilane, allowed the deposition of stoichiometric SiC coatings with refined microstructure at 1400 and 1300 deg. C. The deposition of SiC at lower deposition temperatures was also advantageous since the reduced heat treatment was not detrimental to the properties of the inner pyrolytic carbon which generally occurs when SiC is deposited at 1500 deg. C. The use of a chemical vapor deposition coater with four spouts allowed the deposition of uniform and spherical coatings.

Assessment of volatile organic compounds and particulate matter in a dental clinic and health risks to clinic personnel.

Science.gov (United States)

Hong, Yu-Jue; Huang, Yen-Ching; Lee, I-Long; Chiang, Che-Ming; Lin, Chitsan; Jeng, Hueiwang Anna

2015-01-01

This study was conducted to assess (1) levels of volatile organic compounds (VOCs) and particulate matter (PM) in a dental clinic in southern Taiwan and (2) dental care personnel's health risks associated with due to chronic exposure to VOCs. An automatic, continuous sampling system and a multi-gas monitor were employed to quantify the air pollutants, along with environmental comfort factors, including temperature, CO2, and relative humidity at six sampling sites in the clinic over eight days. Specific VOC compounds were identified and their concentrations were quantified. Both non-carcinogenic and carcinogenic VOC compounds were assessed based on the US Environmental Protection Agency's Principles of Health Risk Assessment in terms of whether those indoor air pollutants increased health risks for the full-time dental care professionals at the clinic. Increased levels of VOCs were recorded during business hours and exceeded limits recommended by the Taiwan Environmental Protection Agency. A total of 68 VOC compounds were identified in the study area. Methylene methacrylate (2.8 ppm) and acetone (0.176 ppm) were the only two non-carcinogenic compounds that posed increased risks for human health, yielding hazard indexes of 16.4 and 4.1, respectively. None of the carcinogenic compounds increased cancer risk. All detected PM10 levels ranged from 20 to 150 μg/m(3), which met the Taiwan EPA and international limits. The average PM10 level during business hours was significantly higher than that during non-business hours (P = 0.04). Improved ventilation capacity in the air conditioning system was recommended to reduce VOCs and PM levels.

Detail study of SiC MOSFET switching characteristics

DEFF Research Database (Denmark)

Li, Helong; Munk-Nielsen, Stig

2014-01-01

This paper makes detail study of the latest SiC MOSFETs switching characteristics in relation to gate driver maximum current, gate resistance, common source inductance and parasitic switching loop inductance. The switching performance of SiC MOSFETs in terms of turn on and turn off voltage...

[Evidence-based quality assessment of 10-year orthodontic clinical trials in 4 major dental journals].

Science.gov (United States)

Sun, Yan-nan; Lei, Fei-fei; Cao, Yan-li; Fu, Min-kui

2010-02-01

To assess the quality of orthodontic clinical trials published in 4 major dental journals in the past 10 years and establish the reference standard for orthodontic clinical trials and quality control of dental journals. All the clinical trials published in Chinese Journal of Stomatology, West China Journal of Stomatology, Journal of Practice Stomatology and Chinese Journal of Orthodontics from 1999 to 2008 were searched. The demographic information of the papers was extracted and the quality of the clinical trials according to the consolidated standards of reporting trials (CONSORT) was assessed. Four hundred and ninety-four clinical trials were retrieved, and 21.3% (105/494) of them were supported by grants. For the study design, only 26.1% (129/494) were prospective studies, and 3.8% (19/494) were randomized clinical trials. It was hard to evaluate precisely due to the lack of information about the details of the study designs. For the randomized clinical trials, the lack of details for randomization, allocation concealment, blinding and intention to treat compromised the quality. The general quality of clinical trials in orthodontics is poor. It needs to be improved both in the clinical study design and the paper writing.

From dental science to clinical practice: Knowledge translation and evidence-based dentistry principles

Directory of Open Access Journals (Sweden)

Kelvin I. Afrashtehfar

2017-07-01

Full Text Available It has been claimed that in order to decrease the gap between what we know and what we do, research findings must be translated from knowledge to action. Such practices better enable dentists to make evidence-based decisions instead of personal ideas and judgments. To this end, this literature review aims to revisit the concepts of knowledge translation and evidence-based dentistry (EBD and depict their role and influence within dental education. It addresses some possible strategies to facilitate knowledge translation (KT, encourage dental students to use EBD principles, and to encourage dental educators to create an environment in which students become self-directed learners. It concludes with a call to develop up-to-date and efficient online platforms that could grant dentists better access to EBD sources in order to more efficiently translate research evidence into the clinic.

From dental science to clinical practice: Knowledge translation and evidence-based dentistry principles.

Science.gov (United States)

Afrashtehfar, Kelvin I; Assery, Mansour K

2017-07-01

It has been claimed that in order to decrease the gap between what we know and what we do, research findings must be translated from knowledge to action. Such practices better enable dentists to make evidence-based decisions instead of personal ideas and judgments. To this end, this literature review aims to revisit the concepts of knowledge translation and evidence-based dentistry (EBD) and depict their role and influence within dental education. It addresses some possible strategies to facilitate knowledge translation (KT), encourage dental students to use EBD principles, and to encourage dental educators to create an environment in which students become self-directed learners. It concludes with a call to develop up-to-date and efficient online platforms that could grant dentists better access to EBD sources in order to more efficiently translate research evidence into the clinic.

Dental Environmental Noise Evaluation and Health Risk Model Construction to Dental Professionals

OpenAIRE

Ma, Kuen Wai; Wong, Hai Ming; Mak, Cheuk Ming

2017-01-01

Occupational noise is unavoidably produced from dental equipment, building facilities, and human voices in the dental environment. The purpose of this study was to investigate the effect of occupational noise exposure on the dental professionals’ health condition. The psychoacoustics approach noise exposure assessment followed by the health risk assessment was carried on at the paediatric dentistry clinic and the dental laboratory in the Prince Philip Dental Hospital of Hong Kong. The A-weigh...

Advances in wide bandgap SiC for optoelectronics

DEFF Research Database (Denmark)

Ou, Haiyan; Ou, Yiyu; Argyraki, Aikaterini

2014-01-01

Silicon carbide (SiC) has played a key role in power electronics thanks to its unique physical properties like wide bandgap, high breakdown field, etc. During the past decade, SiC is also becoming more and more active in optoelectronics thanks to the progress in materials growth and nanofabrication...

Dental students′ compliance with antibiotic prescribing guidelines for dental infections in children

Directory of Open Access Journals (Sweden)

Yee Chen Wong

2016-01-01

Full Text Available Context: To investigate the antibiotic prescribing training received by dental students, clinical experience in treating child patients, awareness of antibiotic prescribing guidelines, preparedness in antibiotic prescribing, and compliance with antibiotic prescribing guidelines for the management of dental infections in children. Methods: This was a cross-sectional study involving final year dentals students from Malaysian and Asian dental schools. A self-administered questionnaire consisting of five clinical case scenarios was e-mailed to all final year students at selected dental schools. Students′ responses were compared for each clinical case scenario with the prescribing guidelines of the American Academy of Pediatric Dentistry and the American Dental Association. Compliance in each scenario was tested for association with their preparedness in antibiotic prescribing, previous training on antibiotic prescribing and awareness of antibiotic prescribing guidelines using Chi-square test. Data collected were analyzed using SPSS statistics version 20. Results: A total of 108 completed responses were received. About 74 (69% students were from Malaysian dental schools. The compliance rate with prescribing guidelines ranged from 15.7% to 43.5%. Those attending Malaysian dental schools (47.3% and those who had treated child patient more often (46.3% were more likely (P < 0.05 to be aware of the guidelines. Those who had received antibiotic prescribing training (21.3% were more likely to think they were well prepared in antibiotic prescribing (P < 0.05. Conclusions: Final year dental students had low awareness and compliance with antibiotic prescribing guidelines. Further research is needed to investigate how compliance with the guidelines may be enhanced.

Research Progress on Preparation for Biomass-based SiC Ceramic

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CUI He-shuai

2017-08-01

Full Text Available Silicon carbide (SiC ceramics prepared by the conventional process has excellent properties and wide application prospects, but the increased cost of high-temperature preparation process restricts its further development. In contrast, the abundant porous structure of biomass makes itself to be ideal replacement of SiC ceramic prepared at low temperature. This paper reviewed the structure characteristics, preparation methods, pyrolysis mechanism and influence parameters of biomass-based SiC ceramic, and eventually explored the current problems and development trends of the pretreatment of carbon source and silicon source, the pyrolysis process and the application research on the preparation for biomass-based SiC ceramic.

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.

Dental student attitudes towards communication skills instruction and clinical application.

Science.gov (United States)

McKenzie, Carly T

2014-10-01

This study investigated dental students' attitudes towards communication skills instruction and clinical application and explored the impact of a one-semester course and year in school on students' attitudes, measured by the Communication Skills Attitude Scale. Demographic characteristics and self-assessment of communication skills were also analyzed. The study employed a pretest-posttest survey design combined with cross-sectional data. Participants were first- and fourth-year students at a U.S. dental school. Out of a possible 120 students, 106 (fifty-seven D1 and forty-nine D4) participated in the pretest, an 88 percent response rate; out of a possible 121 students, 115 (fifty-seven D1 and fifty-eight D4) participated in the posttest, a 95 percent response rate. In the results, D4 students consistently demonstrated less positive attitudes towards communication skills instruction and more negative attitudes regarding the importance of interpersonal skills in clinical encounters than did their D1 counterparts. A single communications course had no discernible effect on attitudes or self-assessments for either cohort. Females reported more positive attitudes towards clinical application of interpersonal skills than did males. Gender significantly interacted with two demographic variables: primary language and parent as health care professional. Female children of health care professionals reported poorer attitudes towards clinical communication skills training and application than did their male counterparts. Generally, parental occupation in health care moderated the decrease in positive attitudes over time towards clinical usefulness of communication skills. The D4 students rated their communication skills higher than did the D1 students. Students who demonstrated more positive attitudes towards communication skills training and application were more likely to say their own skills needed improvement.

Development of reflective judgement in the pre-doctoral dental clinical curriculum.

Science.gov (United States)

Boyd, L D

2008-08-01

When dental students begin patient care in the clinical curriculum, they are required to move from the well-defined problems of the classroom to the more ambiguous and real life problems encountered in the context of patient care in the clinical setting. This change in learning environment requires development of reflective thinking. Reflective thinking refers to the process of thinking about uncertainty or ill-defined problems. King and Kitchener refer to the outcome of the reflective thinking process as reflective judgement. The purpose of this study was to explore the development of reflective judgement in the initial phase of the clinical curriculum. This exploratory study used a case study approach with qualitative methods. A convenience sample of third year predoctoral dental students (n = 16) volunteered to participate in writing a clinic journal and semi-structured interviews at three time points over a time period of one year. Student compliance in writing clinical journals was poor; therefore the qualitative data was primarily gathered from interview transcripts. The qualitative interview data were analysed using a coding scheme based on King and Kitchener's Reflective Judgement Model of Intellectual Development. The Cronbach alpha was 0.76 for reliability of the coding scheme. Based on the analysis of interview data, the there was an average growth in reflective judgement over the year from Stage 4.89 to 5.59 for an overall change of +0.70. Additional research is needed to explore the growth in reflective judgement over the final year of the clinical curriculum as well as to identify the most effective educational strategies to facilitate growth in reflective judgment.

Dental Anomalies: An Update

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Fatemeh Jahanimoghadam

2016-01-01

Full Text Available Dental anomalies are usual congenital malformation that can happen either as isolated findings or as a part of a syndrome. Developmental anomalies influencing the morphology exists in both deciduous and permanent dentition and shows different forms such as gemination, fusion, concrescence, dilaceration, dens evaginatus (DE, enamel pearls, taurodontism or peg-shaped laterals. All These anomalies have clinical significance concerning aesthetics, malocclusion and more necessary preparing of the development of dental decays and oral diseases. Through a search in PubMed, Google, Scopus and Medline, a total of eighty original research papers during 1928-2016 were found with the keywords such as dental anomaly, syndrome, tooth and hypodontia. One hundred review titles were identified, eighty reviews were retrieved that were finally included as being relevant and of sufficient quality. In this review, dental anomalies including gemination, fusion, concrescence, dilaceration, dens invaginatus, DE, taurodontism, enamel pearls, fluorosis, peg-shaped laterals, dentinal dysplasia, regional odontodysplasia and hypodontia are discussed. Diagnosing dental abnormality needs a thorough evaluation of the patient, involving a medical, dental, familial and clinical history. Clinical examination and radiographic evaluation and in some of the cases, specific laboratory tests are also needed. Developmental dental anomalies require careful examination and treatment planning. Where one anomaly is present, clinicians should suspect that other anomalies may also be present. Moreover, careful clinical and radiographical examination is required. Furthermore, more complex cases need multidisciplinary planning and treatment.

Fabrication of Multi-Layerd SiC Composite Tube for LWR Applications

Energy Technology Data Exchange (ETDEWEB)

Kim, Daejong; Jung, Choonghwan; Kim, Weonju; Park, Jiyeon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Jongmin [Chungnam National Univ., Daejeon (Korea, Republic of)

2013-05-15

In this study, the chemical vapor deposition (CVD) and chemical vapor infiltration (CVI) methods were employed for the fabrication of the composite tubes. SiC ceramics and SiC-based composites have recently been studied for LWR fuel cladding applications because of good mechanical/physical properties, neutron irradiation resistance and excellent compatibility with coolant under severe accident. A multi-layered SiC composite tube as the nuclear fuel cladding is composed of the monolith SiC inner layer, SiC/SiC composite intermediate layer, and monolith SiC outer layer. Since all constituents should be highly pure, stoichiometric to achieve the good properties, it has been considered that the chemical process is a well-suited technique for the fabrication of the SiC phases.

Determining the fracture resistance of advanced SiC fiber reinforced SiC matrix composites

International Nuclear Information System (INIS)

Nozawa, T.; Katoh, Y.; Kishimoto, H.

2007-01-01

Full text of publication follows: One of the perceived advantages for highly-crystalline and stoichiometric silicon carbide (SiC) and SiC composites, e.g., advanced SiC fiber reinforced chemically-vapor-infiltrated (CVI) SiC matrix composites, is the retention of fast fracture properties after neutron irradiation at high-temperatures (∼1000 deg. C) to intermediate-doses (∼15 dpa). Accordingly, it has been clarified that the maximum allowable stress (or strain) limit seems unaffected in certain irradiation conditions. Meanwhile, understanding the mechanism of crack propagation from flaws, as potential weakest link to cause composite failure, is somehow lacking, despite that determining the strength criterion based on the fracture mechanics will eventually become important considering the nature of composites' fracture. This study aims to evaluate crack propagation behaviors of advanced SiC/SiC and to provide fundamentals on fracture resistance of the composites to define the strength limit for the practical component design. For those purposes, the effects of irreversible energies related to interfacial de-bonding, fiber bridging, and microcrack forming on the fracture resistance were evaluated. Two-dimensional SiC/SiC composites were fabricated by CVI or nano-infiltration and transient-eutectic-phase (NITE ) methods. Hi-Nicalon TM Type-S or Tyranno TM -SA fibers were used as reinforcements. In-plane mode-I fracture resistance was evaluated by the single edge notched bend technique. The key finding is the continuous Load increase with the crack growth for any types of advanced composites, while many studies specified the gradual load decrease for the conventional composites once the crack initiates. This high quasi-ductility appeared due primarily to high friction (>100 MPa) at the fiber/matrix interface using rough SiC fibers. The preliminary analysis based on the linear elastic fracture mechanics, which does not consider the effects of irreversible energy

Comparisons between the attitudes of medical and dental students toward the clinical importance of gross anatomy and physiology.

Science.gov (United States)

Olowo-Ofayoku, Anthony; Moxham, Bernard John

2014-10-01

Marked changes are occurring within both the medical and dental curricula and new ways of teaching the basic sciences have been devised and traditional methods (e.g., dissection for gross anatomy and of bench-based animal preparations for physiology) are increasingly no longer the norm. Although there is much anecdotal evidence that students are not in favor of such changes, there is little evidence for this based on quantitative analyses of students' attitudes. Using Thurstone and Chave attitude analyses, we assessed the attitudes of first year medical and dental students at Cardiff University toward gross anatomy and physiology in terms of their perceived clinical importance. In addition, we investigated the appropriateness ("fitness for purpose") of teaching methodologies used for anatomy and physiology. The hypotheses tested recognized the possibility that medical and dental students differed in their opinions, but that they had a preference to being taught gross anatomy through the use of dissection and had no preference for physiology teaching. It was found that both medical and dental students displayed positive attitudes toward the clinical relevance of gross anatomy and that they preferred to be taught by means of dissection. Although both medical and dental students displayed positives attitudes toward the clinical relevance of physiology, this was greater for the medical students. Both medical and dental students showed a preference for being taught physiology through didactic teaching in small groups but the medical students also appreciated being taught by means of practicals. Overall, this study highlights the expectations that students have for the basic science foundation teaching within their professional training and signals a preference for being taught experientially/practically. Differences were discerned between medical and dental students that might reflect the direct association between systems physiology and pathophysiology and the

Integration of basic sciences and clinical sciences in oral radiology education for dental students.

Science.gov (United States)

Baghdady, Mariam T; Carnahan, Heather; Lam, Ernest W N; Woods, Nicole N

2013-06-01

Educational research suggests that cognitive processing in diagnostic radiology requires a solid foundation in the basic sciences and knowledge of the radiological changes associated with disease. Although it is generally assumed that dental students must acquire both sets of knowledge, little is known about the most effective way to teach them. Currently, the basic and clinical sciences are taught separately. This study was conducted to compare the diagnostic accuracy of students when taught basic sciences segregated or integrated with clinical features. Predoctoral dental students (n=51) were taught four confusable intrabony abnormalities using basic science descriptions integrated with the radiographic features or taught segregated from the radiographic features. The students were tested with diagnostic images, and memory tests were performed immediately after learning and one week later. On immediate and delayed testing, participants in the integrated basic science group outperformed those from the segregated group. A main effect of learning condition was found to be significant (pbasic sciences integrated with clinical features produces higher diagnostic accuracy in novices than teaching basic sciences segregated from clinical features.

Ag Transport Through Non-Irradiated and Irradiated SiC

Energy Technology Data Exchange (ETDEWEB)

Szlufarska, Izabela [Univ. of Wisconsin, Madison, WI (United States); Morgan, Dane [Univ. of Wisconsin, Madison, WI (United States); Blanchard, James [Univ. of Wisconsin, Madison, WI (United States)

2016-01-11

Silicon carbide is the main barrier to diffusion of fission products in the current design of TRistuctural ISOtropic (TRISO) coated fuel particles, and Ag is one of the few fission products that have been shown to escape through this barrier. Because the SiC coating in TRISO is exposed to radiation throughout the lifetime of the fuel, understanding of how radiation changes the transport of the fission products is essential for the safety of the reactor. The goals of this project are: (i) to determine whether observed variation in integral release measurements of Ag through SiC can be explained by differences in grain size and grain boundary (GB) types among the samples; (2) to identify the effects of irradiation on diffusion of Ag through SiC; (3) to discover phenomena responsible for significant solubility of Ag in polycrystalline SiC. To address these goals, we combined experimental analysis of SiC diffusion couples with modeling studies of diffusion mechanisms through bulk and GBs of this material. Comparison between results obtained for pristine and irradiated samples brings in insights into the effects of radiation on Ag transport.

Ag Transport Through Non-Irradiated and Irradiated SiC

International Nuclear Information System (INIS)

Szlufarska, Izabela; Morgan, Dane; Blanchard, James

2016-01-01

Silicon carbide is the main barrier to diffusion of fission products in the current design of TRistuctural ISOtropic (TRISO) coated fuel particles, and Ag is one of the few fission products that have been shown to escape through this barrier. Because the SiC coating in TRISO is exposed to radiation throughout the lifetime of the fuel, understanding of how radiation changes the transport of the fission products is essential for the safety of the reactor. The goals of this project are: (i) to determine whether observed variation in integral release measurements of Ag through SiC can be explained by differences in grain size and grain boundary (GB) types among the samples; (2) to identify the effects of irradiation on diffusion of Ag through SiC; (3) to discover phenomena responsible for significant solubility of Ag in polycrystalline SiC. To address these goals, we combined experimental analysis of SiC diffusion couples with modeling studies of diffusion mechanisms through bulk and GBs of this material. Comparison between results obtained for pristine and irradiated samples brings in insights into the effects of radiation on Ag transport.

Evaluation of the effect of early clinical exposure on professional attitude of dental students of Shahid Sadoughi University of Medical Sciences in 2011-2012

Directory of Open Access Journals (Sweden)

H. Aghili

2013-06-01

Full Text Available Introduction : Learning dentistry could have many tension and anxieties like encountering to a strange clinical environment. Early clinical exposure (ECE is supposed to control these stresses. ECE program is an increasingly widespread component of educational curriculum. This study aims to determine the effect of early clinical exposure on the attitude of dental students’ towards dental education and profession. Methods: An analytic study was performed on all 72 dental students studying basic science at Faculty of Dentistry of Shahid Sadoughi University of Medical Sciences consisted of a short term course of introduction to clinical environment in academic year of 2011-2012. Every 12 students attended in an one day ECE course from 8 AM to 1 PM. Students ' attitude towards dental profession and education were assessed by a questionnaire included 25 items before and after the course .For data analysis descriptive paired-t-test was used. Results: All students completed the questionnaires. Students' attitude towards dental education and profession was evaluated. Mean score of students' attitude before and after exposure to clinical environment were 94.6 and 100.5 respectively .Significant differences were found in the students' attitude before and after the course (P=0.001 Conclusion: Based on the results of this study, we found a positive effect of early clinical exposure on attitudes of first and second year dental students. Demographic variations had an effect on the students' attitude .Therefore we suggest that early clinical exposure should be added to educational curriculum of dental students.

Managing dental erosion.

Science.gov (United States)

Curtis, Donald A; Jayanetti, Jay; Chu, Raymond; Staninec, Michal

2012-01-01

The clinical signs of dental erosion are initially subtle, yet often progress because the patient remains asymptomatic, unaware and uninformed. Erosion typically works synergistically with abrasion and attrition to cause loss of tooth structure, making diagnosis and management complex. The purpose of this article is to outline clinical examples of patients with dental erosion that highlight the strategy of early identification, patient education and conservative restorative management. Dental erosion is defined as the pathologic chronic loss of dental hard tissues as a result of the chemical influence of exogenous or endogenous acids without bacterial involvement. Like caries or periodontal disease, erosion has a multifactorial etiology and requires a thorough history and examination for diagnosis. It also requires patient understanding and compliance for improved outcomes. Erosion can affect the loss of tooth structure in isolation of other cofactors, but most often works in synergy with abrasion and attrition in the loss of tooth structure (Table 1). Although erosion is thought to be an underlying etiology of dentin sensitivity, erosion and loss of tooth structure often occurs with few symptoms. The purpose of this article is threefold: first, to outline existing barriers that may limit early management of dental erosion. Second, to review the clinical assessment required to establish a diagnosis of erosion. And third, to outline clinical examples that review options to restore lost tooth structure. The authors have included illustrations they hope will be used to improve patient understanding and motivation in the early management of dental erosion.

