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Sample records for load bearing implants

  1. In vivo response of laser processed porous titanium implants for load-bearing implants

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    Bandyopadhyay, Amit; Shivaram, Anish; Tarafder, Solaiman; Sahasrabudhe, Himanshu; Banerjee, Dishary; Bose, Susmita

    2016-01-01

    Applications of porous metallic implants to enhance osseointegration of load-bearing implants are increasing. In this work, porous titanium implants, with 25 volume% porosity, were manufactured using Laser Engineered Net Shaping (LENS™) to measure the influence of porosity towards bone tissue integration in vivo. Surfaces of the LENS™ processed porous Ti implants were further modified with TiO2 nanotubes to improve cytocompatibility of these implants. We hypothesized that interconnected porosity created via additive manufacturing will enhance bone tissue integration in vivo. To test our hypothesis, in vivo experiments using a distal femur model of male Sprague-Dawley rats were performed for a period of 4 and 10 weeks. In vivo samples were characterized via micro-computed tomography (CT), histological imaging, scanning electron microscopy, and mechanical push-out tests. Our results indicate that porosity played an important role to establish early stage osseointegration forming strong interfacial bonding between the porous implants and the surrounding tissue, with or without surface modification, compared to dense Ti implants used as a control. PMID:27307009

  2. In Vivo Response of Laser Processed Porous Titanium Implants for Load-Bearing Implants.

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    Bandyopadhyay, Amit; Shivaram, Anish; Tarafder, Solaiman; Sahasrabudhe, Himanshu; Banerjee, Dishary; Bose, Susmita

    2017-01-01

    Applications of porous metallic implants to enhance osseointegration of load-bearing implants are increasing. In this work, porous titanium implants, with 25 vol.% porosity, were manufactured using Laser Engineered Net Shaping (LENS™) to measure the influence of porosity towards bone tissue integration in vivo. Surfaces of the LENS™ processed porous Ti implants were further modified with TiO 2 nanotubes to improve cytocompatibility of these implants. We hypothesized that interconnected porosity created via additive manufacturing will enhance bone tissue integration in vivo. To test our hypothesis, in vivo experiments using a distal femur model of male Sprague-Dawley rats were performed for a period of 4 and 10 weeks. In vivo samples were characterized via micro-computed tomography (CT), histological imaging, scanning electron microscopy, and mechanical push-out tests. Our results indicate that porosity played an important role to establish early stage osseointegration forming strong interfacial bonding between the porous implants and the surrounding tissue, with or without surface modification, compared to dense Ti implants used as a control.

  3. Load bearing and stiffness tailored NiTi implants produced by additive manufacturing: a simulation study

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    Rahmanian, Rasool; Shayesteh Moghaddam, Narges; Haberland, Christoph; Dean, David; Miller, Michael; Elahinia, Mohammad

    2014-03-01

    Common metals for stable long-term implants (e.g. stainless steel, Titanium and Titanium alloys) are much stiffer than spongy cancellous and even stiffer than cortical bone. When bone and implant are loaded this stiffness mismatch results in stress shielding and as a consequence, degradation of surrounding bony structure can lead to disassociation of the implant. Due to its lower stiffness and high reversible deformability, which is associated with the superelastic behavior, NiTi is an attractive biomaterial for load bearing implants. However, the stiffness of austenitic Nitinol is closer to that of bone but still too high. Additive manufacturing provides, in addition to the fabrication of patient specific implants, the ability to solve the stiffness mismatch by adding engineered porosity to the implant. This in turn allows for the design of different stiffness profiles in one implant tailored to the physiological load conditions. This work covers a fundamental approach to bring this vision to reality. At first modeling of the mechanical behavior of different scaffold designs are presented as a proof of concept of stiffness tailoring. Based on these results different Nitinol scaffolds can be produced by additive manufacturing.

  4. Additively manufactured custom load-bearing implantable devices: grounds for caution

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    Elisabetta M Zanetti

    2017-08-01

    Full Text Available Background Additive manufacturing technologies are being enthusiastically adopted by the orthopaedic community since they are providing new perspectives and new possibilities. First applications were finalised for educational purposes, pre-operative planning, and design of surgical guides; recent applications also encompass the production of implantable devices where 3D printing can bring substantial benefits such as customization, optimization, and manufacturing of very complex geometries. The conceptual smoothness of the whole process may lead to the idea that any medical practitioner can use a 3D printer and her/his imagination to design and produce novel products for personal or commercial use. Aims Outlining how the whole process presents more than one critical aspects, still demanding further research in order to allow a safe application of this technology for fully-custom design, in particular confining attention to orthopaedic/orthodontic prostheses defined as components responding mainly to a structural function. Methods Current knowledge of mechanical properties of additively manufactured components has been examined along with reasons why the behaviour of these components might differ from traditionally manufactured components. The structural information still missing for mechanical design is outlined. Results Mechanical properties of additively manufactured components are not completely known, and especially fatigue limit needs to be examined further. Conclusion At the present stage, with reference to load-bearing implants subjected to many loading cycles, the indication of custom-made additively manufactured medical devices should be restricted to the cases with no viable alternative.

  5. Surface modification and fatigue behavior of nitinol for load bearing implants

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    Bernard, Sheldon A.

    Musculoskeletal disorders are recognized amongst the most significant human health problems that exist today. Even though considerable research and development has gone towards understanding musculoskeletal disorders, there is still lack of bone replacement materials that are appropriate for restoring lost structures and functions, particularly for load-bearing applications. Many materials on the market today, such as titanium and stainless steel, suffer from significantly higher modulus than natural bone and low bioactivity leading to stress shielding and implant loosening over longer time use. Nitinol (NiTi) is an equiatomic intermetallic compound of nickel and titanium whose unique biomechanical and biological properties contributed to its increasing use as a biomaterial. An innovative method for creating dense and porous net shape NiTi alloy parts has been developed to improve biological properties while maintaining comparable or better mechanical properties than commercial materials that are currently in use. Laser engineered net shaping (LENS(TM)) and surface electrochemistry modification was used to create dense/porous samples and micro textured surfaces on NiTi parts, respectively. Porous implants are known to promote cell adhesion and have a low elastic modulus, a combination that can significantly increase the life of an implant. However, porosity can significantly reduce the fatigue life of an implant, and very little work has been reported on the fatigue behavior of bulk porous metals, specifically on porous nitinol alloy. High-cycle rotating bending and compression-compression fatigue behavior of porous NiTi fabricated using LENS(TM) were studied. In cyclic compression loading, plastic strain increased with increasing porosity and it was evident that maximum strain was achieved during the first 50000 cycles and remained constant throughout the remaining loading. No failures were observed due to loading up to 150% of the yield strength. When subjected

  6. Graphene-reinforced calcium silicate coatings for load-bearing implants.

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    Xie, Youtao; Li, Hongqing; Zhang, Chi; Gu, Xin; Zheng, Xuebin; Huang, Liping

    2014-04-01

    Owing to the superior mechanical properties and low coefficient of thermal expansion, graphene has been widely used in the reinforcement of ceramics. In the present study, various ratios of graphene (0.5 wt%, 1.5 wt% and 4 wt%) were reinforced into calcium silicate (CS) coatings for load-bearing implant surface modification. Surface characteristics of the graphene/calcium silicate (GC) composite coatings were characterized by scanning electron microscopy. Results show that the graphene plates (less than 4 wt% in the coatings) were embedded in the CS matrix homogeneously. The surfaces of the coatings showed a hierarchical hybrid nano-/microstructure, which is believed to be beneficial to the behaviors of the cell and early bone fixation of the implants. Wear resistance measured by a pin-on-disc model exhibited an obvious enhancement with the adoption of graphene plates. The weight losses of the GC coatings decreased with the increase of graphene content. However, too high graphene content (4 wt% or more) made the composite coatings porous and the wear resistance decreased dramatically. The weight loss was only 1.3 ± 0.2 mg for the GC coating containing 1.5 wt% graphene (denoted as GC1.5) with a load of 10 N and sliding distance of 500 m, while that of the pure CS coating reached up to 28.6 ± 0.5 mg. In vitro cytocompatibility of the GC1.5 coating was evaluated using a human marrow stem cell (hMSC) culture system. The proliferation and alkaline phosphatase, osteopontin and osteocalcin (OC) osteogenesis-related gene expression of the cells on the GC1.5 coating did not deteriorate with the adoption of graphene. Conversely, even better adhesion of the hMSCs was observed on the GC1.5 coating than on the pure CS coating. All of the results indicate that the GC1.5 coating is a good candidate for load-bearing implants.

  7. Load-Bearing Capacity and Retention of Newly Developed Micro-Locking Implant Prosthetic System: An In Vitro Pilot Study

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    Jae-Won Choi

    2018-04-01

    Full Text Available The aim of this study was to introduce the newly developed micro-locking implant prosthetic system and to evaluate the resulting its characteristics. To evaluate load-bearing capacity, 25 implants were divided into five groups: external-hexagon connection (EH, internal-octagon connection (IO, internal-hexagon connection (IH, one-body implant (OB, micro-locking implant system (ML. The maximum compressive load was measured using a universal testing machine (UTM according to the ISO 14801. Retention was evaluated in two experiments: (1 a tensile test of the structure modifications of the components (attachment and implant and (2 a tensile test after cyclic loading (total 5,000,000 cycles, 100 N, 2 Hz. The load-bearing capacity of the ML group was not significantly different from the other groups (p > 0.05. The number of balls in the attachment and the presence of a hexagonal receptacle did not show a significant correlation with retention (p > 0.05, but the shape of the retentive groove in the implant post had a statistically significant effect on retention (p < 0.05. On the other hand, the retention loss was observed during the initial 1,000,000 cycles, but an overall constant retention was maintained afterward. Various preclinical studies on this novel micro-locking implant prosthetic system should continue so that it can be applied in clinical practice.

  8. High strength, surface porous polyether-ether-ketone for load-bearing orthopaedic implants

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    Evans, Nathan T.; Torstrick, F. Brennan; Lee, Christopher S.D.; Dupont, Kenneth M.; Safranski, David L.; Chang, W. Allen; Macedo, Annie E.; Lin, Angela; Boothby, Jennifer M.; Whittingslow, Daniel C.; Carson, Robert A.; Guldberg, Robert E.; Gall, Ken

    2015-01-01

    Despite its widespread clinical use in load-bearing orthopaedic implants, polyether-ether-ketone (PEEK) is often associated with poor osseointegration. In this study, a surface porous PEEK material (PEEK-SP) was created using a melt extrusion technique. The porous layer thickness was 399.6±63.3 µm and possessed a mean pore size of 279.9±31.6 µm, strut spacing of 186.8±55.5 µm, porosity of 67.3±3.1%, and interconnectivity of 99.9±0.1%. Monotonic tensile tests showed that PEEK-SP preserved 73.9% of the strength (71.06±2.17 MPa) and 73.4% of the elastic modulus (2.45±0.31 GPa) of as-received, injection molded PEEK. PEEK-SP further demonstrated a fatigue strength of 60.0 MPa at one million cycles, preserving 73.4% of the fatigue resistance of injection molded PEEK. Interfacial shear testing showed the pore layer shear strength to be 23.96±2.26 MPa. An osseointegration model in the rat revealed substantial bone formation within the pore layer at 6 and 12 weeks via µCT and histological evaluation. Ingrown bone was more closely apposed to the pore wall and fibrous tissue growth was reduced in PEEK-SP when compared to non-porous PEEK controls. These results indicate that PEEK-SP could provide improved osseointegration while maintaining the structural integrity necessary for load-bearing orthopaedic applications. PMID:25463499

  9. High-strength, surface-porous polyether-ether-ketone for load-bearing orthopedic implants.

    Science.gov (United States)

    Evans, Nathan T; Torstrick, F Brennan; Lee, Christopher S D; Dupont, Kenneth M; Safranski, David L; Chang, W Allen; Macedo, Annie E; Lin, Angela S P; Boothby, Jennifer M; Whittingslow, Daniel C; Carson, Robert A; Guldberg, Robert E; Gall, Ken

    2015-02-01

    Despite its widespread clinical use in load-bearing orthopedic implants, polyether-ether-ketone (PEEK) is often associated with poor osseointegration. In this study, a surface-porous PEEK material (PEEK-SP) was created using a melt extrusion technique. The porous layer was 399.6±63.3 μm thick and possessed a mean pore size of 279.9±31.6 μm, strut spacing of 186.8±55.5 μm, porosity of 67.3±3.1% and interconnectivity of 99.9±0.1%. Monotonic tensile tests showed that PEEK-SP preserved 73.9% of the strength (71.06±2.17 MPa) and 73.4% of the elastic modulus (2.45±0.31 GPa) of as-received, injection-molded PEEK. PEEK-SP further demonstrated a fatigue strength of 60.0 MPa at one million cycles, preserving 73.4% of the fatigue resistance of injection-molded PEEK. Interfacial shear testing showed the pore layer shear strength to be 23.96±2.26 MPa. An osseointegration model in the rat revealed substantial bone formation within the pore layer at 6 and 12 weeks via microcomputed tomography and histological evaluation. Ingrown bone was more closely apposed to the pore wall and fibrous tissue growth was reduced in PEEK-SP when compared to non-porous PEEK controls. These results indicate that PEEK-SP could provide improved osseointegration while maintaining the structural integrity necessary for load-bearing orthopedic applications. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  10. Adhesive strength of bone-implant interfaces and in-vivo degradation of PHB composites for load-bearing applications.

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    Meischel, M; Eichler, J; Martinelli, E; Karr, U; Weigel, J; Schmöller, G; Tschegg, E K; Fischerauer, S; Weinberg, A M; Stanzl-Tschegg, S E

    2016-01-01

    Aim of this study was to evaluate the response of bone to novel biodegradable polymeric composite implants in the femora of growing rats. Longitudinal observation of bone reaction at the implant site (BV/TV) as well as resorption of the implanted pins were monitored using in vivo micro-focus computed tomography (µCT). After 12, 24 and 36 weeks femora containing the implants were explanted, scanned with high resolution ex vivo µCT, and the surface roughness of the implants was measured to conclude on the ingrowth capability for bone tissue. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to observe changes on the surface of Polyhydroxybutyrate (PHB) during degradation and cell ingrowth. Four different composites with zirconium dioxide (ZrO2) and Herafill(®) were compared. After 36 weeks in vivo, none of the implants did show significant degradation. The PHB composite with ZrO2 and a high percentage (30%) of Herafill® as well as the Mg-alloy WZ21 showed the highest values of bone accumulation (increased BV/TV) around the implant. The lowest value was measured in PHB with 3% ZrO2 containing no Herafill®. Roughness measurements as well as EDX and SEM imaging could not reveal any changes on the PHB composites׳ surfaces. Biomechanical parameters, such as the adhesion strength between bone and implant were determined by measuring the shear strength as well as push-out energy of the bone-implant interface. The results showed that improvement of these mechanical properties of the studied PHBs P3Z, P3Z10H and P3Z30H is necessary in order to obtain appropriate load-bearing material. The moduli of elasticity, tensile strength and strain properties of the PHB composites are close to that of bone and thus promising. Compared to clinically used PLGA, PGA and PLA materials, their additional benefit is an unchanged local pH value during degradation, which makes them well tolerated by cells and immune system. They might be used

  11. Influence of artificial aging on the load-bearing capability of straight or angulated zirconia abutments in implant/tooth-supported fixed partial dentures.

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    Nothdurft, Frank P; Doppler, Klaus E; Erdelt, Kurt J; Knauber, Andreas W; Pospiech, Peter R

    2010-01-01

    The aim of the study was to evaluate the influence of artificial aging on the fracture behavior of straight and angulated zirconia implant abutments used in ZirDesign (Astra Tech) implant/tooth-supported fixed partial dentures (FPDs) in the maxilla. Four different test groups (n = 8) representing anterior implant/tooth-supported FPDs were prepared. Groups 1 and 2 simulated a clinical situation with an ideal implant position (maxillary left central incisor) from a prosthetic point of view, which allowed for the use of a straight, prefabricated zirconia abutment. Groups 3 and 4 simulated a situation with a compromised implant position that required an angulated (20-degree) abutment. OsseoSpeed implants (4.5 3 13 mm, Astra Tech) as well as metal tooth analogs (maxillary right lateral incisor) with simulated periodontal mobility were mounted in polymethyl methacrylate. The FPDs (chromium-cobalt alloy) were cemented with glass ionomer. Groups 2 and 4 were thermomechanically loaded and subjected to static loading until failure. Statistical analysis of force data at the fracture site was performed using nonparametric tests. All samples survived thermomechanical loading. Artificial aging did not lead to a significant decrease in load-bearing capacity in either the straight abutments or the angulated abutments. The restorations that used angulated abutments exhibited higher fracture loads than the restorations with straight abutments (group 1: 209.13 ± 39.11 N; group 2: 233.63 ± 30.68 N; group 3: 324.62 ± 108.07 N; group 4: 361.75 ± 73.82 N). This difference in load-bearing performance was statistically significant, both with and without artificial aging. All abutment fractures occurred below the implant shoulder. Compensation for angulated implant positions with an angulated zirconia abutment is possible without reducing the load-bearing capacity of implant/tooth-supported anterior FPDs.

  12. Load responsive hydrodynamic bearing

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    Kalsi, Manmohan S.; Somogyi, Dezso; Dietle, Lannie L.

    2002-01-01

    A load responsive hydrodynamic bearing is provided in the form of a thrust bearing or journal bearing for supporting, guiding and lubricating a relatively rotatable member to minimize wear thereof responsive to relative rotation under severe load. In the space between spaced relatively rotatable members and in the presence of a liquid or grease lubricant, one or more continuous ring shaped integral generally circular bearing bodies each define at least one dynamic surface and a plurality of support regions. Each of the support regions defines a static surface which is oriented in generally opposed relation with the dynamic surface for contact with one of the relatively rotatable members. A plurality of flexing regions are defined by the generally circular body of the bearing and are integral with and located between adjacent support regions. Each of the flexing regions has a first beam-like element being connected by an integral flexible hinge with one of the support regions and a second beam-like element having an integral flexible hinge connection with an adjacent support region. A least one local weakening geometry of the flexing region is located intermediate the first and second beam-like elements. In response to application of load from one of the relatively rotatable elements to the bearing, the beam-like elements and the local weakening geometry become flexed, causing the dynamic surface to deform and establish a hydrodynamic geometry for wedging lubricant into the dynamic interface.

  13. Hybrid coating on a magnesium alloy for minimizing the localized degradation for load-bearing biodegradable mini-implant applications

    Energy Technology Data Exchange (ETDEWEB)

    Kannan, M. Bobby, E-mail: bobby.mathan@jcu.edu.au; Liyanaarachchi, S.

    2013-10-01

    The effect of a hybrid coating, calcium phosphate (CaP) + polylactic acid (PLA), on a magnesium alloy on its in vitro degradation (general and localized) behaviour was studied for potential load-bearing biodegradable mini-implant applications. CaP was coated on a magnesium alloy, AZ91, using an electrochemical deposition method. A spin coating method was used to coat PLA on the CaP coated alloy. In vitro degradation performance of the alloy with hybrid coating was evaluated using electrochemical impedance spectroscopy (EIS) in simulated body fluid (SBF). The EIS results showed that the hybrid coating enhanced the degradation resistance of the alloy by more than two-order of magnitude as compared to the bare alloy and one-order of magnitude higher than that of the CaP coated alloy, after 1 h exposure in simulated body fluid (SBF). Long-term (48 h) EIS results also confirmed that the hybrid coating performed better than the bare alloy and the CaP coated alloy. Importantly, the hybrid coating improved the localized degradation resistance of the alloy significantly, which is critical for better in service mechanical integrity. - Highlights: • A hybrid coating (CaP + PLA) was applied on a magnesium-based alloy. • The hybrid coating enhanced the in vitro degradation resistance of the alloy. • Localized degradation resistance was also improved by the hybrid coating.

  14. Hybrid coating on a magnesium alloy for minimizing the localized degradation for load-bearing biodegradable mini-implant applications

    International Nuclear Information System (INIS)

    Kannan, M. Bobby; Liyanaarachchi, S.

    2013-01-01

    The effect of a hybrid coating, calcium phosphate (CaP) + polylactic acid (PLA), on a magnesium alloy on its in vitro degradation (general and localized) behaviour was studied for potential load-bearing biodegradable mini-implant applications. CaP was coated on a magnesium alloy, AZ91, using an electrochemical deposition method. A spin coating method was used to coat PLA on the CaP coated alloy. In vitro degradation performance of the alloy with hybrid coating was evaluated using electrochemical impedance spectroscopy (EIS) in simulated body fluid (SBF). The EIS results showed that the hybrid coating enhanced the degradation resistance of the alloy by more than two-order of magnitude as compared to the bare alloy and one-order of magnitude higher than that of the CaP coated alloy, after 1 h exposure in simulated body fluid (SBF). Long-term (48 h) EIS results also confirmed that the hybrid coating performed better than the bare alloy and the CaP coated alloy. Importantly, the hybrid coating improved the localized degradation resistance of the alloy significantly, which is critical for better in service mechanical integrity. - Highlights: • A hybrid coating (CaP + PLA) was applied on a magnesium-based alloy. • The hybrid coating enhanced the in vitro degradation resistance of the alloy. • Localized degradation resistance was also improved by the hybrid coating

  15. Degradation of Zr-based bulk metallic glasses used in load-bearing implants: A tribocorrosion appraisal.

    Science.gov (United States)

    Zhao, Guo-Hua; Aune, Ragnhild E; Mao, Huahai; Espallargas, Nuria

    2016-07-01

    Owing to the amorphous structure, Bulk Metallic Glasses (BMGs) have been demonstrating attractive properties for potential biomedical applications. In the present work, the degradation mechanisms of Zr-based BMGs with nominal compositions Zr55Cu30Ni5Al10 and Zr65Cu18Ni7Al10 as potential load-bearing implant material were investigated in a tribocorrosion environment. The composition-dependent micro-mechanical and tribological properties of the two BMGs were evaluated prior to the tribocorrosion tests. The sample Zr65-BMG with a higher Zr content exhibited increased plasticity but relatively reduced wear resistance during the ball-on-disc tests. Both BMGs experienced abrasive wear after the dry wear test under the load of 2N. The cross-sectional subsurface structure of the wear track was examined by Focused Ion Beam (FIB). The electrochemical properties of the BMGs in simulated body fluid were evaluated by means of potentiodynamic polarization and X-ray Photoelectron Spectroscopy (XPS). The spontaneous passivation of Zr-based BMGs in Phosphate Buffer Saline solution was mainly attributed to the highly concentrated zirconium cation (Zr(4+)) in the passive film. The tribocorrosion performance of the BMGs was investigated using a reciprocating tribometer equipped with an electrochemical cell. The more passive nature of the Zr65-BMG had consequently a negative influence on its tribocorrosion resistance, which induced the wear-accelerated corrosion and eventually speeded-up the degradation process. It has been revealed the galvanic coupling was established between the depassivated wear track and the surrounding passive area, which is the main degradation mechanism for the passive Zr65-BMG subjected to the tribocorrosion environment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Mechanical characterization of structurally porous biomaterials built via additive manufacturing: experiments, predictive models, and design maps for load-bearing bone replacement implants.

    Science.gov (United States)

    Melancon, D; Bagheri, Z S; Johnston, R B; Liu, L; Tanzer, M; Pasini, D

    2017-11-01

    Porous biomaterials can be additively manufactured with micro-architecture tailored to satisfy the stringent mechano-biological requirements imposed by bone replacement implants. In a previous investigation, we introduced structurally porous biomaterials, featuring strength five times stronger than commercially available porous materials, and confirmed their bone ingrowth capability in an in vivo canine model. While encouraging, the manufactured biomaterials showed geometric mismatches between their internal porous architecture and that of its as-designed counterpart, as well as discrepancies between predicted and tested mechanical properties, issues not fully elucidated. In this work, we propose a systematic approach integrating computed tomography, mechanical testing, and statistical analysis of geometric imperfections to generate statistical based numerical models of high-strength additively manufactured porous biomaterials. The method is used to develop morphology and mechanical maps that illustrate the role played by pore size, porosity, strut thickness, and topology on the relations governing their elastic modulus and compressive yield strength. Overall, there are mismatches between the mechanical properties of ideal-geometry models and as-manufactured porous biomaterials with average errors of 49% and 41% respectively for compressive elastic modulus and yield strength. The proposed methodology gives more accurate predictions for the compressive stiffness and the compressive strength properties with a reduction of the average error to 11% and 7.6%. The implications of the results and the methodology here introduced are discussed in the relevant biomechanical and clinical context, with insight that highlights promises and limitations of additively manufactured porous biomaterials for load-bearing bone replacement implants. In this work, we perform mechanical characterization of load-bearing porous biomaterials for bone replacement over their entire design

  17. Low elastic modulus Ti-Ta alloys for load-bearing permanent implants: enhancing the biodegradation resistance by electrochemical surface engineering.

    Science.gov (United States)

    Kesteven, Jazmin; Kannan, M Bobby; Walter, Rhys; Khakbaz, Hadis; Choe, Han-Choel

    2015-01-01

    In this study, the in vitro degradation behaviour of titanium-tantalum (Ti-Ta) alloys (10-30 wt.% Ta) was investigated and compared with conventional implant materials, i.e., commercially pure titanium (Cp-Ti) and titanium-aluminium-vanadium (Ti6Al4V) alloy. Among the three Ti-Ta alloys studied, the Ti20Ta (6.3×10(-4) mm/y) exhibited the lowest degradation rate, followed by Ti30Ta (1.2×10(-3) mm/y) and Ti10Ta (1.4×10(-3) mm/y). All the Ti-Ta alloys exhibited lower degradation rate than that of Cp-Ti (1.8×10(-3) mm/y), which suggests that Ta addition to Ti is beneficial. As compared to Ti6Al4V alloy (8.1×10(-4) mm/y), the degradation rate of Ti20Ta alloy was lower by ~22%. However, the Ti30Ta alloy, which has closer elastic modulus to that of natural bone, showed ~48% higher degradation rate than that of Ti6Al4V alloy. Hence, to improve the degradation performance of Ti30Ta alloy, an intermediate thin porous layer was formed electrochemically on the alloy followed by calcium phosphate (CaP) electrodeposition. The coated Ti30Ta alloy (3.8×10(-3) mm/y) showed ~53% lower degradation rate than that of Ti6Al4V alloy. Thus, the study suggests that CaP coated Ti30Ta alloy can be a viable material for load-bearing permanent implants. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Enhanced antitumor efficacy of poly(D,L-lactide-co-glycolide-based methotrexate-loaded implants on sarcoma 180 tumor-bearing mice

    Directory of Open Access Journals (Sweden)

    Gao L

    2017-10-01

    Full Text Available Li Gao,1,2 Lunyang Xia,3 Ruhui Zhang,1 Dandan Duan,3 Xiuxiu Liu,2 Jianjian Xu,2 Lan Luo1 1State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, 2School of Biological and Medical Engineering, Hefei University of Technology, Hefei, 3Laboratory of Pharmaceutical Research, Anhui Zhongren Science and Technology Co., Ltd., Hefei, People’s Republic of China Purpose: Methotrexate is widely used in chemotherapy for a variety of malignancies. However, severe toxicity, poor pharmacokinetics, and narrow safety margin of methotrexate limit its clinical application. The aim of this study was to develop sustained-release methotrexate-loaded implants and evaluate antitumor activity of the implants after intratumoral implantation. Materials and methods: We prepared the implants containing methotrexate, poly(D,L-lactide-co-glycolide, and polyethylene glycol 4000 with the melt-molding technique. The implants were characterized with regards to drug content, morphology, in vitro, and in vivo release profiles. Differential scanning calorimetry (DSC and Fourier transform infrared spectroscopy (FTIR were carried out to investigate the physicochemical properties of the implants. Furthermore, the antitumor activity of the implants was tested in a sarcoma 180 mouse model. Results: The implants were prepared as solid rods. Scanning electron microscopy images showed a smooth surface of the implant, suggesting that methotrexate was homogeneously dispersed in the polymeric matrix. The results of DSC and FTIR indicated that no significant interaction between methotrexate and the polymer was observed in the implants. Both in vitro and in vivo release profiles of the implants were characterized by burst release followed by sustained release of methotrexate. Intratumoral implantation of methotrexate-loaded implants could efficiently delay tumor growth. Moreover, an increase in the dose of implants led to a higher tumor

  19. Low elastic modulus Ti–Ta alloys for load-bearing permanent implants: Enhancing the biodegradation resistance by electrochemical surface engineering

    Energy Technology Data Exchange (ETDEWEB)

    Kesteven, Jazmin [Biomaterials and Engineering Materials (BEM) Laboratory, School of Engineering and Physical Sciences, James Cook University, Townsville, Queensland 4811 (Australia); Kannan, M. Bobby, E-mail: bobby.mathan@jcu.edu.au [Biomaterials and Engineering Materials (BEM) Laboratory, School of Engineering and Physical Sciences, James Cook University, Townsville, Queensland 4811 (Australia); Walter, Rhys; Khakbaz, Hadis [Biomaterials and Engineering Materials (BEM) Laboratory, School of Engineering and Physical Sciences, James Cook University, Townsville, Queensland 4811 (Australia); Choe, Han-Choel [Department of Dental Materials, Chosun University, Gwangju 501-759 (Korea, Republic of)

    2015-01-01

    In this study, the in vitro degradation behaviour of titanium–tantalum (Ti–Ta) alloys (10–30 wt.% Ta) was investigated and compared with conventional implant materials, i.e., commercially pure titanium (Cp-Ti) and titanium–aluminium–vanadium (Ti6Al4V) alloy. Among the three Ti–Ta alloys studied, the Ti20Ta (6.3 × 10{sup −4} mm/y) exhibited the lowest degradation rate, followed by Ti30Ta (1.2 × 10{sup −3} mm/y) and Ti10Ta (1.4 × 10{sup −3} mm/y). All the Ti–Ta alloys exhibited lower degradation rate than that of Cp-Ti (1.8 × 10{sup −3} mm/y), which suggests that Ta addition to Ti is beneficial. As compared to Ti6Al4V alloy (8.1 × 10{sup −4} mm/y), the degradation rate of Ti20Ta alloy was lower by ∼ 22%. However, the Ti30Ta alloy, which has closer elastic modulus to that of natural bone, showed ∼ 48% higher degradation rate than that of Ti6Al4V alloy. Hence, to improve the degradation performance of Ti30Ta alloy, an intermediate thin porous layer was formed electrochemically on the alloy followed by calcium phosphate (CaP) electrodeposition. The coated Ti30Ta alloy (3.8 × 10{sup −3} mm/y) showed ∼ 53% lower degradation rate than that of Ti6Al4V alloy. Thus, the study suggests that CaP coated Ti30Ta alloy can be a viable material for load-bearing permanent implants. - Highlights: • In vitro degradation of titanium–tantalum (Ti–Ta) alloys was studied. • Ta addition to Ti is beneficial for better degradation resistance. • Ti–Ta alloys perform better than commercially pure Ti. • Calcium phosphate coated Ti–Ta alloy is superior to Ti6Al4V alloy.

  20. Load Bearing Equipment for Bone and Muscle

    Science.gov (United States)

    Shackelford, Linda; Griffith, Bryan

    2015-01-01

    Resistance exercise on ISS has proven effective in maintaining bone mineral density and muscle mass. Exploration missions require exercise with similar high loads using equipment with less mass and volume and greater safety and reliability than resistance exercise equipment used on ISS (iRED, ARED, FWED). Load Bearing Equipment (LBE) uses each exercising person to create and control the load to the partner.

  1. LIGHT-WEIGHT LOAD-BEARING STRUCTURE

    DEFF Research Database (Denmark)

    2009-01-01

    The invention relates to a light-weight load-bearing structure (1) with optimized compression zone (2), where along one or more compression zones (2) in the structure (1) to be cast a core (3) of strong concrete is provided, which core (3) is surrounded by concrete of less strength (4) compared...... to the core (3) of strong concrete. The invention also relates to a method of casting of light-weight load-bearing structures (1) with optimized compression zone (2) where one or more channels, grooves, ducts, pipes and/or hoses (5) formed in the load-bearing structure (1) serves as moulds for moulding one...... or more cores (3) of strong concrete in the light-weight load-bearing structure (1)....

  2. Shaft Center Orbit in Dynamically Loaded Bearings

    DEFF Research Database (Denmark)

    Klit, Peder

    2005-01-01

    The aim of this work is to demonstrate how to utilize the bearings damping coe±cients to estimate the orbit for a dynamically loaded journal bearing. The classical method for this analysis was developed by Booker in 1965 [1]and described further in 1972 [2]. Several authors have re¯ned this metho...

  3. Load-Bearing Capacity of Roof Trusses

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Damkilde, Lars; Munch-Andersen, J.

    2004-01-01

    systems such as roof trusses are established and statistical characteristics of the load bearing capacity are determined. The results show that there is a significant increase in the characteristic (nominal) value and a reduction in the coefficient of variation (COV) for typical loads such as permanent...

  4. Static Load Distribution in Ball Bearings

    Science.gov (United States)

    Ricci, Mario

    2010-01-01

    A numerical procedure for computing the internal loading distribution in statically loaded, single-row, angular-contact ball bearings when subjected to a known combined radial and thrust load is presented. The combined radial and thrust load must be applied in order to avoid tilting between inner and outer rings. The numerical procedure requires the iterative solution of Z + 2 simultaneous nonlinear equations - where Z is the number of the balls - to yield an exact solution for axial and radial deflections, and contact angles. Numerical results for a 218 angular-contact ball bearing have been compared with those from the literature and show significant differences in the magnitudes of the ball loads, contact angles, and the extent of the loading zone.

  5. Wound healing in immediately loaded implants.

    Science.gov (United States)

    Romanos, Georgios E

    2015-06-01

    The orthopedic field has accumulated ample evidence that bone formation is related to functional loading and in general to physical activity. However, despite evidence that immediately loaded implants can be predictably successful, many clinicians still use the classical (delayed loading) treatment protocol. This paper examines the effects of loading on dental implants and discusses the advantages of immediate loading. The role of loading on augmented alveolar ridges is also addressed and provides evidence that early bone resorption may be controlled when bone is functionally loaded. Similar data are emerging for advanced augmentation techniques in order to control crestal bone loss. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  6. Early Loaded Single Implant Reinforced Mandibular Overdenture

    Directory of Open Access Journals (Sweden)

    K. Nischal

    2016-01-01

    Full Text Available Rehabilitating atrophied mandible with two-implant supported denture is a common treatment modality for implant retained removable overdenture in mandible. This paper aims to design a treatment modality where single implant reinforced overdenture is fabricated for a severely atrophied mandibular ridge with early loading protocol. Results of studies have shown that a single implant mandibular overdenture significantly increases the satisfaction and quality of life of patients with edentulism. Midline fracture of the prosthesis is the most common complication related to single implant and two-implant retained mandibular overdentures. To manage such complication, a thin metal mesh is used to reinforce the overdenture and also to make the prostheses lighter and cost effective as compared to conventional cast metal framework.

  7. Fatigue life of drilling bit bearings under arbitrary random loads

    Energy Technology Data Exchange (ETDEWEB)

    Talimi, M.; Farshidi, R. [Calgary Univ., AB (Canada)

    2009-07-01

    A fatigue analysis was conducted in order to estimate the bearing life of a roller cone rock bit under arbitrary random loads. The aim of the study was to reduce bearing failures that can interrupt well operations. Fatigue was considered as the main reason for bearing failure. The expected value of cumulative fatigue damage was used to estimate bearing life. An equation was used to express the relation between bearing life and bearing load when the bearing was subjected to a steady load and constant speed. The Palmgren-Miner hypothesis was used to determine the ultimate tensile strength of the material. The rain flow counting principle was used to determine distinct amplitude cycles. Hertzian equations were used to determine maximum stress loads. Fourier series were used to obtain simple harmonic functions for estimating stress-life relations. It was concluded that the method can be used during the well planning phase to prevent bearing failures. 6 refs.

  8. Diclofenac Sodium Loaded Multicomponent Implant

    Science.gov (United States)

    Nikkola, Lila; Viitanen, Petrus; Ashammakhi, Nureddin

    2008-02-01

    Earlier we have reported on developing DS releasing bioabsorbable rods for inhibition of osteolysis [l]. Due to their unsatisfactory drug release profiles we assessed the use of sintering technique of enhancement of drug release in the current study. Melt extruded PLGA 80/20 rods were compounded 8 wt-% DS. Some rods were self reinforced (SR) and some of them were sterilized to get three different components with different drug release profiles. Different rods were sintered together with heat and pressure. Three different specimen groups with different construction were studied. Thermal properties were analyzed using differential scanning calorimetry (DSC). Changes of IV were performed with capillary analysis and drug release measurements with UV-Vis spectrophotometer. Mechanical strength were measured two weeks, when disintegration occurred. Release rate consisted of 1) sharp jump start peak, 2) second smoother peak, and 3) third smooth peak. Released DS concentrations reached local therapeutic levels and maintained at that stage for 24-36 days. All DS was released during 50-70 days. The drug release from multicomponent implant was more stable and commenced earlier than from initial rods. Such properties were favored ones. Initial shear strength was 82 MPa and it decreased to 15 MPa. The mechanical bonding was sufficient although the components disintegrated relatively fast. By sintering different PLGA/DS components with different release rates it is possible to construct a truly controlled release implant for bone fixation with anti-inflammatory properties.

  9. Forecasting the condition of petroleum impregnated load bearing ...

    African Journals Online (AJOL)

    Petroleum products (PP) used in industrial processes systematically fall on the load-bearing CRC structures and gradually impregnate therein. Currently, available guidelines for the assessment of technical condition and reliability of load-bearing CRC structures do not fully take into account the effect of viscosity of PP that ...

  10. Modeling of dynamically loaded hydrodynamic bearings at low Sommerfeld numbers

    DEFF Research Database (Denmark)

    Thomsen, Kim

    Current state of the art within the wind industry dictates the use of conventional rolling element bearings for main bearings. As wind turbine generators increase in size and output, so does the size of the main bearings and accordingly also the cost and potential risk of failure modes. The cost...... and failure risk of rolling element bearings do, however, grow exponentially with the size. Therefore hydrodynamic bearings can prove to be a competitive alternative to the current practice of rolling element bearings and ultimately help reducing the cost and carbon footprint of renewable energy generation....... The challenging main bearing operation conditions in a wind turbine pose a demanding development task for the design of a hydrodynamic bearing. In general these conditions include operation at low Reynolds numbers with frequent start and stop at high loads as well as difficult operating conditions dictated...

  11. Does aquatic exercise reduce hip and knee joint loading? In vivo load measurements with instrumented implants.

    Directory of Open Access Journals (Sweden)

    Ines Kutzner

    Full Text Available Aquatic exercises are widely used for rehabilitation or preventive therapies in order to enable mobilization and muscle strengthening while minimizing joint loading of the lower limb. The load reducing effect of water due to buoyancy is a main advantage compared to exercises on land. However, also drag forces have to be considered that act opposite to the relative motion of the body segments and require higher muscle activity. Due to these opposing effects on joint loading, the load-reducing effect during aquatic exercises remains unknown. The aim of this study was to quantify the joint loads during various aquatic exercises and to determine the load reducing effect of water. Instrumented knee and hip implants with telemetric data transfer were used to measure the resultant joint contact forces in 12 elderly subjects (6x hip, 6x knee in vivo. Different dynamic, weight-bearing and non-weight-bearing activities were performed by the subjects on land and in chest-high water. Non-weight-bearing hip and knee flexion/extension was performed at different velocities and with additional Aquafins. Joint forces during aquatic exercises ranged between 32 and 396% body weight (BW. Highest forces occurred during dynamic activities, followed by weight-bearing and slow non-weight-bearing activities. Compared to the same activities on land, joint forces were reduced by 36-55% in water with absolute reductions being greater than 100%BW during weight-bearing and dynamic activities. During non-weight-bearing activities, high movement velocities and additional Aquafins increased the joint forces by up to 59% and resulted in joint forces of up to 301%BW. This study confirms the load reducing effect of water during weight-bearing and dynamic exercises. Nevertheless, high drag forces result in increased joint contact forces and indicate greater muscle activity. By the choice of activity, movement velocity and additional resistive devices joint forces can be modulated

  12. A semi-analytical bearing model considering outer race flexibility for model based bearing load monitoring

    Science.gov (United States)

    Kerst, Stijn; Shyrokau, Barys; Holweg, Edward

    2018-05-01

    This paper proposes a novel semi-analytical bearing model addressing flexibility of the bearing outer race structure. It furthermore presents the application of this model in a bearing load condition monitoring approach. The bearing model is developed as current computational low cost bearing models fail to provide an accurate description of the more and more common flexible size and weight optimized bearing designs due to their assumptions of rigidity. In the proposed bearing model raceway flexibility is described by the use of static deformation shapes. The excitation of the deformation shapes is calculated based on the modelled rolling element loads and a Fourier series based compliance approximation. The resulting model is computational low cost and provides an accurate description of the rolling element loads for flexible outer raceway structures. The latter is validated by a simulation-based comparison study with a well-established bearing simulation software tool. An experimental study finally shows the potential of the proposed model in a bearing load monitoring approach.

  13. Shaft centre orbit for dynamically loaded radial bearings

    DEFF Research Database (Denmark)

    Klit, Peder; Vølund, Anders

    2002-01-01

    The aim of this work is to demonstrate how to utilize the bearings damping coefficients to estimate the orbit for a dynamically loaded journal bearing. The classical method for this analysis was developed by Booker in 1965 Booker1 and described further in 1972 Booker2. Several authors have refine...

  14. Vertically loaded pivot bearing for high-speed shafts

    International Nuclear Information System (INIS)

    Zippe, G.; Werner, D.; Keller, A.; Stephan, E.

    1974-01-01

    The pivot bearing subjected to vertical loads has a pivot with a rounded end and a diametral slot and a cup-shaped recess in the bearing box. The end of the pivot and the recess constitute a gap which widens towards the periphery of the bearing. The bearing box carries an attachment with a clearance, the shape of a hollow cylinder and accomodating the pivot and its shaft. To feed the lubricating oil surrounding and filling the bearing there is a groove either in the wall of the clearance or at the end of the pivot in the direction of rotation of the shaft or against it. The oil carried to the support point flows back into the oil bath surrounding the bearing through a slot in the bearing box. (DG) [de

  15. Bearing Capacity of Foundations subjected to Impact Loads

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo; Jakobsen, Kim Parsberg

    1996-01-01

    In the design process for foundations, the bearing capacity calculations are normally restricted to monotonic loads. Even in cases where the impact load is of significance the dynamic aspects are neglected by use of a traditional deterministic ultimate limit state analysis. Nevertheless it is com......In the design process for foundations, the bearing capacity calculations are normally restricted to monotonic loads. Even in cases where the impact load is of significance the dynamic aspects are neglected by use of a traditional deterministic ultimate limit state analysis. Nevertheless...

  16. Unbalance Response Prediction for Rotors on Ball Bearings Using Speed and Load Dependent Nonlinear Bearing Stiffness

    Science.gov (United States)

    Fleming, David P.; Poplawski, J. V.

    2003-01-01

    Rolling-element bearing forces vary nonlinearly with bearing deflection. Thus an accurate rotordynamic analysis requires that bearing forces corresponding to the actual bearing deflection be utilized. For this work bearing forces were calculated by COBRA-AHS, a recently developed rolling-element bearing analysis code. Bearing stiffness was found to be a strong function of bearing deflection, with higher deflection producing markedly higher stiffness. Curves fitted to the bearing data for a range of speeds and loads were supplied to a flexible rotor unbalance response analysis. The rotordynamic analysis showed that vibration response varied nonlinearly with the amount of rotor imbalance. Moreover, the increase in stiffness as critical speeds were approached caused a large increase in rotor and bearing vibration amplitude over part of the speed range compared to the case of constant bearing stiffness. Regions of bistable operation were possible, in which the amplitude at a given speed was much larger during rotor acceleration than during deceleration. A moderate amount of damping will eliminate the bistable region, but this damping is not inherent in ball bearings.

  17. Full Contoured Tooth-Implant Supported 3-Pointic All-Ceramic Denture During Occlusal Load Transfer in Lateral Region

    Directory of Open Access Journals (Sweden)

    Żmudzki J.

    2016-06-01

    Full Text Available Implant and a tooth supported dentures are avoided by dentists because of uneven distribution of occlusal loads between a stiffer implant and a more pliable tooth. The hypothesis was that a 3-point all-ceramic bridge supported on a natural second premolar tooth and a two-pieces typical implant bears safely mastication loads. The finite element analysis showed that the implant splinted by all-ceramic zirconium bridge with the second premolar was safe under lateral mastication load, but there was found an overload at wide zone of bone tissue around the implant under the load of 800 N. The patients can safely masticate, but comminution of hard food should be avoided and they should be instructed that after such an indiscretion they need to contact a dental professional, because, in spite of integrity of the prosthesis, the bone tissue around the implant may fail and there is a hazard of intrusion of the tooth.

  18. Load Transfer Characteristics of Various Designs of Three-Implant-Retained Mandibular Overdentures.

    Science.gov (United States)

    Tokar, Emre; Uludag, Bulent

    2015-01-01

    Many different attachment systems (eg, bars, studs, magnets, telescopic copings) have been used to retain overdentures. The current study aimed to investigate the load transfer characteristics and to compare the stress levels of four attachment designs for mandibular overdentures retained by one central implant and two inclined distal implants. Photoelastic mandibular models fabricated with three screw-type implants (Tapered Screw-Vent, 3.75 × 13 mm) were placed in the parasymphyseal area. The center implant was vertically oriented to the midline, and the other implants were embedded in the canine areas with a 20-degree angulation relative to the center implant. Four overdentures with different attachment designs (bar, bar/ball, bar/distally placed Rk-1s, and Locators) were studied in the context of this model. Vertical loads (100 N) were applied to the central fossa of the right first molar area of each overdenture. Stress levels that developed in the denture-bearing areas and around the implants were observed photoelastically and evaluated visually. The studied attachment designs showed low and moderate stress levels. The greatest stress was found with the bar/ball design, while the lowest stress levels were observed with the Locator attachment design. Stresses were concentrated on the loaded side for each design. All tested designs experienced moderate stress around the posterior edentulous area. None of the designs experienced more than moderate stress. The lowest stress was noted with the Locator attachments, which transmitted little discernible stress around the implants.

  19. Feasibility of Applying Controllable Lubrication to Dynamically Loaded Journal Bearings

    DEFF Research Database (Denmark)

    Estupinan, Edgar Alberto; Santos, Ilmar

    2009-01-01

    A multibody dynamic model of the main mechanical components of a hermetic reciprocating compressor is presented in this work. Considering that some of the mechanical elements are interconnected via thin fluid films, the multibody dynamic model is coupled to the equations from the dynamics...... of the fluid films, based on fluid film theory. For a dynamically loaded journal bearing, the fluid film pressure distribution can be computed by numerically solving the Reynolds equation, by means of finite-difference method. Particularly, in this study the main focus is on the lubrication behavior...... and reaction forces in a reciprocating compressor have a cyclic behavior, periodic oil pressure injection rules based on the instantaneous crank angle and load bearing condition can be established. In this paper, several bearing configurations working under different oil pressure injection rules conditions...

  20. CLINICAL CONSIDERATIONS OF DENTAL IMPLANT SYSTEM IN IMMEDIATE LOADING IMPLANT CASES

    Directory of Open Access Journals (Sweden)

    Carolina Damayanti Marpaung

    2015-06-01

    Full Text Available Immediate loading of dental implant has been researched intensively in the development of Branemark’s early concept of 2 stages implant placement. This was embarked from both patients and practiitioner’s convenience towards a simpler protocol and shorter time frame. Many recent researchers later found that micromotions derived from occlusal loading for a certain degree, instead of resulting a fibrous tissue encapsulation, can enhance the osseointegration process. Dental Implant system enhancement towards maximizing the primary stability held a key factor in Branemark’s concept development. Surgical protocol and implant design was found to give a significant contribution to the prognosis of immediate-loading implants.

  1. Lateral load performance of SIP walls with full bearing

    Science.gov (United States)

    Boren Yeh; Tom Skaggs; Xiping Wang; Tom Williamson

    2018-01-01

    The purpose of this study was to develop test data needed to characterize lateral load performance of structural insulated panel (SIP) walls with full bearing (restrained). The research program involved structural testing of 29 full-size SIP walls (8 ft tall by 8 ft long) of various configurations that bracket a range of SIP wall configurations commonly used in the...

  2. Load-bearing processes in agricultural wheel-soil systems

    NARCIS (Netherlands)

    Tijink, F.G.J.

    1988-01-01

    In soil dynamics we distinguish between loosening and loadbearing processes. Load-bearing processes which can occur under agricultural rollers, wheels, and tyres are dealt with In this dissertation.

    We classify rollers, wheels, and tyres and treat some general aspects of these

  3. Foot Loading Characteristics of Different Graduations of Partial Weight Bearing

    Science.gov (United States)

    Gusinde, Johannes; Pauser, Johannes; Swoboda, Bernd; Gelse, Kolja; Carl, Hans-Dieter

    2011-01-01

    Limited weight bearing of the lower extremity is a commonly applied procedure in orthopaedic rehabilitation after reconstructive forefoot surgery, trauma surgery and joint replacement. The most frequent limitations are given as percentage of body weight (BW) and represent 10 or 50% BW. The extent of foot loading under these graduations of partial…

  4. Transient Vibration Prediction for Rotors on Ball Bearings Using Load-dependent Non-linear Bearing Stiffness

    Science.gov (United States)

    Fleming, David P.; Poplawski, J. V.

    2002-01-01

    Rolling-element bearing forces vary nonlinearly with bearing deflection. Thus an accurate rotordynamic transient analysis requires bearing forces to be determined at each step of the transient solution. Analyses have been carried out to show the effect of accurate bearing transient forces (accounting for non-linear speed and load dependent bearing stiffness) as compared to conventional use of average rolling-element bearing stiffness. Bearing forces were calculated by COBRA-AHS (Computer Optimized Ball and Roller Bearing Analysis - Advanced High Speed) and supplied to the rotordynamics code ARDS (Analysis of Rotor Dynamic Systems) for accurate simulation of rotor transient behavior. COBRA-AHS is a fast-running 5 degree-of-freedom computer code able to calculate high speed rolling-element bearing load-displacement data for radial and angular contact ball bearings and also for cylindrical and tapered roller beatings. Results show that use of nonlinear bearing characteristics is essential for accurate prediction of rotordynamic behavior.

  5. Load Bearing Equipment for Bone and Muscle Project

    Science.gov (United States)

    Terrier, Douglas; Clayton, Ronald G.; Shackelford, Linda

    2015-01-01

    Axial skeletal loads coupled with muscle torque forces around joints maintain bone. Astronauts working in pairs to exercise can provide high eccentric loads for each other that are most effective. A prototype of load bearing equipment that will allow astronauts to perform exercises using each other for counter force generation in a controlled fashion and provide eccentric overload is proposed. A frame and attachments that can be rapidly assembled for use and easily stored will demonstrate feasibility of a design that can be adapted for ISS testing and Orion use.

  6. Bearing load distribution studies in a multi bearing rotor system and a remote computing method based on the internet

    International Nuclear Information System (INIS)

    Yang, Zhao Jian; Peng, Ze Jun; Kim, Seock Sam

    2004-01-01

    A model in the form of a Bearing Load Distribution (BLD) matrix in the Multi Bearing Rotor System (MBRS) is established by a transfer matrix equation with the consideration of a bearing load, elevation and uniform load distribution. The concept of Bearing Load Sensitivity (BLS) is proposed and matrices for load and elevation sensitivity are obtained. In order to share MBRS design resources on the internet with remote customers, the basic principle of Remote Computing (RC) based on the internet is introduced ; the RC of the BLD and BLS is achieved by Microsoft Active Server Pages (ASP) technology

  7. Human footprint variation while performing load bearing tasks.

    Directory of Open Access Journals (Sweden)

    Cara M Wall-Scheffler

    Full Text Available Human footprint fossils have provided essential evidence about the evolution of human bipedalism as well as the social dynamics of the footprint makers, including estimates of speed, sex and group composition. Generally such estimates are made by comparing footprint evidence with modern controls; however, previous studies have not accounted for the variation in footprint dimensions coming from load bearing activities. It is likely that a portion of the hominins who created these fossil footprints were carrying a significant load, such as offspring or foraging loads, which caused variation in the footprint which could extend to variation in any estimations concerning the footprint's maker. To identify significant variation in footprints due to load-bearing tasks, we had participants (N = 30, 15 males and 15 females walk at a series of speeds carrying a 20kg pack on their back, side and front. Paint was applied to the bare feet of each participant to create footprints that were compared in terms of foot length, foot width and foot area. Female foot length and width increased during multiple loaded conditions. An appreciation of footprint variability associated with carrying loads adds an additional layer to our understanding of the behavior and morphology of extinct hominin populations.

  8. Drug loaded biodegradable load-bearing nanocomposites for damaged bone repair

    Science.gov (United States)

    Gutmanas, E. Y.; Gotman, I.; Sharipova, A.; Psakhie, S. G.; Swain, S. K.; Unger, R.

    2017-09-01

    In this paper we present a short review-scientific report on processing and properties, including in vitro degradation, of load bearing biodegradable nanocomposites as well as of macroporous 3D scaffolds for bone ingrowth. Biodegradable implantable devices should slowly degrade over time and disappear with ingrown of natural bone replacing the synthetic graft. Compared to low strength biodegradable polymers, and brittle CaP ceramics, biodegradable CaP-polymer and CaP-metal nanocomposites, mimicking structure of natural bone, as well as strong and ductile metal nanocomposites can provide to implantable devices both strengths and toughness. Nanostructuring of biodegradable β-TCP (tricalcium phosphate)-polymer (PCL and PLA), β-TCP-metal (FeMg and FeAg) and of Fe-Ag composites was achieved employing high energy attrition milling of powder blends. Nanocomposite powders were consolidated to densities close to theoretical by high pressure consolidation at ambient temperature—cold sintering, with retention of nanoscale structure. The strength of developed nanocomposites was significantly higher as compared with microscale composites of the same or similar composition. Heat treatment at moderate temperatures in hydrogen flow resulted in retention of nanoscale structure and higher ductility. Degradation of developed biodegradable β-TCP-polymer, β-TCP-metal and of Fe-Ag nanocomposites was studied in physiological solutions. Immersion tests in Ringer's and saline solution for 4 weeks resulted in 4 to 10% weight loss and less than 50% decrease in compression or bending strength, the remaining strength being significantly higher than the values reported for other biodegradable materials. Nanostructuring of Fe-Ag based materials resulted also in an increase of degradation rate because of creation on galvanic Fe-Ag nanocouples. In cell culture experiments, the developed nanocomposites supported the attachment the human osteoblast cells and exhibited no signs of cytotoxicity

  9. Structural response testing of thermal barrier load bearing ceramic pads

    International Nuclear Information System (INIS)

    Pickering, J.L.; Black, W.E.; Luci, R.K.; Oland, C.B.

    1983-01-01

    A load-bearing insulating structure for use in a high-temperature gas-cooled reactor (HTGR) was investigated. The structure was composed of dense ceramic materials in the form of circular pads arranged in a stack. Specifically, the test program was structured to investigate the isolation effectiveness of interface materials placed between the ceramic pads to reduce the effectiveness of mechanically induced loads. The tests were conducted at room temperature using tapered loading platens on single ceramic pads. Seventeen alumina specimens, representing two types of material and two thicknesses, were tested. Three interface material thicknesses were introduced using silica cloth and graphite foil. Pre- and post-test nondestructive examinations were conducted in an effort to identify potential damage-inducing anomalies in the ceramic pads. A total of 62 tests was conducted with all specimens eventually loaded to failure

  10. Discontinuity effects in dynamically loaded tilting pad journal bearings

    DEFF Research Database (Denmark)

    Thomsen, Kim; Klit, Peder; Vølund, Anders

    2011-01-01

    This paper describes two discontinuity effects that can occur when modelling radial tilting pad bearings subjected to high dynamic loads. The first effect to be treated is a pressure build-up discontinuity effect. The second effect is a contact-related discontinuity that disappears when a contact...... force is included in the theoretical model. Methods for avoiding the pressure build-up discontinuity effect are proposed....

  11. Revival of pure titanium for dynamically loaded porous implants using additive manufacturing.

    Science.gov (United States)

    Wauthle, Ruben; Ahmadi, Seyed Mohammad; Amin Yavari, Saber; Mulier, Michiel; Zadpoor, Amir Abbas; Weinans, Harrie; Van Humbeeck, Jan; Kruth, Jean-Pierre; Schrooten, Jan

    2015-09-01

    Additive manufacturing techniques are getting more and more established as reliable methods for producing porous metal implants thanks to the almost full geometrical and mechanical control of the designed porous biomaterial. Today, Ti6Al4V ELI is still the most widely used material for porous implants, and none or little interest goes to pure titanium for use in orthopedic or load-bearing implants. Given the special mechanical behavior of cellular structures and the material properties inherent to the additive manufacturing of metals, the aim of this study is to investigate the properties of selective laser melted pure unalloyed titanium porous structures. Therefore, the static and dynamic compressive properties of pure titanium structures are determined and compared to previously reported results for identical structures made from Ti6Al4V ELI and tantalum. The results show that porous Ti6Al4V ELI still remains the strongest material for statically loaded applications, whereas pure titanium has a mechanical behavior similar to tantalum and is the material of choice for cyclically loaded porous implants. These findings are considered to be important for future implant developments since it announces a potential revival of the use of pure titanium for additively manufactured porous implants. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Bone healing response in cyclically loaded implants: Comparing zero, one, and two loading sessions per day.

    Science.gov (United States)

    de Barros E Lima Bueno, Renan; Dias, Ana Paula; Ponce, Katia J; Wazen, Rima; Brunski, John B; Nanci, Antonio

    2018-05-31

    When bone implants are loaded, they are inevitably subjected to displacement relative to bone. Such micromotion generates stress/strain states at the interface that can cause beneficial or detrimental sequels. The objective of this study is to better understand the mechanobiology of bone healing at the tissue-implant interface during repeated loading. Machined screw shaped Ti implants were placed in rat tibiae in a hole slightly bigger than the implant diameter. Implants were held stable by a specially-designed bone plate that permits controlled loading. Three loading regimens were applied, (a) zero loading, (b) one daily loading session of 60 cycles with an axial force of 1.5 N/cycle for 7 days, and (c) two such daily sessions with the same axial force also for 7 days. Finite element analysis was used to characterize the mechanobiological conditions produced by the loading sessions. After 7 days, the implants with surrounding interfacial tissue were harvested and processed for histological, histomorphometric and DNA microarray analyses. Histomorphometric analyses revealed that the group subjected to repeated loading sessions exhibited a significant decrease in bone-implant contact and increase in bone-implant distance, as compared to unloaded implants and those subjected to only one loading session. Gene expression profiles differed during osseointegration between all groups mainly with respect to inflammatory and unidentified gene categories. The results indicate that increasing the daily cyclic loading of implants induces deleterious changes in the bone healing response, most likely due to the accumulation of tissue damage and associated inflammatory reaction at the bone-implant interface. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

  13. Influence of controlled immediate loading and implant design on peri-implant bone formation.

    Science.gov (United States)

    Vandamme, Katleen; Naert, Ignace; Geris, Liesbet; Vander Sloten, Jozef; Puers, Robert; Duyck, Joke

    2007-02-01

    Tissue formation at the implant interface is known to be sensitive to mechanical stimuli. The aim of the study was to compare the bone formation around immediately loaded versus unloaded implants in two different implant macro-designs. A repeated sampling bone chamber with a central implant was installed in the tibia of 10 rabbits. Highly controlled loading experiments were designed for a cylindrical (CL) and screw-shaped (SL) implant, while the unloaded screw-shaped (SU) implant served as a control. An F-statistic model with alpha=5% determined statistical significance. A significantly higher bone area fraction was observed for SL compared with SU (pimplant contact occurred was the highest for SL and significantly different from SU (pimplant contact was observed, a loading (SL versus SU: p=0.0049) as well as an implant geometry effect (SL versus CL: p=0.01) was found, in favour of the SL condition. Well-controlled immediate implant loading accelerates tissue mineralization at the interface. Adequate bone stimulation via mechanical coupling may account for the larger bone response around the screw-type implant compared with the cylindrical implant.

  14. Bone-Implant Contact around Crestal and Subcrestal Dental Implants Submitted to Immediate and Conventional Loading

    Directory of Open Access Journals (Sweden)

    Ana Emília Farias Pontes

    2014-01-01

    Full Text Available The present study aims to evaluate the influence of apicocoronal position and immediate and conventional loading in the percentage of bone-implant contact (BIC. Thus, 36 implants were inserted in the edentulous mandible from six dogs. Three implants were installed in each hemimandible, in different positions in relation to the ridge: Bone Level (at crestal bone level, Minus 1 (one millimeter apical to crestal bone, and Minus 2 (two millimeters apical to crestal bone. In addition, each hemimandible was submitted to a loading protocol: immediate (prosthesis installed 24 hours after implantation or conventional (prosthesis installed 120 days after implantation. Ninety days after, animals were killed, and implant and adjacent tissues were prepared for histometric analysis. BIC values from immediate loaded implants were 58.7%, 57.7%, and 51.1%, respectively, while conventional loaded implants were 61.8%, 53.8%, and 68.4%. Differences statistically significant were not observed among groups (P=0.10, ANOVA test. These findings suggest that different apicocoronal positioning and loading protocols evaluated did not interfere in the percentage of bone-implant contact, suggesting that these procedures did not jeopardize osseointegration.

  15. Immediate loading with single-piece implant following extraction

    Directory of Open Access Journals (Sweden)

    Hemlata Dwivedi

    2017-01-01

    Full Text Available Although dental implantology had evolved over a number of years, many dental surgeons are unaware of the concept of immediate loading with the use of one-piece implant that began in the early 1960s. The goal of successful prosthodontics rehabilitation is to provide function, esthetics, and comfort to the patient. The aim of this literature is to provide an overview of one-piece implant, with its advantages and disadvantages over conventional two-piece implant. Immediate prosthetic of a one-piece system allows for a better tissue healing and better adhesion of gingival mucosa to form a collar which is healthy and adherent to the implant, avoiding a second surgical procedure, and also includes a very important aspect esthetics. This article describes a case report of immediate loading with single-piece implant following extraction.

  16. LOAD BEARING CAPACITY OF THE GLASS RAILING ELEMENT

    Directory of Open Access Journals (Sweden)

    Elizabeta Šamec

    2016-02-01

    Full Text Available In this paper some basic physical and mechanical properties of glass as structural material are presented. This research is about specifically manufactured glass railing element that will be a part of a pedestrian bridge construction in Zagreb, Croatia. Load bearing capacity test of the glass railing element is conducted within the Faculty of Civil Engineering in Zagreb and obtained experimental results are discussed and compared to the ones provided by the numerical model. Taking into account the behaviour of laminated glass and results of experimental and numerical testing, glass railing element can be regarded as safe.

  17. Finite Element Analysis of Bone Stress for Miniscrew Implant Proximal to Root Under Occlusal Force and Implant Loading.

    Science.gov (United States)

    Shan, Li-Hua; Guo, Na; Zhou, Guan-jun; Qie, Hui; Li, Chen-Xi; Lu, Lin

    2015-10-01

    Because of the narrow interradicular spaces and varying oral anatomies of individual patients, there is a very high risk of root proximity during the mini implants inserting. The authors hypothesized that normal occlusal loading and implant loading affected the stability of miniscrew implants placed in proximity or contact with the adjacent root. The authors implemented finite element analysis (FEA) to examine the effectiveness of root proximity and root contact. Stress distribution in the bone was assessed at different degrees of root proximity by generating 4 finite element models: the implant touches the root surface, the implant was embedded in the periodontal membrane, the implant touches the periodontal surface, and the implant touches nothing. Finite element analysis was then carried out with simulations of 2 loading conditions for each model: condition A, involving only tooth loading and condition B, involving both tooth and implant loading. Under loading condition A, the maximum stress on the bone for the implant touching the root was the distinctly higher than that for the other models. For loading condition B, peak stress areas for the implant touching the root were the area around the neck of the mini implant and the point of the mini implant touches the root. The results of this study suggest that normal occlusal loading and implant loading contribute to the instability of the mini implant when the mini implant touches the root.

  18. The effect of external dynamic loads on the lifetime of rolling element bearings: accurate measurement of the bearing behaviour

    International Nuclear Information System (INIS)

    Jacobs, W; Boonen, R; Sas, P; Moens, D

    2012-01-01

    Accurate prediction of the lifetime of rolling element bearings is a crucial step towards a reliable design of many rotating machines. Recent research emphasizes an important influence of external dynamic loads on the lifetime of bearings. However, most lifetime calculations of bearings are based on the classical ISO 281 standard, neglecting this influence. For bearings subjected to highly varying loads, this leads to inaccurate estimations of the lifetime, and therefore excessive safety factors during the design and unexpected failures during operation. This paper presents a novel test rig, developed to analyse the behaviour of rolling element bearings subjected to highly varying loads. Since bearings are very precise machine components, their motion can only be measured in an accurately controlled environment. Otherwise, noise from other components and external influences such as temperature variations will dominate the measurements. The test rig is optimised to perform accurate measurements of the bearing behaviour. Also, the test bearing is fitted in a modular structure, which guarantees precise mounting and allows testing different types and sizes of bearings. Finally, a fully controlled multi-axial static and dynamic load is imposed on the bearing, while its behaviour is monitored with capacitive proximity probes.

  19. Revival of pure titanium for dynamically loaded porous implants using additive manufacturing

    International Nuclear Information System (INIS)

    Wauthle, Ruben; Ahmadi, Seyed Mohammad; Amin Yavari, Saber; Mulier, Michiel; Zadpoor, Amir Abbas; Weinans, Harrie; Van Humbeeck, Jan; Kruth, Jean-Pierre; Schrooten, Jan

    2015-01-01

    Additive manufacturing techniques are getting more and more established as reliable methods for producing porous metal implants thanks to the almost full geometrical and mechanical control of the designed porous biomaterial. Today, Ti6Al4V ELI is still the most widely used material for porous implants, and none or little interest goes to pure titanium for use in orthopedic or load-bearing implants. Given the special mechanical behavior of cellular structures and the material properties inherent to the additive manufacturing of metals, the aim of this study is to investigate the properties of selective laser melted pure unalloyed titanium porous structures. Therefore, the static and dynamic compressive properties of pure titanium structures are determined and compared to previously reported results for identical structures made from Ti6Al4V ELI and tantalum. The results show that porous Ti6Al4V ELI still remains the strongest material for statically loaded applications, whereas pure titanium has a mechanical behavior similar to tantalum and is the material of choice for cyclically loaded porous implants. These findings are considered to be important for future implant developments since it announces a potential revival of the use of pure titanium for additively manufactured porous implants. - Highlights: • The mechanical properties of CP Ti grade 1 porous structures are studied. • The results are compared with identical structures in Ti6Al4V ELI and tantalum. • Ti6Al4V ELI structures are about two times stronger under a static compressive load. • CP Ti structures deform continuously without fracture while loaded statically. • CP Ti structures have a higher fatigue life compared to Ti6Al4V ELI structures

  20. Revival of pure titanium for dynamically loaded porous implants using additive manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Wauthle, Ruben, E-mail: ruben.wauthle@3dsystems.com [KU Leuven, Department of Mechanical Engineering, Section Production Engineering, Machine Design and Automation (PMA), Celestijnenlaan 300B, 3001 Leuven (Belgium); 3D Systems - LayerWise NV, Grauwmeer 14, 3001 Leuven (Belgium); Ahmadi, Seyed Mohammad; Amin Yavari, Saber [Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628 CD, Delft (Netherlands); Mulier, Michiel [KU Leuven, Department of Orthopaedics, Weligerveld 1, 3212 Pellenberg (Belgium); Zadpoor, Amir Abbas [Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628 CD, Delft (Netherlands); Weinans, Harrie [Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628 CD, Delft (Netherlands); Department of Orthopedics & department of Rheumatology, UMC Utrecht, Heidelberglaan 100, 3584 CX, Utrecht (Netherlands); Van Humbeeck, Jan [KU Leuven, Department of Materials Engineering, Kasteelpark Arenberg 44, PB 2450, 3001 Leuven (Belgium); Kruth, Jean-Pierre [KU Leuven, Department of Mechanical Engineering, Section Production Engineering, Machine Design and Automation (PMA), Celestijnenlaan 300B, 3001 Leuven (Belgium); Schrooten, Jan [KU Leuven, Department of Materials Engineering, Kasteelpark Arenberg 44, PB 2450, 3001 Leuven (Belgium); KU Leuven, Prometheus, Division of Skeletal Tissue Engineering, PB 813, O& N1, Herestraat 49, 3000 Leuven (Belgium)

    2015-09-01

    Additive manufacturing techniques are getting more and more established as reliable methods for producing porous metal implants thanks to the almost full geometrical and mechanical control of the designed porous biomaterial. Today, Ti6Al4V ELI is still the most widely used material for porous implants, and none or little interest goes to pure titanium for use in orthopedic or load-bearing implants. Given the special mechanical behavior of cellular structures and the material properties inherent to the additive manufacturing of metals, the aim of this study is to investigate the properties of selective laser melted pure unalloyed titanium porous structures. Therefore, the static and dynamic compressive properties of pure titanium structures are determined and compared to previously reported results for identical structures made from Ti6Al4V ELI and tantalum. The results show that porous Ti6Al4V ELI still remains the strongest material for statically loaded applications, whereas pure titanium has a mechanical behavior similar to tantalum and is the material of choice for cyclically loaded porous implants. These findings are considered to be important for future implant developments since it announces a potential revival of the use of pure titanium for additively manufactured porous implants. - Highlights: • The mechanical properties of CP Ti grade 1 porous structures are studied. • The results are compared with identical structures in Ti6Al4V ELI and tantalum. • Ti6Al4V ELI structures are about two times stronger under a static compressive load. • CP Ti structures deform continuously without fracture while loaded statically. • CP Ti structures have a higher fatigue life compared to Ti6Al4V ELI structures.

  1. Analysis of bearing stiffness variations, contact forces and vibrations in radially loaded double row rolling element bearings with raceway defects

    Science.gov (United States)

    Petersen, Dick; Howard, Carl; Sawalhi, Nader; Moazen Ahmadi, Alireza; Singh, Sarabjeet

    2015-01-01

    A method is presented for calculating and analyzing the quasi-static load distribution and varying stiffness of a radially loaded double row bearing with a raceway defect of varying depth, length, and surface roughness. The method is applied to ball bearings on gearbox and fan test rigs seeded with line or extended outer raceway defects. When balls pass through the defect and lose all or part of their load carrying capacity, the load is redistributed between the loaded balls. This includes balls positioned outside the defect such that good raceway sections are subjected to increased loading when a defect is present. The defective bearing stiffness varies periodically at the ball spacing, and only differs from the good bearing case when balls are positioned in the defect. In this instance, the stiffness decreases in the loaded direction and increases in the unloaded direction. For an extended spall, which always has one or more balls positioned in the defect, this results in an average stiffness over the ball spacing period that is lower in the loaded direction in comparison to both the line spall and good bearing cases. The variation in bearing stiffness due to the defect produces parametric excitations of the bearing assembly. The qualitative character of the vibration response correlates to the character of the stiffness variations. Rapid stiffness changes at a defect exit produce impulses. Slower stiffness variations due to large wavelength waviness features in an extended spall produce low frequency excitation which results in defect components in the velocity spectra. The contact forces fluctuate around the quasi-static loads on the balls, with rapid stiffness changes producing high magnitude impulsive force fluctuations. Furthermore, it is shown that analyzing the properties of the dynamic model linearized at the quasi-static solutions provides greater insight into the time-frequency characteristics of the vibration response. This is demonstrated by relating

  2. High-Speed Shaft Bearing Loads Testing and Modeling in the NREL Gearbox Reliability Collaborative: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    McNiff, B.; Guo, Y.; Keller, J.; Sethuraman, L.

    2014-12-01

    Bearing failures in the high speed output stage of the gearbox are plaguing the wind turbine industry. Accordingly, the National Renewable Energy Laboratory (NREL) Gearbox Reliability Collaborative (GRC) has performed an experimental and theoretical investigation of loads within these bearings. The purpose of this paper is to describe the instrumentation, calibrations, data post-processing and initial results from this testing and modeling effort. Measured HSS torque, bending, and bearing loads are related to model predictions. Of additional interest is examining if the shaft measurements can be simply related to bearing load measurements, eliminating the need for invasive modifications of the bearing races for such instrumentation.

  3. Gearbox Reliability Collaborative Investigation of High-Speed-Shaft Bearing Loads

    Energy Technology Data Exchange (ETDEWEB)

    Keller, Jonathan [National Renewable Energy Lab. (NREL), Golden, CO (United States); Guo, Yi [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-06-01

    The loads and contact stresses in the bearings of the high speed shaft section of the Gearbox Reliability Collaborative gearbox are examined in this paper. The loads were measured though strain gauges installed on the bearing outer races during dynamometer testing of the gearbox. Loads and stresses were also predicted with a simple analytical model and higher-fidelity commercial models. The experimental data compared favorably to each model, and bearing stresses were below thresholds for contact fatigue and axial cracking.

  4. Carga inmediata en implantes dentales Immediate loading of dental implants

    Directory of Open Access Journals (Sweden)

    C. Concejo Cútoli

    2005-10-01

    Full Text Available El protocolo de carga convencional en una o dos fases quirúrgicas ha sido evaluado durante los últimos 30 años bajo todas las condiciones clínicas posibles. En comparación, la carga inmediata es un protocolo relativamente nuevo que necesita de una estricta evaluación clínica. Realizamos una búsqueda bibliográfica sobre los ensayos clínicos publicados de carga inmediata en función de las diferentes opciones terapéuticas que se pueden plantear. Se hallaron resultados comparables para las dos estrategias de carga en mandíbulas edéntulas. Para el tratamiento con prótesis inmediata de maxilares totalmente edéntulos, restauraciones parciales e unitarias es todavía necesaria una selección adecuada de pacientes y un diseño conservador de la prótesis provisional. La necesidad de ensayos clínicos sencillos aleatorizados de doble ciego, con suficiente número de pacientes y adecuado seguimiento, que comparen una determinada situación clínica con un patrón oclusal de la prótesis provisional bien definido, son imprescindibles para acabar de confirmar la seguridad de la técnica.The protocol for conventional loading in one or two surgical stages has been evaluated over the last 30 years under all the possible clinical conditions. By comparison, immediate loading is a relatively new protocol that requires strict clinical evaluation. We conducted a search of the literature published concerning clinical trials on immediate loading according to the different therapeutic options that could be considered. Comparable results were found for both loading strategies in edentulous mandibles. For treatment involving an immediate prosthesis for totally edentulous mandibles, partial and single tooth restorations, patients have to be selected adequately and provisional prostheses have to be designed conservatively. In order to completely confirm the safety of the technique, double-blind, simple, randomized clinical trials have to be carried out with

  5. Bone reactions at implants subjected to experimental peri-implantitis and static load. A study in the dog

    DEFF Research Database (Denmark)

    Gotfredsen, K; Berglundh, T; Lindhe, J

    2002-01-01

    during a 12-week interval, the screws were reactivated. Thus, the model included 3 different experimental sites of each surface group: group M+L (mucositis+load); group P (peri-implantitis); group P+L (peri-implantitis+load). Fluorochrome labels were injected and standardized radiographs obtained....... The animals were sacrificed and block biopsies of all implant sites dissected and prepared for histological analysis. RESULTS: It was demonstrated that the lateral static load failed to induce peri-implant bone loss at implants with mucositis and failed to enhance the bone loss at implants with experimental...... peri-implantitis. The proportion of bone labels and the bone density in the interface zone were significantly higher in group P+L than in group P. CONCLUSION: It is suggested that a lateral static load with controlled forces may not be detrimental to implants exhibiting mucositis or peri-implantitis....

  6. The effect of varying implant position in immediately loaded implant-supported mandibular overdentures.

    Science.gov (United States)

    Shaarawy, Mohammed A; Aboelross, Ehab M

    2013-06-01

    This study was carried out to evaluate the effect of varying implant position in immediately loaded implant-supported mandibular overdentures on peri-implant bone density, muscle activity, and patient satisfaction. Fourteen completely edentulous patients were selected for the study. After complete denture construction, patients were divided into 2 equal groups. Four dental implants were installed bilaterally in the interforaminal region in the first group, while in the second group, 4 dental implants were inserted bilaterally: 2 in the interforaminal region and 2 in the first molar area. Immediately after suturing, telescopic abutments were screwed to the implants, and the retaining caps were picked up into the fitting surface of the lower denture, which was delivered to the patient. Patients were recalled for radiographic bone density evaluation just after denture delivery and then at 3, 6, and 12 months thereafter. Muscle activities of masseter and temporalis muscles as well as patient satisfaction were also evaluated. The results of the study showed a high success rate approximating 98.2% of the immediately loaded implants. The electromyographic (EMG) records of both muscles in group 1 were significantly higher during chewing hard food after 3 months compared with group 2 (P overdentures through posterior placement beyond the interforaminal area results in a favorable response in terms of increased peri-implant bone density as well as decreased EMG activity of masseter and temporalis muscles.

  7. Implant Mandibular Overdentures Retained by Immediately Loaded Implants: A 1-Year Randomized Trial Comparing the Clinical and Radiographic Outcomes Between Mini Dental Implants and Standard-Sized Implants.

    Science.gov (United States)

    Zygogiannis, Kostas; Aartman, Irene Ha; Parsa, Azin; Tahmaseb, Ali; Wismeijer, Daniel

    The aim of this 1-year randomized trial was to evaluate and compare the clinical and radiographic performance of four immediately loaded mini dental implants (MDIs) and two immediately loaded standard-sized tissue-level (STL) implants, placed in the interforaminal region of the mandible and used to retain mandibular overdentures (IODs) in completely edentulous patients. A total of 50 completely edentulous patients wearing conventional maxillary dentures and complaining about insufficient retention of their mandibular dentures were divided into two groups; 25 patients received four MDIs and 25 patients received two STL implants. The marginal bone loss (MBL) at the mesial and distal sides of each implant was assessed by means of standardized intraoral radiographs after a period of 1 year. Implant success and survival rates were also calculated. Immediate loading was possible for all patients in the first group. In the second group, an immediate loading protocol could not be applied for 10 patients. These patients were treated with a delayed loading protocol. A mean MBL of 0.42 ± 0.56 mm for the MDIs and 0.54 ± 0.49 mm for the immediately loaded STL implants was recorded at the end of the evaluation period. There was no statistically significant difference between the MDIs and the immediately loaded STL implants. Two MDIs failed, resulting in a survival rate of 98%. The success rate was 91%. For the immediately loaded conventional implants, the survival rate was 100% and the success rate 96.7% after 1 year of function. However, in 10 patients, the immediate loading protocol could not be followed. Considering the limitations of this short-term clinical study, immediate loading of four unsplinted MDIs or two splinted STL implants to retain mandibular overdentures seems to be a feasible treatment option. The marginal bone level changes around the MDIs were well within the clinically acceptable range.

  8. Simulation of peri-implant bone healing due to immediate loading in dental implant treatments.

    Science.gov (United States)

    Chou, Hsuan-Yu; Müftü, Sinan

    2013-03-15

    The goal of this work was to investigate the role of immediate loading on the peri-implant bone healing in dental implant treatments. A mechano-regulatory tissue differentiation model that takes into account the stimuli through the solid and the fluid components of the healing tissue, and the diffusion of pluripotent stem cells into the healing callus was used. A two-dimensional axisymmetric model consisting of a dental implant, the healing callus tissue and the host bone tissue was constructed for the finite element analysis. Poroelastic material properties were assigned to the healing callus and the bone tissue. The effects of micro-motion, healing callus size, and implant thread design on the length of the bone-to-implant contact (BIC) and the bone volume (BV) formed in the healing callus were investigated. In general, the analysis predicted formation of a continuous layer of soft tissue along the faces of the implant which are parallel to the loading direction. This was predicted to be correlated with the high levels of distortional strain transferred through the solid component of the stimulus. It was also predicted that the external threads on the implant, redistribute the interfacial load, thus help reduce the high distortional stimulus and also help the cells to differentiate to bone tissue. In addition, the region underneath the implant apex was predicted to experience high fluid stimulus that results in the development of soft tissue. The relationship between the variables considered in this study and the outcome measures, BV and BIC, was found to be highly nonlinear. A three-way analysis of variance (ANOVA) of the results was conducted and it showed that micro-motion presents the largest hindrance to bone formation during healing. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. Effect of a novel load-bearing trabecular Nitinol scaffold on rabbit radius bone regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Gotman, Irena, E-mail: gotman@technion.ac.il; Gutmanas, Elazar Y., E-mail: gutmanas@technion.ac.il [Department of Materials Science and Engineering, Techion-Israel Institute of Technology, Haifa, 32000 Israel (Israel); National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Zaretzky, Asaph [The Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, 31096 Israel (Israel); Psakhie, Sergey G. [National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation)

    2015-10-27

    The research aim was to evaluate the bone regeneration capability of novel load-bearing NiTi alloy (Nitinol) scaffolds in a critical-size defect (CSD) model. High strength “trabecular Nitinol” scaffolds were prepared by PIRAC (Powder Immersion Reaction Assisted Coating) annealing of the highly porous Ni foam in Ti powder at 900°C. This was followed by PIRAC nitriding to mitigate the release of potentially toxic Ni ions. Scaffolds phase composition and microstructure were characterized by X-ray diffraction and scanning electron microscopy (SEM/EDS), and their mechanical properties were tested in compression. New Zealand white rabbits received bone defect in right radius and were divided in four groups randomly. In the control group, nothing was placed in the defect. In other groups, NiTi scaffolds were implanted in the defect: (i) as produced, (ii) loaded with bone marrow aspirate (BMA), and (iii) biomimetically CaP-coated. The animals were sacrificed after 12 weeks. The forelimbs with scaffolds were resected, fixed, sectioned and examined in SEM. New bone formation inside the scaffold was studied by EDS analysis and by the processing of backscattered electron images. Bone ingrowth into the scaffold was observed in all implant groups, mostly next to the ulna. New bone formation was strongly enhanced by BMA loading and biomimeatic CaP coating, the bone penetrating as much as 1–1.5 mm into the scaffold. The results of this preliminary study demonstrate that the newly developed high strength trabecular Nitinol scaffolds can be successfully used for bone regeneration in critical size defects.

  10. The effect of loading rate on pile bearing capacity of saturated sand

    NARCIS (Netherlands)

    Archeewa, E.

    2005-01-01

    Pile load tests are commonly used by engineers to determine its bearing capacity. At present, there are three methods of pile load tests: the static, the dynamic and the quasi-static test. The static pile load test is done by applying an axial load on the pile with a long duration. The dynamic and

  11. Effect of carbon ion implantation on the tribology of metal-on-metal bearings for artificial joints.

    Science.gov (United States)

    Koseki, Hironobu; Tomita, Masato; Yonekura, Akihiko; Higuchi, Takashi; Sunagawa, Sinya; Baba, Koumei; Osaki, Makoto

    2017-01-01

    Metal-on-metal (MoM) bearings have become popular due to a major advantage over metal-on-polymer bearings for total hip arthroplasty in that the larger femoral head and hydrodynamic lubrication of the former reduce the rate of wear. However, concerns remain regarding adverse reactions to metal debris including metallosis caused by metal wear generated at the taper-head interface and another modular junction. Our group has hypothesized that carbon ion implantation (CII) may improve metal wear properties. The purpose of this study was to investigate the wear properties and friction coefficients of CII surfaces with an aim to ultimately apply these surfaces to MoM bearings in artificial joints. CII was applied to cobalt-chromium-molybdenum (Co-Cr-Mo) alloy substrates by plasma source ion implantation. The substrates were characterized using scanning electron microscopy and a 3D measuring laser microscope. Sliding contact tests were performed with a simple geometry pin-on-plate wear tester at a load of 2.5 N, a calculated contact pressure of 38.5 MPa (max: 57.8 MPa), a reciprocating velocity of 30 mm/s, a stroke length of 60 mm, and a reciprocating cycle count of 172,800 cycles. The surfaces of the CII substrates were generally featureless with a smooth surface topography at the same level as untreated Co-Cr-Mo alloy. Compared to the untreated Co-Cr-Mo alloy, the CII-treated bearings had lower friction coefficients, higher resistance to catastrophic damage, and prevented the adhesion of wear debris. The results of this study suggest that the CII surface stabilizes the wear status due to the low friction coefficient and low infiltration of partner materials, and these properties also prevent the adhesion of wear debris and inhibit excessive wear. Carbon is considered to be biologically inert; therefore, CII is anticipated to be applicable to the bearing surfaces of MoM prostheses.

  12. Changes in resonance frequency analysis assessed by Osstell mentor during osseointegration: comparison between immediately loaded implants and control implants without load

    Directory of Open Access Journals (Sweden)

    M. González-Jaranay

    2014-10-01

    Full Text Available Aim: The aim of this prospective clinical study was to evaluate the changes in resonance frequency analysis (RFA, assessed by Osstell Mentor, obtaining information on the implant stability quotient (ISQ during implants tissue integration for immediately loaded and non-loaded control implants. Materials and methods: A total of 40 implants, 20 implants with no immediate loading (control and 20 immediately loaded implants (test, were placed in 15 patients. ISQ implants was evaluated at baseline and at 6 and 8 weeks. Provisional crowns were removed at 8 weeks, when the definitive restoration was placed. Data of control and test implants and maxillary and mandibular areas were statistically compared. Results: At 8 weeks, all implants were integrated and there were no major postoperative complications. A statistically significant difference was found only at baseline between test and control maxillary implants (p=0.009 but not at 6 or 8 weeks (p>0.05. Conclusion: Immediate loading procedures may be applied with primary stability ISQ values >60 and inserted with a force of ≥30 N. The Osstell Mentor RFA may offer an objective method to determine when implant stability is adequate for immediate loading.

  13. Performance improvement of silicon nitride ball bearings by ion implantation. CRADA final report

    International Nuclear Information System (INIS)

    Williams, J.M.; Miner, J.

    1998-01-01

    The present report summarizes technical results of CRADA No. ORNL 92-128 with the Pratt and Whitney Division of United Technologies Corporation. The stated purpose of the program was to assess the 3effect of ion implantation on the rolling contact performance of engineering silicon nitride bearings, to determine by post-test analyses of the bearings the reasons for improved or reduced performance and the mechanisms of failure, if applicable, and to relate the overall results to basic property changes including but not limited to swelling, hardness, modulus, micromechanical properties, and surface morphology. Forty-two control samples were tested to an intended runout period of 60 h. It was possible to supply only six balls for ion implantation, but an extended test period goal of 150 h was used. The balls were implanted with C-ions at 150 keV to a fluence of 1.1 x 10 17 /cm 2 . The collection of samples had pre-existing defects called C-cracks in the surfaces. As a result, seven of the control samples had severe spalls before reaching the goal of 60 h for an unacceptable failure rate of 0.003/sample-h. None of the ion-implanted samples experienced engineering failure in 150 h of testing. Analytical techniques have been used to characterize ion implantation results, to characterize wear tracks, and to characterize microstructure and impurity content. In possible relation to C-cracks. It is encouraging that ion implantation can mitigate the C-crack failure mode. However, the practical implications are compromised by the fact that bearings with C-cracks would, in no case, be acceptable in engineering practice, as this type of defect was not anticipated when the program was designed. The most important reason for the use of ceramic bearings is energy efficiency

  14. Influence of immediate loading on provisional restoration in dental implant stability

    Science.gov (United States)

    Ikbal, M.; Odang, R. W.; Indrasari, M.; Dewi, R. S.

    2017-08-01

    The success of dental implant treatment is determined by the primary stability at placement. One factor that could influence this stability is occlusal loading through provisional restoration. Two types of loading protocols are usually used: immediate and delayed loading. However, some controversies remain about the influence of occlusal loading on implant stability. Therefore, the influence of immediate loading on implant stability must be studied. An animal study was conducted by placing nine dental implants in the mandibular jaw of three Macaca fascicularis. Provisional restorations with various occlusal contacts (no, light, and normal contact) were placed on the implant. The implant stability was measured using the Ostell ISQ three times: immediately (baseline) and at the first and second months after implant placement. The implant stability between implants with no and normal occlusal contact as well as light and normal occlusal contact showed significant differences (p implant placement. However, no significant increase (p > 0.05) in implant stability was seen at the baseline and the first and second months after implant placement for all occlusal contact groups. Immediate loading influenced the implant stability, and provisional restoration of implant without occlusal contact showed the highest implant stability.

  15. Effect of cyclic load on vertical misfit of prefabricated and cast implant single abutment

    OpenAIRE

    de Jesus Tavarez, Rudys Rodolfo; Bonachela, Wellington Cardoso; Xible, Anuar Antônio

    2011-01-01

    OBJECTIVES: The purpose of this in vitro study was to evaluate misfit alterations at the implant/abutment interface of external and internal connection implant systems when subjected to cyclic loading. MATERIAL AND METHODS: Standard metal crowns were fabricated for 5 groups (n=10) of implant/abutment assemblies: Group 1, external hexagon implant and UCLA cast-on premachined abutment; Group 2, internal hexagon implant and premachined abutment; Group 3, internal octagon implant and prefabricate...

  16. Immediate loading of subcrestally placed dental implants in anterior and premolar sites.

    Science.gov (United States)

    Henningsen, Anders; Smeets, Ralf; Köppen, Kai; Sehner, Susanne; Kornmann, Frank; Gröbe, Alexander; Heiland, Max; Gerlach, Till

    2017-11-01

    Immediate loading of dental implants has been evolving into an appropriate procedure for the treatment of partially edentulous jaws. The purpose of this study was to evaluate the clinical success and radiological outcome of immediately and delayed loaded dental implants in anterior and premolar sites. In this retrospective study, data of 163 individuals requiring tooth removal with subsequent implant placement in anterior and premolar sites were analyzed. Implants were immediately loaded by provisional acrylic resin bridges or loaded with delay. Implants were followed up annually for up to 9 years including intraoral radiographs. A total of 285 implants in 163 patients were placed. 218 implants were immediately loaded and 67 implants with delay. Fifteen implants failed during the follow-up period resulting in survival rates of 94.5% for immediate loading and 95.5% for delayed loading. After an initial decrease of 0.3 mm in the first 12 months the marginal bone level remained stable. No statistically significant differences were found in marginal bone loss between immediately and delayed loaded implants (P = 0.518, 95% CI). Within the limits of this study, immediate loading of immediately subcrestally placed dental implants in anterior and premolar sites is a reliable treatment option for dental rehabilitation. Copyright © 2017 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

  17. Feasibility of Applying Active Lubrication to Dynamically Loaded Fluid Film Bearings

    DEFF Research Database (Denmark)

    Estupinan, Edgar Alberto; Santos, Ilmar

    2009-01-01

    The feasibility of modifying the dynamics of the thin fluid films of dynamically loaded journal bearings, using different strategies of active lubrication is studied in this work. A significant reduction in the vibration levels, wear and power friction losses, is expected. Particularly, the focus...... of this study is on the analysis of main crankshaft bearings, where the conventional hydrodynamic lubrication is modified by injecting oil at actively controllable pressures, through orifices circumferentially located along the bearing surface....

  18. Effect of carbon ion implantation on the tribology of metal-on-metal bearings for artificial joints

    Directory of Open Access Journals (Sweden)

    Koseki H

    2017-05-01

    Full Text Available Hironobu Koseki,1 Masato Tomita,2 Akihiko Yonekura,2 Takashi Higuchi,1 Sinya Sunagawa,2 Koumei Baba,3,4 Makoto Osaki2 1Department of Locomotive Rehabilitation Science, Unit of Rehabilitation Sciences, 2Department of Orthopedic Surgery, Nagasaki University Graduate School of Biomedical Sciences, Sakamoto, Nagasaki, Japan; 3Industrial Technology Center of Nagasaki, Ikeda, Omura, Nagasaki, Japan; 4Affiliated Division, Nagasaki University School of Engineering, Bunkyo, Nagasaki, Japan Abstract: Metal-on-metal (MoM bearings have become popular due to a major advantage over metal-on-polymer bearings for total hip arthroplasty in that the larger femoral head and hydrodynamic lubrication of the former reduce the rate of wear. However, concerns remain regarding adverse reactions to metal debris including metallosis caused by metal wear generated at the taper-head interface and another modular junction. Our group has hypothesized that carbon ion implantation (CII may improve metal wear properties. The purpose of this study was to investigate the wear properties and friction coefficients of CII surfaces with an aim to ultimately apply these surfaces to MoM bearings in artificial joints. CII was applied to cobalt-chromium-molybdenum (Co-Cr-Mo alloy substrates by plasma source ion implantation. The substrates were characterized using scanning electron microscopy and a 3D measuring laser microscope. Sliding contact tests were performed with a simple geometry pin-on-plate wear tester at a load of 2.5 N, a calculated contact pressure of 38.5 MPa (max: 57.8 MPa, a reciprocating velocity of 30 mm/s, a stroke length of 60 mm, and a reciprocating cycle count of 172,800 cycles. The surfaces of the CII substrates were generally featureless with a smooth surface topography at the same level as untreated Co-Cr-Mo alloy. Compared to the untreated Co-Cr-Mo alloy, the CII-treated bearings had lower friction coefficients, higher resistance to catastrophic damage, and

  19. Nondestructive determination of the load bearing capacity of rigid pavement structures. Zerstoerungsfreie Tragfaehigkeitsbestimmung fuer starre Deckenkonstruktionen

    Energy Technology Data Exchange (ETDEWEB)

    Heinrich, U. (Bauakademie, IHLGB, Berlin (Germany))

    1991-01-01

    Actual parameters of the bearing capacity of traffic areas are in case of intensive use an indispensable necessity for the determination of the remaining use value with the aim to optimize reinforcing layers and reconstruction periods. Until now there is only one adequate measuring method for flexible layers. With the Rollig load test (RLT) initial data can be gained for the calculation of the load bearing capacity of rigid pavement structures. The method is described with the example of an airplane runway. (BWI).

  20. Immediate loading of titanium hexed screw-type implants in the edentulous patient: case report.

    Science.gov (United States)

    Calvo, M P; Muller, E; Garg, A K

    2000-01-01

    Histologic and histomorphometric studies in both animals and humans have shown that more rapid and greater bone-to-implant contact can be achieved with implants that incorporate certain surface characteristics compared with the original machined-surface implants. Such findings are significant because various implant designs may allow the fixtures to sufficiently resist functional loading sooner than originally thought. The case report presented here indicates that immediate loading of hexed titanium screw-type implants in the anterior mandible can lead to successful osseointegration and clinical outcome. The number of implants placed, their distribution, and the type of rigid connection are critical considerations for immediate loading. A bone height that can accommodate dental implants > or = 10 mm long is recommended. Biomechanically, the implants to be immediately loaded must be stable and resistant to macromovement to ensure good osseointegration.

  1. In-vivo orthopedic implant diagnostic device for sensing load, wear, and infection

    Science.gov (United States)

    Evans, III, Boyd McCutchen; Thundat, Thomas G.; Komistek, Richard D.; Dennis, Douglas A.; Mahfouz, Mohamed

    2006-08-29

    A device for providing in vivo diagnostics of loads, wear, and infection in orthopedic implants having at least one load sensor associated with the implant, at least one temperature sensor associated with the implant, at least one vibration sensor associated with the implant, and at least one signal processing device operatively coupled with the sensors. The signal processing device is operable to receive the output signal from the sensors and transmit a signal corresponding with the output signal.

  2. Progressive immediate loading of a perforated maxillary sinus dental implant: a case report

    Directory of Open Access Journals (Sweden)

    Al-Juboori MJ

    2015-01-01

    Full Text Available Mohammed Jasim Al-Juboori Department of Oral Surgery, MAHSA University, Kuala Lumpur, Malaysia Abstract: The displacement of a dental implant into the maxillary sinus may lead to implant failure due to exposure of the apical third or the tip of the implant beyond the bone, resulting in soft tissue growth. This case report discusses dental implant placement in the upper first molar area with maxillary sinus involvement of approximately 2 mm. A new technique for progressive implant loading was used, involving immediately loaded implants with maxillary sinus perforation and low primary stability. Follow-up was performed with resonance frequency analysis and compared with an implant placed adjacent in the upper second premolar area using a conventional delayed loading protocol. Implants with maxillary sinus involvement showed increasing stability during the healing period. We found that progressive implant loading may be a safe technique for the placement of immediately loaded implants with maxillary sinus involvement. Keywords: progressive implant loading, resonance frequency analysis, implant stability, provisional crown, bone density, maxillary sinus

  3. Analysis of submerged implant towards mastication load using 3D finite element method (FEM)

    OpenAIRE

    Widia Hafsyah Sumarlina Ritonga; Janti Rusjanti; Nunung Rusminah; Aldilla Miranda; Tatacipta Dirgantara

    2016-01-01

    Introduction: The surgical procedure for implantation of a surgical implant comprising a stage for the implant design nonsubmerged and two stages for submerged. Submerged implant design often used in Faculty of Dentistry Universitas Padjadjaran because it is safer in achieving osseointegration. This study was conducted to evaluate the failure of dental implant based on location and the value of internal tensiones as well as supporting tissues when given mastication load by using the 3D Finite...

  4. Load-bearing evaluation of spinal posterior column by measuring surface strain from lumbar pedicles. An in vitro study.

    Science.gov (United States)

    Sun, Peidong; Zhao, Weidong; Bi, Zhenyu; Wu, Changfu; Ouyang, Jun

    2012-01-01

    An understanding of the load transfer within spinal posterior column of lumbar spine is necessary to determine the influence of mechanical factors on potential mechanisms of the motion-sparing implant such as artificial intervertebral disc and the dynamic spine stabilization systems. In this study, a new method has been developed for evaluating the load bearing of spinal posterior column by the surface strain of spinal pedicle response to the loading of spinal segment. Six cadaveric lumbar spine segments were biomechanically evaluated between levels L1 and L5 in intact condition and the strain gauges were pasted to an inferior surface of L2 pedicles. Multidirectional flexibility testing used the Panjabi testing protocol; pure moments for the intact condition with overall spinal motion and unconstrained intact moments of ±8 Nm were used for flexion-extension and lateral bending testing. High correlation coefficient (0.967-0.998) indicated a good agreement between the load of spinal segment and the surface strain of pedicle in all loading directions. Principal compressive strain could be observed in flexion direction and tensile strain in extension direction, respectively. In conclusion, the new method seems to be effective for evaluating posterior spinal column loads using pedicles' surface strain data collected during biomechanical testing of spine segments.

  5. Load bearing capacities and elastic-plastic behavior of reactor vessel internals

    International Nuclear Information System (INIS)

    Watanabe, Keita; Nagase, Ryuichi

    2017-01-01

    Radial Support Keys (RSKs) are installed at the bottom of Reactor Vessel Internal (RVI) of Pressurized Water Reactor (PWR) and fit into Core Support Lugs of Reactor Pressure Vessel (RPV). This structure provides reactor core horizontal support and transmits the loads between RVI and RPV. RSK is one of the critical parts of RVI from the view point of earthquake-proof safety. In order to assure the structural integrity of Nuclear Reactor in case of massive earthquake, load bearing capacities of RSK are confirmed by static loading tests with reduced-scale mockups. In addition, collapse loads of actual components calculated by Limit Analyses are conservative enough compared to the load bearing capacities confirmed by the test. Thus, the methodology to calculate collapse load by Limit Analysis is applicable to evaluation of structural integrity for RSK. (author)

  6. Effect of cyclic loading and retightening on reverse torque value in external and internal implants.

    Science.gov (United States)

    Cho, Woong-Rae; Huh, Yoon-Hyuk; Park, Chan-Jin; Cho, Lee-Ra

    2015-08-01

    The aim of this study was to evaluate the effect of cyclic loading and screw retightening on reverse torque value (RTV) in external and internal type implants. Cement-retained abutments were connected with 30 Ncm torque to external and internal type implants. Experimental groups were classified according to implant connection type and retightening/loading protocol. In groups with no retightening, RTV was evaluated after cyclic loading for 100,000 cycles. In groups with retightening, RTV was measured after 3, 10, 100 cycles as well as every 20,000 cycles until 100,000 cycles of loading. Every group showed decreased RTV after cyclic loading. Before and after cyclic loading, external type implants had significantly higher RTVs than internal type implants. In external type implants, retightening did not affect the decrease in RTV. In contrast, retightening 5 times and retightening after 10 cycles of dynamic loading was effective for maintaining RTV in internal type implants. Retightening of screws is more effective in internal type implants than external type implants. Retightening of screws is recommended in the early stage of functional loading.

  7. An instrumented implant for vertebral body replacement that measures loads in the anterior spinal column.

    Science.gov (United States)

    Rohlmann, Antonius; Gabel, Udo; Graichen, Friedmar; Bender, Alwina; Bergmann, Georg

    2007-06-01

    Realistic loads on a spinal implant are required among others for optimization of implant design and preclinical testing. In addition, such data may help to choose the optimal physiotherapy program for patients with such an implant and to evaluate the efficacy of aids like braces or crutches. Presently, no implant is available that can measure loads in the anterior spinal column during activities of daily life. Therefore, an implant instrumented for in vivo load measurement was developed for vertebral body replacement. The aim of this paper is to describe in detail a telemeterized implant that measures forces and moments acting on it. Six load sensors, a nine-channel telemetry unit and a coil for inductive power supply of the electronic circuits were integrated into a modified vertebral body replacement (Synex). The instrumented part of the implant is hermetically sealed. Patients are videotaped during measurements, and implant loads are displayed on and off line. The average accuracy of load measurement is better than 2% for force and 5% for moment components with reference to the maximum value of 3000 N and 20 Nm, respectively. The measuring implant described here will provide additional information on spinal loads.

  8. Random spectrum loading of dental implants: An alternative approach to functional performance assessment.

    Science.gov (United States)

    Shemtov-Yona, K; Rittel, D

    2016-09-01

    The fatigue performance of dental implants is usually assessed on the basis of cyclic S/N curves. This neither provides information on the anticipated service performance of the implant, nor does it allow for detailed comparisons between implants unless a thorough statistical analysis is performed, of the kind not currently required by certification standards. The notion of endurance limit is deemed to be of limited applicability, given unavoidable stress concentrations and random load excursions, that all characterize dental implants and their service conditions. We propose a completely different approach, based on random spectrum loading, as long used in aeronautical design. The implant is randomly loaded by a sequence of loads encompassing all load levels it would endure during its service life. This approach provides a quantitative and comparable estimate of its performance in terms of lifetime, based on the very fact that the implant will fracture sooner or later, instead of defining a fatigue endurance limit of limited practical application. Five commercial monolithic Ti-6Al-4V implants were tested under cyclic, and another 5 under spectrum loading conditions, at room temperature and dry air. The failure modes and fracture planes were identical for all implants. The approach is discussed, including its potential applications, for systematic, straightforward and reliable comparisons of various implant designs and environments, without the need for cumbersome statistical analyses. It is believed that spectrum loading can be considered for the generation of new standardization procedures and design applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Bone reactions adjacent to titanium implants subjected to static load. A study in the dog (I)

    DEFF Research Database (Denmark)

    Gotfredsen, K; Berglundh, T; Lindhe, J

    2001-01-01

    The aim of the study was to evaluate the effect of lateral static load induced by an expansion force on the bone/implant interface and adjacent peri-implant bone. In 3 beagle dogs, the 2nd, 3rd and 4th mandibular premolars were extracted bilaterally. Twelve weeks later 8 implants of the ITI Dental...... Implant System were placed in each dog. Crowns connected in pairs were screwed on the implants 12 weeks after implant installation. The connected crowns contained an orthodontic expansion screw yielding 4 loading units in each dog. Clinical registrations, standardized radiographs and fluorochrome labeling...... were carried out during the 24-week loading period. Biopsies were harvested and processed for ground sectioning. The sections were subjected to histological examination. No evident marginal bone loss was observed at either test or control sites. The bone density and the mineralized bone-to-implant...

  10. Dynamic load testing on the bearing capacity of prestressed tubular concrete piles in soft ground

    Science.gov (United States)

    Yu, Chuang; Liu, Songyu

    2008-11-01

    Dynamic load testing (DLT) is a high strain test method for assessing pile performance. The shaft capacity of a driven PTC (prestressed tubular concrete) pile in marine soft ground will vary with time after installation. The DLT method has been successfully transferred to the testing of prestressed pipe piles in marine soft clay of Lianyungang area in China. DLT is investigated to determine the ultimate bearing capacity of single pile at different period after pile installation. The ultimate bearing capacity of single pile was founded to increase more than 70% during the inventing 3 months, which demonstrate the time effect of rigid pile bearing capacity in marine soft ground. Furthermore, the skin friction and axial force along the pile shaft are presented as well, which present the load transfer mechanism of pipe pile in soft clay. It shows the economy and efficiency of DLT method compared to static load testing method.

  11. The Bearing Capacity of Strip Footings in Cohesionless Soil Subject to Eccentric and Inclined Loads

    DEFF Research Database (Denmark)

    Krabbenhøft, Sven; Damkilde, Lars; Krabbenhøft, Kristian

    2014-01-01

    Lower bound calculations based on the finite element method is used to determine the bearing capacity of a strip foundation subjected to an inclined, eccentric load on cohesionless soil with varying surcharges and with friction angles 25, 30 and 35°. The soil is assumed perfectly plastic following...... the Mohr-Coulomb failure criterion. The results are reported as graphs showing the bearing capacity as a function of the friction angle, the eccentricity, inclination and the surcharge. The results have been compared with the Eurocode 7 and for smaller eccentricities, except in the case of no surcharge......, the lower bound values are the greater, the discrepancy increasing with growing surcharge. Positive load inclinations has a negative effect for smaller eccentricities but may have a beneficial effect on the bearing capacity for greater eccentricities. Negative load inclinations have the opposite effect...

  12. Stress Analysis and Fatigue Behaviour of PTFE-Bronze Layered Journal Bearing under Real-Time Dynamic Loading

    Science.gov (United States)

    Duman, M. S.; Kaplan, E.; Cuvalcı, O.

    2018-01-01

    The present paper is based on experimental studies and numerical simulations on the surface fatigue failure of the PTFE-bronze layered journal bearings under real-time loading. ‘Permaglide Plain Bearings P10’ type journal bearings were experimentally tested under different real time dynamic loadings by using real time journal bearing test system in our laboratory. The journal bearing consists of a PTFE-bronze layer approximately 0.32 mm thick on the steel support layer with 2.18 mm thick. Two different approaches have been considered with in experiments: (i) under real- time constant loading with varying bearing widths, (ii) under different real-time loadings at constant bearing widths. Fatigue regions, micro-crack dispersion and stress distributions occurred at the journal bearing were experimentally and theoretically investigated. The relation between fatigue region and pressure distributions were investigated by determining the circumferential pressure distribution under real-time dynamic loadings for the position of every 10° crank angles. In the theoretical part; stress and deformation distributions at the surface of the journal bearing analysed by using finite element methods to determine the relationship between stress and fatigue behaviour. As a result of this study, the maximum oil pressure and fatigue cracks were observed in the most heavily loaded regions of the bearing surface. Experimental results show that PTFE-Bronze layered journal bearings fatigue behaviour is better than the bearings include white metal alloy.

  13. Evaluation of Bearing Capacity of Strip Foundation Subjected to Eccentric Inclined Loads Using Finite Element Method

    Directory of Open Access Journals (Sweden)

    Ahmed Majeed Ali

    2016-08-01

    Full Text Available In real conditions of structures, foundations like retaining walls, industrial machines and platforms in offshore areas are commonly subjected to eccentrically inclined loads. This type of loading significantly affects the overall stability of shallow foundations due to exposing the foundation into two components of loads (horizontal and vertical and consequently reduces the bearing capacity Based on a numerical analysis performed using finite element software (Plaxis 3D Foundation, the behavior of model strip foundation rested on dry sand under the effect of eccentric inclined loads with different embedment ratios (D/B ranging from (0-1 has been explored. The results display that, the bearing capacity of strip foundation is noticeably decreased with the increase of inclination angle (α and eccentricity ratio (e/B. As well as, a reduction factor (RF expression was appointed to measure the degree of decreasing in the bearing capacity when the model footing is subjected to eccentric inclined load. It was observed that, the (RF decreases as the embedment ratio increases. Moreover, the test results also exhibit that, the model footing bearing capacity is reduced by about (69% when the load inclination is varied from (0° to 20° and the model footing is on the surface. While, the rate of decreasing in the bearing capacity was found to be (58%, for both cases of footing when they are at embedment ratios of (0.5 and 1.0. Also, a comparative study was carried out between the present results and previous experimental test results under the same conditions (soil properties and boundary condition. A good agreement was obtained between the predicted bearing capacities for the two related studies.

  14. Immediate non-occlusal loading of single implants in the aesthetic zone : A randomized clinical trial

    NARCIS (Netherlands)

    den Hartog, Laurens; Raghoebar, Gerry M.; Stellingsma, Kees; Vissink, Arjan; Meijer, Henny J. A.

    P>Aim This study compared the outcome of immediate non-occlusal loading with conventional loading for single implants in the maxillary aesthetic zone. It was hypothesized that immediate non-occlusal loading is not inferior to conventional loading. Materials and Methods Sixty-two patients with a

  15. Angular-contact ball-bearing internal load estimation algorithm using runtime adaptive relaxation

    Science.gov (United States)

    Medina, H.; Mutu, R.

    2017-07-01

    An algorithm to estimate internal loads for single-row angular contact ball bearings due to externally applied thrust loads and high-operating speeds is presented. A new runtime adaptive relaxation procedure and blending function is proposed which ensures algorithm stability whilst also reducing the number of iterations needed to reach convergence, leading to an average reduction in computation time in excess of approximately 80%. The model is validated based on a 218 angular contact bearing and shows excellent agreement compared to published results.

  16. Infrared Thermographic Diagnosis Mechanism for Fault Detection of Ball Bearing under Dynamic Loading Conditions

    International Nuclear Information System (INIS)

    Seo, Jin Ju; Yoon, Hanvit; Kim, Dong Yeon; Hong, Dong Pyo; Kim, Won Tae

    2011-01-01

    Fault detection for dynamic loading conditions of rotational machineries was considered from the contactless, non-destructive infrared thermographic method, rather than the traditional diagnosis method. In this paper, by applying a rotating deep-grooved ball bearing, passive thermographic experiment was performed as an alternative way proceeding the traditional fault monitoring. In addition, the thermographic experiments were compared with the vibration spectrum analysis to evaluate the efficiency of the proposed method. Based on the results, it was concluded the temperature characteristics of the ball bearing under dynamic loading conditions were analyzed thoroughly

  17. Implant loading protocols for edentulous patients with fixed prostheses: a systematic review and meta-analysis.

    Science.gov (United States)

    Papaspyridakos, Panos; Chen, Chun-Jung; Chuang, Sung-Kiang; Weber, Hans-Peter

    2014-01-01

    To report on the effect of immediate implant loading with fixed prostheses compared to early and conventional loading on implant and prosthesis survival, failure, and complications. An electronic and manual search was conducted to identify randomized controlled clinical trials (RCTs) as well as prospective and retrospective studies involving rough surface implants and implant fixed complete dental prostheses for edentulous patients. The 62 studies that fulfilled the inclusion criteria featured 4 RCTs, 2 prospective case-control studies, 34 prospective cohort studies, and 22 retrospective cohort studies. These studies yielded data from 2,695 patients (2,757 edentulous arches) with 13,653 implants. Studies were grouped according to the loading protocol applied; 45 studies reported on immediate loading, 8 on early loading, and 11 on conventional loading. For the immediate loading protocol with flap surgery, the implant and prosthesis survival rates ranged from 90.1% to 100% and 93.75% to 100%, respectively (range of follow-up, 1 to 10 years). When immediate loading was combined with guided flapless implant placement, the implant survival rates ranged from 90% to 99.4%. For the early loading protocol, the implant and prosthesis survival rates ranged from 94.74% to 100% and 93.75% to 100%, respectively (range of follow-up, 1 to 10 years). For the conventional loading protocol, the implant and prosthesis survival rates ranged from 94.95% to 100% and 87.5% to 100%, respectively (range of follow-up, 2 to 15 years). No difference was identified between maxilla and mandible. When selecting cases carefully and using dental implants with a rough surface, immediate loading with fixed prostheses in edentulous patients results in similar implant and prosthesis survival and failure rates as early and conventional loading. For immediate loading, most of the studies recommended a minimal insertion torque of 30 Ncm. The estimated 1-year implant survival was above 99% with all three

  18. Analysis of submerged implant towards mastication load using 3D finite element method (FEM

    Directory of Open Access Journals (Sweden)

    Widia Hafsyah Sumarlina Ritonga

    2016-11-01

    Full Text Available Introduction: The surgical procedure for implantation of a surgical implant comprising a stage for the implant design nonsubmerged and two stages for submerged. Submerged implant design often used in Faculty of Dentistry Universitas Padjadjaran because it is safer in achieving osseointegration. This study was conducted to evaluate the failure of dental implant based on location and the value of internal tensiones as well as supporting tissues when given mastication load by using the 3D Finite Element Method (FEM. Methods: This study used a photograph of the mandibular CBCT patient and CT Scan Micro one implant submerged. Radiograph image was then converted into a digital model of the 3D computerized finite element, inputted the material properties, pedestal, then simulated the occlusion load  as much as 87N and 29N of frictional Results: The maximum tension location on the implant was located on the  exact side of the contact area between the implant and alveolar crest. The maximum tension value was 193.31MPa on the implant body. The value was below the limit value of the ability of the titanium alloy to withstand fracture (860 MPa. Conclusion: The location of the maximum tension on the body of the implant was located on the exact contact area between the implant-abutment and alveolar crest. Under the mastication load, this implant design found no failure.

  19. Immediately loaded mini dental implants as overdenture retainers: 1-Year cohort study of implant stability and peri-implant marginal bone level.

    Science.gov (United States)

    Šćepanović, Miodrag; Todorović, Aleksandar; Marković, Aleksa; Patrnogić, Vesna; Miličić, Biljana; Moufti, Adel M; Mišić, Tijana

    2015-05-01

    This 1-year cohort study investigated stability and peri-implant marginal bone level of immediately loaded mini dental implants used to retain overdentures. Each of 30 edentulous patients received 4 mini dental implants (1.8 mm × 13 mm) in the interforaminal mandibular region. The implants were immediately loaded with pre-made overdentures. Outcome measures included implant stability and bone resorption. Implant stability was measured using the Periotest Classic(®) device immediately after placement and on the 3rd and 6th weeks and the 4th, 6th and 12th months postoperatively. The peri-implant marginal bone level (PIBL) was evaluated at the implant's mesial and distal sides from the polished platform to the marginal crest. Radiographs were taken using a tailored film holder to reproducibly position the X-ray tube at the 6th week, 4th and 12th months postoperatively. The primary stability (Periotest value, PTV) measured -0.27 ± 3.41 on a scale of -8 to + 50 (lower PTV reflects higher stability). The secondary stability decreased significantly until week 6 (mean PTV = 7.61 ± 7.05) then increased significantly reaching (PTV = 6.17 ± 6.15) at 12 months. The mean PIBL measured -0.40 mm after 1 year of functional loading, with no statistically significant differences at the various follow-ups (p = 0.218). Mini dental implants placed into the interforaminal region could achieve a favorable primary stability for immediate loading. The follow-up Periotest values fluctuated, apparently reflecting the dynamics of bone remodeling, with the implants remaining clinically stable (98.3%) after 1 year of function. The 1-year bone resorption around immediately loaded MDIs is within the clinically acceptable range for standard implants. Copyright © 2014 Elsevier GmbH. All rights reserved.

  20. Time Course of Peri-Implant Bone Regeneration around Loaded and Unloaded Implants in a Rat Model

    Science.gov (United States)

    Jariwala, Shailly H.; Wee, Hwabok; Roush, Evan P.; Whitcomb, Tiffany L.; Murter, Christopher; Kozlansky, Gery; Lakhtakia, Akhlesh; Kunselman, Allen R.; Donahue, Henry J.; Armstrong, April D.; Lewis, Gregory S.

    2018-01-01

    The time-course of cancellous bone regeneration surrounding mechanically loaded implants affects implant fixation, and is relevant to determining optimal rehabilitation protocols following orthopaedic surgeries. We investigated the influence of controlled mechanical loading of titanium-coated polyether-ether ketone (PEEK) implants on osseointegration using time-lapsed, non-invasive, in vivo micro-computed tomography (micro-CT) scans. Implants were inserted into proximal tibial metaphyses of both limbs of eight female Sprague-Dawley rats. External cyclic loading (60 μm or 100 μm displacement, 1 Hz, 60 seconds) was applied every other day for 14 days to one implant in each rat, while implants in contralateral limbs served as the unloaded controls. Hind limbs were imaged with high-resolution micro-CT (12.5 μm voxel size) at 2, 5, 9, and 12 days post-surgery. Trabecular changes over time were detected by 3D image registration allowing for measurements of bone-formation rate (BFR) and bone-resorption rate (BRR). At day 9, mean %BV/TV for loaded and unloaded limbs were 35.5 ± 10.0 % and 37.2 ± 10.0 %, respectively, and demonstrated significant increases in bone volume compared to day 2. BRR increased significantly after day 9. No significant differences between bone volumes, BFR, and BRR were detected due to implant loading. Although not reaching significance (p = 0.16), an average 119 % increase in pull-out strength was measured in the loaded implants. PMID:27381807

  1. Groundwater flux and nutrient loading in the northeast section of Bear Lake, Muskegon County, Michigan, 2015

    Science.gov (United States)

    Totten, Alexander R.; Maurer, Jessica A.; Duris, Joseph W.

    2017-11-30

    Bear Lake in North Muskegon, Michigan, is listed as part of the Muskegon Lake area of concern as designated by the U.S. Environmental Protection Agency. This area of concern was designated as a result of eutrophication and beneficial use impairments. On the northeast end of Bear Lake, two man-made retention ponds (Willbrandt Pond East and Willbrandt Pond West), formerly used for celery farming, may contribute nutrients to Bear Lake. Willbrandt Ponds (East and West) were previously muck fields that were actively used for celery farming from the early 1900s until 2002. The restoration and reconnection of the Willbrandt Ponds into Bear Lake prompted concerns of groundwater nutrient loading into Bear Lake. Studies done by the State of Michigan and Grand Valley State University revised initial internal phosphorus load estimates and indicated an imbalance in the phosphorus budget in Bear Lake. From June through November 2015, the U.S. Geological Survey (USGS) did an investigative study to quantify the load of nutrients from shallow groundwater around the Willbrandt Ponds in an effort to update the phosphorus budget to Bear Lake. Seven sampling locations were established, including five shallow groundwater wells and two surface-water sites, in the Willbrandt pond study area and Bear Lake. A total of 12 nutrient samples and discrete water-level measurements were collected from each site from June through November 2015. Continuous water-level data were recorded for both surface-water monitoring locations for the entire sampling period.Water-level data indicated that Willbrandt Pond West had the highest average water-level elevation of all sites monitored, which indicated the general direction of flux is from Willbrandt Pond West to Bear Lake. Nutrient and chloride loading from Willbrandt Pond West to Bear Lake was calculated using two distinct methods: Dupuit and direct seepage methods. Shallow groundwater loading calculations were determined by using groundwater levels to

  2. Advanced immediate functional loading: requirements for long-term success in modern implant dentistry.

    Science.gov (United States)

    Romanos, Georgios E

    2014-01-01

    There are benefits to be derived from the use of advanced surgical protocols in conjunction with immediate functional loading using various dental implant designs and implant-abutment connections. Clinical protocols with simultaneous bone grafting, immediate implant placement, and/or sinus augmentations when a shortened treatment period is needed are included in this report, with the aim of providing understanding of the main protocol characteristics and prerequisites for long-term success in implant dentistry. This article presents three clinical cases that illustrate possibilities for advanced immediate loading using different implant designs. It demonstrates treatment of severe bone defects and the facilitation of placing implants in regenerated bone that can be immediately loaded.

  3. Numerical assessment of bone remodeling around conventionally and early loaded titanium and titanium-zirconium alloy dental implants.

    Science.gov (United States)

    Akça, Kıvanç; Eser, Atılım; Çavuşoğlu, Yeliz; Sağırkaya, Elçin; Çehreli, Murat Cavit

    2015-05-01

    The aim of this study was to investigate conventionally and early loaded titanium and titanium-zirconium alloy implants by three-dimensional finite element stress analysis. Three-dimensional model of a dental implant was created and a thread area was established as a region of interest in trabecular bone to study a localized part of the global model with a refined mesh. The peri-implant tissues around conventionally loaded (model 1) and early loaded (model 2) implants were implemented and were used to explore principal stresses, displacement values, and equivalent strains in the peri-implant region of titanium and titanium-zirconium implants under static load of 300 N with or without 30° inclination applied on top of the abutment surface. Under axial loading, principal stresses in both models were comparable for both implants and models. Under oblique loading, principal stresses around titanium-zirconium implants were slightly higher in both models. Comparable stress magnitudes were observed in both models. The displacement values and equivalent strain amplitudes around both implants and models were similar. Peri-implant bone around titanium and titanium-zirconium implants experiences similar stress magnitudes coupled with intraosseous implant displacement values under conventional loading and early loading simulations. Titanium-zirconium implants have biomechanical outcome comparable to conventional titanium implants under conventional loading and early loading.

  4. Influence of the implant abutment types and the dynamic loading on initial screw loosening

    OpenAIRE

    Kim, Eun-Sook; Shin, Soo-Yeon

    2013-01-01

    PURPOSE This study examined the effects of the abutment types and dynamic loading on the stability of implant prostheses with three types of implant abutments prepared using different fabrication methods by measuring removal torque both before and after dynamic loading. MATERIALS AND METHODS Three groups of abutments were produced using different types of fabrication methods; stock abutment, gold cast abutment, and CAD/CAM custom abutment. A customized jig was fabricated to apply the load at ...

  5. Effect of cyclic load on vertical misfit of prefabricated and cast implant single abutment

    Science.gov (United States)

    DE JESUS TAVAREZ, Rudys Rodolfo; BONACHELA, Wellington Cardoso; XIBLE, Anuar Antônio

    2011-01-01

    Objective The purpose of this in vitro study was to evaluate misfit alterations at the implant/abutment interface of external and internal connection implant systems when subjected to cyclic loading. Material and Methods Standard metal crowns were fabricated for 5 groups (n=10) of implant/abutment assemblies: Group 1, external hexagon implant and UCLA cast-on premachined abutment; Group 2, internal hexagon implant and premachined abutment; Group 3, internal octagon implant and prefabricated abutment; Group 4, external hexagon implant and UCLA cast-on premachined abutment; and Group 5, external hexagon implant and Ceraone abutment. For groups 1, 2, 3 and 5, the crowns were cemented on the abutments and in group 4 crowns were screwed directly on the implant. The specimens were subjected to 500,000 cycles at 19.1 Hz of frequency and non-axial load of 133 N in a MTS 810 machine. The vertical misfit (μm) at the implant/abutment interface was evaluated before (B) and after (A) application of the cyclic loading. Data were analyzed statistically by using two-away ANOVA and Tukey’s post-hoc test (pabutment connection may develop a role on the vertical misfit at the implant/abutment interface. PMID:21437464

  6. Immediately loaded implants supporting fixed prostheses in the edentulous maxilla: a preliminary clinical and radiologic report.

    Science.gov (United States)

    Bergkvist, Göran; Sahlholm, Sten; Karlsson, Ulf; Nilner, Krister; Lindh, Christina

    2005-01-01

    To evaluate the survival rate of immediately loaded ITI sand-blasted, large-grit, acid-etched (SLA) solid-screw dental implants in the edentulous maxilla after 8 months of loading. Twenty-eight patients (mean age 63 years) with edentulous maxillae each received 6 implants and 1 implant-supported fixed provisional prosthesis within 24 hours after surgery. After a mean healing time of 15 weeks, the patient received a definitive, screw-retained, implant-supported fixed prosthesis. A total of 168 implants were placed. Clinical parameters were registered after 1 month of loading with the implant-supported fixed prostheses as well as 8 months after implant placement. Radiologic examinations and assessments were made at implant placement and after 8 months. The mean marginal bone level at implant placement was 1.6 mm (range 0 to 5.1; SD 1.1) apical of the reference point (the implant shoulder). The mean marginal bone level at the 8-month follow-up was 3.2 mm (range 0.4 to 5.9; SD 1.1) apical of the reference point. Three implants failed during the healing period. The improved results in the present study might be a result of the positive effect of splinting the implants immediately after placement. ITI SLA solid-screw implants immediately loaded (ie, loaded within 24 hours of placement) and supporting fixed prostheses had successful survival rates after 8 months. The present results constitute a solid baseline for future follow-up studies.

  7. Recent Steps Towards a Common Understanding of Ball Bearing Load Capacity

    Science.gov (United States)

    Lewis, Simon; Gaillard, Lionel; Seiler, René; Parzianello, Giorgio; LeLetty, Ronan

    2015-09-01

    This paper discusses the derivation and substantiation of the load capacity standards currently used to define the de-rating of ball bearings to provide appropriate margins for space applications. It is noted that European and U.S. standards affecting this issue differ, leading to discrepancies in claimed margins and perhaps to mass and performance disadvantages for mechanisms designed strictly in accordance with the present European standard. On the basis of empirical and experimental data, this paper proposes a potential route toward a harmonisation of the load capacity approach for ball bearings both between different international standards and between the separate ECSS standards on mechanisms and structures. The effect of such an approach on bearings and other tribological components intended for space applications is briefly reviewed.

  8. Curvilinear steel elements in load-bearing structures of high-rise building spatial frames

    Directory of Open Access Journals (Sweden)

    Ibragimov Alexander

    2018-01-01

    Full Text Available The application of curvilinear elements in load-bearing metal structures of high-rise buildings supposes ensuring of their bearing capacity and serviceability. There may exist a great variety of shapes and orientations of such structural elements. In particular, it may be various flat curves of an open or closed oval profile such as circular or parabolic arch or ellipse. The considered approach implies creating vast internal volumes without loss in the load-bearing capacity of the frame. The basic concept makes possible a wide variety of layout and design solutions. The presence of free internal spaces of large volume in "skyscraper" type buildings contributes to resolving a great number of problems, including those of communicative nature. The calculation results confirm the basic assumptions.

  9. Curvilinear steel elements in load-bearing structures of high-rise building spatial frames

    Science.gov (United States)

    Ibragimov, Alexander; Danilov, Alexander

    2018-03-01

    The application of curvilinear elements in load-bearing metal structures of high-rise buildings supposes ensuring of their bearing capacity and serviceability. There may exist a great variety of shapes and orientations of such structural elements. In particular, it may be various flat curves of an open or closed oval profile such as circular or parabolic arch or ellipse. The considered approach implies creating vast internal volumes without loss in the load-bearing capacity of the frame. The basic concept makes possible a wide variety of layout and design solutions. The presence of free internal spaces of large volume in "skyscraper" type buildings contributes to resolving a great number of problems, including those of communicative nature. The calculation results confirm the basic assumptions.

  10. Lower-Bound Calculations of the Bearing Capacity of Eccentrically Loaded Footings in Cohesionless Soil

    DEFF Research Database (Denmark)

    Krabbenhøft, Sven; Damkilde, Lars; Krabbenhøft, Kristian

    2012-01-01

    Lower-bound calculations based on the finite element method are used to determine the bearing capacity of a strip foundation subjected to a vertical, eccentric load on cohesionless soil with varying surcharges. The soil is assumed perfectly plastic following the Mohr-Coulomb failure criterion. Th...

  11. Nondimensional characterization and asymptotic model development for multifunctional structures with application to load-bearing antennas

    International Nuclear Information System (INIS)

    Santapuri, Sushma; Bechtel, Stephen E

    2014-01-01

    This paper (i) presents a mathematical approach to formulate leading-order models for complex multifunctional systems with coupled thermomechanical and electromagnetic field interactions, and (ii) demonstrates its applicability to the modeling and analysis of a load-bearing antenna, a multifunctional sensing and transmitting device integrated with a load-bearing structure. Starting from first-principle equations, i.e. the thermomechanical balance laws coupled with Maxwell’s equations, nondimensionalization and perturbation techniques are employed to formulate a leading-order model for the coupled system. Depending on the design of the structure and nature of the excitation, the nondimensional numbers arising in the coupled multifunctional system are quantified, and through a relative ordering of these quantities, the dominant physical effects are extracted. The resulting dominant effects determine the regime of operation of the structure, and in turn dictate the appropriate computational model. This approach is demonstrated through an application to a load-bearing antenna for a prototypical design. The resulting leading-order model is subsequently solved, and the electrical and structural response of the load-bearing antenna is analyzed and compared for different combinations of material properties. The framework introduced in this paper is envisioned to have applications in developing leading-order models for a wide range of complex multifunctional systems and can be utilized for their efficient design. (paper)

  12. Slim 198gold-grain implanter loaded with standard royal marsden 14-grain magazines

    International Nuclear Information System (INIS)

    Delclos, L.; Moore, E.B.

    1979-01-01

    We designed a slim gold-grain implanter with adaptable lengths to implant areas accessible only through long, narrow, examining instruments, such as a suspension laryngoscope. The implanter is loaded with the same 14-grain magazine designed for and supplied with the Royal Marsden gun. The simplicity of the loading mechanism with a minimum of moving parts makes the instrument practically trouble free. Although it is designed to be used along narrow examining instruments, it can also be used in any situation in which a permanent implant is required, for instance, prostatic cancer and pelvic recurrences in cancer of the uterine cervix previously treated by external and intracavitary irradiation

  13. Biomechanical optimization of implant diameter and length for immediate loading: a nonlinear finite element analysis.

    Science.gov (United States)

    Kong, Liang; Gu, Zexu; Li, Tao; Wu, Junjie; Hu, Kaijin; Liu, Yanpu; Zhou, Hongzhi; Liu, Baolin

    2009-01-01

    A nonlinear finite element method was applied to examine the effects of implant diameter and length on the maximum von Mises stresses in the jaw, and to evaluate the maximum displacement of the implant-abutment complex in immediate-loading models. The implant diameter (D) ranged from 3.0 to 5.0 mm and implant length (L) ranged from 6.0 to 16.0 mm. The results showed that the maximum von Mises stress in cortical bone was decreased by 65.8% under a buccolingual load with an increase in D. In cancellous bone, it was decreased by 71.5% under an axial load with an increase in L. The maximum displacement in the implant-abutment complex decreased by 64.8% under a buccolingual load with an increase in D. The implant was found to be more sensitive to L than to D under axial loads, while D played a more important role in enhancing its stability under buccolingual loads. When D exceeded 4.0 mm and L exceeded 11.0 mm, both minimum stress and displacement were obtained. Therefore, these dimensions were the optimal biomechanical selections for immediate-loading implants in type B/2 bone.

  14. Ældre betonbroers bæreevne (Load bearing capacity of old concrete bridges)

    DEFF Research Database (Denmark)

    Nielsen, Anders

    1999-01-01

    Two old bridges have been analysed in connection with their demolition. The first one is a pedestrian bridge, the Gefion bridge, from 1894. This is the first bridge of reinforced concrete in Denmark. Here the creep in the concrete severely have changed the way in which the load on the bridge was ...... was carried. - The other is a motor way bridge from 1939, which were reinforced 1991 with external steel plates on the areas of shear on the beams. Four beams were carried to our laboratory and load tested. The steel plates have doubled the load bearing capacity of the beams....

  15. Stålplader gav dobbelt bæreevne (Steel plates doubled the load bearing capacity)

    DEFF Research Database (Denmark)

    Nielsen, Jan Broch

    1999-01-01

    Abstract from an examination of motor road bridge beams reinforced with steel plates on the sides and bottom. The plates doubled the load bearing capacity of the beams.......Abstract from an examination of motor road bridge beams reinforced with steel plates on the sides and bottom. The plates doubled the load bearing capacity of the beams....

  16. Clinical evaluation of a novel dental implant system as single implants under immediate loading conditions - 4-month post-loading results from a multicentre randomised controlled trial.