Preparation and infrared absorption properties of buried SiC layers

International Nuclear Information System (INIS)

Yan Hui; Chen Guanghua; Wong, S.P.; Kwok, R.W.M.

1997-01-01

Buried SiC layers were formed by using a metal vapor vacuum arc (MEVVA) ion source, with C + ions implanted into Si substrates under different doses. In the present study, the extracted voltage was 50 kV and the ion dose was varied from 3.0 x 10 17 to 1.6 x 10 18 cm -2 . According to infrared absorption measurements, it was fount that the structure of the buried SiC layers depended on the ion dose. Moreover, the results also demonstrated that the buried SiC layers including cubic crystalline SiC could be synthesized at an averaged substrate temperature of lower than 400 degree C with the MEVVA ion source

Dental Fear and Delayed Dental Care in Appalachia-West Virginia.

Science.gov (United States)

Wiener, R Constance

2015-08-01

The people of Appalachia-West Virginia are culturally unique and are known to have oral health disparities. The purpose of this study was to evaluate dental fear in relation to delayed dental care as a factor influencing oral health behaviors within this culture. A cross sectional study design was used. Participants were urgent care patients in a university dental clinic. The sample included 140 adults over age 18 years. The Dental Fear Survey was used to determine dental fear level. Self-report of delayed dental care was provided by the participants. The Dental Fear Survey was dichotomized at score 33, with higher scores indicating dental fear. The prevalence of dental fear was 47.1% (n=66). There was a significant association of dental fear and dental delay. The unadjusted odds ratio was 2.87 (95% CI: 1.17, 7.04; p=0.021). The adjusted odds ratio was 3.83 (95%CI: 1.14, 12.82; p=0.030), controlling for tobacco use, perceived oral health status, pain, and last dental visit. A difference in dental delay between men and women was not present in this sample. The only significant variable in delayed dental care was dental fear. In Appalachia-West Virginia, there remains a high level of dental fear, despite advances in dental care, techniques, and procedures. Copyright © 2015 The American Dental Hygienists’ Association.

Temperature Dependence of Mechanical Properties of TRISO SiC Coatings

International Nuclear Information System (INIS)

Kim, Do Kyung; Park, Kwi Il; Lee, Hyeon Keun; Seong, Young Hoon; Lee, Seung Jun

2009-04-01

SiC coating layer has been introduced as protective layer in TRISO nuclear fuel particle of high temperature gas cooled reactor (HTGR) due to excellent mechanical stability at high temperature. It is important to study for high temperature stability in SiC coating layers, because TRISO fuel particles were operating at high temperature around 1000 .deg. C. In this study, the nanoindentation test and micro tensile test were conducted in order to measure the mechanical properties of SiC coating layers at elevated temperature. SiC coating film was fabricated on the carbon substrate using chemical vapor deposition process with different microstructures and thicknesses. Nanoindentation test was performed for the analysis of the hardness, modulus and creep properties up to 500 .deg. C. Impression creep method applied to nanoindentation and creep properties of SiC coating layers were characterized by nanoindentation creep test. The fracture strength of SiC coating layers was measured by the micro tensile method at room temperature and 500 .deg. C. From the results, we can conclude that the hardness and fracture strength are decreased with temperature and no significant change in the modulus is observed with increase in temperature. The deformation mechanism for indentation creep and creep rate changes as the testing temperature increased

Tema 8. Principis físics dels semiconductors (Resum)

OpenAIRE

Beléndez Vázquez, Augusto

2011-01-01

Resum del "Tema 8. Principis físics dels semiconductors" de l'assignatura "Fonaments Físics de l'Enginyeria I" de "Grau en Enginyeria en So i Imatge" impartit a l'Escola Politècnica Superior de la Universitat d'Alacant.

Evaluation of surface contamination of bacteria in various dental clinics with special reference to obligate and facultative anaerobic spore bearing bacilli

Directory of Open Access Journals (Sweden)

Kannan I, Jessica Yolanda Jeevitha, Sambandam Cecilia, Jayalakshmi M, Premavathy RK and Shantha S

2014-07-01

Full Text Available Introduction: The occupational health and safety is an important prerequisite in dental clinic setup for well being of both the doctor and patient. Both the patient and dentist are always at the risk of infections. Aim and objectives: There is no proper literature on the survey of bacterial spores, especially of Clostridium species in dental clinics. Hence an attempt has been made in the present pilot study to evaluate the surface contamination with special reference to bacterial spores. Materials and methods: Various dental clinics from Chennai city, India were selected for the present study. Samples were collected from two clinics each from endodontic, prosthodontic, orthodontic, and periodontic. In each clinic important places were selected for sampling. The samples were collected in the form of swabs. The swabs thus obtained were inoculated into Robertson Cooked Meat Medium and was incubated in anaerobic condition at 370C for 7 days. Each day the tubes were examined for turbidity and colour change and were noted. At the end of 7th day the smear was prepared from each tube and gram staining was performed. The gram stained slides were examined microscopically for the presence of spore bearing bacilli especially with special reference to terminal spore bearing bacilli. Results and conclusion: From the present study it is clear that the dental clinics invariably posses a lot of aerobic and anaerobic spores irrespective of stringent disinfection procedures. Hence it is mandatory for the dental clinics to undergo periodical microbiological surveillance and to take proper steps in the control of bacterial spores.

Prevalence of TMJ Disorders among the Patients Attending the Dental Clinic of Ajman University of Science and Technology–Fujairah Campus, UAE

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Kashef K. AlShaban

2018-01-01

Full Text Available The objective of this study was to determine the prevalence of temporomandibular joint (TMJ disorders (if any among the patients attending the dental clinic (for routine dental treatment of Ajman University of Science and Technology (AUST–Fujairah campus, UAE, and its possible causes. A sample of 100 adult patients attending the dental clinic of AUST for different types of dental treatment were collected; the routine examination of the TMJ and possible disorders such as clicking, crepitation, limitation or deviation during mouth opening, or tenderness reveals that 41% of the sample experience varying degrees of disorders in the TMJ. Radiographs were taken if needed (panoramic radiograph. The information was collected and recorded for each patient through questionnaires.

Microbial environmental contamination in Italian dental clinics: A multicenter study yielding recommendations for standardized sampling methods and threshold values.

Science.gov (United States)

Pasquarella, Cesira; Veronesi, Licia; Napoli, Christian; Castiglia, Paolo; Liguori, Giorgio; Rizzetto, Rolando; Torre, Ida; Righi, Elena; Farruggia, Patrizia; Tesauro, Marina; Torregrossa, Maria V; Montagna, Maria T; Colucci, Maria E; Gallè, Francesca; Masia, Maria D; Strohmenger, Laura; Bergomi, Margherita; Tinteri, Carola; Panico, Manuela; Pennino, Francesca; Cannova, Lucia; Tanzi, Marialuisa

2012-03-15

A microbiological environmental investigation was carried out in ten dental clinics in Italy. Microbial contamination of water, air and surfaces was assessed in each clinic during the five working days, for one week per month, for a three-month period. Water and surfaces were sampled before and after clinical activity; air was sampled before, after, and during clinical activity. A wide variation was found in microbial environmental contamination, both within the participating clinics and for the different sampling times. Before clinical activity, microbial water contamination in tap water reached 51,200cfu/mL (colony forming units per milliliter), and that in Dental Unit Water Systems (DUWSs) reached 872,000cfu/mL. After clinical activity, there was a significant decrease in the Total Viable Count (TVC) in tap water and in DUWSs. Pseudomonas aeruginosa was found in 2.38% (7/294) of tap water samples and in 20.06% (59/294) of DUWS samples; Legionella spp. was found in 29.96% (89/297) of tap water samples and 15.82% (47/297) of DUWS samples, with no significant difference between pre- and post-clinical activity. Microbial air contamination was highest during dental treatments, and decreased significantly at the end of the working activity (p<0.05). The microbial buildup on surfaces increased significantly during the working hours. This study provides data for the establishment of standardized sampling methods, and threshold values for contamination monitoring in dentistry. Some very critical situations have been observed which require urgent intervention. Furthermore, the study emphasizes the need for research aimed at defining effective managing strategies for dental clinics. Copyright © 2012 Elsevier B.V. All rights reserved.

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

Wear measurement of dental tissues and materials in clinical studies: A systematic review.

Science.gov (United States)

Wulfman, C; Koenig, V; Mainjot, A K

2018-06-01

This study aims to systematically review the different methods used for wear measurement of dental tissues and materials in clinical studies, their relevance and reliability in terms of accuracy and precision, and the performance of the different steps of the workflow taken independently. An exhaustive search of clinical studies related to wear of dental tissues and materials reporting a quantitative measurement method was conducted. MedLine, Embase, Scopus, Cochrane Library and Web of Science databases were used. Prospective studies, pilot studies and case series (>10 patients), as long as they contained a description of wear measurement methodology. Only studies published after 1995 were considered. After duplicates' removal, 495 studies were identified, and 41 remained for quantitative analysis. Thirty-four described wear-measurement protocols, using digital profilometry and superimposition, whereas 7 used alternative protocols. A specific form was designed to analyze the risk of bias. The methods were described in terms of material analyzed; study design; device used for surface acquisition; matching software details and settings; type of analysis (vertical height-loss measurement vs volume loss measurement); type of area investigated (entire occlusal area or selective areas); and results. There is a need of standardization of clinical wear measurement. Current methods exhibit accuracy, which is not sufficient to monitor wear of restorative materials and tooth tissues. Their performance could be improved, notably limiting the use of replicas, using standardized calibration procedures and positive controls, optimizing the settings of scanners and matching softwares, and taking into account unusable data. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

The relationship between radiological features and clinical manifestation and dental expenses of keratocystic odontogenic tumor

International Nuclear Information System (INIS)

Min, Jung Hyun; Huh, Kyung Heo; Heo, Min Suk; Choi, Soon Chul; Lee, Sam Sun; Bae, Kwang Hak; Choi, Jin Woo

2013-01-01

This study was performed to identify correlations between keratocystic odontogenic tumor (KCOT) data from CT sections, and data on the KCOT clinical manifestation and resulting dental expenses. Following local Institutional Review Board (IRB) approval, a seven-years of retrospective study was performed regarding patients with KCOTs treated at the Seoul National University Dental Hospital. A total of 180 KCOT were included in this study. The following information was collected: age, gender, location and size of the lesion, radiological features, surgical treatment provided and dental expenses. There was no significant association between the size of the KCOT and age, gender, and presenting preoperative symptoms. In both jaws, it was unusual to find KCOTs under 10 mm. The correlation between the number of teeth removed and the size of the KCOT in the tooth bearing area was statistically significant in the mandible, whereas in the maxilla, no significant relationship was found. Dental expenses compared with the size of the KCOT were found to be significant in both jaws. The size of KCOT was associated with a significant increase in dental expenses for both jaws and the number of teeth removed from the mandible. These findings emphasize the importance of routine examinations and early detection of lesions, which in turn helps preserving anatomical structures and reducing dental expenses.

The relationship between radiological features and clinical manifestation and dental expenses of keratocystic odontogenic tumor

Energy Technology Data Exchange (ETDEWEB)

Min, Jung Hyun; Huh, Kyung Heo; Heo, Min Suk; Choi, Soon Chul; Lee, Sam Sun; Bae, Kwang Hak [Dept. of School of Dentistry, Seoul National University, Seoul (Korea, Republic of); Choi, Jin Woo [Dept. of Oral and Maxillofacial Radiology, Dankook University College of Dentistry, Cheonan (Korea, Republic of)

2013-06-15

This study was performed to identify correlations between keratocystic odontogenic tumor (KCOT) data from CT sections, and data on the KCOT clinical manifestation and resulting dental expenses. Following local Institutional Review Board (IRB) approval, a seven-years of retrospective study was performed regarding patients with KCOTs treated at the Seoul National University Dental Hospital. A total of 180 KCOT were included in this study. The following information was collected: age, gender, location and size of the lesion, radiological features, surgical treatment provided and dental expenses. There was no significant association between the size of the KCOT and age, gender, and presenting preoperative symptoms. In both jaws, it was unusual to find KCOTs under 10 mm. The correlation between the number of teeth removed and the size of the KCOT in the tooth bearing area was statistically significant in the mandible, whereas in the maxilla, no significant relationship was found. Dental expenses compared with the size of the KCOT were found to be significant in both jaws. The size of KCOT was associated with a significant increase in dental expenses for both jaws and the number of teeth removed from the mandible. These findings emphasize the importance of routine examinations and early detection of lesions, which in turn helps preserving anatomical structures and reducing dental expenses.

General dental practitioner's views on dental general anaesthesia services.

Science.gov (United States)

Threlfall, A G; King, D; Milsom, K M; Blinkhom, A S; Tickle, M

2007-06-01

Policy has recently changed on provision of dental general anaesthetic services in England. The aim of this study was to investigate general dental practitioners' views about dental general anaesthetics, the reduction in its availability and the impact on care of children with toothache. Qualitative study using semi-structured interviews and clinical case scenarios. General dental practitioners providing NHS services in the North West of England. 93 general dental practitioners were interviewed and 91 answered a clinical case scenario about the care they would provide for a 7-year-old child with multiple decayed teeth presenting with toothache. Scenario responses showed variation; 8% would immediately refer for general anaesthesia, 25% would initially prescribe antibiotics, but the majority would attempt to either restore or extract the tooth causing pain. Interview responses also demonstrated variation in care, however most dentists agree general anaesthesia has a role for nervous children but only refer as a last resort. The responses indicated an increase in inequalities, and that access to services did not match population needs, leaving some children waiting in pain. Most general dental practitioners support moving dental general anaesthesia into hospitals but some believe that it has widened health inequalities and there is also a problem associated with variation in treatment provision. Additional general anaesthetic services in some areas with high levels of tooth decay are needed and evidence based guidelines about caring for children with toothache are required.

First clinical description of Eggerthia catenaformis bacteremia in a patient with dental abscess

DEFF Research Database (Denmark)

Kordjian, Hayarpi H; Schultz, Joyce D J H; Rosenvinge, Flemming Schønning

2015-01-01

We present a case of Eggerthia catenaformis bacteremia originating from a dental abscess and imitating necrotizing fasciitis in a previously healthy adult. The isolates were easily identified by MALDI-TOF MS. The clinical course, surgical and antibiotic treatment as well as the successful outcome...

Dental patients' use of the Internet.

LENUS (Irish Health Repository)

2009-12-19

To determine the use of the Internet by patients attending a range of dental clinics to search for information regarding dental procedures, and also to investigate their interest in online dental consultations and \\'dental tourism\\'.

Anxiety and blood pressure prior to dental treatment.

NARCIS (Netherlands)

Benjamins, C.; Schuurs, A.H.; Asscheman, H.; Hoogstraten, J.

1990-01-01

Assessed dental anxiety and blood pressure immediately prior to a dental appointment in 24 patients attending a university dental clinic or a clinic for anxious dental patients in the Netherlands. Blood pressure was assessed by 2 independent methods, and the interchangeability of the blood-pressure

Additive Manufacturing of SiC Based Ceramics and Ceramic Matrix Composites

Science.gov (United States)

Halbig, Michael Charles; Singh, Mrityunjay

2015-01-01

Silicon carbide (SiC) ceramics and SiC fiber reinforcedSiC ceramic matrix composites (SiCSiC CMCs) offer high payoff as replacements for metals in turbine engine applications due to their lighter weight, higher temperature capability, and lower cooling requirements. Additive manufacturing approaches can offer game changing technologies for the quick and low cost fabrication of parts with much greater design freedom and geometric complexity. Four approaches for developing these materials are presented. The first two utilize low cost 3D printers. The first uses pre-ceramic pastes developed as feed materials which are converted to SiC after firing. The second uses wood containing filament to print a carbonaceous preform which is infiltrated with a pre-ceramic polymer and converted to SiC. The other two approaches pursue the AM of CMCs. The first is binder jet SiC powder processing in collaboration with rp+m (Rapid Prototyping+Manufacturing). Processing optimization was pursued through SiC powder blending, infiltration with and without SiC nano powder loading, and integration of nanofibers into the powder bed. The second approach was laminated object manufacturing (LOM) in which fiber prepregs and laminates are cut to shape by a laser and stacked to form the desired part. Scanning electron microscopy was conducted on materials from all approaches with select approaches also characterized with XRD, TGA, and bend testing.

Knowledge of risk factors and the periodontal disease-systemic link in dental students' clinical decisions.

Science.gov (United States)

Friesen, Lynn Roosa; Walker, Mary P; Kisling, Rebecca E; Liu, Ying; Williams, Karen B

2014-09-01

This study evaluated second-, third-, and fourth-year dental students' ability to identify systemic conditions associated with periodontal disease, risk factors most important for referral, and medications with an effect on the periodontium and their ability to apply this knowledge to make clinical decisions regarding treatment and referral of periodontal patients. A twenty-one question survey was administered at one U.S. dental school in the spring semester of 2012 to elicit the students' knowledge and confidence regarding clinical reasoning. The response rate was 86 percent. Periodontal risk factors were accurately selected by at least 50 percent of students in all three classes; these were poorly controlled diabetes, ≥6 mm pockets posteriorly, and lack of response to previous non-surgical therapy. Confidence in knowledge, knowledge of risk factors, and knowledge of medications with an effect on the periodontium improved with training and were predictive of better referral decision making. The greatest impact of training was seen on the students' ability to make correct decisions about referral and treatment for seven clinical scenarios. Although the study found a large increase in the students' abilities from the second through fourth years, the mean of 4.6 (out of 7) for the fourth-year students shows that, on average, those students missed correct treatment or referral on more than two of seven clinical cases. These results suggest that dental curricula should emphasize more critical decision making with respect to referral and treatment criteria in managing the periodontal patient.

Awareness of Infection Control Protocols Among Dental Students in Babylon Dental Faculty

Directory of Open Access Journals (Sweden)

Khalil Ibraheem Zaidan

2018-02-01

Full Text Available Infection control and knowledge of common "infectious diseases" is essential for safe dental practice. Conveyance of infectious diseases is likely "from one individual to another during dental procedures", thorough" blood-borne" viruses and bacteria   "such as hepatitis" , human immunodeficiency virus (HIV. Thence in dental practice, the  sterilization and particular protection  is of most importance Process in  dental procedures,  and patient sponsor settings seek specific strategies guide to prevent the  transmission of diseases among dental students , oral verdure care staffs and their patients. Aim: Current study highlight  the methods and behavior  to evaluate  the  benefits of awareness, stance and pursuit of infection control between dental students in training dental clinic at Babylon  dental collage . Materials and Methods: A cross-sectional wipe using a rear ordered questionnaire was executed. The reconnaissance consisted of 38 closed-ended questions that included the key areas of infection control, including hand hygiene, personal preservation, sterilization and disinfection and ecological infection monitoring. There were also questions to elicit perceptions regarding the treatment of HBV and HIV/AIDS patients. Results: Survey study was done for dental students replied to the reconnaissance. Their situation and realization across infection control in college teaching  clinic .The results were assorted between 100% were orderly using gloves and 96% mask   with patient to 6% were orderly wore eye glasses. The type of sterilization of instrument was 90% autoclave and 10% oven and from analysis of data revealed most teaching clinics devoid of instruction post about control of infection control measures   Conclusion: "Improved compliance with recommended infection control procedures is required for all dentists" and graduated dental students  predestined in the existing project. Enduring instruction "programs and short

Assessing the Clinical Skills of Dental Students: A Review of the Literature

Science.gov (United States)

Taylor, Carly L.; Grey, Nick; Satterthwaite, Julian D.

2013-01-01

Education, from a student perspective, is largely driven by assessment. An effective assessment tool should be both valid and reliable, yet this is often not achieved. The aim of this literature review is to identify and appraise the evidence base for assessment tools used primarily in evaluating clinical skills of dental students. Methods:…

Clinical and radiological investigations of mandibular overdentures supported by conventional or mini-dental implants: A 2-year prospective follow-up study.

Science.gov (United States)

Temizel, Sonay; Heinemann, Friedhelm; Dirk, Cornelius; Bourauel, Christoph; Hasan, Istabrak

2017-02-01

Conventional dental implants are not applicable in the mandibular interforaminal region if bone volume is limited. Mini-dental implants offer an alternative means of supporting mandibular overdentures in a narrow residual ridge, without additional surgery. The purpose of this nonrandomized clinical trial was to compare the ability of mini-dental implants with that of conventional dental implants in supporting mandibular overdentures during a 2-year clinical follow-up. Bone quality, bone resorption, implant stability, and oral health were assessed radiographically. A total of 32 participants with edentulism were included. Twenty-two participants (99 implants) received 4 to 5 mini-dental implants (diameter: 1.8-2.4 mm; length: 13-15 mm, study group), and 10 participants (35 implants) received 2 to 4 conventional dental implants (diameter: 3.3-3.7 mm; length: 11-13 mm, control group). The selection of the participants in the study or control group was based on the available bone volume in the mandible. The selection was not randomized. The density of cortical bone thickness was measured in Hounsfield units (HU) from computed tomography data, and patients were followed for 2 years. The participants were examined 3, 6, 12, and 24 months after surgery. Primary stability immediately after the insertion of dental implants (Periotest), secondary stability 6 months after implantation, modified plaque, bleeding on probing indices, and probing depth were measured and analyzed statistically (α=.05). The mean HU value 6 months after implantation in the participants who received mini-dental implants was significantly (P=.035) higher (1250 HU) than that in the participants who received conventional dental implants (1100 HU). The probing depths around the conventional dental implants (1.6 and 1.8 mm, respectively) were significantly higher than those around the mini-dental implants (1.3 and 1.2 mm, respectively) 12 and 24 months after surgery, respectively (Pdental implants were

Use of information and communication technology among dental students and registrars at the faculty of dental sciences, University of Lagos.