    Science.gov (United States)

    Esposito, Marco; Trullenque-Eriksson, Anna; Blasone, Rodolfo; Malaguti, Giuliano; Gaffuri, Cristiano; Caneva, Marco; Minciarelli, Armando; Luongo, Giuseppe

    To evaluate the safety and clinical effectiveness of a novel dental implant system (GENESIS Implant System, Keystone Dental, Massachusetts, USA) using another dental implant system by the same manufacturer as a control (PRIMA Implant System, Keystone Dental). A total of 53 patients requiring at least two single crowns had their sites randomised according to a split-mouth design to receive both implant systems at six centres. If implants could be placed with a torque superior to 40 Ncm they were to be loaded immediately with provisional crowns, otherwise after 3 months of submerged healing. Provisional crowns were replaced by definitive crowns 4 months after initial loading, when the follow-up period for the initial part of this study was completed. Outcome measures were crown/implant failures, complications, pink esthetic score (PES), peri-implant marginal bone level changes, plaque score, marginal bleeding, patients and preference of the clinician. In total 53 PRIMA and 53 GENESIS implants were placed. Three patients dropped out but all of the remaining patients were followed up to 4-months post-loading. No PRIMA implant failed whereas four GENESIS implants failed. Only two complications were reported for PRIMA implants. There were no statistically significant differences for crown/implant failures (difference in proportions = 0.080; P (McNemar test) = 0.125) and complications (difference in proportions = -0.04; P (McNemar test) = 0.500) between the implant systems. There were no differences at 4-months post-loading for plaque (difference = -0.54, 95% CI: -3.01 to 1.93; P (Paired t-test) = 0.660), marginal bleeding (difference = -3.8, 95% CI: -7.63 to 0.019; P (Paired t-test) = 0.051), PES (difference = 0.47, 95% CI: -0.56 to 1.50; P (Paired t-test) = 0.365) and marginal bone level changes (difference in mm = -0.04, 95% CI: -0.33 to 0.26; P (Paired t-test) = 0.795). The majority of the patients (46) had no

  17. Carga inmediata con implantes en maxilar superior Immediate loading of implants in the maxilla

    Directory of Open Access Journals (Sweden)

    F. Monje Gil

    2007-08-01

    Full Text Available La carga inmediata en la mandíbula se ha incorporado a la práctica clínica en primer lugar y, por las características del hueso, se realiza de forma protocolizada. Sin embargo, en el maxilar superior no hay evidencia científica para realizarlo de forma cotidiana. Las razones son debidas a que el maxilar superior, en general, alberga una masa ósea de menor densidad. Por otro lado, en el maxilar superior pueden coexistir diferentes densidades óseas (según la clasificación de Misch en el mismo individuo. Además, por las características anatómicas del maxilar superior (reabsorción labiopalatina el alineamiento axial es asumible pero, sin embargo, el paralelismo de los implantes es difícil.16,17 El objetivo del presente trabajo es analizar la información científica de la que disponemos para confirmar si es posible la carga inmediata sobre el maxilar superior. Para ello estudiaremos varios aspectos de la carga inmediata en el maxilar superior: • Sobredentaduras • Prótesis fija completa • Prótesis parcial fija • Prótesis unitaria fija • Requerimientos protésicos • ContraindicacionesImmediate loading in the mandible has been introduced into clinical practice taking first place and, and because of the characteristics of the bone, this is carried out following a protocol. However, in the maxilla there is no scientific evidence for routinely carrying this out. This is because the maxilla, in general, has a lower bone mass density. Moreover, in the maxilla various densities may coexist (according to Misch’s classification in the same individual. In addition, given the anatomic characteristics of the maxilla (lip and palate resorption, axial alignment can be carried out, but implant parallelism is difficult.16,17 The aim of this paper is to analyze the scientific information that we have at our disposal in order to confirm whether immediate loading in the maxilla is possible. For this we will study various aspects of

  18. Esthetic Outcomes of Immediately Loaded Locking Taper Implants in the Anterior Maxilla: A Case Series Study.

    Science.gov (United States)

    Lombardo, Giorgio; Corrocher, Giovanni; Pighi, Jacopo; Mascellaro, Anna; Marincola, Mauro; Nocini, Per Francesco

    2016-06-01

    The purpose of this study was to evaluate the esthetic outcome of single-tooth locking taper connection implants placed in the anterior maxilla following a postextractive nonfunctional loading protocol. This preliminary clinical study involving 16 patients evaluated the results of 21 implants placed in areas with high esthetic value. For each implant the pink esthetic score, white esthetic score, cumulative survival rate, and health status of peri-implant tissues were evaluated. The cumulative survival rate was 100% 2 years after prosthetic loading, and the mean total pink esthetic score/white esthetic score was 16.9 ± 1.14 on a maximum value of 20. There was excellent plaque control in all patients, and inflammation indices were within the norm. Within the limits of this study, this immediate nonfunctional loading protocol seems to be a successful procedure esthetically and for the maintenance of peri-implant soft tissues.

  19. Ultimate design load analysis of planetary gearbox bearings under extreme events

    DEFF Research Database (Denmark)

    Gallego Calderon, Juan Felipe; Natarajan, Anand; Cutululis, Nicolaos Antonio

    2017-01-01

    This paper investigates the impact of extreme events on the planet bearings of a 5 MW gearbox. The system is simulated using an aeroelastic tool, where the turbine structure is modeled, and MATLAB/Simulink, where the drivetrain (gearbox and generator) are modeled using a lumped-parameter approach....... Three extreme events are assessed: low-voltage ride through, emergency stop and normal stop. The analysis is focused on finding which event has the most negative impact on the bearing extreme radial loads. The two latter events are carried out following the guidelines of the International...

  20. Effect of radial head implant shape on joint contact area and location during static loading.

    Science.gov (United States)

    Shannon, Hannah L; Deluce, Simon R; Lalone, Emily A; Willing, Ryan; King, Graham J W; Johnson, James A

    2015-04-01

    To examine the effect of implant shape on radiocapitellar joint contact area and location in vitro. We used 8 fresh-frozen cadaveric upper extremities. An elbow loading simulator examined joint contact in pronation, neutral rotation, and supination with the elbow at 90° flexion. Muscle tendons were attached to pneumatic actuators to allow for computer-controlled loading to achieve the desired forearm rotation. We performed testing with the native radial head, an axisymmetric implant, a reverse-engineered patient-specific implant, and a population-based quasi-anatomic implant. Implants were inserted using computer navigation. Contact area and location were quantified using a casting technique. We found no significant difference between contact locations for the native radial head and the 3 implants. All of the implants had a contact area lower than the native radial head; however, only the axisymmetric implant was significantly different. There was no significant difference in contact area between implant shapes. The similar contact areas and locations of the 3 implant designs suggest that the shape of the implant may not be important with respect to radiocapitellar joint contact mechanics when placed optimally using computer navigation. Further work is needed to explore the sensitivity of radial head implant malpositioning on articular contact. The lower contact area of the radial head implants relative to the native radial head is similar to previous benchtop studies and is likely the result of the greater stiffness of the implant. Radial head implant shape does not appear to have a pronounced influence on articular contact, and both axisymmetric and anatomic metal designs result in elevated cartilage stress relative to the intact state. Copyright © 2015 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

  1. Biomechanical implant treatment complications: a systematic review of clinical studies of implants with at least 1 year of functional loading.

    Science.gov (United States)

    Hsu, Yung-Ting; Fu, Jia-Hui; Al-Hezaimi, Khalid; Wang, Hom-Lay

    2012-01-01

    The aim of this article is to discuss the current literature available on the etiology and management of biomechanical complications of dental implant treatment. An electronic search of the PubMed database for English-language articles published before May 31, 2011, was performed based on a focus question: "How can biomechanical implant treatment complications be managed and identified?" The key words used were "dental implant," "etiology," "management," "excessive occlusal forces," "occlusal forces," "occlusion," "parafunctional habits," "biomechanical failure," "biomechanical complications," and "occlusal overloading." Clinical trials with a minimum of 10 implants followed for at least 1 year after functional loading were included. The initial electronic search identified 2,087 publications, most of which were eliminated, as they were animal studies, finite element analyses, bench-top studies, case reports, and literature reviews. After the titles, abstracts, and full text of 39 potentially eligible publications were reviewed, 15 studies were found to fulfill the inclusion criteria. Occlusal overloading was thought to be the primary etiologic factor in biomechanical implant treatment complications, which commonly included marginal bone loss, fracture of resin/ceramic veneers and porcelain, retention device or denture base fracture of implant-supported overdentures, loosening or fracture of abutment screws, and even implant failure. Occlusal overloading was positively associated with parafunctional habits such as bruxism. An appreciation of the intricacy of implant occlusion would allow clinicians to take a more preventive approach when performing implant treatment planning, as avoidance of implant overloading helps to ensure the long-term stability of implant-supported prostheses.

  2. BEARING CAPACITY OF A HORIZONTALLY LOADED SINGLE PILE SUPPORT WITH SLEEPERS

    Directory of Open Access Journals (Sweden)

    Buslov Anatoliy Semenovich

    2015-09-01

    Full Text Available The supports of a overhead wiring used in transport take up substantial loads both because of wires and constructions holding them and wind, dynamic and other extraordinary impacts. In case of using single-member piles a question about their stability appears. For this reason different sleepers constructions are used. In order to improve the bearing capacity of horizontally loaded single pile supports of the contact systems used in urban, road and rail transport, power lines, etc.., it is recommended to use sleepers as horizontally laid under the ground in the depth of support beams. The calculation methods for different support sleepers of different lengths and cross sections are not well investigated. The proposed calculation method allows determining the carrying capacity of horizontally loaded bearings with soil pieces of different structural dimensions and their location in the soil, which allows choosing the best option for cost and material consumption. The calculations offered by the authors prove the efficiency of sleepers use in order to increase the bearing capacity of horizontally loaded piles and the possibility to chose their size.

  3. Residual gentamicin-release from antibiotic-loaded polymethylmethacrylate beads after 5 years of implantation

    NARCIS (Netherlands)

    Neut, D; van de Belt, H; van Horn, [No Value; van der Mei, HC; Busscher, HJ

    In infected joint arthroplasty, high local levels of antibiotics are achieved through temporary implantation of non-biodegradable gentamicin-loaded polymethylmethacrylate beads. Despite their antibiotic release, these beads act as a biomaterial surface to which bacteria preferentially adhere, grow

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

    Science.gov (United States)

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

    2016-02-01

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

  5. Load Transfer Characteristics of Three-Implant-Retained Overdentures with Different Interimplant Distances.

    Science.gov (United States)

    Tokar, Emre; Uludag, Bulent; Karacaer, Ozgul

    Implant-retained overdentures are the first choice of rehabilitation for edentulous mandibles. Bone morphology and anatomical landmarks may be influenced by the location and angulation of implants and distances between the implants. The purpose of this study was to investigate stress distribution characteristics and to compare stress levels of three different attachment designs of three-implant-retained mandibular overdentures with three different interimplant distances. Three photoelastic mandibular models with three implants were fabricated using an edentulous mandible cast with moderate residual ridge resorption. The center implants were embedded parallel to the midline, and the distal implants were aligned at a 20-degree angulation corresponding to the center implants. Distances between the center and distal implants were set at 11, 18, and 25 mm at the photoelastic models. Bar, bar-ball, and Locator attachment-retained overdentures were prepared for the models. Vertical loads were applied to the overdentures, and stress levels and distribution were evaluated by a circular polariscope. The greatest observed stress level was moderate for the tested overdenture designs. The Locator attachment system showed the lowest stress level for the 11-mm and 25-mm photoelastic models. The bar attachment design transmitted less stress compared with the other tested designs for the 18-mm photoelastic model. Stresses were observed on the loaded side of the photoelastic models. The lowest stress was found with the Locator and bar attachments for the 11-mm photoelastic model, which transmitted little or no discernible stress around the implants.

  6. Biomechanics and strain mapping in bone as related to immediately-loaded dental implants

    Science.gov (United States)

    Du, Jing; Lee, Jihyun; Jang, Andrew; Gu, Allen; Hossaini-Zadeh, Mehran; Prevost, Richard; Curtis, Don; Ho, Sunita

    2015-01-01

    The effects of alveolar bone socket geometry and bone-implant contact on implant biomechanics, and resulting strain distributions in bone were investigated. Following extraction of lateral incisors on a cadaver mandible, immediate implants were placed and bone-implant contact area, stability and bone strain were measured. In situ biomechanical testing coupled with micro X-ray microscope (μ-XRM) illustrated less stiff bone-implant complexes (701-822 N/mm) compared with bone-periodontal ligament (PDL)-tooth complexes (791-913 N/mm). X-ray tomograms illustrated that the cause of reduced stiffness was due to reduced and limited bone-implant contact. Heterogeneous elemental composition of bone was identified by using energy dispersive X-ray spectroscopy (EDS). The novel aspect of this study was the application of a new experimental mechanics method, that is, digital volume correlation, which allowed mapping of strains in volumes of alveolar bone in contact with a loaded implant. The identified surface and subsurface strain concentrations were a manifestation of load transferred to bone through bone-implant contact based on bone-implant geometry, quality of bone, implant placement, and implant design. 3D strain mapping indicated that strain concentrations are not exclusive to the bone-implant contact regions, but also extend into bone not directly in contact with the implant. The implications of the observed strain concentrations are discussed in the context of mechanobiology. Although a plausible explanation of surgical complications for immediate implant treatment is provided, extrapolation of results is only warranted by future systematic studies on more cadaver specimens and/or in vivo small scale animal models. PMID:26162549

  7. Study on Load-Bearing Characteristics of a New Pile Group Foundation for an Offshore Wind Turbine

    Directory of Open Access Journals (Sweden)

    Ruiqing Lang

    2014-01-01

    Full Text Available Because offshore wind turbines are high-rise structures, they transfer large horizontal loads and moments to their foundations. One of the keys to designing a foundation is determining the sensitivities and laws affecting its load-bearing capacity. In this study, this procedure was carried out for a new high-rise cap pile group foundation adapted to the loading characteristics of offshore wind turbines. The sensitivities of influential factors affecting the bearing properties were determined using an orthogonal test. Through a combination of numerical simulations and model tests, the effects of the inclination angle, length, diameter, and number of side piles on the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity were determined. The results indicate that an increase in the inclination angle of the side piles will increase the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity. An increase in the length of the side piles will increase the vertical bearing capacity and bending bearing capacity. When the length of the side piles is close to the central pile, the increase is more apparent. Finally, increasing the number of piles will increase the horizontal bearing capacity; however, the growth rate is small because of the pile group effect.

  8. Study on load-bearing characteristics of a new pile group foundation for an offshore wind turbine.

    Science.gov (United States)

    Lang, Ruiqing; Liu, Run; Lian, Jijian; Ding, Hongyan

    2014-01-01

    Because offshore wind turbines are high-rise structures, they transfer large horizontal loads and moments to their foundations. One of the keys to designing a foundation is determining the sensitivities and laws affecting its load-bearing capacity. In this study, this procedure was carried out for a new high-rise cap pile group foundation adapted to the loading characteristics of offshore wind turbines. The sensitivities of influential factors affecting the bearing properties were determined using an orthogonal test. Through a combination of numerical simulations and model tests, the effects of the inclination angle, length, diameter, and number of side piles on the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity were determined. The results indicate that an increase in the inclination angle of the side piles will increase the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity. An increase in the length of the side piles will increase the vertical bearing capacity and bending bearing capacity. When the length of the side piles is close to the central pile, the increase is more apparent. Finally, increasing the number of piles will increase the horizontal bearing capacity; however, the growth rate is small because of the pile group effect.

  9. Study on Load-Bearing Characteristics of a New Pile Group Foundation for an Offshore Wind Turbine

    Science.gov (United States)

    Liu, Run; Lian, Jijian; Ding, Hongyan

    2014-01-01

    Because offshore wind turbines are high-rise structures, they transfer large horizontal loads and moments to their foundations. One of the keys to designing a foundation is determining the sensitivities and laws affecting its load-bearing capacity. In this study, this procedure was carried out for a new high-rise cap pile group foundation adapted to the loading characteristics of offshore wind turbines. The sensitivities of influential factors affecting the bearing properties were determined using an orthogonal test. Through a combination of numerical simulations and model tests, the effects of the inclination angle, length, diameter, and number of side piles on the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity were determined. The results indicate that an increase in the inclination angle of the side piles will increase the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity. An increase in the length of the side piles will increase the vertical bearing capacity and bending bearing capacity. When the length of the side piles is close to the central pile, the increase is more apparent. Finally, increasing the number of piles will increase the horizontal bearing capacity; however, the growth rate is small because of the pile group effect. PMID:25250375

  10. On load paths and load bearing topology from finite element analysis

    International Nuclear Information System (INIS)

    Kelly, D; Reidsema, C; Lee, M

    2010-01-01

    Load paths can be mapped from vector plots of 'pointing stress vectors'. They define a path along which a component of load remains constant as it traverses the solution domain. In this paper the theory for the paths is first defined. Properties of the plots that enable a designer to interpret the structural behavior from the contours are then identified. Because stress is a second order tensor defined on an orthogonal set of axes, the vector plots define separate paths for load transfer in each direction of the set of axes. An algorithm is therefore presented that combines the vectors to define a topology to carry the loads. The algorithm is shown to straighten the paths reducing bending moments and removing stress concentration. Application to a bolted joint, a racing car body and a yacht hull demonstrate the usefulness of the plots.

  11. Assessment of Embedded Conjugated Polymer Sensor Arrays for Potential Load Transmission Measurement in Orthopaedic Implants

    Directory of Open Access Journals (Sweden)

    Carolina Micolini

    2017-11-01

    Full Text Available Load transfer through orthopaedic joint implants is poorly understood. The longer-term outcomes of these implants are just starting to be studied, making it imperative to monitor contact loads across the entire joint implant interface to elucidate the force transmission and distribution mechanisms exhibited by these implants in service. This study proposes and demonstrates the design, implementation, and characterization of a 3D-printed smart polymer sensor array using conductive polyaniline (PANI structures embedded within a polymeric parent phase. The piezoresistive characteristics of PANI were investigated to characterize the sensing behaviour inherent to these embedded pressure sensor arrays, including the experimental determination of the stable response of PANI to continuous loading, stability throughout the course of loading and unloading cycles, and finally sensor repeatability and linearity in response to incremental loading cycles. This specially developed multi-material additive manufacturing process for PANI is shown be an attractive approach for the fabrication of implant components having embedded smart-polymer sensors, which could ultimately be employed for the measurement and analysis of joint loads in orthopaedic implants for in vitro testing.

  12. Mechanical stability of immediately loaded implants with various surfaces and designs: a pilot study in dogs.

    Science.gov (United States)

    Neugebauer, Jörg; Weinländer, Michael; Lekovic, Vojislav; von Berg, Karl-Heinz Linne; Zoeller, Joachim E

    2009-01-01

    Immediate loading is among the most innovative techniques in implant therapy today. This pilot study investigates the biomechanical outcome of various designs and surfaces that claim to shorten implant treatment. In each quadrant of two mongrel dogs, four different implants were used for immediate loading. The following implants were placed 3 months after tooth extraction: screw with low thread profile and anodic oxidized surface (LPAOS), solid screw with wide thread profile and titanium plasma spray coating (WPTPS), screw with low profile and hybrid design of double-etched and machined surface (LPHES), and screw with two thread profiles and a sandblasted and acid-etched surface (DTSAE). The insertion torque of each implant was above 35 Ncm. Resonance frequency analysis was performed after implant placement and again after sacrifice. Additionally, the removal torque and the amount of embedded titanium particles in the peri-implant bone were measured. All 16 prostheses were functional after a 5-month loading period. The highest mean removal torque values were recorded with WPTPS implants (24.4 Ncm/mm), followed by DTSAE implants (22.3 Ncm/mm) and LPAOS implants (18.7 Ncm/mm); the lowest score was obtained by LPHES (12.0 Ncm/mm). The ISQ values increased between the time of surgery and recall for all systems on average, but a significant positive correlation was found for DTSAE only. Significantly higher amounts of titanium were found in the surrounding bone with WPTPS (0.76%) and LPAOS (0.41%) in comparison with DTSAE (0.10%) and LPHES (0.03%). Immediate loading is possible with various designs and surfaces if high primary stability can be achieved during implant placement.

  13. Multifunctional Structures for High-Energy Lightweight Load-Bearing Storage

    Science.gov (United States)

    Loyselle, Patricia L.

    2018-01-01

    This is a pull-up banner of the Multifunctional Structures for High-Energy Lightweight Load-bearing Storage (M-SHELLS) technology that will be on display at the SciTech Conference in January 2018. Efforts in Multifunctional Structures for High Energy Load-Bearing Storage (M-Shells) are pushing the boundaries of development for hybrid electric propulsion for future commercial aeronautical transport. The M-Shells hybrid material would serve as the power/energy storage of the vehicle and provide structural integrity, freeing up usable volume and mass typically occupied by bulky batteries. The ultimate goal is to demonstrate a system-level mass savings with a multifunctional structure with energy storage.

  14. Structural response testing of thermal barrier load-bearing ceramic pads

    International Nuclear Information System (INIS)

    Black, W.E.; Luci, R.K.; Pickering, J.L.; Oland, G.B.

    1983-01-01

    A load bearing insulating structure for use in a HTGR was investigated. The structure was composed of dense ceramic materials in the form of circular pads arranged in a stack. Specifically, the test program was structured to investigate the isolation effectiveness of interface materials placed between the ceramic pads to reduce the effectiveness of mechanically induced loads. The tests were conducted at room temperature using tapered loading platens on single ceramic pads. Seventeen alumina specimens, representing two types of material and two thicknesses, were tested. Three interface material thicknesses were introduced using silica cloth and graphite foil. Pre and post test nondestructive examinations were conducted in an effort to identify potential damage-inducing anomalies in the ceramic pads. A total of 62 tests was conducted with all specimens eventually loaded to failure. (orig./HP)

  15. Design automation of load-bearing arched structures of roofs of tall buildings

    Science.gov (United States)

    Kulikov, Vladimir

    2018-03-01

    The article considers aspects of the possible use of arched roofs in the construction of skyscrapers. Tall buildings experience large load from various environmental factors. Skyscrapers are subject to various and complex types of deformation of its structural elements. The paper discusses issues related to the aerodynamics of various structural elements of tall buildings. The technique of solving systems of equations state method of Simpson. The article describes the optimization of geometric parameters of bearing elements of the arched roofs of skyscrapers.

  16. Early loading of plalatal implants (ortho-type II a prospective multicenter randomized controlled clinical trial

    Directory of Open Access Journals (Sweden)

    Gedrange Tomasz

    2007-09-01

    Full Text Available Abstract Background In orthodontic treatment, anchorage control is a fundamental aspect. Usually conventional mechanism for orthodontic anchorage control can be either extraoral or intraoral that is headgear or intermaxillary elastics. Their use are combined with various side effects such as tipping of occlusal plane or undesirable movements of teeth. Especially in cases, where key-teeth are missing, conventional anchorage defined as tooth-borne anchorage will meet limitations. Therefore, the use of endosseous implants for anchorage purposes are increasingly used to achieve positional stability and maximum anchorage. Methods/Design The intended study is designed as a prospective, multicenter randomized controlled trial (RCT, comparing and contrasting the effect of early loading of palatal implant therapy versus implant loading after 12 weeks post implantation using the new ortho-implant type II anchor system device (Orthosystem Straumann, Basel, Switzerland. 124 participants, mainly adult males or females, whose diagnoses require temporary stationary implant-based anchorage treatment will be randomized 1:1 to one of two treatment groups: group 1 will receive a loading of implant standard therapy after a healing period of 12 week (gold standard, whereas group 2 will receive an early loading of orthodontic implants within 1 week after implant insertion. Participants will be at least followed for 12 months after implant placement. The primary endpoint is to investigate the behavior of early loaded palatal implants in order to find out if shorter healing periods might be justified to accelerate active orthodontic treatment. Secondary outcomes will focus e.g. on achievement of orthodontic treatment goals and quantity of direct implant-bone interface of removed bone specimens. As tertiary objective, a histologic and microtomography evaluation of all retrieved implants will be performed to obtain data on the performance of the SLA surface in human bone

  17. Effects of mechanical repetitive load on bone quality around implants in rat maxillae.

    Directory of Open Access Journals (Sweden)

    Yusuke Uto

    Full Text Available Greater understanding and acceptance of the new concept "bone quality", which was proposed by the National Institutes of Health and is based on bone cells and collagen fibers, are required. The novel protein Semaphorin3A (Sema3A is associated with osteoprotection by regulating bone cells. The aims of this study were to investigate the effects of mechanical loads on Sema3A production and bone quality based on bone cells and collagen fibers around implants in rat maxillae. Grade IV-titanium threaded implants were placed at 4 weeks post-extraction in maxillary first molars. Implants received mechanical loads (10 N, 3 Hz for 1800 cycles, 2 days/week for 5 weeks from 3 weeks post-implant placement to minimize the effects of wound healing processes by implant placement. Bone structures, bone mineral density (BMD, Sema3A production and bone quality based on bone cells and collagen fibers were analyzed using microcomputed tomography, histomorphometry, immunohistomorphometry, polarized light microscopy and birefringence measurement system inside of the first and second thread (designated as thread A and B, respectively, as mechanical stresses are concentrated and differently distributed on the first two threads from the implant neck. Mechanical load significantly increased BMD, but not bone volume around implants. Inside thread B, but not thread A, mechanical load significantly accelerated Sema3A production with increased number of osteoblasts and osteocytes, and enhanced production of both type I and III collagen. Moreover, mechanical load also significantly induced preferential alignment of collagen fibers in the lower flank of thread B. These data demonstrate that mechanical load has different effects on Sema3A production and bone quality based on bone cells and collagen fibers between the inside threads of A and B. Mechanical load-induced Sema3A production may be differentially regulated by the type of bone structure or distinct stress distribution

  18. Immediate occlusal loading of Osseotite implants in mandibular edentulous patients: a prospective observational report with 18-month data.

    Science.gov (United States)

    Drago, Carl J; Lazzara, Richard J

    2006-01-01

    To evaluate the efficacy of treatment consisting of placement and immediate occlusal loading of implants in 27 patients with edentulous mandibles. Twenty-seven patients were treated in two private practice settings. One hundred fifty-one implants were placed and immediately occlusally loaded with fixed implant prostheses (15 cement-retained, 12 screw-retained) on the day of implant placement. The implant-retained prostheses were inserted within 5 hours of implant placement. Patients were followed for at least 18 months. The required criteria for immediate occlusal loading was primary implant stability of at least 30 Ncm of insertion torque. The implant prostheses were removed at least 12 months post-placement and the implants were evaluated for primary clinical stability and radiographic bone apposition to implants. At the 12-month follow-up appointments, cumulative survival rates of 98.0% and 100% were recorded for implants and prostheses, respectively. Three implants failed within 3 months. All other implants were clinically successful. Immediate occlusal loading of multiple, splinted mandibular implants is an effective treatment when implants are stable at insertion and are rigidly splinted with implant-retained prostheses.

  19. Effect of Cyclic Loading on Micromotion at the Implant-Abutment Interface.

    Science.gov (United States)

    Karl, Matthias; Taylor, Thomas D

    2016-01-01

    Cyclic loading may cause settling of abutments mounted on dental implants, potentially affecting screw joint stability and implant-abutment micromotion. It was the goal of this in vitro study to compare micromotion of implant-abutment assemblies before and after masticatory simulation. Six groups of abutments (n = 5) for a specific tissue-level implant system with an internal octagon were subject to micromotion measurements. The implant-abutment assemblies were loaded in a universal testing machine, and an apparatus and extensometers were used to record displacement. This was done twice, in the condition in which they were received from the abutment manufacturer and after simulated loading (100,000 cycles; 100 N). Statistical analysis was based on analysis of variance, two-sample t tests (Welch tests), and Pearson product moment correlation (α = .05). The mean values for micromotion ranged from 33.15 to 63.41 μm and from 30.03 to 42.40 μm before and after load cycling. The general trend toward reduced micromotion following load cycling was statistically significant only for CAD/CAM zirconia abutments (P = .036) and for one type of clone abutment (P = .012), with no significant correlation between values measured before and after cyclic loading (Pearson product moment correlation; P = .104). While significant differences in micromotion were found prior to load cycling, no significant difference among any of the abutment types tested could be observed afterward (P > .05 in all cases). A quantifiable settling effect at the implant-abutment interface seems to result from cyclic loading, leading to a decrease in micromotion. This effect seems to be more pronounced in low-quality abutments. For the implant system tested in this study, retightening of abutment screws is recommended after an initial period of clinical use.

  20. Improvement of the corrosion and tribological properties of CSS-42L aerospace bearing steel using carbon ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Fangfang; Zhou, Chungen; Zheng, Lijing, E-mail: zhenglijing@buaa.edu.cn; Zhang, Hu

    2017-01-15

    Highlights: • The corrosion and tribological properties of an aerospace bearing steel CSS-42L was investigated. • Carbon ion implantation was conducted and an amorphous layer formed at the near surface of CSS-42L steel. • The enhanced Cr diffusion and the decreased free electrons are contributed to the improvement of corrosion properties. • The external hard layer has positive effect on the wear resistance. - Abstract: The aerospace bearings steel CSS-42L was ion implanted by carbon with implantation fluxes of 5 × 10{sup 16} ions cm{sup −2}. The composition, microstructure and hardness of the carbon implanted samples were characterized using X-ray photoelectron spectroscopy, Auger electron spectroscopy, X-ray diffraction, and nanoindentation tests. The corrosion and tribological properties were also evaluated in the present work. The results shown that carbon implantation produced an amorphous layer and graphitic bounds formed at the near surface of CSS-42L steel. In the electrochemical test, the carbon implanted samples suggested lower current densities and corrosion rates. Carbon ion implanted samples shown a relative Cr-enrichment at the surface as compared with nonimplanted samples. The improved corrosion resistance is believed to be related to the formed amorphous layer, the enhancement of Cr diffusion in the carbon implantation layer which contributed the formation of passive film on the surface, the decrease of free electrons which caused by the increase of carbon fraction. The external hard layer had positive effect on the wear resistance, reducing strongly the friction coefficient about 30% and the abrasive-adhesive mechanism present in the unimplanted samples was not modified by the implantation process.

  1. 2D FEA of evaluation of micromovements and stresses at bone-implant interface in immediately loaded tapered implants in the posterior maxilla

    Directory of Open Access Journals (Sweden)

    Shrikar R Desai

    2013-01-01

    Full Text Available Aim: The aim of the study is to evaluate the influence implant length on stress distribution at bone implant interface in single immediately loaded implants when placed in D4 bone quality. Materials and Methods: A 2-dimensional finite element models were developed to simulate two types of implant designs, standard 3.75 mm-diameter tapered body implants of 6 and 10 mm lengths. The implants were placed in D4 bone quality with a cortical bone thickness of 0.5 mm. The implant design incorporated microthreads at the crestal part and the rest of the implant body incorporated Acme threads. The Acme thread form has a 29° thread angle with a thread height half of the pitch; the apex and valley are flat. A 100 N of force was applied vertically and in the oblique direction (at an angle of 45° to the long axis of the implants. The respective material properties were assigned. Micro-movements and stresses at the bone implant interface were evaluated. Results: The results of total deformation (micro-movement and Von mises stress were found to be lower for tapered long implant (10 mm than short implant (6 mm while using both vertical as well as oblique loading. Conclusion: Short implants can be successfully placed in poor bone quality under immediate loading protocol. The novel approach of the combination of microthreads at the crestal portion and acme threads for body portion of implant fixture gave promising results.

  2. 2D FEA of evaluation of micromovements and stresses at bone-implant interface in immediately loaded tapered implants in the posterior maxilla.

    Science.gov (United States)

    Desai, Shrikar R; Singh, Rika; Karthikeyan, I

    2013-09-01

    The aim of the study is to evaluate the influence implant length on stress distribution at bone implant interface in single immediately loaded implants when placed in D4 bone quality. A 2-dimensional finite element models were developed to simulate two types of implant designs, standard 3.75 mm-diameter tapered body implants of 6 and 10 mm lengths. The implants were placed in D4 bone quality with a cortical bone thickness of 0.5 mm. The implant design incorporated microthreads at the crestal part and the rest of the implant body incorporated Acme threads. The Acme thread form has a 29° thread angle with a thread height half of the pitch; the apex and valley are flat. A 100 N of force was applied vertically and in the oblique direction (at an angle of 45°) to the long axis of the implants. The respective material properties were assigned. Micro-movements and stresses at the bone implant interface were evaluated. The results of total deformation (micro-movement) and Von mises stress were found to be lower for tapered long implant (10 mm) than short implant (6 mm) while using both vertical as well as oblique loading. Short implants can be successfully placed in poor bone quality under immediate loading protocol. The novel approach of the combination of microthreads at the crestal portion and acme threads for body portion of implant fixture gave promising results.

  3. Improvement of the corrosion property of Cr4Mo4V bearing steel using plasma immersion ion implantation

    International Nuclear Information System (INIS)

    Wang, S.Y.; Chu, P.K.

    1997-01-01

    The working conditions of aerospace bearings such as engine bearings are quite harsh and prolonging the life span of these components is thus very important to the aerospace industry. Previous results have shown that the main failure mechanism of aerospace bearings is corrosion, and enhancing their corrosion resistance is a key. Cr4Mo4V, which is equivalent to AISI M50 bearing steel, is usually used in aerospace bearings in China. In this study, Cr4Mo4V components are treated in a new generation plasma immersion ion implanter in which ion implantation and sputter deposition can be carried out in the same chamber without breaking vacuum. Three treatment processes involving Cr, Mo, and N are evaluated. Our test results indicate that Cr is the main element enhancing the corrosion resistance and the addition of nitrogen improves the properties further. The non line-of-sight advantage of PIII is important to the processing of complex-shaped samples such as engine bearings. (orig.)

  4. Effect of cyclic load on vertical misfit of prefabricated and cast implant single abutment

    Directory of Open Access Journals (Sweden)

    Rudys Rodolfo de Jesus Tavarez

    2011-02-01

    Full Text Available OBJECTIVES: The purpose of this in vitro study was to evaluate misfit alterations at the implant/abutment interface of external and internal connection implant systems when subjected to cyclic loading. MATERIAL AND METHODS: Standard metal crowns were fabricated for 5 groups (n=10 of implant/abutment assemblies: Group 1, external hexagon implant and UCLA cast-on premachined abutment; Group 2, internal hexagon implant and premachined abutment; Group 3, internal octagon implant and prefabricated abutment; Group 4, external hexagon implant and UCLA cast-on premachined abutment; and Group 5, external hexagon implant and Ceraone abutment. For groups 1, 2, 3 and 5, the crowns were cemented on the abutments and in group 4 crowns were screwed directly on the implant. The specimens were subjected to 500,000 cycles at 19.1 Hz of frequency and non-axial load of 133 N in a MTS 810 machine. The vertical misfit (μm at the implant/abutment interface was evaluated before (B and after (A application of the cyclic loading. Data were analyzed statistically by using two-away ANOVA and Tukey's post-hoc test (p<0.05. RESULTS: Before loading values showed no difference among groups 2 (4.33±3.13, 3 (4.79±3.43 and 5 (3.86±4.60; between groups 1 (12.88±6.43 and 4 (9.67±3.08, and among groups 2, 3 and 4. However, groups 1 and 4 were significantly different from groups 2, 3 and 5. After loading values of groups 1 (17.28±8.77 and 4 (17.78±10.99 were significantly different from those of groups 2 (4.83±4.50, 3 (8.07±4.31 and 5 (3.81±4.84. There was a significant increase in misfit values of groups 1, 3 and 4 after cyclic loading, but not for groups 2 and 5. CONCLUSIONS: The cyclic loading and type of implant/abutment connection may develop a role on the vertical misfit at the implant/abutment interface.

  5. Load bearing and deformation behaviour of dynamically loaded wide plate specimens

    International Nuclear Information System (INIS)

    Julisch, P.; Haedrich, H.J.; Stadtmueller, W.; Sturm, D.

    1989-01-01

    For the testing of large-scale specimens, a 12 MN-High Loading Rate Tensile Testing Machine was designed and built at MPA Stuttgart. The aim was to determine the influence of high loading rates on the stress and strain behaviour of unwelded and welded components of ferritic and austenitic materials. This new generation of testing machines is driven by a propellant charge, and generates a maximum tensile force of 12 MN with a piston velocity of 25 m/s after a stroke of 20 mm, or a maximum velocity of 60 m/s after a stroke of 400 mm. In a first test programme, welded and unwelded wide plate specimens made of material X 6 CrNi 18 11 were tested at room temperature with different strain rates from 10 -3 /s to 63/s. In addition to a description of the 12 MN-High Loading Rate Tensile Testing Machine, the results of the high loading rate tensile tests performed will be presented and compared with quasistatically tested wide plate specimens. (orig.)

  6. Numerical Modelling and Analysis of Hydrostatic Thrust Air Bearings for High Loading Capacities and Low Air Consumption

    Science.gov (United States)

    Yu, Yunluo; Pu, Guang; Jiang, Kyle

    2017-12-01

    The paper presents a numerical simulation study on hydrostatic thrust air bearings to assess the load capacity, compressed air consumptions, and the dynamic response. Finite Difference Method (FDM) and Finite Volume Method (FVM) are combined to solve the non-linear Reynolds equation to find the pressure distribution of the air bearing gas film and the total loading capacity of the bearing. The influence of design parameters on air film gap characteristics, including the air film thickness, supplied pressure, depth of the groove and external load, are investigated based on the proposed FDM model. The simulation results show that the thrust air bearings with a groove have a higher load capacity and air consumption than without a groove, and the load capacity and air consumption both increase with the depth of the groove. Bearings without the groove are better damped than those with the grooves, and the stability of thrust bearing decreases when the groove depth increases. The stability of the thrust bearings is also affected by their loading.

  7. Use of transitional implants for immediate loading in mandibular complete dentures- A case report

    Directory of Open Access Journals (Sweden)

    Seema Bhoosreddy

    2009-01-01

    Full Text Available After the placement of implants in areas in which several teeth have been lost, both the clinician and the patient face many difficulties, particularly during healing. If no prosthesis is provided, the patient′s quality of life suffers. If a removable prosthesis is provided for optimum mastication and speech, many complicated adjustments of the denture may become necessary during healing, and the possibility of osseointegration failure increases. It has been reported that for implants to become osseointegrated, they must heal in the absence of functional loads for 4 to 6 months. To address the need for undisturbed healing and patient demand for uninterrupted immediate function and esthetics, the transitional implant system has been developed. This case report describes the use of transitional implants to support a removable mandibular overdenture. The transitional implant system is a sound and economical method of immediate patient restoration that allows for the protected healing of submerged implants.

  8. Bearing capacity and rigidity of short plastic-concrete-tubal vertical columns under transverse load

    Science.gov (United States)

    Dolzhenko, A. V.; Naumov, A. E.; Shevchenko, A. E.

    2018-03-01

    The results of mathematical modeling in determining strain-stress distribution parameters of a short plastic-concrete-tubal vertical column under horizontal load as those in vertical constructions are described. Quantitative parameters of strain-stress distribution during vertical and horizontal loads and horizontal stiffness were determined by finite element modeling. The internal stress in the concrete column core was analyzed according to equivalent stress in Mohr theory of failure. It was determined that the bearing capacity of a short plastic- concrete-tubal vertical column is 25% higher in resistibility and 15% higher in rigidness than those of the caseless concrete columns equal in size. Cracks formation in the core of a short plastic-concrete-tubal vertical column happens under significantly bigger horizontal loads with less amount of concrete spent than that in caseless concrete columns. The significant increase of bearing capacity and cracking resistance of a short plastic-concrete-tubal vertical column under vertical and horizontal loads allows recommending them as highly effective and highly reliable structural wall elements in civil engineering.

  9. Immediate Loading of Tapered Implants Placed in Postextraction Sockets and Healed Sites.

    Science.gov (United States)

    Han, Chang-Hun; Mangano, Francesco; Mortellaro, Carmen; Park, Kwang-Bum

    2016-07-01

    The aim of the present study was to compare the survival, stability, and complications of immediately loaded implants placed in postextraction sockets and healed sites. Over a 2-year period, all patients presenting with partial or complete edentulism of the maxilla and/or mandible (healed site group, at least 4 months of healing after tooth extraction) or in need of replacement of nonrecoverable failing teeth (postextraction group) were considered for inclusion in this study. Tapered implants featuring a nanostructured calcium-incorporated surface were placed and loaded immediately. The prosthetic restorations comprised single crowns, fixed partial dentures, and fixed full arches. Primary outcomes were implant survival, stability, and complications. Implant stability was assessed at placement and at each follow-up evaluation (1 week, 3 months, and 1 year after placement): implants with an insertion torque (IT) sockets of 17 patients, and 32 implants were placed in healed sites of 22 patients. There were no statistically significant differences in ISQ values between the 2 groups, at each assessment. In total, 60 implants (96.8%) had an IT ≥45 and an ISQ ≥70 at placement and at each follow-up control: all these implants were successfully loaded. Only 2 implants (1 in a postextraction socket and 1 in a healed site, 3.2%) could not achieve an IT ≥45 N·cm and/or an ISQ ≥70 at placement or over time: accordingly, these were considered failed for stability, as they could not be subjected to immediate loading. One of these 2 implants, in a healed site of a posterior maxilla, had to be removed, yielding an overall 1-year implant survival rate of 98.4%. No complications were reported. No significant differences were reported between the 2 groups with respect to implant failures and complications. Immediately loaded implants placed in postextraction sockets and healed sites had similar high survival and stability, with no reported complications. Further long

  10. In situ microradioscopy and microtomography of fatigue-loaded dental two-piece implants.

    Science.gov (United States)

    Wiest, Wolfram; Zabler, Simon; Rack, Alexander; Fella, Christian; Balles, Andreas; Nelson, Katja; Schmelzeisen, Rainer; Hanke, Randolf

    2015-11-01

    Synchrotron real-time radioscopy and in situ microtomography are the only techniques providing direct visible information on a micrometre scale of local deformation in the implant-abutment connection (IAC) during and after cyclic loading. The microgap formation at the IAC has been subject to a number of studies as it has been proposed to be associated with long-term implant success. The next step in this scientific development is to focus on the in situ fatigue procedure of two-component dental implants. Therefore, an apparatus has been developed which is optimized for the in situ fatigue analysis of dental implants. This report demonstrates both the capability of in situ radioscopy and microtomography at the ID19 beamline for the study of cyclic deformation in dental implants. The first results show that it is possible to visualize fatigue loading of dental implants in real-time radioscopy in addition to the in situ fatigue tomography. For the latter, in situ microtomography is applied during the cyclic loading cycles in order to visualize the opening of the IAC microgap. These results concur with previous ex situ studies on similar systems. The setup allows for easily increasing the bending force, to simulate different chewing situations, and is, therefore, a versatile tool for examining the fatigue processes of dental implants and possibly other specimens.

  11. Removal torque evaluation of three different abutment screws for single implant restorations after mechanical cyclic loading.

    Science.gov (United States)

    Paepoemsin, T; Reichart, P A; Chaijareenont, P; Strietzel, F P; Khongkhunthian, P

    2016-01-01

    The aim of this study was to evaluate the removal torque of three different abutment screws and pull out strength of implant-abutment connection for single implant restorations after mechanical cyclic loading. The study was performed in accordance with ISO 14801:2007. Three implant groups (n=15) were used: group A, PW Plus® with flat head screw; group B, PW Plus® with tapered screw; and group C, Conelog® with flat head screw. All groups had the same implant-abutment connection feature: cone with mandatory index. All screws were tightened with manufacturer's recommended torque. Ten specimens in each group underwent cyclic loading (1×106 cycles, 10 Hz, and 250 N). Then, all specimens were un-tightened, measured for the removal torque, and underwent a tensile test. The force that dislodged abutment from implant fixture was recorded. The data were analysed using independent sample t-test, ANOVA and Tukey HSD test. Before cyclic loading, removal torque in groups A, B and C were significantly different (B> A> C, Pabutment from implant fixture increased immensely after cyclic loading.

  12. Immediately loaded zygomatic implants vs conventional dental implants in augmented atrophic maxillae: 4 months post-loading results from a multicentre randomised controlled trial.

    Science.gov (United States)

    Esposito, Marco; Davó, Rubén; Marti-Pages, Carlos; Ferrer-Fuertes, Ada; Barausse, Carlo; Pistilli, Roberto; Ippolito, Daniela Rita; Felice, Pietro

    2018-01-01

    To compare the clinical outcome of immediately loaded cross-arch maxillary prostheses supported by zygomatic implants vs conventional implants placed in augmented bone. A total of 71 edentulous patients with severely atrophic maxillas, who did not have sufficient bone volume to place dental implants or when it was possible to place only two implants in the front area (minimal diameter 3.5 mm and length of 8 mm) and less than 4.0 mm of bone height subantrally, were randomised according to a parallel group design. They (35 patients) received zygomatic implants to be loaded immediately vs grafting with a xenograft, followed, after 6 months of graft consolidation, by the placement of six to eight conventional dental implants, submerged for 4 months (36 patients). To be loaded immediately, zygomatic implants had to be inserted with an insertion torque superior to 40 Ncm. Screw-retained, metal-reinforced, acrylic provisional prostheses were provided to be replaced by definitive Procera Implant Bridge Titanium prostheses (Nobel Biocare, Göteborg, Sweden) with ceramic or acrylic veneer materials 4 months after initial loading. Outcome measures were: prosthesis, implant and augmentation failures, any complications, quality of life (OHIP-14), the number of days that patients experienced total or partial impaired activity, time to function, and number of dental visits, assessed by independent assessors. Patients were followed up to 4 months after loading. No augmentation procedure failed. Three patients dropped out from the augmentation group. Six prostheses could not be delivered or failed in the augmentation group vs one prosthesis in the zygomatic group, the difference being statistically significant (difference in proportions = 15.32%; P = 0.04; 95% CI: 0.23 to 31.7). Eight patients lost 35 implants in the augmentation group vs three implants in one patient from the zygomatic group, the difference being statistically significant (difference in proportions = 21.38%; P = 0

  13. Effect on Bone Architecture of Marginal Grooves in Dental Implants Under Occlusal Loaded Conditions in Beagle Dogs.

    Science.gov (United States)

    Kato, Hatsumi; Kuroshima, Shinichiro; Inaba, Nao; Uto, Yusuke; Sawase, Takashi

    2018-02-01

    The aim of this study was to clarify whether marginal grooves on dental implants affect osseointegration, bone structure, and the alignment of collagen fibers to determine bone quality under loaded conditions. Anodized Ti-6Al-4V alloy dental implants, with and without marginal grooves (test and control implants, respectively), were used (3.7 × 8.0 mm). Fourth premolars and first molars of 6 beagle mandibles were extracted. Two control and test implants were placed in randomly selected healed sites at 12 weeks after tooth extraction. Screw-retained single crowns for first molars were fabricated. Euthanasia was performed at 8 weeks after the application of occlusal forces. Implant marginal bone level, bone to implant contact (BIC), bone structure around dental implants, and the alignment of collagen fibers determining bone quality were analyzed. The marginal bone level in test implants was significantly higher than that in control implants. Occlusal forces significantly increased BIC in test implants ( P = .007), whereas BIC did not change in control implants, irrespective of occlusal forces ( P = .303). Moreover, occlusal forces significantly increased BIC in test implants compared with control implants ( P = .032). Additionally, occlusal forces preferentially aligned collagen fibers in test implants, but not control implants. Hence, marginal grooves on dental implants have positive effects on increased osseointegration and adapted bone quality based on the preferential alignment of collagen fibers around dental implants under loaded conditions.

  14. Influence of occlusal loading on peri-implant clinical parameters. A pilot study.

    Science.gov (United States)

    Pellicer-Chover, Hilario; Viña-Almunia, José; Romero-Millán, Javier; Peñarrocha-Oltra, David; García-Mira, Berta; Peñarrocha-Diago, María

    2014-05-01

    To investigate the relation between occlusal loading and peri-implant clinical parameters (probing depth, bleeding on probing, gingival retraction, width of keratinized mucosa, and crevicular fluid volume) in patients with implant-supported complete fixed prostheses in both arches. This clinical study took place at the University of Valencia (Spain) dental clinic. It included patients attending the clinic for regular check-ups during at least 12 months after rehabilitation of both arches with implant-supported complete fixed ceramo-metallic prostheses. One study implant and one control implant were established for each patient using the T-Scan®III computerized system (Tesco, South Boston, USA). The maxillary implant closest to the point of maximum occlusal loading was taken as the study implant and the farthest (with least loading) as the control. Occlusal forces were registered with the T-Scan® III and then occlusal adjustment was performed to distribute occlusal forces correctly. Peri-implant clinical parameters were analyzed in both implants before and two and twelve months after occlusal adjustment. Before occlusal adjustment, study group implants presented a higher mean volume of crevicular fluid (51.3 ± 7.4 UP) than the control group (25.8 ± 5.5 UP), with statistically significant difference. Two months after occlusal adjustment, there were no significant differences between groups (24.6 ± 3.8 UP and 26 ± 4.5 UP respectively) (p=0.977). After twelve months, no significant differences were found between groups (24.4 ± 11.1 UP and 22.5 ± 8.9 UP respectively) (p=0.323). For the other clinical parameters, no significant differences were identified between study and control implants at any of the study times (p>0.05). Study group implants receiving higher occlusal loading presented significantly higher volumes of crevicular fluid than control implants. Crevicular fluid volumes were similar in both groups two and twelve months after occlusal adjustment.

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

    Science.gov (United States)

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

    2016-10-01

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

  16. Stress distribution and displacement of abutment of middle implant-natural teeth fixed bridge under different loading

    International Nuclear Information System (INIS)

    Chen Erjun; Zhou Yanmin; Ma Chenchun; Cong Zhiqiang; Jiang Yonghua

    2004-01-01

    Objective: To study stress distribution and displacement of abutment of middle implant-natural teeth fixed bridge under different loading. Methods: The stress distribution and displacement of abutment were studied and analyzed by means of three-dimensional finite element when different loading was applied. Results: The biggest stress of middle implant was 4-5 times as big as that of natural teeth. Under concentrated vertical loading, the biggest stress of implant was about 2 times higher than that under dispersed vertical loading. There was no significant difference of biggest stress on the implant between concentrated oblique loading and dispersed oblique loading. The biggest stress of implant under oblique loading was 3 times as big as that under dispersed vertical loading. The biggest stress of natural teeth under dispersed loading was lower than that under concentrated loading. The maximum displacement of implant in occlusal-gum direction was great lower than that of natural teeth. Both in buccal-lingual direction and medial-distal direction, the displacement of implant were about equal to that of natural teeth. Conclusion: The oblique loading is the main force to destroy the middle implant-natural teeth fixed bridge. The lean of cusp should be reduced. The abnormally high occlusal points should be deleted. The bite points should be well distributed. The fixed bridge is feasible. (authors)

  17. Fracture load of different crown systems on zirconia implant abutments.

    Science.gov (United States)

    Albrecht, T; Kirsten, A; Kappert, H F; Fischer, H

    2011-03-01

    The purpose of this study was to evaluate the fracture load of single zirconia abutment restorations using different veneering techniques and materials. The abutment restorations were divided into 6 groups with 20 samples each: test abutments (control group A), lithium disilicate ceramic crowns bonded on incisor abutments (group B), leucite ceramic crowns bonded on incisor abutments (group C), premolar abutments directly veneered with a fluor apatite ceramic (group D (layered) and group E (pressed)) and premolar abutments bonded with lithium disilicate ceramic crowns (group F). The fracture load of the restorations was evaluated using a universal testing machine. Half of each group was artificially aged (chewing simulation and thermocycling) before evaluating the fracture load with the exception of the test abutments. The fracture load of the test abutments was 705 ± 43N. Incisor abutments bonded with lithium disilicate or leucite ceramic crowns (groups B and C) showed fracture loads of about 580N. Premolar restorations directly veneered with fluor apatite ceramic (groups D and E) showed fracture loads of about 850N. Premolar restorations bonded with lithium disilicate ceramic crowns (group F) showed fracture loads of about 1850N. The artificial ageing showed no significant influence on the strength of the examined restorations. All ceramic crowns made of lithium disilicate glass-ceramic, adhesively bonded to premolar abutments showed the highest fracture loads in this study. However, all tested groups can withstand physiological bite forces. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  18. Influence of matrix attachment installation load on movement and resultant forces in implant overdentures.

    Science.gov (United States)

    Goto, Takaharu; Nagao, Kan; Ishida, Yuichi; Tomotake, Yoritoki; Ichikawa, Tetsuo

    2015-02-01

    This in vitro study investigated the effect of attachment installation conditions on the load transfer and denture movements of implant overdentures, and aims to clarify the differences among the three types of attachments, namely ball, Locator, and magnet attachments. Three types of attachments, namely ball, Locator, and magnetic attachments were used. An acrylic resin mandibular edentulous model with two implants placed in the bilateral canine regions and removable overdenture were prepared. The two implants and bilateral molar ridges were connected to three-axis load-cell transducers, and a universal testing machine was used to apply a 50 N vertical force to each site of the occlusal table in the first molar region. The denture movement was measured using a G(2) motion sensor. Three installation conditions, namely, the application of 0, 50, and 100 N loads were used to install each attachment on the denture base. The load transfer and denture movement were then evaluated. The resultant force decreased with increasing installation load for all attachments. In particular, the resultant force on implants on the loading side of the Locator attachment significantly decreased when the installation load was increased from 0 to 50 N, and that for magnetic attachment significantly decreased when the installation load was increased from 50 to 100 N. For the residual ridges on the loading side, the direction of the forces for all attachments changed to downward with increasing installation load. Furthermore, the yaw Euler angle increased with increasing installation load for the magnetic attachment. Subject to the limitations of this study, the use of any installation load greater than 0 N is recommended for the installation of ball and Locator attachments on a denture base. Regarding magnetic attachments, our results also recommend installation on a denture base using any installation load greater than 0 N, and suggest that the resultant force acting on the implant can be

  19. Clinical and radiographic evaluation of early loaded narrow-diameter implants

    DEFF Research Database (Denmark)

    Maiorana, Carlo; King, Paul; Quaas, Sebastian

    2015-01-01

    OBJECTIVE: To evaluate the clinical reliability of narrow implants placed in a one-stage procedure and early loaded in the upper and lower incisor region. MATERIAL AND METHODS: This is a prospective, single-arm, multicenter study in which patients with missing natural dentition in upper lateral a...... be considered as a valid solution in the treatment of the localized narrow bony defects in the anterior area with reduced spaces between the natural teeth....... healing period. Clinical and radiographic checks were performed at implant placement, loading, and at the 6, 12, 24, and 36 months follow-up visits. RESULTS: A total of 69 subjects with 97 implants have been included in this study. From surgery to 36 months follow-up, 5.6% of the implants showed bone loss...... loss between loading and the 1-year follow-up visit (Galindo-Moreno et al. 2012). This finding, associated with a stable probing pocket depth and a stable crown-gingiva distance, using a one-stage surgical procedure helps to maintain the integrity of the peri-implant soft tissues. Narrow implants can...

  20. The immediate insertion, loading and provisional prosthetic restoration of dental implants.

    Science.gov (United States)

    Sârbu, I

    2008-01-01

    The immediate insertion and loading of dental implants although used in the past as an alternative method for the surgical phase of the dental implant treatment is today becoming more and more popular due to its immediate and spectacular results. With information on bone density and a careful patient selection, this method has increased chances of success. Its main advantage is the high degree of patient comfort with a great aesthetic effect. This article presents the theoretical and practical technique used on two clinical cases of dental implantation and their outcome.

  1. Immediate loading implants with mandibular overdenture: a 48-month prospective follow-up study

    Directory of Open Access Journals (Sweden)

    Karla ZANCOPE

    2014-08-01

    Full Text Available The aim of this prospective clinical study was to evaluate patient rehabilitation with two immediately loaded implants and bar-retained mandibular overdentures after 48 months of follow-up. Twenty patients were treated with two implants each; of these, 17 patients were re-evaluated for comparison. Gender, age, plaque index, gingival inflammation, keratinized mucosa, probing depth, bleeding, and implant loss data were recorded, and periapical radiographs were obtained for measurement of marginal bone loss. The results were statistically analyzed with one-way analysis of variance (ANOVA followed by Student’s t-test and Pearson’s correlation test. To compare the data at baseline and after 48 months, a Wilcoxon Signed Rank Test was performed (α = 0.05. One implant failed (2.9% during the first year and was replaced. A total of 35 implants were evaluated. Bone loss values were 0.52–2.89 mm (mean, 1.46 mm. Probing depth was 1.75–3.75 mm (mean, 2.22 mm. Correlations were found between bone loss and plaque index and between bone loss and gender, but bone loss did not correlate with gingival inflammation, keratinized mucosa, probing depth, or age. The overall survival rate of the implants was 97.1%. Based on these results, the use of two immediately loaded splinted interforaminal implants to retain an overdenture with a bar attachment is a clinically viable option with a high survival rate.

  2. Retrospective analysis of 56 edentulous dental arches restored with 344 single-stage implants using an immediate loading fixed provisional protocol: statistical predictors of implant failure.

    Science.gov (United States)

    Kinsel, Richard P; Liss, Mindy

    2007-01-01

    The purpose of this retrospective study was to evaluate the effects of implant dimensions, surface treatment, location in the dental arch, numbers of supporting implant abutments, surgical technique, and generally recognized risk factors on the survival of a series of single-stage Straumann dental implants placed into edentulous arches using an immediate loading protocol. Each patient received between 4 and 18 implants in one or both dental arches. Periapical radiographs were obtained over a 2- to 10-year follow-up period to evaluate crestal bone loss following insertion of the definitive metal-ceramic fixed prostheses. Univariate tests for failure rates as a function of age ( or = 60 years), gender, smoking, bone grafting, dental arch, surface type, anterior versus posterior, number of implants per arch, and surgical technique were made using Fisher exact tests. The Cochran-Armitage test for trend was used to evaluate the presence of a linear trend in failure rates regarding implant length and implant diameter. Logistic regression modeling was used to determine which, if any, of the aforementioned factors would predict patient and implant failure. A significance criterion of P = .05 was utilized. Data were collected for 344 single-stage implants placed into 56 edentulous arches (39 maxillae and 17 mandibles) of 43 patients and immediately loaded with a 1-piece provisional fixed prosthesis. A total of 16 implants failed to successfully integrate, for a survival rate of 95.3%. Increased rates of failure were associated with reduced implant length, placement in the posterior region of the jaw, increased implant diameter, and surface treatment. Implant length emerged as the sole significant predictor of implant failure. In this retrospective analysis of 56 consecutively treated edentulous arches with multiple single-stage dental implants loaded immediately, reduced implant length was the sole significant predictor of failure.

  3. Clinical Parameters and Crestal Bone Loss in Internal Versus External Hex Implants at One Year after Loading

    Directory of Open Access Journals (Sweden)

    HamidReza Arab

    2015-09-01

    Full Text Available Introduction: The survival of an implant system is affected by the choice of antirotational design, which can include an external or internal hex. Implant success also is affected by the maintenance of the crestal bone around implants. The aim of present study was to evaluate the crestal bone loss and clinical parameters related to bone loss in patients loaded with an external or internal hex 3i implant (3i Implant Innovation, Palm Beach Gardens, FL, USA. The evaluations were performed one year after loading. Materials and Methods: A total of 39 implants (23 external hex, 16 internal hex were placed randomly in 23 patients (10 male, 13 female by a submerged approach. None of patients had compromised conditions or parafunctional habits. At placement and at one year after loading, periapical radiographs were taken via the parallel method from the implant sites. Results: Crestal bone loss was -0.712±0.831 mm in implants with an internal hex connection and -0.139±0.505 mm in implants with an external hex connection (P≤0.05. No correlation was found between crestal bone loss and parameters such as age, gender, jaw, implant location (anterior, premolar, or molar, implant diameter, or implant length. Conclusions: Crestal bone loss was greater in patients with internal hex 3i implants than in those with external implants. Similar results in other clinical factors were found between the groups.

  4. Diet and environment shape fecal bacterial microbiota composition and enteric pathogen load of grizzly bears.

    Directory of Open Access Journals (Sweden)

    Clarissa Schwab

    Full Text Available BACKGROUND: Diet and environment impact the composition of mammalian intestinal microbiota; dietary or health disturbances trigger alterations in intestinal microbiota composition and render the host susceptible to enteric pathogens. To date no long term monitoring data exist on the fecal microbiota and pathogen load of carnivores either in natural environments or in captivity. This study investigates fecal microbiota composition and the presence of pathogenic Escherichia coli and toxigenic clostridia in wild and captive grizzly bears (Ursus arctos and relates these to food resources consumed by bears. METHODOLOGY/PRINCIPAL FINDINGS: Feces were obtained from animals of two wild populations and from two captive animals during an active bear season. Wild animals consumed a diverse diet composed of plant material, animal prey and insects. Captive animals were fed a regular granulated diet with a supplement of fruits and vegetables. Bacterial populations were analyzed using quantitative PCR. Fecal microbiota composition fluctuated in wild and in captive animals. The abundance of Clostridium clusters I and XI, and of C. perfringens correlated to regular diet protein intake. Enteroaggregative E. coli were consistently present in all populations. The C. sordellii phospholipase C was identified in three samples of wild animals and for the first time in Ursids. CONCLUSION: This is the first longitudinal study monitoring the fecal microbiota of wild carnivores and comparing it to that of captive individuals of the same species. Location and diet affected fecal bacterial populations as well as the presence of enteric pathogens.

  5. Diet and environment shape fecal bacterial microbiota composition and enteric pathogen load of grizzly bears.

    Science.gov (United States)

    Schwab, Clarissa; Cristescu, Bogdan; Northrup, Joseph M; Stenhouse, Gordon B; Gänzle, Michael

    2011-01-01

    Diet and environment impact the composition of mammalian intestinal microbiota; dietary or health disturbances trigger alterations in intestinal microbiota composition and render the host susceptible to enteric pathogens. To date no long term monitoring data exist on the fecal microbiota and pathogen load of carnivores either in natural environments or in captivity. This study investigates fecal microbiota composition and the presence of pathogenic Escherichia coli and toxigenic clostridia in wild and captive grizzly bears (Ursus arctos) and relates these to food resources consumed by bears. Feces were obtained from animals of two wild populations and from two captive animals during an active bear season. Wild animals consumed a diverse diet composed of plant material, animal prey and insects. Captive animals were fed a regular granulated diet with a supplement of fruits and vegetables. Bacterial populations were analyzed using quantitative PCR. Fecal microbiota composition fluctuated in wild and in captive animals. The abundance of Clostridium clusters I and XI, and of C. perfringens correlated to regular diet protein intake. Enteroaggregative E. coli were consistently present in all populations. The C. sordellii phospholipase C was identified in three samples of wild animals and for the first time in Ursids. This is the first longitudinal study monitoring the fecal microbiota of wild carnivores and comparing it to that of captive individuals of the same species. Location and diet affected fecal bacterial populations as well as the presence of enteric pathogens.

  6. Doxycycline-loaded coaxial nanofiber coating of titanium implants enhances osseointegration and inhibits Staphylococcus aureus infection.

    Science.gov (United States)

    Song, Wei; Seta, Joseph; Chen, Liang; Bergum, Christopher; Zhou, Zhubin; Kanneganti, Praveen; Kast, Rachel E; Auner, Gregory W; Shen, Ming; Markel, David C; Ren, Weiping; Yu, Xiaowei

    2017-07-05

    Few studies have been reported that focus on developing implant surface nanofiber (NF) coating to prevent infection and enhance osseointegration by local drug release. In this study, coaxial doxycycline (Doxy)-doped polycaprolactone/polyvinyl alcohol (PCL/PVA) NFs were directly deposited on a titanium (Ti) implant surface during electrospinning. The interaction of loaded Doxy with both PVA and PCL NFs was characterized by Raman spectroscopy. The bonding strength of Doxy-doped NF coating on Ti implants was confirmed by a stand single-pass scratch test. The improved implant osseointegration by PCL/PVA NF coatings in vivo was confirmed by scanning electron microscopy, histomorphometry and micro computed tomography (μCT) at 2, 4 and 8 weeks after implantation. The bone contact surface (%) changes of the NF coating group (80%) is significantly higher than that of the no NF group (coating effectively inhibited bacterial infection and enhanced osseointegration in an infected (Staphylococcus aureus) tibia implantation rat model. Doxy released from NF coating inhibited bacterial growth up to 8 weeks in vivo. The maximal push-in force of the Doxy-NF coating (38 N) is much higher than that of the NF coating group (6.5 N) 8 weeks after implantation (p coating doped with Doxy and/or other drugs have great potential in enhancing implant osseointegration and preventing infection.

  7. Assessment of the transportation route of oversize and excessive loads in relation to the load-bearing capacity of existing bridges

    Science.gov (United States)

    Doležel, Jiří; Novák, Drahomír; Petrů, Jan

    2017-09-01

    Transportation routes of oversize and excessive loads are currently planned in relation to ensure the transit of a vehicle through critical points on the road. Critical points are level-intersection of roads, bridges etc. This article presents a comprehensive procedure to determine a reliability and a load-bearing capacity level of the existing bridges on highways and roads using the advanced methods of reliability analysis based on simulation techniques of Monte Carlo type in combination with nonlinear finite element method analysis. The safety index is considered as a main criterion of the reliability level of the existing construction structures and the index is described in current structural design standards, e.g. ISO and Eurocode. An example of a single-span slab bridge made of precast prestressed concrete girders of the 60 year current time and its load bearing capacity is set for the ultimate limit state and serviceability limit state. The structure’s design load capacity was estimated by the full probability nonlinear MKP analysis using a simulation technique Latin Hypercube Sampling (LHS). Load-bearing capacity values based on a fully probabilistic analysis are compared with the load-bearing capacity levels which were estimated by deterministic methods of a critical section of the most loaded girders.

  8. Three dimensional biphasic calcium phosphate nanocomposites for load bearing bioactive bone grafts

    Energy Technology Data Exchange (ETDEWEB)

    Garai, Subhadra, E-mail: subha@nmlindia.org; Sinha, Arvind

    2016-02-01

    Mimicking matrix mediated bio-mineralization process, three dimensional blocks of biphasic calcium phosphate (BCP, hydroxyapatite (HA) and β-tricalcium phosphate (TCP)) nanocomposites, having three different stoichiometries have been synthesized for possible application as load bearing synthetic bone graft or scaffolds. Biphasic blocks with three weight ratios of 20:80, 25:75 and 30:70 of HA and TCP respectively have been synthesized. Detailed structural and chemical characterization of the samples revealed a strong dependence of porosity and mechanical properties on the stoichiometry of biphasic blocks. Effect of physiological medium on the microstructure and mechanical properties of the three different blocks has also been studied. Bioactivity of the BCP block, exhibiting highest compressive strength in air as well as in physiological medium, has been evaluated through adhesion, proliferation and differentiation of mesenchymal stem cells using different markers. - Highlights: • Developed a process for the synthesis of load bearing 3d- biphasic nanocomposites. • Synthesized nanocomposites exhibited in vitro osteoconductivity and osteoinductivity for bone marrow mesenchymal cells. • Developed process is a matrix mediated biomimetic one.