Science.gov (United States)

Butali, A; Adeyemo, W L; Akinshipo, A O; Fashina, A; Savage, K O

2011-01-01

The aim of this study was to investigate the use of information technology amongst dental students, dental nursing students and resident doctors in training at the faculty of dental Surgery University of Lagos. A structured questionnaire was distributed to 58 clinical dental students in 4 th and 5 th years of training in the 2010/2011 academic year, 36 dental nursing students and 63 resident doctors undergoing specialist training. All participants have access to the computers, 2.5% within the University and 31% at home and internet cafes and about 50% have the basic skills required. A significant difference was observed between the resident doctors and clinical dental students (P = 0.003), between resident doctors and dental nursing students (P = 0.0001) when the use of computer for study was compared. Over 95% of participants have access to internet and about 50% of them use the internet for their studies. A significant difference (P = 0.005) was observed between clinical dental students and dental nursing students that use the internet and word processing. The resident doctors used the computers for multimedia and MedLine search tools more than clinical dental students (P = 0.004) and dental nursing students (0.0006). The findings of the study show that dental students and resident doctors in training have the requisite knowledge to operate the computer for use in their study and personal activities.

Psychosocial student functioning in comprehensive dental clinic education: A qualitative study.

Science.gov (United States)

Moore, R

2018-02-17

The aims were to describe first-year clinical dental students' psychosocial experiences in a known well-functioning comprehensive clinic teaching group (F+Grp) and a known dysfunctional group (Dys-Grp) and, thus, discover and describe phenomena related to psychosocial functioning of students. These groups were compared and contrasted regarding negative stress symptoms, perfectionism and coping with stress. Eight female dental students (mean 26 years old), four in each group, were interviewed after the first clinical year about learning and emotional experiences. The students also rated their perceived stress using a 0-10 scale, where 0 is no stress, and 10 is highest stress. Qualitative analyses involved searching for recurring themes and discovery of categories of clinical and social functioning. All 8 students were revisited as dentists after 8 years and filled out a 15-item survey as longitudinal validation of their first-year clinical experiences and to estimate group consensus and informant accuracy. Both groups suffered from negative stress symptoms attributed to lack of time for clinical tasks, worries about work quality with confusion about their own expectations and worries about how others perceived them. Dys-Grp experienced higher negative stress and maladaptive perfectionism and described crying behaviours, withdrawal and unwillingness to cooperate with others. In contrast, students in F+Grp provided rich content about mutual cooperation related to social networking and positive support. The 8 subjects exhibited high internal consistency (α  =  .98) in their responses to the follow-up survey about their first year of clinic. The comprehensive care teaching clinic environment with students working in groups appeared to provide a possibility for students to support each other for improved stress coping. Unfortunately, the opposite also occurred. Positive, supportive teacher supervision of student challenges related to perfectionism and stress is

Low dose irradiation performance of SiC interphase SiC/SiC composites

International Nuclear Information System (INIS)

Snead, L.L.; Lowden, R.A.; Strizak, J.; More, K.L.; Eatherly, W.S.; Bailey, J.; Williams, A.M.; Osborne, M.C.; Shinavski, R.J.

1998-01-01

Reduced oxygen Hi-Nicalon fiber reinforced composite SiC materials were densified with a chemically vapor infiltrated (CVI) silicon carbide (SiC) matrix and interphases of either 'porous' SiC or multilayer SiC and irradiated to a neutron fluence of 1.1 x 10 25 n m -2 (E>0.1 MeV) in the temperature range of 260 to 1060 C. The unirradiated properties of these composites are superior to previously studied ceramic grade Nicalon fiber reinforced/carbon interphase materials. Negligible reduction in the macroscopic matrix microcracking stress was observed after irradiation for the multilayer SiC interphase material and a slight reduction in matrix microcracking stress was observed for the composite with porous SiC interphase. The reduction in strength for the porous SiC interfacial material is greatest for the highest irradiation temperature. The ultimate fracture stress (in four point bending) following irradiation for the multilayer SiC and porous SiC interphase materials was reduced by 15% and 30%, respectively, which is an improvement over the 40% reduction suffered by irradiated ceramic grade Nicalon fiber materials fabricated in a similar fashion, though with a carbon interphase. The degradation of the mechanical properties of these composites is analyzed by comparison with the irradiation behavior of bare Hi-Nicalon fiber and Morton chemically vapor deposited (CVD) SiC. It is concluded that the degradation of these composites, as with the previous generation ceramic grade Nicalon fiber materials, is dominated by interfacial effects, though the overall degradation of fiber and hence composite is reduced for the newer low-oxygen fiber. (orig.)

An Extension of SIC Predictions to the Wiener Coactive Model.

Science.gov (United States)

Houpt, Joseph W; Townsend, James T

2011-06-01

The survivor interaction contrasts (SIC) is a powerful measure for distinguishing among candidate models of human information processing. One class of models to which SIC analysis can apply are the coactive, or channel summation, models of human information processing. In general, parametric forms of coactive models assume that responses are made based on the first passage time across a fixed threshold of a sum of stochastic processes. Previous work has shown that that the SIC for a coactive model based on the sum of Poisson processes has a distinctive down-up-down form, with an early negative region that is smaller than the later positive region. In this note, we demonstrate that a coactive process based on the sum of two Wiener processes has the same SIC form.

[Oral and dental health and oral and dental support of home patients--role of dental hygienist in the home service nursing station].

Science.gov (United States)

Hayashi, T; Kimura, M; Tamura, N; Hirata, S; Yabunaka, T; Kamimura, Y

1999-12-01

Home patients have few chances for going out, so communication with their family means a lot. Talking and eating are particular pleasures. Therefore, oral and dental health and oral and dental support are very important for home patients. A dental hygienist from our clinic visits and offers oral and dental health (oral care) and oral and dental support (oral rehabilitation) to home patients as part of a care plan with home care nurses. Moreover, as general conditions are closely related with oral function, maintaining oral and dental health and regular oral and dental support are very important in order to improve the quality of life (QOL) of home patients.

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.

Synthesis of micro-sized interconnected Si-C composites

Science.gov (United States)

Wang, Donghai; Yi, Ran; Dai, Fang

2016-02-23

Embodiments provide a method of producing micro-sized Si--C composites or doped Si--C and Si alloy-C with interconnected nanoscle Si and C building blocks through converting commercially available SiO.sub.x (0

An evaluation of clinical, radiological and three-dimensional dental tomography findings in ectodermal dysplasia cases.

Science.gov (United States)

Doğan, Mehmet-Sinan; Callea, Michele; Yavuz, Ìzzet; Aksoy, Orhan; Clarich, Gabriella; Günay, Ayse; Günay, Ahmet; Güven, Sedat; Maglione, Michele; Akkuş, Zeki

2015-05-01

This study aimed to review the results related to head and jaw disorders in cases of ectodermal dysplasia. The evaluation of ectodermal dysplasia cases was made by clinical examination and examination of the jaw and facial areas radiologically and on cone-beam 3-dimensional dental tomography (CBCT) images. In the 36 cases evaluated in the study, typical clinical findings of pure hypohidrotic ectodermal displasia (HED) were seen, such as missing teeth, dry skin, hair and nail disorders. CBCT images were obtained from 12 of the 36 cases, aged 1.5- 45 years, and orthodontic analyses were made on these images. The clinical and radiological evaluations determined, hypodontia or oligodontia, breathing problems, sweating problems, a history of fever, sparse hair, saddle nose, skin peeling, hypopigmentation, hyperpigmentation, finger and nail deformities, conical teeth anomalies, abnormal tooth root formation, tooth resorption in the root, gingivitis, history of epilepsy, absent lachrymal canals and vision problems in the cases which included to the study. Ectodermal dysplasia cases have a particular place in dentistry and require a professional, multi-disciplinary approach in respect of the chewing function, orthognathic problems, growth, oral and dental health. It has been understood that with data obtained from modern technologies such as three-dimensional dental tomography and the treatments applied, the quality of life of these cases can be improved.

The effect of SiC particle size on the properties of Cu–SiC composites

International Nuclear Information System (INIS)

Celebi Efe, G.; Zeytin, S.; Bindal, C.

2012-01-01

Graphical abstract: The relative densities of Cu–SiC composites sintered at 700 °C for 2 h are ranged from 97.3% to 91.8% for SiC with 1 μm particle size and 97.5% to 95.2% for SiC with 5 μm particle size, microhardness of composites ranged from 143 to 167 HV for SiC having 1 μm particle size and 156–182 HVN for SiC having 5 μm particle size and the electrical conductivity of composites changed between 85.9% IACS and 55.7% IACS for SiC with 1 μm particle size, 87.9% IACS and 65.2%IACS for SiC with 5 μm particle size. It was found that electrical conductivity of composites containing SiC with 5 μm particle size is better than that of Cu–SiC composites containing SiC with particle size of 1 μm. Highlights: ► In this research, the effect of SiC particle size on some properties of Cu–SiC composites were investigated. ► The mechanical properties were improved. ► The electrical properties were obtained at desirable level. -- Abstract: SiC particulate-reinforced copper composites were prepared by powder metallurgy (PM) method and conventional atmospheric sintering. Scanning electron microscope (SEM), X-ray diffraction (XRD) techniques were used to characterize the sintered composites. The effect of SiC content and particle size on the relative density, hardness and electrical conductivity of composites were investigated. The relative densities of Cu–SiC composites sintered at 700 °C for 2 h are ranged from 97.3% to 91.8% for SiC with 1 μm particle size and from 97.5% to 95.2% for SiC with 5 μm particle size. Microhardness of composites ranged from 143 to 167 HV for SiC having 1 μm particle size and from 156 to 182 HV for SiC having 5 μm particle size. The electrical conductivity of composites changed between 85.9% IACS and 55.7% IACS for SiC with 1 μm particle size, between 87.9% IACS and 65.2% IACS for SiC with 5 μm particle size.

Patient satisfaction in Dental Healthcare Centers.

Science.gov (United States)

Ali, Dena A

2016-01-01

This study aimed to (1) measure the degree of patient satisfaction among the clinical and nonclinical dental services offered at specialty dental centers and (2) investigate the factors associated with the degree of overall satisfaction. Four hundred and ninety-seven participants from five dental centers were recruited for this study. Each participant completed a self-administered questionnaire to measure patient satisfaction with clinical and nonclinical dental services. Analysis of variance, t-tests, a general linear model, and stepwise regression analysis was applied. The respondents were generally satisfied, but internal differences were observed. The exhibited highest satisfaction with the dentists' performance, followed by the dental assistants' services, and the lowest satisfaction with the center's physical appearance and accessibility. Females, participants with less than a bachelor's degree, and younger individuals were more satisfied with the clinical and nonclinical dental services. The stepwise regression analysis revealed that the coefficient of determination (R (2)) was 40.4%. The patient satisfaction with the performance of the dentists explained 42.6% of the overall satisfaction, whereas their satisfaction with the clinical setting explained 31.5% of the overall satisfaction. Additional improvements with regard to the accessibility and physical appearance of the dental centers are needed. In addition, interventions regarding accessibility, particularly when booking an appointment, are required.

Impact of untreated dental caries and its clinical consequences on the oral health-related quality of life of schoolchildren aged 8-10 years.

Science.gov (United States)

Mota-Veloso, Isabella; Soares, Maria Eliza C; Alencar, Bruna Mota; Marques, Leandro Silva; Ramos-Jorge, Maria Letícia; Ramos-Jorge, Joana

2016-01-01

This study aims to evaluate the impact of untreated dental caries and its clinical consequences on the quality of life of Brazilian schoolchildren aged 8-10 years. A randomly selected sample of 587 children underwent a clinical oral examination for the assessment of untreated dental caries and clinical consequences. The WHO criteria (decayed component of the decayed, missing, and filled teeth--D-DMFT in permanent teeth or d-dfmt in primary teeth) and the PUFA index, which records the presence of severely decayed permanent (upper case) and primary (lower case) teeth with visible pulpal involvement (P/p), as well as ulceration caused by dislocated tooth fragments (U/u), fistula (F/f), and abscesses (A/a), were used for the oral examination. Oral health-related quality of life (OHRQoL) was evaluated using the Child's Perception Questionnaire (CPQ8-10). Poisson regression was employed to test unadjusted and adjusted associations between untreated dental caries/clinical consequences and OHRQoL. The prevalence of untreated dental caries was 64.6% (D/d component of DMFT/dmft > 0) and 17.9% of children exhibited clinical consequences of caries (PUFA/pufa index >0). In the adjusted models, untreated caries was significantly associated with the total CPQ8-10 score and all subscale scores. The clinical consequences of dental caries (PUFA/pufa index >0) were significantly associated with the total CPQ8-10 as well as the oral symptoms and functional limitations' subscales. Untreated dental caries and its clinical consequences exerted a negative impact on the OHRQoL of the schoolchildren analyzed.

Fractographic features of glass-ceramic and zirconia-based dental restorations fractured during clinical function.

Science.gov (United States)

Oilo, Marit; Hardang, Anne D; Ulsund, Amanda H; Gjerdet, Nils R

2014-06-01

Fractures during clinical function have been reported as the major concern associated with all-ceramic dental restorations. The aim of this study was to analyze the fracture features of glass-ceramic and zirconia-based restorations fractured during clinical use. Twenty-seven crowns and onlays were supplied by dentists and dental technicians with information about type of cement and time in function, if available. Fourteen lithium disilicate glass-ceramic restorations and 13 zirconia-based restorations were retrieved and analyzed. Fractographic features were examined using optical microscopy to determine crack initiation and crack propagation of the restorations. The material comprised fractured restorations from one canine, 10 incisors, four premolars, and 11 molars. One crown was not categorized because of difficulty in orientation of the fragments. The results revealed that all core and veneer fractures initiated in the cervical margin and usually from the approximal area close to the most coronally placed curvature of the margin. Three cases of occlusal chipping were found. The margin of dental all-ceramic single-tooth restorations was the area of fracture origin. The fracture features were similar for zirconia, glass-ceramic, and alumina single-tooth restorations. Design features seem to be of great importance for fracture initiation. © 2014 Eur J Oral Sci.

InP-based photonic integrated circuit platform on SiC wafer.

Science.gov (United States)

Takenaka, Mitsuru; Takagi, Shinichi

2017-11-27

We have numerically investigated the properties of an InP-on-SiC wafer as a photonic integrated circuit (PIC) platform. By bonding a thin InP-based semiconductor on a SiC wafer, SiC can be used as waveguide cladding, a heat sink, and a support substrate simultaneously. Since the refractive index of SiC is sufficiently low, PICs can be fabricated using InP-based strip and rib waveguides with a minimum bend radius of approximately 7 μm. High-thermal-conductivity SiC underneath an InP-based waveguide core markedly improves heat dissipation, resulting in superior thermal properties of active devices such as laser diodes. The InP-on-SiC wafer has significantly smaller thermal stress than InP-on-SiO 2 /Si wafer, which prevents the thermal degradation of InP-based devices during high-temperature processes. Thus, InP on SiC provides an ideal platform for high-performance PICs.

Factors affecting the corrosion of SiC layer by fission product palladium

International Nuclear Information System (INIS)

Dewita, E.

2000-01-01

HTR is one of the advanced nuclear reactors which has inherent safety system, graphite moderated and helium gas cooled. In general, these reactors are designed with the TRISO coated particle consist of four coating layers that are porous pyrolytic carbon (PyC). inner dense PyC (IPyC), silicon carbide (SiC), and outer dense PyC (OPyC). Among the four coating layers, the SiC plays an important role beside in retaining metallic fission products, it also provides mechanical strength to fuel particle. However, results of post irradiation examination indicate that fission product palladium can react with and corrode SiC layer, This assessment is conducted to get the comprehension about resistance of SiC layer on irradiation effects, especially in order to increase the fuel bum-up. The result of this shows that the corrosion of SiC layer by fission product palladium is beside depend on the material characteristics of SiC, and also there are other factors that affect on the SiC layer corrosion. Fuel enrichment, bum-up, and irradiation time effect on the palladium flux in fuel kernel. While, the fuel density, vapour pressure of palladium (the degree depend on the irradiation temperature and kernel composition) effect on palladium migration in fuel particle. (author)

SiC fibre by chemical vapour deposition on tungsten filament

Indian Academy of Sciences (India)

Unknown

SiC fibre by chemical vapour deposition on tungsten filament ... CMCs), in defence and industrial applications. SiC has attractive ... porosity along with chemical purity. This is lacking .... reactor. Since mercury is very toxic it should be removed.

The annealing effects on irradiated SiC piezo resistive pressure sensor

International Nuclear Information System (INIS)

Almaz, E.; Blue, T. E.; Zhang, P.

2009-01-01

The effects of temperature on annealing of Silicon Carbide (SiC) piezo resistive pressure sensor which was broken after high fluence neutron irradiation, were investigated. Previously, SiC piezo resistive sensor irradiated with gamma ray and fast neutron in the Co-60 gamma-ray irradiator and Beam Port 1 (BP1) and Auxiliary Irradiation Facility (AIF) at the Ohio State University Nuclear Reactor Laboratory (OSUNRL) respectively. The Annealing temperatures were tested up to 400 C. The Pressure-Output voltage results showed recovery after annealing process on SiC piezo resistive pressure sensor. The bridge resistances of the SiC pressure sensor stayed at the same level up to 300 C. After 400 C annealing, the resistance values changed dramatically.

Recent progress of ultrahigh voltage SiC devices for particle accelerator

International Nuclear Information System (INIS)

Fukuda, Kenji; Tsuji, Takashi; Shiomi, Hiromu; Mizushima, Tomonori; Yonezawa, Yoshiyuki; Kondo, Chikara; Otake, Yuji

2016-01-01

Silicon carbide (SiC) is the promising material for next power electronics technology used in the field such as HEV, EV, and railway, electric power infrastructure. SiC enables power devices with low loss to easily operate in an ultrahigh-voltage region because of the high breakdown electric field of SiC. In this paper, we report static and dynamic electric performances of 3300 V class SiC SBDs, IE-MOSFETs, >10 kV PiN diodes and IE-IGBTs. Especially, the electrical characteristics of IE-IGBT with the blocking voltage of 16.5 kV indicate the sufficient ability to convert the thyratron in high power RF system of an accelerator. (author)

Elaboration of silicon carbides nano particles (SiC): from the powder synthesis to the sintered ceramic

International Nuclear Information System (INIS)

Reau, A.

2008-01-01

Materials for the reactor cores of the fourth generation will need materials supporting high temperatures with fast neutrons flux. SiC f /SiC ceramics are proposed. One of the possible elaboration process is to fill SiC fiber piece with nano particles SiC powder and to strengthen by sintering. The aim of this thesis is to obtain a nano structured SiC ceramic as a reference for the SiC f /SiC composite development and to study the influence of the fabrication parameters. (A.L.B.)

Detection and analysis of particles with failed SiC in AGR-1 fuel compacts

Energy Technology Data Exchange (ETDEWEB)

Hunn, John D., E-mail: hunnjd@ornl.gov [Oak Ridge National Laboratory (ORNL), P.O. Box 2008, Oak Ridge, TN 37831-6093 (United States); Baldwin, Charles A.; Gerczak, Tyler J.; Montgomery, Fred C.; Morris, Robert N.; Silva, Chinthaka M. [Oak Ridge National Laboratory (ORNL), P.O. Box 2008, Oak Ridge, TN 37831-6093 (United States); Demkowicz, Paul A.; Harp, Jason M.; Ploger, Scott A. [Idaho National Laboratory (INL), P.O. Box 1625, Idaho Falls, ID 83415-6188 (United States)

2016-09-15

Highlights: • Cesium release was used to detect SiC failure in HTGR fuel. • Tristructural-isotropic particles with SiC failure were isolated by gamma screening. • SiC failure was studied by X-ray tomography and SEM. • SiC degradation was observed after irradiation and subsequent safety testing. - Abstract: As the primary barrier to release of radioactive isotopes emitted from the fuel kernel, retention performance of the SiC layer in tristructural isotropic (TRISO) coated particles is critical to the overall safety of reactors that utilize this fuel design. Most isotopes are well-retained by intact SiC coatings, so pathways through this layer due to cracking, structural defects, or chemical attack can significantly contribute to radioisotope release. In the US TRISO fuel development effort, release of {sup 134}Cs and {sup 137}Cs are used to detect SiC failure during fuel compact irradiation and safety testing because the amount of cesium released by a compact containing one particle with failed SiC is typically ten or more times higher than that released by compacts without failed SiC. Compacts with particles that released cesium during irradiation testing or post-irradiation safety testing at 1600–1800 °C were identified, and individual particles with abnormally low cesium retention were sorted out with the Oak Ridge National Laboratory (ORNL) Irradiated Microsphere Gamma Analyzer (IMGA). X-ray tomography was used for three-dimensional imaging of the internal coating structure to locate low-density pathways through the SiC layer and guide subsequent materialography by optical and scanning electron microscopy. All three cesium-releasing particles recovered from as-irradiated compacts showed a region where the inner pyrocarbon (IPyC) had cracked due to radiation-induced dimensional changes in the shrinking buffer and the exposed SiC had experienced concentrated attack by palladium; SiC failures observed in particles subjected to safety testing were

Improving a Dental School's Clinic Operations Using Lean Process Improvement.

Science.gov (United States)

Robinson, Fonda G; Cunningham, Larry L; Turner, Sharon P; Lindroth, John; Ray, Deborah; Khan, Talib; Yates, Audrey

2016-10-01

The term "lean production," also known as "Lean," describes a process of operations management pioneered at the Toyota Motor Company that contributed significantly to the success of the company. Although developed by Toyota, the Lean process has been implemented at many other organizations, including those in health care, and should be considered by dental schools in evaluating their clinical operations. Lean combines engineering principles with operations management and improvement tools to optimize business and operating processes. One of the core concepts is relentless elimination of waste (non-value-added components of a process). Another key concept is utilization of individuals closest to the actual work to analyze and improve the process. When the medical center of the University of Kentucky adopted the Lean process for improving clinical operations, members of the College of Dentistry trained in the process applied the techniques to improve inefficient operations at the Walk-In Dental Clinic. The purpose of this project was to reduce patients' average in-the-door-to-out-the-door time from over four hours to three hours within 90 days. Achievement of this goal was realized by streamlining patient flow and strategically relocating key phases of the process. This initiative resulted in patient benefits such as shortening average in-the-door-to-out-the-door time by over an hour, improving satisfaction by 21%, and reducing negative comments by 24%, as well as providing opportunity to implement the electronic health record, improving teamwork, and enhancing educational experiences for students. These benefits were achieved while maintaining high-quality patient care with zero adverse outcomes during and two years following the process improvement project.

Reflective learning in community-based dental education.

Science.gov (United States)

Deogade, Suryakant C; Naitam, Dinesh

2016-01-01

Community-based dental education (CBDE) is the implementation of dental education in a specific social context, which shifts a substantial part of dental clinical education from dental teaching institutional clinics to mainly public health settings. Dental students gain additional value from CBDE when they are guided through a reflective process of learning. We propose some key elements to the existing CBDE program that support meaningful personal learning experiences. Dental rotations of 'externships' in community-based clinical settings (CBCS) are year-long community-based placements and have proven to be strong learning environments where students develop good communication skills and better clinical reasoning and management skills. We look at the characteristics of CBDE and how the social and personal context provided in communities enhances dental education. Meaningfulness is created by the authentic context, which develops over a period of time. Structured reflection assignments and methods are suggested as key elements in the existing CBDE program. Strategies to enrich community-based learning experiences for dental students include: Photographic documentation; written narratives; critical incident reports; and mentored post-experiential small group discussions. A directed process of reflection is suggested as a way to increase the impact of the community learning experiences. We suggest key elements to the existing CBDE module so that the context-rich environment of CBDE allows for meaningful relations and experiences for dental students and enhanced learning.