  9. Immediate loading of implants in the aesthetic zone: comparison between two placement timings.

    Science.gov (United States)

    Carini, Fabrizio; Longoni, Salvatore; Pisapia, Valeria; Francesconi, Manuel; Saggese, Vito; Porcaro, Gianluca

    2014-01-01

    Implant rehabilitation delivered in accordance with the traditional protocol has proven to be highly predictable and acceptable (1). Nevertheless, the application of immediate loading on post-extraction implants, especially for aesthetic zones, has now considerably increased (2). The aim of this work is to illustrate the immediate loading of implants placed in the aesthetic zone through tapered design fixtures with microgeometry of a high degree of porosity inserted at the same time or 4-8 weeks from dental avulsion (TSA® Advance, Phibo®). A total of 15 implant fixtures of which 8 at an interval of 4-8 weeks from extraction (type 2) and the remaining according to the immediate post-extraction technique (type 1) were positioned. All implants were prosthesized within 24 hours from the placement. Definitive crowns replaced provisional restorations after 20-24 weeks. After 4 and 12 months from implant insertion, the following parameters were assessed: X-ray image, pain, mobility or suppuration, soft tissue condition and aesthetic appearance. Percentage of osseointegration was 93.75%, and 53.5% of the osseointegrated fixtures was type 2. No statistically significant difference between the mean ISQ values for implants of type 1 and 2 both in the post-operative period and after 12 months was evident, indicating that the timing of insertion did not affect the achievement of stability for the implant fixtures tested in our study. Immediate post-extraction implants showed a greater propensity for gingival recession and a peri-implant radiolucency greater than those placed at an interval of 4-8 weeks. The values obtained for the PES/WES and the subjective evaluation of the analyzed sample showed the considerable aesthetic value and the high level of satisfaction guaranteed by the implant technique illustrated. Although well-designed, high quality, randomized clinical trials are still needed as well as the requirement to establish a common, complete, and reproducible index

  10. Tank Applied Testing of Load-Bearing Multilayer Insulation (LB-MLI)

    Science.gov (United States)

    Johnson, Wesley L.; Valenzuela, Juan G.; Feller, Jerr; Plachta, Dave

    2014-01-01

    The development of long duration orbital cryogenic storage systems will require the reduction of heat loads into the storage tank. In the case of liquid hydrogen, complete elimination of the heat load at 20 K is currently impractical due to the limitations in lift available on flight cryocoolers. In order to reduce the heat load, without having to remove heat at 20 K, the concept of Reduced Boil-Off uses cooled shields within the insulation system at approximately 90 K. The development of Load-Bearing Multilayer Insulation (LB-MLI) allowed the 90 K shield with tubing and cryocooler attachments to be suspended within the MLI and still be structurally stable. Coupon testing both thermally and structurally were performed to verify that the LB-MLI should work at the tank applied level. Then tank applied thermal and structural (acoustic) testing was performed to demonstrate the functionality of the LB-MLI as a structural insulation system. The LB-MLI showed no degradation of thermal performance due to the acoustic testing and showed excellent thermal performance when integrated with a 90 K class cryocooler on a liquid hydrogen tank.

  11. Immediate versus early non-occlusal loading of dental implants placed flapless in partially edentulous patients. One-year results from a randomised controlled trial.

    Science.gov (United States)

    Merli, Mauro; Merli, Aldo; Bernardelli, Francesco; Lombardini, Francesco; Esposito, Marco

    2008-01-01

    To compare immediate versus early (6 weeks) non-occlusal loading of dental implants placed flapless in partially edentulous patients 1 year after loading. Sixty patients were randomised: 30 to the immediately loaded group and 30 to the early loaded group. In order to be immediately loaded, implants were inserted with a minimum torque of > or = 40Ncm. Implants were fully occlusally loaded after 6 months. Outcome measures were prosthesis and implant failures, and biological and biomechanical complications. Five implants in five patients randomised to the immediately loaded group did not reach the required primary implant stability. Three of these implants (two prostheses) were not immediately loaded. Two patients who were randomised to the early loaded group were immediately loaded erroneously. Implants in five patients of the early loaded group were conventionally loaded. No patient dropped out and there were no failures. Two complications occurred in the early and one in the immediately loaded group (no statistically significant difference), but were solved. The use of a flapless technique for placing dental implants in conjunction with non-occlusal immediate or early loading in selected patients can provide excellent clinical results. No differences were observed when comparing implants that were loaded immediately or early. Therefore, when a high primary implant stability is obtained, it might be preferable to load the implants immediately rather than waiting for a few weeks.

  12. Alveolar Bone Resorption Evaluation Around Single-piece Designed Bicortical Implants, Using Immediate Loading Protocol, Based on Orthopantomographs

    Directory of Open Access Journals (Sweden)

    Száva Dániel-Tamás

    2017-12-01

    Full Text Available Background: Inserting dental implants in severely atrophied jawbones is a great challenge for the dental practitioner. There are an increasing number of patients who choose dental implantanchored prosthetic restorations despite compromised bone quality and quantity. There have been numerous attempts in adapting implant design for the atrophic crestal bone. One-piece, needle-type basal implant design is a typical design for these cases. These implants are inserted in the remaining compact bone located in the basal aspect of the jawbones. If high primary stability is achieved, these implants are used for immediate loading protocol. From many points of view, this technique is based on contradictory principles compared to classic implant surgery and loading protocols. The aim of this study was to investigate the long-term success of basal one-piece short-diameter dental implants used for immediate loading protocol.

  13. Approximate solution of oil film load-carrying capacity of turbulent journal bearing with couple stress flow

    Science.gov (United States)

    Zhang, Yongfang; Wu, Peng; Guo, Bo; Lü, Yanjun; Liu, Fuxi; Yu, Yingtian

    2015-01-01

    The instability of the rotor dynamic system supported by oil journal bearing is encountered frequently, such as the half-speed whirl of the rotor, which is caused by oil film lubricant with nonlinearity. Currently, more attention is paid to the physical characteristics of oil film due to an oil-lubricated journal bearing being the important supporting component of the bearing-rotor systems and its nonlinear nature. In order to analyze the lubrication characteristics of journal bearings efficiently and save computational efforts, an approximate solution of nonlinear oil film forces of a finite length turbulent journal bearing with couple stress flow is proposed based on Sommerfeld and Ocvirk numbers. Reynolds equation in lubrication of a finite length turbulent journal bearing is solved based on multi-parametric principle. Load-carrying capacity of nonlinear oil film is obtained, and the results obtained by different methods are compared. The validation of the proposed method is verified, meanwhile, the relationships of load-carrying capacity versus eccentricity ratio and width-to-diameter ratio under turbulent and couple stress working conditions are analyzed. The numerical results show that both couple stress flow and eccentricity ratio have obvious influence on oil film pressure distribution, and the proposed method approximates the load-carrying capacity of turbulent journal bearings efficiently with various width-to-diameter ratios. This research proposes an approximate solution of oil film load-carrying capacity of turbulent journal bearings with different width-to-diameter ratios, which are suitable for high eccentricity ratios and heavy loads.

  14. Simulation of the mechanical behavior of a HIP implant. Implant fixed to bone by cementation under arbitrary load

    Science.gov (United States)

    Oldani, C. R.; Dominguez, A. A.

    2007-11-01

    In a previous work a finite elements model was constructed to simulate a fatigue assay according to the norm IRAM 9422-3. Three materials were studied, two of them are the most used in this type of implant (Stainless steel 3161 and alloy T16A14V) and the third was a new developed titanium alloy (Ti35Nb7Zr5Ta). Static loads were applied to the model according to the highest requirements of the norm and the stress - strain distribution were determined. In this study a simplified analysis of the material's fatigue was done according to the previous work. The best behavior of the titanium alloys vs. the stainless steel was evident. With the objective of studying the behavior of both: the implant and the femur bone, new finite elements models were realized, in which the presence of the bone was considered. Inside the bone, the femoral component of the implant was placed in a similar way of a cemented prosthesis in a total hip arthroplasty. The advantage of the titanium implant related to the stainless steel one, was very clear.

  15. Simulation of the mechanical behavior of a HIP implant. Implant fixed to bone by cementation under arbitrary load

    Energy Technology Data Exchange (ETDEWEB)

    Oldani, C R [Materials Department - FCEFyN - Universidad Nacional de Cordoba, Av.Velez Sarsfield 1611 (5016) Cordoba (Argentina); Dominguez, A A [INTI Cordoba, Av. Velez Sarsfield 1561 (5016) Cordoba (Argentina)

    2007-11-15

    In a previous work a finite elements model was constructed to simulate a fatigue assay according to the norm IRAM 9422-3. Three materials were studied, two of them are the most used in this type of implant (Stainless steel 3161 and alloy T16A14V) and the third was a new developed titanium alloy (Ti35Nb7Zr5Ta). Static loads were applied to the model according to the highest requirements of the norm and the stress - strain distribution were determined. In this study a simplified analysis of the material's fatigue was done according to the previous work. The best behavior of the titanium alloys vs. the stainless steel was evident. With the objective of studying the behavior of both: the implant and the femur bone, new finite elements models were realized, in which the presence of the bone was considered. Inside the bone, the femoral component of the implant was placed in a similar way of a cemented prosthesis in a total hip arthroplasty. The advantage of the titanium implant related to the stainless steel one, was very clear.

  16. Immediate loading versus immediate provisionalization of maxillary single-tooth replacements: a prospective randomized study with BioComp implants

    NARCIS (Netherlands)

    Lindeboom, Jerome A.; Frenken, Joost W.; Dubois, Leander; Frank, Michael; Abbink, Ingmar; Kroon, Frans H.

    2006-01-01

    PURPOSE: The aim of this prospective randomized study was to evaluate the clinical outcome of immediately loaded solid plasma sprayed (TPS) BioComp (BioComp Industries BV, Vught, The Netherlands) implants versus immediate provisionalized but non-loaded BioComp implants in the anterior and premolar

  17. Influence of the implant abutment types and the dynamic loading on initial screw loosening

    Science.gov (United States)

    Kim, Eun-Sook

    2013-01-01

    PURPOSE This study examined the effects of the abutment types and dynamic loading on the stability of implant prostheses with three types of implant abutments prepared using different fabrication methods by measuring removal torque both before and after dynamic loading. MATERIALS AND METHODS Three groups of abutments were produced using different types of fabrication methods; stock abutment, gold cast abutment, and CAD/CAM custom abutment. A customized jig was fabricated to apply the load at 30° to the long axis. The implant fixtures were fixed to the jig, and connected to the abutments with a 30 Ncm tightening torque. A sine curved dynamic load was applied for 105 cycles between 25 and 250 N at 14 Hz. Removal torque before loading and after loading were evaluated. The SPSS was used for statistical analysis of the results. A Kruskal-Wallis test was performed to compare screw loosening between the abutment systems. A Wilcoxon signed-rank test was performed to compare screw loosening between before and after loading in each group (α=0.05). RESULTS Removal torque value before loading and after loading was the highest in stock abutment, which was then followed by gold cast abutment and CAD/CAM custom abutment, but there were no significant differences. CONCLUSION The abutment types did not have a significant influence on short term screw loosening. On the other hand, after 105 cycles dynamic loading, CAD/CAM custom abutment affected the initial screw loosening, but stock abutment and gold cast abutment did not. PMID:23509006

  18. Porous, Dexamethasone-loaded polyurethane coatings extend performance window of implantable glucose sensors in vivo.

    Science.gov (United States)

    Vallejo-Heligon, Suzana G; Brown, Nga L; Reichert, William M; Klitzman, Bruce

    2016-01-01

    Continuous glucose sensors offer the promise of tight glycemic control for insulin dependent diabetics; however, utilization of such systems has been hindered by issues of tissue compatibility. Here we report on the in vivo performance of implanted glucose sensors coated with Dexamethasone-loaded (Dex-loaded) porous coatings employed to mediate the tissue-sensor interface. Two animal studies were conducted to (1) characterize the tissue modifying effects of the porous Dex-loaded coatings deployed on sensor surrogate implants and (2) investigate the effects of the same coatings on the in vivo performance of Medtronic MiniMed SOF-SENSOR™ glucose sensors. The tissue response to implants was evaluated by quantifying macrophage infiltration, blood vessel formation, and collagen density around implants. Sensor function was assessed by measuring changes in sensor sensitivity and time lag, calculating the Mean Absolute Relative Difference (MARD) for each sensor treatment, and performing functional glucose challenge test at relevant time points. Implants treated with porous Dex-loaded coatings diminished inflammation and enhanced vascularization of the tissue surrounding the implants. Functional sensors with Dex-loaded porous coatings showed enhanced sensor sensitivity over a 21-day period when compared to controls. Enhanced sensor sensitivity was accompanied with an increase in sensor signal lag and MARD score. These results indicate that Dex-loaded porous coatings were able to elicit an attenuated tissue response, and that such tissue microenvironment could be conducive towards extending the performance window of glucose sensors in vivo. In the present article, a coating to extend the functionality of implantable glucose sensors in vivo was developed. Our study showed that the delivery of an anti-inflammatory agent with the presentation of micro-sized topographical cues from coatings may lead to improved long-term glucose sensor function in vivo. We believe that

  19. Outcomes of different bearings in total hip arthroplasty - implant survival, revision causes, and patient-reported outcome

    DEFF Research Database (Denmark)

    Varnum, Claus

    2017-01-01

    ceramic-on-ceramic (CoC) THAs comparing them to those of "standard" metal-on-polyethylene (MoP) THAs. Study II: To compare the six-year revision risk for metal-on-metal (MoM) with that for MoP bearings in cementless stemmed THA, and further to study the revision risk for different designs of stemmed Mo...... for the outcome of THA is the type of bearings. This PhD thesis focuses on the influence of different types of bearings on implant survival, revision causes, PROMs, and noises from THA. The aims of the thesis were: Study I: To examine the revision risk and to investigate the causes of revision of cementless......M THAs and the causes of revision. Study III: To examine the association between CoC, MoM, and MoP bearings and both generic and disease-specific PROMs, and furthermore to examine the incidence and types of noises from the three types of bearings and identify the effect of noises on PROM scores. In study...

  20. In situ microradioscopy and microtomography of fatigue-loaded dental two-piece implants

    Energy Technology Data Exchange (ETDEWEB)

    Wiest, Wolfram; Zabler, Simon, E-mail: simon.zabler@physik.uni-wuerzburg.de [University of Würzburg (Germany); Rack, Alexander [European Synchrotron Radiation Facility (France); Fella, Christian; Balles, Andreas [University of Würzburg (Germany); Nelson, Katja; Schmelzeisen, Rainer [Medical Centre – University of Freiburg (Germany); Hanke, Randolf [University of Würzburg (Germany); Fraunhofer EZRT, Fürth (Germany)

    2015-10-09

    Results of a novel in situ microradiography and microtomography setup for the study of fatigue processes are presented. This setup is optimized for the requirements of dental implants and use at synchrotron imaging beamlines. Synchrotron real-time radioscopy and in situ microtomography are the only techniques providing direct visible information on a micrometre scale of local deformation in the implant–abutment connection (IAC) during and after cyclic loading. The microgap formation at the IAC has been subject to a number of studies as it has been proposed to be associated with long-term implant success. The next step in this scientific development is to focus on the in situ fatigue procedure of two-component dental implants. Therefore, an apparatus has been developed which is optimized for the in situ fatigue analysis of dental implants. This report demonstrates both the capability of in situ radioscopy and microtomography at the ID19 beamline for the study of cyclic deformation in dental implants. The first results show that it is possible to visualize fatigue loading of dental implants in real-time radioscopy in addition to the in situ fatigue tomography. For the latter, in situ microtomography is applied during the cyclic loading cycles in order to visualize the opening of the IAC microgap. These results concur with previous ex situ studies on similar systems. The setup allows for easily increasing the bending force, to simulate different chewing situations, and is, therefore, a versatile tool for examining the fatigue processes of dental implants and possibly other specimens.

  1. In situ microradioscopy and microtomography of fatigue-loaded dental two-piece implants

    International Nuclear Information System (INIS)

    Wiest, Wolfram; Zabler, Simon; Rack, Alexander; Fella, Christian; Balles, Andreas; Nelson, Katja; Schmelzeisen, Rainer; Hanke, Randolf

    2015-01-01

    Results of a novel in situ microradiography and microtomography setup for the study of fatigue processes are presented. This setup is optimized for the requirements of dental implants and use at synchrotron imaging beamlines. Synchrotron real-time radioscopy and in situ microtomography are the only techniques providing direct visible information on a micrometre scale of local deformation in the implant–abutment connection (IAC) during and after cyclic loading. The microgap formation at the IAC has been subject to a number of studies as it has been proposed to be associated with long-term implant success. The next step in this scientific development is to focus on the in situ fatigue procedure of two-component dental implants. Therefore, an apparatus has been developed which is optimized for the in situ fatigue analysis of dental implants. This report demonstrates both the capability of in situ radioscopy and microtomography at the ID19 beamline for the study of cyclic deformation in dental implants. The first results show that it is possible to visualize fatigue loading of dental implants in real-time radioscopy in addition to the in situ fatigue tomography. For the latter, in situ microtomography is applied during the cyclic loading cycles in order to visualize the opening of the IAC microgap. These results concur with previous ex situ studies on similar systems. The setup allows for easily increasing the bending force, to simulate different chewing situations, and is, therefore, a versatile tool for examining the fatigue processes of dental implants and possibly other specimens

  2. The effects of microhardnesses and friction coefficients of GCr15 and Cr4Mo4V bearing materials by ion implantation

    International Nuclear Information System (INIS)

    Yang Qifa; Xiang Deguang; Lu Haolin

    1988-01-01

    Some experimental results of microhardnesses and friction coefficients of GCr15 and Cr4Mo4V bearing materials which were implanted with Cr, Mo, N and B ions are reported in this paper. It is found that the microhardnesses are increased and the friction coefficients are reduced by Cr, Mo, N and B ion implantation for two materials. The friction coefficients of Cr + Mo + N , Cr + Mo + B ion implanted samples are reduced to 1/3 of the unimplanted samples

  3. Immediate Loading of Single Implants in the Anterior Maxilla: A 1-Year Prospective Clinical Study on 34 Patients

    Directory of Open Access Journals (Sweden)

    Miguel Stanley

    2017-01-01

    Full Text Available Purpose. To present the outcomes of immediately loaded single implants placed in the anterior maxilla. Methods. Over a 2-year period, all patients referred to a private clinic were considered for enrolment in this study. Inclusion criteria were single-tooth placement in postextraction sockets or healed sites of the anterior maxilla. All implants were immediately loaded and followed for a period of 1 year after the placement of definitive crowns. The outcome measures were implant stability, survival, and success. Results. 34 patients were selected and 43 tapered implants with a knife-edge thread design and a nanostructured, calcium-incorporated surface (Anyridge®, Megagen, Gyeongsang, Korea were installed. Two implants were not sufficiently stable at placement (ISQ < 60 and were considered failed for immediate loading; 41 implants had an ISQ ≥ 60 at placement and were immediately loaded. One year after the placement of definitive crowns, no implant failures were reported, for a survival rate of 100%. No biological complications were found, but 2 implants had their prosthetic abutments loosened: the implant success rate was 95.2%. Conclusions. In the present study on the immediate loading of single implants in the anterior maxilla, positive outcomes were reported, with high survival (100% and success (95.2% rates (the present study has been registered in the ISRCTN registry, a publicly available trial register recognized by WHO and ICMJE, with number ISRCTN12935478.

  4. No influence of simultaneous bone-substitute application on the success of immediately loaded dental implants: a retrospective cohort study.

    Science.gov (United States)

    Kopp, Sigmar; Behrend, Detlef; Kundt, Günther; Ottl, Peter; Frerich, Bernhard; Warkentin, Mareike

    2013-06-01

    To examine the influence of bone-substitute application during implantation on the success of immediately placed and loaded dental implants. A total of 147 consecutive patients (age, 16.5-80.4 years) were provided with 696 immediately loaded implants. The mean follow-up time was 34.1 months. Of these implants, 50.4% (n=351) were immediately placed into extraction sockets. A total of 119 implants were added by simultaneous bone-substitute application (NanoBone, Artoss GmbH, Rostock Germany), whereas the other implants were placed in healed bone. Univariate and multivariate analysis was performed using IBM SPSS V.20. The overall implant success rate was 96.1%. Implants with simultaneous bone replacement had a hazard ratio of 0.877 (p=0.837); 95% CI, 0.253-3.04). Factors found to be statistically significant modifiers of success on multivariate analysis (p<0.05) included type of superstructure (p<0.001), implant-abutment connection (p<0.001), membrane use (p=0.010), and jaw (p=0.026). None of the other factors investigated were significant modifiers. The present study demonstrates high success rates for immediately loaded implants and their superstructures independent of the simultaneous application of bone substitute. The declared aim of socket preservation, the prevention avoiding bone loss, is achieved in the immediate implant placement scenario under immediate-loading conditions.

  5. DESIGN OF STRUCTURAL ELEMENTS IN THE EVENT OF THE PRE-SET RELIABILITY, REGULAR LOAD AND BEARING CAPACITY DISTRIBUTION

    Directory of Open Access Journals (Sweden)

    Tamrazyan Ashot Georgievich

    2012-10-01

    Full Text Available Accurate and adequate description of external influences and of the bearing capacity of the structural material requires the employment of the probability theory methods. In this regard, the characteristic that describes the probability of failure-free operation is required. The characteristic of reliability means that the maximum stress caused by the action of the load will not exceed the bearing capacity. In this paper, the author presents a solution to the problem of calculation of structures, namely, the identification of reliability of pre-set design parameters, in particular, cross-sectional dimensions. If the load distribution pattern is available, employment of the regularities of distributed functions make it possible to find the pattern of distribution of maximum stresses over the structure. Similarly, we can proceed to the design of structures of pre-set rigidity, reliability and stability in the case of regular load distribution. We consider the element of design (a monolithic concrete slab, maximum stress S which depends linearly on load q. Within a pre-set period of time, the probability will not exceed the values according to the Poisson law. The analysis demonstrates that the variability of the bearing capacity produces a stronger effect on relative sizes of cross sections of a slab than the variability of loads. It is therefore particularly important to reduce the coefficient of variation of the load capacity. One of the methods contemplates the truncation of the bearing capacity distribution by pre-culling the construction material.

  6. Antibacterial activity of contact lenses bearing surface-immobilized layers of intact liposomes loaded with levofloxacin.

    Science.gov (United States)

    Danion, Anne; Arsenault, Isabelle; Vermette, Patrick

    2007-09-01

    In vitro methods to evaluate antibacterial activity were used with contact lenses bearing levofloxacin-loaded liposomes developed for the prevention and treatment of bacterial ocular infections such as keratitis. Levofloxacin was incorporated into liposomes before these intact liposomes were immobilized onto the surfaces of soft contact lenses using a multilayer immobilization strategy. The release of levofloxacin from contact lenses bearing 2, 5, and 10 layers of liposomes into a saline buffer at 37 degrees C was monitored by fluorescence. The levofloxacin release, as a function of time, was described by a mechanism taking into account two independent first-order kinetic models. The total release of levofloxacin from the contact lenses was completed within 6 days. The release of levofloxacin from contact lenses bearing 10 layers of liposomes and subsequently soaked overnight in a levofloxacin solution was also studied and compare to that of dried contact lenses without any chemical modification rehydrated in a levofloxacin solution. The antibacterial activity of the liposome-coated contact lenses against Staphylococcus aureus was evaluated by measuring (i) the diameters of the inhibition zone on an agar plate and (ii) the optical density using a broth assay. The liposome-coated lenses showed an antibacterial activity both on agar and in broth following 24 h. When initial bacteria inocula were equal or below 10(6) CFU/mL, all the bacteria were inhibited within 2 h. When using initial bacteria inocula of 10(8) CFU/mL, an initial burst release provided by soaking the liposomal lenses was required for the first hours to inhibit bacteria growth. (c) 2007 Wiley-Liss, Inc. and the American Pharmacists Association.

  7. Long-term evaluation of immediately loaded implants in the edentulous mandible using fixed bridges and platform shifting.

    Science.gov (United States)

    Romanos, Georgios E; Gaertner, Kathrin; Nentwig, Georg H

    2014-08-01

    The immediate loading concept has been extensively documented in the anterior part of the mandible when six primary stable implants are placed, splinted with a fixed prosthesis. The aim of this study was to evaluate the long-term success of immediately occlusal loaded implants with a progressive thread design and platform shifting in the edentulous mandible. Seventy-eight implants placed in 13 patients and were connected with their abutments immediately after surgery. The implants were splinted using a fixed temporary restoration having occlusal contacts in the centric and group function in the lateral movements of the mandible (immediate occlusal loading). The patients were advised to use soft/liquid diet for the first 6 to 8 weeks of healing in order to reduce excessive loading in the bone-to-implant interface. Abutment level impressions were taken without removing the abutments in order to fabricate the final prostheses. The final restorations were delivered 4 to 8 weeks after surgery and cemented temporarily in order to evaluate the peri-implant soft tissue condition at the different time intervals after removal of the restoration. Clinical stability and radiological indices were evaluated at the start of loading, at 3-month interval after loading, and then annually. After a mean loading period of 75.29 (± 38.18) months, no implant was lost (100% success rate). All clinical indices had values in normal levels. The Periotest values demonstrated a continuous reduction, representing high stability. The crestal bone level was relatively stable and only minimal crestal bone loss was observed in some implants. Long-term success and stability of the peri-implant tissues around immediately loaded mandibular implants are expected when implants with platform shifting are restored with bridges without abutment removal. © 2013 Wiley Periodicals, Inc.

  8. Load bearing capacity of welded joints between dissimilar pipelines with unequal wall thickness

    Energy Technology Data Exchange (ETDEWEB)

    Beak, Jonghyun; Kim, Youngpyo; Kim, Woosik [Korea Gas Corporation, Suwon (Korea, Republic of)

    2012-09-15

    The behavior of the load bearing capacity of a pipeline with unequal wall thickness was evaluated using finite element analyses. Pipelines with a wall thickness ratio of 1.22-1.89 were adopted to investigate plastic collapse under tensile, internal pressure, or bending stress. A parametric study showed that the tensile strength and moment of a pipeline with a wall thickness ratio less than 1.5 were not influenced by the wall thickness ratio and taper angle; however, those of a pipeline with a wall thickness ratio more than 1.5 decreased considerably at a low taper angle. The failure pressure of a pipeline with unequal wall thickness was not influenced by the wall thickness ratio and taper angle.

  9. Hierarchical cellular designs for load-bearing biocomposite beams and plates

    International Nuclear Information System (INIS)

    Burgueno, Rigoberto; Quagliata, Mario J.; Mohanty, Amar K.; Mehta, Geeta; Drzal, Lawrence T.; Misra, Manjusri

    2005-01-01

    Scrutiny into the composition of natural, or biological materials convincingly reveals that high material and structural efficiency can be attained, even with moderate-quality constituents, by hierarchical topologies, i.e., successively organized material levels or layers. The present study demonstrates that biologically inspired hierarchical designs can help improve the moderate properties of natural fiber polymer composites or biocomposites and allow them to compete with conventional materials for load-bearing applications. An overview of the mechanics concepts that allow hierarchical designs to achieve higher performance is presented, followed by observation and results from flexural tests on periodic and hierarchical cellular beams and plates made from industrial hemp fibers and unsaturated polyester resin biocomposites. The experimental data is shown to agree well with performance indices predicted by mechanics models. A procedure for the multi-scale integrated material/structural analysis of hierarchical cellular biocomposite components is presented and its advantages and limitations are discussed

  10. Biodynamic feedback training to assure learning partial load bearing on forearm crutches.

    Science.gov (United States)

    Krause, Daniel; Wünnemann, Martin; Erlmann, Andre; Hölzchen, Timo; Mull, Melanie; Olivier, Norbert; Jöllenbeck, Thomas

    2007-07-01

    To examine how biodynamic feedback training affects the learning of prescribed partial load bearing (200N). Three pre-post experiments. Biomechanics laboratory in a German university. A volunteer sample of 98 uninjured subjects who had not used crutches recently. There were 24 subjects in experiment 1 (mean age, 23.2y); 64 in experiment 2 (mean age, 43.6y); and 10 in experiment 3 (mean age, 40.3y), parallelized by arm force. Video instruction and feedback training: In experiment 1, 2 varied instruction videos and reduced feedback frequency; in experiment 2, varied frequencies of changing tasks (contextual interference); and in experiment 3, feedback training (walking) and transfer (stair tasks). Vertical ground reaction force. Absolute error of practiced tasks was significantly reduced for all samples (Pstairs might be beneficial.

  11. Silk as a biocohesive sacrificial binder in the fabrication of hydroxyapatite load bearing scaffolds.

    Science.gov (United States)

    McNamara, Stephanie L; Rnjak-Kovacina, Jelena; Schmidt, Daniel F; Lo, Tim J; Kaplan, David L

    2014-08-01

    Limitations of current clinical methods for bone repair continue to fuel the demand for a high strength, bioactive bone replacement material. Recent attempts to produce porous scaffolds for bone regeneration have been limited by the intrinsic weakness associated with high porosity materials. In this study, ceramic scaffold fabrication techniques for potential use in load-bearing bone repairs have been developed using naturally derived silk from Bombyx mori. Silk was first employed for ceramic grain consolidation during green body formation, and later as a sacrificial polymer to impart porosity during sintering. These techniques allowed preparation of hydroxyapatite (HA) scaffolds that exhibited a wide range of mechanical and porosity profiles, with some displaying unusually high compressive strength up to 152.4 ± 9.1 MPa. Results showed that the scaffolds exhibited a wide range of compressive strengths and moduli (8.7 ± 2.7 MPa to 152.4 ± 9.1 MPa and 0.3 ± 0.1 GPa to 8.6 ± 0.3 GPa) with total porosities of up to 62.9 ± 2.7% depending on the parameters used for fabrication. Moreover, HA-silk scaffolds could be molded into large, complex shapes, and further machined post-sinter to generate specific three-dimensional geometries. Scaffolds supported bone marrow-derived mesenchymal stem cell attachment and proliferation, with no signs of cytotoxicity. Therefore, silk-fabricated HA scaffolds show promise for load bearing bone repair and regeneration needs. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. Biomimetic nanocomposites of carboxymethyl cellulose-hydroxyapatite: novel three dimensional load bearing bone grafts.

    Science.gov (United States)

    Garai, Subhadra; Sinha, Arvind

    2014-03-01

    An innovative biomimetic synthesis of novel three dimensional micro/macro porous carboxymethyl cellulose (CMC)-hydroxyapatite (HA) nanocomposites having four systematically different compositions has been established for its possible application as a load bearing synthetic bone graft. Our process, being in situ, involves a simple and cost effective route akin to a matrix mediated biomineralization process. Developed synthesis route not only controls the size of HA particles in the range of 15-50 nm, embedded in CMC matrix, but also assists in the formation of a mechanically strong three dimensional nanocomposite structures due to physical cross linking of HA impregnated CMC matrix. The process does not involve any toxic cross linker and works at near ambient conditions. The nanocomposites are systematically structurally and mechanically characterized using various techniques like scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform IR (FTIR), solid state (13)C nuclear magnetic resonance ((13)C NMR), thermo-gravimetric analysis (TGA) and Universal mechanical test. It reveals that the ionic/polar or electrostatic interactions are the main driving force for formation of load bearing three dimensional nanocomposites via a process similar to matrix mediated biomineralization. Compressive strength and compressive modulus of nanocomposites, being in the range of 1.74-12 MPa and 157-330 MPa, respectively, meet the desired range of compressive strength for the synthetic grafts used in cancellous bone. An increase in the compressive strength with increase in the porosity has been an interesting observation in the present study. In vitro cytotoxicity of the synthesized nanocomposites has been evaluated using bone marrow mesenchymal stem cells (BMSC) isolated from Wistar rat. Copyright © 2013 Elsevier B.V. All rights reserved.

  13. Repair of segmental load-bearing bone defect by autologous mesenchymal stem cells and plasma-derived fibrin impregnated ceramic block results in early recovery of limb function.

    Science.gov (United States)

    Ng, Min Hwei; Duski, Suryasmi; Tan, Kok Keong; Yusof, Mohd Reusmaazran; Low, Kiat Cheong; Rose, Isa Mohamed; Mohamed, Zahiah; Bin Saim, Aminuddin; Idrus, Ruszymah Bt Hj

    2014-01-01

    Calcium phosphate-based bone substitutes have not been used to repair load-bearing bone defects due to their weak mechanical property. In this study, we reevaluated the functional outcomes of combining ceramic block with osteogenic-induced mesenchymal stem cells and platelet-rich plasma (TEB) to repair critical-sized segmental tibial defect. Comparisons were made with fresh marrow-impregnated ceramic block (MIC) and partially demineralized allogeneic bone block (ALLO). Six New Zealand White female rabbits were used in each study group and three rabbits with no implants were used as negative controls. By Day 90, 4/6 rabbits in TEB group and 2/6 in ALLO and MIC groups resumed normal gait pattern. Union was achieved significantly faster in TEB group with a radiological score of 4.50 ± 0.78 versus ALLO (1.06 ± 0.32), MIC (1.28 ± 0.24), and negative controls (0). Histologically, TEB group scored the highest percentage of new bone (82% ± 5.1%) compared to ALLO (5% ± 2.5%) and MIC (26% ± 5.2%). Biomechanically, TEB-treated tibiae achieved the highest compressive strength (43.50 ± 12.72 MPa) compared to those treated with ALLO (15.15 ± 3.57 MPa) and MIC (23.28 ± 6.14 MPa). In conclusion, TEB can repair critical-sized segmental load-bearing bone defects and restore limb function.

  14. Positive Contrast MRI Techniques for Visualization of Iron-Loaded Hernia Mesh Implants in Patients.

    Directory of Open Access Journals (Sweden)

    Alexander Ciritsis

    Full Text Available In MRI, implants and devices can be delineated via susceptibility artefacts. To discriminate susceptibility voids from proton-free structures, different positive contrast techniques were implemented. The purpose of this study was to evaluate a pulse sequence-based positive contrast technique (PCSI and a post-processing susceptibility gradient mapping algorithm (SGM for visualization of iron loaded mesh implants in patients.Five patients with iron-loaded MR-visible inguinal hernia mesh implants were examined at 1.5 Tesla. A gradient echo sequence (GRE; parameters: TR: 8.3ms; TE: 4.3ms; NSA:2; FA:20°; FOV:350mm² and a PCSI sequence (parameters: TR: 25ms; TE: 4.6ms; NSA:4; FA:20°; FOV:350mm² with on-resonant proton suppression were performed. SGM maps were calculated using two algorithms. Image quality and mesh delineation were independently evaluated by three radiologists.On GRE, the iron-loaded meshes generated distinct susceptibility-induced signal voids. PCSI exhibited susceptibility differences including the meshes as hyperintense signals. SGM exhibited susceptibility differences with positive contrast. Visually, the different algorithms presented no significant differences. Overall, the diagnostic value was rated best in GRE whereas PCSI and SGM were barely "sufficient".Both "positive contrast" techniques depicted implanted meshes with hyperintense signal. SGM comes without additional acquisition time and can therefore be utilized in every patient.

  15. Mathematical solution of the stone column effect on the load bearing capacity and settlement using numerical analysis

    Science.gov (United States)

    Madun, A.; Meghzili, S. A.; Tajudin, SAA; Yusof, M. F.; Zainalabidin, M. H.; Al-Gheethi, A. A.; Dan, M. F. Md; Ismail, M. A. M.

    2018-04-01

    The most important application of various geotechnical construction techniques is for ground improvement. Many soil improvement project had been developed due to the ongoing increase in urban and industrial growth and the need for greater access to lands. Stone columns are one of the best effective and feasible techniques for soft clay soil improvement. Stone columns increase the bearing capacity and reduce the settlement of soil. Finite element analyses were performed using the program PLAXIS 2D. An elastic-perfectly plastic constitutive relation, based on the Mohr–Coulomb criterion, governs the soft clay and stone column behaviour. This paper presents on how the response surface methodology (RSM) software is used to optimize the effect of the diameters and lengths of column on the load bearing capacity and settlement of soft clay. Load tests through the numerical modelling using Plaxis 2D were carried out on the loading plate at 66 mm. Stone column load bearing capacity increases with the increasing diameter of the column and settlement decreases with the increasing length of the column. Results revealed that the bigger column diameter, the higher load bearing capacity of soil while the longer column length, the lower settlement of soil. However, the optimum design of stone column was varied with each factor (diameter and length) separately for improvement.

  16. Constructive systems, load-bearing and enclosing structures of high-rise buildings

    Science.gov (United States)

    Anatol'evna Korol', Elena; Olegovna Kustikova, Yuliya

    2018-03-01

    As the height of the building increases, loads on load-carrying structures increase dramatically, and as a result of the development of high-rise construction, several structural systems of such buildings have been developed: frame, frame-frame, cross-wall, barrel, box-type, box-to-wall ("pipe in pipe", "Trumpet in the farm"), etc. In turn, the barrel systems have their own versions: cantilever support of the ceilings on the trunk, suspension of the outer part of the overlap to the upper carrying console "hanging house" or its support by means of the walls on the lower bearing cantilever, intermediate position of the supporting cantilevers in height to the floor, from a part of floors. The object of the study are the structural solutions of high-rise buildings. The subject of the study is the layout of structural schemes of high-rise buildings, taking into account the main parameters - altitude (height), natural climatic conditions of construction, materials of structural elements and their physical and mechanical characteristics. The purpose of the study is to identify the features and systematization of structural systems of high-rise buildings and the corresponding structural elements. The results of the research make it possible, at the stage of making design decisions, to establish rational parameters for the correspondence between the structural systems of high-rise buildings and their individual elements.

  17. Macroscopic and microscopic evaluation of a new implant design supporting immediately loaded full arch rehabilitation.

    Science.gov (United States)

    Tetè, Stefano; Zizzari, Vincenzo; De Carlo, Alessandro; Sinjari, Bruna; Gherlone, Enrico

    2012-04-01

    The purpose of this study is to evaluate macroscopic and microscopic appearance of a new implant design, with particular emphasis given to the type of prosthesis connection. Two dental implants of the same type (Torque Type(®), WinSix(®), BioSAFin. S.r.l. - Ancona, Italy), with sandblasted and acid etched surfaces (Micro Rough Surface(®)), but differing from each other for the prosthesis connection system, were examined by scanning electron microscope (SEM) analysis at different magnifications: TTI implant, with a hexagonal internal connection, and TTX implant, with a hexagonal external connection. SEM analysis showed that the Torque Type(®) implant is characterized by a truncated cone shape with tapered tips. The implant body showed a double loop thread and double pitch with blunt tips. For both types of connection, the implant neck was 0.7 mm in height with a 3% taper. This implant design may be able to guarantee osteotomic properties at the time of insertion in a surgical site suitably prepared, a facilitated screwing, thanks to the thread pitch and to the broad and deep draining grooves, thereby ensuring a good primary stability. The different connection design appears defined and precise, in order to ensure a good interface between the fixture and the prosthetic components. Therefore, this design appears to be particularly suitable in cases where a good primary stability is necessary and a precise coupling between endosseous and prosthetic components, as it allows an easy insertion of the fixture even in conditions of reduced bone availability, and in cases of immediately loaded full-arch rehabilitations.

  18. Marginal bone-level alterations of loaded zirconia and titanium dental implants: an experimental study in the dog mandible.

    Science.gov (United States)

    Thoma, Daniel S; Benic, Goran I; Muñoz, Fernando; Kohal, Ralf; Sanz Martin, Ignacio; Cantalapiedra, Antonio G; Hämmerle, Christoph H F; Jung, Ronald E

    2016-04-01

    The aim was to test whether or not the marginal bone-level alterations of loaded zirconia implants are similar to the bone-level alterations of a grade 4 titanium one-piece dental implant. In six dogs, all premolars and the first molars were extracted in the mandible. Four months later, three zirconia implants (BPI, VC, ZD) and a control titanium one-piece (STM) implant were randomly placed in each hemimandible and left for transmucosal healing (baseline). Six months later, CAD/CAM crowns were cemented. Sacrifice was scheduled at 6-month postloading. Digital X-rays were taken at implant placement, crowns insertion, and sacrifice. Marginal bone-level alterations were calculated, and intra- and intergroup comparisons performed adjusted by confounding factors. Implants were successfully placed. Until crown insertion, two implants were fractured (one VC, one ZD). At sacrifice, 5 more implants were (partly) fractured (one BPI, four ZD), and one lost osseointegration (VC). No decementation of crowns occurred. All implant systems demonstrated a statistically significant (except VC) loss of marginal bone between baseline and crown insertion ranging from 0.29 mm (VC; P = 0.116) to 0.80 mm (ZD; P = 0.013). The estimated marginal bone loss between baseline and 6 months of loading ranged between 0.19 mm (BPI) and 1.11 mm (VC), being statistically significant for STM and VC only (P implants and control implants (STM vs. BPI P = 0.007; vs. VC P = 0.001; vs. ZD P = 0.011). Zirconia implants were more prone to fracture prior to and after loading with implant-supported crowns compared to titanium implants. Individual differences and variability in the extent of the bone-level changes during the 12-month study period were found between the different implant types and materials. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  19. Settling of abutments into implants and changes in removal torque in five different implant-abutment connections. Part 1: Cyclic loading.

    Science.gov (United States)

    Kim, Ki-Seong; Han, Jung-Suk; Lim, Young-Jun

    2014-01-01

    The aim of this study was to evaluate and compare the settling of abutments into implants and the removal torque values (RTVs) before and after cyclic loading. Five different implant-abutment connections were tested: Ext = external butt joint + two-piece abutment; Int-H2 = internal hexagon + two-piece abutment; Int-H1 = internal hexagon + one-piece abutment; Int-O2 = internal octagon + two-piece abutment; and Int-O1 = internal octagon + one-piece abutment. Ten abutments from each group were secured to their corresponding implants (total n = 50). All samples were tested in a universal testing machine with a vertical load of 250 N for 100,000 cycles of 14 Hz. The amount of settling of the abutment into the implant was calculated from the change in the total length of the implant-abutment sample before and after loading, as measured with an electronic digital micrometer. The RTV after cyclic loading was compared to the initial RTV with a digital torque gauge. Statistical analysis was performed at a 5% significance level. A multiple-comparison test showed specific significant differences in settling values in each group after 250 N cyclic loading (Int-H1, Ext abutment type and related to the design characteristics of the implant-abutment connection.

  20. Clinical outcomes of immediate/early loading of dental implants. A literature review of recent controlled prospective clinical studies.

    Science.gov (United States)

    Sennerby, L; Gottlow, J

    2008-06-01

    Two previous reviews have evaluated the clinical outcomes of immediate/early loading of dental implants based on studies published until 2005.(1,2) The aim of the present paper was to review controlled clinical studies on the subject published since 2005 including at least 10 patients in each group followed for at least one year in function. Six comparative studies were found and none of these showed any differences in survival rates or marginal bone loss after one to five years. Most authors used specified inclusion criteria to avoid known risk factors such as soft bone, short implants and bruxism. Data from one randomized study in the edentulous maxilla showed no differences between early and delayed loading in consecutive clinical routine cases including short implants and soft bone. Three additional studies comparing different surfaces or implant designs under immediate loading were reviewed. No differences between implants with a moderately rough or smooth surface topography were observed. The data add to the previous bulk of evidence that various designs of implants can be loaded shortly after their placement in both the mandible and the maxilla. However, one study reported on marginal bone loss around a novel one-piece implant design leading to implant failure which was not seen for control two-piece implants.(3).

  1. Early Loading of Single-Piece Implant for Partially Edentulous Posterior Arch: A Prospective One-Year Case Report

    Directory of Open Access Journals (Sweden)

    Amol Beldar

    2013-01-01

    Full Text Available Implant therapy is now well established, and there is an increasing need for shorter rehabilitation time. Original prerequisites of osseointegration have been reassessed to satisfy continuously increasing patient's expectation of reduced treatment time, improved esthetics, and increased comfort. Shorter healing time may be appropriate in some circumstances, and examples of early loading have been reported in animal and human studies. However, to date there are insufficient data to determine a universally acceptable opinion on early loading of implants for single-tooth replacement. This case report involves early loading, combined with construction of a restoration, inserted directly after 6 weeks of implant surgery and followup of one year.

  2. 3D finite element analysis of immediate loading of single wide versus double implants for replacing mandibular molar

    Directory of Open Access Journals (Sweden)

    Shrikar R Desai

    2013-01-01

    Full Text Available Purpose: The purpose of this finite element study was to compare the stresses, strains, and displacements of double versus single implant in immediate loading for replacing mandibular molar. Materials and Methods: Two 3D FEM (finite element method models were made to simulate implant designs. The first model used 5-mm-wide diameter implant to support a single molar crown. The second model used 3.75-3.75 double implant design. Anisotropic properties were assigned to bone model. Each model was analyzed with single force magnitude (100 N in vertical axis. Results: This FEM study suggested that micromotion can be controlled better for double implants compared to single wide-diameter implants. The Von Mises stress for double implant showed 74.44% stress reduction compared to that of 5-mm implant. The Von Mises elastic strain was reduced by 61% for double implant compared to 5-mm implant. Conclusion: Within the limitations of the study, when the mesiodistal space for artificial tooth is more than 12.5 mm, under immediate loading, the double implant support should be considered.

  3. Urinary morbidity with a modified peripheral loading technique of transperineal 125i prostate implantation

    International Nuclear Information System (INIS)

    Brown, Douglas; Colonias, Athanasios; Miller, Ralph; Benoit, Ronald; Cohen, Jeffrey; Arshoun, Youssef; Galloway, Michael; Karlovits, Stephen; Wu, Andrew; Johnson, Mark; Quinn, Annette; Kalnicki, Shalom

    2000-01-01

    Purpose: Analysis of urinary morbidity within the first 12 months following a modified peripheral loading technique for permanent transperineal transrectal ultrasound (TRUS) guided 125 I prostate implantation and comparison of urinary morbidity with various clinical and implant parameters. Materials and Methods: Between October 1, 1996, and March 11, 1998, 87 patients with favorable, early stage prostate cancer were treated with permanent transperineal TRUS guided 125 I prostate implantation. A peripheral loading technique was utilized for source placement with 75-80% source distribution in the periphery and 20-25% source distribution centrally. A mean total activity of 38 mCi of 125 I was implanted (range, 19-66 mCi). The mean source activity was 0.43 mCi/source (range, 0.26-0.61 mCi/source) and the mean number of sources implanted was 88 (range, 56-134). The minimum prescribed dose to the prostate was 145 Gy. The median D 90 , V 100 , and V 150 were 152 Gy (range, 104-211 Gy), 92% (range, 71-99%), and 61% (range, 11-89%), respectively. The median follow-up time was 19 months (range, 12-29 months). Urinary morbidity was scored at 3 weeks and then at 3-month intervals for the first 2 years using a modified Radiation Therapy Oncology Group (RTOG) grading system (scale 0-5). Results: Most patients developed at least minor urinary symptoms with frequency or nocturia being the most common. Overall, 79% (69/87) of patients experienced urinary morbidity with 21% (18/87) reporting no symptoms. The incidence of overall Grade 1 urinary morbidity was 37% (32/87); Grade 2 morbidity was 37% (32/87); and Grade 3 morbidity was 6% (5/87). There was no Grade 4 or 5 morbidity. The incidence of Grade 0 frequency/nocturia was 36% (31/87); Grade 1 was 33% (29/87); Grade 2 was 30% (26/87); and Grade 3 was 1% (1/87). Grade 0 dysuria was seen in 56% (49/87) of patients; 32% (28/87) had Grade 1; 10% (9/87) Grade 2; and 1% (1/87) Grade 3 dysuria. Most urinary symptoms started a few weeks

  4. Varying stiffness and load distributions in defective ball bearings: Analytical formulation and application to defect size estimation

    Science.gov (United States)

    Petersen, Dick; Howard, Carl; Prime, Zebb

    2015-02-01

    This paper presents an analytical formulation of the load distribution and varying effective stiffness of a ball bearing assembly with a raceway defect of varying size, subjected to static loading in the radial, axial and rotational degrees of freedom. The analytical formulation is used to study the effect of the size of the defect on the load distribution and varying stiffness of the bearing assembly. The study considers a square-shaped outer raceway defect centered in the load zone and the bearing is loaded in the radial and axial directions while the moment loads are zero. Analysis of the load distributions shows that as the defect size increases, defect-free raceway sections are subjected to increased static loading when one or more balls completely or partly destress when positioned in the defect zone. The stiffness variations that occur when balls pass through the defect zone are significantly larger and change more rapidly at the defect entrance and exit than the stiffness variations that occur for the defect-free bearing case. These larger, more rapid stiffness variations generate parametric excitations which produce the low frequency defect entrance and exit events typically observed in the vibration response of a bearing with a square-shaped raceway defect. Analysis of the stiffness variations further shows that as the defect size increases, the mean radial stiffness decreases in the loaded radial and axial directions and increases in the unloaded radial direction. The effects of such stiffness changes on the low frequency entrance and exit events in the vibration response are simulated with a multi-body nonlinear dynamic model. Previous work used the time difference between the low frequency entrance event and the high frequency exit event to estimate the size of the defect. However, these previous defect size estimation techniques cannot distinguish between defects that differ in size by an integer number of the ball angular spacing, and a third feature

  5. Effects of Food Texture on Three-Dimensional Loads on Implants During Mastication Based on In Vivo Measurements.

    Science.gov (United States)

    Yoda, Nobuhiro; Ogawa, Toru; Gunji, Yoshinori; Vanegas, Juan R; Kawata, Tetsuo; Sasaki, Keiichi

    2016-08-01

    The mechanisms by which the loads exerted on implants that support prostheses are modulated during mastication remain unclear. The purpose of this study was to evaluate the effects of food texture on 3-dimensional loads measured at a single implant using a piezoelectric transducer. Two subjects participated in this study. The transducer and the experimental superstructure, which had been adjusted to the subject's occlusal scheme, were attached to the implant with a titanium screw. The foods tested were chewing gum and peanuts. The mean maximum load on the implant in each chewing cycle was significantly higher during peanut chewing than during gum chewing. The direction of maximum load was significantly more widely dispersed during peanut chewing than during gum chewing. The range of changes in load direction during the force-increasing phase of each chewing cycle was significantly wider during peanut chewing than during gum chewing. The load on the implant was affected by food texture in both subjects. This measurement method can be useful to investigate the mechanisms of load modulation on implants during mastication.

  6. Radial power distribution shaping within a PWR fuel assembly utilizing asymmetrically loaded gadolinia-bearing fuel pins

    International Nuclear Information System (INIS)

    Stone, I.Z.

    1992-01-01

    As in-core fuel management designs evolve to meet the demands of increasing energy output, more innovative methods are developed to maintain power peaking within acceptable thermal margin limits. In-core fuel management staff must utilize various loading pattern strategies such as cross-core movement of fuel assemblies, multibatch enrichment schemes, and burnable absorbers as the primary means of controlling the radial power distribution. The utilization of fresh asymmetrically loaded gadolinia-bearing assemblies as a fuel management tool provides an additional means of controlling the radial power distribution. At Siemens Nuclear Power Corporation (SNP), fresh fuel assemblies fabricated with asymmetrically loaded gadolinia-bearing fuel rods have been used successfully for several cycles of reactor operation. Asymmetric assemblies are neutronically modeled using the same tools and models that SNP uses to model symmetrically loaded gadolinia-bearing fuel assemblies. The CASMO-2E code is used to produce the homogenized macroscopic assembly cross sections for the nodal core simulator. Optimum fuel pin locations within the asymmetrical assembly are determined using the pin-by-pin PDQ7 assembly core model for each new assembly design. The optimum pin location is determined by the rod loading that minimizes the peak-to-average pin power

  7. H-M bearing capacity of a modified suction caisson determined by using load-/displacement-controlled methods

    Science.gov (United States)

    Zhang, Yu-kun; Gao, Yu-feng; Li, Da-yong; Mahfouz, Ali H.

    2016-12-01

    This paper presents a series of monotonically combined lateral loading tests to investigate the bearing capacity of the MSCs (modified suction caissons) in the saturated marine fine sand. The lateral loads were applied under load- and displacement-controlled methods at the loading eccentricity ratios of 1.5, 2.0 and 2.5. Results show that, in the displacement-controlled test, the deflection-softening behavior of load-deflection curves for MSCs was observed, and the softening degree of the load-deflection response increased with the increasing external skirt length or the decreasing loading eccentricity. It was also found that the rotation center of the MSC at failure determined by the load-controlled method is slightly lower than that by the displacement-controlled method. The calculated MSC capacity based on the rotation center position in serviceability limit state is relatively conservative, compared with the calculated capacity based on the rotation center position in the ultimate limit state. In the limit state, the passive earth pressures opposite the loading direction under load- and displacement-controlled methods decrease by 46% and 74% corresponding to peak values, respectively; however, the passive earth pressures in the loading direction at failure only decrease by approximately 3% and 7%, compared with their peak values.

  8. New conceptual copper alloy bearing for diesel engine to achieve longer life under higher load; Diesel engine yo komen`atsu chojumyo jikuuke no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Tomikawa, T; Oshiro, H; Hashizume, K; Kamiya, S [Taiho Kogyo Co. Ltd., Aichi (Japan)

    1997-10-01

    Recently, the requirement like higher output, lower fuel consumption and cleaner exhaust gas for automotive engines has been increased. As a result, especially, higher bearing performance is required for diesel engine under a higher unit load and longer period. For this reason, we have developed the new conceptual copper alloy bearing to achieve higher performance under a higher unit load. This paper describes about the performance of this new bearing material. 3 refs., 12 figs., 5 tabs.

  9. Influence of bearing pre-load coefficient on shaft vibration and pad temperature in a hydroturbine generator unit. A case study

    Energy Technology Data Exchange (ETDEWEB)

    Feng Fuzhou; Chu Fulei; Guo Dan; Lu Wenxiu [Tsinghua Univ., Beijing, BJ (China). Dept. of Precision Instruments

    2001-07-01

    From data collected by an online condition monitoring and fault diagnosis system, a higher pad temperature at the upper guide bearing in a pumped storage power generator unit installed in Guangdong province(GPSPS), China, was found. And also a relatively intensive shaft vibration occurred at the lower guide bearing. By calculating the Reynolds equation and viscosity-temperature equation of the lubricant, a curve between the pre-load coefficient and the increment of pad temperature is obtained, which shows that the larger, the pre-load coefficient, the bigger, the increment of pad temperature. For a practical unit in GPSPS, by employing Transfer matrix method and Wilson-{theta} method to analyze shaft vibration at different pre-load coefficients of the whole bearing or ''pad pair'' bearings, the results show that the larger the pre-load coefficient is, the smaller the vibration amplitude is, the shorter the time for vibration to become steady is. And an uneven pre-load coefficient of the ''pad pair'' bearings will cause shaft orbit from a circle to an ellipse whose long axes is at the direction of the ''pad pair'' with the lowest pre-load coefficient. Finally, reasons of higher pad temperature of the upper guide bearing and larger shaft vibration at the lower guide bearing are due to the inconsistent relation of bearing assembling clearance or pre-load coefficient of the upper and lower guide bearing, and also due to the too small, uneven pre-load coefficient of ''pad pair'' bearings. After a scheme for adjusting the bearing clearance is given, data measured show that the analysis and simulation methods are correct and the adjustment scheme to the assembling clearance of the upper and lower guide bearings is feasible and can be used to guide the field maintenance conveniently. (orig.)

  10. Mechanical and thermo-mechanical response of a lead-core bearing device subjected to different loading conditions

    Directory of Open Access Journals (Sweden)

    Zhelyazov Todor

    2018-01-01

    Full Text Available The contribution is focused on the numerical modelling, simulation and analysis of a lead-core bearing device for passive seismic isolation. An accurate finite element model of a lead-core bearing device is presented. The model is designed to analyse both mechanical and thermo-mechanical responses of the seismic isolator to different loading conditions. Specifically, the mechanical behaviour in a typical identification test is simulated. The response of the lead-core bearing device to circular sinusoidal paths is analysed. The obtained shear displacement – shear force relationship is compared to experimental data found in literature sources. The hypothesis that heating of the lead-core during cyclic loading affects the degrading phenomena in the bearing device is taken into account. Constitutive laws are defined for each material: lead, rubber and steel. Both predefined constitutive laws (in the used general–purpose finite element code and semi-analytical procedures aimed at a more accurate modelling of the constitutive relations are tested. The results obtained by finite element analysis are to be further used to calibrate a macroscopic model of the lead-core bearing device seen as a single-degree-of-freedom mechanical system.

  11. Estimation of Alignment and Transverse Load in Multi-Bearing Rotor System

    OpenAIRE

    Tom J. Chalko; Dong-Xu Li

    1997-01-01

    The paper presents a method for estimation of a multi-bearing machine alignment on the basis of measured eccentricities of the shaft in machine bearings. The method uses a linear FEM model of the rotor and the non-linear models of machine bearings. In the presented example, the non-linear models of hydrodynamic bearings are used, but it is shown, that the method could be easily applied to other types of bearings. In addition to the alignment estimation, the method allows to estimate the unkno...

  12. Building on Sub-Arctic Soil: Geopolymerization of Muskeg to a Densified Load-Bearing Composite.

    Science.gov (United States)

    Waetzig, Gregory R; Cho, Junsang; Lacroix, Max; Banerjee, Sarbajit

    2017-11-07

    The marshy water-saturated soil typical of the sub-Arctic represents a considerable impediment to the construction of roads, thereby greatly hindering human habitation and geological excavation. Muskeg, the native water-laden topsoil characteristic of the North American sub-Arctic, represents a particularly vexing challenge for road construction. Muskeg must either be entirely excavated, or for direct construction on muskeg, a mix of partial excavation and gradual compaction with the strategic placement of filling materials must be performed. Here, we demonstrate a novel and entirely reversible geopolymerization method for reinforcing muskeg with wood fibers derived from native vegetation with the addition of inorganic silicate precursors and without the addition of extraneous metal precursors. A continuous siloxane network is formed that links together the muskeg, wood fibers, and added silicates yielding a load-bearing and low-subsidence composite. The geopolymerization approach developed here, based on catalyzed formation of a siloxane network with further incorporation of cellulose, allows for an increase of density as well as compressive strength while reducing the compressibility of the composite.

  13. On the biomechanical function of scaffolds for engineering load-bearing soft tissues.

    Science.gov (United States)

    Stella, John A; D'Amore, Antonio; Wagner, William R; Sacks, Michael S

    2010-07-01

    Replacement or regeneration of load-bearing soft tissues has long been the impetus for the development of bioactive materials. While maturing, current efforts continue to be confounded by our lack of understanding of the intricate multi-scale hierarchical arrangements and interactions typically found in native tissues. The current state of the art in biomaterial processing enables a degree of controllable microstructure that can be used for the development of model systems to deduce fundamental biological implications of matrix morphologies on cell function. Furthermore, the development of computational frameworks which allow for the simulation of experimentally derived observations represents a positive departure from what has mostly been an empirically driven field, enabling a deeper understanding of the highly complex biological mechanisms we wish to ultimately emulate. Ongoing research is actively pursuing new materials and processing methods to control material structure down to the micro-scale to sustain or improve cell viability, guide tissue growth, and provide mechanical integrity, all while exhibiting the capacity to degrade in a controlled manner. The purpose of this review is not to focus solely on material processing but to assess the ability of these techniques to produce mechanically sound tissue surrogates, highlight the unique structural characteristics produced in these materials, and discuss how this translates to distinct macroscopic biomechanical behaviors. Copyright 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  14. A compression and shear loading test of concrete filled steel bearing wall

    International Nuclear Information System (INIS)

    Akiyama, Hiroshi; Sekimoto, Hisashi; Fukihara, Masaaki; Nakanishi, Kazuo; Hara, Kiyoshi.

    1991-01-01

    Concrete-filled steel bearing walls called SC structure which are the composite structure of concrete and steel plates have larger load-carrying capacity and higher ductility as compared with conventional RC structures, and their construction method enables the rationalization of construction procedures at sites and the shortening of construction period. Accordingly, the SC structures have become to be applied to the inner concrete structures of PWR nuclear power plants, and subsequently, it is planned to apply them to the auxiliary buildings of nuclear power plants. The purpose of this study is to establish a rational design method for the SC structures which can be applied to the auxiliary buildings of nuclear power plants. In this study, the buckling strength of surface plates and the ultimate strength of the SC structure were evaluated with the results of the compression and shear tests which have been carried out. The outline of the study and the tests, the results of the compression test and the shear test and their evaluation are reported. Stud bolts were effective for preventing the buckling of surface plates. The occurrence of buckling can be predicted analytically. (K.I.)

  15. Retention Strength after Compressive Cyclic Loading of Five Luting Agents Used in Implant-Supported Prostheses

    Directory of Open Access Journals (Sweden)

    Angel Alvarez-Arenal

    2016-01-01

    Full Text Available The purpose of this study was to evaluate and compare the retention strength of five cement types commonly used in implant-retained fixed partial dentures, before and after compressive cyclic loading. In five solid abutments screwed to 5 implant analogs, 50 metal Cr-Ni alloy copings were cemented with five luting agents: resin-modified glass ionomer (RmGI, resin composite (RC, glass ionomer (GI, resin urethane-based (RUB, and compomer cement (CC. Two tensile tests were conducted with a universal testing machine, one after the first luting of the copings and the other after 100,000 cycles of 100 N loading at 0.72 Hz. The one way ANOVA test was applied for the statistical analysis using the post hoc Tukey test when required. Before and after applying the compressive load, RmGI and RC cement types showed the greatest retention strength. After compressive loading, RUB cement showed the highest percentage loss of retention (64.45%. GI cement recorded the lowest retention strength (50.35 N and the resin composite cement recorded the highest (352.02 N. The type of cement influences the retention loss. The clinician should give preference to lower retention strength cement (RUB, CC, and GI if he envisages any complications and a high retention strength one (RmGI, RC for a specific clinical situation.

  16. Immediate loading of tapered implants placed in postextraction sockets: retrospective analysis of the 5-year clinical outcome.

    Science.gov (United States)

    Mura, Priamo

    2012-08-01

    The use of immediate implant loading protocols delivers obvious benefits to the patient. When applied in healed sites, this has not only been well documented in the totally edentolous mandible but has also been documented and reported to be predictable in the upper jaw, and in cases of partial edentoulism, as well. A further application of immediate loading protocol, although still controversial, especially when replacing single maxillary teeth in the anterior zone, is the immediate implant placement and provisionalization in postextractive sockets. In consideration of the oxidized surface promoting bone healing and the tapered shape of the implant body, the Replace Select Tapered TiUnite implants have been used for many years in our clinic when facing these clinical situations. This article will report about our long-term clinical experience with such implants and the relevant role of a correct surgical and prosthetic treatment planning. The aim of this retrospective study was to report on the 5-year clinical and radiologic outcome of patients treated with Replace Select Tapered TiUnite implants when used according to an immediate loading protocol in postextraction sites. In routine practice, 56 consecutive patients were treated with 79 implants. The patients, 23 males and 33 females, had a mean age of 50.9 years, range 21-76 years, at implant placement. Forty-seven implants were placed in the maxilla and 32 implants were placed in the mandible. All implants were placed in postextraction sites and were immediately loaded. Provisional restorations were delivered within 2 hours from surgery and all were in occlusion. Forty-three patients received a single implant while in the remaining 13 patients the implants were splinted. Definitive prosthetic restoration was delivered within 1 to 4 months following implant placement. Evaluations of soft tissue health and marginal bone remodeling were conducted. An independent radiologist performed the radiographic evaluation

  17. Positive effects of cell-free porous PLGA implants and early loading exercise on hyaline cartilage regeneration in rabbits.

    Science.gov (United States)

    Chang, Nai-Jen; Lin, Chih-Chan; Shie, Ming-You; Yeh, Ming-Long; Li, Chien-Feng; Liang, Peir-In; Lee, Kuan-Wei; Shen, Pei-Hsun; Chu, Chih-Jou

    2015-12-01

    -thickness osteochondral regeneration in rabbit knee joint models. Promoting effective hyaline cartilage regeneration rather than fibrocartilage scar tissue remains clinically challenging. To address the obstacle, we fabricated a spongy cell-free PLGA scaffold, and designed a reasonable exercise program to generate combined therapeutic effects. First, the implanting scaffold generates an affordable mechanical structure to bear the loading forces and bridge with the host to offer a space in the full-thickness osteochondral regeneration in rabbit knee joint. After implantation, rabbits were performed by an early treadmill exercise 15 min/day, 5 days/week for 2 weeks that directly exerts in situ endogenous growth factor and anti-inflammatory effects in the reparative site. The advanced therapeutic strategy showed that neo-hyaline cartilage formation with enriched collagen type II, higher glycosaminoglycan, integrating subchondral bone formation and modest inflammation. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  18. Immediate functional loading of provisional implants in the reconstructed atrophic maxilla: preliminary results of a prospective study after 6 months of loading with a provisional bridge.

    Science.gov (United States)

    Lenssen, O; Barbier, L; De Clercq, C

    2011-09-01

    Implant-prosthetic rehabilitation of atrophic maxillae remains a challenging problem. The aim of this paper is to describe a novel treatment for functional rehabilitation of the atrophic maxilla and to discuss preliminary results of this treatment protocol. A prospective pilot study was carried out in 10 patients who underwent bony reconstruction of atrophic maxillae under general anaesthesia, with autologous calvarial bone grafts and simultaneous placement of six provisional implants. The provisional implants were loaded with a provisional acrylic bridge 1 day after surgery. After 6 months, the provisional implants were removed and final implants were placed under local anaesthesia, again in an immediate loading concept with a provisional bridge, followed by a final bridge after another 6 months of healing. The bone grafts integrated well in all 10 patients without infectious complications. The prosthetic survival of the provisional bridge at the time of placing the implants was 100%. All final implants could be placed and immediately loaded with a second provisional bridge. Patient satisfaction was high due to limited postoperative inconvenience and immediate fixed prosthetic rehabilitation. The preliminary results of this pilot study demonstrate that this treatment protocol is a well tolerated treatment for patients with maxillary atrophy desiring dental rehabilitation. Copyright © 2011 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

  19. Immediate occlusal loading of NanoTite PREVAIL implants: a prospective 1-year clinical and radiographic study.

    Science.gov (United States)

    Ostman, Pär-Olov; Wennerberg, Ann; Albrektsson, Tomas

    2010-03-01

    Recently, a new implant surface texture, featuring application of nanometer-scale calcium phosphate has been shown to enhance early bone fixation and formation in preclinical studies and in human histomorphometric studies, which may be beneficial in immediate loading situations. The purpose of the present prospective clinical study was to, during 1 year, clinically and radiographically evaluate a nanometer scale surface modified implant placed for immediate loading of fixed prostheses in both maxillary and mandibular regions. Thirty-five out of 38 patients who needed implant treatment and met inclusion criteria agreed to participate in the study and were consecutively enrolled. Surgical implant placement requirements consisted of a final torque of a least 25 Ncm prior to final seating and an implant stability quotient above 55. A total of 102 NanoTite PREVAIL (NTP) implants (BIOMET 3i, Palm Beach Gardens, FL, USA) (66 maxillary and 36 mandibular) were placed by one investigator, and the majority of these were placed in posterior regions (65%) and in soft bone (69%). A total of 44 prosthetic constructions were evaluated consisting of 14 single-tooth restorations, 26 fixed partial dentures, and four complete fixed restorations. All provisional constructions were delivered within 1 hour, and the final constructions placed after 4 months. Implants were monitored for clinical and radiographic outcomes at follow-up examinations scheduled for 3, 6, and 12 months. Of the 102 study implants, one implant failed. The simple cumulative survival rate value at 1 year was 99.2%. The average marginal bone resorption was 0.37 mm (SD 0.39) during the first year in function. According to the success criteria of Albrektsson and Zarb, success grade 1 was found with 93% of the implants. Although limited to the short follow-up, immediate loading of NanoTite Prevail implants seems to be a viable option in implant rehabilitation, at least when a good initial fixation is achieved.

  20. Near-infrared fluorescence imaging platform for quantifying in vivo nanoparticle diffusion from drug loaded implants.

    Science.gov (United States)

    Markovic, Stacey; Belz, Jodi; Kumar, Rajiv; Cormack, Robert A; Sridhar, Srinivas; Niedre, Mark

    2016-01-01

    Drug loaded implants are a new, versatile technology platform to deliver a localized payload of drugs for various disease models. One example is the implantable nanoplatform for chemo-radiation therapy where inert brachytherapy spacers are replaced by spacers doped with nanoparticles (NPs) loaded with chemotherapeutics and placed directly at the disease site for long-term localized drug delivery. However, it is difficult to directly validate and optimize the diffusion of these doped NPs in in vivo systems. To better study this drug release and diffusion, we developed a custom macroscopic fluorescence imaging system to visualize and quantify fluorescent NP diffusion from spacers in vivo. To validate the platform, we studied the release of free fluorophores, and 30 nm and 200 nm NPs conjugated with the same fluorophores as a model drug, in agar gel phantoms in vitro and in mice in vivo. Our data verified that the diffusion volume was NP size-dependent in all cases. Our near-infrared imaging system provides a method by which NP diffusion from implantable nanoplatform for chemo-radiation therapy spacers can be systematically optimized (eg, particle size or charge) thereby improving treatment efficacy of the platform.

  1. The effect of number and distribution of unsplinted maxillary implants on the load transfer in implant-retained maxillary overdentures: an in vitro study.

    Science.gov (United States)

    Damghani, Sahar; Masri, Radi; Driscoll, Carl F; Romberg, Elaine

    2012-06-01

    There is little information as to how the number and distribution of implants affect the amount of load transmitted to the palate in implant-retained maxillary overdentures. The purpose of this study was to evaluate the effect of the number and distribution of dental implants on the load transmitted to the palate. Eight implant analogues were placed in a replica of an average sized edentulous maxilla corresponding to the position of canines, first and second premolars, and first molars. The anteroposterior distance between the centers of implants in each quadrant was 8 mm. Fifteen denture bases were fabricated to fit the edentulous maxilla analogue. The denture bases were attached to the oral analogue using 6 different configurations of attachments (6 groups): Either no Locator attachments were used (control group), or the 2 most anterior attachments were attached, or 4 implants were engaged with a distance of 8, 16, or 24 mm between the centers of implants on left and right side, and finally, when all 8 attachments were activated. A force-measuring sensor was used to measure the force transmitted to the palate when a static force of 245 N was applied on the occlusal rims of the denture bases. Data (Newtons) were analyzed using 1-way ANOVA and Tukey's HSD test α=.05). The mean (SD) amount of force measured on the palate when the overdentures were supported by 4 Locator attachments; [49.84 (26.52) at 8 mm spacing], [24.42 (15.05) at 16 mm spacing], [35.66 (22.94) at 24 mm spacing] was significantly lower than when no attachments [90.98 (20.20), control], or when 2 Locator attachments were used [76.07 (27.63)] (Poverdentures were supported by 8 Locator attachments, the force measured on the palate [20.67(16.06) N] was significantly lower than that for the control group (Poverdentures supported by 2 Locator attachments (Poverdentures supported by 4 Locator attachments when the distance between the anterior and posterior implants was 8 mm P=.006). The distribution of

  2. Bone Reduction to Facilitate Immediate Implant Placement and Loading Using CAD/CAM Surgical Guides for Patients With Terminal Dentition.

    Science.gov (United States)

    Alzoubi, Fawaz; Massoomi, Nima; Nattestad, Anders

    2016-10-01

    The aim of this study is to present a method, using 3 computer-aided design/computer-aided manufacturing (CAD/CAM) surgical guides, to accurately obtain the desired bone reduction followed by immediate implant placements and loading for patients diagnosed with terminal dentition. Patients who had bone reduction, implants placed, and immediate loading using Anatomage Invivo 5 CAD/CAM surgical guides between the period 2013 and 2015 were evaluated retrospectively. Patients diagnosed with terminal dentition and treated using the "3-guide technique" were identified. Pre- and postsurgical images were superimposed to evaluate deviations of the bone reduction and deviations at the crest, apex, and angle of implants placed. Twenty-six implants placed in 5 patients were included in this study. The overall deviation means measured for bone reduction was 1.98 mm. The overall deviation means measured for implant placement at the crest, apex, and angle were 1.43 mm, 1.90 mm, and 4.14°, respectively. The CAD/CAM surgical guide fabrication is an emerging tool that may facilitate the surgical process and aid in safe and predictable execution of bone reduction and immediate implant placement. Using 3 CAD/CAM surgical guides, a method is presented to obtain the desired bone reduction followed by immediate implant placement and loading for patients diagnosed with terminal dentition. This method may improve guide stability for patients with terminal dentition undergoing complete implant-supported treatment by taking advantage of the teeth to be extracted.

  3. Bone reactions adjacent to titanium implants subjected to static load of different duration. A study in the dog (III)

    DEFF Research Database (Denmark)

    Gotfredsen, K; Berglundh, T; Lindhe, J

    2001-01-01

    The aim of the present experiment was to study the effect of a long-standing lateral static load on the peri-implant bone. Three beagle dogs were used. The mandibular premolars were extracted and 12 weeks later 3 titanium implants (ITI(R) Dental Implant System) were installed in each quadrant....... Crowns were fitted to all implants 12 weeks after the installation procedure. The anterior and central crowns were fused and connected to the posterior crown by an expansion screw. In the right side of the mandible, the expansion screws were activated every 2 weeks during a 46-week period. During...... the last 10 weeks of this period, an expansion force similar to that of the right side was applied in the left. The animals were sacrificed and block biopsies of each implant site harvested and prepared for histological analysis. Sites subjected to 10 weeks or 46 weeks of lateral load had a similar (i...

  4. A radiographic evaluation of progressive loading on crestal and bone density changes around single osseointegrated implants in the posterior maxilla

    Directory of Open Access Journals (Sweden)

    Ommati Shabestari Gh.

    2009-11-01

    Full Text Available "nBackground and Aim: The aim of this clinical study was to determine the effectiveness of progressive loading procedures on preserving crestal bone height and improving peri-implant bone density around maxillary implants restored with single crowns by an accurate longitudinal radiographic assessment technique. "n "n "nMaterials and Methods: Eleven Micro-Thread Osseo Speed dental implants were placed in 11 subjects and permitted to heal for 6 weeks before surgical uncovering. Following an 8-week healing period, implants underwent a progressive loading protocol by increasing the height of the occlusal table in increments from adding acrylic resin to an acrylic crown. The progressively loaded crowns were placed in 2 mm infraocclusion for the first 2 months, light occlusion for the second 2 months, and full occlusion for the third 2 months. At forth 2 months, a metal ceramic crown replaced the acrylic crown. Digital radiographs of each implant were made at the time of restoration, then after 2, 4, 6, 8, and 12 months of function. Digital image analysis was done to measure changes in crestal bone height and peri-implant bone density. "n "n "nResults: The mean values of crestal bone loss at 12 months were 0.11 ± 0.19 mm, and when tested with Friedman across the time periods, the differences were not statistically significant (p> 0.05. The mean values of bone density in the crestal, middle, and apical area were tested with Repeated Measure ANOVA across the time periods, the differences were statistically significant (p<0.05. "n "n "nConclusion: Progressive loading doesn’t cause crestal bone loss. The peri-implant density measurements of the progressively loaded implants show continuous increase in crestal, middle and apical peri-implant bone density by time. "n 

  5. Load-bearing masonry system adoption and performance: A case study of construction company in a developing country

    Science.gov (United States)

    Ramli, Nor Azlinda; Abdullah, Che Sobry; Nawi, Mohd Nasrun Mohd; Bahaudin, Ahmad Yusni

    2016-08-01

    This study addresses the factors that influence the adoption of load-bearing masonry (LBM) system. A case study of the load-bearing masonry (LBM) system adoption is conducted through an interview to explore the situation of the technology adoption in a construction company. The finding indicates the factors influence the adoption of LBM system for the construction company are: organizational resources, usefulness, less maintenance, reduce construction time and cost. From the findings, these factors consistent with previous literature. Furthermore, the performance of the company was measured by looking into the financial and non-financial aspects. The LBM system brings good performance as it increased the profits of the company, a good quality of product and attracts more demand from customers. Thus, these factors should be considered for the other companies that are interested in implementing the LBM system in their projects.

  6. Experimental investigations of the frictional and wear behavior of tungsten carbide cermet ball bearings under axial load in liquid sodium

    International Nuclear Information System (INIS)

    Kleefeldt, K.W.

    1976-01-01

    The paper describes part of the R and D work performed on ball bearings operated in a liquid sodium environment and tested under conditions which are felt to be representative for high precision mechanisms in LMFBR's. After a short introduction, mainly dealing with the experimental results of other authors, a description will be given of the test facility, the test procedure, the ball bearings and the basis for the selection of the materials. The paper covers the experimental phase, which has been carried out in two steps. In the first phase material screening tests demonstrated the tungsten-carbide-cobalt cermet to be superior to the other materials tested with respect to friction and wear. This material, therefore, was selected for a more detailed parameter test programme during phase 2. Up to now a series of tests have been performed with bearing load and speed as parameters, indicating that fatigue is the life limiting factor. It shows that a life-load relationship, similar to that known for conventional ball bearing technology, also seems appropriate for the test conditions and environment investigated here

  7. Repair of Segmental Load-Bearing Bone Defect by Autologous Mesenchymal Stem Cells and Plasma-Derived Fibrin Impregnated Ceramic Block Results in Early Recovery of Limb Function

    Directory of Open Access Journals (Sweden)

    Min Hwei Ng

    2014-01-01

    Full Text Available Calcium phosphate-based bone substitutes have not been used to repair load-bearing bone defects due to their weak mechanical property. In this study, we reevaluated the functional outcomes of combining ceramic block with osteogenic-induced mesenchymal stem cells and platelet-rich plasma (TEB to repair critical-sized segmental tibial defect. Comparisons were made with fresh marrow-impregnated ceramic block (MIC and partially demineralized allogeneic bone block (ALLO. Six New Zealand White female rabbits were used in each study group and three rabbits with no implants were used as negative controls. By Day 90, 4/6 rabbits in TEB group and 2/6 in ALLO and MIC groups resumed normal gait pattern. Union was achieved significantly faster in TEB group with a radiological score of 4.50 ± 0.78 versus ALLO (1.06 ± 0.32, MIC (1.28 ± 0.24, and negative controls (0. Histologically, TEB group scored the highest percentage of new bone (82% ± 5.1% compared to ALLO (5% ± 2.5% and MIC (26% ± 5.2%. Biomechanically, TEB-treated tibiae achieved the highest compressive strength (43.50 ± 12.72 MPa compared to those treated with ALLO (15.15 ± 3.57 MPa and MIC (23.28 ± 6.14 MPa. In conclusion, TEB can repair critical-sized segmental load-bearing bone defects and restore limb function.

  8. Fracture mode during cyclic loading of implant-supported single-tooth restorations

    DEFF Research Database (Denmark)

    Hosseini, Mandana; Kleven, Erik; Gotfredsen, Klaus

    2012-01-01

    restorations of zirconia abutment-retained crowns with zirconia copings veneered with glass-ceramics (n=8) and feldspathic ceramics (n=8). The control group was composed of 16 metal ceramic restorations of titanium abutment-retained crowns with gold alloy copings veneered with glass (n=8) and feldspathic...... ceramics (n=8). The palatal surfaces of the crowns were exposed to cyclic loading of 800 N with a frequency of 2 Hz, which continued to 4.2 million cycles or until fracture of the copings, abutments, or implants. The number of cycles and the fracture modes were recorded. The fracture modes were analyzed...

  9. Misfit of Three Different Implant-Abutment Connections Before and After Cyclic Load Application: An In Vitro Study.

    Science.gov (United States)

    Gehrke, Sergio Alexandre; Delgado-Ruiz, Rafael Arcesio; Prados Frutos, Juan Carlos; Prados-Privado, María; Dedavid, Berenice Anina; Granero Marín, Jose Manuel; Calvo Guirado, José Luiz

    This study aimed to evaluate the misfit of three different implant-abutment connections before and after cycling load. One hundred twenty dental implants and correspondent prefabricated titanium abutments were used. Three different implant-abutment connections were evaluated: Morse taper (MT group), external hexagon (EH group), and internal hexagon (IH group). Forty implants and 40 abutments were used per group. The parameters for the mechanical evaluation were set as: 360,000 cycles, load of 150 N, and frequency of 4 Hz. Samples were sectioned in their longitudinal and transversal axes, and the misfit of the implant-abutment connection was evaluated by scanning electron microscopy analysis. One-way analyses of variance, Tukey post hoc analyses (α = .05), and t test (P .05). Transversally, only the MT group showed full fitting after cycling load compared with the other groups (EH and IH) (P abutment connection in internal, external, and Morse taper connections. In the longitudinal direction, the accommodation decreases and/or eliminates the gap observed initially (before load). In the horizontal direction, Morse cone implant-abutment connections experience a complete accommodation with the elimination of the gap.

  10. Immediate occlusal loading of implants in the partially edentate mandible: a prospective 1-year radiographic and 4-year clinical study.

    Science.gov (United States)

    Ostman, Pär-Olov; Hellman, Mats; Sennerby, Lars

    2008-01-01

    The purpose of the present prospective clinical study was to evaluate the radiographic and clinical outcome of immediately loaded implants in the partial edentulous mandible over a 4-year follow-up period using a modified surgical protocol, primary implant stability criteria, and splinting for inclusion. Patients in need of implant treatment in the partial edentate mandible were consecutively included in the study. The implant sites were underprepared to obtain maximal stability. Inclusion criteria for the study were torque of a least 30 Ncm before final seating of the implant and an ISQ greater than 60. A provisional fixed partial denture was delivered within 24 hours and a definitive fixed partial denture within 3 months. The patients were monitored with clinical and radiographic follow-up examinations for up to 4 years. Stability of the implants was measured with resonance frequency analysis at placement and after 6 months. Ninety-six patients were evaluated, and 77 patients who met the inclusion criteria were included. A total of 111 fixed partial dentures supported by 257 Brånemark System implants (77 turned and 180 TiUnite implants) were delivered. Four (1.6%) of the 257 implants did not osseointegrate, giving an overall survival rate of 98.4% after 4 years. Three turned (3.9%) implants and 1 oxidized implant (0.6%) failed after 4 to 13 months. The average marginal bone resorption was 0.7 mm (SD 0.78) during the first year in function. Turned implants showed an average bone loss of 0.5 mm (SD 0.8) and oxidized implants an average of 0.7 mm (SD 0.8). Resonance frequency analysis showed a mean implant stability quotient of 72.2 (SD 7.5) at placement and 72.5 (SD 5.7) after 6 months of loading. It is concluded that immediate loading of implants with firm primary stability in partially edentulous areas of the mandible appears to be a viable procedure with predictable outcome.

  11. Immediate versus early loading of two implants placed with a flapless technique supporting mandibular bar-retained overdentures: a single-blinded, randomised controlled clinical trial.

    Science.gov (United States)

    Cannizzaro, Gioacchino; Leone, Michele; Esposito, Marco

    2008-01-01

    To evaluate the efficacy of immediate loading versus early loading at 6 weeks of bar-retained mandibular overdentures supported by two implants placed with a flapless technique. Sixty patients were randomised: 30 to the immediately loaded group and 30 to the early loaded group. To be immediately loaded, implants had to be inserted with a minimum torque > 48 Ncm. Outcome measures were prosthesis and implant failures, biological and biomechanical complications, patient satisfaction, and Implant Stability Quotient (ISQ) assessed with a resonance frequency analysis instrument. Sixty implants were placed in each group. Flaps had to be raised in nine patients to check drill direction or to better visualise the area after multiple teeth extraction. Two implants in two patients did not reach the planned insertion torque and were immediately replaced by larger diameters ones. After 1 year no drop out occurred and two early loaded implants failed in two patients. There were no statistically significant differences between groups for prosthesis failures, implant losses, complications, and mean ISQ values; however, patients in the immediately loaded group were significantly more satisfied than those loaded early. When comparing mean ISQ values taken 6 weeks after placement with 1-year data within each group, values decreased significantly. Mandibular overdentures can be successfully loaded the same day of implant placement with a minimally invasive surgery, increasing patient satisfaction while decreasing treatment time and patient discomfort. No apparent advantages were seen when loading the overdentures at 6 weeks.

  12. Magnesium alloys as body implants: fracture mechanism under dynamic and static loadings in a physiological environment.

    Science.gov (United States)

    Choudhary, Lokesh; Raman, R K Singh

    2012-02-01

    It is essential that a metallic implant material possesses adequate resistance to cracking/fracture under the synergistic action of a corrosive physiological environment and mechanical loading (i.e. stress corrosion cracking (SCC)), before the implant can be put to actual use. This paper presents a critique of the fundamental issues with an assessment of SCC of a rapidly corroding material such as magnesium alloys, and describes an investigation into the mechanism of SCC of a magnesium alloy in a physiological environment. The SCC susceptibility of the alloy in a simulated human body fluid was established by slow strain rate tensile (SSRT) testing using smooth specimens under different electrochemical conditions for understanding the mechanism of SCC. However, to assess the life of the implant devices that often possess fine micro-cracks, SCC susceptibility of notched specimens was investigated by circumferential notch tensile (CNT) testing. CNT tests also produced important design data, i.e. threshold stress intensity for SCC (KISCC) and SCC crack growth rate. Fractographic features of SCC were examined using scanning electron microscopy. The SSRT and CNT results, together with fractographic evidence, confirmed the SCC susceptibility of both smooth and notched specimens of a magnesium alloy in the physiological environment. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  13. Single dental implant retained mandibular complete dentures – influence of the loading protocol: study protocol for a randomized controlled trial

    Science.gov (United States)

    2014-01-01

    Background Over the years, there has been a strong consensus in dentistry that at least two implants are required to retain a complete mandibular denture. It has been shown in several clinical trials that one single median implant can retain a mandibular overdenture sufficiently well for up to 5 years without implant failures, when delayed loading was used. However, other trials have reported conflicting results with in part considerable failure rates when immediate loading was applied. Therefore it is the purpose of the current randomized clinical trial to test the hypothesis that immediate loading of a single mandibular midline implant with an overdenture will result in a comparable clinical outcome as using the standard protocol of delayed loading. Methods/design This prospective nine-center randomized controlled clinical trial is still ongoing. The final patient will complete the trial in 2016. In total, 180 edentulous patients between 60 and 89 years with sufficient complete dentures will receive one median implant in the edentulous mandible, which will retain the existing complete denture using a ball attachment. Loading of the median implant is either immediately after implant placement (experimental group) or delayed by 3 months of submerged healing at second-stage surgery (control group). Follow-up of patients will be performed for 24 months after implant loading. The primary outcome measure is non-inferiority of implant success rate of the experimental group compared to the control group. The secondary outcome measures encompass clinical, technical and subjective variables. The study was funded by the Deutsche Forschungsgemeinschaft (German research foundation, KE 477/8-1). Discussion This multi-center clinical trial will give information on the ability of a single median implant to retain a complete mandibular denture when immediately loaded. If viable, this treatment option will strongly improve everyday dental practice. Trial registration The trial

  14. A novel flexible capacitive load sensor for use in a mobile unicompartmental knee replacement bearing: An in vitro proof of concept study.

    Science.gov (United States)

    Mentink, M J A; Van Duren, B H; Murray, D W; Gill, H S

    2017-08-01

    Instrumented knee replacements can provide in vivo data quantifying physiological loads acting on the knee. To date instrumented mobile unicompartmental knee replacements (UKR) have not been realised. Ideally instrumentation would be embedded within the polyethylene bearing. This study investigated the feasibility of an embedded flexible capacitive load sensor. A novel flexible capacitive load sensor was developed which could be incorporated into standard manufacturing of compression moulded polyethylene bearings. Dynamic experiments were performed to determine the characteristics of the sensor on a uniaxial servo-hydraulic material testing machine. The instrumented bearing was measured at sinusoidal frequencies between 0.1 and 10Hz, allowing for measurement of typical gait load magnitudes and frequencies. These correspond to frequencies of interest in physiological loading. The loads that were applied were a static load of 390N, corresponding to an equivalent body weight load for UKR, and a dynamic load of ±293N. The frequency transfer response of the sensor suggests a low pass filter response with a -3dB frequency of 10Hz. The proposed embedded capacitive load sensor was shown to be applicable for measuring in vivo loads within a polyethylene mobile UKR bearing. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

  15. Immediate occlusal loading of NanoTite™ tapered implants: a prospective 1-year clinical and radiographic study.

    Science.gov (United States)

    Östman, Pär-Olov; Wennerberg, Ann; Ekestubbe, Annika; Albrektsson, Tomas

    2013-12-01

    During the last decade, high success rates have been reported for implants placed with immediate loading procedures, especially when bone quality and quantity provide good implant stability. In many of these studies, straight-walled implants with moderately rough surfaces were employed. Tapered implants are becoming increasingly more popular due to standardized drilling protocols and reports of high initial primary stability. The aim of the present prospective, single center clinical study was to evaluate surface topographical analysis and the clinical and radiographic outcomes of the NanoTite™ (BIOMET 3i, Palm Beach Gardens, FL, USA) Tapered Implant when used for immediate loading of fixed prostheses and single-tooth restorations. Forty-two patients who needed implant treatment and met admission criteria agreed to participate in the study and were consecutively enrolled. Surgical implant placement requirements consisted of a final torque of a least 30 Ncm prior to final seating and an implant stability quotient above 55. A total of 139 NanoTite Tapered implants (112 maxillary and 27 mandibular) were placed by one investigator, and the majority of these implants (n = 77/55%) were placed in posterior regions, and in soft bone (n = 90/65%). A total of 57 prosthetic constructions were evaluated consisting of 20 single-tooth restorations, 30 fixed partial dentures, and 7 complete, fixed maxillary restorations. Radiographs were taken at baseline and at 12 months of follow-up. Of the 139 study implants, one implant failure was declared. The overall cumulative survival rate at 1 year is 99.4%. Mean marginal bone resorption is 1.01 mm (SD 0.85) during the first year of function. Although limited to the short follow-up, immediate loading of NanoTite Tapered implants seems to be a viable option in implant rehabilitation, when insertion torque of at least 30 Ncm is achieved. Further studies are needed to authenticate the finding of this study. © 2012 Wiley

  16. The Load-Bearing Capacity of Timber-Glass Composite I-Beams Made with Polyurethane Adhesives

    Science.gov (United States)

    Rodacki, Konrad

    2017-12-01

    This article discusses the issue of composite timber-glass I-beams, which are an interesting alternative for load-bearing beams of ceilings and roofs. The reasoning behind the use of timber-glass I-beams is the combination of the best features of both materials - this enables the creation of particularly safe beams with regard to structural stability and post-breakage load capacity. Due to the significant differences between the bonding surfaces of timber and glass, a study on the adhesion of various adhesives to both surfaces is presented at the beginning of the paper. After examination, two adhesives were selected for offering the best performance when used with composite beams. The beams were investigated using a four-point bending test under quasi-static loading.

  17. Effect of controlled early implant loading on bone healing and bone mass in guinea pigs, as assessed by micro-CT and histology.

    NARCIS (Netherlands)

    Smet, E. De; Jaecques, S.V.; Wevers, M.; Jansen, J.A.; Jacobs, R.; Sloten, J. van der; Naert, I.E.

    2006-01-01

    Without controlled loading, the failure of early loaded oral implants is higher than in delayed loading, unless loading regimens can be identified that stimulate bone formation. The purpose of this study was to investigate whether controlled early loading optimizes osseointegration. Six series of

  18. Throughput of oil and demand for oil of non-stationary loaded sliding bearings in internal combustion engines. Oeldurchsatz und Oelbedarf instationaer belasteter Gleitlager am Verbrennungsmotor

    Energy Technology Data Exchange (ETDEWEB)

    Esch, H.J.

    1981-12-17

    The throughput of oil and the demand for oil of the non-stationary loaded sliding bearings was determined in a high speed petrol engine. The crankshaft bearing and connecting rod bearing were examined. The bearing temperature of the connecting rod bearing was measured by thermocouples built into this bearing; transmission of the signal from the rotating to the fixed part of the system was by means of a rotating transmitter. The temperature measurement in the crankshaft bearing was done by thermocouples in the bearing shell. Using a separate oil supply for the test bearing, the demand for oil was determined by reducing the oil pressure. Comparative oil throughput calculations were carried out to clear up the relationships discovered in the equipment. The results of the investigation are collected in 15 points, which are explained in detail. These include: negligible effect on the oil throughput of the ignition timing, air ratio and coolant temperature at constant speed and constant mean pressure, the considerable rise of the oil throughput through the connecting rod and crankshaft bearing with increasing speed, and the dominating effect of play in the bearing on the maximum bearing temperature.

  19. Life prediction of different commercial dental implants as influence by uncertainties in their fatigue material properties and loading conditions.

    Science.gov (United States)

    Pérez, M A

    2012-12-01

    Probabilistic analyses allow the effect of uncertainty in system parameters to be determined. In the literature, many researchers have investigated static loading effects on dental implants. However, the intrinsic variability and uncertainty of most of the main problem parameters are not accounted for. The objective of this research was to apply a probabilistic computational approach to predict the fatigue life of three different commercial dental implants considering the variability and uncertainty in their fatigue material properties and loading conditions. For one of the commercial dental implants, the influence of its diameter in the fatigue life performance was also studied. This stochastic technique was based on the combination of a probabilistic finite element method (PFEM) and a cumulative damage approach known as B-model. After 6 million of loading cycles, local failure probabilities of 0.3, 0.4 and 0.91 were predicted for the Lifecore, Avinent and GMI implants, respectively (diameter of 3.75mm). The influence of the diameter for the GMI implant was studied and the results predicted a local failure probability of 0.91 and 0.1 for the 3.75mm and 5mm, respectively. In all cases the highest failure probability was located at the upper screw-threads. Therefore, the probabilistic methodology proposed herein may be a useful tool for performing a qualitative comparison between different commercial dental implants. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  20. Osseointegration of layer-by-layer polyelectrolyte multilayers loaded with IGF1 and coated on titanium implant under osteoporotic condition

    Directory of Open Access Journals (Sweden)

    Xing H

    2017-10-01

    Full Text Available Helin Xing,1,* Xing Wang,2,* Saisong Xiao,3,* Guilan Zhang,1 Meng Li,1 Peihuan Wang,1 Quan Shi,1 Pengyan Qiao,1 Lingling E,1 Hongchen Liu1 1Institute of Stomatology, Chinese PLA General Hospital, Beijing, 2Hospital of Stomatology, Shanxi Medical University, Taiyuan, 3Department of Anesthesia, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China *These authors contributed equally to this work Purpose: Titanium implant is a widely used method for dental prosthesis restoration. Nevertheless, in patients with systemic diseases, including osteoporosis, diabetes, and cancer, the success rate of the implant is greatly reduced. This study investigates a new implant material loaded with insulin-like growth factor 1 (IGF1, which could potentially improve the implant success rate, accelerate the occurrence of osseointegration, and provide a new strategy for implant treatment in osteoporotic patients. Materials and methods: Biofunctionalized polyelectrolyte multilayers (PEMs with polyethylenimine as the excitation layer and gelatin/chitosan loaded with IGF1 were prepared on the surface of titanium implant by layer-by-layer self-assembly technique. The physical and chemical properties of the biofunctionalized PEMs, the biological characteristics of bone marrow mesenchymal stem cells (BMMSCs, and bone implant contact correlation test indexes were detected and analyzed in vitro and in vivo using osteoporosis rat model. Results: PEMs coatings loaded with IGF1 (TNS-PEM-IGF1-100 implant promoted the early stage of BMMSCs adhesion. Under the action of body fluids, the active coating showed sustained release of growth factors, which in turn promoted the proliferation and differentiation of BMMSCs and the extracellular matrix. At 8 weeks from implant surgery, the new bone around the implants was examined using micro-CT and acid fuchsin/methylene blue staining. The new bone formation increased with time in each group, while the TNS-PEM-IGF1

  1. Continuously Growing Ultrathick CrN Coating to Achieve High Load-Bearing Capacity and Good Tribological Property.

    Science.gov (United States)

    Li, Zechao; Wang, Yongxin; Cheng, Xiaoying; Zeng, Zhixiang; Li, Jinlong; Lu, Xia; Wang, Liping; Xue, Qunji

    2018-01-24

    Continuous growth of traditional monolayer CrN coatings up to 24 h is successfully achieved to fabricate ultrathickness of up to 80 μm on the 316 stainless steel substrate using a multiarc ion plating technique. The microstructures, mechanical properties, and tribological properties evolution with the CrN coating continuously growing was evaluated in detail. The transmission electron microscopy observations and inverse Fourier-filtered images reveal a relaxation mechanism during the continuous growth of CrN coating, which can lead to a decrease in the residual stress when coating growth time exceeds 5 h. The scratch test and friction test results both show that the load-bearing capacity of coating is significantly increased as CrN coatings growing thicker. During the scratch test, the ultrathick CrN coating of thickness 80.6 μm is not failed under the load of 180 N, and the dominant failure mechanism is the cohesive failure including wedge spallation and cracking. The dry-sliding friction test results show the mean coefficient of friction and the wear rate of ultrathick CrN are respectively decreased by 17.2 and 56.8% at most compared with the thin coating (thickness is 5.4 μm). The ultrahigh load-bearing capacity and excellent tribological property are attributed to the relaxation mechanism and limited contact pressure as the coating grows continuously.

  2. Loading Variables on Implant-Supported Distal-Extension Removable Partial Dentures: An In Vitro Pilot Study.

    Science.gov (United States)

    Hirata, Kiyotaka; Takahashi, Toshihito; Tomita, Akiko; Gonda, Tomoya; Maeda, Yoshinobu

    2016-01-01

    The aim of this study was to investigate strain on implants used for adjunctive support of distal extension removable partial dentures. An implant with strain gauges was used for testing purposes in two positions, parallel and inclined. Three loading scenarios--loading apparatus (LA), artificial teeth via cotton roll (CR), and artificial teeth (UT)--were studied and strains compared via the Kruskal-Wallis test (P=.05). Strain under CR was significantly larger than UT in parallel (P<.05). However, the opposite was observed in inclined. Strain in parallel was smallest for UT, whereas in inclined it was largest for CR.

  3. Mystery of Foil Air Bearings for Oil-free Turbomachinery Unlocked: Load Capacity Rule-of-thumb Allows Simple Estimation of Performance

    Science.gov (United States)

    DellaCorte, Christopher; Valco, Mark J.

    2002-01-01

    The Oil-Free Turbomachinery team at the NASA Glenn Research Center has unlocked one of the mysteries surrounding foil air bearing performance. Foil air bearings are self-acting hydrodynamic bearings that use ambient air, or any fluid, as their lubricant. In operation, the motion of the shaft's surface drags fluid into the bearing by viscous action, creating a pressurized lubricant film. This lubricating film separates the stationary foil bearing surface from the moving shaft and supports load. Foil bearings have been around for decades and are widely employed in the air cycle machines used for cabin pressurization and cooling aboard commercial jetliners. The Oil-Free Turbomachinery team is fostering the maturation of this technology for integration into advanced Oil-Free aircraft engines. Elimination of the engine oil system can significantly reduce weight and cost and could enable revolutionary new engine designs. Foil bearings, however, have complex elastic support structures (spring packs) that make the prediction of bearing performance, such as load capacity, difficult if not impossible. Researchers at Glenn recently found a link between foil bearing design and load capacity performance. The results have led to a simple rule-of-thumb that relates a bearing's size, speed, and design to its load capacity. Early simple designs (Generation I) had simple elastic (spring) support elements, and performance was limited. More advanced bearings (Generation III) with elastic supports, in which the stiffness is varied locally to optimize gas film pressures, exhibit load capacities that are more than double those of the best previous designs. This is shown graphically in the figure. These more advanced bearings have enabled industry to introduce commercial Oil-Free gas-turbine-based electrical generators and are allowing the aeropropulsion industry to incorporate the technology into aircraft engines. The rule-of-thumb enables engine and bearing designers to easily size and

  4. Effect of abutment screw length and cyclic loading on removal torque in external and internal hex implants.

    Science.gov (United States)

    Mohammed, Hnd Hadi; Lee, Jin-Han; Bae, Ji-Myung; Cho, Hye-Won

    2016-02-01

    The purpose of this study was to evaluate the effects of abutment screw length and cyclic loading on the removal torque (RTV) in external hex (EH) and internal hex (IH) implants. Forty screw-retained single crowns were connected to external and internal hex implants. The prepared titanium abutment screws were classified into 8 groups based on the number of threads (n = 5 per group): EH 12.5, 6.5, 3.5, 2.5 and IH 6.5, 5, 3.5, 2.5 threads. The abutment screws were tightened with 20 Ncm torque twice with 10-minute intervals. After 5 minutes, the initial RTVs of the abutment screws were measured with a digital torque gauge (MGT12). A customized jig was constructed to apply a load along the implant long axis at the central fossa of the maxillary first molar. The post-loading RTVs were measured after 16,000 cycles of mechanical loading with 50 N at a 1-Hz frequency. Statistical analysis included one-way analysis of variance and paired t-tests. The post-loading RTVs were significantly lower than the initial RTVs in the EH 2.5 thread and IH 2.5 thread groups (P<.05). The initial RTVs exhibited no significant differences among the 8 groups, whereas the post-loading RTVs of the EH 6.5 and EH 3.5 thread groups were higher than those of the IH 3.5 thread group (P<.05). Within the limitations of this study, the external hex implants with short screw lengths were more advantageous than internal hex implants with short screw lengths in torque maintenance after cyclic loading.

  5. Characterization of the bone-metal implant interface by Digital Volume Correlation of in-situ loading using neutron tomography.

    Science.gov (United States)

    Le Cann, Sophie; Tudisco, Erika; Perdikouri, Christina; Belfrage, Ola; Kaestner, Anders; Hall, Stephen; Tägil, Magnus; Isaksson, Hanna

    2017-11-01

    Metallic implants are commonly used as surgical treatments for many orthopedic conditions. The long-term stability of implants relies on an adequate integration with the surrounding bone. Unsuccessful integration could lead to implant loosening. By combining mechanical loading with high-resolution 3D imaging methods, followed by image analysis such as Digital Volume Correlation (DVC), we aim at evaluating ex vivo the mechanical resistance of newly formed bone at the interface. X-rays tomography is commonly used to image bone but induces artefacts close to metallic components. Utilizing a different interaction with matter, neutron tomography is a promising alternative but has not yet been used in studies of bone mechanics. This work demonstrates that neutron tomography during in situ loading is a feasible tool to characterize the mechanical response of bone-implant interfaces, especially when combined with DVC. Experiments were performed where metal screws were implanted in rat tibiae during 4 weeks. The screws were pulled-out while the samples were sequentially imaged in situ with neutron tomography. The images were analyzed to quantify bone ingrowth around the implants. DVC was used to track the internal displacements and calculate the strain fields in the bone during loading. The neutron images were free of metal-related artefacts, which enabled accurate quantification of bone ingrowth on the screw (ranging from 60% to 71%). DVC allowed successful identification of the deformation and cracks that occurred during mechanical loading and led to final failure of the bone-implant interface. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Investigation of journal orbit and flow pattern in a dynamically loaded journal bearing

    DEFF Research Database (Denmark)

    Christiansen, Christian Kim; Walther, Jens Honore; Klit, Peder

    2017-01-01

    A hydrodynamic journal bearing has been investigated using both the traditional two-dimensional (2D) Reynolds equation, and the full solution being the three-dimensional (3D) Navier-Stokes equations. The two approaches are compared by performing an investigation of two inlet groove designs: the a...

  7. Bearing Stress at Failure of Double-Lap Hybrid Joints in Woven Fabric Kenaf Fiber Composite Plates under Quasi-static Loading

    Directory of Open Access Journals (Sweden)

    Lee Sim Yee

    2017-01-01

    Full Text Available The present paper is focused on the bearing stress at failure of double-lap woven fabric kenaf fiber reinforced polymer (KFRP hybrid bonded-bolted joints in experimental frameworks. The effects of different normalized plate width (plate width/hole diameter, W/d, lay-up types and bolt loads were incorporated in current study as specified in testing series. Generally, hybrid joint coupons separated within adhesive layer prior to net-tension failure or bearing/net-tension failure. The bearing stress at failure increased as W/d ratio increment, critical W/d is given as four and three in clamped and finger tight condition respectively. Lay-up types present insignificant effect to bearing stress at failure due to low volume fiber fraction in kenaf fiber composites. Combination of thicker and clamped conditions plate demonstrated greater bearing stress than equivalent finger-tight (FT conditions due to higher load transferred from friction, as expected.

  8. Long-Term Survival of Dental Implants with Different Prosthetic Loading Times in Healthy Patients: A 5-Year Retrospective Clinical Study.

    Science.gov (United States)

    Muelas-Jiménez, M Isabel; Olmedo-Gaya, Maria Victoria; Manzano-Moreno, Francisco J; Reyes-Botella, Candela; Vallecillo-Capilla, Manuel

    2017-02-01

    To compare survival rates among dental implants restored with immediate, early, and conventional loading protocols, also comparing between maxillary and mandibular implants, and to evaluate the influence of implant length and diameter and the type of prosthesis on treatment outcomes. This retrospective cohort study initially included all 52 patients receiving dental implants between July 2006 and February 2008 at a private oral surgery clinic in Granada (Southern Spain). Clinical and radiographic examinations were performed, including periapical or panoramic radiographs, and incidences during completion of the restoration were recorded at 1 week, 3 months, 6 months, and at 1, 2, 3, 4, and 5 years. After a 5-year follow-up, 1 patient had died, 3 were lost to follow-up, and 6 required grafting before implant placement; therefore, the final study sample comprised 42 patients with 164 implants. Variables associated with the survival/failure of the restoration were: number of implants (higher failure rate with fewer implants), bone type (higher failure rate in type III or IV bone), and type of prosthesis (higher failure rate with single crowns). No significant association was found in univariate or multivariate analyses between survival rate and the loading protocol, implant length or diameter, or maxillary/mandibular location. Immediate occlusal loading, immediate provisionalization without occlusal loading, and early loading are viable treatment options with similar survival rates to those obtained with conventional loading. Bone quality and number of implants per patient were the most influential factors. © 2015 by the American College of Prosthodontists.

  9. Peri-implant evaluation of osseointegrated implants subjected to orthodontic forces: results after three years of functional loading

    Directory of Open Access Journals (Sweden)

    Bruna de Rezende Marins

    2016-04-01

    Full Text Available ABSTRACT Objective: The objective of this study was to clinically and radiographically assess the peri-implant conditions of implants used as orthodontic anchorage. Methods: Two groups were studied: 1 a test group in which osseointegrated implants were used as orthodontic anchorage, with the application of 200-cN force; and 2 a control group in which implants were not subjected to orthodontic force, but supported a screw-retained prosthesis. Clinical evaluations were performed three, six and nine months after prosthesis installation and 1- and 3-year follow-up examinations. Intraoral periapical radiographs were obtained 30 days after surgical implant placement, at the time of prosthesis installation, and one, two and three years thereafter. The results were compared by Kruskal-Wallis test. Results: There was no statistically significant difference in clinical probing depth (p = 0.1078 or mesial and distal crestal bone resorption (p = 0.1832 during the study period. After three years of follow-up, the mean probing depth was 2.21 mm for the control group and 2.39 mm for the test group. The implants of the control group showed a mean distance between the bone crest and implant shoulder of 2.39 mm, whereas the implants used as orthodontic anchorage showed a mean distance of 2.58 mm at the distal site. Conclusion: Results suggest that the use of stable intraoral orthodontic anchorage did not compromise the health of peri-implant tissues or the longevity of the implant.

  10. A Prospective Study of Early Loaded Single Implant-Retained Mandibular Overdentures: Preliminary One-Year Results

    Directory of Open Access Journals (Sweden)

    Ali M. El-Sheikh

    2012-01-01

    Full Text Available Purpose. To investigate the predictability of simplifying mandibular overdenture treatment using one-stage surgery and early prosthetic loading of a single implant. Materials and Methods. Twenty edentulous patients with problematic existing mandibular dentures were treated. A single implant with a chemically modified surface (SLActive, Straumann AG, Basel, Switzerland was placed into the mandibular midline. The patients were recalled at 3, 6 and 12 months. Clinical assessments and marginal bone loss using standardized radiographs were recorded. All complications, failures and maintenance were noted. Visual analog-scale questionnaires were used to record patient satisfaction in five categories. ANOVA was used to determine differences between means of marginal bone loss and different categories of patient staisfaction (=0.05. Results. The 20 early loaded implants were all surviving at the 12-month recall. All implants showed less than 1 mm of marginal bone loss by the end of the 1-year with a significant increase during the follow-up period. Few prosthetic problems were reported. Patient satisfaction was high with a significant increase in all comfort and functional parameters. Conclusions. These preliminary 1-year results indicate that early loading of a single chemically modified surface implant used to retain a mucosa-borne mandibular overdenture is a safe, reliable, and cost-effective treatment.

  11. Comparison of patient-reported outcomes between immediately and conventionally loaded mandibular two-implant overdentures: A preliminary study.

    Science.gov (United States)

    Omura, Yuri; Kanazawa, Manabu; Sato, Daisuke; Kasugai, Shohei; Minakuchi, Shunsuke

    2016-07-01

    The aim of this preliminary study is to compare patient-reported outcomes between immediately and conventionally loaded mandibular two-implant overdentures retained by magnetic attachments. Nineteen participants with edentulous mandibles were randomly assigned into either an immediate loading group (immediate group) or a conventional loading group (conventional group). Each participant received 2 implants in the inter-foraminal region by means of flapless surgery. Prostheses in the immediate and conventional groups were loaded using magnetic attachments on the same day as implant placement or 3 months after surgery, respectively. All participants completed questionnaires (the Japanese version of the Oral Health Impact Profile for edentulous [OHIP-EDENT-J], the patient's denture assessment [PDA], and general satisfaction) before implant placement (baseline) and 1, 2, 3, 4, 5, 6, and 12 months after surgery. The median differences between baseline and each monthly score were compared using the Mann-Whitney U test. The differences in median and 95% confidence interval between two groups were analyzed. The immediate group showed slightly lower OHIP-EDENT-J summary score at 1 and 3 months than the conventional group (P=0.09). In the lower denture domain of PDA, the immediate group showed a statistically higher score at 3 months (P=0.04). There was no statistically significant difference in general satisfaction between the two groups. Based on this preliminary study, immediate loading of mandibular two-implant overdentures with magnetic attachments tends to improve oral health-related quality of life and patient assessment earlier than observed with a conventional loading protocol. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  12. Maxillary and mandibular immediately loaded implant-supported interim complete fixed dental prostheses on immediately placed dental implants with a digital approach: A clinical report.

    Science.gov (United States)

    Lewis, Ryan C; Harris, Bryan T; Sarno, Robert; Morton, Dean; Llop, Daniel R; Lin, Wei-Shao

    2015-09-01

    This clinical report describes the treatment of maxillary and mandibular immediate implant placement and immediately loaded implant-supported interim complete fixed dental prostheses with a contemporary digital approach. The virtual diagnostic tooth arrangement eliminated the need for a customized radiographic template, and the diagnostic data collection required for computer-guided surgery (digital diagnostic impressions, digital photographs, and a cone beam-computed tomography [CBCT] scan) was completed in a single visit with improved workflow efficiency. Computer-aided design and computer-aided manufacturing (CAD/CAM)-fabricated surgical templates and interim prosthesis templates were made in a dental laboratory to facilitate computer-guided surgery and the immediate loading process. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  13. Xenoimplantation of an Extracellular-Matrix-Derived, Biphasic, Cell-Scaffold Construct for Repairing a Large Femoral-Head High-Load-Bearing Osteochondral Defect in a Canine Model

    Directory of Open Access Journals (Sweden)

    Yang Qiang

    2014-01-01

    Full Text Available This study was aimed to develop an ECM-derived biphasic scaffold and to investigate its regeneration potential loaded with BM-MSCs in repair of large, high-load-bearing osteochondral defects of the canine femoral head. The scaffolds were fabricated using cartilage and bone ECM as a cartilage and bone layer, respectively. Osteochondral constructs were fabricated using induced BM-MSCs and the scaffold. Osteochondral defects (11 mm diameter × 10 mm depth were created on femoral heads of canine and treated with the constructs. The repaired tissue was evaluated for gross morphology, radiography, histological, biomechanics at 3 and 6 months after implantation. Radiography revealed that femoral heads slightly collapsed at 3 months and severely collapsed at 6 months. Histology revealed that some defects in femoral heads were repaired, but with fibrous tissue or fibrocartilage, and femoral heads with different degrees of collapse. The bone volume fraction was lower for subchondral bone than normal femoral bone at 3 and 6 months. Rigidity was lower in repaired subchondral bone than normal femoral bone at 6 months. The ECM-derived, biphasic scaffold combined with induced BM-MSCs did not successfully repair large, high-load-bearing osteochondral defects of the canine femoral head. However, the experience can help improve the technique of scaffold fabrication and vascularization.

  14. Load-bearing Characters Analysis of Large Diameter Rock-Socketed Filling Piles Based on Self-Balanced Method

    Science.gov (United States)

    tongqing, Wu; liang, Li; xinjian, Liu; Xu, nianchun; Tian, Mao

    2018-03-01

    Self-balanced method is carried out on the large diameter rock-socketed filling piles of high-pile wharf at Inland River, to explore the distribution laws of load-displacement curve, pile internal force, pile tip friction resistance and pile side friction resistance under load force. The results showed that: the tip resistance of S1 and S2 test piles accounted for 53.4% and 53.6% of the pile bearing capacity, respectively, while the total side friction resistance accounted for 46.6% and 46.4% of the pile bearing capacity, respectively; both the pile tip friction resistance and pile side friction resistance can be fully played, and reach to the design requirements. The reasonability of large diameter rock-socketed filling design is verified through test analysis, which can provide basis for the optimization of high-pile wharf structural type, thus reducing the wharf project cost, and also providing reference for the similar large diameter rock-socketed filling piles of high-pile wharf at Inland River.

  15. Bone reactions adjacent to titanium implants with different surface characteristics subjected to static load. A study in the dog (II)

    DEFF Research Database (Denmark)

    Gotfredsen, K; Berglundh, T; Lindhe, J

    2001-01-01

    The purpose of the present study was to compare bone reactions adjacent to titanium implants with either a titanium plasma-sprayed (TPS) or a machined surface subjected to lateral static loading induced by an expansion force. In 3 labrador dogs, the 2nd, 3rd and 4th mandibular premolars were...

  16. The influence of Young's modulus of loaded implants on bone remodeling: an experimental and numerical study in the goat knee.

    NARCIS (Netherlands)

    Stoppie, N.; Oosterwyck, H. Van; Jansen, J.A.; Wolke, J.G.C.; Wevers, M.; Naert, I.

    2009-01-01

    The aim of this study was to examine the influence of the Young's modulus of the implant material on the bone remodeling in a loaded condition. A combined animal experimental and computational study was set up. The animal experimental group comprised of 16 Saanen goats, each receiving one titanium

  17. Immediate versus delayed loading of strategic mini dental implants for the stabilization of partial removable dental prostheses: a patient cluster randomized, parallel-group 3-year trial.

    Science.gov (United States)

    Mundt, Torsten; Al Jaghsi, Ahmad; Schwahn, Bernd; Hilgert, Janina; Lucas, Christian; Biffar, Reiner; Schwahn, Christian; Heinemann, Friedhelm

    2016-07-30

    Acceptable short-term survival rates (>90 %) of mini-implants (diameter implants as strategic abutments for a better retention of partial removable dental prosthesis (PRDP) are not available. The purpose of this study is to test the hypothesis that immediately loaded mini-implants show more bone loss and less success than strategic mini-implants with delayed loading. In this four-center (one university hospital, three dental practices in Germany), parallel-group, controlled clinical trial, which is cluster randomized on patient level, a total of 80 partially edentulous patients with unfavourable number and distribution of remaining abutment teeth in at least one jaw will receive supplementary min-implants to stabilize their PRDP. The mini-implant are either immediately loaded after implant placement (test group) or delayed after four months (control group). Follow-up of the patients will be performed for 36 months. The primary outcome is the radiographic bone level changes at implants. The secondary outcome is the implant success as a composite variable. Tertiary outcomes include clinical, subjective (quality of life, satisfaction, chewing ability) and dental or technical complications. Strategic implants under an existing PRDP are only documented for standard-diameter implants. Mini-implants could be a minimal invasive and low cost solution for this treatment modality. The trial is registered at Deutsches Register Klinischer Studien (German register of clinical trials) under DRKS-ID: DRKS00007589 ( www.germanctr.de ) on January 13(th), 2015.

  18. Analysis of load distribution in tooth-implant supported fixed partial dentures by the use of resilient abutment.

    Science.gov (United States)

    Glisić, Mirko; Stamenković, Dragoslav; Grbović, Aleksandar; Todorović, Aleksandar; Marković, Aleksa; Trifković, Branka

    2016-01-01

    Differences between the tooth and implant response to load can lead to many biological and technical implications in the conditions of occlusal forces. The objective of this study was to analyze load distribution in tooth/implant-supported fixed partial dentures with the use of resilient TSA (Titan Shock Absorber, BoneCare GmbH, Augsburg, Germany) abutment and conventional non-resilient abutment using finite element method. This study presents two basic 3D models. For one model a standard non-resilient abutment is used, and on the implant of the second model a resilient TSA abutment is applied. The virtual model contains drawn contours of tooth, mucous membranes, implant, cortical bones and spongiosa, abutment and suprastructure. The experiment used 500 N of vertical force, applied in three different cases of axial load. Calculations of von Mises equivalent stresses of the tooth root and periodontium, implants and peri-implant tissue were made. For the model to which a non-resilient abutment is applied, maximum stress values in all three cases are observed in the cortical part of the bone (maximum stress value of 49.7 MPa). Measurements of stress and deformation in the bone tissue in the model with application of the resilientTSA abutment demonstrated similar distribution; however, these values are many times lower than in the model with non-resilient TSA abutment (maximum stress value of 28.9 MPa). Application of the resilient TSA abutment results in more equal distribution of stress and deformations in the bone tissue under vertical forces. These values are many times lower than in the model with the non-resilient abutment.

  19. Lifetime Assessment of Load-Bearing Polymer Glasses: The Influence of Physical Ageing

    NARCIS (Netherlands)

    Visser, Roy; Bor, Teunis Cornelis; Wolters, Mannes; Wismans, Joris G.F.; Govaert, Leon E.

    2010-01-01

    The timescale at which ductile failure occurs in loaded glassy polymers can be successfully predicted using the engineering approach presented in a previous publication. In this paper the influence of progressive physical ageing on the plastic deformation behaviour of unplasticised poly(vinyl

  20. Lifetime assessment of load-bearing polymer glasses : the influence of physical ageing

    NARCIS (Netherlands)

    Visser, H.A.; Bor, T.C.; Wolters, M.; Wismans, J.G.F.; Govaert, L.E.

    2010-01-01

    The timescale at which ductile failure occurs in loaded glassy polymers can be successfullypredicted using the engineering approach presented in a previous publication.In this paper the influence of progressive physical ageing on the plastic deformationbehaviour of uPVC is characterised and

  1. Advanced interlocking systems to improve heavy-load-bearing characteristics of flexible intramedullary nailing

    Energy Technology Data Exchange (ETDEWEB)

    Berger, Leopold, E-mail: leopold.berger@tuwien.ac.at [Institute of Building Construction and Technology, TU Wien, Karlsplatz 13/206-4, 1040 Vienna (Austria); Eichler, Johannes [Department of Orthopedics and Orthopedic Surgery, Medical University of Graz, Auenbruggerplatz 5/6, 8036 Graz (Austria); Ryll, E. Jonathan S. [Department of Trauma-, Hand- and Reconstructive Surgery, University Hospital Muenster, Westphalian-Wilhelms University, Muenster (Germany); Fischerauer, Stefan [Department of Traumatology, Medical University of Graz, Auenbruggerplatz 5/6, 8036 Graz (Austria); Raschke, Michael J. [Department of Trauma-, Hand- and Reconstructive Surgery, University Hospital Muenster, Westphalian-Wilhelms University, Muenster (Germany); Kolbitsch, Andreas [Institute of Building Construction and Technology, TU Wien, Karlsplatz 13/206-4, 1040 Vienna (Austria); Castellani, Christoph [Department of Pediatric and Adolescence Surgery, Medical University of Graz, Auenbruggerplatz 34, 8036 Graz (Austria); Weinberg, Annelie-Martina [Department of Orthopedics and Orthopedic Surgery, Medical University of Graz, Auenbruggerplatz 5/6, 8036 Graz (Austria)

    2016-11-01

    Flexible intramedullary nailing (FIN) is a minimally invasive and widespread standard method for osteosynthesis of pediatric long bone fractures. In the case of unstable fractures of the lower extremity, interlocking systems need to be used to prevent axial shortening and subsequent perforation of the nail at its insertion site. In the present study, four different screw-fixed interlocking systems for FINs (Hofer TwinPlug with two 3-mm titanium interlocking screws, Hofer FixPlug with 3-mm titanium interlocking screw, Hofer Plug with 3.5-mm titanium interlocking screw, and Hofer Plug with 3-mm titanium interlocking screw) in comparison with the commonly used Ender stainless steel nails (locked with 3.5-mm screw) were experimentally investigated in cadaveric lamb tibiae, regarding their load characteristics and failure modes in the case of heavy loading. The specimens were subjected to sequential axial cyclic loading of 5000cycles with stepwise increase of the load amplitude until failure. Migration of locking screws and internal damage of bone tissue was quantified by micro-computed tomography (CT) imaging. Ender nails failed on average at a peak load of 800 N, TwinPlugs at 1367 N, FixPlugs at 1222 N, Plugs 3.5mm at 1225 N and Plugs 3.0mm at 971 N. TwinPlugs, FixPlugs, and Plugs 3.5mm failed in a slow manner over several hundred loading cycles, whereas Ender nails and Plugs 3.0mm exhibited abrupt failure without any prior indication. Our results confirm that axial stability of FIN can be further improved by screw-fixed plugs by simultaneously avoiding shortcomings of an eye-locked system, which the Ender nails are. Considering biomechanical results, plug interlocking systems with 3.5-mm screws should be favored over conventional Ender nails and plugs with 3-mm screws. - Highlights: • Locked flexible intramedullary nails in lamb tibiae were cyclically loaded. • Strongly different failure modes of locking systems were detected. • Novel screw-fixed plugs are

  2. Evaluation of the increased load bearing capacity of steel beams strengthened with pre-stressed FRP laminates

    Directory of Open Access Journals (Sweden)

    S. Bennati

    2016-10-01

    Full Text Available We analyse the problem of a simply supported steel beam subjected to uniformly distributed load, strengthened with a pre-stressed fibre-reinforced polymer (FRP laminate. We assume that the laminate is first put into tension, then bonded to the beam bottom surface, and finally fixed at both its ends by suitable connections. The beam and laminate are modelled according to classical beam theory. The adhesive is modelled as a cohesive interface with a piecewise linear constitutive law defined over three intervals (elastic response, softening response, debonding. The model is described by a set of differential equations with suitable boundary conditions. An analytical solution to the problem is determined, including explicit expressions for the internal forces and interfacial stresses. As an application, we consider the standard IPE series for the steel beam and the Sika® CarboDur® system for the adhesive and laminate. For each considered cross section, we first carry out a preliminary design of the unstrengthened steel beam. Then, we imagine to apply the FRP strengthening and calculate the loads corresponding to the elastic limit states in the steel beam, adhesive, and laminate. Lastly, we take into account the ultimate limit state corresponding to the plasticisation of the mid-span steel cross section and evaluate the increased load bearing capacity of the strengthened beam

  3. Influence of surgical and prosthetic techniques on marginal bone loss around titanium implants. Part I: immediate loading in fresh extraction sockets.

    Science.gov (United States)

    Berberi, Antoine N; Tehini, Georges E; Noujeim, Ziad F; Khairallah, Alexandre A; Abousehlib, Moustafa N; Salameh, Ziad A

    2014-10-01

    Delayed placement of implant abutments has been associated with peri-implant marginal bone loss; however, long-term results obtained by modifying surgical and prosthetic techniques after implant placement are still lacking. This study aimed to evaluate the marginal bone loss around titanium implants placed in fresh extraction sockets using two loading protocols after a 5-year follow-up period. A total of 36 patients received 40 titanium implants (Astra Tech) intended for single-tooth replacement. Implants were immediately placed into fresh extraction sockets using either a one-stage (immediate loading by placing an interim prosthesis into functional occlusion) or a two-stage prosthetic loading protocol (insertion of abutments after 8 weeks of healing time). Marginal bone levels relative to the implant reference point were evaluated at four time intervals using intraoral radiographs: at time of implant placement, and 1, 3, and 5 years after implant placement. Measurements were obtained from mesial and distal surfaces of each implant (α = 0.05). One-stage immediate implant placement into fresh extraction sockets resulted in a significant reduction in marginal bone loss (p sockets reduced marginal bone loss and did not compromise the success rate of the restorations. © 2014 by the American College of Prosthodontists.

  4. In vitro and in vivo investigation of bisphosphonate-loaded hydroxyapatite particles for peri-implant bone augmentation.

    Science.gov (United States)

    Kettenberger, Ulrike; Luginbuehl, Vera; Procter, Philip; Pioletti, Dominique P

    2017-07-01

    Locally applied bisphosphonates, such as zoledronate, have been shown in several studies to inhibit peri-implant bone resorption and recently to enhance peri-implant bone formation. Studies have also demonstrated positive effects of hydroxyapatite (HA) particles on peri-implant bone regeneration and an enhancement of the anti-resorptive effect of bisphosphonates in the presence of calcium. In the present study, both hydroxyapatite nanoparticles (nHA) and zoledronate were combined to achieve a strong reinforcing effect on peri-implant bone. The nHA-zoledronate combination was first investigated in vitro with a pre-osteoclastic cell assay (RAW 264.7) and then in vivo in a rat model of postmenopausal osteoporosis. The in vitro study confirmed that the inhibitory effect of zoledronate on murine osteoclast precursor cells was enhanced by loading the drug on nHA. For the in vivo investigation, either zoledronate-loaded or pure nHA were integrated in hyaluronic acid hydrogel. The gels were injected in screw holes that had been predrilled in rat femoral condyles before the insertion of miniature screws. Micro-CT-based dynamic histomorphometry and histology revealed an unexpected rapid mineralization of the hydrogel in vivo through formation of granules, which served as scaffold for new bone formation. The delivery of zoledronate-loaded nHA further inhibited a degradation of the mineralized hydrogel as well as a resorption of the peri-implant bone as effectively as unbound zoledronate. Hyaluronic acid with zoledronate-loaded nHA, thanks to its dual effect on inducing a rapid mineralization and preventing resorption, is a promising versatile material for bone repair and augmentation. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  5. Fab’-bearing siRNA TNFα-loaded nanoparticles targeted to colonic macrophages offer an effective therapy for experimental colitis

    Science.gov (United States)

    Hamed, Laroui; Emilie, Viennois; Xiao, Bo; Canup, Brandon S.; Duke, Geem; Denning, Timothy L.; Didier, Merlin

    2014-01-01

    Patients suffering from Inflammatory Bowel Disease (IBD) are currently treated by systemic drugs that can have significant side effects. Thus, it would be highly desirable to target TNFα siRNA (a therapeutic molecule) to the inflamed tissue. Here, we demonstrate that TNFα siRNA can be efficiently loaded into nanoparticles (NPs) made of poly (lactic acid) poly (ethylene glycol) block copolymer (PLA-PEG), and that grafting of the Fab’ portion of the F4/80 Ab (Fab’-bearing) onto the NP surface via maleimide/thiol group-mediated covalent bonding improves the macrophage (MP)-targeting kinetics of the NPs to RAW264.7 cells in vitro. Direct binding was shown between MPs and the Fab’-bearing NPs. Next, we orally administered hydrogel (chitosan/alginate)-encapsulated Fab’-bearing TNFα-siRNA-loaded NPs to 3% dextran sodium sulfate (DSS)-treated mice and investigated the therapeutic effect on colitis. In vivo, the release of TNFα-siRNA-loaded NPs into the mouse colon attenuated colitis more efficiently when the NPs were covered with Fab’-bearing, compared to uncovered NPs. All DSS-induced parameters of colonic inflammation (e.g., weight loss, myeloperoxidase activity, and Iκbα accumulation) were more attenuated Fab’-bearing NPs loaded with TNFα siRNA than without the Fab’-bearing. Grafting the Fab’-bearing onto the NPs improved the kinetics of endocytosis as well as the MP-targeting ability, as indicated by flow cytometry. Collectively, our results show that Fab’-bearing PLA-PEG NPs are powerful and efficient nanosized tools for delivering siRNAs into colonic macrophages. PMID:24810114

  6. Factors affecting date of implantation, parturition, and den entry estimated from activity and body temperature in free-ranging brown bears.

    Science.gov (United States)

    Friebe, Andrea; Evans, Alina L; Arnemo, Jon M; Blanc, Stéphane; Brunberg, Sven; Fleissner, Günther; Swenson, Jon E; Zedrosser, Andreas

    2014-01-01

    Knowledge of factors influencing the timing of reproduction is important for animal conservation and management. Brown bears (Ursus arctos) are able to vary the birth date of their cubs in response to their fat stores, but little information is available about the timing of implantation and parturition in free-ranging brown bears. Body temperature and activity of pregnant brown bears is higher during the gestation period than during the rest of hibernation and drops at parturition. We compared mean daily body temperature and activity levels of pregnant and nonpregnant females during preimplantation, gestation, and lactation. Additionally we tested whether age, litter size, primiparity, environmental conditions, and the start of hibernation influence the timing of parturition. The mean date of implantation was 1 December (SD = 12), the mean date of parturition was 26 January (SD = 12), and the mean duration of the gestation period was 56 days (SD = 2). The body temperature of pregnant females was higher during the gestation and lactation periods than that of nonpregnant bears. The body temperature of pregnant females decreased during the gestation period. Activity recordings were also used to determine the date of parturition. The parturition dates calculated with activity and body temperature data did not differ significantly and were the same in 50% of the females. Older females started hibernation earlier. The start of hibernation was earlier during years with favorable environmental conditions. Dates of parturition were later during years with good environmental conditions which was unexpected. We suggest that free-ranging pregnant brown bears in areas with high levels of human activities at the beginning of the denning period, as in our study area, might prioritize investing energy in early denning than in early parturition during years with favorable environmental conditions, as a strategy to prevent disturbances caused by human.

  7. Factors affecting date of implantation, parturition, and den entry estimated from activity and body temperature in free-ranging brown bears.

    Directory of Open Access Journals (Sweden)

    Andrea Friebe

    Full Text Available Knowledge of factors influencing the timing of reproduction is important for animal conservation and management. Brown bears (Ursus arctos are able to vary the birth date of their cubs in response to their fat stores, but little information is available about the timing of implantation and parturition in free-ranging brown bears. Body temperature and activity of pregnant brown bears is higher during the gestation period than during the rest of hibernation and drops at parturition. We compared mean daily body temperature and activity levels of pregnant and nonpregnant females during preimplantation, gestation, and lactation. Additionally we tested whether age, litter size, primiparity, environmental conditions, and the start of hibernation influence the timing of parturition. The mean date of implantation was 1 December (SD = 12, the mean date of parturition was 26 January (SD = 12, and the mean duration of the gestation period was 56 days (SD = 2. The body temperature of pregnant females was higher during the gestation and lactation periods than that of nonpregnant bears. The body temperature of pregnant females decreased during the gestation period. Activity recordings were also used to determine the date of parturition. The parturition dates calculated with activity and body temperature data did not differ significantly and were the same in 50% of the females. Older females started hibernation earlier. The start of hibernation was earlier during years with favorable environmental conditions. Dates of parturition were later during years with good environmental conditions which was unexpected. We suggest that free-ranging pregnant brown bears in areas with high levels of human activities at the beginning of the denning period, as in our study area, might prioritize investing energy in early denning than in early parturition during years with favorable environmental conditions, as a strategy to prevent disturbances caused by human.