Identifying barriers to receiving preventive dental services: expanding access to preventive dental hygiene services through affiliated practice.

Science.gov (United States)

Gross-Panico, Michelle L; Freeman, Wilbur K

2012-01-01

Minority children and children from lower income families are more likely to experience the burden of oral disease. Since oral disease reduces quality of life, it is a priority to utilize preventive dental services. The research questions ask if affiliated practice increases utilization of preventive dental services by underserved children from birth to 18 years of age, and what the barriers to receiving preventive dental services are and their level of importance. A survey was administered to parents/guardians of patients from birth to 18 years of age who received preventive dental services from Catholic Healthcare West East Valley Children's Dental Clinic, an affiliated practice dental clinic in Chandler, Arizona. Thirty-four surveys were completed: 21 completed in English and 13 completed in Spanish. The data was analyzed to provide descriptive statistics and non-parametrically analyzed using the Friedman's, Kendall's W and Wilcoxon Signed Ranks Tests. The cost of preventive dental services is more important to this population than both convenience of appointment time and distance traveled. As the cost increases for preventive dental services, this population will utilize preventive dental services less frequently. The study indicated that the increase of self-reported utilization of preventive dental services by underserved children, ranging in age from birth to 18 years old, in Arizona affiliated practice dental clinics, was primarily impacted by perceived reduced costs of receiving care. Funding efforts, reimbursement mechanisms and legislative policies should support this dental care delivery model to provide care to underserved children, adults and seniors throughout the U.S.

[Experience, prevalence, severity, treatment needs for dental caries and care index in Mexican adolescents and young adults].

Science.gov (United States)

García-Cortés, José Obed; Mejia-Cruz, Jorge Adrián; Medina-Cerda, Eduardo; Orozco-De la Torre, Guillermo; Medina-Solís, Carlo Carlo; Márquez-Rodríguez, Sonia; Navarrete-Hernández, José de Jesús; Islas-Granillo, Horacio

2014-01-01

To determine the experience, prevalence and severity of dental caries as well as to establish the treatment needs and restorative care in adolescents and young adults. This cross-sectional study included 638 subjects 16-25 years old candidates to enter to state public university of San Luis Potosí, México. For caries detection was used the DMFT index (sum of decayed teeth + missing teeth + filled teeth in the permanent dentition). With DMFT index data were calculated the experience, the prevalence and the severity of caries. Also are reported the significant caries index (SiC), the treatment needs index (TNI) and the care index (CI). Statistical analysis was performed using nonparametric tests. The mean DMFT index was 4.24 ± 3.85, prevalence 76.5% and severity of 52.3% for DMFT > 3 and 26.2% for DMFT > 6. The SiC index was 8.7. The TNI was 43.0% and 52.8% CI. No variation was observed (p > 0.05) on the experience, prevalence and severity of caries by age. The component "filled teeth" showed differences by age (p caries experience and severity than men (p dental caries in this sample of adolescents and young adults. We found almost 40% of untreated caries lesions. We found some differences by sex.

Predictors of Academic Success for the National Board Dental Hygiene Examination and the Southern Regional Testing Agency Clinical Exam

Science.gov (United States)

Efurd, Melissa G.

2012-01-01

The purpose for conducting this study was to investigate and describe the relationship between applicant criteria for a dental hygiene program and subsequent outcomes on credentialing exams: the National Board Dental Hygiene Exam and the Southern Regional Testing Agency clinical exam. Because admission criteria play a crucial role in applicant…

Transformation from amorphous to nano-crystalline SiC thin films ...

Indian Academy of Sciences (India)

Administrator

phous SiC to cubic nano-crystalline SiC films with the increase in the gas flow ratio. Raman scattering ... Auger electron spectroscopy showed that the carbon incorporation in the .... with a 514 nm Ar+ laser excitation source and the laser.

TiC/Ti3SiC2复合材料的制备及其性能研究%Preparation and properties of TiC/Ti3SiC2 composites

Institute of Scientific and Technical Information of China (English)

贾换; 尹洪峰; 袁蝴蝶; 杨祎诺

2012-01-01

以粉末Ti,Si,TiC和炭黑为原料,采用反应热压烧结法制备TiC/Ti3SiC2复合材料.借助XRD和SEM研究TiC含量对TiC/Ti3SiC2复合材料相组成、显微结构及力学特性的影响.结果表明:通过热压烧结可以得到致密度较高的TiC/Ti3SiC2复合材料；引入TiC可以促进Ti3SiC2的生成,当引入TiC的质量分数达30％,TiC/Ti3SiC2复合材料的弯曲强度和断裂韧性分别为406.9 MPa,3.7 MPa·m1/2；复合材料中Ti3SiC2相以穿晶断裂为主,TiC晶粒易产生拔出.%TiC/Ti3SiC2 composites were fabricated by reactive hot pressing sintering method using the mixture powder of Ti, Si, C and TiC as raw material. The effect of TiC content on phase composition, microstructure and mechanical properties of TiC/Ti3SiC2 composites was investigated by X-ray diffraction and scanning electron microscopy. The results demonstrate that dense TiC/ Ti3SiC2 composites can be obtained by hot pressing. The addition of TiC into composites can enhance the formation of TisSiC2. When the additional content of TiC reaches 30% (mass fraction) , the flexural strength and fracture toughness of TiC/Ti3SiC2 composite are 406.9 MPa and 3.7 MPa·m-2, respectively. Ti3SiC2 phase displays intergranular fracture and TiC grain pulls out from Ti3SiC2 matrix when TiC/Ti3SiC2 composite fractures.

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

Clinical evidence on titanium-zirconium dental implants: a systematic review and meta-analysis.

Science.gov (United States)

Altuna, P; Lucas-Taulé, E; Gargallo-Albiol, J; Figueras-Álvarez, O; Hernández-Alfaro, F; Nart, J

2016-07-01

The use of titanium implants is well documented and they have high survival and success rates. However, when used as reduced-diameter implants, the risk of fracture is increased. Narrow diameter implants (NDIs) of titanium-zirconium (Ti-Zr) alloy have recently been developed (Roxolid; Institut Straumann AG). Ti-Zr alloys (two highly biocompatible materials) demonstrate higher tensile strength than commercially pure titanium. The aim of this systematic review was to summarize the existing clinical evidence on dental NDIs made from Ti-Zr. A systematic literature search was performed using the Medline database to find relevant articles on clinical studies published in the English language up to December 2014. Nine clinical studies using Ti-Zr implants were identified. Overall, 607 patients received 922 implants. The mean marginal bone loss was 0.36±0.06mm after 1 year and 0.41±0.09mm after 2 years. The follow-up period ranged from 3 to 36 months. Mean survival and success rates were 98.4% and 97.8% at 1 year after implant placement and 97.7% and 97.3% at 2 years. Narrow diameter Ti-Zr dental implants show survival and success rates comparable to regular diameter titanium implants (>95%) in the short term. Long-term follow-up clinical data are needed to confirm the excellent clinical performance of these implants. Copyright © 2016 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Advantages of the Dental Practice-Based Research Network Initiative and Its Role in Dental Education

Science.gov (United States)

Curro, Frederick A.; Grill, Ashley C.; Thompson, Van P.; Craig, Ronald G.; Vena, Don; Keenan, Analia V.; Naftolin, Frederick

2012-01-01

Practice-based research networks (PBRNs) provide a novel venue in which providers can increase their knowledge base and improve delivery of care through participation in clinical studies. This article describes some aspects of our experience with a National Institute of Dental and Craniofacial Research-supported PBRN and discusses the role it can play in dental education. PBRNs create a structured pathway for providers to advance their professional development by participating in the process of collecting data through clinical research. This process allows practitioners to contribute to the goals of evidence-based dentistry by helping to provide a foundation of evidence on which to base clinical decisions as opposed to relying on anecdotal evidence. PBRNs strengthen the professional knowledge base by applying the principles of good clinical practice, creating a resource for future dental faculty, training practitioners on best practices, and increasing the responsibility, accountability, and scope of care. PBRNs can be the future pivotal instruments of change in dental education, the use of electronic health record systems, diagnostic codes, and the role of comparative effectiveness research, which can create an unprecedented opportunity for the dental profession to advance and be integrated into the health care system. PMID:21828299

Fission-product SiC reaction in HTGR fuel

International Nuclear Information System (INIS)

Montgomery, F.

1981-01-01

The primary barrier to release of fission product from any of the fuel types into the primary circuit of the HTGR are the coatings on the fuel particles. Both pyrolytic carbon and silicon carbide coatings are very effective in retaining fission gases under normal operating conditions. One of the possible performance limitations which has been observed in irradiation tests of TRISO fuel is chemical interaction of the SiC layer with fission products. This reaction reduces the thickness of the SiC layer in TRISO particles and can lead to release of fission products from the particles if the SiC layer is completely penetrated. The experimental section of this report describes the results of work at General Atomic concerning the reaction of fission products with silicon carbide. The discussion section describes data obtained by various laboratories and includes (1) a description of the fission products which have been found to react with SiC; (2) a description of the kinetics of silicon carbide thinning caused by fission product reaction during out-of-pile thermal gradient heating and the application of these kinetics to in-pile irradiation; and (3) a comparison of silicon carbide thinning in LEU and HEU fuels

SiC substrate defects and III-N heteroepitaxy

Energy Technology Data Exchange (ETDEWEB)

Poust, B D [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Koga, T S [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Sandhu, R [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Heying, B [Northrop Grumman Space Technology, Space and Electronics Group, Redondo Beach, CA 90278 (United States); Hsing, R [Northrop Grumman Space Technology, Space and Electronics Group, Redondo Beach, CA 90278 (United States); Wojtowicz, M [Northrop Grumman Space Technology, Space and Electronics Group, Redondo Beach, CA 90278 (United States); Khan, A [Department of Electrical Engineering, University of South Carolina, Columbia, SC (United States); Goorsky, M S [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States)

2003-05-21

This study addressed how defects in SiC substrates influence the crystallographic properties of AlGaN/GaN layers deposited by metallorganic vapour phase epitaxy and by molecular beam epitaxy. We employed double crystal reflection x-ray topography using symmetric (0008) and (00012) reflections with CuK{alpha} radiation ({lambda} = 1.54 A) to image dislocations, micropipes, and low angle boundaries in SiC substrates. Lattice strain near the core of a micropipe defect was estimated to be of the order of 10{sup -7}. The substrates investigated exhibited radial patterns of strain and, primarily, of tilt of the order of tens of arcsec. After deposition of the AlGaN and GaN layers, DCXRT images were generated from the substrate (0008) or (00012) and GaN epitaxial layer (0004) reflections. Full-width at half-maximum values ranging from {approx}100 to 300 arcsec were typical of the GaN reflections, while those of the 4H-SiC reflections were {approx}20-70 arcsec. Micropipes, tilt boundaries, and inclusions in the SiC were shown to produce structural defects in the GaN layers. A clear correlation between SiC substrate defects and GaN defects has been established.

SiC substrate defects and III-N heteroepitaxy

International Nuclear Information System (INIS)

Poust, B D; Koga, T S; Sandhu, R; Heying, B; Hsing, R; Wojtowicz, M; Khan, A; Goorsky, M S

2003-01-01

This study addressed how defects in SiC substrates influence the crystallographic properties of AlGaN/GaN layers deposited by metallorganic vapour phase epitaxy and by molecular beam epitaxy. We employed double crystal reflection x-ray topography using symmetric (0008) and (00012) reflections with CuKα radiation (λ = 1.54 A) to image dislocations, micropipes, and low angle boundaries in SiC substrates. Lattice strain near the core of a micropipe defect was estimated to be of the order of 10 -7 . The substrates investigated exhibited radial patterns of strain and, primarily, of tilt of the order of tens of arcsec. After deposition of the AlGaN and GaN layers, DCXRT images were generated from the substrate (0008) or (00012) and GaN epitaxial layer (0004) reflections. Full-width at half-maximum values ranging from ∼100 to 300 arcsec were typical of the GaN reflections, while those of the 4H-SiC reflections were ∼20-70 arcsec. Micropipes, tilt boundaries, and inclusions in the SiC were shown to produce structural defects in the GaN layers. A clear correlation between SiC substrate defects and GaN defects has been established

A Grande Reportagem no contexto informativo SIC

OpenAIRE

Colaço, Vanessa Alexandra Francisco

2014-01-01

Os telespectadores querem ver grandes reportagens? Como evoluíram as audiências da Grande Reportagem SIC? É este o produto premium da estação? Terá este formato um investimento e continuidade garantidas? Estas são algumas das questões formuladas e às quais se procurou dar resposta neste Relatório de Estágio. Neste trabalho traça-se o perfil do programa Grande Reportagem SIC, clarificando a linha editorial que lhe serviu de base, procurando perceber as suas dinâmicas e passando em revista mome...

High Temperature Memories in SiC Technology

OpenAIRE

Ekström, Mattias

2014-01-01

This thesis is part of the Working On Venus (WOV) project. The aim of the project is to design electronics in silicon carbide (SiC) that can withstand the extreme surface environmen  of Venus. This thesis investigates some possible computer memory technologies that could survive on the surface of Venus. A memory must be able to function at 460 °C and after a total radiation dose of at least 200 Gy (SiC). This thesis is a literature survey. The thesis covers several Random-Access Memory (RAM) ...

Dental Services Satisfaction and Perceived Quality in a School-Based Clinic in Cartagena, Colombia

OpenAIRE

Lora-Salgado, Irene Margarita; Tirado-Amador, Lesbia Rosa; Montoya-Mendoza, Jorge Luis; Simancas-Pallares, Miguel Angel

2016-01-01

Objective: to describe the level of quality and perception of satisfaction in attended users from a school-based dental clinic in Cartagena, Colombia. Methods: we performed a cross-sectional study in 277 patients. For data collection we applied a structured and self-administered survey asking for demographic, clinic attention topics and specific questions regarding quality and services satisfaction. Data analysis was performed through descriptive statistics with frequencies, proportions and 9...

Laser diagnostic and therapy of dental caries: the clinic point of view

International Nuclear Information System (INIS)

Paiva, Priscila Faria

2001-01-01

Dental caries's diagnosis is a major dentistry problem from the clinic point of view. The laser beam on the region of 655 nm induces the fluorescence of the compounds present in the hard tissue, quantifying differences between sound and carious enamel and dentine. Diagnodent (Kavo, Germany), showed to be effective regarding dental caries's diagnosis in the present research sampling. The Er:YAG laser (Kavo Key Laser 2, Germany) performed efficient cavity preparations in caries lesions of I and V class type, using up energies that ranged from 300 mJ to 350 mJ with 4 Hz repetition rate for the enamel; and from 250 mJ to 300 mJ with 4 Hz repetition rate for the dentine, and with 80 mJ with 6 Hz of repetition rate for laser conditioning. In the Er:YAG laser preparations no patient was anesthetized even when there were deeper cavities, and the maximum degree of pain ( which ranged from 0 to 10) was 4. In the control group with conventional high-speed drill two patients were anesthetized and the maximum degree of pain was 7. Restorations performed by conventional method of composite were equally satisfying both in caries groups of I and V class type and in the control group. The laser application in the operative dentistry office as a new method of diagnosis and dental preparations should be a good alternative to the use of the conventional dental drill. Nevertheless, dentistry practice has a lot to improve from technology progress, as well as new researches on laser dentistry are necessary in a long term. New types of lasers will come about and will increasingly improve the dental practice assistance and procedures quality. (author)

"Meaningful use" of EHR in dental school clinics: how to benefit from the U.S. HITECH Act's financial and quality improvement incentives.

Science.gov (United States)

Kalenderian, Elsbeth; Walji, Muhammad; Ramoni, Rachel B

2013-04-01

Through the 2009 HITECH (Health Information Technology for Economic and Clinical Health) Act, the U.S. government committed $27 billion to incentivize the adoption and "meaningful use" of certified electronic health records (EHRs) by providers, including dentists. Given their patient profiles, dental school clinics are in a position to benefit from this time-delimited commitment to support the adoption and use of certified EHR technology under the Medicaid-based incentive. The benefits are not merely financial: rather, the meaningful use objectives and clinical quality measures can drive quality improvement initiatives within dental practices and help develop a community of medical and dental professionals focused on quality. This article describes how dentists can qualify as eligible providers and the set of activities that must be undertaken and attested to in order to obtain this incentive. Two case studies describe the approaches that can be used to meet the Medicaid threshold necessary to be eligible for the incentive. Dentists can and have successfully applied for meaningful use incentive payments. Given the diverse set of patients who are treated at dental schools, these dental practices are among those most likely to benefit from the incentive programs.

Defects induced by helium implantation in SiC

International Nuclear Information System (INIS)

Oliviero, E.; Barbot, J.F.; Declemy, A.; Beaufort, M.F.; Oliviero, E.

2008-01-01

SiC is one of the considered materials for nuclear fuel conditioning and for the fabrication of some core structures in future nuclear generation reactors. For the development of this advance technology, a fundamental research on this material is of prime importance. In particular, the implantation/irradiation effects have to be understood and controlled. It is with this aim that the structural alterations induced by implantation/irradiation in SiC are studied by different experimental techniques as transmission electron microscopy, helium desorption, X-ray diffraction and Rutherford backscattering spectrometry. In this work, the different types of defects induced by helium implantation in SiC, point or primary defects (obtained at low energy (∼100 eV) until spread defects (obtained at higher energy (until ∼2 MeV)) are exposed. The amorphization/recrystallization and swelling phenomena are presented too. (O.M.)

SiC nanocrystals as Pt catalyst supports for fuel cell applications

DEFF Research Database (Denmark)

Dhiman, Rajnish; Morgen, Per; Skou, E.M.

2013-01-01

A robust catalyst support is pivotal to Proton Exchange Membrane Fuel Cells (PEMFCs) to overcome challenges such as catalyst support corrosion, low catalyst utilization and overall capital cost. SiC is a promising candidate material which could be applied as a catalyst support in PEMFCs. Si...... on the nanocrystals of SiC-SPR and SiC-NS by the polyol method. The SiC substrates are subjected to an acid treatment to introduce the surface groups, which help to anchor the Pt nano-catalysts. These SiC based catalysts have been found to have a higher electrochemical activity than commercially available Vulcan...... based catalysts (BASF & HISPEC). These promising results signal a new era of SiC based catalysts for fuel cell applications....

Reconstruction of pseudo three-dimensional dental image from dental panoramic radiograph and tooth surface shape

International Nuclear Information System (INIS)

Imura, Masataka; Kuroda, Yoshihiro; Oshiro, Osamu; Kuroda, Tomohiro; Kagiyama, Yoshiyuki; Yagi, Masakazu; Takada, Kenji; Azuma, Hiroko

2010-01-01

Three-dimensional volume data set is useful for diagnosis in dental treatments. However, to obtain three-dimensional images of a dental arch in general dental clinics is difficult. In this paper, we propose a method to reconstruct pseudo three-dimensional dental images from a dental panoramic radiograph and a tooth surface shape which can be obtained from three dimensional shape measurement of a dental impression. The proposed method finds an appropriate curved surface on which the dental panoramic radiograph is mapped by comparing a virtual panoramic image made from a tooth surface shape to a real panoramic radiograph. The developed pseudo three-dimensional dental images give clear impression of patient's dental condition. (author)

Dental caries experience and use of dental services among Brazilian prisoners.

Science.gov (United States)

Cavalcanti, Alessandro Leite; Rodrigues, Iris Sant Anna Araujo; de Melo Silveira, Ingrid Thays; de Oliveira, Thaliny Batista Sarmento; de Almeida Pinto, Magaly Suenya; Xavier, Alidianne Fabia Cabral; de Castro, Ricardo Dias; Padilha, Wilton Wilney Nascimento

2014-11-25

This ross-sectional study involving 127 male prisoners evaluates the use of dental services and dental caries among Brazilian inmates. Data were collected by interview and clinical examination. Sociodemographic and sentencing information as well as use of dental services, self-reported dental morbidity, self-perception, and oral health impacts were investigated. The mean DMFT index value was 19.72. Of the components, the decayed component showed the highest mean value (11.06 ± 5.37). Statistically significant association was found between DMFTs with values from 22 to 32 and oral health satisfaction (p = 0.002), difficulty speaking (p = 0.024), shame of talking (p = 0.004) and smiling (p dental services, 80% had their last dental appointment less than one year ago, with most visits occurring in prison (80%), with restorative treatment (32%), followed by dental pain (26.4%), being the main reasons for such appointments. Most prisoners used dental services provided by the prison. Although restorative treatment has been the main reason for the use of dental services, "decayed" and "missing" components contributed to the high mean DMFT index.

Nigerian Dental Journal

African Journals Online (AJOL)

... needs of dental practitioners in Nigeria, Africa and international community interested in the dental practice in the developing world. The NDJ is published biannually and accepts reports of original research, review articles, clinical case reports and innovations in surgical techniques related to dentistry and allied subjects ...

Is self interdental cleaning associated with dental plaque levels, dental calculus, gingivitis and periodontal disease?

Science.gov (United States)

Crocombe, L A; Brennan, D S; Slade, G D; Loc, D O

2012-04-01

To ascertain whether interdental cleaning behaviours of Australian adults were associated with lower levels of plaque, gingivitis and periodontal disease. Data were obtained from the National Survey of Adult Oral Health 2004-06. Outcome variables were three indicators of oral hygiene outcomes (the presence or not of dental plaque, dental calculus and gingivitis) and two of periodontal disease (the presence or not of at least one tooth with a periodontal pocket or clinical attachment loss of ≥ 4 mm). The independent variable was classified into the following three groups: regularly clean interproximally 'at least daily' (daily+); 'less than daily' (dental plaque (dental calculus (dental plaque and gingivitis, although there was no significant association between regular interdental cleaning and clinical attachment loss. © 2011 John Wiley & Sons A/S.

Expanded function allied dental personnel and dental practice productivity and efficiency.

Science.gov (United States)

Beazoglou, Tryfon J; Chen, Lei; Lazar, Vickie F; Brown, L Jackson; Ray, Subhash C; Heffley, Dennis R; Berg, Rob; Bailit, Howard L

2012-08-01

This study examined the impact of expanded function allied dental personnel on the productivity and efficiency of general dental practices. Detailed practice financial and clinical data were obtained from a convenience sample of 154 general dental practices in Colorado. In this state, expanded function dental assistants can provide a wide range of reversible dental services/procedures, and dental hygienists can give local anesthesia. The survey identified practices that currently use expanded function allied dental personnel and the specific services/procedures delegated. Practice productivity was measured using patient visits, gross billings, and net income. Practice efficiency was assessed using a multivariate linear program, Data Envelopment Analysis. Sixty-four percent of the practices were found to use expanded function allied dental personnel, and on average they delegated 31.4 percent of delegatable services/procedures. Practices that used expanded function allied dental personnel treated more patients and had higher gross billings and net incomes than those practices that did not; the more services they delegated, the higher was the practice's productivity and efficiency. The effective use of expanded function allied dental personnel has the potential to substantially expand the capacity of general dental practices to treat more patients and to generate higher incomes for dental practices.

Stress Wave attenuation in SiC3D/Al Composite

International Nuclear Information System (INIS)

Yuan Chunyuan; Wang Yangwei; Li Guoju; Zhang Xu; Gao Jubin

2013-01-01

SiC 3D /Al composite is a kind of special composite with interpenetrating network microstructure. The attenuation properties of stress wave propagation along the SiC 3D /Al composite are studied by a Split Hopkinson Pressure Bar system and FEM simulations, and the attenuation mechanism is discussed in this paper. Results show that the attenuation rate of the stress wave in the composite is up to 1.73MPa·mm −1 . The reduction of the amplitude of waves is caused by that plenty of interfaces between SiC and Al within the composite acting with stress waves. When the incident plane wave reaches the SiC 3D /Al interface, reflection wave and transmission wave propagates in different directions along the irregular interface between SiC phase and aluminium phase due to the impedance mismatch of them, which leads to the divergence of stress wave. At the same time, some stress micro-focuses occurs in the aluminium phase for the complex wave superimposition, and some plastic deformation may take place within such micro-regions, which results in the consumption of stress wave energy. In conclusion, the stress wave attenuation is derived from divergence and consumption of stress wave.

The Flipped Classroom for pre-clinical dental skills teaching - a reflective commentary.

Science.gov (United States)

Crothers, A J; Bagg, J; McKerlie, R

2017-05-12

A Flipped Classroom method for teaching of adult practical pre-clinical dental skills was introduced to the BDS curriculum in Glasgow during the 2015/2016 academic session. This report provides a commentary of the first year of employing this method - from the identification of the need to optimise teaching resources, through the planning, implementation and development of the method, with an early indication of performance.

Adult Dental Anxiety: Recent Assessment Approaches and Psychological Management in a Dental Practice Setting.

Science.gov (United States)

Humphris, Gerry; Spyt, James; Herbison, Alice G; Kelsey, Thomas W

2016-05-01

Dental anxiety of patients is a common feature of the everyday experience of dental practice. This article advocates the use of regular assessment of this psychological construct to assist in patient management. Various tools, such as the Modified Dental Anxiety Scale (MDAS), are available to monitor dental anxiety that are quick to complete and easy to interpret. Patient burden is low. A new mobile phone assessment system (DENTANX) is being developed for distribution. This application and other psychological interventions are being investigated to assist patients to receive dental care routinely. Clinical relevance: This article provides evidence and expert opinion on the worth of regular dental anxiety assessment in dental practice using structured tools, such as the Modified Dental Anxiety Scale, and consideration of psychological intervention development.

The Integration of Psychomotor Skills in a Hybrid-PBL Dental Curriculum: The Clinical Clerkships.

Science.gov (United States)

Walton, Joanne N.; MacNeil, M. A. J.; Harrison, Rosamund L.; Clark, D. Christopher

1998-01-01

Describes the restructuring of clinical clerkships at the University of British Columbia (Canada) dental school as part of a new, hybrid, problem-based learning (PBL) curriculum, focusing on strategies for integrating development of psychomotor skills. Methods of achieving both horizontal and vertical integration of competencies through grouping…

Effect of SiC particles on microarc oxidation process of magnesium matrix composites

International Nuclear Information System (INIS)

Wang, Y.Q.; Wang, X.J.; Gong, W.X.; Wu, K.; Wang, F.H.

2013-01-01

SiC particles are an important reinforced phase in metal matrix composites. Their effect on the microarc oxidation (MAO, also named plasma electrolytic oxidation-PEO) process of SiC p /AZ91 Mg matrix composites (MMCs) was studied and the mechanism was revealed. The corrosion resistance of MAO coating was also investigated. Voltage–time curves during MAO were recorded to study the barrier film status on the composites. Scanning electron microscopy was used to characterize the existing state of SiC particles in MAO. Energy dispersive X-ray spectrometry and X-ray photoelectron spectroscopy were used to analyze the chemical composition of the coating. Corrosion resistance of the bare and coated composites was evaluated by potentiodynamic polarization curves in 3.5% NaCl solution. Results showed that the integrality and electrical insulation properties of the barrier film on the composites were destroyed by the SiC particles. Consequently, the sparking discharge at the early stage of MAO was inhibited, and the growth efficiency of the MAO coating decreased with the increase in the volume fraction of SiC particles. SiC particles did not exist stably during MAO; they were oxidized or partially oxidized into SiO 2 before the overall sparking discharge. The transformation from semi-conductive SiC to insulating SiO 2 by oxidation restrained the current leakage at the original SiC positions and then promoted sparking discharge and coating growth. The corrosion current density of SiC p /AZ91 MMCs was reduced by two orders of magnitude after MAO treatment. However, the corrosion resistances of the coated composites were lower than that of the coated alloy.

Biomimetic synthesis of cellular SiC based ceramics from plant ...

Indian Academy of Sciences (India)

Unknown

SiC based materials so derived can be used in structural applications and in designing high temperature filters and catalyst supports. Keywords. Biomimetic synthesis; carbonaceous biopreform; biomorphic Si–SiC ceramic composites; porous cellular SiC ceramics. 1. Introduction. In recent years, there has been tremendous ...

Reliability Concerns for Flying SiC Power MOSFETs in Space

Science.gov (United States)

Galloway, K. F.; Witulski, A. F.; Schrimpf, R. D.; Sternberg, A. L.; Ball, D. R.; Javanainen, A.; Reed, R. A.; Sierawski, B. D.; Lauenstein, J-M

2018-01-01

SiC power MOSFETs are space-ready in terms of typical reliability measures. However, single event burnout (SEB) often occurs at voltages 50% or lower than specified breakdown. Data illustrating burnout for 1200 V devices is reviewed and the space reliability of SiC MOSFETs is discussed.

Pd/CeO2/SiC Chemical Sensors

Science.gov (United States)

Lu, Weijie; Collins, W. Eugene

2005-01-01

The incorporation of nanostructured interfacial layers of CeO2 has been proposed to enhance the performances of Pd/SiC Schottky diodes used to sense hydrogen and hydrocarbons at high temperatures. If successful, this development could prove beneficial in numerous applications in which there are requirements to sense hydrogen and hydrocarbons at high temperatures: examples include monitoring of exhaust gases from engines and detecting fires. Sensitivity and thermal stability are major considerations affecting the development of high-temperature chemical sensors. In the case of a metal/SiC Schottky diode for a number of metals, the SiC becomes more chemically active in the presence of the thin metal film on the SiC surface at high temperature. This increase in chemical reactivity causes changes in chemical composition and structure of the metal/SiC interface. The practical effect of the changes is to alter the electronic and other properties of the device in such a manner as to degrade its performance as a chemical sensor. To delay or prevent these changes, it is necessary to limit operation to a temperature sensor structures. The present proposal to incorporate interfacial CeO2 films is based partly on the observation that nanostructured materials in general have potentially useful electrical properties, including an ability to enhance the transfer of electrons. In particular, nanostructured CeO2, that is CeO2 with nanosized grains, has shown promise for incorporation into hightemperature electronic devices. Nanostructured CeO2 films can be formed on SiC and have been shown to exhibit high thermal stability on SiC, characterized by the ability to withstand temperatures somewhat greater than 700 C for limited times. The exchanges of oxygen between CeO2 and SiC prevent the formation of carbon and other chemical species that are unfavorable for operation of a SiC-based Schottky diode as a chemical sensor. Consequently, it is anticipated that in a Pd/CeO2/SiC Schottky

Considerations for use of dental photography and electronic media in dental education and clinical practice.

Science.gov (United States)

Stieber, Jane C; Nelson, Travis; Huebner, Colleen E

2015-04-01

Photography and electronic media are indispensable tools for dental education and clinical practice. Although previous research has focused on privacy issues and general strategies to protect patient privacy when sharing clinical photographs for educational purposes, there are no published recommendations for developing a functional, privacy-compliant institutional framework for the capture, storage, transfer, and use of clinical photographs and other electronic media. The aims of this study were to research patient rights relating to electronic media and propose a framework for the use of patient media in education and clinical care. After a review of the relevant literature and consultation with the University of Washington's director of privacy and compliance and assistant attorney general, the researchers developed a privacy-compliant framework to ensure appropriate capture, storage, transfer, and use of clinical photography and electronic media. A four-part framework was created to guide the use of patient media that reflects considerations of patient autonomy and privacy, informed consent, capture and storage of media, and its transfer, use, and display. The best practices proposed for capture, storage, transfer, and use of clinical photographs and electronic media adhere to the health care code of ethics (based on patient autonomy, nonmaleficence, beneficence, justice, and veracity), which is most effectively upheld by a practical framework designed to protect patients and limit institutional liability. Educators have the opportunity and duty to convey these principles to students who will become the next generation of dentists, researchers, and educators.

Synthesis of boron nitride nanotubes with SiC nanowire as template

International Nuclear Information System (INIS)

Zhong, B.; Song, L.; Huang, X.X.; Wen, G.W.; Xia, L.

2011-01-01

Highlights: → Boron nitride nanotubes (BNNTs) have been fabricated using SiC nanowires as template. → SiC nanowires could be effectively etched out by the vapors decomposed from ammonia borane, leading to the formation of BNNTs. → A template self-sacrificing mechanism is responsible for the formation of BNNTs. -- Abstract: A novel template method for the preparation of boron nitride nanotubes (BNNTs) using SiC nanowire as template and ammonia borane as precursor is reported. We find out that the SiC nanowires could be effectively etched out by the vapors decomposed from ammonia borane, leading to the formation of BNNTs. The as-prepared products are well characterized by means of complementary analytical techniques. A possible formation mechanism is disclosed. The method developed here paves the way for large scale production of BNNTs.

Nanocrystalline SiC film thermistors for cryogenic applications

Science.gov (United States)

Mitin, V. F.; Kholevchuk, V. V.; Semenov, A. V.; Kozlovskii, A. A.; Boltovets, N. S.; Krivutsa, V. A.; Slepova, A. S.; Novitskii, S. V.

2018-02-01

We developed a heat-sensitive material based on nanocrystalline SiC films obtained by direct deposition of carbon and silicon ions onto sapphire substrates. These SiC films can be used for resistance thermometers operating in the 2 K-300 K temperature range. Having high heat sensitivity, they are relatively low sensitive to the magnetic field. The designs of the sensors are presented together with a discussion of their thermometric characteristics and sensitivity to magnetic fields.

The views of part-time clinical teachers regarding their role in undergraduate education at the University of Bristol Dental School.

Science.gov (United States)

Puryer, J; McNally, L; O'Sullivan, D

2015-01-01

UK dental schools are reliant on part-time teachers to deliver the clinical educational component of the course, the majority with a background in general dental practice. Opportunities for promotion are limited, as is the support for obtaining educational qualifications. The aim of this study was to ascertain the views of such teachers at a dental school. An anonymous online survey was used to obtain both qualitative and quantitative views. The response rate was 80%. The school has n = 50 part-time clinical teachers, who have been teaching for, on average ten years, and for three sessions per week. Eighteen percent of teachers are recognised specialists. Forty-six percent of respondents have a formal teaching qualification, mostly at certificate level, and 55% thought it necessary to acquire a formal teaching qualification. Eighty-eight percent were happy with their role as clinical teachers. This study demonstrates that despite the lack of support and prospect of career progression, the majority of part-time clinical teachers at this institution are satisfied with their role.

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.

Knowledge, perceptions and clinical application of the shortened dental arch concept among Malaysian government dentists.

Science.gov (United States)

Kasim, Siti Kamilah Mohd; Razak, Ishak Abdul; Yusof, Zamros Yuzadi Mohd

2018-02-01

To assess the knowledge and perceptions of Malaysian government dentists regarding the shortened dental arch (SDA) concept and its application in clinical practice. The SDA concept refers to a specific type of dentition with intact anterior teeth and a reduction in posterior occlusal pairs. Dentists' knowledge and perceptions of the SDA concept can influence its application in clinical practice. A self-administered questionnaire on the SDA concept was distributed to 326 government dentists in the states of Selangor and Kuala Lumpur, Malaysia. The data were analysed using SPSS version 22 software. The response rate was 84.0%. The majority of respondents had good knowledge on five of six knowledge items and good attitudes towards 10 of 17 perception items. However, only one-fifth (20.4%) reported having applied the SDA concept in the clinic. A larger number of participants who graduated locally than who graduated abroad perceived that patients 5 years of work experience perceived that the SDA concept enables simpler treatment planning (P concept, it is not widely applied in the clinic. Concerted efforts in SDA training of dentists are needed to help to shorten denture waiting lists and reduce costs. © 2017 FDI World Dental Federation.

A comparison of computer- and hand-generated clinical dental notes with statutory regulations in record keeping.

Science.gov (United States)

McAndrew, R; Ban, J; Playle, R

2012-02-01

Dental patient records should be of high quality, contain information to allow for good continuity of care and clinical defence (should the need ever arise) and, ideally, facilitate clinical audit. Handwritten dental records have been assessed for their compliance to statutory regulations, but the same cannot be levelled at computer-generated notes. This study aimed to compare and analyse the compliance of both methods of data recording with statutory regulations. Fifty consecutive sets of handwritten notes and 50 sets of computer-generated notes were audited for compliance with a number of legal requirements and desirable characteristics for dental records and the results compared. The standard set for compliance with all characteristics was 100%. The computer-generated notes satisfied the set standard for 8 of the 11 legal requirements and three of six desirable characteristics. The handwritten notes satisfied the set standard for 1 of 11 legal requirements and none of the desirable characteristics. A statistical difference (using a 95% confidence interval) between the two methods was observed in 5 of 11 legal characteristics and three of six desirable characteristics, all of which were in favour of computer-generated notes. Within the limitations of this study, computer-generated notes achieved a much higher compliance rate with the set parameters, making defence in cases of litigation, continuity of care and clinical audit easier and more efficient. © 2011 John Wiley & Sons A/S.

Gonioscopic changes in conventional ECCE vs manual SICS: A comparative study

Directory of Open Access Journals (Sweden)

Surya Joseph, Sundararajan D, Rajvin Samuel Ponraj, Srinivasan M, Veluchamy

2014-04-01

Full Text Available The aim of the study is to observe and compare the Gonioscopic changes in the angle of the anterior chamber of the eye after surgeries namely; Conventional Extra capsular cataract extraction (ECCE with Posterior chamber Intraocular lens (PC IOL implantation, Manual Small incision Cataract Surgery with PCIOL implantation. The clinical study was undertaken after Institutional Ethical committee clearance, securing the inform consent, total number of 100 patients were enrolled in the study. 50 ECCE; 50 SICS consisting of 57 Males and 43 Females aged between 40 – 80yrs who were admitted and operated for Cataract at Meenakshi Medical college Hospital & Research institute. The following parameters are studied: Gonioscopic changes in the angle, namely the PAS formation in the quadrants, pigment dispersion in each of the methods. After this study, we arrive to a conclusion that complications in the angle of anterior chamber occur mostly in Conventional with insignificant change in manual SICS. So manual Small incision Cataract Surgery with PCIOL implantation is preferable over Conventional ECCE with PCIOL implantation.

Properties and Clinical Application of Three Types of Dental Glass-Ceramics and Ceramics for CAD-CAM Technologies

Science.gov (United States)

Ritzberger, Christian; Apel, Elke; Höland, Wolfram; Peschke, Arnd; Rheinberger, Volker M.

2010-01-01

The main properties (mechanical, thermal and chemical) and clinical application for dental restoration are demonstrated for three types of glass-ceramics and sintered polycrystalline ceramic produced by Ivoclar Vivadent AG. Two types of glass-ceramics are derived from the leucite-type and the lithium disilicate-type. The third type of dental materials represents a ZrO2 ceramic. CAD/CAM technology is a procedure to manufacture dental ceramic restoration. Leucite-type glass-ceramics demonstrate high translucency, preferable optical/mechanical properties and an application as dental inlays, onlays and crowns. Based on an improvement of the mechanical parameters, specially the strength and toughness, the lithium disilicate glass-ceramics are used as crowns; applying a procedure to machine an intermediate product and producing the final glass-ceramic by an additional heat treatment. Small dental bridges of lithium disilicate glass-ceramic were fabricated using a molding technology. ZrO2 ceramics show high toughness and strength and were veneered with fluoroapatite glass-ceramic. Machining is possible with a porous intermediate product.

Does dental caries affect dental development in children and adolescents?

Science.gov (United States)

Dhamo, Brunilda; Elezi, Besiana; Kragt, Lea; Wolvius, Eppo B; Ongkosuwito, Edwin M

2018-01-01

Although a link between dietary changes, caries, and dental development has been observed, the literature provides little insight about this relationship. The aim of our study was to investigate the association between dental caries and dental development in a clinical sample of Albanian children and adolescents. In total, 118 children and adolescents, born between 1995 and 2004 and aged 6–15 years, were included. Dental caries in the deciduous dentition was assessed using the Decayed, Filled Teeth (dft) index and dental caries in the permanent dentition was assessed using the Decayed, Missing, Filled Teeth (DMFT) index. Dental development during the permanent dentition was determined using the Demirjian method. Linear and ordinal regression models were applied to analyze the associations of dental caries with dental age and developmental stages of each left mandibular tooth. Dental caries in the deciduous dentition, estimated as a median dft of 2.0 (90% range, 0.0–9.1), was significantly associated with lower dental age (β = -0.21; 90% CI: -0.29, -0.12) and with delayed development of the canine, both premolars, and the second molar. Untreated dental caries (dt) was associated with lower dental age (β = -0.19; 90% CI: -0.28, -0.10). Dental caries in the permanent dentition, estimated as a median DMFT of 1.0 (90% range, 0.0–8.0), was not significantly associated with dental age (β = 0.05; 90% CI: -0.04, 0.14). However, the DMFT was associated with the advanced stages of development of both premolars and the second molar. The untreated dental caries in the deciduous dentition delays the development of permanent teeth. PMID:29659350

Relationship of periodontal clinical parameters with bacterial composition in human dental plaque.

Science.gov (United States)

Fujinaka, Hidetake; Takeshita, Toru; Sato, Hirayuki; Yamamoto, Tetsuji; Nakamura, Junji; Hase, Tadashi; Yamashita, Yoshihisa

2013-06-01

More than 600 bacterial species have been identified in the oral cavity, but only a limited number of species show a strong association with periodontitis. The purpose of the present study was to provide a comprehensive outline of the microbiota in dental plaque related to periodontal status. Dental plaque from 90 subjects was sampled, and the subjects were clustered based on bacterial composition using the terminal restriction fragment length polymorphism of 16S rRNA genes. Here, we evaluated (1) periodontal clinical parameters between clusters; (2) the correlation of subgingival bacterial composition with supragingival bacterial composition; and (3) the association between bacterial interspecies in dental plaque using a graphical Gaussian model. Cluster 1 (C1) having high prevalence of pathogenic bacteria in subgingival plaque showed increasing values of the parameters. The values of the parameters in Cluster 2a (C2a) having high prevalence of non-pathogenic bacteria were markedly lower than those in C1. A cluster having low prevalence of non-pathogenic bacteria in supragingival plaque showed increasing values of the parameters. The bacterial patterns between subgingival plaque and supragingival plaque were significantly correlated. Chief pathogens, such as Porphyromonas gingivalis, formed a network with other pathogenic species in C1, whereas a network of non-pathogenic species, such as Rothia sp. and Lautropia sp., tended to compete with a network of pathogenic species in C2a. Periodontal status relates to non-pathogenic species as well as to pathogenic species, suggesting that the bacterial interspecies connection affects dental plaque virulence.

Dental radiology for children

International Nuclear Information System (INIS)

Myers, D.R.

1984-01-01

The benefit for the child from the judicious use of diagnostic dental radiography is improved dental health. The risk to the child from dental diagnostic radiation exposure appears to be extremely low. Despite the low risk, the dentist must minimize the child's exposure to ionizing radiation by using sound clinical judgment to determine what radiographs are necessary and to provide children with optimal protection from ionizing radiation

A Mid-Level Dental Provider in Oregon: Dental hygienists' perceptions.

Science.gov (United States)

Coplen, Amy E; Bell, Kathryn; Aamodt, Gail L; Ironside, Lynn

2017-10-01

Purpose: Many states are exploring alternative provider models and examining the role of the dental hygienist to address access to care challenges as the United States continues to face increasing demands for oral healthcare services. The purpose of this study was to assess dental hygienists' opinions in the state of Oregon regarding the current limitations of dental hygienists' scope of practice, perceived need for a mid-level provider in Oregon, and personal interest in becoming a mid-level provider. Methods: In December 2013 a survey was mailed to a sample of 1,231 dental hygienists registered in Oregon representing 30% of the licentiates. All licentiates holding expanded practice permits (EPP) were included in the sample (n=351). The following categories were included in the 32-question survey: scope of practice, mid-level provider, current practice, and demographics. Results: A total of 440 surveys were returned for a response rate of 36%. Of the EPP holders, 51% responded to the survey. Over half of respondents (59%) believe that a mid-level provider is needed in the state. Respondents holding membership in the American Dental Hygienists' Association, as well as EPP holders, were significantly more likely to respond that a mid-level dental provider was needed in the state (plevel provider was introduced in Oregon, the new provider should be a registered dental hygienist model. Forty-three percent (n=186) of respondents were interested in becoming mid-level providers and 47% (n=203) of respondents believed that the minimum education for a mid-level provider should be a bachelor's degree. The majority, 74% (n=137), of those interested in becoming a mid-level provider indicated a preference in completing their education through online teaching combined with a clinical internship. Conclusion: There is strong support from dental hygienists in Oregon that a need exists for a mid-level dental provider and that this provider model should be dental hygiene based

Aging of monolithic zirconia dental prostheses: Protocol for a 5-year prospective clinical study using ex vivo analyses.