  8. Hysteresis model of shape memory alloy wire-based laminated rubber bearing under compression and unidirectional shear loadings

    International Nuclear Information System (INIS)

    Hedayati Dezfuli, F; Alam, M Shahria

    2015-01-01

    Smart lead rubber bearings (LRBs), in which a shape memory alloy (SMA) is used in the form of wires, are a new generation of elastomeric isolators with improved performance in terms of recentering capability and energy dissipation capacity. It is of great interest to implement SMA wire-based lead rubber bearings (SMA-LRBs) in bridges; however, currently there is no appropriate hysteresis model for accurately simulating the behavior of such isolators. A constitutive model for SMA-LRBs is proposed in this study. An LRB is equipped with a double cross configuration of SMA wires (DC-SMAW) and subjected to compression and unidirectional shear loadings. Due to the complexity of the shear behavior of the SMA-LRB, a hysteresis model is developed for the DC-SMAWs and then combined with the bilinear kinematic hardening model, which is assumed for the LRB. Comparing the hysteretic response of decoupled systems with that of the SMA-LRB shows that the high recentering capability of the DC-SMAW model with zero residual deformation could noticeably reduce the residual deformation of the LRB. The developed constitutive model for DC-SMAWs is characterized by three stiffnesses when the shear strain exceeds a starting limit at which the SMA wires are activated due to phase transformation. An important point is that the shear hysteresis of the DC-SMAW model looks different from the flag-shaped hysteresis of the SMA because of the specific arrangement of wires and its effect on the resultant forces transferred from the wires to the rubber bearing. (paper)

  9. Metal Ion Concentrations in Body Fluids after Implantation of Hip Replacements with Metal-on-Metal Bearing – Systematic Review of Clinical and Epidemiological Studies

    Science.gov (United States)

    Hartmann, Albrecht; Hannemann, Franziska; Lützner, Jörg; Seidler, Andreas; Drexler, Hans; Günther, Klaus-Peter; Schmitt, Jochen

    2013-01-01

    Introduction The use of metal-on-metal (MoM) total hip arthroplasty (THA) increased in the last decades. A release of metal products (i.e. particles, ions, metallo-organic compounds) in these implants may cause local and/or systemic adverse reactions. Metal ion concentrations in body fluids are surrogate measures of metal exposure. Objective To systematically summarize and critically appraise published studies concerning metal ion concentrations after MoM THA. Methods Systematic review of clinical trials (RCTs) and epidemiological studies with assessment of metal ion levels (cobalt, chromium, titanium, nickel, molybdenum) in body fluids after implantation of metalliferous hip replacements. Systematic search in PubMed and Embase in January 2012 supplemented by hand search. Standardized abstraction of pre- and postoperative metal ion concentrations stratified by type of bearing (primary explanatory factor), patient characteristics as well as study quality characteristics (secondary explanatory factors). Results Overall, 104 studies (11 RCTs, 93 epidemiological studies) totaling 9.957 patients with measurement of metal ions in body fluids were identified and analyzed. Consistently, median metal ion concentrations were persistently elevated after implantation of MoM-bearings in all investigated mediums (whole blood, serum, plasma, erythrocytes, urine) irrespective of patient characteristics and study characteristics. In several studies very high serum cobalt concentrations above 50 µg/L were measured (detection limit typically 0.3 µg/L). Highest metal ion concentrations were observed after treatment with stemmed large-head MoM-implants and hip resurfacing arthroplasty. Discussion Due to the risk of local and systemic accumulation of metallic products after treatment with MoM-bearing, risk and benefits should be carefully balanced preoperatively. The authors support a proposed „time out“ for stemmed large-head MoM-THA and recommend a restricted indication for hip

  10. Metal ion concentrations in body fluids after implantation of hip replacements with metal-on-metal bearing--systematic review of clinical and epidemiological studies.

    Directory of Open Access Journals (Sweden)

    Albrecht Hartmann

    Full Text Available INTRODUCTION: The use of metal-on-metal (MoM total hip arthroplasty (THA increased in the last decades. A release of metal products (i.e. particles, ions, metallo-organic compounds in these implants may cause local and/or systemic adverse reactions. Metal ion concentrations in body fluids are surrogate measures of metal exposure. OBJECTIVE: To systematically summarize and critically appraise published studies concerning metal ion concentrations after MoM THA. METHODS: Systematic review of clinical trials (RCTs and epidemiological studies with assessment of metal ion levels (cobalt, chromium, titanium, nickel, molybdenum in body fluids after implantation of metalliferous hip replacements. Systematic search in PubMed and Embase in January 2012 supplemented by hand search. Standardized abstraction of pre- and postoperative metal ion concentrations stratified by type of bearing (primary explanatory factor, patient characteristics as well as study quality characteristics (secondary explanatory factors. RESULTS: Overall, 104 studies (11 RCTs, 93 epidemiological studies totaling 9.957 patients with measurement of metal ions in body fluids were identified and analyzed. Consistently, median metal ion concentrations were persistently elevated after implantation of MoM-bearings in all investigated mediums (whole blood, serum, plasma, erythrocytes, urine irrespective of patient characteristics and study characteristics. In several studies very high serum cobalt concentrations above 50 µg/L were measured (detection limit typically 0.3 µg/L. Highest metal ion concentrations were observed after treatment with stemmed large-head MoM-implants and hip resurfacing arthroplasty. DISCUSSION: Due to the risk of local and systemic accumulation of metallic products after treatment with MoM-bearing, risk and benefits should be carefully balanced preoperatively. The authors support a proposed "time out" for stemmed large-head MoM-THA and recommend a restricted

  11. Plastic material investment in load-bearing silk attachments in spiders.

    Science.gov (United States)

    Wolff, Jonas O; Jones, Braxton; Herberstein, Marie E

    2018-05-17

    The nature and size of attachments is a fundamental element of animal constructions. Presumably, these adhesive structures are plastically deployed to balance material investment and attachment strength. Here we studied plasticity in dragline anchorages of the golden orb web spider, Nephila plumipes. Specifically, we predict that spiders adjust the size and structure of dragline anchorages with load, i.e. spider mass. Mass was manipulated by attaching lead pieces to the spider's abdomen resulting in a 50 percent increase in mass. Loaded spiders spun larger but structurally similar thread anchorages than unloaded spiders. Thus, the spinning program that determines the overall anchor structure is highly stereotypic, and flexibility is introduced through varying the anchor size by increasing material investment. Our study showcases substrate attachments as suitable models to investigate the interplay between innate and changeable elements in the economy of building behaviours. Copyright © 2018 Elsevier GmbH. All rights reserved.

  12. Evaluation of ultimate load bearing capacity of the primary containment of a typical 540 MWe Indian PHWR

    International Nuclear Information System (INIS)

    Ray, Indrajit; Roy, Raghupati; Verma, U.S.P.; Warudkar, A.S.

    2003-01-01

    This paper presents the analysis of the Inner Containment Structure (ICS) of a typical 540 MWe Indian PHWR for the purpose of evaluating its ultimate load bearing capacity (ULBC) under beyond postulated design basis accident (DBA) scenario. The methodology adopted for the non-linear analysis of the prestressed concrete ICS including the various issues, viz. behaviour of concrete under compression and tension, tension stiffening, cracked shear modulus etc. have also been discussed in this paper. The effect of accident temperature on ULBC has been studied and discussed in this paper. This paper also discusses about the study carried out for mesh sensitivity of the finite element (FE) discretization on ULBC of ICS in the non-linear range. Based on the detailed analysis, the factor of safety of the ICS under beyond postulated DBA scenario has been evaluated. (author)

  13. Mechanical analysis and optimisation of large and highly-loaded bearing rollers For the "Riesenrad" Ion Gantry

    CERN Document Server

    Reimoser, S A

    2000-01-01

    A carbon ion gantry would allow the irradiation of cancer patients with carbon ions from any direction in space best suited for therapy. Till today, such a machine has not been built due to the expected size, mass and cost. A novel design, called "Riesenrad" ion gantry, promises to provide a competitive solution. The central part of the Riesenrad, which can rotate ± 90°, is supported (statically determinate) on pendular bearing units with two rollers each. High precision requirements for the structure rule out any plastic deformations in the area of contact. The present report describes the design of the highly-loaded rollers. In order to achieve a large contact area and a uniform distribution of contact stresses, a "barrel shape" for the rollers is proposed. An analysis using the finite element method (FEM) was performed to optimise the roller design, namely to establish the required crown roll (camber radius).

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

    Science.gov (United States)

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

    2016-01-01

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

  15. Influence of crop load on the expression patterns of starch metabolism genes in alternate-bearing citrus trees.

    Science.gov (United States)

    Nebauer, Sergio G; Renau-Morata, Begoña; Lluch, Yolanda; Baroja-Fernández, Edurne; Pozueta-Romero, Javier; Molina, Rosa-Victoria

    2014-07-01

    The fruit is the main sink organ in Citrus and captures almost all available photoassimilates during its development. Consequently, carbohydrate partitioning and starch content depend on the crop load of Citrus trees. Nevertheless, little is known about the mechanisms controlling the starch metabolism at the tree level in relation to presence of fruit. The aim of this study was to find the relation between the seasonal variation of expression and activity of the genes involved in carbon metabolism and the partition and allocation of carbohydrates in 'Salustiana' sweet orange trees with different crop loads. Metabolisable carbohydrates, and the expression and activity of the enzymes involved in sucrose and starch metabolism, including sucrose transport, were determined during the year in the roots and leaves of 40-year-old trees bearing heavy crop loads ('on' trees) and trees with almost no fruits ('off' trees). Fruit altered photoassimilate partitioning in trees. Sucrose content tended to be constant in roots and leaves, and surplus fixed carbon is channeled to starch production. Differences between 'on' and 'off' trees in starch content can be explained by differences in ADP-glucose pyrophosphorylase (AGPP) expression/activity and α-amylase activity which varies depending on crop load. The observed relation of AGPP and UGPP (UDP-glucose pyrophosphorylase) is noteworthy and indicates a direct link between sucrose and starch synthesis. Furthermore, different roles for sucrose transporter SUT1 and SUT2 have been proposed. Variation in soluble sugars content cannot explain the differences in gene expression between the 'on' and 'off' trees. A still unknown signal from fruit should be responsible for this control. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  16. A 5-year comparison of marginal bone level following immediate loading of single-tooth implants placed in healed alveolar ridges and extraction sockets in the maxilla.

    Science.gov (United States)

    Berberi, Antoine N; Sabbagh, Joseph M; Aboushelib, Moustafa N; Noujeim, Ziad F; Salameh, Ziad A

    2014-01-01

    The aim of present investigation was to evaluate marginal bone level after 5-year follow-up of implants placed in healed ridges and fresh extraction sockets in maxilla with immediate loading protocol. Thirty-six patients in need of a single-tooth replacement in the anterior maxilla received 42 Astra Tech implants (Astra Tech Implant system™, Dentsply Implants, Mölndal, Sweden). Implants were placed either in healed ridges (group I) or immediately into fresh extraction sockets (group II). Implants were restored and placed into functional loading immediately by using a prefabricated abutment. Marginal bone level relative to the implant reference point was recorded at implant placement, crown cementation, 12, 36, and 60 months following loading using intra-oral radiographs. Measurements were made on the mesial and distal sides of each implant. Overall, two implants were lost from the group II, before final crown cementation: they were excluded from the study. The mean change in marginal bone loss (MBL) after implant placement was 0.26 ± 0.161 mm for 1 year, and 0.26 ± 0.171 mm for 3 years, and 0.21 ± 0.185 mm for 5 years in extraction sockets and was 0.26 ± 0.176 mm for 1 year and 0.21 ± 0.175 mm for 3 years, and 0.19 ± 0.172 mm for 5 years in healed ridges group. Significant reduction of marginal bone was more pronounced in implants inserted in healed ridges (P sockets (P sockets or healed ridges were similar. Functional loading technique by using prefabricated abutment placed during the surgery time seems to maintain marginal bone around implant in both healed and fresh extraction sites.

  17. A 5- Year Comparison of Marginal Bone Level Following Immediate Loading of Single-Tooth Implants Placed in Healed Alveolar Ridges and Extraction Sockets in the Maxilla.

    Directory of Open Access Journals (Sweden)

    Antoine Nicolas Berberi

    2014-01-01

    Full Text Available AbstractPurpose: The aim of present investigation was to evaluate marginal bone level after 5-year follow-up of implants placed in healed ridges and fresh extraction sockets in maxilla with immediate loading protocol.Materials and Methods: Thirty-six patients in need of a single tooth replacement in the anterior maxilla received 42 Astra Tech implants (Astra Tech Implant system™, Dentsply Implants, Mölndal, Sweden. Implants were placed in healed ridges (group I or immediately into extraction sockets (group II. Implants were restored and placed into functional loading immediately by using a prefabricated abutment. Marginal bone level relative to the implant reference point was recorded at implant placement, crown cementation, 12, 36 and 60 months following loading using intra-oral radiographs. Measurements were made on the mesial and distal sides of each implantResults: Overall, two implants were lost from the group II, before final crown cementation: they were excluded from the study and all remaining implants osseointegrated successfully after 5 years of functional loading. The mean change in marginal bone loss after implant placement was 0.267±0.161 for one year, and 0.265±0.171 for three years and 0.213±0.185 for five years in extraction sockets and was 0.266±0.176 for one year and 0.219±0.175 for three years and 0.194±0.172 for five years in healed ridges group. Significant reduction of marginal bone loss was more pronounced in implants inserted in healed ridges (P

  18. Effect of macro-design of immediately loaded implants on micromotion and stress distribution in surrounding bone using finite element analysis.

    Science.gov (United States)

    Fazel, Akbar; Aalai, Shima; Rismanchian, Mansour

    2009-08-01

    Macro-design influences the initial stability of implant and reduces micromotions. The aim of this study was to determine and compare micromotions and stress distribution in the bone around immediately loaded Maestro and Xive implants using finite element analysis. In this experimental study, accurate, clear photos were prepared of Xive and Maestro implants 12 and 13 mm long and 4 and 3.8 mm in diameter, respectively, using a Nikon Digital Camera with a resolution 5.24-megapixels with 8x Optical Zoom and 4x Digital Zoom. After accurate measurements, 3-D models of the implants inside the lower mandible (D2) were processed in Solidworks Version 2003 environment and transferred into Ansys for finite element analysis. After loading of 500 N angled at 70 degrees from the horizontal plane, the micromotion of the implant and Von Misses stresses around the bone were measured. The measured micromotion in Maestro implant was 148 mum and that in Xive was 284 mum. Stress distribution in the bone surrounding Maestro implant was better than Xive, but maximum stress surrounding Xive implants (30 MPa) was lower than Maestro (33 MPa). Based on the results obtained in the present study, maximum micromotion in maestro was less than that in Xive implants. This finding can guarantee the application of maestro implants for immediate loading.

  19. Immediate versus early non-occlusal loading of dental implants placed flapless in partially edentulous patients: a 3-year randomized clinical trial.

    Science.gov (United States)

    Merli, Mauro; Moscatelli, Marco; Mariotti, Giorgia; Piemontese, Matteo; Nieri, Michele

    2012-02-01

    To compare immediate versus early non-occlusal loading of dental implants placed flapless in a 3-year, parallel group, randomized clinical trial. The study was conducted in a private dental clinic between July 2005 and July 2010. Patients 18 years or older were randomized to receive implants for fixed partial dentures in cases of partial edentulism. The test group was represented by immediate non-occlusal implant loading, whereas the control group was represented by early non-occlusal implant loading. The outcome variables were implant failure, complications and radiographic bone level at implant sites 3 years after loading, measured from the implant-abutment junction to the most coronal point of bone-to-implant contact. Randomization was computer-generated with allocation concealment by opaque sequentially numbered sealed envelopes, and the measurer was blinded to group assignment. Sixty patients were randomized: 30 to the immediately loaded group and 30 to the early loaded group. Four patients dropped out; however, the data of all patients were included in the analysis. No implant failure occurred. Two complications occurred in the control group and one in the test group. The mean bone level at 3 years was 1.91 mm for test group and 1.59 mm for control group. The adjusted difference in bone level was 0.26 mm (CI 95% -0.08 to 0.59, p = 0.1232). The null hypothesis of no difference in failure rates, complications and bone level between implants that were loaded immediately or early at 3 years cannot be rejected in this randomized clinical trial. © 2011 John Wiley & Sons A/S.

  20. Satisfaction and Clinical Outcomes Among Patients with Immediately Loaded Mandibular Overdentures Supported by One or Two Dental Implants: Results of a 5-Year Prospective Randomized Clinical Trial.

    Science.gov (United States)

    Kronstrom, Mats; Davis, Ben; Loney, Robert; Gerrow, Jack; Hollender, Lars

    The purpose of this study was to evaluate patient satisfaction and clinical outcomes among subjects with mandibular overdentures supported by one or two immediately placed dental implants 5 years after loading. Thirty-six subjects (16 men and 20 women) received one or two dental implants in the anterior mandible, and all implants were loaded the day of surgery. Subjects were scheduled for follow-up 3-, 6-, and 12 months after implant placement and thereafter annually for 4 more years. Patient satisfaction scores were measured with the Oral Health Impact Profile-EDENT (OHIPEDENT) questionnaire. Seventeen subjects (7 male and 10 female) with a mean age of 59.4 years (range, 44 to 74 years) were available for the 5-year follow-up examination. Nine subjects with 10 failing implants were excluded during the first year and nine subjects were lost to follow-up. No implants failed between the 12- and 60-month follow-up examinations, and the need for denture maintenance was low. Mean peri-implant bone change was 0.92 mm, and the Spearman test failed to show correlation between the insertion torque value and implant stability quotient. Patient satisfaction scores increased significantly when compared with baseline values and continued to be high for both groups, with no significant differences. Ten implants in nine subjects failed early, but no failures were observed after the 12-month examination. No significant differences were found between subjects in the two groups with respect to implant survival rates and peri-implant bone loss, and patient satisfaction scores continued to be high. Although patient satisfaction and implant success were high during the 12- to 60-month period, the results should be interpreted with caution because of the high number of failing implants and patients lost to follow-up. More research is needed to study outcomes of treatment with immediately loaded mandibular implant overdentures.

  1. Marginal Bone Loss Around Early-Loaded SLA and SLActive Implants: Radiological Follow-Up Evaluation Up to 6.5 Years.

    Science.gov (United States)

    Şener-Yamaner, Işil Damla; Yamaner, Gökhan; Sertgöz, Atilla; Çanakçi, Cenk Fatih; Özcan, Mutlu

    2017-08-01

    The aim of this study was to compare marginal bone loss around early-loaded SLA and SLActive tissue-level implants (Straumann Dental Implants; Institut Straumann AG, Basel, Switzerland) after a mean of 81-month follow-up period. One hundred seven SLA and 68 SLActive implants were placed in 55 patients and loaded with final restoration after 8 and 3 weeks of healing time, respectively. Marginal bone loss around implants was determined radiographically at initial and after a mean observation time ranging between 20 and 81 months. The effect of location (mandible vs maxilla), smoking habit, sex, implant length and diameter, and the type of prosthesis on the marginal bone loss was evaluated. The overall cumulative survival rate was 98.2% being 99% for SLA implants and 97% for SLActive implants. After 20-month follow-up period, mean marginal bone loss values for the SLA and SLActive implants were 0.24 and 0.17 mm, respectively. After 81 months, mean marginal bone loss for the SLA and SLActive implants reached 0.71 and 0.53 mm, respectively. Marginal bone loss was affected by the length and type of implant and patients' smoking habit after a mean observation time of 20 months. However, none of the parameters had any significant effect on the marginal bone loss after a follow-up period of 81 months. With both SLA and SLActive implants, successful clinical results could be achieved up to 6.5 years of follow-up period.

  2. Characterization of wear debris from metal-on-metal hip implants during normal wear versus edge-loading conditions.

    Science.gov (United States)

    Kovochich, Michael; Fung, Ernest S; Donovan, Ellen; Unice, Kenneth M; Paustenbach, Dennis J; Finley, Brent L

    2018-04-01

    Advantages of second-generation metal-on-metal (MoM) hip implants include low volumetric wear rates and the release of nanosized wear particles that are chemically inert and readily cleared from local tissue. In some patients, edge loading conditions occur, which result in higher volumetric wear. The objective of this study was to characterize the size, morphology, and chemistry of wear particles released from MoM hip implants during normal (40° angle) and edge-loading (65° angle with microseparation) conditions. The mean primary particle size by volume under normal wear was 35 nm (range: 9-152 nm) compared with 95 nm (range: 6-573 nm) under edge-loading conditions. Hydrodynamic diameter analysis by volume showed that particles from normal wear were in the nano- (edge-loading conditions generated particles that ranged from Edge-loading conditions generated more elongated particles (4.5%) (aspect ratio ≥ 2.5) and more CoCr alloy particles (9.3%) compared with normal wear conditions (1.3% CoCr particles). By total mass, edge-loading particles contained approximately 640-fold more cobalt than normal wear particles. Our findings suggest that high wear conditions are a potential risk factor for adverse local tissue effects in MoM patients who experience edge loading. This study is the first to characterize both the physical and chemical characteristics of MoM wear particles collected under normal and edge-loading conditions. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 986-996, 2018. © 2017 Wiley Periodicals, Inc.

  3. Determination of residual load-bearing capacity of concrete beams at the operation stage by the strength reinforcement and concrete criterion

    OpenAIRE

    V.S. Utkin

    2015-01-01

    An experimental theoretical method was considered for estimating the residual load-bearing capacity of an individual reinforced concrete beam at the operational stage according to the criteria of the working strength and durability of concrete reinforcement compressed zone of the beam. Integrated methods of beam testing and probabilistic methods of random variables definition were used. Ultimate load in the form of interval during the operational phase was accepted as the measure of carr...

  4. Biomechanics and load resistance of small-diameter and mini dental implants: a review of literature.

    Science.gov (United States)

    Hasan, Istabrak; Bourauel, Christoph; Mundt, Torsten; Stark, Helmut; Heinemann, Friedhelm

    2014-02-01

    In recent years, the application of small-diameter and mini dental implants to support removable and fixed prosthesis has dramatically increased. However, the success of these implants under functional biting forces and the reaction of the bone around them need to be analyzed. This review was aimed to present studies that deal with the fatigue life of small-diameter and mini dental implants under normal biting force, and their survival rate. The numerical and experimental studies concluded that an increase in the risk of bone damage or implant failure may be assumed in critical clinical situations and implants with <3 mm diameter have a risk of fracture in clinical practice. The survival rate of the small-diameter and mini dental implants over 5 years was 98.3-99.4%.

  5. Dynamic analysis of double-row self-aligning ball bearings due to applied loads, internal clearance, surface waviness and number of balls

    Science.gov (United States)

    Zhuo, Yaobin; Zhou, Xiaojun; Yang, Chenlong

    2014-11-01

    In this paper, a three degrees of freedom (dof) model was established for a double-row self-aligning ball bearing (SABB) system, and was applied to study the dynamic behavior of the system during starting process and constant speed rotating process. A mathematical model was developed concerning stiffness and damping characteristics of the bearing, as well as three-dimensional applied load, rotor centrifugal force, etc. Balls and races were all considered as nonlinear springs, and the contact force between ball and race was calculated based on classic Hertzian elastic contact deformation theory and deformation compatibility theory. The changes of each ball's contact force and loaded angle of each row were taken into account. In order to solve the nonlinear dynamical equilibrium equations of the system, these equations were rewritten as differential equations and the fourth order Runge-Kutta method was used to solve the equations iteratively. In order to verify accuracy of the dynamical model and correctness of the numerical solution method, a kind of SABB-BRF30 was chosen for case studies. The effects of several important governing parameters, such as radial and axial applied loads, normal internal, inner and outer races waviness, and number of balls were investigated. These parametric studies led to a complete characterization of the shaft-bearing system vibration transmission. The research provided a theoretical reference for new type bearing design, shaft-bearing system kinetic analysis, optimal design, etc.

  6. Development of model hydroxyapatite bone scaffolds with multiscale porosity for potential load bearing applications

    Science.gov (United States)

    Dellinger, Jennifer Gwynne

    2005-11-01

    Model hydroxyapatite (HA) bone scaffolds consisting of a latticed pattern of rods were fabricated by a solid freeform fabrication (SFF) technique based on the robotic deposition of colloidal pastes. An optimal HA paste formulation for this method was developed. Local porosity, i.e. microporosity (1--30 mum) and sintering porosity (less than 1 mum), were produced by including polymer microsphere porogens in the HA pastes and by controlling the sintering of the scaffolds. Scaffolds with and without local porosity were evaluated with and without in vitro accelerated degradation. Percent weight loss of the scaffolds and calcium and phosphorus concentrations in solution increased with degradation time. After degradation, compressive strength and modulus decreased significantly for scaffolds with local porosity, but did not change significantly for scaffolds without local porosity. The compressive strength and modulus of scaffolds without local porosity were comparable to human cortical bone and were significantly greater than the scaffolds with local porosity. Micropores in HA disks caused surface pits that increased the surface roughness as compared to non-microporous HA disks. Mouse mesenchymal stem cells extended their cell processes into these microporous pits on HA disks in vitro. ALP expression was prolonged, cell attachment strength increased, and ECM production appeared greater on microporous HA disks compared to non-microporous HA disks and tissue culture treated polystyrene controls. Scaffolds with and without microporosity were implanted in goats bones. Microporous scaffolds with rhBMP-2 increased the percent of the scaffold filled with bone tissue compared to microporous scaffolds without rhBMP-2. Lamellar bone inside scaffolds was aligned near the rods junctions whereas lamellar bone was aligned in a more random configuration away from the rod junctions. Microporous scaffolds stained darkly with toluidine blue beneath areas of contact with new bone. This

  7. Survival rates and bone loss after immediate loading of implants in fresh extraction sockets (single gaps). A clinical prospective study with 4 year follow-up

    Science.gov (United States)

    Wojtovicz, Eduardo; España-Lopez, Antonio; Jimenez-Guerra, Alvaro; Monsalve-Guil, Loreto; Ortiz-Garcia, Ivan; Serrera-Figallo, Maria-Angeles

    2018-01-01

    Background The aim of this prospective study was to report the outcome of treatment with implants inserted after tooth extraction and immediately loaded. Material and Methods Fifty-six patients with single tooth loss were treated with 116 IPX Galimplant® implants with internal connections and a sandblasted, acid-etched surface. All implants were placed after tooth extraction using a flapless approach without bone regeneration, and they were then immediately loaded with cemented acrylic prostheses. After a period of three months, definitive cemented ceramic prostheses were placed. Patients were examined throughout a total of 4 years of follow-up. Marginal bone loss and survival rates were evaluated using digital periapical radiographs, taking into account clinical variables such as age, gender, smoking, history of periodontitis, etiology of extraction, placement site, diameter, and implant length. The Mann-Whitney U and Kruskal-Wallis non-parametric tests were used to compare differences between subgroups created based on the different clinical variables identified. Results Clinical results indicate an implant survival and success rate of 97.4%. Three implants were lost. Of the 116 immediate acrylic single crowns initially placed, 113 were replaced with definitive ceramic crowns after 3 months. A total of 77.8% of implants were inserted in the maxilla, while 22.2% were inserted in the mandible. No further complications were reported after the follow-up period (4 years). The mean marginal bone loss was 0.67 mm ± 0.40 mm. No differences were found among the subgroups of study patients. Conclusions This study indicates that dental implants that are inserted after tooth extraction and immediately loaded may constitute a successful and predictable alternative implant treatment. Key words:Dental implants, post-extraction implants, fresh sockets, immediate loading, immediate prostheses, implant dentistry. PMID:29476669

  8. Immediate loading of mandibular overdentures supported by one-piece, direct metal laser sintering mini-implants: a short-term prospective clinical study.

    Science.gov (United States)

    Mangano, Francesco G; Caprioglio, Alberto; Levrini, Luca; Farronato, Davide; Zecca, Piero A; Mangano, Carlo

    2015-02-01

    Only a few studies have dealt with immediately loaded, unsplinted mini-implants supporting ball attachment-retained mandibular overdentures (ODs). The aim of this study is to evaluate treatment outcomes of ball attachment-retained mandibular ODs supported by one-piece, unsplinted, immediately loaded, direct metal laser sintering (DMLS) mini-implants. Over a 4-year period (2009 to 2012), all patients referred to the Dental Clinic, University of Varese, and to a private practice for treatment with mandibular ODs were considered for inclusion in this study. Each patient received three or four DMLS mini-implants. Immediately after implant placement, a mandibular OD was connected to the implants. At each annual follow-up session, clinical and radiographic parameters were assessed, including the following outcome measures: 1) implant failures; 2) peri-implant marginal bone loss; and 3) complications. Statistical analysis was conducted using a life-table analysis. A total of 231 one-piece DMLS mini-implants were inserted in 62 patients. After 4 years of loading, six implants failed, giving an overall cumulative survival rate of 96.9%. The mean distance between the implant shoulder and the first visible bone-to-implant contact was 0.38 ± 0.25 and 0.62 ± 0.20 mm at the 1- and 4-year follow-up examinations, respectively. An incidence of 6.0% of biologic complications was reported; prosthetic complications were more frequent (12.9%). Within the limits of this study, it can be concluded that the immediate loading of one-piece, unsplinted, DMLS titanium mini-implants by means of ball attachment-supported mandibular ODs is a successful treatment procedure. Long-term follow-up studies are needed to confirm these results.

  9. Biological in situ Dose Painting for Image-Guided Radiation Therapy Using Drug-Loaded Implantable Devices

    International Nuclear Information System (INIS)

    Cormack, Robert A.; Sridhar, Srinivas; Suh, W. Warren; D'Amico, Anthony V.; Makrigiorgos, G. Mike

    2010-01-01

    Purpose: Implantable devices routinely used for increasing spatial accuracy in modern image-guided radiation treatments (IGRT), such as fiducials or brachytherapy spacers, encompass the potential for in situ release of biologically active drugs, providing an opportunity to enhance the therapeutic ratio. We model this new approach for two types of treatment. Methods and Materials: Radiopaque fiducials used in IGRT, or prostate brachytherapy spacers ('eluters'), were assumed to be loaded with radiosensitizer for in situ drug slow release. An analytic function describing the concentration of radiosensitizer versus distance from eluters, depending on diffusion-elimination properties of the drug in tissue, was developed. Tumor coverage by the drug was modeled for tumors typical of lung stereotactic body radiation therapy treatments for various eluter dimensions and drug properties. Six prostate 125 I brachytherapy cases were analyzed by assuming implantation of drug-loaded spacers. Radiosensitizer-induced subvolume boost was simulated from which biologically effective doses for typical radiosensitizers were calculated in one example. Results: Drug distributions from three-dimensional arrangements of drug eluters versus eluter size and drug properties were tabulated. Four radiosensitizer-loaded fiducials provide adequate radiosensitization for ∼4-cm-diameter lung tumors, thus potentially boosting biologically equivalent doses in centrally located stereotactic body treated lesions. Similarly, multiple drug-loaded spacers provide prostate brachytherapy with flexible shaping of 'biologically equivalent doses' to fit requirements difficult to meet by using radiation alone, e.g., boosting a high-risk region juxtaposed to the urethra while respecting normal tissue tolerance of both the urethra and the rectum. Conclusions: Drug loading of implantable devices routinely used in IGRT provides new opportunities for therapy modulation via biological in situ dose painting.

  10. A 5-year comparison of marginal bone level following immediate loading of single-tooth implants placed in healed alveolar ridges and extraction sockets in the maxilla

    Science.gov (United States)

    Berberi, Antoine N.; Sabbagh, Joseph M.; Aboushelib, Moustafa N.; Noujeim, Ziad F.; Salameh, Ziad A.

    2014-01-01

    Purpose: The aim of present investigation was to evaluate marginal bone level after 5-year follow-up of implants placed in healed ridges and fresh extraction sockets in maxilla with immediate loading protocol. Materials and Methods: Thirty-six patients in need of a single-tooth replacement in the anterior maxilla received 42 Astra Tech implants (Astra Tech Implant system™, Dentsply Implants, Mölndal, Sweden). Implants were placed either in healed ridges (group I) or immediately into fresh extraction sockets (group II). Implants were restored and placed into functional loading immediately by using a prefabricated abutment. Marginal bone level relative to the implant reference point was recorded at implant placement, crown cementation, 12, 36, and 60 months following loading using intra-oral radiographs. Measurements were made on the mesial and distal sides of each implant. Results: Overall, two implants were lost from the group II, before final crown cementation: they were excluded from the study. The mean change in marginal bone loss (MBL) after implant placement was 0.26 ± 0.161 mm for 1 year, and 0.26 ± 0.171 mm for 3 years, and 0.21 ± 0.185 mm for 5 years in extraction sockets and was 0.26 ± 0.176 mm for 1 year and 0.21 ± 0.175 mm for 3 years, and 0.19 ± 0.172 mm for 5 years in healed ridges group. Significant reduction of marginal bone was more pronounced in implants inserted in healed ridges (P prefabricated abutment placed during the surgery time seems to maintain marginal bone around implant in both healed and fresh extraction sites. PMID:24550840

  11. Clinical evaluation of immediate loading of electroeroded screw-retained titanium fixed prostheses supported by tilted implant: a multicenter retrospective study.

    Science.gov (United States)

    Acocella, Alessandro; Ercoli, Carlo; Geminiani, Alessandro; Feng, Changyong; Billi, Mauro; Acocella, Gabriele; Giannini, Domenico; Sacco, Roberto

    2012-05-01

    Immediate occlusal loading of dental implants in the edentulous mandible has proven to be an effective, reliable, and predictable treatment protocol. However, there is limited long-term data available in the literature, when an electroeroded definitive cast-titanium fixed prosthesis is used for this treatment protocol. The aim of this study was to evaluate the clinical effectiveness of dental implants (Astra Tech Dental, Mölndal, Sweden) in the edentulous mandible immediately loaded with an electroeroded cast-titanium screw-retained fixed prosthesis. Forty-five patients received five implants each in the interforaminal area. All the implants were inserted with torque up to 40 Ncm and the distal implants were distally tilted approximately 20 to 30 degrees to minimize the length of posterior cantilevers. Implants were loaded within 48 hours of placement with an acrylic resin-titanium screw-retained prosthesis fabricated by electroerosion. Two of the 225 inserted implants failed after 3 and 16 months of healing, respectively, with a cumulative survival rate of 99.1% and a prosthetic survival rate of 97.8%. Immediate loading of tilted dental implants inserted in the edentulous mandible with a screw-retained titanium definitive prosthesis fabricated with electrical discharge machining provide reliable and predictable results. © 2011 Wiley Periodicals, Inc.

  12. Finite element analysis of dental implant loading on atrophic and non-atrophic cancellous and cortical mandibular bone - a feasibility study

    NARCIS (Netherlands)

    Marcián, P.; Borák, L.; Valášek, J.; Kaiser, J.; Florian, Z.; Wolff, J.

    2014-01-01

    The first aim of this study was to assess displacements and micro-strain induced on different grades of atrophic cortical and trabecular mandibular bone by axially loaded dental implants using finite element analysis (FEA). The second aim was to assess the micro-strain induced by different implant

  13. Finite element analysis of dental implant loading on atrophic and non-atrophic cancellous and cortical mandibular bone – a feasibility study

    NARCIS (Netherlands)

    Marcian, P.; Borak, L.; Valasek, J.; Kaiser, J.; Florian, Z.; Wolff, J.E.H.

    2014-01-01

    The first aim of this study was to assess displacements and micro-strain induced on different grades of atrophic cortical and trabecular mandibular bone by axially loaded dental implants using finite element analysis (FEA). The second aim was to assess the micro-strain induced by different implant

  14. A tissue engineering solution for segmental defect regeneration in load-bearing long bones.

    Science.gov (United States)

    Reichert, Johannes C; Cipitria, Amaia; Epari, Devakara R; Saifzadeh, Siamak; Krishnakanth, Pushpanjali; Berner, Arne; Woodruff, Maria A; Schell, Hanna; Mehta, Manav; Schuetz, Michael A; Duda, Georg N; Hutmacher, Dietmar W

    2012-07-04

    The reconstruction of large defects (>10 mm) in humans usually relies on bone graft transplantation. Limiting factors include availability of graft material, comorbidity, and insufficient integration into the damaged bone. We compare the gold standard autograft with biodegradable composite scaffolds consisting of medical-grade polycaprolactone and tricalcium phosphate combined with autologous bone marrow-derived mesenchymal stem cells (MSCs) or recombinant human bone morphogenetic protein 7 (rhBMP-7). Critical-sized defects in sheep--a model closely resembling human bone formation and structure--were treated with autograft, rhBMP-7, or MSCs. Bridging was observed within 3 months for both the autograft and the rhBMP-7 treatment. After 12 months, biomechanical analysis and microcomputed tomography imaging showed significantly greater bone formation and superior strength for the biomaterial scaffolds loaded with rhBMP-7 compared to the autograft. Axial bone distribution was greater at the interfaces. With rhBMP-7, at 3 months, the radial bone distribution within the scaffolds was homogeneous. At 12 months, however, significantly more bone was found in the scaffold architecture, indicating bone remodeling. Scaffolds alone or with MSC inclusion did not induce levels of bone formation comparable to those of the autograft and rhBMP-7 groups. Applied clinically, this approach using rhBMP-7 could overcome autograft-associated limitations.

  15. The Effect of Consolidation on TBM Shield Loading in Water-Bearing Squeezing Ground

    Science.gov (United States)

    Ramoni, M.; Anagnostou, G.

    2011-01-01

    Jamming or overstressing of the shield due to ground pressure are potential problems for tunnel boring machine (TBM) tunnelling in squeezing ground. The risk of shield jamming depends essentially on the deformation rate of the ground in the vicinity of the working face. The time-dependency of the ground response to the excavation is associated with its rheological properties as well as with the transient consolidation process that takes place around the opening in the case of a low-permeability saturated ground. The present paper focuses on the second mechanism and investigates the interaction between the advancing shield, tunnel lining and consolidating ground by means of transient numerical analyses. For a given set of geotechnical conditions and a given TBM configuration, the load exerted by the ground upon the shield during TBM operation decreases with increasing gross advance rate. During a long break in operations, the ground pressure may increase significantly, thereby necessitating a higher thrust force to overcome shield skin friction and restart the TBM. It is interesting to note that a high advance rate reduces the risk of shield jamming not only during TBM advance, but is also favourable with respect to any subsequent long standstills.

  16. Calculation of load-bearing capacity of prestressed reinforced concrete trusses by the finite element method

    Science.gov (United States)

    Agapov, Vladimir; Golovanov, Roman; Aidemirov, Kurban

    2017-10-01

    The technique of calculation of prestressed reinforced concrete trusses with taking into account geometrical and physical nonlinearity is considered. As a tool for solving the problem, the finite element method has been chosen. Basic design equations and methods for their solution are given. It is assumed that there are both a prestressed and nonprestressed reinforcement in the bars of the trusses. The prestress is modeled by setting the temperature effect on the reinforcement. The ways of taking into account the physical and geometrical nonlinearity for bars of reinforced concrete trusses are considered. An example of the analysis of a flat truss is given and the behavior of the truss on various stages of its loading up to destruction is analyzed. A program for the analysis of flat and spatial concrete trusses taking into account the nonlinear deformation is developed. The program is adapted to the computational complex PRINS. As a part of this complex it is available to a wide range of engineering, scientific and technical workers

  17. Randomized controlled multicenter study comparing short dental implants (6 mm) versus longer dental implants (11-15 mm) in combination with sinus floor elevation procedures. Part 2: clinical and radiographic outcomes at 1 year of loading.

    Science.gov (United States)

    Schincaglia, Gian Pietro; Thoma, Daniel S; Haas, Robert; Tutak, Marcin; Garcia, Abel; Taylor, Thomas D; Hämmerle, Christoph H F

    2015-11-01

    To compare, clinically and radiographically, short dental implants (6 mm) to long implants (11-15 mm) placed with sinus grafting. Participants with 5-7 mm of bone height in the posterior maxilla were randomly allocated to receive short implants (GS) or long implants with sinus grafting (GG). Implants were loaded with single crowns 6 months after placement (PR). Patients were re-evaluated 12 months after loading (FU-1). Outcome variables included: Implant survival rate (CSR), marginal bone level alteration (MBL), periodontal probing depth (PPD), bleeding on probing (BoP), plaque control record (PCR) and crown-to-implant ratios (C/I). Statistical analysis was performed using parametric tests. In 97 subjects, 132 implants were re-evaluated at FU-1. The CSR was 100%. The MBL from implant placement (IP) to (PR) was -0.22 ± 0.4 mm for GG and -0.3 ± 0.45 mm for GS (p 0.05), PPD (p = 1) and PCR (p = 0.09). BoP was higher in the GS (p = 0.04). The C/I was 0.99 ± 0.17 for GG and 1.86 ± 0.23 for GS (p < 0.001). No correlation was observed between C/I and MBL, (GG: p = 0.13; GS: p = 0.38). Both treatment modalities provided similar outcomes. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  18. Optimization in multi-implant placement for immediate loading in edentulous arches using a modified surgical template and prototyping: a case report.

    Science.gov (United States)

    Jayme, Sérgio J; Muglia, Valdir A; de Oliveira, Rafael R; Novaes, Arthur B Júnior

    2008-01-01

    Immediate loading of dental implants shortens the treatment time and makes it possible to give the patient an esthetic appearance throughout the treatment period. Placement of dental implants requires precise planning that accounts for anatomic limitations and restorative goals. Diagnosis can be made with the assistance of computerized tomographic scanning, but transfer of planning to the surgical field is limited. Recently, novel CAD/CAM techniques such as stereolithographic rapid prototyping have been developed to build surgical guides in an attempt to improve precision of implant placement. The aim of this case report was to show a modified surgical template used throughout implant placement as an alternative to a conventional surgical guide.

  19. Effect of a self-adhesive coating on the load-bearing capacity of tooth-coloured restorative materials.

    Science.gov (United States)

    Bagheri, R; Palamara, Jea; Mese, A; Manton, D J

    2017-03-01

    The aim of this study was to compare the flexural strength and Vickers hardness of tooth-coloured restorative materials with and without applying a self-adhesive coating for up to 6 months. Specimens were prepared from three resin composites (RC), two resin-modified glass-ionomer cements (RM-GIC) and two conventional glass-ionomer cements (CGIC). All materials were tested both with and without applying G-Coat Plus (GCP). Specimens were conditioned in 37 °C distilled deionized water for 24 h, and 1, 3 and 6 months. The specimens were strength tested using a four-point bend test jig in a universal testing machine. The broken specimen's halves were used for Vickers hardness testing. Representative specimens were examined under an environmental scanning electron microscope. Data analysis showed that regardless of time and materials, generally the surface coating was associated with a significant increase in the flexural strength of the materials. Applying the GCP decreased the hardness of almost all materials significantly (P < 0.05) and effect of time intervals on hardness was material dependent. The load-bearing capacity of the restorative materials was affected by applying self-adhesive coating and ageing. The CGIC had significantly higher hardness but lower flexural strength than the RM-GIC and RC. © 2016 Australian Dental Association.

  20. Empirical study of the perceived ease of use and relative advantage on load-bearing masonry (LBM) technology adoption

    Science.gov (United States)

    Ramli, Nor Azlinda; Abdullah, Che Sobry; Nawi, Mohd Nasrun Mohd

    2017-11-01

    Load-bearing masonry (LBM) technology has been identified as an alternative method that can potentially encourage the sustainability of the housing industry. The adoption of LBM technology is believed to bring beneficial effects to the housing industry as well as company productivity. The factors related to the adoption LBM technology was revealed to strongly influence the implementation of this system in the housing industry. The aim of this study is to determine the factors influencing the adoption of LBM technology among the developer firms in Malaysia as well as the factors that are highly related to perceived ease of use and relative advantage. A random sampling technique was applied and a questionnaire-based field survey was carried out to obtain the data from the respondents. All the data were analyzed using Partial Least Squares Structural Equation Modeling (PLS-SEM). The findings of this paper have revealed that perceived ease of use and relative advantage are related to the adoption of LBM technology. The findings also indicated the validity of Technology Acceptance Model TAM (perceived ease of use) and Innovation Diffusion Theory IDT (relative advantage) as the determinant factors in the adoption of LBM technology. Finally, some recommendations for future research are suggested in the final section of this paper.

  1. Evaluation of ultimate load bearing capacity of the primary containment of a typical first generation 220 MWe Indian PHWRs

    International Nuclear Information System (INIS)

    Singh, A.K.; Ray, I.; Roy, R.; Garg, R.P.; Verma, U.S.P.

    2005-01-01

    This paper presents the analysis of the Inner Containment Structure (ICS) of a typical first generation 220 MWe Indian PHWR for the purpose of evaluating its ultimate load bearing capacity (ULBC) beyond postulated design basis accident (DBA) scenario. The first generation ICS of Indian PHWRs are made of cylindrical wall capped with prestressed/reinforced cellular containment slab, which is connected monolithically to outer containment (OC) Wall to provide clamping effect during postulated DBA scenario. This paper discusses the simulation of construction sequence in analytical model, which is a very important aspect from point of view of capturing the residual stresses generated in the structure. The methodology adopted for the non-linear analysis of the prestressed concrete ICS including the various issues, viz. behaviour of concrete under compression and tension, tension stiffening, cracked shear modulus etc. have also been discussed in this paper. The effect of accident temperature on ULBC has been studied and discussed in this paper. This paper also discusses the study of mesh sensitivity of the finite element (FE) discretisation on ULBC of ICS in the non-linear range. Based on the detailed analysis, the factor of safety of the ICS beyond postulated DBA scenario has been evaluated. (authors)

  2. A Novel Inversion Method of Manufacturing Flaws in the Packaging of Conformal Load-Bearing Antenna Structure

    Directory of Open Access Journals (Sweden)

    P. Li

    2015-01-01

    Full Text Available Composite material is widely used in the conformal load-bearing antenna structure (CLAS, and the manufacturing flaws in the packaging process of the CLAS will lead to the degradation of its wave-transparent property. For this problem, a novel inverse method of the flaw’s dimension by antenna-radome system’s far field data has been proposed. Two steps are included in the inversion: the first one is the inversion from the far filed data to the transmission coefficient of the CLAS’s radome; the second one is the inversion from the transmission coefficient to the flaw’s dimension. The inversion also has a good potential for the separable multilayer composite material radome. A 12.5 GHz CLAS with microstrip antenna array is used in the simulation, which indicates the effectiveness of the novel inversion method. Finally, the error analysis of the inversion method is presented by numerical simulation; the results is that the inversed error could be less than 10%, if the measurement error of far field data is less than 0.45 dB in amplitude and ±5° in phase.

  3. In situ epicatechin-loaded hydrogel implants for local drug delivery ...

    African Journals Online (AJOL)

    induce apoptosis and cell cycle arrest in a wide array of cell lines, and protect ... attenuated ischaemic brain injury and inhibition ..... biodegradable smart implants for tissue regeneration after spinal ... Synthetic hydrogels for controlled stem cell.

  4. A Randomized Case-Series Study Comparing the Stability of Implant with Two Different Surfaces Placed in Fresh Extraction Sockets and Immediately Loaded

    Science.gov (United States)

    Vanden Bogaerde, Leonardo; Sennerby, Lars

    2016-01-01

    Background. Hydrophilic and moderately rough implant surfaces have been proposed to enhance the osseointegration response. Aim. The aim of this study was to compare early changes of stability for two implants with identical macrodesign but with different surface topographies. Materials and Methods. In 11 patients, a total of 22 implants (11 bimodal (minimally rough, control) and 11 proactive (moderately rough and hydrophilic, test), Neoss Ltd., Harrogate, UK) were immediately placed into fresh extraction sockets and immediately loaded. The peak insertion torque (IT) was measured in Ncm at placement. Resonance Frequency Analysis (RFA) measurements were made at baseline and 2, 4, 6, and 12 weeks after surgery. Results. The two implant types showed similar IT and RFA values at placement (NS). A dip of RFA values after 2 weeks followed by an increase was observed, where the test implant showed a less pronounced decrease and a more rapid recovery than the control implant. The test implants were significantly more stable than the control ones after 12 weeks. Conclusions. The results from the present study indicated that the hydrophilic and rougher test implant was more resistant to immediate loading and showed a significantly higher stability than the smoother control implant after 12 weeks. PMID:27042180

  5. Resonance frequency analysis of thermal acid-etched, hydrophilic implants during first 3 months of healing and osseointegration in an early-loading protocol

    NARCIS (Netherlands)

    van Eekeren, P.; Said, C.; Tahmaseb, A.; Wismeijer, D.

    2015-01-01

    Purpose: Safe loading of dental implants requires an optimal osseointegration. This osseointegration process during healing could be analyzed by resonance frequency analysis (RFA). The purpose of the study was to evaluate RFA changes during healing in splinted, early-loaded, thermal acid-etched,

  6. In vivo evaluation of an antibacterial coating containing halogenated furanone compound-loaded poly(l-lactic acid) nanoparticles on microarc-oxidized titanium implants.

    Science.gov (United States)

    Cheng, Yicheng; Gao, Bo; Liu, Xianghui; Zhao, Xianghui; Sun, Weige; Ren, Huifang; Wu, Jiang

    2016-01-01

    To prevent peri-implant infection, a new antibacterial coating containing a halogenated furanone compound, (Z-)-4-bromo-5-(bromomethylene)-2(5H)-furanone-loaded poly(l-lactic acid) nanoparticles, has been fabricated. The current study was designed to evaluate the preventive effect of the antibacterial coating under a simulated environment of peri-implant infection in vivo. Microarc-oxidized titanium implants treated with minocycline hydrochloride ointment were used as positive control group, and microarc-oxidized titanium implants without any treatment were used as blank control group. Three kinds of implants were implanted in dogs' mandibles, and the peri-implant infection was simulated by silk ligation and feeding high sugar diet. After 2-month implantation, the results showed that no significant differences were detected between the experimental and positive control groups (P>0.05), but the data of clinical measurements of the blank control group were significantly higher than those of the other two groups (Pmicroscope observation and histological examination showed that more new bone was formed on the surface of the experimental and positive control groups. It can be concluded that the antibacterial coating fabricated on implants has remarkable preventive effect on peri-implant infection at the early stage.

  7. Botulinum Toxin Type A as Preoperative Treatment for Immediately Loaded Dental Implants Placed in Fresh Extraction Sockets for Full-Arch Restoration of Patients With Bruxism.

    Science.gov (United States)

    Mijiritsky, Eitan; Mortellaro, Carmen; Rudberg, Omri; Fahn, Miri; Basegmez, Cansu; Levin, Liran

    2016-05-01

    The aim of the present report was to describe the use of Botulinum toxin type A as preoperative treatment for immediately loaded dental implants placed in fresh extraction sockets for full-arch restoration of patients with bruxism. Patients with bruxism who were scheduled to receive immediately loaded full-arch implant supported fixed restorations were included in this retrospective clinical report. To reduce the occlusal forces applied in patients with bruxism, Botulinum toxin type A was introduced prior to the implant placement procedure. Patients were followed and implant survival as well as peri-implant bone level was assessed in each periodic follow-up visit. Adverse effects were also recorded. A control group with no use of Botulinum toxin was evaluated as well. A total of 26 patients (13 test and 13 control), with bruxism, aged 59.15 ± 11.43 years on average were included in this retrospective report and received immediately loaded dental implants placed in fresh extraction sockets for full-arch restoration. The test group treatment preceded by Botulinum toxin type A injection. Maxillary arches were supported by 8 to 10 implants while the mandibular arch was supported by 6 implants. All surgeries went uneventfully and no adverse effects were observed. The average follow-up time was 32.5 ± 10.4 months (range, 18-51). In the test group, no implant failures were recorded. One patient presented with 1 to 2 mm bone loss around 4 of the implants; the other implants presented with stable bone level. In the control group 1 patient lost 2 implants and another demonstrated 2 mm bone loss around 3 of the implants. The preoperative use of Botulinum toxin in patients with bruxism undergoing full-arch rehabilitation using immediately loaded dental implants placed in fresh extraction sockets seems to be a technique that deserves attention. Further long-term, large-scale randomized clinical trials will help to determine the additional benefit of this suggested

  8. Predicting the service life of connecting rod and main bearings, taking into account different engine loads. Final report; Lebensdauervorhersage fuer Pleuel- und Hauptlager unter Beruecksichtigung unterschiedlicher Motorlastkollektive. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Berkowitz, B.; Lueneburg, B.; Liu, J.

    1994-12-31

    Connecting rod and main bearings of internal combustion engines are among the most heavily stressed components in modern engines. It was found that these engine components are increasingly reaching the limits of their strength and therefore become the components limiting engine life. However, there is no known process which makes a calculated prediction of the service life of modern connecting rod and main bearings possible, taking into account various engine loads. In this research project, a new concept for the calculated prediction of the service life of non-static highly loaded radial sliding bearings is worked out. The basis is a process of calculation which realistically determines the pressure and gap course in highly loaded sliding bearings. Apart from the viscosity depending on pressure and temperature, the elastic deformations of the system sliding bearing/conn rod are also taken into account. Calculations are done for different operating points for a complete cycle of a four stroke Diesel engine (Daimler-Benz OM 364 LA). The results are compared with the present conventional process of calculation and the effects which occur are discussed. Based on the elasto-hydrodynamic calculation, a method of calculating the service life of non-statically loaded sliding bearings, taking into account various motor loads, is worked out. (orig./HW) [Deutsch] Pleuel- und Hauptlager von Verbrennungskraftmaschinen zaehlen mit zu den spezifisch am hoechsten beanspruchten Bauteilen in modernen Motoren. Es hat sich gezeigt, dass vor allem diese Maschinenelemente zunehmend an die Grenzen ihrer Belastbarkeit stossen und so zum lebensdauerbegrenzenden Bauteil werden. Es ist jedoch kein Verfahren bekannt, das eine rechnerische Lebensdauervorhersage moderner Pleuel- und Hauptlager unter Beruecksichtigung unterschiedlicher Motorlastkollektive ermoeglicht. Im vorliegenden Forschungsvorhaben wird daher ein neuartiges Konzept zur rechnerischen Lebensdauervorhersage von instationaeren

  9. LIGHT-WEIGHT LOAD-BEARING STRUCTURES REINFORCED BY CORE ELEMENTS MADE OF SEGMENTS AND A METHOD OF CASTING SUCH STRUCTURES

    DEFF Research Database (Denmark)

    2009-01-01

    The invention relates to a light-weight load-bearing structure, reinforced by core elements (2) of a strong material constituting one or more compression or tension zones in the structure to be cast, which core (2) is surrounded by or adjacent to a material of less strength compared to the core (2......), where the core (2) is constructed from segments (1) of core elements (2) assembled by means of one or more prestressing elements (4). The invention further relates to a method of casting of light-weight load-bearing structures, reinforced by core elements (2) of a strong material constituting one...... or more compression or tension zones in the structure to be cast, which core (2) is surrounded by or adjacent to a material of less strength compared to the core (2), where the core (2) is constructed from segments (1) of core elements (2) assembled and hold together by means of one or more prestressing...

  10. Sinus Floor Elevation with Modified Crestal Approach and Single Loaded Short Implants: A Case Report with 4 Years of Follow-Up

    Directory of Open Access Journals (Sweden)

    Michele Perelli

    2017-01-01

    Full Text Available Tooth extraction is usually followed by bone reduction. In the maxillary posterior region, this remodelling combined with sinus pneumatisation and periodontal defects may lead to a reduced basal bone height available for implant placement. Sinus floor elevation can be performed with different surgical techniques. Crestal approach has demonstrated to be effective, less invasive, and associated with a reduced morbidity. This article reports a modified sinus floor elevation by means of rotary, noncutting instruments, addition of xenograft, and 2 short-threaded implant placements. The aim of the study was to evaluate the implant’s success and intrasinus radiographical bone gain after 4 years of functional loading. The premolar implant site presented a starting basal bone height of 6 mm, while the molar site was of 2 mm. In the first surgical step, sinus floor elevation was performed mesially and the implant was inserted, and distally only sinus floor elevation was performed. After 6 months, the mesial implant was uncovered and the second implant was inserted; 4 months later, the second fixture was uncovered, and both fixtures were loaded with single provisional screw-retained crowns and later with single screw-retained porcelain fused to metal crowns. Implants integrated successfully, and crestal bone remodelling did not exceed the smooth collar. Bone gain was 3 mm for the mesial implant and more than 5 mm for the distal one.

  11. Evaluation of Bernese periacetabular osteotomy: prospective studies examining projected load-bearing area, bone density, cartilage thickness and migration.

    Science.gov (United States)

    Mechlenburg, Inger

    2008-06-01

    The typical dysplastic hip joint is characterised by maldirection of the acetabulum and femoral neck, insufficient coverage of the femoral head focally and globally and erosions of the limbus acetabuli (1). An unknown number of persons with hip dysplasia will suffer from pain in hip or groin, decreased hip function and development of osteoarthritis at a young age. The Bernese periacetabular osteotomy is performed to prevent osteoarthritis in patients with hip dysplasia and has been carried out at Aarhus University Hospital, Denmark since 1996 with more than 500 osteotomies performed. Throughout the years, research and quality improvement of the treatment has taken place and this PhD thesis is part of that process. The aims of this PhD thesis were to evaluate outcome aspects after periacetabular osteotomy in terms of I) estimating the projected loadbearing surface before and after periacetabular osteotomy, II) estimating bone density changes in the acetabulum after periacetabular osteotomy, III) developing a technique to precisely and efficiently estimate the thickness of the articular cartilage in the hip joint and IV) examining the stability of the re-orientated acetabulum after periacetabular osteotomy. In study I, we applied a stereologic method based on 3D computed tomography (CT) to estimate the projected loadbearing surface in six normal hip joints and in six dysplastic hips. The dysplastic hips were CT scanned before and after periacetabular osteotomy. We found that the average area of the projected loadbearing surface of the femoral head preoperatively was 7.4 (range 6.5-8.4) cm2 and postoperatively 11 (9.8-14.3) cm2. The area of the projected loadbearing surface was increased significantly with a mean of 49% (34-70%) postoperatively and thus comparable with the load-bearing surface in the normal control group. Double measurements were performed and the error variance of the mean was estimated to be 1.6%. The effect of overprojection, on the projected

  12. Macroscopic and microscopic evaluation of a new implant design supporting immediately loaded full arch rehabilitation

    OpenAIRE

    Tetè, Stefano; Zizzari, Vincenzo; De Carlo, Alessandro; Sinjari, Bruna; Gherlone, Enrico

    2012-01-01

    The purpose of this study is to evaluate macroscopic and microscopic appearance of a new implant design, with particular emphasis given to the type of prosthesis connection. Two dental implants of the same type (Torque Type®, WinSix®, BioSAFin. S.r.l. - Ancona, Italy), with sandblasted and acid etched surfaces (Micro Rough Surface®), but differing from each other for the prosthesis connection system, were examined by scanning electron microscope (SEM) analysis at different magnifications: TTI...

  13. Gene expression of inflammation and bone healing in peri-implant crevicular fluid after placement and loading of dental implants. A kinetic clinical pilot study using quantitative real-time PCR.

    Science.gov (United States)

    Slotte, Christer; Lennerås, Maria; Göthberg, Catharina; Suska, Felicia; Zoric, Neven; Thomsen, Peter; Nannmark, Ulf

    2012-10-01

    Early detection of healing complications after placement of dental implants is a pressing but elusive goal. This paper proposes a non-invasive diagnostic tool for monitoring healing- and peri-implant disease specific genes, complementary to clinical evaluations. Eighteen partially edentulous patients were recruited to this pilot study. Three Brånemark TiUnite® implants/patient (Nobel Biocare) were placed in a one-stage procedure. Abutments with smooth or rough (TiUnite®) surface were placed. The test group (n = 9) received fixed bridges (immediate loading), whereas the control group (n = 9) implants were loaded 3 months after surgery. In addition to clinical measurements, crevicular fluid was collected using paper strips at the implant abutments 2, 14, 28, and 90 days postoperative. mRNA was extracted, purified, and converted to cDNA. Quantitative PCR assays for IL-1β, TNF-α, Osteocalcin (OC), Alkaline Phosphatase (ALP), Cathepsin K, Tartrate Resistant Acid Phosphatase, and 18S ribosomal RNA were designed and validated. Relative gene expression levels were calculated. One implant was lost in the control group and three in the test group. In one test patient, one implant showed lowered stability after 2 to 4 weeks and was unloaded. Later implant stability improved which allowed for loading after 3 to 4 months. TNF-α and ALP most commonly showed correlation with clinical parameters followed by IL-1β and OC. The strongest correlation was found for TNF-α with clinical complications at 2 and 14 days (p = .01/r = -048, and p = .0004/r = -0.56, respectively; test and control groups together). In some cases, gene expression predicted clinical complications (TNF-α, ALP, CK). This study is based on samples from few individuals; still, some genes showed correlation with clinical findings. Further studies are needed to refine and optimize the sampling process, to find the appropriate panel, and to validate gene expression for monitoring implant healing. © 2010 Wiley

  14. APPLICATION OF COMPUTER SIMULATION IN THE EVALUATION OF THE STRESS-STRAIN STATE OF LOAD-BEARING STRUCTURES OF BUILDINGS MASONRY

    Directory of Open Access Journals (Sweden)

    Anatoliy I. Bedov

    2017-03-01

    Full Text Available The results of studies on the analysis of the stress-strain state of the structures of bearing walls of high-hollow pottery. The way of modeling masonry finite element method. The experimental study of masonry structures produced in the Republic of Bashkortostan high-hollow pottery, set the nature of their work load, the mechanism of destruction. The results of the comparative evaluation of the calculations in the software package and the traditional “manual” calculation.

  15. Revival of pure titanium for dynamically loaded porous implants using additive manufacturing

    NARCIS (Netherlands)

    Wauthle, Ruben; Ahmadi, Seyed Mohammad; Amin Yavari, Saber; Mulier, Michiel; Zadpoor, Amir Abbas; Weinans, Harrie; Van Humbeeck, Jan; Kruth, Jean-Pierre; Schrooten, Jan

    Additive manufacturing techniques are getting more and more established as reliable methods for producing porous metal implants thanks to the almost full geometrical and mechanical control of the designed porous biomaterial. Today, Ti6Al4V ELI is still the most widely used material for porous

  16. Abutment-to-fixture load transfer and peri-implant bone stress

    NARCIS (Netherlands)

    van Oers, R.F.; Feilzer, A.J.

    2015-01-01

    Purpose: To uncover design principles for the abutment-fixture complex that reduce the stress concentration on the bone. Methods: A 3-dimensional finite element model was used to vary shape, elasticity, and connectivity of the abutment-fixture complex. We compared peri-implant bone stress of these

  17. Five-year outcome of a retrospective cohort study on the rehabilitation of completely edentulous atrophic maxillae with immediately loaded zygomatic implants placed extra-maxillary.

    Science.gov (United States)

    Maló, Paulo; Nobre, Miguel de Araújo; Lopes, Armando; Ferro, Ana; Moss, Steven

    2014-01-01

    implants was 1.16 mm (0.77 mm) in those 9 patients having the intraoral radiographs. The long term outcome (5 years) of rehabilitations performed on patients with completely edentulous, severely atrophic maxillae supported by immediately loaded zygomatic implants alone, or in combination with conventional implants, is satisfactory.

  18. A Systematic Review on Immediate Loading of Implants Used to Support Overdentures Opposed by Conventional Prostheses: Factors That Might Influence Clinical Outcomes.

    Science.gov (United States)

    Zygogiannis, Kostas; Wismeijer, Daniel; Aartman, Irene Ha; Osman, Reham B

    2016-01-01

    Different treatment protocols in terms of number, diameter, and suprastructure design have been proposed for immediately loaded implants that are used to support mandibular overdentures opposed by maxillary conventional dentures. The aim of this study was to investigate the influence of these protocols on survival rates as well as clinical and prosthodontic outcomes. Several electronic databases were searched for all relevant articles published from 1966 to June 2014. Only randomized controlled trials and prospective studies with a minimum follow-up of 12 months were selected. The primary outcomes of interest were the success and survival rates of the implants. Prosthodontic complications were also evaluated. Fourteen studies fulfilled the inclusion criteria. Of the studies identified, nine were randomized controlled trials and five were prospective studies. The mean follow-up period was 3 years or less for the vast majority of the studies. The reported survival and success rates were comparable to that of conventional loading for most of the included studies. No specific immediate loading protocol seemed to perform better in terms of clinical and prosthodontic outcomes. Immediate loading protocols of mandibular overdentures seem to be a viable alternative to conventional loading. It was not possible to recommend a specific treatment protocol related to the number, diameter of the implants, and attachment system used. Long-term, well-designed studies comparing different immediate loading modalities could help to establish a protocol that delivers the most clinically predictable, efficient, and cost-effective outcome for edentulous patients in need of implant overdentures.

  19. Circumferential bone loss around splinted and nonsplinted immediately loaded implants retaining mandibular overdentures: A randomized controlled clinical trial using cone beam computed tomography.