Science.gov (United States)

Koenig, Vinciane; Wulfman, Claudine P; Derbanne, Mathieu A; Dupont, Nathalie M; Le Goff, Stéphane O; Tang, Mie-Leng; Seidel, Laurence; Dewael, Thibaut Y; Vanheusden, Alain J; Mainjot, Amélie K

2016-12-15

Recent introduction of computer-aided design/computer-aided manufacturing (CAD/CAM) monolithic zirconia dental prostheses raises the issue of material low thermal degradation (LTD), a well-known problem with zirconia hip prostheses. This phenomenon could be accentuated by masticatory mechanical stress. Until now zirconia LTD process has only been studied in vitro . This work introduces an original protocol to evaluate LTD process of monolithic zirconia prostheses in the oral environment and to study their general clinical behavior, notably in terms of wear. 101 posterior monolithic zirconia tooth elements (molars and premolars) are included in a 5-year prospective clinical trial. On each element, several areas between 1 and 2 mm 2 (6 on molars, 4 on premolars) are determined on restoration surface: areas submitted or non-submitted to mastication mechanical stress, glazed or non-glazed. Before prosthesis placement, ex vivo analyses regarding LTD and wear are performed using Raman spectroscopy, SEM imagery and 3D laser profilometry. After placement, restorations are clinically evaluated following criteria of the World Dental Federation (FDI), complemented by the analysis of fracture clinical risk factors. Two independent examiners perform the evaluations. Clinical evaluation and ex vivo analyses are carried out after 6 months and then each year for up to 5 years. For clinicians and patients, the results of this trial will justify the use of monolithic zirconia restorations in dental practice. For researchers, the originality of a clinical study including ex vivo analyses of material aging will provide important data regarding zirconia properties.Trial registration: ClinicalTrials.gov Identifier: NCT02150226.

Plasmon-assisted photoluminescence enhancement of SiC nanocrystals by proximal silver nanoparticles

International Nuclear Information System (INIS)

Zhang, N.; Dai, D.J.; Fan, J.Y.

2012-01-01

Highlights: ► We studied metal surface plasmon-enhanced photoluminescence in SiC nanocrystals. ► The integrated emission intensity can be enhanced by 17 times. ► The coupling between SiC emission and Ag plasmon oscillation induces the enhancement. ► The enhancement is tunable with varied spacing thickness of electrolytes. - Abstract: Plasmon-enhanced photoluminescence has wide application potential in many areas, whereas the underlying mechanism is still in debate. We report the photoluminescence enhancement in SiC nanocrystal–Ag nanoparticle coupled system spaced by the poly(styrene sulfonic acid) sodium salt/poly(allylamine hydrochloride) polyelectrolyte bilayers. The integrated luminescence intensity can be improved by up to 17 times. Our analysis indicates that the strong coupling between the SiC nanocrystals and the surface plasmon oscillation of the silver nanoparticles is the major cause of the luminescence enhancement. These findings will help to understand the photoluminescence enhancement mechanism as well as widen the applications of the SiC nanocrystals in photonics and life sciences.

The role of Pd in the transport of Ag in SiC

International Nuclear Information System (INIS)

Olivier, E.J.; Neethling, J.H.

2013-01-01

This paper presents results in support of a newly proposed transport mechanism to account for the release of Ag from intact TRISO particles during HTR reactor operation. The study reveals that the migration of Ag in polycrystalline SiC can occur in association with Pd, a relatively high yield metallic fission product. The migration takes place primarily along grain boundary routes, seen in the form of distinct Pd, Ag and Si containing nodules. Pd is known to rapidly migrate to the SiC and iPyC interface within TRISO particles during operation. It has been shown to chemically corrode the SiC to form palladium silicides. These palladium silicides are found present along SiC grain boundaries in nodule like form. It is suggested that Ag penetrates these nodules together with the palladium silicide, to form a Pd, Ag and Si solution capable of migrating along SiC grain boundaries over time.

The role of Pd in the transport of Ag in SiC

Energy Technology Data Exchange (ETDEWEB)

Olivier, E.J., E-mail: jolivier@nmmu.ac.za [Centre for High Resolution Transmission Electron Microscopy, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Neethling, J.H. [Centre for High Resolution Transmission Electron Microscopy, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

2013-01-15

This paper presents results in support of a newly proposed transport mechanism to account for the release of Ag from intact TRISO particles during HTR reactor operation. The study reveals that the migration of Ag in polycrystalline SiC can occur in association with Pd, a relatively high yield metallic fission product. The migration takes place primarily along grain boundary routes, seen in the form of distinct Pd, Ag and Si containing nodules. Pd is known to rapidly migrate to the SiC and iPyC interface within TRISO particles during operation. It has been shown to chemically corrode the SiC to form palladium silicides. These palladium silicides are found present along SiC grain boundaries in nodule like form. It is suggested that Ag penetrates these nodules together with the palladium silicide, to form a Pd, Ag and Si solution capable of migrating along SiC grain boundaries over time.

Nucleation and growth of polycrystalline SiC

DEFF Research Database (Denmark)

Kaiser, M.; Schimmel, S.; Jokubavicius, V.

2014-01-01

The nucleation and bulk growth of polycrystalline SiC in a 2 inch PVT setup using isostatic and pyrolytic graphite as substrates was studied. Textured nucleation occurs under near-thermal equilibrium conditions at the initial growth stage with hexagonal platelet shaped crystallites of 4H, 6H and 15......R polytypes. It is found that pyrolytic graphite results in enhanced texturing of the nucleating gas species. Reducing the pressure leads to growth of the crystallites until a closed polycrystalline SiC layer containing voids with a rough surface is developed. Bulk growth was conducted at 35 mbar Ar...

with gingivitis and periodontitis referring Resalat Dental Clinic, Chaleshtor in 2015

Directory of Open Access Journals (Sweden)

MS Khafari ghosheh

2017-05-01

Full Text Available Abstract   Background & aim: Entamoeba gingivalis and Trichomonas tenax are oral protozoa that could cause periodontitis and gingivitis. The present study was done to determine the prevalence of these two protozoa in people over 14 years with periodontitis and gingivitis.   Methods: In this descriptive, cross-sectional study, 540 patients referring Resalat Dental Clinic, Shahrekord were enrolled and assigned in two groups of 270 patients with periodontitis and gingivitis and270 healthy individuals. The prepared specimens were examined by extensive wet procedures, Gimsa staining and Trichorom staining. Data were analyzed by chi-square, Fisher’s exact test, and logistic regression in SPSSv.20.   Results: No E. gingivalis- and T. tenax-positive cases were seen in the healthy group. The prevalence of E. gingivalis and T. tenax was obtained 3% by extensive wet procedure, 1.9% by Trichoderma staining, and 0.7% by Giemsa staining respectively. By logistic regression model, none of variables of age, gender, place of residence, smoking, tooth brushing, flossing, and oral PH were associated protozoan infection of E. gingivalis and T. tenax (P>0.05. Conclusion: In patients with periodontitis and gingivitis referred to the dental clinic, parasitic infections were attenuated to gingivialis and trichomoniasis vaginalis, and possibly other non-parasitic agents, including bacteria or other microorganisms, may play a role.    

PhySIC: a veto supertree method with desirable properties.

Science.gov (United States)

Ranwez, Vincent; Berry, Vincent; Criscuolo, Alexis; Fabre, Pierre-Henri; Guillemot, Sylvain; Scornavacca, Celine; Douzery, Emmanuel J P

2007-10-01

This paper focuses on veto supertree methods; i.e., methods that aim at producing a conservative synthesis of the relationships agreed upon by all source trees. We propose desirable properties that a supertree should satisfy in this framework, namely the non-contradiction property (PC) and the induction property (PI). The former requires that the supertree does not contain relationships that contradict one or a combination of the source topologies, whereas the latter requires that all topological information contained in the supertree is present in a source tree or collectively induced by several source trees. We provide simple examples to illustrate their relevance and that allow a comparison with previously advocated properties. We show that these properties can be checked in polynomial time for any given rooted supertree. Moreover, we introduce the PhySIC method (PHYlogenetic Signal with Induction and non-Contradiction). For k input trees spanning a set of n taxa, this method produces a supertree that satisfies the above-mentioned properties in O(kn(3) + n(4)) computing time. The polytomies of the produced supertree are also tagged by labels indicating areas of conflict as well as those with insufficient overlap. As a whole, PhySIC enables the user to quickly summarize consensual information of a set of trees and localize groups of taxa for which the data require consolidation. Lastly, we illustrate the behaviour of PhySIC on primate data sets of various sizes, and propose a supertree covering 95% of all primate extant genera. The PhySIC algorithm is available at http://atgc.lirmm.fr/cgi-bin/PhySIC.

Passivation of hexagonal SiC surfaces by hydrogen termination

International Nuclear Information System (INIS)

Seyller, Thomas

2004-01-01

Surface hydrogenation is a well established technique in silicon technology. It is easily accomplished by wet-chemical procedures and results in clean and unreconstructed surfaces, which are extremely low in charged surface states and stable against oxidation in air, thus constituting an ideal surface preparation. As a consequence, methods for hydrogenation have been sought for preparing silicon carbide (SiC) surfaces with similar well defined properties. It was soon recognized, however, that due to different surface chemistry new ground had to be broken in order to find a method leading to the desired monatomic hydrogen saturation. In this paper the results of H passivation of SiC surfaces by high-temperature hydrogen annealing will be discussed, thereby placing emphasis on chemical, structural and electronic properties of the resulting surfaces. In addition to their unique properties, hydrogenated hexagonal SiC {0001} surfaces offer the interesting possibility of gaining insight into the formation of silicon- and carbon-rich reconstructions as well. This is due to the fact that to date hydrogenation is the only method providing oxygen-free surfaces with a C to Si ratio of 1:1. Last but not least, the electronic properties of hydrogen-free SiC {0001} surfaces will be alluded to. SiC {0001} surfaces are the only known semiconductor surfaces that can be prepared in their unreconstructed (1 x 1) state with one dangling bond per unit cell by photon induced hydrogen desorption. These surfaces give indications of a Mott-Hubbard surface band structure

Large area SiC coating technology of RBSC for semiconductor processing component

International Nuclear Information System (INIS)

Park, Ji Yeon; Kim, Weon Ju

2001-06-01

As the semiconductor process is developed for the larger area wafer and the larger-scale integration, the processing fixtures are required to have excellent mechanical and high temperature properties. This highlights the importance of silicon carbide-based materials as a substitute for quartz-based susceptors. In this study, SiC coating technology on reaction sintered (RS) SiC with thickness variation of +/- 10% within a diameter of 8 inch by low pressure chemical vapor deposition has been developed for making a plate type SiC fixture such as heater, baffle, etc., with a diameter of 12 inch. Additionally, a state of art on fabrication technology and products of the current commercial SiC fixtures has been described

Large area SiC coating technology of RBSC for semiconductor processing component

Energy Technology Data Exchange (ETDEWEB)

Park, Ji Yeon; Kim, Weon Ju

2001-06-01

As the semiconductor process is developed for the larger area wafer and the larger-scale integration, the processing fixtures are required to have excellent mechanical and high temperature properties. This highlights the importance of silicon carbide-based materials as a substitute for quartz-based susceptors. In this study, SiC coating technology on reaction sintered (RS) SiC with thickness variation of +/- 10% within a diameter of 8 inch by low pressure chemical vapor deposition has been developed for making a plate type SiC fixture such as heater, baffle, etc., with a diameter of 12 inch. Additionally, a state of art on fabrication technology and products of the current commercial SiC fixtures has been described.

Characterisation of 10 kV 10 A SiC MOSFET

DEFF Research Database (Denmark)

Eni, Emanuel-Petre; Incau, Bogdan Ioan; Munk-Nielsen, Stig

2015-01-01

The objective of this paper is to characterize and evaluate the static and dynamic performances of 10 kV 10 A 4H-SIC MOSFETs at high temperatures. The results show good electrical performances of the SiC MOSFETs for high temperature operations. The double-pulse test results showed interesting...

CVD of SiC and AlN using cyclic organometallic precursors

Science.gov (United States)

Interrante, L. V.; Larkin, D. J.; Amato, C.

1992-01-01

The use of cyclic organometallic molecules as single-source MOCVD precursors is illustrated by means of examples taken from our recent work on AlN and SiC deposition, with particular focus on SiC. Molecules containing (AlN)3 and (SiC)2 rings as the 'core structure' were employed as the source materials for these studies. The organoaluminum amide, (Me2AlNH2)3, was used as the AlN source and has been studied in a molecular beam sampling apparatus in order to determine the gas phase species present in a hot-wall CVD reactor environment. In the case of SiC CVD, a series of disilacyclobutanes (Si(XX')CH2)2 (with X and X' = H, CH3, and CH2SiH2CH3), were examined in a cold-wall, hot-stage CVD reactor in order to compare their relative reactivities and prospective utility as single-source CVD precursors. The parent compound, disilacyclobutane, (SiH2CH2)2, was found to exhibit the lowest deposition temperature (ca. 670 C) and to yield the highest purity SiC films. This precursor gave a highly textured, polycrystalline film on the Si(100) substrates.

Investigational Clinical Trial of a Prototype Optoelectronic Computer-Aided Navigation Device for Dental Implant Surgery.

Science.gov (United States)

Jokstad, Asbjørn; Winnett, Brenton; Fava, Joseph; Powell, David; Somogyi-Ganss, Eszter

New digital technologies enable real-time computer-aided (CA) three-dimensional (3D) guidance during dental implant surgery. The aim of this investigational clinical trial was to demonstrate the safety and effectiveness of a prototype optoelectronic CA-navigation device in comparison with the conventional approach for planning and effecting dental implant surgery. Study participants with up to four missing teeth were recruited from the pool of patients referred to the University of Toronto Graduate Prosthodontics clinic. The first 10 participants were allocated to either a conventional or a prototype device study arm in a randomized trial. The next 10 participants received implants using the prototype device. All study participants were restored with fixed dental prostheses after 3 (mandible) or 6 (maxilla) months healing, and monitored over 12 months. The primary outcome was the incidence of any surgical, biologic, or prosthetic adverse events or device-related complications. Secondary outcomes were the incidence of positioning of implants not considered suitable for straightforward prosthetic restoration (yes/no); the perception of the ease of use of the prototype device by the two oral surgeons, recorded by use of a Likert-type questionnaire; and the clinical performance of the implant and superstructure after 1 year in function. Positioning of the implants was appraised on periapical radiographs and clinical photographs by four independent blinded examiners. Peri-implant bone loss was measured on periapical radiographs by a blinded examiner. No adverse events occurred related to placing any implants. Four device-related complications led to a switch from using the prototype device to the conventional method. All implants placed by use of the prototype device were in a position considered suitable for straightforward prosthetic restoration (n = 21). The qualitative evaluation by the surgeons was generally positive, although ergonomic challenges were identified

Deposition of thin ultrafiltration membranes on commercial SiC microfiltration tubes

DEFF Research Database (Denmark)

Facciotti, Marco; Boffa, Vittorio; Magnacca, Giuliana

2014-01-01

Porous SiC based materials present high mechanical, chemical and thermal robustness, and thus have been largely applied to water-filtration technologies. In this study, commercial SiC microfiltration tubes with nominal pore size of 0.04 m were used as carrier for depositing thin aluminium oxide....... After 5 times coating, a 5.6 µm thick γ-Al2O3 layer was obtained. This membrane shows retention of ~75% for polyethylene glycol molecules with Mn of 8 and 35 kDa, indicating that, despite their intrinsic surface roughness, commercial SiC microfiltration tubes can be applied as carrier for thin...... ultrafiltration membranes. This work also indicates that an improvement of the commercial SiC support surface smoothness may greatly enhance permeance and selectivity of Υ-Al2O3 ultrafiltration membranes by allowing the deposition of thinner defect-free layers....

Awareness, Knowledge, and Attitude of Dental Students toward ...

African Journals Online (AJOL)

2018-05-22

May 22, 2018 ... clinical dentistry as there is an increase in the prevalence of infectious diseases among dental ... procedures for infection control in dental schools and clinics. Objectives: ... former were regularly disinfecting dental cast before sending it to the laboratory and later ..... improve their quality of life. This survey ...

White light emission from fluorescent SiC with porous surface

DEFF Research Database (Denmark)

Lu, Weifang; Ou, Yiyu; Fiordaliso, Elisabetta Maria

2017-01-01

We report for the frst time a NUV light to white light conversion in a N-B co-doped 6H-SiC (fuorescent SiC) layer containing a hybrid structure. The surface of fuorescent SiC sample contains porous structures fabricated by anodic oxidation method. After passivation by 20nm thick Al2O3, the photol......We report for the frst time a NUV light to white light conversion in a N-B co-doped 6H-SiC (fuorescent SiC) layer containing a hybrid structure. The surface of fuorescent SiC sample contains porous structures fabricated by anodic oxidation method. After passivation by 20nm thick Al2O3...... the bulk fuorescent SiC layer. A high color rendering index of 81.1 has been achieved. Photoluminescence spectra in porous layers fabricated in both commercial n-type and lab grown N-B co-doped 6H-SiC show two emission peaks centered approximately at 460nm and 530nm. Such bluegreen emission phenomenon can......, the photoluminescence intensity from the porous layer was signifcant enhanced by a factor of more than 12. Using a porous layer of moderate thickness (~10µm), high-quality white light emission was realized by combining the independent emissions of blue-green emission from the porous layer and yellow emission from...

Dental Environmental Noise Evaluation and Health Risk Model Construction to Dental Professionals.

Science.gov (United States)

Ma, Kuen Wai; Wong, Hai Ming; Mak, Cheuk Ming

2017-09-19

Occupational noise is unavoidably produced from dental equipment, building facilities, and human voices in the dental environment. The purpose of this study was to investigate the effect of occupational noise exposure on the dental professionals' health condition. The psychoacoustics approach noise exposure assessment followed by the health risk assessment was carried on at the paediatric dentistry clinic and the dental laboratory in the Prince Philip Dental Hospital of Hong Kong. The A-weighted equivalent sound level, total loudness, and sharpness values were statistically significantly higher for the noise at the laboratory than that at the clinic. The degree of perceived influences and sharpness of noise were found to have the impacts on the dental professionals' working performance and health. Moreover, the risk of having a bad hearing state would a have 26% and 31% higher chance for a unit increment of the short-term and long-term impact scores, respectively. The dental professionals with the service length more than 10 years and the daily working hours of more than eight showed the highest risk to their hearing state. The worse the hearing state was, the worse the health state was found for the dental professionals. Also, the risk of dissatisfaction would be increased by 4.41 and 1.22 times for those who worked at the laboratory and a unit increment of the long-term impact score. The constructed health risk mode with the scientific and statistical evidence is hence important for the future noise management of environmental improvement.

Dental magnetic resonance imaging

International Nuclear Information System (INIS)

Hilgenfeld, Tim; Bendszus, Martin; Haehnel, Stefan

2016-01-01

Growing distribution and utilization of digital volume tomography (DVT) extend the spectrum of clinical dental imaging. Additional diagnostic value, however, comes along with an increasing amount of radiation. In contrast, magnetic resonance imaging is a radiation free imaging technique. Furthermore, it offers a high soft tissue contrast. Morphological and numerical dental anomalies, differentiation of periapical lesions and exclusion of complications of dental diseases are field of applications for dental MRI. In addition, detection of caries and periodontal lesions and injury of inferior alveolar nerve are promising application areas in the future.

Clinical utility of dental cone-beam computed tomography: current perspectives

Directory of Open Access Journals (Sweden)

Jaju PP

2014-04-01

Full Text Available Prashant P Jaju,1 Sushma P Jaju21Oral Medicine and Radiology, 2Conservative Dentistry and Endodontics, Rishiraj College of Dental Sciences and Research Center, Bhopal, IndiaAbstract: Panoramic radiography and computed tomography were the pillars of maxillofacial diagnosis. With the advent of cone-beam computed tomography, dental practice has seen a paradigm shift. This review article highlights the potential applications of cone-beam computed tomography in the fields of dental implantology and forensic dentistry, and its limitations in maxillofacial diagnosis.Keywords: dental implants, cone-beam computed tomography, panoramic radiography, computed tomography

Qualification of SiC materials for fusion and fission reactors

International Nuclear Information System (INIS)

Ryazanov, Alexander

2009-01-01

Ceramic materials such as silicon carbide (SiC) and SiC/SiC composites are both considered, due to their high-temperature strength, pseudo-ductile fracture behavior and low-induced radioactivity, as candidate materials for fusion reactor (test blanket module for ITER) and high temperature gas-cooled reactors (HTGR). The radiation swelling and creep of SiC are very important physical phenomena that determine the radiation resistance of them in these reactors. Other important problem which exists especially in fusion reactor is an effect of accumulation of high concentrations of helium atoms in SiC (up to 15000-20000 at.ppm) due to (n,α) nuclear reaction on physical mechanical properties. An understanding of the physical mechanism of this phenomenon is very important for the investigations of helium atom effect on radiation swelling in SiC. In this report a compilation of non-irradiated and irradiated properties of SiC are provided and analyzed in terms of their application to fusion and high temperature gas cooled reactors. Special topic of this report is oriented on the micro structural changes in chemically vapor-deposited (CVD) high-purity beta-SiC during neutron and ion irradiations at elevated temperatures. The evolutions of various radiation induced defects including dislocation loops, network dislocations and cavities are presented here as a function of irradiation temperature and fluencies. These observations are discussed in relation with such irradiation phenomena in SiC as low temperature swelling and cavity swelling. One of the main difficulties in the radiation damage studies of SiC materials lies in the absence of theoretical models and interpretation of many physical mechanisms of radiation phenomena including the radiation swelling and creep. The point defects in ceramic materials are characterized by the charge states and they can have an effective charge. The internal effective electrical field is formed due to the accumulation of charged point

10kV SiC MOSFET split output power module

DEFF Research Database (Denmark)

Beczkowski, Szymon; Li, Helong; Uhrenfeldt, Christian

2015-01-01

The poor body diode performance of the first generation of 10kV SiC MOSFETs and the parasitic turn-on phenomenon limit the performance of SiC based converters. Both these problems can potentially be mitigated using a split output topology. In this paper we present a comparison between a classical...

Energy efficiency improvement target for SIC 34 - fabricated metal products

Energy Technology Data Exchange (ETDEWEB)

Byrer, T. G.; Billhardt, C. F.; Farkas, M. S.

1977-03-15

A March 15, 1977 revision of a February 15, 1977 document on the energy improvement target for the Fabricated Metal Products industry (SIC 34) is presented. A net energy savings in 1980 of 24% as compared with 1972 energy consumption in SIC 34 is considered a realistic goal. (ERA citation 04:045008)

SiC Coating Process Development Using H-PCS in Supercritical CO2

International Nuclear Information System (INIS)

Park, Kwangheon; Jung, Wonyoung

2013-01-01

We tried SiC coating using supercritical fluids. Supercritical fluids are the substance exists over critical temperature and critical pressure. It is hard to expect that there would be a big change as single-solvent as the fluid is incompressible and the space between the molecules is almost steady. But the fluid which is being supercritical can bring a great change when it is changed its pressure near its critical point, showing its successive change in the density, viscosity, diffusion coefficient and the polarity. We have tested the 'H-PCS into SiC' coating experiment with supercritical CO 2 which has the high penetration, low viscosity as well as the high density and the high solubility that shows the property of the fluid. This experiment is for SiC coating using H-PCS in supercritical CO 2 . It shows the clear difference that the penetration of H-PCS into the SiC between dip coating method and using the supercritical CO 2 If we can make a metal cladding with SiC composites as a protective layer, the use of the cladding will be very broad and diverse. Inherent safe nuclear fuels can be possible that can stand under severe accident conditions. SiC is known to be one of a few materials that maintain very corrosion-resistant properties under tough corrosive environments. The metal cladding with SiC composites as a protective layer will be a high-tech product that can be used in many applications including chemical, material, and nuclear engineering and etc

Tema 8. Principis físics dels semiconductors (Guia del tema)

OpenAIRE

Beléndez Vázquez, Augusto

2011-01-01

Guia del "Tema 8. Principis físics dels semiconductors" de l'assignatura "Fonaments Físics de l'Enginyeria I" de "Grau en Enginyeria en So i Imatge" impartit a l'Escola Politècnica Superior de la Universitat d'Alacant.

Diodes of nanocrystalline SiC on n-/n+-type epitaxial crystalline 6H-SiC

Science.gov (United States)

Zheng, Junding; Wei, Wensheng; Zhang, Chunxi; He, Mingchang; Li, Chang

2018-03-01

The diodes of nanocrystalline SiC on epitaxial crystalline (n-/n+)6H-SiC wafers were investigated, where the (n+)6H-SiC layer was treated as cathode. For the first unit, a heavily boron doped SiC film as anode was directly deposited by plasma enhanced chemical vapor deposition method on the wafer. As to the second one, an intrinsic SiC film was fabricated to insert between the wafer and the SiC anode. The third one included the SiC anode, an intrinsic SiC layer and a lightly phosphorus doped SiC film besides the wafer. Nanocrystallization in the yielded films was illustrated by means of X-ray diffraction, transmission electronic microscope and Raman spectrum respectively. Current vs. voltage traces of the obtained devices were checked to show as rectifying behaviors of semiconductor diodes, the conduction mechanisms were studied. Reverse recovery current waveforms were detected to analyze the recovery performance. The nanocrystalline SiC films in base region of the fabricated diodes are demonstrated as local regions for lifetime control of minority carriers to improve the reverse recovery properties.

Patient satisfaction after receiving dental treatment among patients ...

African Journals Online (AJOL)

Background: Patient satisfaction is one of the indicators of the quality of care. Therefore it is one of the tools for evaluating the quality of care. Aim: To determine patient satisfaction after receiving dental treatment among patients attending public dental clinics in Dar-Es-Salaam. Material and methods: Five public dental clinics ...

Effect of Ti and Si interlayer materials on the joining of SiC ceramics

Energy Technology Data Exchange (ETDEWEB)

Jung, Yang Il; Park, Jung Hwan; Kim, Hyun Gil; Park, Dong Jun; Park, Jeong Yong; Kim, Weon Ju [LWR Fuel Technology Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-08-15

SiC-based ceramic composites are currently being considered for use in fuel cladding tubes in light-water reactors. The joining of SiC ceramics in a hermetic seal is required for the development of ceramic-based fuel cladding tubes. In this study, SiC monoliths were diffusion bonded using a Ti foil interlayer and additional Si powder. In the joining process, a very low uniaxial pressure of ∼0.1 MPa was applied, so the process is applicable for joining thin-walled long tubes. The joining strength depended strongly on the type of SiC material. Reaction-bonded SiC (RB-SiC) showed a higher joining strength than sintered SiC because the diffusion reaction of Si was promoted in the former. The joining strength of sintered SiC was increased by the addition of Si at the Ti interlayer to play the role of the free Si in RB-SiC. The maximum joint strength obtained under torsional stress was ∼100 MPa. The joint interface consisted of TiSi{sub 2}, Ti{sub 3}SiC{sub 2}, and SiC phases formed by a diffusion reaction of Ti and Si.

Diagnosing dental caries in populations with different levels of dental fluorosis

DEFF Research Database (Denmark)

Nyvad, Bente; Machiulskiene, Vita; Fejerskov, Ole

2009-01-01

concentrations of 0.3 and 1.1 ppm (0.3 and 1.1 mg/l) fluoride, respectively, 150 children were clinically examined twice, 2 wk apart, for dental fluorosis, using the Thylstrup-Fejerskov index (TF index), and for dental caries using the Nyvad visual-tactile caries criteria. The prevalence of dental fluorosis......, a pronounced dental fluorosis background did not reduce the reliability of the caries recordings, which appeared to be slightly less reliable at very low levels of dental fluorosis.......The aim of this study was to assess the reliability of the Nyvad visual-tactile caries-diagnostic criteria when used among children who have been lifelong residents in areas with 'optimal' or low concentrations of fluoride in the drinking water. In each of two areas with drinking water fluoride...

Micromechanics of fiber pull-out and crack bridging in SCS-6 SiC- CVD SiC composite system at high-temperature

International Nuclear Information System (INIS)

El-Azab, A.; Ghoniem, N.M.

1993-01-01

A micro mechanical model is developed to study fiber pull-out and crack bridging in fiber reinforced SiC-SiC composites with time dependent thermal creep. By analyzing the creep data for monolithic CVD SiC (matrix) and the SCS-6 SiC fibers in the temperature range 900-1250 degrees C, it is found that the matrix creep rates can be ignored in comparison to those of fibers. Two important relationships are obtained: (1) a time dependent relation between the pull-out stress and the relative sliding distance between the fiber and matrix for the purpose of analyzing pull-out experiments, and (2) the relation between the bridging stress and the crack opening displacement to be used in studying the mechanics and stability of matrix crack bridged by fibers at high temperatures. The present analysis can also be applied to Nicalon-reinforced CVD SiC matrix system since the Nicalon fibers exhibit creep characteristics similar to those of the SCS-6 fibers

SiC Optically Modulated Field-Effect Transistor

Science.gov (United States)

Tabib-Azar, Massood

2009-01-01

An optically modulated field-effect transistor (OFET) based on a silicon carbide junction field-effect transistor (JFET) is under study as, potentially, a prototype of devices that could be useful for detecting ultraviolet light. The SiC OFET is an experimental device that is one of several devices, including commercial and experimental photodiodes, that were initially evaluated as detectors of ultraviolet light from combustion and that could be incorporated into SiC integrated circuits to be designed to function as combustion sensors. The ultraviolet-detection sensitivity of the photodiodes was found to be less than desired, such that it would be necessary to process their outputs using high-gain amplification circuitry. On the other hand, in principle, the function of the OFET could be characterized as a combination of detection and amplification. In effect, its sensitivity could be considerably greater than that of a photodiode, such that the need for amplification external to the photodetector could be reduced or eliminated. The experimental SiC OFET was made by processes similar to JFET-fabrication processes developed at Glenn Research Center. The gate of the OFET is very long, wide, and thin, relative to the gates of typical prior SiC JFETs. Unlike in prior SiC FETs, the gate is almost completely transparent to near-ultraviolet and visible light. More specifically: The OFET includes a p+ gate layer less than 1/4 m thick, through which photons can be transported efficiently to the p+/p body interface. The gate is relatively long and wide (about 0.5 by 0.5 mm), such that holes generated at the body interface form a depletion layer that modulates the conductivity of the channel between the drain and the source. The exact physical mechanism of modulation of conductivity is a subject of continuing research. It is known that injection of minority charge carriers (in this case, holes) at the interface exerts a strong effect on the channel, resulting in amplification

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.

Smelling Anxiety Chemosignals Impairs Clinical Performance of Dental Students.

Science.gov (United States)

Singh, Preet Bano; Young, Alix; Lind, Synnøve; Leegaard, Marie Cathinka; Capuozzo, Alessandra; Parma, Valentina

2018-05-15

Despite the fact that human body odors can transfer anxiety-related signals, the impact of such signals in real-life situations is scant. In this study, the effects of anxiety chemosignals on the performance of dental students operating on simulation units, wearing t-shirts imbued with human sweat and masked with eugenol were tested. Twenty-four 4th year dental students (17F) donated their body odors in two sessions (Anxiety and Rest). Twenty-four normosmic, sex- and age-matched test subjects who were3rd year dental students performed three dental procedures while smelling masked anxiety body odors, masked rest body odors or masker alone. The intensity and pleasantness ratings showed that the test subjects could not report perceptual differences between the odor conditions. When exposed to masked anxiety body odors the test subject's dental performance was significantly worse than when they were exposed to masked rest body odors and masker alone, indicating that their performance was modulated by exposure to the emotional tone of the odor. These findings call for a careful evaluation of the anxiety-inducing effects of body odors in performance-related tasks and provide the first ecological evaluation of human anxiety chemosignal communication.

SYLRAMICTM SiC fibers for CMC reinforcement

International Nuclear Information System (INIS)

Jones, Richard E.; Petrak, Dan; Rabe, Jim; Szweda, Andy

2000-01-01

Dow Corning researchers developed SYLRAMIC SiC fiber specifically for use in ceramic-matrix composite (CMC) components for use in turbine engine hot sections where excellent thermal stability, high strength and high thermal conductivity are required. This is a stoichiometric SiC fiber with a high degree of crystallinity, high tensile strength, high tensile modulus and good thermal conductivity. Owing to the small diameter, this textile-grade fiber can be woven into 2-D and 3-D structures for CMC fabrication. These properties are also of high interest to the nuclear community. Some initial studies have shown that SYLRAMIC fiber shows very good dimensional stability in a neutron flux environment, which offers further encouragement. This paper will review the properties of SYLRAMIC SiC fiber and then present the properties of polymer impregnation and pyrolysis (PIP) processed CMC made with this fiber at Dow Corning. While these composites may not be directly applicable to applications of interest to this audience, we believe that the properties shown will give good evidence that the fiber should be suitable for high temperature structural applications in the nuclear arena

Barriers and Drawbacks of the Assessment of Dental Fear, Dental Anxiety and Dental Phobia in Children: A Critical Literature Review.

Science.gov (United States)

Asl, Aminabadi Naser; Shokravi, Marzieh; Jamali, Zahra; Shirazi, Sajjad

Dental anxiety, fear and phobia have different etiology, response patterns, time courses, and intensities that justify a clear distinction between these constructs. Differentiation of dental anxiety, fear or phobia in practice is a critical prerequisite for developing and implementing effective treatment for children. The aim of this study was to investigate whether current researches in the pediatric dentistry appropriately discriminate the central construct of dental anxiety, fear and phobia. We also highlighted the specific methodological issues in the assessment of these issues in pediatric dentistry. A systematic search was conducted in Pubmed/medline and Scopus for articles which assessed dental anxiety, fear or phobia in children. 104 research papers were included in the review that had made a distinction between dental anxiety, fear and phobia and had not used them interchangeably. Only five studies used different clinical measures or cut-offs to discriminate between dental anxiety, fear and phobia. The dental literature appears unable to capture and also measure the multi-sided construct of dental anxiety, fear and phobia and, therefore, there was a tendency to use them interchangeably.

Clinical Fit of Partial Removable Dental Prostheses Based on Alginate or Polyvinyl Siloxane Impressions.

Science.gov (United States)

Fokkinga, Wietske A; Witter, Dick J; Bronkhorst, Ewald M; Creugers, Nico H

The aim of this study was to analyze the clinical fit of metal-frame partial removable dental prostheses (PRDPs) based on custom trays used with alginate or polyvinyl siloxane impression material. Fifth-year students of the Nijmegen Dental School made 25 correct impressions for 23 PRDPs for 21 patients using alginate, and 31 correct impressions for 30 PRDPs for 28 patients using polyvinyl siloxane. Clinical fit of the framework as a whole and of each retainer separately were evaluated by calibrated supervisors during framework try-in before (first evaluation) and after (second evaluation) possible adjustments (score 0 = poor fit, up to score 3 = good fit). Framework fit and fit of the denture base were evaluated at delivery (third evaluation). Finally, postinsertion sessions were evaluated and total number of sessions needed, sore spots, adjustments to the denture base, and reported food-impaction were recorded. No significant differences in clinical fit (of the framework as a whole, for the retainers, or for the denture base) were found between the groups in the three evaluation sessions. Differences were not found for postinsertion sessions with one exception: in the alginate group, four subjects reported food impaction, versus none in the polyvinyl siloxane group. Clinical fit of metal-frame PRDPs based on impressions with custom trays combined with alginate or polyvinyl siloxane was similar.

ToF-MEIS stopping measurements in thin SiC films

International Nuclear Information System (INIS)

Linnarsson, M.K.; Khartsev, S.; Primetzhofer, D.; Possnert, G.; Hallén, A.

2014-01-01

Electronic stopping in thin, amorphous, SiC films has been studied by time-of-flight medium energy ion scattering and conventional Rutherford backscattering spectrometry. Amorphous SiC films (8, 21 and 36 nm) were prepared by laser ablation using a single crystalline silicon carbide target. Two kinds of substrate films, one with a lower atomic mass (carbon) and one with higher atomic mass (iridium) compared to silicon has been used. Monte Carlo simulations have been used to evaluate electronic stopping from the shift in energy for the signal scattered from Ir with and without SiC. The two kinds of samples are used to illustrate the strength and challenges for ToF-MEIS compared to conventional RBS

Assessing the Effectiveness of a School-Based Dental Clinic on the Oral Health of Children Who Lack Access to Dental Care: A Program Evaluation

Science.gov (United States)

Carpino, Rachel; Walker, Mary P.; Liu, Ying; Simmer-Beck, Melanie

2017-01-01

This program evaluation examines the effectiveness of a school-based dental clinic. A repeated-measures design was used to longitudinally examine secondary data from participants (N = 293). Encounter intensity was developed to normalize data. Multivariate analysis of variance and Kruskal-Wallis test were used to investigate the effect of encounter…

Detecting the manipulation of digital clinical records in dental practice

International Nuclear Information System (INIS)

Díaz-Flores-García, V.; Labajo-González, E.; Santiago-Sáez, A.; Perea-Pérez, B.

2017-01-01

Introduction: Radiography provides many advantages in the diagnosis and management of dental conditions. However, dental X-ray images may be subject to manipulation with malicious intent using easily accessible computer software. Methods: In this study, we sought to evaluate a dentist's ability to identify a manipulated dental X-ray images, when compared with the original, using a variant of the methodology described by Visser and Kruger. Sixty-six dentists were invited to participate and evaluate 20 intraoral dental X-ray images, 10 originals and 10 modified, manipulated using Adobe Photoshop to simulate fillings, root canal treatments, etc. Results: Participating dentists were correct in identifying the manipulated image in 56% of cases, 6% higher than by chance and 10% more than in the study by Visser and Kruger. Conclusion: Malicious changes to dental X-ray images may go unnoticed even by experienced dentists. Professionals must be aware of the legal consequences of such changes. A system of detection/validation should be created for radiographic images. - Highlights: • Fraudulent manipulation of dental X-ray images creates a problem of legal security. • Dentists were able to identify manipulated images on 56% of all occasions. • 6% more than the probability of a person with no dental training. • 10% more than in the study by Visser and Kruger.

Preparation of biomorphic SiC ceramic by carbothermal reduction of oak wood charcoal

International Nuclear Information System (INIS)

Qian Junmin; Wang Jiping; Jin Zhihao

2004-01-01

Highly porous silicon carbide (SiC) ceramic with woodlike microstructure has been prepared at 1400-1600 deg. C by carbothermal reduction reaction of charcoal/silica composites in static argon atmosphere. These composites were fabricated by infiltrating silica sol into a porous biocarbon template from oak wood using a vacuum/pressure infiltration process. The morphology of resulting porous SiC ceramic, as well as the conversion mechanism of wood to porous SiC ceramic, have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Experimental results show that the biomorphic cellular morphology of oak wood charcoal is remained in the porous SiC ceramic with high precision that consists of β-SiC with traces of α-SiC. Silica in the charcoal/silica composites exists in the cellular pores in form of fibers and rods. The SiC strut material is formed by gas-solid reaction between SiO (g) and C (s) during the charcoal-to-ceramic conversion. The densification of SiC strut material may occur at moderate temperatures and holding time

Preparation of biomorphic SiC ceramic by carbothermal reduction of oak wood charcoal

Energy Technology Data Exchange (ETDEWEB)

Qian Junmin; Wang Jiping; Jin Zhihao

2004-04-25

Highly porous silicon carbide (SiC) ceramic with woodlike microstructure has been prepared at 1400-1600 deg. C by carbothermal reduction reaction of charcoal/silica composites in static argon atmosphere. These composites were fabricated by infiltrating silica sol into a porous biocarbon template from oak wood using a vacuum/pressure infiltration process. The morphology of resulting porous SiC ceramic, as well as the conversion mechanism of wood to porous SiC ceramic, have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Experimental results show that the biomorphic cellular morphology of oak wood charcoal is remained in the porous SiC ceramic with high precision that consists of {beta}-SiC with traces of {alpha}-SiC. Silica in the charcoal/silica composites exists in the cellular pores in form of fibers and rods. The SiC strut material is formed by gas-solid reaction between SiO (g) and C (s) during the charcoal-to-ceramic conversion. The densification of SiC strut material may occur at moderate temperatures and holding time.

Feasibility study on the application of carbide (ZrC, SiC) for VHTR

Energy Technology Data Exchange (ETDEWEB)

Park, Ji Yeon; Kim, Weon Ju; Jung, Choong Hwan; Ryu, Woo Seog; Kim, Si Hyeong; Jang, Moon Hee; Lee, Young Woo

2006-08-15

A feasibility study on the coating process of ZrC for the TRISO nuclear fuel and applications of SiC as high temperature materials for the core components has performed to develop the fabrication process for the advanced ZrC TRISO fuels and the high temperature structural components for VHTR, respectively. In the case of ZrC coating, studies were focused on the comparisons of the developed coating processes for screening of our technology, the evaluations of the reactions parameters for a ZrC deposition by the thermodynamic calculations and the preliminary coating experiments by the chloride process. With relate to SiC ceramics, our interesting items are as followings; an analysis of applications and specifications of the SiC components and collections of the SiC properties and establishments of data base. For these purposes, applications of SiC ceramics for the GEN-IV related components as well as the fusion reactor related ones were reviewed. Additionally, the on-going activities with related to the ZrC clad and the SiC composites discussed in the VHTR GIF-PMB, were reviewed to make the further research plans at the section 1 in chapter 3.

Microwave joining of SiC

Energy Technology Data Exchange (ETDEWEB)

Silberglitt, R.; Ahmad, I. [FM Technologies, Inc., Fairfax, VA (United States); Black, W.M. [George Mason Univ., Fairfax, VA (United States)] [and others

1995-05-01

The purpose of this work is to optimize the properties of SiC-SiC joints made using microwave energy. The current focus is on optimization of time-temperature profiles, production of SiC from chemical precursors, and design of new applicators for joining of long tubes.

Laser diagnostic and therapy of dental caries: the clinic point of view; Laser diagnostico e tratamento da carie dental: uma visao clinica

Energy Technology Data Exchange (ETDEWEB)

Paiva, Priscila Faria

2001-07-01

Dental caries's diagnosis is a major dentistry problem from the clinic point of view. The laser beam on the region of 655 nm induces the fluorescence of the compounds present in the hard tissue, quantifying differences between sound and carious enamel and dentine. Diagnodent (Kavo, Germany), showed to be effective regarding dental caries's diagnosis in the present research sampling. The Er:YAG laser (Kavo Key Laser 2, Germany) performed efficient cavity preparations in caries lesions of I and V class type, using up energies that ranged from 300 mJ to 350 mJ with 4 Hz repetition rate for the enamel; and from 250 mJ to 300 mJ with 4 Hz repetition rate for the dentine, and with 80 mJ with 6 Hz of repetition rate for laser conditioning. In the Er:YAG laser preparations no patient was anesthetized even when there were deeper cavities, and the maximum degree of pain ( which ranged from 0 to 10) was 4. In the control group with conventional high-speed drill two patients were anesthetized and the maximum degree of pain was 7. Restorations performed by conventional method of composite were equally satisfying both in caries groups of I and V class type and in the control group. The laser application in the operative dentistry office as a new method of diagnosis and dental preparations should be a good alternative to the use of the conventional dental drill. Nevertheless, dentistry practice has a lot to improve from technology progress, as well as new researches on laser dentistry are necessary in a long term. New types of lasers will come about and will increasingly improve the dental practice assistance and procedures quality. (author)

Laser diagnostic and therapy of dental caries: the clinic point of view; Laser diagnostico e tratamento da carie dental: uma visao clinica

Energy Technology Data Exchange (ETDEWEB)

Paiva, Priscila Faria

2001-07-01

Dental caries's diagnosis is a major dentistry problem from the clinic point of view. The laser beam on the region of 655 nm induces the fluorescence of the compounds present in the hard tissue, quantifying differences between sound and carious enamel and dentine. Diagnodent (Kavo, Germany), showed to be effective regarding dental caries's diagnosis in the present research sampling. The Er:YAG laser (Kavo Key Laser 2, Germany) performed efficient cavity preparations in caries lesions of I and V class type, using up energies that ranged from 300 mJ to 350 mJ with 4 Hz repetition rate for the enamel; and from 250 mJ to 300 mJ with 4 Hz repetition rate for the dentine, and with 80 mJ with 6 Hz of repetition rate for laser conditioning. In the Er:YAG laser preparations no patient was anesthetized even when there were deeper cavities, and the maximum degree of pain ( which ranged from 0 to 10) was 4. In the control group with conventional high-speed drill two patients were anesthetized and the maximum degree of pain was 7. Restorations performed by conventional method of composite were equally satisfying both in caries groups of I and V class type and in the control group. The laser application in the operative dentistry office as a new method of diagnosis and dental preparations should be a good alternative to the use of the conventional dental drill. Nevertheless, dentistry practice has a lot to improve from technology progress, as well as new researches on laser dentistry are necessary in a long term. New types of lasers will come about and will increasingly improve the dental practice assistance and procedures quality. (author)

Properties of SiC semiconductor detector of fast neutrons investigated using MCNPX code

International Nuclear Information System (INIS)

Sedlakova, K.; Sagatova, A.; Necas, V.; Zatko, B.