    Science.gov (United States)

    Elsyad, Moustafa Abdou; Khirallah, Ahmed Samir

    2016-11-01

    Circumferential marginal bone around 2 splinted and nonsplinted immediately loaded implants in the edentulous mandible has not been previously investigated. The purpose of this randomized controlled clinical trial was to assess circumferential bone loss around splinted and nonsplinted immediately loaded implants retaining mandibular overdentures, using cone beam computed tomography (CBCT). Thirty participants with complete edentulism were allocated to 2 groups and received 2 implants in the canine region of the mandible. Implants were either left nonsplinted (with ball attachment [BA]) or splinted (with bar attachment [RA]). Mandibular overdentures were connected to the implants 1 week later. CBCT was used to evaluate vertical bone loss (VBL) and horizontal bone loss (HBLo) bone loss at the distal (D), buccal (B), mesial (M), and lingual (L) sites of each implant upon overdenture insertion (baseline, T0), 1 year (T1) and 3 years (T3) after insertion. Repeated measures ANOVA was used for statistical analysis (α=.05). No significant difference in the survival rate (93.3% for BA and 100% for RA) was found between groups (P=.156). VBL and HBLo increased significantly at T3 compared with T1 for both groups (Poverdentures were associated with significantly higher vertical and horizontal circumferential bone loss than those associated with splinted implants after a follow-up of 3 years. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  20. Implant Restoration of Edentulous Jaws with 3D Software Planning, Guided Surgery, Immediate Loading, and CAD-CAM Full Arch Frameworks

    Directory of Open Access Journals (Sweden)

    Silvio Mario Meloni

    2013-01-01

    Full Text Available Purpose. The aim of this study was to analyze the clinical and radiographic outcomes of 23 edentulous jaws treated with 3D software planning, guided surgery, and immediate loading and restored with CAD-CAM full arch frameworks. Materials and Methods. This work was designed as a prospective case series clinical study. Twenty patients have been consecutively rehabilitated with an immediately loaded implant supported fixed full prosthesis. A total of 120 fixtures supporting 23 bridges were placed. 117 out of 120 implants were immediately loaded. Outcome measures were implants survival, radiographic marginal bone levels and remodeling, soft tissue parameters, and complications. Results. 114 of 117 implants reached a 30 months follow-up, and no patients dropped out from the study. The cumulative survival rate was 97.7%; after 30 months, mean marginal bone level was  mm, mean marginal bone remodeling value was , mean PPD value was  mm, and mean BOP value was 4% ± 2.8%. Only minor prosthetic complications were recorded. Conclusion. Within the limitations of this study, it can be concluded that computer-guided surgery and immediate loading seem to represent a viable option for the immediate rehabilitations of completely edentulous jaws with fixed implant supported restorations. This trial is registered with Clinicaltrials.gov NCT01866696.

  1. PlA polymorphism and platelet reactivity following clopidogrel loading dose in patients undergoing coronary stent implantation.

    Science.gov (United States)

    Angiolillo, Dominick J; Fernandez-Ortiz, Antonio; Bernardo, Esther; Alfonso, Fernando; Sabaté, Manel; Fernández, Cristina; Stranieri, Chiara; Trabetti, Elisabetta; Pignatti, Pier Franco; Macaya, Carlos

    2004-01-01

    The PlA polymorphism (Leu33Pro) of the platelet glycoprotein (GP) IIIa gene has been suggested to play an important role in coronary thrombosis. In vitro studies have shown differences for this polymorphism in platelet sensitivity towards antiplatelet drugs (aspirin and abciximab), suggesting a pharmacogenetic modulation. The aim of the study was to assess the modulatory effect of the PlA polymorphism on clopidogrel-induced antiplatelet effects in 38 patients undergoing coronary stent implantation receiving a 300 mg clopidogrel loading-dose. Platelet reactivity was assessed as GPIIb/IIIa activation and P-selectin expression in platelets stimulated with 2 micromol/l adenosine diphosphate using whole blood flow cytometry. The distribution of the homozygous PlA1/A1 and heterozygous PlA1/A2 genotypes were 74 and 26%, respectively. PlA2 carriers had a higher degree of GPIIb/IIIa activation (P = 0.05) and P-selectin expression (P = 0.02) during the overall study time course and a lower antiplatelet effect to a 300 mg clopidogrel loading-dose up to 24 h following intervention (P < 0.05). In conclusion, the Pl polymorphism of the GPIIIa gene modulates platelet reactivity towards clopidogrel front loading in patients undergoing coronary stenting. This suggests the need for individualized antithrombotic regimens to optimally inhibit platelet reactivity. Copyright 2004 Lippincott Williams and Wilkins

  2. Stability Development of Immediately Loaded Hybrid Self-Tapping Implants Inserted in the Posterior Maxilla: 1-Year Results of a Randomized Controlled Trial.

    Science.gov (United States)

    Todorovic, Vladimir S; Vasovic, Miroslav; Beetge, Mia-Michaela; van Zyl, Andre W; Kokovic, Vladimir

    2017-02-01

    The objective of the present study was to elucidate stability development of immediately loaded hybrid self-tapping implants inserted in the posterior maxilla. Forty-eight hybrid self-tapping implants with a chemically modified surface (∅4.1; length: 8 mm) were inserted bilaterally in the maxillary first and second premolar and first molar sites of 8 patients. In each patient, both sides of the maxilla were assigned randomly to either immediate (IL) or early (EL) loading group. Implant stability was evaluated by means of resonance frequency analysis immediately after implant placement and after 1, 2, 3, 4, 5, 6, 12, 26, and 52 weeks. High values of primary stability were found in both groups (71.91 ± 6.52 implant stability quotient [ISQ] in IL group; 73.87 ± 6.5 ISQ in EL group), with significant differences between the groups at the different time points. Initial decrease in stability was observed between the first and fifth weeks in the IL group and between the first and third weeks for the EL group. In the IL group 1 implant was removed after 3 weeks due to lack of stability. Early results of this study showed the ability of hybrid self-tapping dental implants with a chemically modified surface to achieve sufficient primary stability and to maintain high values of secondary implant stability in bone type 3 and 4, even when loaded immediately. Minimal alterations in stability were observed for both investigated groups, but the EL group showed faster recovery after an initial drop in stability.

  3. Dual effect biodegradable ciprofloxacin loaded implantable matrices for osteomyelitis: controlled release and osteointegration.

    Science.gov (United States)

    Hanafy, Ahmed F; Ali, Hany S M; El Achy, Samar N; Habib, El-Sayed E

    2018-06-01

    Ciprofloxacin biodegradable implantable matrices (CPX-IMs) of tailored porous surfaces were fabricated by hot melt injection molding of poly-l-lactic acid (PLLA) followed by coating with PLLA/sodium chloride. CPX-IDs were designed to have a non-porous coat (NPC) or a porous coat of small pore size (SPC; 150-250 µm) or a large pore size (LPC; 250-350 µm). CPX-IMs surface pore size was confirmed by scanning electron microscope. The hardness of NPC, LPC, and SPC CPX-IMs were 58 ± 2.8, 53 ± 1.9, and 50 ± 2.1 N, respectively. The measured porosity values were 41.2 ± 1.53, 65.2 ± 1.1, and 60.7 ± 1.2%, respectively. Differential scanning calorimetry was employed to study the compatibility of ingredients, the effect of injection molding on polymer properties, and implants degradation. Coating of CPX-IMs prolonged drug release to reach a value of 90% release in 40 days. Antibacterial activity tests showed sufficiency of CPX to inhibit pathogens known to cause osteomyelitis. The in vivo study showed tissue compatibilities of the inserted matrices in tested rats with no sign of infection throughout the experiment period. SPC and LPC CPX-IMs demonstrated a better osteointegration, cell adhesion, and infiltration of different types of bone cells within implants structure compared to the non-porous matrix. Furthermore, LPC CPX-IMs showed a superior bone cell attachment and osteointegration relative to SPC CPX-IMs. Findings of this study confirmed the impact of porosity and pore sizes on cell proliferation and fracture healing concurrently with the sustained local antibiotic therapy for treatment or prevention of osteomyelitis.

  4. The influence of repeated abutment changes on peri-implant tissue stability: 3-year post-loading results from a multicentre randomised controlled trial.

    Science.gov (United States)

    Bressan, Eriberto; Grusovin, Maria Gabriella; D'Avenia, Ferdinando; Neumann, Konrad; Sbricoli, Luca; Luongo, Giuseppe; Esposito, Marco

    To evaluate the influence of at least three abutment disconnections in conventional loaded implants against placement of a definitive abutment in immediately non-occlusal loaded implants on hard and soft tissue changes. A secondary aim was to evaluate whether the presence of less than 2 mm of keratinised mucosa is associated with increased peri-implant marginal bone loss and soft tissue recessions. Eighty patients requiring one single crown or one fixed partial prosthesis supported by a maximum of three implants were randomised, after implants were placed with more than 35 Ncm, according to a parallel group design to receive definitive abutments that were loaded immediately (definitive abutment or immediate loading group) or transmucosal abutments, which were delayed loaded after 3 months and removed at least three times: 1. At impression taking (3 months after implant placement); 2. When checking the zirconium core on titanium abutments at single crowns or the fitting the metal structure at prostheses supported by multiple implants; 3. At delivery of the definitive prostheses (repeated disconnection or conventional loading group). Patients were treated at four centres and each patient contributed to the study, with only one prosthesis followed for 3 years after initial loading. Outcome measures were: prosthesis failures, implant failures, complications, pink aesthetic score (PES), buccal recessions, patient satisfaction, peri-implant marginal bone level changes and height of the keratinised mucosa. Forty patients were randomly allocated to each group according to a parallel group design. Six patients from the definitive abutment group dropped out or died, and one left from the repeated disconnection group. One implant, from the repeated disconnection group, fractured (difference = 3%; CI 95%: -2%, 8%; P = 1). Four provisional crowns and one definitive single crown had to be remade because of poor fitting, and one definitive crown and one definitive prosthesis

  5. Lead-free sliding overplate for highly loaded big end bearings; Bleifreie Laufschicht fuer hochbelastete Haupt- und Pleuellager

    Energy Technology Data Exchange (ETDEWEB)

    Graham, N.; Schnell, L.; Arnold, G. [Federal-Mogul Wiesbaden GmbH and Co. KG (Germany)

    2003-10-01

    Lead has always been an important metal in plain bearing technology. Completely lead-free solutions for high-end engine applications are still not considered to be technically achievable. Therefore, the European End of Life Directive (2000/53/EC), which took effect on 1 July 2003, lists copper-based lead/bronze bearings as an exception. The bearing group of Federal-Mogul has now announced its exit from the lead industry and addresses the issue layer by layer. A recently introduced adaptive bearing offers a lead-free overplate for high-performance internal combustion engine applications. This new bearing changes its technical characteristics during the running-in phase. (orig.) [German] Blei war schon immer eine wichtige Komponente in der Gleitlagertechnik. Bis heute gelten vollstaendig bleifreie Loesungen fuer hochbelastete Gleitlager als technisch nicht machbar. Deshalb nennt die europaeische Altautoverordnung (2000/53/EG), die seit dem 1. Juli 2003 in Kraft ist, als Ausnahme die kupferbasierten Bleibronzelager. Die Gleitlagergruppe von Federal-Mogul hat jetzt ihren Rueckzug aus der Verarbeitung von Blei angekuendigt und geht das Thema Schicht fuer Schicht an. Ein kuerzlich eingefuehrtes, anpassungsfaehiges Lager fuer High-End-Verbrennungsmotoren verfuegt ueber eine bleifreie Laufschicht. Bei diesem neuen Lager veraendern sich die technischen Eigenschaften waehrend der Einlaufphase. (orig.)

  6. Calculation methods for steadily loaded, off-set pivot, tilting pad thrust bearings. (Guide to use of computer program A9235.)

    Science.gov (United States)

    1992-12-01

    ESDU 92035 provides details of a FORTRAN program that implements the calculation method of ESDU 83004. It allows performance analysis of an existing design, or the design of a bearing dimensions, subject to any space constraint, are recommended. The predicted performance includes the lubricant film thickness under load, its temperature and flow rate, the power loss, and the bearing temperature. Recommendations are also made on surface finish. Warning messages are output in the following cases, for each of which possible remedial actions are suggested: drain or pad temperature too high, churning losses too great, film thickness too small, pad number too high, ratio or inner to outer pad radius too large, flow rate too great, lubricant or pad temperature outside usable range. A lubricant database is provided that may be extended or edited. The program applies to Newtonian lubricants in laminar flow. Worked examples illustrate the use of the program.

  7. Beam-envelope calculations of space-charge loaded beams in MeV dc ion-implantation facilities

    International Nuclear Information System (INIS)

    Urbanus, W.H.; Bannenberg, J.G.; Doorn, S.; Saris, F.W.; Koudijs, R.; Dubbelman, P.; Koelewijn, W.

    1989-01-01

    MeV dc ion accelerators are being developed that can deliver a beam current up to several hundred micro-amperes. At the low-energy part of the accelerator, the beam transport is space-charge dominated rather than emittance dominated. A system of differential equations has been derived, based on the Kapchinski-Vladimirski equations, which describe the envelope of a space-charge loaded ion beam, taking a longitudinal electrical field in an accelerating tube into account. The equations have been used to design the accelerator of a high-current 1 MV heavy-ion implantation facility. Furthermore, the design of a 2 MV accelerator is presented, which is used for analyzing techniques such as RBS and PIXE. Both facilities are based on single-ended Van de Graaff accelerators. (orig.)

  8. Early Loading of Fluoridated Implants Placed in Fresh Extraction Sockets and Healed Bone: A 3- to 5-Year Clinical and Radiographic Follow-Up Study of 39 Consecutive Patients.

    Science.gov (United States)

    Oxby, Gert; Oxby, Fredrik; Oxby, Johan; Saltvik, Tomas; Nilsson, Peter

    2015-10-01

    Immediate placement of implants in extraction sockets for early loading is an attractive treatment modality due to reduced treatment time. However, the outcome of fluoridated implants in this situation with regard to bone levels and health of soft tissues is not well documented. To evaluate the outcome of early loading of OsseoSpeed(™) dental implants placed into fresh extraction sockets and healed bone in consecutive patients treated in a private clinic. A total of 182 OsseoSpeed(™) implants (Astra Tech Implant System, DENTSPLY Implants, Mölndal, Sweden), 72 in immediate extraction sockets and 110 in healed sites, were placed in 39 consecutive patients. The implants were loaded with permanent restorations within 60 days (average 31 days). Clinical and radiographic follow-up examinations were performed annually for at least 3 years (mean 55 months). An aesthetic index was used to evaluate the soft tissues adjacent to the prosthetic restorations. No implant was lost during the observation period, giving a survival rate of 100%. Bone level changes during the observation period were minimal, with a mean marginal bone loss of 0.3 ± 0.9 mm around the delayed implants and a mean marginal bone gain of 0.3 ± 1.4 mm around the immediate implants (p = .0036). The frequency distribution of bone level revealed that 85% of implants placed in fresh extraction sockets and 84% of implants in healed bone did not show any loss of bone level during follow-up (p = NS). Soft tissue complications were observed at two immediate implant sites in one patient. The remaining 180 implants received the highest aesthetic score. Moreover, no signs of peri-implant purulent infection or aggressive bone loss were found during the follow-up period. Early loading of fluoridated implants with permanent constructions appears to be a viable therapy for implants placed immediately in extraction sites and in healed bone. © 2014 Wiley Periodicals, Inc.

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

    Science.gov (United States)

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

    2014-01-01

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

  10. Gentamicin-loaded poly(lactic-co-glycolic acid) microparticles for the prevention of maxillofacial and orthopedic implant infections

    International Nuclear Information System (INIS)

    Flores, Claudia; Degoutin, Stephanie; Chai, Feng; Raoul, Gwenael; Hornez, Jean-Chritophe; Martel, Bernard; Siepmann, Juergen; Ferri, Joel; Blanchemain, Nicolas

    2016-01-01

    Trauma and orthopedic surgery can cause infections as any open surgical procedures. Such complications occur in only1 to 5% of the cases, but the treatment is rather complicated due to bacterial biofilm formation and limited drug access to the site of infection upon systemic administration. An interesting strategy to overcome this type of complications is to prevent bacterial proliferation and biofilm formation via the local and controlled release of antibiotic drugs from the implant itself. Obviously, the incorporation of the drug into the implant should not affect the latter's biological and mechanical properties. In this context, we optimized the preparation process for gentamicin-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles, which can be incorporated in the macropores of calcium phosphate-based bone substitutes. Microparticles were prepared using a double emulsion solvent extraction/evaporation technique. The processing parameters were optimized in order to provide an average microparticle size of about 60 μm, allowing for incorporation inside the macropores (100 μm) of the hydroxyapatite scaffold. Gentamicin-loaded PLGA microparticles showed a sustained release for 25–30 days and a rapid antibacterial activity due to a burst effect, the extent of which was controlled by the initial loading of the microparticles. SEM pictures revealed a highly porous microparticle structure, which can help to reduce the micro environmental pH drop and autocatalytic effects. The biological evaluation showed the cytocompatibility and non-hemolytic property of the microparticles, and the antibacterial activity against Staphylococcus aureus under the given conditions. - Highlights: • The optimization of microparticle preparation parameters allows to obtain a size compatible with the bone substitute porosity • PDL% has a direct impact on the burst effect, a control release of gentamicin was obtained • The incorporation of microparticles into the macroporosity

  11. Gentamicin-loaded poly(lactic-co-glycolic acid) microparticles for the prevention of maxillofacial and orthopedic implant infections

    Energy Technology Data Exchange (ETDEWEB)

    Flores, Claudia [Univ. Lille, 59000 Lille (France); INSERM U1008, Controlled Drug Delivery Systems and Biomaterials, 59000 Lille (France); Degoutin, Stephanie [Univ. Lille, 59000 Lille (France); UMET, Ingénierie des Systèmes Polymères, Université de Lille 1, 59655 Villeneuve d' Ascq (France); Chai, Feng [Univ. Lille, 59000 Lille (France); INSERM U1008, Controlled Drug Delivery Systems and Biomaterials, 59000 Lille (France); Raoul, Gwenael [Univ. Lille, 59000 Lille (France); INSERM U1008, Controlled Drug Delivery Systems and Biomaterials, 59000 Lille (France); Service Chirurgie Maxillo-Faciale, CHRU de Lille, 59000 Lille (France); Hornez, Jean-Chritophe [Laboratoire des Matériaux Céramiques et Procédés Associés (LMCPA), Université de Valenciennes, 59300 Valenciennes (France); Martel, Bernard [Univ. Lille, 59000 Lille (France); UMET, Ingénierie des Systèmes Polymères, Université de Lille 1, 59655 Villeneuve d' Ascq (France); Siepmann, Juergen [Univ. Lille, 59000 Lille (France); INSERM U1008, Controlled Drug Delivery Systems and Biomaterials, 59000 Lille (France); Ferri, Joel [Univ. Lille, 59000 Lille (France); INSERM U1008, Controlled Drug Delivery Systems and Biomaterials, 59000 Lille (France); Service Chirurgie Maxillo-Faciale, CHRU de Lille, 59000 Lille (France); Blanchemain, Nicolas, E-mail: nicolas.blanchemain@univ-lille2.fr [Univ. Lille, 59000 Lille (France); INSERM U1008, Controlled Drug Delivery Systems and Biomaterials, 59000 Lille (France)

    2016-07-01

    Trauma and orthopedic surgery can cause infections as any open surgical procedures. Such complications occur in only1 to 5% of the cases, but the treatment is rather complicated due to bacterial biofilm formation and limited drug access to the site of infection upon systemic administration. An interesting strategy to overcome this type of complications is to prevent bacterial proliferation and biofilm formation via the local and controlled release of antibiotic drugs from the implant itself. Obviously, the incorporation of the drug into the implant should not affect the latter's biological and mechanical properties. In this context, we optimized the preparation process for gentamicin-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles, which can be incorporated in the macropores of calcium phosphate-based bone substitutes. Microparticles were prepared using a double emulsion solvent extraction/evaporation technique. The processing parameters were optimized in order to provide an average microparticle size of about 60 μm, allowing for incorporation inside the macropores (100 μm) of the hydroxyapatite scaffold. Gentamicin-loaded PLGA microparticles showed a sustained release for 25–30 days and a rapid antibacterial activity due to a burst effect, the extent of which was controlled by the initial loading of the microparticles. SEM pictures revealed a highly porous microparticle structure, which can help to reduce the micro environmental pH drop and autocatalytic effects. The biological evaluation showed the cytocompatibility and non-hemolytic property of the microparticles, and the antibacterial activity against Staphylococcus aureus under the given conditions. - Highlights: • The optimization of microparticle preparation parameters allows to obtain a size compatible with the bone substitute porosity • PDL% has a direct impact on the burst effect, a control release of gentamicin was obtained • The incorporation of microparticles into the

  12. Importance of a distal proximal contact on load transfer by implant-supported single adjacent crowns in posterior region of the mandible: a photoelastic study

    Directory of Open Access Journals (Sweden)

    Fabio Afranio de Aguiar Junior

    2013-09-01

    Full Text Available OBJECTIVE: This study aimed to evaluate the importance of a distal proximal contact on the load transfer to the posterior region of the mandible by non-splinted adjacent implant-supported crowns using photoelastic stress analysis. MATERIAL AND METHODS: A rectangular model (68x30x15 mm was made of polymethylmethacrylate resin to simulate half of the mandibular arch. One model was completed with resin replicas representing the first premolar and second molar and with two 3.75 mm dia.x11 mm internal hexagon threaded implants replacing the second premolar and first molar. The other model was manufactured in the same way but without the second molar. Both models were duplicated using photoelastic resin. The roots of the teeth replicas were covered with a layer of polyether impression material to simulate the periodontal ligament. Two different vertical loads were applied to the crowns as follows: 1 - single static point load alternately applied to the crowns replacing the second premolar and first molar (50 N; 2 - simultaneous static point loads applied to both of the crowns replacing the second premolar and first molar (100 N. The resulting isochromatic fringe pattern in the photoelastic model was monitored and photographed. RESULTS: All loading conditions studied showed that the presence of the second molar has changed the load transmission and the pattern of stresses. CONCLUSION: Results showed that the presence of a second molar proximal contact can help minimize the stresses around the implants.

  13. Soft tissue around three different implant types after 1.5 years of functional loading without oral hygiene: a preliminary study in baboons.

    Science.gov (United States)

    Watzak, Georg; Zechner, Werner; Tangl, Stefan; Vasak, Christoph; Donath, Karl; Watzek, Georg

    2006-04-01

    The purpose of this study was to determine the peri-implant soft tissue dimension (PSD) and peri-implant bone level (BL) of dental implants with different designs and surface modifications after functional loading without oral hygiene. Three types of dental implants were placed in the posterior jaws of adult baboons, three of the same design per quadrant, and fitted with fixed partial dentures. After 1.5 years of functional loading and plaque accumulation, all implants showed severe peri-implant mucositis and comparatively high BL. A histomorphometric evaluation of the sulcus depth (SD), the dimension of the junctional epithelium (JE) and the connective tissue contact (CTC) resulted in no significant differences between the three implant designs, neither in the maxilla nor in the mandible (P>0.05). The sum of SD, JE and CTC forming the PSD was nearly the same in the maxilla (commercially pure titanium, CpTi: 3.5 mm 2.9/4.1 confidence interval (CI); titanium plasma sprayed (TPS): 3.5 mm 2.9/4.2 CI; sand blasted acid-etched (GBAE): 3.2 mm 2.7/3.9 CI) and in the mandible (CpTi: 3.2 mm 2.6/3.8 CI; TPS: 3.2 mm 2.6/3.8 CI; GBAE: 3.2 mm 2.7/3.9 CI; P>0.05). There was no difference in BL around the three implant designs (maxilla: CpTi: 0.9 mm 0.5/1.6 CI; TPS: 0.9 mm 0.5/1.5CI; GBAE: 0.9 mm 0.5/1.6 CI; mandible: CpTi: 0.8 mm 0.5/1.2 CI; TPS: 0.6 mm 0.4/0.9 CI; GBAE: 0.7 mm 0.5/1.1 CI; P>0.05). Overall, the data presented did not show any significant differences in peri-implant soft tissue conditions in baboons. Moreover, plaque accumulation and propagation of peri-implant mucositis after 1.5 years of functional loading was not influenced by implant design and surface modifications in baboons.

  14. A systematic review on immediate loading of implants used to support overdentures opposed by conventional prostheses : factors that might influence clinical outcomes

    NARCIS (Netherlands)

    Zygogiannis, K.; Wismeijer, D.; Aartman, I.H.A.; Osman, R.B.

    2016-01-01

    Purpose: Different treatment protocols in terms of number, diameter, and suprastructure design have been proposed for immediately loaded implants that are used to support mandibular overdentures opposed by maxillary conventional dentures. The aim of this study was to investigate the influence of

  15. Finite element analysis of dental implant loading on atrophic and non-atrophic cancellous and cortical mandibular bone - a feasibility study.

    Science.gov (United States)

    Marcián, Petr; Borák, Libor; Valášek, Jiří; Kaiser, Jozef; Florian, Zdeněk; Wolff, Jan

    2014-12-18

    The first aim of this study was to assess displacements and micro-strain induced on different grades of atrophic cortical and trabecular mandibular bone by axially loaded dental implants using finite element analysis (FEA). The second aim was to assess the micro-strain induced by different implant geometries and the levels of bone-to-implant contact (BIC) on the surrounding bone. Six mandibular bone segments demonstrating different grades of mandibular bone atrophy and various bone volume fractions (from 0.149 to 0.471) were imaged using a micro-CT device. The acquired bone STL models and implant (Brånemark, Straumann, Ankylos) were merged into a three-dimensional finite elements structure. The mean displacement value for all implants was 3.1 ±1.2 µm. Displacements were lower in the group with a strong BIC. The results indicated that the maximum strain values of cortical and cancellous bone increased with lower bone density. Strain distribution is the first and foremost dependent on the shape of bone and architecture of cancellous bone. The geometry of the implant, thread patterns, grade of bone atrophy and BIC all affect the displacement and micro-strain on the mandible bone. Preoperative finite element analysis could offer improved predictability in the long-term outlook of dental implant restorations. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Least Limiting Water Range and Load Bearing Capacity of Soil under Types of Tractor-Trailers for Mechanical Harvesting of Green Sugarcane

    Directory of Open Access Journals (Sweden)

    Antonio Higino Frederico Pereira

    2015-12-01

    Full Text Available ABSTRACT The expansion of the sugarcane industry in Brazil has intensified the mechanization of agriculture and caused effects on the soil physical quality. The purpose of this study was to evaluate the limiting water range and soil bearing capacity of a Latossolo Vermelho distroférrico típico (Rhodic Hapludox under the influence of different tractor-trailers used in mechanical sugarcane harvesting. The experiment was arranged in a randomized block design with five replications. The treatments consisted of green sugarcane harvesting with: harvester without trailer (T1; harvester with two trailers with a capacity of 10 Mg each (T2; harvester with trailer with a capacity of 20 Mg (T3 and harvester and truck with trailer with a capacity of 20 Mg (10 Mg per compartment (T4. The least limiting water range and soil bearing capacity were evaluated. The transport equipment to remove the harvested sugarcane from the field (trailer at harvest decreased the least limiting water range, reducing the structural soil quality. The truck trailer caused the greatest impact on the soil physical properties studied. The soil load bearing capacity was unaffected by the treatments, since the pressure of the harvester (T1 exceeded the pre-consolidation pressure of the soil.

  17. Effects of spine loading in a patient with post-decompression lumbar disc herniation: observations using an open weight-bearing MRI.

    Science.gov (United States)

    Mahato, Niladri Kumar; Sybert, Daryl; Law, Tim; Clark, Brian

    2017-05-01

    Our objective was to use an open weight-bearing MRI to identify the effects of different loading conditions on the inter-vertebral anatomy of the lumbar spine in a post-discectomy recurrent lumbar disc herniation patient. A 43-year-old male with a left-sided L5-S1 post-decompression re-herniation underwent MR imaging in three spine-loading conditions: (1) supine, (2) weight-bearing on standing (WB), and (3) WB with 10 % of body mass axial loading (WB + AL) (5 % through each shoulder). A segmentation-based proprietary software was used to calculate and compare linear dimensions, angles and cross sections across the lumbar spine. The L5 vertebrae showed a 4.6 mm posterior shift at L5-S1 in the supine position that changed to an anterior translation >2.0 mm on WB. The spinal canal sagittal thickness at L5-S1 reduced from supine to WB and WB + AL (13.4, 10.6, 9.5 mm) with corresponding increases of 2.4 and 3.5 mm in the L5-S1 disc protrusion with WB and WB + AL, respectively. Change from supine to WB and WB + AL altered the L5-S1 disc heights (10.2, 8.6, 7.0 mm), left L5-S1 foramen heights (12.9, 11.8, 10.9 mm), L5-S1 segmental angles (10.3°, 2.8°, 4.3°), sacral angles (38.5°, 38.3°, 40.3°), L1-L3-L5 angles (161.4°, 157.1°, 155.1°), and the dural sac cross sectional areas (149, 130, 131 mm 2 ). Notably, the adjacent L4-L5 segment demonstrated a retro-listhesis >2.3 mm on WB. We observed that with weight-bearing, measurements indicative of spinal canal narrowing could be detected. These findings suggest that further research is warranted to determine the potential utility of weight-bearing MRI in clinical decision-making.

  18. The effects of hydroxyapatite coating and bone allograft on fixation of loaded experimental primary and revision implants

    DEFF Research Database (Denmark)

    Søballe, Kjeld; Mouzin, Olivier R G; Kidder, Louis A

    2003-01-01

    We used our established experimental model of revision joint replacement to examine the roles of hydroxyapatite coating and bone graft in improving the fixation of revision implants. The revision protocol uses the Søballe micromotion device in a preliminary 8-week period of implant instability...... a titanium alloy (Ti) or a hydroxyapatite (HA) 6.0 mm plasma-sprayed implant, in the presence or absence of allograft packed into the initial 0.75 mm peri-implant gap. The contralateral limb is subjected to primary surgery with the same implant configuration, and serves as control. 8 implants were included...

  19. Fracture load of complete-arch implant-supported prostheses reinforced with nylon-silica mesh: An in vitro study.

    Science.gov (United States)

    Gonçalves, Fernanda de Cássia Papaiz; Amaral, Marina; Borges, Alexandre Luiz Souto; Gonçalves, Luiz Fernando Martins; Paes-Junior, Tarcisio José de Arruda

    2018-04-01

    Complete-arch implant-supported prostheses without a framework have a high risk of failure: a straightforward and inexpensive reinforcement material, such as nylon mesh, could improve their longevity. The purpose of this in vitro study was to evaluate a nylon-silica mesh compound on the fracture strength of acrylic resin and the fracture load of complete-arch implant-supported prostheses. Twenty-four complete mandibular arch implant-supported prostheses were divided into 2 groups according to cantilever length (molar and premolar) and subdivided into another 2 subgroups according to the presence or absence of reinforcing mesh. The specimens were submitted to a maximum load-to-fracture test in a universal testing machine, with a 100-N load cell, a 2 mm/min crosshead speed, and a spherical metal tip diameter of 4 mm at different points (molar and premolar). These were submitted to 1-way analysis of variance for repeated measurement and the post hoc Tukey multiple comparison test (α=.05). The mean maximum load ±standard deviation for the molar group was 393.4 ±95.0 N with reinforcement and 305.4 ±76.3 N without reinforcement (P=.02); and for the premolar group was 1083.3 ±283.7 N with reinforcement and 605.3 ±90.5 N without reinforcement (P=.001). Reinforcement with nylon mesh increased the mean maximum load of implant-supported complete-arch prostheses at both cantilever lengths. The cantilever to the premolar (5 mm) presented the highest maximum load values to fracture. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  20. Effect of screw access hole preparation on fracture load of implant-supported zirconia-based crowns: an in vitro study

    Directory of Open Access Journals (Sweden)

    Hadi Mokhtarpour

    2016-07-01

    Full Text Available Background. Fracture load of implant-supported restorations is an important factor in clinical success. This study evaluated the effect of two techniques for screw access hole preparation on the fracture load of cement-screw-retained implant-supported zirconia-based crowns. Methods. Thirty similar cement-screw-retained implant-supported zirconia-based maxillary central incisor crowns were evaluated in three groups of 10. Group NH: with no screw access holes for the control; Group HBS: with screw access holes prepared with a machine before zirconia sintering; Group HAS: with screw access holes prepared manually after zirconia sintering. In group HBS, the access holes were virtually designed and prepared by a computer-assisted design/computer-assisted manufacturing system. In group HAS, the access holes were manually prepared after zirconia sintering using a diamond bur. The dimensions of the screw access holes were equal in both groups. The crowns were cemented onto same-size abutments and were then subjected to thermocycling. The fracture load values of the crowns were measured using a universal testing machine. Data were analyzed with ANOVA and Tukey test (P < 0.05. Results. The mean fracture load value for the group NH was 888.37 ± 228.92 N, which was the highest among the groups, with a significant difference (P < 0.0001. The fracture load values were 610.48 ± 125.02 N and 496.74 ± 104.10 Nin the HBS and HAS groups, respectively, with no significant differences (P = 0.44. Conclusion. Both techniques used for preparation of screw access holes in implant-supported zirconia-based crowns de-creased the fracture load.

  1. Immediate Loading of Implants in the Edentulous Maxilla with a Fixed Provisional Restoration without Bone Augmentation: A Report on 5-Year Outcomes Data Obtained from a Prospective Clinical Trial.

    Science.gov (United States)

    Toljanic, Joseph A; Ekstrand, Karl; Baer, Russell A; Thor, Andreas

    2016-01-01

    Successful immediate loading of implants in the edentulous maxilla has been previously reported. The purpose of this 5-year prospective study was to further assess long-term outcomes following immediate loading of implants in the edentulous maxilla with fixed provisional restorations without the use of bone augmentation procedures. Subjects with edentulous maxillary arches each received six implants placed in native bone without augmentation. Where insufficient posterior bone volume existed, angled implant placement was employed. Fixed provisional restorations were delivered within 24 hours of implant placement. Implant placement locations, insertion torque values, and implant dimensions were recorded. Definitive fixed prostheses were placed within 24 weeks following implantation. Baseline implant site marginal bone levels were measured using periapical radiographs. Baseline peri-implant plaque and bleeding scores were obtained. Subjects were examined 6 months after implant placement and then annually for 5 years with follow-up periapical radiographs and plaque/bleeding scores obtained. Fifty-one subjects received a total of 306 implants. Forty subjects with 232 implants returned for the final follow-up appointment representing a 5-year implant survival proportion of 93% with a mean marginal bone loss of 0.44 ± 1.25 mm for this group. Thirty-nine of these 40 subjects continued to function with fixed restorations with the remaining subject functioning with a non-implant-retained removable prosthesis. Within the limitations of this study, predictable long-term implant rehabilitation outcomes were demonstrated for the edentulous maxilla using an immediate loading protocol without bone augmentation.

  2. Telemetry experiments with a hibernating black bear

    Science.gov (United States)

    Craighead, J. J.; Varney, J. R.; Sumner, J. S.; Craighead, F. C., Jr.

    1972-01-01

    The objectives of this research were to develop and test telemetry equipment suitable for monitoring physiological parameters and activity of a hibernating bear in its den, to monitor this data and other environmental information with the Nimbus 3 IRLS data collection system, and to refine immobilizing, handling, and other techniques required in future work with wild bears under natural conditions. A temperature-telemetering transmitter was implanted in the abdominal cavity of a captive black bear and body temperature data was recorded continuously during a 3 month hibernation period. Body temperatures ranging between 37.5 and 31.8 C were observed. Body temperature and overall activity were influenced by disturbances and ambient den temperature. Nychthemeral temperature changes were not noticable. A load cell weight recording device was tested for determining weight loss during hibernation. Monitoring of data by satellite was not attempted. The implanted transmitter was removed and the bear was released with a radiolocation collar at the conclusion of the experiment.

  3. A new platelet cryoprecipitate glue promoting bone formation after ectopic mesenchymal stromal cell-loaded biomaterial implantation in nude mice.

    Science.gov (United States)

    Trouillas, Marina; Prat, Marie; Doucet, Christelle; Ernou, Isabelle; Laplace-Builhé, Corinne; Blancard, Patrick Saint; Holy, Xavier; Lataillade, Jean-Jacques

    2013-01-04

    This study investigated the promising effect of a new Platelet Glue obtained from Cryoprecipitation of Apheresis Platelet products (PGCAP) used in combination with Mesenchymal Stromal Cells (MSC) loaded on ceramic biomaterials to provide novel strategies enhancing bone repair. PGCAP growth factor content was analyzed by ELISA and compared to other platelet and plasma-derived products. MSC loaded on biomaterials (65% hydroxyapatite/35% beta-TCP or 100% beta-TCP) were embedded in PGCAP and grown in presence or not of osteogenic induction medium for 21 days. Biomaterials were then implanted subcutaneously in immunodeficient mice for 28 days. Effect of PGCAP on MSC was evaluated in vitro by proliferation and osteoblastic gene expression analysis and in vivo by histology and immunohistochemistry. We showed that PGCAP, compared to other platelet-derived products, allowed concentrating large amount of growth factors and cytokines which promoted MSC and osteoprogenitor proliferation. Next, we found that PGCAP improves the proliferation of MSC and osteogenic-induced MSC. Furthermore, we demonstrated that PGCAP up-regulates the mRNA expression of osteogenic markers (Collagen type I, Osteonectin, Osteopontin and Runx2). In vivo, type I collagen expressed in ectopic bone-like tissue was highly enhanced in biomaterials embedded in PGCAP in the absence of osteogenic pre-induction. Better results were obtained with 65% hydroxyapatite/35% beta-TCP biomaterials as compared to 100% beta-TCP. We have demonstrated that PGCAP is able to enhance in vitro MSC proliferation, osteoblastic differentiation and in vivo bone formation in the absence of osteogenic pre-induction. This clinically adaptable platelet glue could be of interest for improving bone repair.

  4. Recent advances in the design of drug-loaded polymeric implants for the treatment of solid tumors.

    Science.gov (United States)

    Wadee, Ameena; Pillay, Viness; Choonara, Yahya E; du Toit, Lisa C; Penny, Clement; Ndesendo, Valence M K; Kumar, Pradeep; Murphy, Caragh S

    2011-10-01

    The effective treatment of solid tumors continues to be a great challenge to clinicians, despite the development of novel drugs. In order to improve the clinical efficacy of existing chemotherapeutic agents, researchers have considered the possibility of site-specific solid tumor treatment. The greatest advantage of localized delivery is the significantly fewer side effects experienced by patients. Recently, in situ forming implants have attracted considerable interest. These polymeric systems are injected as solutions into tumor sites and the injected solution forms an implant as a result of local environmental stimuli and hence removes the need for surgical implantation. This review summarizes the attempts that have been made to date in the development of polymeric implants for the treatment of solid tumors. Both in situ forming implants and preformed implants, fabricated using natural and synthetic polymers, are described. In addition, the peri- or intra-tumoral delivery of chemotherapeutic agents based on implants inserted surgically into the affected region is also discussed along with a short coverage of implants having an undesirable initial burst release effect. Although these implants have been shown to improve the treatment of various solid tumors, the ideal implant that is able to deliver high doses of chemotherapeutics to the tumor site, over prolonged periods with relatively few side effects on normal tissue, is yet to be formulated.

  5. The effects of hydroxyapatite coating and bone allograft on fixation of loaded experimental primary and revision implants.

    Science.gov (United States)

    Søballe, Kjeld; Mouzin, Olivier R G; Kidder, Louis A; Overgaard, Søren; Bechtold, Joan E

    2003-06-01

    We used our established experimental model of revision joint replacement to examine the roles of hydroxyapatite coating and bone graft in improving the fixation of revision implants. The revision protocol uses the Søballe micromotion device in a preliminary 8-week period of implant instability for the presence of particulate polyethylene. During this procedure, a sclerotic endosteal bone rim forms, and a dense fibrous membrane is engendered, having macrophages with ingested polyethylene and high levels of inflammatory cytokines. At the time of revision after 8 weeks, the cavity is revised with either a titanium alloy (Ti) or a hydroxyapatite (HA) 6.0 mm plasma-sprayed implant, in the presence or absence of allograft packed into the initial 0.75 mm peri-implant gap. The contralateral limb is subjected to primary surgery with the same implant configuration, and serves as control. 8 implants were included in each of the 8 treatment groups (total 64 implants in 32 dogs). The observation period was 4 weeks after revision. Outcome measures are based on histomorphometry and mechanical pushout properties. The revision setting was always inferior to its primary counterpart. Bone graft improved the revision fixation in all treatment groups, as also did the HA coating. The sole exception was revision-grafted HA implants, which reached the same fixation as primary Ti and HA grafted implants. The revision, which was less active in general, seems to need the dual stimulation of bone graft and HA implant surface, to obtain the same level of fixation associated with primary implants. Our findings suggest that the combination of HA implant and bone graft may be of benefit in the clinical revision implant setting.

  6. A deep convolutional neural network with new training methods for bearing fault diagnosis under noisy environment and different working load

    Science.gov (United States)

    Zhang, Wei; Li, Chuanhao; Peng, Gaoliang; Chen, Yuanhang; Zhang, Zhujun

    2018-02-01

    In recent years, intelligent fault diagnosis algorithms using machine learning technique have achieved much success. However, due to the fact that in real world industrial applications, the working load is changing all the time and noise from the working environment is inevitable, degradation of the performance of intelligent fault diagnosis methods is very serious. In this paper, a new model based on deep learning is proposed to address the problem. Our contributions of include: First, we proposed an end-to-end method that takes raw temporal signals as inputs and thus doesn't need any time consuming denoising preprocessing. The model can achieve pretty high accuracy under noisy environment. Second, the model does not rely on any domain adaptation algorithm or require information of the target domain. It can achieve high accuracy when working load is changed. To understand the proposed model, we will visualize the learned features, and try to analyze the reasons behind the high performance of the model.

  7. Influence of crop load on the expression patterns of starch metabolism genes in alternate-bearing Citrus trees.

    OpenAIRE

    González Nebauer, Sergio; Renau Morata, Begoña; Lluch Gomez, Yolanda Patricia; BAROJA FERNANDEZ, EDURNE; POZUETA-ROMERO, JAVIER; Molina Romero, Rosa Victoria

    2014-01-01

    [EN] The fruit is the main sink organ in Citrus and captures almost all available photoassimilates during its development. Consequently, carbohydrate partitioning and starch content depend on the crop load of Citrus trees. Nevertheless, little is known about the mechanisms controlling the starch metabolism at the tree level in relation to presence of fruit. The aim of this study was to find the relation between the seasonal variation of expression and activity of the genes involved in carbon...

  8. Changes in general and oral health-related quality of life in immediate or conventionally loaded dental implants: a nonrandomized clinical trial.

    Science.gov (United States)

    Dolz, Javier; Silvestre, Francisco J; Montero, Javier

    2014-01-01

    To evaluate changes in the general and oral health-related quality of life (using the European Quality of Life indicator and the Oral Health Impact Profile-49 [OHIP-49], respectively) of patients treated with conventionally or immediately loaded implants. This clinical trial consisted of a clinical oral examination and a questionnaire-based interview carried out before and after both surgery and definitive prosthetic rehabilitation in a consecutive sample of patients requiring dental implants. According to the clinical diagnosis and patient preference, patients were assigned to the immediate loading group (IL group; n = 29) or the conventional loading group (CL group; n = 75). The change summary scores and effect sizes were calculated in the intermediate stage and at the final follow-up, taking baseline scores as reference. The oral health-related quality of life and oral satisfaction after implant therapy were significantly better than at baseline, with an even greater benefit when the implants were loaded immediately than when prosthetic rehabilitation was delayed. However, there were no significant differences in between-group comparisons in the ratings of general health status. The effect size for the OHIP-49 exceeded the threshold value of 0.8 for the domains functional limitation, pain/discomfort, and psychological discomfort in both groups and also for physical disability and psychological disability in the IL group. A gradual improvement in oral well-being scores, but not in those of general well-being, were observed for both groups from the intermediate stage to the final evaluation. This benefit was markedly greater for the IL group.

  9. In vitro comparison of fracture load of implant-supported, zirconia-based, porcelain- and composite-layered restorations after artificial aging.

    Science.gov (United States)

    Komine, Futoshi; Taguchi, Kohei; Fushiki, Ryosuke; Kamio, Shingo; Iwasaki, Taro; Matsumura, Hideo

    2014-01-01

    This study evaluated fracture load of single-tooth, implant-supported, zirconia-based, porcelain- and indirect composite-layered restorations after artificial aging. Forty-four zirconia-based molar restorations were fabricated on implant abutments and divided into four groups, namely, zirconia-based all-ceramic restorations (ZAC group) and three types of zirconia-based composite-layered restorations (ZIC-P, ZIC-E, and ZIC groups). Before layering an indirect composite material, the zirconia copings in the ZIC-P and ZIC-E groups were primed with Clearfil Photo Bond and Estenia Opaque Primer, respectively. All restorations were cemented on the abutments with glass-ionomer cement and then subjected to thermal cycling and cyclic loading. All specimens survived thermal cycling and cyclic loading. The fracture load of the ZIC-P group (2.72 kN) was not significantly different from that of the ZAC group (3.05 kN). The fracture load of the zirconia-based composite-layered restoration primed with Clearfil Photo Bond (ZIC-P) was comparable to that of the zirconia-based all-ceramic restoration (ZAC) after artificial aging.

  10. The Effect of Docetaxel-Loaded Micro-Bubbles Combined with Low-Frequency Ultrasound in H22 Hepatocellular Carcinoma-Bearing Mice.

    Science.gov (United States)

    Ren, Shu-Ting; Shen, Shu; He, Xin-Ying; Liao, Yi-Ran; Sun, Peng-Fei; Wang, Bing; Zhao, Wen-Bao; Han, Shui-Ping; Wang, Yi-Li; Tian, Tian

    2016-02-01

    A novel lipid micro-bubble (MB) loaded with docetaxel (DOC-MB) was investigated in a previous study. However, its anti-tumor effects and mechanism of action in combination with low-frequency ultrasound (LFUS) in vivo are still unclear. DOC-MBs containing 5.0 mg of DOC were prepared by lyophilization with modification via ultrasonic emulsification. Then, the effects of DOC-MBs combined with LFUS on tumor growth, proliferating cell nuclear antigen (PCNA) expression and cell apoptosis, as well as local DOC delivery, were investigated in H22 hepatocellular carcinoma (HCC)-bearing mice. Compared with the previously prepared DOC-MBs (1.6 mg of DOC loaded), the encapsulation efficiency (81.2% ± 3.89%) and concentration ([7.94 ± 0.04] × 10(9) bubbles/mL) of the DOC-MBs containing 5.0 mg of DOC were higher, but the bubble size (1.368 ± 0.004 μm) was smaller. After treatment with the DOC-MBs and LFUS, the H22 HCC growth inhibition rate was significantly increased, PCNA expression in tumor tissue was significantly inhibited and local release of DOC was induced. In conclusion, new DOC-MBs containing 5.0 mg of DOC were successfully prepared with a high encapsulation efficiency and superior bubble size and concentration, and their combination with LFUS significantly enhanced the anti-tumor effect of DOC in H22 HCC-bearing mice by inhibiting tumor cell proliferation and increasing local drug delivery. Copyright © 2016 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  11. Bone attachment to glass-fibre-reinforced composite implant with porous surface.

    Science.gov (United States)

    Mattila, R H; Laurila, P; Rekola, J; Gunn, J; Lassila, L V J; Mäntylä, T; Aho, A J; Vallittu, P K

    2009-06-01

    A method has recently been developed for producing fibre-reinforced composites (FRC) with porous surfaces, intended for use as load-bearing orthopaedic implants. This study focuses on evaluation of the bone-bonding behaviour of FRC implants. Three types of cylindrical implants, i.e. FRC implants with a porous surface, solid polymethyl methacrylate (PMMA) implants and titanium (Ti) implants, were inserted in a transverse direction into the intercondular trabeculous bone area of distal femurs and proximal tibias of New Zealand White rabbits. Animals were sacrificed at 3, 6 and 12 weeks post operation, and push-out tests (n=5-6 per implant type per time point) were then carried out. At 12 weeks the shear force at the porous FRC-bone interface was significantly higher (283.3+/-55.3N) than the shear force at interfaces of solid PMMA/bone (14.4+/-11.0 N; pshielding effect.

  12. Stripping study of U(VI) from loaded TBP/n-paraffin using ammonium nitrate bearing waste as strippant

    International Nuclear Information System (INIS)

    Shrishma Paik; Biswas, S.; Bhattacharya, S.; Roy, S.B.

    2013-01-01

    Stripping studies of U(VI) from loaded solvent TBP/n-paraffin was carried out using ammonium nitrate solution as strippant. Effects of various stripping parameters such as concentration of ammonium nitrate solution, U(VI) concentration in organic phase, initial pH of strippant, temperature etc. have been investigated in detail. Kinetics of the stripping process by ammonium nitrate was found to be slower than that of stripping with water. It was observed that with the increase in ammonium nitrate concentration in aqueous solution, stripping of U(VI) decreased. With the increase in U(VI) loading in the organic phase, there was an increase in uranium stripping for ammonium nitrate whereas for distilled water it becomes reverse. With the increase in pH of the aqueous ammonium nitrate solution, stripping increased up to a certain pH of 8.5 and after that precipitation of uranium started. Increase in temperature of the biphasic system shows an enhancing effect of U(VI) stripping. Evaluation of thermodynamic data such as ΔH indicated that the process is endothermic. Based on the optimized conditions, McCabe-Thiele diagram was constructed for U(VI) stripping using ammonium nitrate solution at room temperature. (author)

  13. Silk coating on a bioactive ceramic scaffold for bone regeneration: effective enhancement of mechanical and in vitro osteogenic properties towards load-bearing applications.

    Science.gov (United States)

    Li, Jiao Jiao; Roohani-Esfahani, Seyed-Iman; Kim, Kyungsook; Kaplan, David L; Zreiqat, Hala

    2017-06-01

    Bioactive ceramic scaffolds represent competitive choices for clinical bone reconstruction, but their widespread use is restricted by inherent brittleness and weak mechanical performance under load. This study reports the development of strong and tough bioactive scaffolds suitable for use in load-bearing bone reconstruction. A strong and bioactive ceramic scaffold (strontium-hardystonite-gahnite) is combined with single and multiple coating layers of silk fibroin to enhance its toughness, producing composite scaffolds which match the mechanical properties of cancellous bone and show enhanced capacity to promote in vitro osteogenesis. Also reported for the first time is a comparison of the coating effects obtained when a polymeric material is coated on ceramic scaffolds with differing microstructures, namely the strontium-hardystonite-gahnite scaffold with high-density struts as opposed to a conventional ceramic scaffold, such as biphasic calcium phosphate, with low-density struts. The results show that silk coating on a unique ceramic scaffold can lead to simple and effective enhancement of its mechanical and biological properties to suit a wider range of applications in clinical bone reconstruction, and also establish the influence of ceramic microstructure on the effectiveness of silk coating as a method of reinforcement when applied to different types of ceramic bone graft substitutes. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  14. Immediate loading and customized restoration of a single implant in the maxillary esthetic zone : A clinical report

    NARCIS (Netherlands)

    den Hartog, Laurens; Raghoebar, Gerry M.; Stellingsma, Kees; Meijer, Henny J. A.

    2009-01-01

    The replacement of a single missing anterior tooth with an implant-supported crown Is a demanding therapy. This report describes a treatment in which an anterior maxillary implant was immediately restored with a provisional restoration. During the provisional phase, an optimal emergence profile was

  15. A load-displacement based approach to assess the bearing capacity and deformations of mono-bucket foundations

    DEFF Research Database (Denmark)

    Vahdatirad, Mohammadjavad; Diaz, Alberto Troya; Nielsen, Søren

    2016-01-01

    It is now accepted that a larger effort must be made in order to optimize the design so that offshore wind turbines can be competitive with the other energy resources. In this regard, mono-buckets are known as a cost-effective offshore foundation solution. In the current study, a load–displacemen......It is now accepted that a larger effort must be made in order to optimize the design so that offshore wind turbines can be competitive with the other energy resources. In this regard, mono-buckets are known as a cost-effective offshore foundation solution. In the current study, a load...... and run the calculations is proposed. The model is validated, and its accuracy is analyzed, by comparison with field test results for a bucket foundation installed in silty, sandy soil....

  16. Clinical performance of provisional screw-retained metal-free acrylic restorations in an immediate loading implant protocol: a 242 consecutive patients' report.

    Science.gov (United States)

    Suarez-Feito, Jose-María; Sicilia, Alberto; Angulo, Jorge; Banerji, Subir; Cuesta, Isabel; Millar, Brian

    2010-12-01

    To evaluate the clinical performance of provisional screw-retained metal-free acrylic restorations in an immediate loading implant protocol. Two hundred and forty-two consecutive patients were selected retrospectively, who received 1011 implants and 311 immediate provisional screw-retained implant restorations (2-4 h after implant surgery). The patients were monitored for a period of 2-3 months, until they were referred for a final restoration. The primary variables recorded include the survival time and the appearance of fractures in the provisional restoration, and the independent variables included age, sex, dental arch, type of restoration, type of attachment and components used, as well as cantilevers and opposing dentition. A survival analysis (Kaplan-Meier) and a Cox regression analysis were performed. Twenty-three restorations in 20 patients (8.26%, 95% CI 4.8-11.7) showed at least one fracture (7.39%). More than half of the new fractures (52%, 12 cases) occurred in the first 4 weeks. The cumulative survival probability observed was greater in mandible (P=0.05) and non-cantilever restorations (P=0.001), and in those opposed by full restorations or natural teeth (P=0.001). With an opposing implant-supported prosthesis, the risk of fracture was multiplied by 4.7, and the use of cantilevers as well as the location of the restoration in the maxilla multiply the risk by 3.4-3.5. Immediate provisional screw-retained metal-free implant-supported restorations can be considered a reliable restoration (92.6% remain intact) for the healing period of 3 months. © 2010 John Wiley & Sons A/S.

  17. A doxycycline-loaded polymer-lipid encapsulation matrix coating for the prevention of implant-related osteomyelitis due to doxycycline-resistant methicillin-resistant Staphylococcus aureus.

    Science.gov (United States)

    Metsemakers, Willem-Jan; Emanuel, Noam; Cohen, Or; Reichart, Malka; Potapova, Inga; Schmid, Tanja; Segal, David; Riool, Martijn; Kwakman, Paulus H S; de Boer, Leonie; de Breij, Anna; Nibbering, Peter H; Richards, R Geoff; Zaat, Sebastian A J; Moriarty, T Fintan

    2015-07-10

    Implant-associated bone infections caused by antibiotic-resistant pathogens pose significant clinical challenges to treating physicians. Prophylactic strategies that act against resistant organisms, such as methicillin-resistant Staphylococcus aureus (MRSA), are urgently required. In the present study, we investigated the efficacy of a biodegradable Polymer-Lipid Encapsulation MatriX (PLEX) loaded with the antibiotic doxycycline as a local prophylactic strategy against implant-associated osteomyelitis. Activity was tested against both a doxycycline-susceptible (doxy(S)) methicillin-susceptible S. aureus (MSSA) as well as a doxycycline-resistant (doxy(R)) methicillin-resistant S. aureus (MRSA). In vitro elution studies revealed that 25% of the doxycycline was released from the PLEX-coated implants within the first day, followed by a 3% release per day up to day 28. The released doxycycline was highly effective against doxy(S) MSSA for at least 14days in vitro. A bolus injection of doxycycline mimicking a one day release from the PLEX-coating reduced, but did not eliminate, mouse subcutaneous implant-associated infection (doxy(S) MSSA). In a rabbit intramedullary nail-related infection model, all rabbits receiving a PLEX-doxycycline-coated nail were culture negative in the doxy(S) MSSA-group and the surrounding bone displayed a normal physiological appearance in both histological sections and radiographs. In the doxy(R) MRSA inoculated rabbits, a statistically significant reduction in the number of culture-positive samples was observed for the PLEX-doxycycline-coated group when compared to the animals that had received an uncoated nail, although the reduction in bacterial burden did not reach statistical significance. In conclusion, the PLEX-doxycycline coating on titanium alloy implants provided complete protection against implant-associated MSSA osteomyelitis, and resulted in a significant reduction in the number of culture positive samples when challenged with a

  18. Bearing system

    Science.gov (United States)

    Kapich, Davorin D.

    1987-01-01

    A bearing system includes backup bearings for supporting a rotating shaft upon failure of primary bearings. In the preferred embodiment, the backup bearings are rolling element bearings having their rolling elements disposed out of contact with their associated respective inner races during normal functioning of the primary bearings. Displacement detection sensors are provided for detecting displacement of the shaft upon failure of the primary bearings. Upon detection of the failure of the primary bearings, the rolling elements and inner races of the backup bearings are brought into mutual contact by axial displacement of the shaft.

  19. The effect of load on heat production, thermal effects and expenditure of time during implant site preparation - an experimental ex vivo comparison between piezosurgery and conventional drilling.

    Science.gov (United States)

    Stelzle, Florian; Frenkel, Carsten; Riemann, Max; Knipfer, Christian; Stockmann, Philipp; Nkenke, Emeka

    2014-02-01

    Piezoelectric surgery (PS) is meant to be a gentle osteotomy method. The aim of this study was to compare piezosurgical vs. conventional drilling methods for implant site preparation (ISP) - focusing on load-dependent thermal effect on hard tissue and the expenditure of ISP time. Three hundred and sixty ISP were performed on ex vivo pig heads using piezosurgery, spiral burs (SB) and trephine burs (TB). The load applied was increased from 0 to 1000 g in 100-g intervals. Temperature within the bone was measured with a thermocouple, and duration was recorded with a stop watch. Thermal effects were histomorphometrically analysed. Twelve ISPs per technique were performed at the lateral wall of the maxillary sinus. PS yields the highest mean temperatures (48.6 ± 3.4°C) and thermal effects (200.7 ± 44.4 μm), both at 900-1000 g. Duration is reduced with a plus of load and significantly longer in either case for PS (P < 0.05). There is a correlation of the applied load with all other examined factors for PS and TB. Temperature and histological effects decrease for SB beyond 500 g. PS yields significantly higher temperatures and thermal tissue alterations on load levels higher than 500 g and is significantly slower for ISP compared to SB and TB. For ISP with PS, a maximum load of 400 g should be maintained. © 2012 John Wiley & Sons A/S.

  20. Long-Term Retrospective Clinical and Radiographic Follow-up of 205 Brånemark System Mk III TiUnite Implants Submitted to Either Immediate or Delayed Loading.

    Science.gov (United States)

    Imburgia, Mario; Del Fabbro, Massimo

    2015-10-01

    Studies are needed to evaluate long-term performance of immediately loaded implants with moderately rough surface. This retrospective study evaluated long-term survival and periimplant soft and hard tissue conditions in patients treated with TiUnite implants. Forty-one consecutive patients (mean age, 52.6 years) received 205 Brånemark System Mk III TiUnite implants (145 maxillary, 60 mandibular). The indication was single tooth (n = 7 implants), partial (n = 94), or full arches (n = 104). One hundred thirteen implants were immediately loaded. Cumulative survival rate (CSR) of implants was assessed. Long-term marginal bone remodeling, probing pocket depth (PPD), and periimplant mucosa conditions were assessed. Follow-up averaged 8.8 years (range, 6.6-10.6 years). Eight implants in 5 patients failed. CSR was 96.1% (implant basis) and 87.8% (patient basis) up to 10 years. At the longest follow-up, bone loss averaged 0.43 ± 1.15 mm (n = 173), PPD averaged 3.64 ± 0.74 mm, and periimplant mucosa was healthy in 74.6% of cases. Furthermore, 50.3% and 35.5% of implants scored negative for plaque and bleeding, respectively. No significant difference in CSR and hard and soft tissue conditions was found in the long term between immediately and delayed loaded implants. Implants with TiUnite surface demonstrated excellent long-term survival, marginal bone response, and soft tissue conditions, despite a nonoptimal level of oral hygiene.

  1. Surface Engineering for Bone Implants: A Trend from Passive to Active Surfaces

    Directory of Open Access Journals (Sweden)

    John Jansen

    2012-07-01

    Full Text Available The mechanical and biological properties of bone implants need to be optimal to form a quick and firm connection with the surrounding environment in load bearing applications. Bone is a connective tissue composed of an organic collagenous matrix, a fine dispersion of reinforcing inorganic (calcium phosphate nanocrystals, and bone-forming and -degrading cells. These different components have a synergistic and hierarchical structure that renders bone tissue properties unique in terms of hardness, flexibility and regenerative capacity. Metallic and polymeric materials offer mechanical strength and/or resilience that are required to simulate bone tissue in load-bearing applications in terms of maximum load, bending and fatigue strength. Nevertheless, the interaction between devices and the surrounding tissue at the implant interface is essential for success or failure of implants. In that respect, coatings can be applied to facilitate the process of bone healing and obtain a continuous transition from living tissue to the synthetic implant. Compounds that are inspired by inorganic (e.g., hydroxyapatite crystals or organic (e.g., collagen, extracellular matrix components, enzymes components of bone tissue, are the most obvious candidates for application as implant coating to improve the performance of bone implants. This review provides an overview of recent trends and strategies in surface engineering that are currently investigated to improve the biological performance of bone implants in terms of functionality and biological efficacy.

  2. Comparison of Different Assembling Techniques Regarding Cost, Durability, and Ecology - A Survey of Multi-layer Wooden Panel Assembly Load-Bearing Construction Elements

    Directory of Open Access Journals (Sweden)

    Dietrich Buck

    2015-10-01

    Full Text Available Wood is a pure, sustainable, renewable material. The increasing use of wood for construction can improve its sustainability. There are various techniques to assemble multi-layer wooden panels into prefabricated, load-bearing construction elements. However, comparative market and economy studies are still scarce. In this study, the following assembling techniques were compared: laminating, nailing, stapling, screwing, stress laminating, doweling, dovetailing, and wood welding. The production costs, durability, and ecological considerations were presented. This study was based on reviews of published works and information gathered from 27 leading wood product manufacturing companies in six European countries. The study shows that the various techniques of assembling multi-layer wooden construction panel elements are very different. Cross laminated timber (CLT exhibited the best results in terms of cost and durability. With regard to ecological concerns, dovetailing is the best. Taking into account both durability and ecological considerations, wooden screw-doweling is the best. These alternatives give manufacturers some freedom of choice regarding the visibility of surfaces and the efficient use of lower-quality timber. CLT is the most cost-effective, is not patented, and is a well-established option on the market today.

  3. Efficacy of standard (SLA) and modified sandblasted and acid-etched (SLActive) dental implants in promoting immediate and/or early occlusal loading protocols: a systematic review of prospective studies.

    Science.gov (United States)

    Chambrone, Leandro; Shibli, Jamil Awad; Mercúrio, Carlos Eduardo; Cardoso, Bruna; Preshaw, Philip M

    2015-04-01

    To assess the survival percentage, clinical and radiographic outcomes of sandblasted and acid-etched (SLA) dental implants and its modified surface (SLActive) in protocols involving immediate and early occlusal loading. MEDLINE, EMBASE and the Cochrane Oral Health Group's Trials Register CENTRAL were searched in duplicate up to, and including, June 2013 to include randomised controlled trials (RCTs) and prospective observational studies of at least 6-month duration published in all languages. Studies limited to patients treated with SLA and/or SLActive implants involving a treatment protocol describing immediate and early loading of these implants were eligible for inclusion. Data on clinical and/or radiographic outcomes following implant placement were considered for inclusion. Of the 447 potentially eligible publications identified by the search strategy, seven RCTs comprising a total of 853 implants (8% titanium plasma-sprayed, 41.5% SLA and 50.5% SLActive) and 12 prospective observational studies including 1394 SLA and 145 SLActive implants were included in this review. According to the Cochrane Collaboration's tool for assessing risk of bias, one of the studies was considered to be at a low risk of bias, whereas the remaining studies were considered to be at an unclear risk. Regarding the observational studies, all of them presented a medium methodological quality based on the Modified Newcastle-Ottawa scale. There were no significant differences reported in the studies in relation to implant loss or clinical parameters between the immediate/early loading and delayed loading protocols. Overall, 95% of SLA and 97% of SLActive implants still survive at the end of follow-up. Despite of the positive findings achieved by the included studies, few RCTs were available for analysis for SLActive implants. Study heterogeneity, scarcity of data and the lack of pooled estimates represent a limitation between studies' comparisons and should be considered when interpreting

  4. A comparative study of the effectiveness of early and delayed loading of short tissue-level dental implants with hydrophilic surfaces placed in the posterior section of the mandible-A preliminary study.

    Science.gov (United States)

    Makowiecki, Arkadiusz; Botzenhart, Ute; Seeliger, Julia; Heinemann, Friedhelm; Biocev, Peter; Dominiak, Marzena

    2017-07-01

    The objective of the present study was to compare the primary and secondary stability of tissue-level short dental titanium implants with polished necks and hydrophilic surfaces of two different designs and manufacturers. The first implant system used (SPI ® ELEMENT RC INICELL titanium implants, Thommen Medical AG, Grenchen, Switzerland), allowed functional loading 6 weeks after its placement, whereas the second implant system (RN SLActiv ® tissue-level titanium implants, Straumann GmbH, Fribourg, Germany), was loaded after 15 weeks. The degree of primary and secondary stability was determined using an Osstell ISQ measuring device. Marginal bone loss (MBL) was evaluated radiographically 12 and 24 weeks after implantation and the Wachtel's healing index as well as the patient's satisfaction with the treatment was registered on a VAS scale. The intergroup comparison revealed significant differences in terms of primary stability as well as differences in MBL 3 months after the procedure, but no significant differences could be found after 6 months and for secondary stability. The primary stability was significantly higher for Thommen ® compared to Straumann ® implants. Insertion of short dental implants with a hydrophilic conditioned surface significantly shortens patient treatment time. Copyright © 2017 Elsevier GmbH. All rights reserved.

  5. Magnesium as a biodegradable and bioabsorbable material for medical implants

    Science.gov (United States)

    Brar, Harpreet S.; Platt, Manu O.; Sarntinoranont, Malisa; Martin, Peter I.; Manuel, Michele V.

    2009-09-01

    For many years, stainless steel, cobalt-chromium, and titanium alloys have been the primary biomaterials used for load-bearing applications. However, as the need for structural materials in temporary implant applications has grown, materials that provide short-term structural support and can be reabsorbed into the body after healing are being sought. Since traditional metallic biomaterials are typically biocompatible but not biodegradable, the potential for magnesium-based alloys in biomedical applications has gained more interest. This paper summarizes the history and current status of magnesium as a bioabsorbable implant material. Also discussed is the development of a magnesium-zinc-calcium alloy that demonstrates promising degradation behavior.

  6. Roller bearing geometry design

    Science.gov (United States)

    Savage, M.; Pinkston, B. H. W.

    1976-01-01

    A theory of kinematic stabilization of rolling cylinders is extended and applied to the design of cylindrical roller bearings. The kinematic stabilization mechanism puts a reverse skew into the rolling elements by changing the roller taper. Twelve basic bearing modification designs are identified amd modeled. Four have single transverse convex curvature in their rollers while eight have rollers which have compound transverse curvature made up of a central cylindrical band surrounded by symmetric bands with slope and transverse curvature. The bearing designs are modeled for restoring torque per unit axial displacement, contact stress capacity, and contact area including dynamic loading, misalignment sensitivity and roller proportion. Design programs are available which size the single transverse curvature roller designs for a series of roller slopes and load separations and which design the compound roller bearings for a series of slopes and transverse radii of curvature. The compound rollers are proportioned to have equal contact stresses and minimum size. Design examples are also given.