2013-01-01

The potential of silicon carbide (SiC) for use in semiconductor nuclear radiation detectors has been long recognized. The wide bandgap of SiC (3.25 eV for 4H-SiC polytype) compared to that for more conventionally used semiconductors, such as silicon (1.12 eV) and germanium (0.67 eV), makes SiC an attractive semiconductor for use in high dose rate and high ionization nuclear environments. The present work focused on the simulation of particle transport in SiC detectors of fast neutrons using statistical analysis of Monte Carlo radiation transport code MCNPX. Its possibilities in detector design and optimization are presented.(authors)

Determination of irradiation temperature using SiC temperature monitors

International Nuclear Information System (INIS)

Maruyama, Tadashi; Onose, Shoji

1999-01-01

This paper describes a method for detecting the change in length of SiC temperature monitors and a discussion is made on the relationship between irradiation temperature and the recovery in length of SiC temperature monitors. The SiC specimens were irradiated in the experimental fast reactor JOYO' at the irradiation temperatures around 417 to 645degC (design temperature). The change in length of irradiated specimens was detected using a dilatometer with SiO 2 glass push rod in an infrared image furnace. The temperature at which recovery in macroscopic length begins was obtained from the annealing intersection temperature. The results of measurements indicated that a difference between annealing intersection temperature and the design temperature sometimes reached well over ±100degC. A calibration method to obtain accurate irradiation temperature was presented and compared with the design temperature. (author)

Dental pain and dental treatment of young children attending the general dental service.

Science.gov (United States)

Milsom, K M; Tickle, M; Blinkhorn, A S

2002-03-09

The objective was to examine the relationship between dental pain (and its sequelae), and the extent of restorative care provided for primary molars, amongst children who regularly attend a general dental practitioner. A retrospective review of the clinical case notes of 677 children with caries who attended 50 general dental practitioners on a regular basis. Analyses were performed at the subject level. Logistic regression models were fitted for the dependent variables whether or not pain, a dental extraction for pain or sepsis and a course of antibiotics was recorded, after taking into account the proportion of carious teeth that were restored, the total number of carious teeth, the age caries was first recorded, gender and the clustering of the subjects within dental practices. Almost half of the children in the study (48%) were recorded as having at least one episode of pain. Total decay experience in the primary molars was a significant predictor of pain, extraction due to pain or sepsis and prescription of antibiotics. There was no significant association between the proportion of carious teeth restored and each of the three dependent variables. For those children who regularly attend their general dental practitioner and who have decay in their primary molars, dental pain is a common finding. Total decay experience in primary molars is the principal predictor of pain, extraction due to pain and the need for antibiotics, whilst the level of restorative care in the primary dentition is less important. In order to reduce the incidence of dental pain in young children, effective methods of preventing caries at the individual and public health levels need to be expanded.

"You Get Beautiful Teeth Down There": Racial/Ethnic Minority Older Adults' Perspectives on Care at Dental School Clinics.

Science.gov (United States)

Northridge, Mary E; Schenkel, Andrew B; Birenz, Shirley; Estrada, Ivette; Metcalf, Sara S; Wolff, Mark S

2017-11-01

To help eliminate reported racial/ethnic and socioeconomic inequities in oral health care, listening to the perspectives of racial/ethnic minority older adults on their experiences with dental school clinics is needed. The aim of this study was to examine the experiences of African American, Puerto Rican, and Dominican older adults who attend senior centers in upper Manhattan, New York City, regarding the care received at dental school clinics. Focus groups were conducted from 2013 to 2015 with 194 racial/ethnic minority men and women aged 50 years and older living in upper Manhattan. All of the 24 focus group sessions were digitally audiorecorded and transcribed for analysis. Groups conducted in Spanish were transcribed first in Spanish and then translated into English. Analysis of the transcripts was conducted using thematic content analysis. Seven subthemes were manifest in the data related to these adults' positive experiences with dental school clinics: excellent outcomes and dentists, painless and safe treatment, affordable care, honest and reputable, benefits of student training, accepting and helpful, and recommended by family and friends. Negative experiences centered around four subthemes: multiple visits required for treatment, loss of interpersonal communication due to use of technology, inconvenient location, and perceived stigma with Medicaid. This study provided novel evidence of the largely positive experiences with dental schools of racial/ethnic minority senior center attendees. Interventions targeted at the organization and provider level, including organizational motivation, resources, staff attributes, climate, and teamwork plus payment programs and services, insurance and affordability, and provider- and system-level supports, may improve health care processes and patient experiences of care.

Synthesis of nanostructured SiC using the pulsed laser deposition technique

International Nuclear Information System (INIS)

Zhang, H.X.; Feng, P.X.; Makarov, V.; Weiner, B.R.; Morell, G.

2009-01-01

We report the new results on the direct synthesis of nanostructured silicon carbide (SiC) materials using the pulsed laser deposition technique. Scanning electron microscopy images revealed that SiC nanoholes, nanosprouts, nanowires, and nanoneedles were obtained. The crystallographic structure, chemical composition, and bond structure of the nanoscale SiC materials were investigated using X-ray diffraction, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Raman scattering spectroscopy. The transverse optical mode and longitudinal optical mode in Raman spectra were found to become sharper as the substrate temperature was increased, while the material structure evolved from amorphous to crystalline

Fabrication of SiC nanopillars by inductively coupled SF6/O2 plasma etching

International Nuclear Information System (INIS)

Choi, J H; Bano, E; Latu-Romain, L; Dhalluin, F; Chevolleau, T; Baron, T

2012-01-01

In this paper, we demonstrate a top-down fabrication technique for nanometre scale silicon carbide (SiC) pillars using inductively coupled plasma etching. A set of experiments in SF 6 -based plasma was carried out in order to realize high aspect ratio SiC nanopillars. The etched SiC nanopillars using a small circular mask pattern (115 nm diameter) show high aspect ratio (7.4) with a height of 2.2 µm at an optimum bias voltage (300 V) and pressure (6 mTorr). Under the optimal etching conditions using a large circular mask pattern with 370 nm diameter, the obtained SiC nanopillars exhibit high anisotropy features (6.4) with a large etch depth (>7 µm). The etch characteristic of the SiC nanopillars under these conditions shows a high etch rate (550 nm min -1 ) and a high selectivity (over 60 for Ni). We also studied the etch profile of the SiC nanopillars and mask evolution over the etching time. As the mask pattern size shrinks in nanoscale, vertical and lateral mask erosion plays a crucial role in the etch profile of the SiC nanopillars. Long etching process makes the pillars appear with a hexagonal shape, coming from the crystallographic structure of α-SiC. It is found that the feature of pillars depends not only on the etching process parameters, but also on the crystallographic structure of the SiC phase. (paper)

Highly flexible and robust N-doped SiC nanoneedle field emitters

KAUST Repository

Chen, Shanliang

2015-01-23

Flexible field emission (FE) emitters, whose unique advantages are lightweight and conformable, promise to enable a wide range of technologies, such as roll-up flexible FE displays, e-papers and flexible light-emitting diodes. In this work, we demonstrate for the first time highly flexible SiC field emitters with low turn-on fields and excellent emission stabilities. n-Type SiC nanoneedles with ultra-sharp tips and tailored N-doping levels were synthesized via a catalyst-assisted pyrolysis process on carbon fabrics by controlling the gas mixture and cooling rate. The turn-on field, threshold field and current emission fluctuation of SiC nanoneedle emitters with an N-doping level of 7.58 at.% are 1.11 V μm-1, 1.55 V μm-1 and 8.1%, respectively, suggesting the best overall performance for such flexible field emitters. Furthermore, characterization of the FE properties under repeated bending cycles and different bending states reveal that the SiC field emitters are mechanically and electrically robust with unprecedentedly high flexibility and stabilities. These findings underscore the importance of concurrent morphology and composition controls in nanomaterial synthesis and establish SiC nanoneedles as the most promising candidate for flexible FE applications. © 2015 Nature Publishing Group All rights reserved.

Highly flexible and robust N-doped SiC nanoneedle field emitters

KAUST Repository

Chen, Shanliang; Ying, Pengzhan; Wang, Lin; Wei, Guodong; Gao, Fengmei; Zheng, Jinju; Shang, Minhui; Yang, Zuobao; Yang, Weiyou; Wu, Tao

2015-01-01

Flexible field emission (FE) emitters, whose unique advantages are lightweight and conformable, promise to enable a wide range of technologies, such as roll-up flexible FE displays, e-papers and flexible light-emitting diodes. In this work, we demonstrate for the first time highly flexible SiC field emitters with low turn-on fields and excellent emission stabilities. n-Type SiC nanoneedles with ultra-sharp tips and tailored N-doping levels were synthesized via a catalyst-assisted pyrolysis process on carbon fabrics by controlling the gas mixture and cooling rate. The turn-on field, threshold field and current emission fluctuation of SiC nanoneedle emitters with an N-doping level of 7.58 at.% are 1.11 V μm-1, 1.55 V μm-1 and 8.1%, respectively, suggesting the best overall performance for such flexible field emitters. Furthermore, characterization of the FE properties under repeated bending cycles and different bending states reveal that the SiC field emitters are mechanically and electrically robust with unprecedentedly high flexibility and stabilities. These findings underscore the importance of concurrent morphology and composition controls in nanomaterial synthesis and establish SiC nanoneedles as the most promising candidate for flexible FE applications. © 2015 Nature Publishing Group All rights reserved.

Effect of Carbon Concentration on the Sputtering of Carbon-Rich SiC Bombarded by Helium Ions

Directory of Open Access Journals (Sweden)

Xinghao Liang

2018-02-01

Full Text Available Silicon carbide (SiC is considered as an important material for nuclear engineering due to its excellent properties. Changing the carbon content in SiC can regulate and control its elastic and thermodynamic properties, but a simulation study of the effect of carbon content on the sputtering (caused by the helium ions of SiC is still lacking. In this work, we used the Monte-Carlo and molecular dynamics simulation methods to study the effects of carbon concentration, incidence energy, incident angle, and target temperature on the sputtering yield of SiC. The results show that the incident ions’ energy and angle have a significant effect on sputtering yield of SiC when the carbon concentration in SiC is around 62 at %, while the target temperature has a little effect on the sputtering yield of SiC. Our work might provide theoretical support for the experimental research and engineering application of carbon fiber-reinforced SiC that be used as the plasma-facing material in tokamak fusion reactors.

Phenotypic and genotypic characterization of clinically relevant bacteria isolated from dental waste and waste workers' hands, mucosas and coats.

Science.gov (United States)

Tagliaferri, T L; Vieira, C D; de Carvalho, M A R; Ladeira, L C D; Magalhães, P P; de Macêdo Farias, L; Dos Santos, S G

2017-10-01

Infectious wastes are potential sources of pathogenic micro-organisms, which may represent a risk to the professionals who manage them. In this study, we aimed to characterize the infectious bacteria present in dental waste and waste workers. The dental waste produced over 24 h was collected and waste workers were sampled by swabbing. Isolate resistance profiles were characterized by Vitek ® and PCR and biofilm formation by Congo Red agar, string test and microtitre assay. To assess similarity between the waste and the workers' samples, a random amplified polymorphic DNA test was used. Twenty-eight bacteria were identified as clinically relevant. The most frequent gene was bla TEM present in five Gram-negative micro-organisms, and one bla SHV in Klebsiella pneumoniae. All Pseudomonas aeruginosa were positive to extracellular polymeric substances formation, except one isolated from a worker. Klebsiella pneumoniae had negative results for the string test. Pseudomonas aeruginosa showed better adherence at 25°C after 48 h of incubation and K. pneumonia had the best biofilm formation at the same temperature, after 24 h. The similarity between P. aeruginosa recovered from dental waste and from workers was low, however, it is important to note that a pathogen was found on a worker's hands and that improvements in biosafety are required. Infectious dental waste can contain clinically relevant bacteria with important resistance and biofilm profiles. These micro-organisms could be transmitted to waste workers, other professionals and patients if the principles of biosafety measures are neglected. To our knowledge, no study has ever evaluated the microbial characterization and the potential contamination risk of dental infectious waste and waste handlers. The presence of clinically relevant bacteria in the hands and nasal mucosa of waste workers highlights the need for studies in this field to clarify the risk of these pathogens in dental healthcare services, and to

Quality assurance in digital dental radiography--justification and dose reduction in dental and maxillofacial radiology.

Science.gov (United States)

Hellstern, F; Geibel, M-A

2012-01-01

To evaluate the implementation of quality assurance requirements for digital dental radiography in routine clinical practice. The results should be discussed by radiation protection authorities in the context of the relevant legal requirements and current debates on radiation protection. Two hundred digital dental radiographs were randomly selected from the digital database of the Department of Dentistry's Dental and Maxillofacial Surgery Clinic, Ulm University, and evaluated for various aspects of image quality and compliance with radiographic documentation requirements. The dental films were prepared by different radiology assistants (RAs) using one of two digital intraoral radiographic systems: Sirona Heliodent DS, 60 kV, focal spot size: 0.7 mm (group A) or KaVo Gendex 765 DC, 65 kV, focal spot size: 0.4 mm (group B). Radiographic justification was documented in 70.5% of cases, and the radiographic findings in 76.5%. Both variables were documented in the patient records as well as in the software in 14% of cases. Clinical documentation of the required information (name of the responsible dentist and radiology assistant, date, patient name, department, tube voltage, tube current, exposure time, type of radiograph, film size, department and serial number of the dental radiograph) was 100% complete in all cases. Moreover, the department certified according to DIN ISO 9001:2008 specifications demonstrated complete clinical documentation of radiographic justifications and radiographic findings. The entire dentition was visible on 83% of the digital films. The visible area corresponded to the target region on 85.7% of the digital dental radiographs. Seven to 8.5% of the images were classified as "hypometric" or "hypermetric". This study indicates that improvements in radiology training and continuing education fordentists and dental staff performing x-ray examinations are needed to ensure consistent high quality of digital dental radiography. Implementation of

Effects of SiC and MgO on aluminabased ceramic foams filters

OpenAIRE

CAO Da-li; ZHOU Jing-yi; JIN Yong-ming

2007-01-01

Alumina-based foam ceramic filters were fabricated by using alumina, SiC, magnesia powder as major materials. It has been found that this ceramic filter has a uniform macrostructure for filtering molten metals. The influences of SiC and magnesia content, the sintering temperatures on ceramic properties were discussed. Aluminabased foam ceramic filters containing 2.2 mass% magnesia and 7.6 mass% SiC has a compressive strength of 1.36 MPa and a thermal shock resistance of 5 times. Its main phas...

Heteroepitaxy of zinc-blende SiC nano-dots on Si substrate by organometallic ion beam

International Nuclear Information System (INIS)

Matsumoto, T.; Kiuchi, M.; Sugimoto, S.; Goto, S.

2006-01-01

The self-assembled SiC nano-dots were fabricated on Si(111) substrate at low-temperatures using the organometallic ion beam deposition technique. The single precursor of methylsilicenium ions (SiCH 3 + ) with the energy of 100 eV was deposited on Si(111) substrate at 500, 550 and 600 deg. C. The characteristics of the self-assembled SiC nano-dots were analyzed by reflection high-energy electron diffraction (RHEED), Raman spectroscopy and atomic force microscope (AFM). The RHEED patterns showed that the crystal structure of the SiC nano-dots formed on Si(111) substrate was zinc-blende SiC (3C-SiC) and it was heteroepitaxy. The self-assembled SiC nano-dots were like a dome in shape, and their sizes were the length of 200-300 nm and the height of 10-15 nm. Despite the low-temperature of 500 deg. C as SiC crystallization the heteroepitaxial SiC nano-dots were fabricated on Si(111) substrate using the organometallic ion beam

Microstructure of SiC ceramics fabricated by pyrolysis of electron beam irradiated polycarbomethylsilane containing precursors

International Nuclear Information System (INIS)

Xu Yunshu; Tanaka, Shigeru

2003-01-01

A modified gel-casting method was developed to form the ceramics precursor matrix by using polycarbomehylsilane (PCMS) and SiC powder. The polymer precursor was mixed with SiC powder in toluene, and then the slurry samples were cast into designed shapes. The pre-ceramic samples were then irradiated by 2.0 MeV electron beam generated by a Cockcroft-Walton type accelerator in He gas flow to about 15 MGy. The cured samples were pyrolyzed and sintered into SiC ceramics at 1300degC in Ar gas. The modified gel-casting method leaves almost no internal stress in the pre-ceramic samples, and the electron beam curing not only diminished the amount of pyrolysis gaseous products but also enhanced the interface binding of the polymer converted SiC and the grains of SiC powder. Optical microscope, AFM and SEM detected no visible internal or surface cracks in the final SiC ceramics matrix. A maximum value of 122 MPa of flexural strength of the final SiC ceramics was achieved. (author)

Spherical nanostructured Si/C composite prepared by spray drying technique for lithium ion batteries anode

Energy Technology Data Exchange (ETDEWEB)

Chen Libao [Energy Science and Technology Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Xie Xiaohua [Energy Science and Technology Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Wang Baofeng [Department of Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Wang Ke [Energy Science and Technology Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Xie Jingying [Energy Science and Technology Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China) and Graduate School of Chinese Academy of Sciences, Beijing 100049 (China)]. E-mail: jyxie@mail.sim.ac.cn

2006-07-15

Spherical nanostructured Si/C composite was prepared by spray drying technique, followed by heat treatment, in which nanosized silicon and fine graphite particles were homogeneously embedded in carbon matrix pyrolyzed by phenol formaldehyde resin. Cyclic voltammetry tests showed two pairs of redox peaks corresponding to lithiation and delithiation of Si/C composite. The Si/C composite exhibited a reversible capacity of 635 mAh g{sup -1} and good cycle performance used in lithium ion batteries. To improve cycle performance of this Si/C composite further, the carbon-coated Si/C composite was synthesized by the second spray drying and heat treatment processing. The cycle performance of carbon-coated Si/C composite was improved significantly, which was attributed to the formation of stable SEI passivation layers on the outer surface of carbon shell which protected the bared silicon from exposing to electrolyte directly.

Spherical nanostructured Si/C composite prepared by spray drying technique for lithium ion batteries anode

International Nuclear Information System (INIS)

Chen Libao; Xie Xiaohua; Wang Baofeng; Wang Ke; Xie Jingying

2006-01-01

Spherical nanostructured Si/C composite was prepared by spray drying technique, followed by heat treatment, in which nanosized silicon and fine graphite particles were homogeneously embedded in carbon matrix pyrolyzed by phenol formaldehyde resin. Cyclic voltammetry tests showed two pairs of redox peaks corresponding to lithiation and delithiation of Si/C composite. The Si/C composite exhibited a reversible capacity of 635 mAh g -1 and good cycle performance used in lithium ion batteries. To improve cycle performance of this Si/C composite further, the carbon-coated Si/C composite was synthesized by the second spray drying and heat treatment processing. The cycle performance of carbon-coated Si/C composite was improved significantly, which was attributed to the formation of stable SEI passivation layers on the outer surface of carbon shell which protected the bared silicon from exposing to electrolyte directly

Acute dental pain II

DEFF Research Database (Denmark)

Jonasson, Peter; Kirkevang, Lise-Lotte; Rosen, Annika

2016-01-01

Acute dental pain most often occurs in relation to inflammatory conditions in the dental pulp or in the periradicular tissues surrounding a tooth, but it is not always easy to reach a diagnose and determine what treatment to perform. The anamnesis and the clinical examination provide valuable...

Ethics and the electronic health record in dental school clinics.

Science.gov (United States)

Cederberg, Robert A; Valenza, John A

2012-05-01

Electronic health records (EHRs) are a major development in the practice of dentistry, and dental schools and dental curricula have benefitted from this technology. Patient data entry, storage, retrieval, transmission, and archiving have been streamlined, and the potential for teledentistry and improvement in epidemiological research is beginning to be realized. However, maintaining patient health information in an electronic form has also changed the environment in dental education, setting up potential ethical dilemmas for students and faculty members. The purpose of this article is to explore some of the ethical issues related to EHRs, the advantages and concerns related to the use of computers in the dental operatory, the impact of the EHR on the doctor-patient relationship, the introduction of web-based EHRs, the link between technology and ethics, and potential solutions for the management of ethical concerns related to EHRs in dental schools.

Inhibition of odontogenic differentiation of human dental pulp cells by dental resin monomers

OpenAIRE

Kwon, Ji Hyun; Park, Hee Chul; Zhu, Tingting; Yang, Hyeong-Cheol

2015-01-01

Background Dental resin monomers that are leached from the resin matrix due to incomplete polymerization can affect the viability and various functions of oral tissues and cells. In this study, the effects of triethylene glycol dimethacrylate (TEGDMA) and 2-hydroxyethyl methacrylate (HEMA) on odontogenic differentiation of human dental pulp cells (HDPCs) were examined. To mimic clinical situations, dental pulp cells were treated with resin monomers for 24?h prior to the analysis of alkaline p...

Structural and electrical characterization of ion beam synthesized and n-doped SiC layers

Energy Technology Data Exchange (ETDEWEB)

Serre, C.; Perez-Rodriguez, A.; Romano-Rodriguez, A.; Morante, J.R. [Barcelona Univ. (Spain). Dept. Electronica; Panknin, D.; Koegler, R.; Skorupa, W. [Forschungszentrum Rossendorf, Dresden (Germany); Esteve, J.; Acero, M.C. [CSIC, Bellaterra (Spain). Centre Nacional de Microelectronica

2001-07-01

This work reports preliminary data on the ion beam synthesis of n-doped SiC layers. For this, two approaches have been studied: (i) doping by ion implantation (with N{sup +}) of ion beam synthesized SiC layers and (ii) ion beam synthesis of SiC in previously doped (with P) Si wafers. In the first case, the electrical data show a p-type overcompensation of the SiC layer in the range of temperatures between -50 C and 125 C. The structural (XRD) and in-depth (SIMS, Spreading Resistance) analysis of the samples suggest this overcompensation to be induced by p-type active defects related to the N{sup +} ion implantation damage, and therefore the need for further optimization their thermal processing. In contrast, the P-doped SiC layers always show n-type doping. This is also accompanied by a higher structural quality, being the spectral features of the layers similar to those from the not doped material. Electrical activation of P in the SiC lattice is about one order of magnitude lower than in Si. These data constitute, to our knowledge, the first results reported on the doping of ion beam synthesized SiC layers. (orig.)

A comparative study on electrical characteristics of 1-kV pnp and npn SiC bipolar junction transistors

Science.gov (United States)

Okuda, Takafumi; Kimoto, Tsunenobu; Suda, Jun

2018-04-01

We investigate the electrical characteristics of 1-kV pnp SiC bipolar junction transistors (BJTs) and compare them with those of npn SiC BJTs. The base resistance, current gain, and blocking capability are characterized. It is found that the base resistance of pnp SiC BJTs is two orders of magnitude lower than that of npn SiC BJTs. However, the obtained current gains are low below unity in pnp SiC BJTs, whereas npn SiC BJTs exhibit a current gain of 14 without surface passivation. The reason for the poor current gain of pnp SiC BJTs is discussed.