  7. Finite Element Analysis of the Effect of Superstructure Materials and Loading Angle on Stress Distribution around the Implant

    Directory of Open Access Journals (Sweden)

    Jafari K

    2014-12-01

    Full Text Available Statement of Problem: A general process in implant design is to determine the reason of possible problems and to find the relevant solutions. The success of the implant depends on the control technique of implant biomechanical conditions. Objectives: The goal of this study was to evaluate the influence of both abutment and framework materials on the stress of the bone around the implant by using threedimensional finite element analysis. Materials and Methods: A three-dimensional model of a patient’s premaxillary bone was fabricated using Cone Beam Computed Tomography (CBCT. Then, three types of abutment from gold, nickel-chromium and zirconia and also three types of crown frame from silver-palladium, nickel-chromium and zirconia were designed. Finally, a 178 N force at angles of zero, 30 and 45 degrees was exerted on the implant axis and the maximum stress and strain in the trabecular, cortical bones and cement was calculated. Results: With changes of the materials and mechanical properties of abutment and frame, little difference was observed in the level and distribution pattern of stress. The stress level was increased with the rise in the angle of pressure exertion. The highest stress concentration was related to the force at the angle of 45 degrees. The results of the cement analysis proved an inverse relationship between the rate of elastic modulus of the frame material and that of the maximum stress in the cement. Conclusions: The impact of the angle at which the force was applied was more significant in stress distribution than that of abutment and framework core materials.

  8. Gear bearing drive

    Science.gov (United States)

    Mavroidis, Constantinos (Inventor); Vranish, John M. (Inventor); Weinberg, Brian (Inventor)

    2011-01-01

    A gear bearing drive provides a compact mechanism that operates as an actuator providing torque and as a joint providing support. The drive includes a gear arrangement integrating an external rotor DC motor within a sun gear. Locking surfaces maintain the components of the drive in alignment and provide support for axial loads and moments. The gear bearing drive has a variety of applications, including as a joint in robotic arms and prosthetic limbs.

  9. Antitumor effect of free rhodium (II) citrate and rhodium (II) citrate-loaded maghemite nanoparticles on mice bearing breast cancer: a systemic toxicity assay.

    Science.gov (United States)

    Peixoto, Raphael Cândido Apolinário; Miranda-Vilela, Ana Luisa; de Souza Filho, José; Carneiro, Marcella Lemos' Brettas; Oliveira, Ricardo G S; da Silva, Matheus Oliveira; de Souza, Aparecido R; Báo, Sônia Nair

    2015-05-01

    Breast cancer is one of the most prevalent cancer types among women. The use of magnetic fluids for specific delivery of drugs represents an attractive platform for chemotherapy. In our previous studies, it was demonstrated that maghemite nanoparticles coated with rhodium (II) citrate (Magh-Rh2Cit) induced in vitro cytotoxicity and in vivo antitumor activity, followed by intratumoral administration in breast carcinoma cells. In this study, our aim was to follow intravenous treatment to evaluate the systemic antitumor activity and toxicity induced by these formulations in Balb/c mice bearing orthotopic 4T1 breast carcinoma. Female Balb/c mice were evaluated with regard to toxicity of intravenous treatments through analyses of hemogram, serum levels of alanine aminotransferase, iron, and creatinine and liver, kidney, and lung histology. The antitumor activity of rhodium (II) citrate (Rh2Cit), Magh-Rh2Cit, and maghemite nanoparticles coated with citrate (Magh-Cit), used as control, was evaluated by tumor volume reduction, histology, and morphometric analysis. Magh-Rh2Cit and Magh-Cit promoted a significant decrease in tumor area, and no experimental groups presented hematotoxic effects or increased levels of serum ALT and creatinine. This observation was corroborated by the histopathological examination of the liver and kidney of mice. Furthermore, the presence of nanoparticles was verified in lung tissue with no morphological changes, supporting the idea that our nanoformulations did not induce toxicity effects. No studies about the systemic action of rhodium (II) citrate-loaded maghemite nanoparticles have been carried out, making this report a suitable starting point for exploring the therapeutic potential of these compounds in treating breast cancer.

  10. Hydrostatic and hybrid bearing design

    CERN Document Server

    Rowe, W B

    1983-01-01

    Hydrostatic and Hybrid Bearing Design is a 15-chapter book that focuses on the bearing design and testing. This book first describes the application of hydrostatic bearings, as well as the device pressure, flow, force, power, and temperature. Subsequent chapters discuss the load and flow rate of thrust pads; circuit design, flow control, load, and stiffness; and the basis of the design procedures and selection of tolerances. The specific types of bearings, their design, dynamics, and experimental methods and testing are also shown. This book will be very valuable to students of engineering des

  11. Plasma immersion ion implantation: duplex layers from a single process

    International Nuclear Information System (INIS)

    Hutchings, R.; Collins, G.A.; Tendys, J.

    1992-01-01

    Plasma immersion ion implantation (PI 3 ) is an alternative non-line-of-sight technique for implanting ions directly from a plasma which surrounds the component to be treated. In contrast to plasma source ion implantation, the PI 3 system uses an inductively coupled r.f. plasma. It is shown that nitrogen can be retained during implantation at elevated temperatures, even for unalloyed steels. This allows controlled diffusion of nitrogen to greater depths, thereby improving the load bearing capacity of the implanted layer. Components can be heated directly, using the energy deposited by the incident ions during the pulsed implantation. The necessary temperature control can be accomplished simply by regulating the frequency and length of the high voltage pulses applied to the component. Chemical depth profiles and microstructural data obtained from H13 tool steel are used to show that PI 3 can, in a single process, effectively produce a duplex subsurface structure. This structure consists of an outer non-equilibrium layer typical of nitrogen implantation (containing in excess of 20 at.% nitrogen) backed by a substantial diffusion zone of much lower nitrogen content. The relationship between implantation temperature and the resultant subsurface microstructure is explored. (orig.)

  12. A glass fiber-reinforced composite - bioactive glass cranioplasty implant: A case study of an early development stage implant removed due to a late infection.

    Science.gov (United States)

    Posti, Jussi P; Piitulainen, Jaakko M; Hupa, Leena; Fagerlund, Susanne; Frantzén, Janek; Aitasalo, Kalle M J; Vuorinen, Ville; Serlo, Willy; Syrjänen, Stina; Vallittu, Pekka K

    2015-03-01

    This case study describes the properties of an early development stage bioactive glass containing fiber-reinforced composite calvarial implant with histology that has been in function for two years and three months. The patient is a 33-year old woman with a history of substance abuse, who sustained a severe traumatic brain injury later unsuccessfully treated with an autologous bone flap and a custom-made porous polyethylene implant. She was thereafter treated with developmental stage glass fiber-reinforced composite - bioactive glass implant. After two years and three months, the implant was removed due to an implant site infection. The implant was analyzed histologically, mechanically, and in terms of chemistry and dissolution of bioactive glass. Mechanical integrity of the load bearing fiber-reinforced composite part of the implant was not affected by the in vivo period. Bioactive glass particles demonstrated surface layers of hydroxyapatite like mineral and dissolution, and related increase of pH was considerably less after two and three months period than that for fresh bioactive glass. There was a difference in the histology of the tissues inside the implant areas near to the margin of the implant that absorbed blood during implant installation surgery, showed fibrous tissue with blood vessels, osteoblasts, collagenous fibers with osteoid formation, and tiny clusters of more mature hard tissue. In the center of the implant, where there was less absorbed blood, only fibrous tissue was observed. This finding is in line with the combined positron emission tomography - computed tomography examination with (18F)-fluoride marker, which demonstrated activity of the mineralizing bone by osteoblasts especially at the area near to the margin of the implant 10 months after implantation. Based on these promising reactions found in the bioactive glass containing fiber-reinforced composite implant that has been implanted for two years and three months, calvarial

  13. Nanotubular surface modification of metallic implants via electrochemical anodization technique.

    Science.gov (United States)

    Wang, Lu-Ning; Jin, Ming; Zheng, Yudong; Guan, Yueping; Lu, Xin; Luo, Jing-Li

    2014-01-01

    Due to increased awareness and interest in the biomedical implant field as a result of an aging population, research in the field of implantable devices has grown rapidly in the last few decades. Among the biomedical implants, metallic implant materials have been widely used to replace disordered bony tissues in orthopedic and orthodontic surgeries. The clinical success of implants is closely related to their early osseointegration (ie, the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant), which relies heavily on the surface condition of the implant. Electrochemical techniques for modifying biomedical implants are relatively simple, cost-effective, and appropriate for implants with complex shapes. Recently, metal oxide nanotubular arrays via electrochemical anodization have become an attractive technique to build up on metallic implants to enhance the biocompatibility and bioactivity. This article will thoroughly review the relevance of electrochemical anodization techniques for the modification of metallic implant surfaces in nanoscale, and cover the electrochemical anodization techniques used in the development of the types of nanotubular/nanoporous modification achievable via electrochemical approaches, which hold tremendous potential for bio-implant applications. In vitro and in vivo studies using metallic oxide nanotubes are also presented, revealing the potential of nanotubes in biomedical applications. Finally, an outlook of future growth of research in metallic oxide nanotubular arrays is provided. This article will therefore provide researchers with an in-depth understanding of electrochemical anodization modification and provide guidance regarding the design and tuning of new materials to achieve a desired performance and reliable biocompatibility.

  14. Femoral fracture repair using a locking plate technique in an adult captive polar bear (Ursus maritimus).

    Science.gov (United States)

    Zimmerman, Dawn M; Dew, Terry; Douglass, Michael; Perez, Edward

    2010-02-01

    To report successful femoral fracture repair in a polar bear. Case report. Female polar bear (Ursus maritimus) 5 years and approximately 250 kg. A closed, complete, comminuted fracture of the distal midshaft femur was successfully reduced and stabilized using a compression plating technique with 2 specialized human femur plates offering axial, rotational, and bending support, and allowing the bone to share loads with the implant. Postoperative radiographs were obtained at 11.5 weeks, 11 months, and 24 months. Bone healing characterized by marked periosteal reaction was evident at 11 months with extensive remodeling evident at 24 months. No complications were noted. Distal mid shaft femoral fracture was reduced, stabilized, and healed in an adult polar bear with a locking plate technique using 2 plates. Previously, femoral fractures in polar bears were considered irreparable. Use of 2 plates applied with a locking plate technique can result in successful fracture repair despite large body weight and inability to restrict postoperative activity.

  15. Immediate occlusal loading of single lower molars using Brånemark System® Wide Platform TiUnite™ implants: a 5-year follow-up report of a prospective clinical multicenter study.

    Science.gov (United States)

    Calandriello, Roberto; Tomatis, Massimiliano

    2011-12-01

    Although not essential, molars hold their importance in terms of functional jaw stability, antagonist opposition, and support of facial height. Therefore, implant therapy is an attractive concept in molar areas. However, especially in the posterior mandible, the conventional two-stage surgical approach to implant therapy was reported to cause higher bone loss and/or higher implant failures with machined implants because of the peculiar anatomic and physiologic conditions of this area. As the TiUnite™ (Nobel Biocare AB, Göteborg, Sweden) surface results in faster bone healing than with machined-surface implants, it was hypothesized that this surface would also improve the performance of wide implants in posterior mandibles. Based on these assumptions, a protocol for immediately loaded implants for single molar replacement was developed. This paper aimed to report on the clinical and radiological performance of Brånemark System® TiUnite Wide Platform implants supporting single molars in the lower jaw, loaded immediately and followed for up to 5 years, and to assess if the benefit delivered by oxidized surfaces in the short run is also present after 5 years. The study includes 33 consecutive patients treated between March 2001 and September 2003 and monitored until September 2008 in two private dental offices. A total of 40 Brånemark System TiUnite Wide Platform MK III implants were placed. All implants were provided with provisional crowns in full centric occlusion at the time of surgery. Patients were clinically and radiologically followed up for up to 5 years. Two implant failed so that the cumulative success rate at 5 years was 95.0%. The mean marginal bone remodeling (n = 38) expressed as mesial plus distal value averages was -1.17 mm (SD ± 0.90) at the 5-year time point. Although limited by the number of patients treated in accordance with the protocol described, 5-year results encourage the use of immediately loaded single lower molars supported by Br

  16. Estimating Wear Of Installed Ball Bearings

    Science.gov (United States)

    Keba, John E.; Mcvey, Scott E.

    1993-01-01

    Simple inspection and measurement technique makes possible to estimate wear of balls in ball bearing, without removing bearing from shaft on which installed. To perform measurement, one observes bearing cage while turning shaft by hand to obtain integral number of cage rotations and to measure, to nearest 2 degrees, number of shaft rotations producing cage rotations. Ratio between numbers of cages and shaft rotations depends only on internal geometry of bearing and applied load. Changes in turns ratio reflect changes in internal geometry of bearing provided measurements made with similar bearing loads. By assuming all wear occurs on balls, one computes effective value for this wear from change in turns ratio.

  17. Ball Bearing Analysis with the ORBIS Tool

    Science.gov (United States)

    Halpin, Jacob D.

    2016-01-01

    Ball bearing design is critical to the success of aerospace mechanisms. Key bearing performance parameters, such as load capability, stiffness, torque, and life all depend on accurate determination of the internal load distribution. Hence, a good analytical bearing tool that provides both comprehensive capabilities and reliable results becomes a significant asset to the engineer. This paper introduces the ORBIS bearing tool. A discussion of key modeling assumptions and a technical overview is provided. Numerous validation studies and case studies using the ORBIS tool are presented. All results suggest the ORBIS code closely correlates to predictions on bearing internal load distributions, stiffness, deflection and stresses.

  18. Journal bearing

    Science.gov (United States)

    Menke, John R.; Boeker, Gilbert F.

    1976-05-11

    1. An improved journal bearing comprising in combination a non-rotatable cylindrical bearing member having a first bearing surface, a rotatable cylindrical bearing member having a confronting second bearing surface having a plurality of bearing elements, a source of lubricant adjacent said bearing elements for supplying lubricant thereto, each bearing element consisting of a pair of elongated relatively shallowly depressed surfaces lying in a cylindrical surface co-axial with the non-depressed surface and diverging from one another in the direction of rotation and obliquely arranged with respect to the axis of rotation of said rotatable member to cause a flow of lubricant longitudinally along said depressed surfaces from their distal ends toward their proximal ends as said bearing members are rotated relative to one another, each depressed surface subtending a radial angle of less than 360.degree., and means for rotating said rotatable bearing member to cause the lubricant to flow across and along said depressed surfaces, the flow of lubricant being impeded by the non-depressed portions of said second bearing surface to cause an increase in the lubricant pressure.

  19. Oral Health-related quality of life and clinical outcomes of immediately or delayed loaded implants in the rehabilitation of edentulous jaws: a retrospective comparative study.

    Science.gov (United States)

    Cosola, Saverio; Marconcini, Simone; Giammarinaro, Enrica; Poli, Gian L; Covani, Ugo; Barone, Antonio

    2018-04-16

    Patient-centred outcomes are being given great attention by the dental scientific community. The Oral Health Impact Profile -14 questionnaire (OHIP-14) has been introduced to address patients' success criteria when describing the impact of oral rehabilitations on quality of life (OHrQoL). Thirty-five patients wearing a full-arch implant-prosthesis being in place between 4 and 6 years before this analysis were considered eligible and then enrolled in the present retrospective study. According to their prosthetic anamnesis, two groups were defined: delayed loading group (IL-group) and immediate loading group (IL-group). At the moment of analysis, clinical and radiographic parameters were collected, and patients were asked to complete the Oral Health Impact Profile -14 questionnaire (OHIP-14) in order to measure their OHrQoL. Independent t-test showed total OHIP-14 scores to be not significantly different between groups; however, the domains "Functional limitation" and "physical disability" resulted significantly higher in patients within the DL-group. On the contrary, social disability was higher in the IL-group. When the comparison was performed taking sex into account, no significant differences between groups were highlighted. Instead, the stratification for years of follow-up led to significant evidences. When the follow-up was shorter (less-than-5 years), the functional limitation reported scores were higher. Within the limitations of this study, the analysis supports the absence of significant differences between immediate loading and delayed loading full-arch protocol in term of clinical, radiological parameters and OHrQoL.

  20. Optimization of cell adhesion on mg based implant materials by pre-incubation under cell culture conditions.

    Science.gov (United States)

    Willumeit, Regine; Möhring, Anneke; Feyerabend, Frank

    2014-05-05

    Magnesium based implants could revolutionize applications where orthopedic implants such as nails, screws or bone plates are used because they are load bearing and degrade over time. This prevents a second surgery to remove conventional implants. To improve the biocompatibility we studied here if and for how long a pre-incubation of the material under cell culture conditions is favorable for cell attachment and proliferation. For two materials, Mg and Mg10Gd1Nd, we could show that 6 h pre-incubation are already enough to form a natural protective layer suitable for cell culture.

  1. Optimization of Cell Adhesion on Mg Based Implant Materials by Pre-Incubation under Cell Culture Conditions

    Directory of Open Access Journals (Sweden)

    Regine Willumeit

    2014-05-01

    Full Text Available Magnesium based implants could revolutionize applications where orthopedic implants such as nails, screws or bone plates are used because they are load bearing and degrade over time. This prevents a second surgery to remove conventional implants. To improve the biocompatibility we studied here if and for how long a pre-incubation of the material under cell culture conditions is favorable for cell attachment and proliferation. For two materials, Mg and Mg10Gd1Nd, we could show that 6 h pre-incubation are already enough to form a natural protective layer suitable for cell culture.

  2. Microbiological outcome of two screw-shaped titanium implant systems placed following a split-mouth randomised protocol, at the 12th year of follow-up after loading.

    Science.gov (United States)

    Van Assche, Nele; Pittayapat, Pisha; Jacobs, Reinhilde; Pauwels, Martine; Teughels, Wim; Quirynen, Marc

    2011-01-01

    To compare the subgingival microbiota around two differently designed implant systems that were in function for more than 12 years in a randomised split-mouth study design, and to compare the outcome with natural dentition. A total of 18 partially edentulous patients received at least two TiOblast™ (Astra Tech) and two Brånemark (Nobel Biocare) implants following a split-mouth design. At the last follow-up visit, periodontal parameters (probing depth, bleeding on probing and plaque) were recorded and intraoral radiographs were taken to calculate bone loss. Subgingival plaque samples were collected for culture, qPCR and checkerboard DNA-DNA hybridisation analysis. These data were related to implant design and bone loss. This study setup allowed a comparison of 34 Astra Tech (Impl A) with 32 Brånemark (Impl B) implants. During the 12-year follow up, five patients dropped out. One Brånemark implant was lost before abutment connection in a dropout patient. Mean bone loss between loading and year 12 was 0.7 mm (range: -0.8-5.8) (Impl A), and 0.4 mm (range: -1.1-4.1) (Impl B). No significant microbiological differences (qualitative and quantitative) could be observed between both implant types. Compared to teeth, subgingival plaque samples from implants did not reach the concentration of pathogens, even after 12 years of function. These data show that both implant systems (with differences in macro-design and surface characteristics), in patients with good oral hygiene and a stable periodontal condition, can maintain a successful treatment outcome without significant subgingival microbiological differences after 12 years of loading. The presence of periodontopathogens did not necessarily result in bone loss.

  3. Effect of Integration Patterns Around Implant Neck on Stress Distribution in Peri-Implant Bone: A Finite Element Analysis.

    Science.gov (United States)

    Han, Jingyun; Sun, Yuchun; Wang, Chao

    2017-08-01

    To investigate the biomechanical performance of different osseointegration patterns between cortical bone and implants using finite element analysis. Fifteen finite element models were constructed of the mandibular fixed prosthesis supported by implants. Masticatory loads (200 N axial, 100 N oblique, 40 N horizontal) were applied. The cortical bone/implant interface was divided equally into four layers: upper, upper-middle, lower-middle, and lower. The bone stress and implant displacement were calculated for 5 degrees of uniform integration (0, 20%, 40%, 60%, and 100%) and 10 integration patterns. The stress was concentrated in the bone margin and gradually decreased as osseointegration progressed, when the integrated and nonintegrated areas were alternated on the bone-implant surface. Compared with full integration, the integration of only the lower-middle layer or lower half layers significantly decreased von Mises, tensile, and compressive stresses in cortical bone under oblique and horizontal loads, and these patterns did not induce higher stress in the cancellous bone. For the integration of only the upper or upper-middle layer, stress in the cortical and cancellous bones significantly increased and was considerably higher than in the case of nonintegration. In addition, the maximum stress in the cortical bone was sensitive to the quantity of integrated nodes at the bone margin; lower quantity was associated with higher stress. There was no significant difference in the displacement of implants among 15 models. Integration patterns of cortical bone significantly affect stress distribution in peri-implant bone. The integration of only the lower-middle or lower half layers helps to increase the load-bearing capacity of peri-implant bone and decrease the risk of overloading, while upper integration may further increase the risk of bone resorption. © 2016 by the American College of Prosthodontists.

  4. Biological Strategies for Improved Osseointegration and Osteoinduction of Porous Metal Orthopedic Implants

    Science.gov (United States)

    Riester, Scott M.; Bonin, Carolina A.; Kremers, Hilal Maradit; Dudakovic, Amel; Kakar, Sanjeev; Cohen, Robert C.; Westendorf, Jennifer J.

    2015-01-01

    The biological interface between an orthopedic implant and the surrounding host tissue may have a dramatic effect upon clinical outcome. Desired effects include bony ingrowth (osseointegration), stimulation of osteogenesis (osteoinduction), increased vascularization, and improved mechanical stability. Implant loosening, fibrous encapsulation, corrosion, infection, and inflammation, as well as physical mismatch may have deleterious clinical effects. This is particularly true of implants used in the reconstruction of load-bearing synovial joints such as the knee, hip, and the shoulder. The surfaces of orthopedic implants have evolved from solid-smooth to roughened-coarse and most recently, to porous in an effort to create a three-dimensional architecture for bone apposition and osseointegration. Total joint surgeries are increasingly performed in younger individuals with a longer life expectancy, and therefore, the postimplantation lifespan of devices must increase commensurately. This review discusses advancements in biomaterials science and cell-based therapies that may further improve orthopedic success rates. We focus on material and biological properties of orthopedic implants fabricated from porous metal and highlight some relevant developments in stem-cell research. We posit that the ideal primary and revision orthopedic load-bearing metal implants are highly porous and may be chemically modified to induce stem cell growth and osteogenic differentiation, while minimizing inflammation and infection. We conclude that integration of new biological, chemical, and mechanical methods is likely to yield more effective strategies to control and modify the implant–bone interface and thereby improve long-term clinical outcomes. PMID:25348836

  5. GAS BEARING

    Science.gov (United States)

    Skarstrom, C.W.

    1960-09-01

    A gas lubricated bearing for a rotating shaft is described. The assembly comprises a stationary collar having an annular member resiliently supported thereon. The collar and annular member are provided with cooperating gas passages arranged for admission of pressurized gas which supports and lubricates a bearing block fixed to the rotatable shaft. The resilient means for the annular member support the latter against movement away from the bearing block when the assembly is in operation.

  6. Grizzly bear

    Science.gov (United States)

    Schwartz, C.C.; Miller, S.D.; Haroldson, M.A.; Feldhamer, G.; Thompson, B.; Chapman, J.

    2003-01-01

    The grizzly bear inspires fear, awe, and respect in humans to a degree unmatched by any other North American wild mammal. Like other bear species, it can inflict serious injury and death on humans and sometimes does. Unlike the polar bear (Ursus maritimus) of the sparsely inhabited northern arctic, however, grizzly bears still live in areas visited by crowds of people, where presence of the grizzly remains physically real and emotionally dominant. A hike in the wilderness that includes grizzly bears is different from a stroll in a forest from which grizzly bears have been purged; nighttime conversations around the campfire and dreams in the tent reflect the presence of the great bear. Contributing to the aura of the grizzly bear is the mixture of myth and reality about its ferocity. unpredictable disposition, large size, strength, huge canines, long claws, keen senses, swiftness, and playfulness. They share characteristics with humans such as generalist life history strategies. extended periods of maternal care, and omnivorous diets. These factors capture the human imagination in ways distinct from other North American mammals. Precontact Native American legends reflected the same fascination with the grizzly bear as modern stories and legends (Rockwell 1991).

  7. The pre-calculation of the operating behaviour of axial sliding bearings at high circumferential speeds and high specific loads. Final report; Vorausberechnung des Betriebsverhaltens von Axialgleitlagern bei hohen Umfangsgeschwindigkeiten und hohen spezifischen Belastungen. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Glienicke, J.; Lindloff, K.; Medhioub, M.

    1997-12-31

    The reliable pre-calculation of the important axial bearing parameters is of decisive importance for the safe running of high speed rotors with high axial thrust. However, the computer programs available now contain simplified assumptions which can lead to considerable discrepancies between measured and calculated values at high speeds of sliding and high specific loads. By expanding the existing sliding bearing computer program, in which the exact segment geometry, the local lubricating film turbulence, the centrifugal forces and entry losses of the oil, the flow resistance, both incoming and outgoing, the thermal conduction in the tracking ring and the bearing, the thermal pocket mixing, the elastic and thermal segment deformation and the coupling of the lubrication films in double-acting axial bearings are now included, good agreement between measured and calculated results is obtained for all bearing shapes examined. (orig./AKF) [Deutsch] Fuer den betriebssicheren Lauf hochtouriger Rotoren mit hohem Axialschub ist die zuverlaessige Vorausberechnung der massgebenden Axiallager-Kennwerte von entscheidender Bedeutung. Die heute verfuegbaren Rechenprogramme enthalten jedoch vereinfachende Annahmen, die bei hohen Gleitgeschwindigkeiten und hohen spezifischen Belastungen zu wesentlichen Abweichungen zwischen Mess- und Rechenwerten fuehren koennen. Durch Erweiterung eines vorhandenen Gleitlager-Rechenprogramms, in dem nun die genaue Segmentgeometrie, die lokale Schmierfilmturbulenz, die Fliehkraefte und Eintrittsverluste des Oels, die Durchflusswiderstaende im Zu- und Abfluss, die Waermeleitung in Spurscheibe und Lager, die thermische Taschenmischung, die elastischen und thermischen Segmentverformungen und die Kopplung der Schmierfilme bei doppeltwirkenden Axiallagern erfasst werden, wird fuer alle untersuchten Lagerbauformen eine gute Uebereinstimmung von Mess- und Rechenwerten erreicht. (orig./AKF)

  8. Assessment of a polyelectrolyte multilayer film coating loaded with BMP-2 on titanium and PEEK implants in the rabbit femoral condyle

    Science.gov (United States)

    Guillot, R.; Pignot-Paintrand, I.; Lavaud, J.; Decambron, A.; Bourgeois, E.; Josserand, V.; Logeart-Avramoglou, D.; Viguier, E.; Picart, C.

    2016-01-01

    The aim of this study was to evaluate the osseointegration of titanium implants (Ti-6Al-4V, noted here TA6V) and poly(etheretherketone) PEEK implants induced by a BMP-2-delivering surface coating made of polyelectrolyte multilayer films. The in vitro bioactivity of the polyelectrolyte film-coated implants was assessed using the alkaline phosphatase assay. BMP-2-coated TA6V and PEEK implants with a total dose of 9.3 µg of BMP-2 were inserted into the femoral condyles of New Zealand white rabbits and compared to uncoated implants. Rabbits were sacrificed 4 and 8 weeks after implantation. Histomorphometric analyses on TA6V and PEEK implants and microcomputed tomography on PEEK implants revealed that the bone-to-implant contact and bone area around the implants were significantly lower for the BMP-2-coated implants than for the bare implants. This was confirmed by scanning electron microscopy imaging. This difference was more pronounced at 4 weeks in comparison to the 8-week time point. However, bone growth inside the hexagonal upper hollow cavity of the screws was higher in the case of the BMP-2 coated implants. Overall, this study shows that a high dose of BMP-2 leads to localized and temporary bone impairment, and that the dose of BMP-2 delivered at the surface of an implant needs to be carefully optimized. PMID:26965394

  9. DEVELOPMENT AND RESEARCH OF THE MODIFIED WHITE METAL MATERIAL WITH THE PURPOSE OF ITS USE AT REPAIR OF HEAVY-LOADED BEARINGS OF SLIPPING

    Directory of Open Access Journals (Sweden)

    A. V. Alifanov

    2012-01-01

    Full Text Available The paper shows that wear resistance of new modified babbit material (MBM is by an order of magnitude higher than that of the Б83 State Standard 1320-74 standard babbit material. Therefore, the latter can be recommended for restoration of sliding bearings that are used in gascompressor units.

  10. Influence of Palatal Coverage and Implant Distribution on Implant Strain in Maxillary Implant Overdentures.

    Science.gov (United States)

    Takahashi, Toshihito; Gonda, Tomoya; Mizuno, Yoko; Fujinami, Yozo; Maeda, Yoshinobu

    2016-01-01

    Maxillary implant overdentures are often used in clinical practice. However, there is no agreement or established guidelines regarding prosthetic design or optimal implant placement configuration. The purpose of this study was to examine the influence of palatal coverage and implant number and distribution in relation to impact strain under maxillary implant overdentures. A maxillary edentulous model with implants and experimental overdentures with and without palatal coverage was fabricated. Four strain gauges were attached to each implant, and they were positioned in the anterior, premolar, and molar areas. A vertical occlusal load of 98 N was applied through a mandibular complete denture, and the implant strains were compared using one-way analysis of variance (P = .05). The palatolabial strain was much higher on anterior implants than on other implants in both denture types. Although there was no significant difference between the strain under dentures with and without palatal coverage, palateless dentures tended to result in higher implant strain than dentures with palatal coverage. Dentures supported by only two implants registered higher strain than those supported by four or six implants. Implants under palateless dentures registered higher strain than those under dentures with palatal coverage. Anterior implants exhibited higher palatolabial strain than other implants regardless of palatal coverage and implant configuration; it is therefore recommended that maxillary implant overdentures should be supported by six implants with support extending to the distal end of the arch.

  11. Analysis of load reduction possibilities using a hydraulic soft yaw system for a 5-MW turbine and its sensitivity to yaw-bearing friction

    DEFF Research Database (Denmark)

    Stubkier, S.; Pedersen, H. C.; Jonkman, J. M.

    2014-01-01

    With the increasing size of wind turbines and with increasing lifetime demands, new methods for load reduction in the turbines need to be examined. One method is to make the yaw system of the turbine flexible, thereby dampening the loads to the system. This paper presents a hydraulic soft yaw...... concept and investigates the effect this has on critical loads in the turbine. To analyze the system, a novel friction model is developed and implemented for the yaw system using the NREL 5-MW turbine in the aerodynamic code FAST. Based on this model, the influence of friction is investigated...

  12. Recent advances in dental implants.

    Science.gov (United States)

    Hong, Do Gia Khang; Oh, Ji-Hyeon

    2017-12-01

    Dental implants are a common treatment for the loss of teeth. This paper summarizes current knowledge on implant surfaces, immediate loading versus conventional loading, short implants, sinus lifting, and custom implants using three-dimensional printing. Most of the implant surface modifications showed good osseointegration results. Regarding biomolecular coatings, which have been recently developed and studied, good results were observed in animal experiments. Immediate loading had similar clinical outcomes compared to conventional loading and can be used as a successful treatment because it has the advantage of reducing treatment times and providing early function and aesthetics. Short implants showed similar clinical outcomes compared to standard implants. A variety of sinus augmentation techniques, grafting materials, and alternative techniques, such as tilted implants, zygomatic implants, and short implants, can be used. With the development of new technologies in three-dimension and computer-aided design/computer-aided manufacturing (CAD/CAM) customized implants can be used as an alternative to conventional implant designs. However, there are limitations due to the lack of long-term studies or clinical studies. A long-term clinical trial and a more predictive study are needed.

  13. Osseointegration of KrF laser hydroxylapatite films on Ti6A14V alloy by mini-pigs: loaded osseointegration of dental implants

    Science.gov (United States)

    Dostalova, Tatjana; Jelinek, Miroslav; Himmlova, Lucia; Grivas, Christos

    1999-05-01

    Aim of study was to evaluate osseointegration of the KrF laser hydroxyapatite coated titanium alloy Ti6Al4V dental implants. For deposition KrF excimer laser in stainless- steel deposition chamber was used. Thickness of HA films were round 1 μm . Mini-pigs were used in this investigation. Implants were placed vertically into the lower jaw. After 14 weeks unloaded osseointegration the metal ceramic crowns were inserted. the experimental animals were sacrificed (1 year post insertion). The vertical position of implants was controlled with a radiograph. Microscopical sections were cut and ground. Sections were viewed using microscope with CCD camera. 1 year osseointegration in lower jaw confirmed by all implants presence of newly formed bone around the all implants. Laser-deposited coating the layer of fibrous connective tissue was seen only seldom. In the control group (titamium implant without cover) the fibrous connective tissue was seen between implant and newly formed bone.

  14. Magnetically leviated superconducting bearing

    Science.gov (United States)

    Weinberger, Bernard R.; Lynds, Jr., Lahmer

    1993-01-01

    A magnetically levitated superconducting bearing includes a magnet (2) mounted on a shaft (12) that is rotatable around an axis of rotation and a Type II superconductor (6) supported on a stator (14) in proximity to the magnet (2). The superconductor (6) is positioned so that when it is cooled to its superconducting state in the presence of a magnetic field, it interacts with the magnet (2) to produce an attractive force that levitates the magnet (2) and supports a load on the shaft (12). The interaction between the superconductor (6) and magnet(2) also produces surface screening currents (8) that generate a repulsive force perpendicular to the load. The bearing also has means for maintaining the superconductor at a temperature below its critical temperature (16, 18). The bearing could also be constructed so the magnet (2) is supported on the stator (14) and the superconductor (6) is mounted on the shaft (12). The bearing can be operated by cooling the superconductor (6) to its superconducting state in the presence of a magnetic field.

  15. Fiber glass-bioactive glass composite for bone replacing and bone anchoring implants.

    Science.gov (United States)

    Vallittu, Pekka K; Närhi, Timo O; Hupa, Leena

    2015-04-01

    Although metal implants have successfully been used for decades, devices made out of metals do not meet all clinical requirements, for example, metal objects may interfere with some new medical imaging systems, while their stiffness also differs from natural bone and may cause stress-shielding and over-loading of bone. Peer-review articles and other scientific literature were reviewed for providing up-dated information how fiber-reinforced composites and bioactive glass can be utilized in implantology. There has been a lot of development in the field of composite material research, which has focused to a large extent on biodegradable composites. However, it has become evident that biostable composites may also have several clinical benefits. Fiber reinforced composites containing bioactive glasses are relatively new types of biomaterials in the field of implantology. Biostable glass fibers are responsible for the load-bearing capacity of the implant, while the dissolution of the bioactive glass particles supports bone bonding and provides antimicrobial properties for the implant. These kinds of combination materials have been used clinically in cranioplasty implants and they have been investigated also as oral and orthopedic implants. The present knowledge suggests that by combining glass fiber-reinforced composite with particles of bioactive glass can be used in cranial implants and that the combination of materials may have potential use also as other types of bone replacing and repairing implants. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  16. Electromechanical impedance method to assess dental implant stability

    International Nuclear Information System (INIS)

    Tabrizi, Aydin; Rizzo, Piervincenzo; Ochs, Mark W

    2012-01-01

    The stability of a dental implant is a prerequisite for supporting a load-bearing prosthesis and establishment of a functional bone–implant system. Reliable and noninvasive methods able to assess the bone interface of dental and orthopedic implants (osseointegration) are increasingly demanded for clinical diagnosis and direct prognosis. In this paper, we propose the electromechanical impedance method as a novel approach for the assessment of dental implant stability. Nobel Biocare ® implants with a size of 4.3 mm diameter ×13 mm length were placed inside bovine bones that were then immersed in a solution of nitric acid to allow material degradation. The degradation simulated the inverse process of bone healing. The implant–bone systems were monitored by bonding a piezoceramic transducer (PZT) to the implants’ abutment and measuring the admittance of the PZT over time. It was found that the PZT’s admittance and the statistical features associated with its analysis are sensitive to the degradation of the bones and can be correlated to the loss of calcium measured by means of the atomic absorption spectroscopy method. The present study shows promising results and may pave the road towards an innovative approach for the noninvasive monitoring of dental implant stability and integrity. (paper)

  17. Radium bearing waste disposal

    International Nuclear Information System (INIS)

    Tope, W.G.; Nixon, D.A.; Smith, M.L.; Stone, T.J.; Vogel, R.A.; Schofield, W.D.

    1995-01-01

    Fernald radium bearing ore residue waste, stored within Silos 1 and 2 (K-65) and Silo 3, will be vitrified for disposal at the Nevada Test Site (NTS). A comprehensive, parametric evaluation of waste form, packaging, and transportation alternatives was completed to identify the most cost-effective approach. The impacts of waste loading, waste form, regulatory requirements, NTS waste acceptance criteria, as-low-as-reasonably-achievable principles, and material handling costs were factored into the recommended approach

  18. Superconducting composite for magnetic bearings

    International Nuclear Information System (INIS)

    Rigney, T.K. II.

    1995-01-01

    A composite includes granules of Type II superconducting material and granules of rare-earth permanent magnets that are distributed in a binder. The composite is a two-phase structure that combines the properties of the superconductor and magnets with the flexibility and toughness of a polymeric material. A bearing made from this composite has the load capacity and stiffness of a permanent magnet bearing with added stability from a Type II superconducting material. 7 figs

  19. A study of chitosan hydrogel with embedded mesoporous silica nanoparticles loaded by ibuprofen as a dual stimuli-responsive drug release system for surface coating of titanium implants.

    Science.gov (United States)

    Zhao, Pengkun; Liu, Hongyu; Deng, Hongbing; Xiao, Ling; Qin, Caiqin; Du, Yumin; Shi, Xiaowen

    2014-11-01

    In this study, the complex pH and electro responsive system made of chitosan hydrogel with embedded mesoporous silica nanoparticles (MSNs) was evaluated as a tunable drug release system. As a model drug, ibuprofen (IB) was used; its adsorption in MSNs was evidenced by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TG). In order to prepare the complex drug release system, the loaded particles IB-MSNs were dispersed in chitosan solution and then the complex IB-MSNs/chitosan film of 2mm thickness was deposited as a hydrogel on the titanium electrode. The codeposition of components was performed under a negative biasing of the titanium electrode at -0.75 mA/cm2 current density during 30 min. The IB release from the IB-MSNs/chitosan hydrogel film was studied as dependent on pH of the release media and electrical conditions applied to the titanium plate. When incubating the complex hydrogel film in buffers with different pH, the IB release followed a near zero-order profile, though its kinetics varied. Compared to the spontaneous IB release from the hydrogel in 0.9% NaCl solution (at 0 V), the application of negative biases to the coated titanium plate had profound effluences on the release behavior. The release was retarded when -1.0 V was applied, but a faster kinetics was observed at -5.0 V. These results imply that a rapid, mild and facile electrical process for covering titanium implants by complex IB-MSNs/chitosan hydrogel films can be used for controlled drug delivery applications. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Generation of an rhBMP-2-loaded beta-tricalcium phosphate/hydrogel composite and evaluation of its efficacy on peri-implant bone formation

    International Nuclear Information System (INIS)

    Lee, Jae Hyup; Baek, Hae-Ri; Lee, Ji-Ho; Ryu, Mi Young; Seo, Jun-Hyuk; Lee, Kyung-Mee

    2014-01-01

    Dental implant insertion on a site with low bone quality or bone defect should be preceded by a bone graft or artificial bone graft insertion to heal the defect. We generated a beta-tricalcium phosphate (β-TCP) and poloxamer 407-based hydrogel composite and penetration of the β-TCP/hydrogel composite into the peri-implant area of bone was evaluated by porous bone block experiments. The maximum penetration depth for porous bone blocks and dense bone blocks were 524 μm and 464 μm, respectively. We report the in-vivo performance of a composite of β-TCP/hydrogel composite as a carrier of recombinant human bone morphogenetic protein (rhBMP-2), implanted into a rabbit tibial defect model. Three holes drilled into each tibia of eight male rabbits were (1) grafted with dental implant fixtures; (2) filled with β-TCP/hydrogel composite (containing 5 μg of rhBMP-2), followed by grafting of the dental implant fixtures. Four weeks later, bone-implant contact ratio and peri-implant bone formation were analyzed by radiography, micro-CT and histology of undecalcified specimens. The micro-CT results showed a significantly higher level of trabecular thickness and new bone and peri-implant new bone formation in the experimental treatment compared to the control treatment. Histomorphometry revealed a significantly higher bone-implant contact ratio and peri-implant bone formation with the experimental treatment. The use of β-TCP/poloxamer 407 hydrogel composite as a carrier of rhBMP-2 significantly promoted new bone formation around the dental implant fixture and it also improved the quality of the new bone formed in the tibial marrow space. (paper)

  1. Assessing the Contribution of the CFRP Strip of Bearing the Applied Load Using Near-Surface Mounted Strengthening Technique with Innovative High-Strength Self-Compacting Cementitious Adhesive (IHSSC-CA

    Directory of Open Access Journals (Sweden)

    Alyaa Mohammed

    2018-01-01

    Full Text Available Efficient transfer of load between concrete substrate and fibre reinforced polymer (FRP by the bonding agent is the key factor in any FRP strengthening system. An innovative high-strength self-compacting non-polymer cementitious adhesive (IHSSC-CA was recently developed by the authors and has been used in a number of studies. Graphene oxide and cementitious materials are used to synthesise the new adhesive. The successful implementation of IHSSC-CA significantly increases carbon FRP (CFRP strip utilization and the load-bearing capacity of the near-surface mounted (NSM CFRP strengthening system. A number of tests were used to inspect the interfacial zone in the bonding area of NSM CFRP strips, including physical examination, pore structure analysis, and three-dimensional laser profilometery analysis. It was deduced from the physical inspection of NSM CFRP specimens made with IHSSC-CA that a smooth surface for load transfer was found in the CFRP strip without stress concentrations in some local regions. A smooth surface of the adhesive layer is very important for preventing localized brittle failure in the concrete. The pore structure analysis also confirmed that IHSSC-CA has better composite action between NSM CFRP strips and concrete substrate than other adhesives, resulting in the NSM CFRP specimens made with IHSSC-CA sustaining a greater load. Finally, the results of three-dimensional laser profilometery revealed a greater degree of roughness and less deformation on the surface of the CFRP strip when IHSSC-CA was used compared to other adhesives.

  2. Vibration model of rolling element bearings in a rotor-bearing system for fault diagnosis

    Science.gov (United States)

    Cong, Feiyun; Chen, Jin; Dong, Guangming; Pecht, Michael

    2013-04-01

    Rolling element bearing faults are among the main causes of breakdown in rotating machines. In this paper, a rolling bearing fault model is proposed based on the dynamic load analysis of a rotor-bearing system. The rotor impact factor is taken into consideration in the rolling bearing fault signal model. The defect load on the surface of the bearing is divided into two parts, the alternate load and the determinate load. The vibration response of the proposed fault signal model is investigated and the fault signal calculating equation is derived through dynamic and kinematic analysis. Outer race and inner race fault simulations are realized in the paper. The simulation process includes consideration of several parameters, such as the gravity of the rotor-bearing system, the imbalance of the rotor, and the location of the defect on the surface. The simulation results show that different amplitude contributions of the alternate load and determinate load will cause different envelope spectrum expressions. The rotating frequency sidebands will occur in the envelope spectrum in addition to the fault characteristic frequency. This appearance of sidebands will increase the difficulty of fault recognition in intelligent fault diagnosis. The experiments given in the paper have successfully verified the proposed signal model simulation results. The test rig design of the rotor bearing system simulated several operating conditions: (1) rotor bearing only; (2) rotor bearing with loader added; (3) rotor bearing with loader and rotor disk; and (4) bearing fault simulation without rotor influence. The results of the experiments have verified that the proposed rolling bearing signal model is important to the rolling bearing fault diagnosis of rotor-bearing systems.

  3. Hydrodynamic bearings

    CERN Document Server

    Bonneau, Dominique; Souchet, Dominique

    2014-01-01

    This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the rheological models and the equations of lubrication. It also presents the numerical approaches used to solve the above equations by finite differences, finite volumes and finite elements methods.

  4. Parametric analysis of electromechanical and fatigue performance of total knee replacement bearing with embedded piezoelectric transducers

    Science.gov (United States)

    Safaei, Mohsen; Meneghini, R. Michael; Anton, Steven R.

    2017-09-01

    Total knee arthroplasty is a common procedure in the United States; it has been estimated that about 4 million people are currently living with primary knee replacement in this country. Despite huge improvements in material properties, implant design, and surgical techniques, some implants fail a few years after surgery. A lack of information about in vivo kinetics of the knee prevents the establishment of a correlated intra- and postoperative loading pattern in knee implants. In this study, a conceptual design of an ultra high molecular weight (UHMW) knee bearing with embedded piezoelectric transducers is proposed, which is able to measure the reaction forces from knee motion as well as harvest energy to power embedded electronics. A simplified geometry consisting of a disk of UHMW with a single embedded piezoelectric ceramic is used in this work to study the general parametric trends of an instrumented knee bearing. A combined finite element and electromechanical modeling framework is employed to investigate the fatigue behavior of the instrumented bearing and the electromechanical performance of the embedded piezoelectric. The model is validated through experimental testing and utilized for further parametric studies. Parametric studies consist of the investigation of the effects of several dimensional and piezoelectric material parameters on the durability of the bearing and electrical output of the transducers. Among all the parameters, it is shown that adding large fillet radii results in noticeable improvement in the fatigue life of the bearing. Additionally, the design is highly sensitive to the depth of piezoelectric pocket. Finally, using PZT-5H piezoceramics, higher voltage and slightly enhanced fatigue life is achieved.

  5. The role of dental implant abutment design on the aesthetic outcome: preliminary 3-month post-loading results from a multicentre split-mouth randomised controlled trial comparing two different abutment designs.

    Science.gov (United States)

    Esposito, Marco; Cardaropoli, Daniele; Gobbato, Luca; Scutellà, Fabio; Fabianelli, Andrea; Mascellani, Saverio; Delli Ficorelli, Gianluca; Mazzocco, Fabio; Sbricoli, Luca; Trullenque-Eriksson, Anna

    To evaluate whether there are aesthetic and clinical benefits to using a newly designed abutment (Curvomax), over a conventional control abutment (GingiHue). A total of 49 patients, who required at least two implants, had two sites randomised according to a split-mouth design to receive one abutment of each type at seven different centres. The time of loading (immediate, early or delayed) and of prosthesis (provisional crowns of fixed prosthesis) was decided by the clinicians, but they had to restore both implants in a similar way. Provisional prostheses were replaced by definitive ones 3 months after initial loading, when the follow-up for the initial part of this study was completed. Outcome measures were: prosthesis failures, implant failures, complications, pink esthetic score (PES), peri-implant marginal bone level changes, and patient preference. In total, 49 Curvomax and 49 GingiHue abutments were delivered. Two patients dropped out. No implant failure, prosthesis failure or complication was reported. There were no differences at 3 months post-loading for PES (difference = -0.15, 95% CI -0.55 to 0.25; P (paired t test) = 0.443) and marginal bone level changes (difference = -0.02 mm, 95% CI -0.20 to 0.16; P (paired t test) = 0.817). The majority of the patients (30) had no preference regarding the two abutment designs; 11 patients preferred the Curvomax, while five patients preferred the GingiHue abutments (P (McNemar test) = 0.210). The preliminary results of the comparison between two different abutment designs did not disclose any statistically significant differences between the evaluated abutments. However the large number of missing radiographs and clinical pictures casts doubt on the reliability of the results. Longer follow-ups of wider patient populations are needed to better understand whether there is an effective advantage with one of the two abutment designs. Conflict of interest statement: This research project was originally partially funded by

  6. Bearing Capacity of Floating Ice Sheets under Short-Term Loads: Over-Sea-Ice Traverse from McMurdo Station to Marble Point

    Science.gov (United States)

    2015-01-01

    under Short-Term Loads Over-Sea-Ice Traverse from McMurdo Station to Marble Point Co ld R eg io ns R es ea rc h an d En gi ne er in g La bo ra...Traverse from McMurdo Station to Marble Point Jason C. Weale and Devinder S. Sodhi Cold Regions Research and Engineering Laboratory (CRREL) U.S...Division of Polar Programs operates an over-sea-ice traverse from McMurdo Station to rou- tinely resupply Marble Point Camp. The traverse requires that

  7. Understanding long-term silver release from surface modified porous titanium implants.

    Science.gov (United States)

    Shivaram, Anish; Bose, Susmita; Bandyopadhyay, Amit

    2017-08-01

    Prevention of orthopedic device related infection (ODRI) using antibiotics has met with limited amount of success and is still a big concern during post-surgery. As an alternative, use of silver as an antibiotic treatment to prevent surgical infections is being used due to the well-established antimicrobial properties of silver. However, in most cases silver is used in particulate form with wound dressings or with short-term devices such as catheters but not with load-bearing implants. We hypothesize that strongly adherent silver to load-bearing implants can offer longer term solution to infection in vivo. Keeping that in mind, the focus of this study was to understand the long term release study of silver ions for a period of minimum 6months from silver coated surface modified porous titanium implants. Implants were fabricated using a LENS™ system, a powder based additive manufacturing technique, with at least 25% volume porosity, with and without TiO 2 nanotubes in phosphate buffer saline (pH 7.4) to see if the total release of silver ions is within the toxic limit for human cells. Considering the fact that infection sites may reduce the local pH, silver release was also studied in acetate buffer (pH 5.0) for a period of 4weeks. Along with that, the osseointegrative properties as well as cytotoxicity of porous titanium implants were assessed in vivo for a period of 12weeks using a rat distal femur model. In vivo results indicate that porous titanium implants with silver coating show comparable, if not better, biocompatibility and bonding at the bone-implant interface negating any concerns related to toxicity related to silver to normal cells. The current research is based on our recently patented technology, however focused on understanding longer-term silver release to mitigate infection related problems in load-bearing implants that can even arise several months after the surgery. Prevention of orthopedic device related infection using antibiotics has met

  8. Short dental implants: an emerging concept in implant treatment.

    Science.gov (United States)

    Al-Hashedi, Ashwaq Ali; Taiyeb Ali, Tara Bai; Yunus, Norsiah

    2014-06-01

    Short implants have been advocated as a treatment option in many clinical situations where the use of conventional implants is limited. This review outlines the effectiveness and clinical outcomes of using short implants as a valid treatment option in the rehabilitation of edentulous atrophic alveolar ridges. Initially, an electronic search was performed on the following databases: Medline, PubMed, Embase, Cochrane Database of Systematic Reviews, and DARE using key words from January 1990 until May 2012. An additional hand search was included for the relevant articles in the following journals: International Journal of Oral and Maxillofacial Implants, Clinical Oral Implants Research, Journal of Clinical Periodontology, International Journal of Periodontics, Journal of Periodontology, and Clinical Implant Dentistry and Related Research. Any relevant papers from the journals' references were hand searched. Articles were included if they provided detailed data on implant length, reported survival rates, mentioned measures for implant failure, were in the English language, involved human subjects, and researched implants inserted in healed atrophic ridges with a follow-up period of at least 1 year after implant-prosthesis loading. Short implants demonstrated a high rate of success in the replacement of missing teeth in especially atrophic alveolar ridges. The advanced technology and improvement of the implant surfaces have encouraged the success of short implants to a comparable level to that of standard implants. However, further randomized controlled clinical trials and prospective studies with longer follow-up periods are needed.

  9. Full-mouth rehabilitation with immediate loading of implants inserted with computer-guided flap-less surgery: a 3-year multicenter clinical evaluation with oral health impact profile.

    Science.gov (United States)

    Marra, Roberto; Acocella, Alessandro; Rispoli, Alessandra; Sacco, Roberto; Ganz, Scott D; Blasi, Andrea

    2013-10-01

    The purpose of this report is to present the clinical outcomes and patients' satisfaction of full-mouth rehabilitation using computer-aided flapless implant placement and immediate loading of a prefabricated prosthesis. The study included 30 consecutive fully edentulous patients who received 312 implants. Mandible and maxilla were treated in the same surgical session with computer-guided flapless approach using the NobelGuide protocol. Prefabricated screw-retained fixed prostheses were inserted at the end of surgery. Clinical and radiographic evaluations were assessed at 6, 12, and 36 months. At baseline and 6 months after surgery, patients answered Oral Health Impact Profile in Edentulous Adults questionnaire to assess satisfaction. The implant survival rate was 97.9%, whereas the average marginal bone loss was 1.9 ± 1.3 mm after 3 years. At 6 months, patients showed significantly greater satisfaction with their fixed rehabilitation when compared with conventional dentures. The results of this study confirm that rehabilitation with a prefabricated fixed prosthesis supported by implants placed with NobelGuide protocol is a viable and predictable treatment and increases patients' satisfaction and improves oral health-related quality of life.

  10. Influence of Implant Positions and Occlusal Forces on Peri-Implant Bone Stress in Mandibular Two-Implant Overdentures: A 3-Dimensional Finite Element Analysis.

    Science.gov (United States)

    Alvarez-Arenal, Angel; Gonzalez-Gonzalez, Ignacio; deLlanos-Lanchares, Hector; Brizuela-Velasco, Aritza; Dds, Elena Martin-Fernandez; Ellacuria-Echebarria, Joseba

    2017-12-01

    The aim of this study was to evaluate and compare the bone stress around implants in mandibular 2-implant overdentures depending on the implant location and different loading conditions. Four 3-dimensional finite element models simulating a mandibular 2-implant overdenture and a Locator attachment system were designed. The implants were located at the lateral incisor, canine, second premolar, and crossed-implant levels. A 150 N unilateral and bilateral vertical load of different location was applied, as was 40 N when combined with midline load. Data for von Mises stress were produced numerically, color coded, and compared between the models for peri-implant bone and loading conditions. With unilateral loading, in all 4 models much higher peri-implant bone stress values were recorded on the load side compared with the no-load side, while with bilateral occlusal loading, the stress distribution was similar on both sides. In all models, the posterior unilateral load showed the highest stress, which decreased as the load was applied more mesially. In general, the best biomechanical environment in the peri-implant bone was found in the model with implants at premolar level. In the crossed-implant model, the load side greatly altered the biomechanical environment. Overall, the overdenture with implants at second premolar level should be the chosen design, regardless of where the load is applied. The occlusal loading application site influences the bone stress around the implant. Bilateral occlusal loading distributes the peri-implant bone stress symmetrically, while unilateral loading increases it greatly on the load side, no matter where the implants are located.

  11. Ion implantation

    International Nuclear Information System (INIS)

    Dearnaley, Geoffrey

    1975-01-01

    First, ion implantation in semiconductors is discussed: ion penetration, annealing of damage, gettering, ion implanted semiconductor devices, equipement requirements for ion implantation. The importance of channeling for ion implantation is studied. Then, some applications of ion implantation in metals are presented: study of the corrosion of metals and alloys; influence or ion implantation on the surface-friction and wear properties of metals; hyperfine interactions in implanted metals

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

    Science.gov (United States)

    Pektaş, Ömer; Tönük, Ergin

    2014-11-01

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

  13. Antitumor effect and toxicity of free rhodium (II) citrate and rhodium (II) citrate-loaded maghemite nanoparticles in mice bearing breast cancer.

    Science.gov (United States)

    Carneiro, Marcella Lemos Brettas; Peixoto, Raphael C A; Joanitti, Graziela A; Oliveira, Ricardo G S; Telles, Luis A M; Miranda-Vilela, Ana L; Bocca, Anamélia L; Vianna, Leonora M S; da Silva, Izabel C R; de Souza, Aparecido R; Lacava, Zulmira G M; Báo, Sônia N

    2013-02-16

    Magnetic fluids containing superparamagnetic iron oxide nanoparticles represent an attractive platform as nanocarriers in chemotherapy. Recently, we developed a formulation of maghemite nanoparticles coated with rhodium (II) citrate, which resulted in in vitro cytotoxicity enhanced up to 4.6 times when compared to free rhodium (II) citrate formulation on breast carcinoma cells. In this work, we evaluate the antitumor activity and toxicity induced by these formulations in Balb/c mice bearing orthotopic 4T1 breast carcinoma. Mice were evaluated with regard to the treatments' toxicity through analyses of hemogram, serum levels of alanine aminotransferase, iron, and creatinine; DNA fragmentation and cell cycle of bone marrow cells; and liver, kidney and lung histology. In addition, the antitumor activity of rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate was verified by tumor volume reduction, histology and immunohistochemistry. Regarding the treatments' toxicity, no experimental groups had alterations in levels of serum ALT or creatinine, and this suggestion was corroborated by the histopathologic examination of liver and kidney of mice. Moreover, DNA fragmentation frequency of bone marrow cells was lower than 15% in all experimental groups. On the other hand, the complexes rhodium (II) citrate-functionalized maghemite and free rhodium (II) citrate led to a marked growth inhibition of tumor and decrease in CD31 and Ki-67 staining. In summary, we demonstrated that both rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate formulations exhibited antitumor effects against 4T1 metastatic breast cancer cell line following intratumoral administration. This antitumor effect was followed by inhibition of both cell proliferation and microvascularization and by tumor tissue injury characterized as necrosis and fibrosis. Remarkably, this is the first published report demonstrating the therapeutic efficacy of maghemite

  14. Bearing structures

    International Nuclear Information System (INIS)

    Lee, A.S.; Preece, G.E.

    1988-01-01

    A hydrostatic bearing for the lower end of the vertical shaft of a sodium pump comprises a support shell encircling the shaft and a bush located between the shell and shaft. Liquid sodium is fed from the pump outlet to the bush/shaft and bush/shell interfaces to provide hydrostatic support. The bush outer surface and the shell inner surface are of complementary part-spherical shape and the bush floats relative to the shaft so that the bush can align itself with the shaft axis. Monitoring of the relative rotational speed of the bush with respect to the shaft (such rotation being induced by the viscous drag forces present) is also performed for the purposes of detecting abnormal operation of the bearing or partial seizure, at least one magnet is rotatable with the bush, and a magnetic sensor provides an output having a frequency related to the speed of the bush. (author)

  15. Journal Bearings

    Directory of Open Access Journals (Sweden)

    Renato Brancati

    1999-01-01

    determined after acquiring and analysing the orbits described by the journal axis for assigned unbalance values in different operating conditions. Analysis of the results shows some particular operating features that were not entirely predicted by the theoretical model and which may give rise to malfunctions in the rotor-tilting pad bearings system. The tests were carried out in the rotor dynamics laboratory of the Dipartimento di Ingegneria Meccanica per l'Energetica at the University of Naples.

  16. Camshaft bearing arrangement

    Energy Technology Data Exchange (ETDEWEB)

    Aoi, K.; Ozawa, T.

    1986-06-10

    A bearing arrangement is described for the camshaft of an internal combustion engine or the like which camshaft is formed along its length in axial order with a first bearing surface, a first cam lobe, a second bearing surface, a second cam lobe, a third bearing surface, a third cam lobe and a fourth bearing surface, the improvement comprising first bearing means extending around substantially the full circumference of the first bearing surface and journaling the first bearing surface, second bearing means extending around substantially less than the circumference of the second bearing surface and journaling the second bearing surface, third bearing means extending around substantially less than the circumference of the third bearing surface and journaling the third bearing surface, and fourth bearing means extending around substantially the full circumference of the fourth bearing surface and journaling the first bearing surface.

  17. Dental-Implantate und ihre Werkstoffe

    Science.gov (United States)

    Newesely, Heinrich

    1983-07-01

    Some new trends in materials for dental implants, which also effect in the operative techniques and implant design, are described. Advantages and shortcomings of the different material types are exemplified and correlated with their bioinert resp. bioactive functions. The practical interest in metallic implants focussed in titanium resp. oxide ceramics in the ceramic field, whereas the special goal of implant research follows from the improvement of the bioactive principle with loaded calcium phosphate implants.

  18. Osseointegration of loaded dental implant with KrF laser hydroxylapatite films on Ti6Al4V alloy by minipigs

    Science.gov (United States)

    Dostalova, Tatjana; Himmlova, Lucia; Jelinek, Miroslav; Grivas, Christos

    2001-04-01

    This study was performed with the objective of evaluating osseointegration of titanium alloy Ti6Al4V dental implants coated with hydroxylapatite (HA) deposited by a KrF laser. For this a KrF excimer laser and stainless-steel deposition chamber were used. The thickness of the HA films was approximately 1 micrometers . IN this investigation experimental animals minipigs were used; the implants were placed vertically into the lower jaw. After 14 weeks of unloaded osseointegration, metal-ceramic crowns were inserted and, at the same time, fluorescent solution was injected into the experimental animals. Six months after insertion of crowns the animals were sacrificed. The vertical position of the implants was checked by a radiograph. Microscopic sections were cut and ground, and the sections were examined under polarized and fluorescent light using a microscope with a charge coupled device camera. The six month long osseointegration in the lower jaw has confirmed the presence of newly formed bone around all the implants. In the experimental group, which had a laser-deposited coating, the layer of fibrous connective tissue was seen only randomly. In the control group (titanium implant without a cover) the fibrous connective tissue between the implant and the newly formed bone was observed more frequently, but this difference was not significant.

  19. Scaling laws for radial foil bearings

    Science.gov (United States)

    Honavara Prasad, Srikanth

    The effects of fluid pressurization, structural deformation of the compliant members and heat generation in foil bearings make the design and analysis of foil bearings very complicated. The complex fluid-structural-thermal interactions in foil bearings also make modeling efforts challenging because these phenomena are governed by highly non-linear partial differential equations. Consequently, comparison of various bearing designs require detailed calculation of the flow fields (velocities, pressures), bump deflections (structural compliance) and heat transfer phenomena (viscous dissipation in the fluid, frictional heating, temperature profile etc.,) resulting in extensive computational effort (time/hardware). To obviate rigorous computations and aid in feasibility assessments of foil bearings of various sizes, NASA developed the "rule of thumb" design guidelines for estimation of journal bearing load capacity. The guidelines are based on extensive experimental data. The goal of the current work is the development of scaling laws for radial foil bearings to establish an analytical "rule of thumb" for bearing clearance and bump stiffness. The use of scale invariant Reynolds equation and experimentally observed NASA "rule of thumb" yield scale factors which can be deduced from first principles. Power-law relationships between: a. Bearing clearance and bearing radius, and b. bump stiffness and bearing radius, are obtained. The clearance and bump stiffness values obtained from scaling laws are used as inputs for Orbit simulation to study various cases. As the clearance of the bearing reaches the dimensions of the material surface roughness, asperity contact breaks the fluid film which results in wear. Similarly, as the rotor diameter increases (requiring larger bearing diameters), the load capacity of the fluid film should increase to prevent dry rubbing. This imposes limits on the size of the rotor diameter and consequently bearing diameter. Therefore, this thesis aims

  20. Effect of healing time on bone-implant contact of orthodontic micro-implants: a histologic study.

    Science.gov (United States)

    Ramazanzadeh, Barat Ali; Fatemi, Kazem; Dehghani, Mahboobe; Mohtasham, Nooshin; Jahanbin, Arezoo; Sadeghian, Hamed

    2014-01-01

    Objectives. This study aimed to evaluate the effect of immediate and delayed loading of orthodontic micro-implants on bone-implant contact. Materials and Methods. Sixty four micro-implants were implanted in dog's jaw bone. The micro-implants were divided into loaded and unloaded (control) groups. The control group had two subgroups: four and eight weeks being implanted. The loaded group had two subgroups of immediate loading and delayed (after four weeks healing) loading. Loaded samples were subjected to 200g load for four weeks. After sacrificing the animals micro-implants and surrounding tissues were observed histologically. Bone-implant contact ratios (BIC) were calculated and different groups' results were compared by three-way ANOVA. Results. Mean survival rate was 96.7% in general. Survival rates were 96.7%, 94.4% and 100% for control, immediate and delayed loaded groups, respectively. BIC values were not significantly different in loaded and control groups, immediate and delayed loading groups, and pressure and tension sides. Mandibular micro-implants had significantly higher BIC than maxillary ones in immediate loading, 4-weeks control, and 8-weeks control groups (P = 0.021, P = 0.009, P = 0.003, resp.). Conclusion Immediate or delayed loading of micro-implants in dog did not cause significant difference in Bone-implant contact which could be concluded that healing time had not significant effect on micro-implant stability.

  1. Development of implants composed of bioactive materials for bone repair

    Science.gov (United States)

    Xiao, Wei

    The purpose of this Ph.D. research was to address the clinical need for synthetic bioactive materials to heal defects in non-loaded and loaded bone. Hollow hydroxyapatite (HA) microspheres created in a previous study were evaluated as a carrier for controlled release of bone morphogenetic protein-2 (BMP2) in bone regeneration. New bone formation in rat calvarial defects implanted with BMP2-loaded microspheres (43%) was significantly higher than microspheres without BMP2 (17%) at 6 weeks postimplantation. Then hollow HA microspheres with a carbonate-substituted composition were prepared to improve their resorption rate. Hollow HA microspheres with 12 wt. % of carbonate showed significantly higher new bone formation (73 +/- 8%) and lower residual HA (7 +/- 2%) than stoichiometric HA microspheres (59 +/- 2% new bone formation; 21 +/- 3% residual HA). The combination of carbonate-substituted hollow HA microspheres and clinically-safe doses of BMP2 could provide promising implants for healing non-loaded bone defects. Strong porous scaffolds of bioactive silicate (13-93) glass were designed with the aid of finite-element modeling, created by robocasting and evaluated for loaded bone repair. Scaffolds with a porosity gradient to mimic human cortical bone showed a compressive strength of 88 +/- 20 MPa, a flexural strength of 34 +/- 5 MPa and the ability to support bone infiltration in vivo. The addition of a biodegradable polylactic acid (PLA) layer to the external surface of these scaffolds increased their load-bearing capacity in four-point bending by 50% and dramatically enhanced their work of fracture, resulting in a "ductile" mechanical response. These bioactive glass-PLA composites, combining bioactivity, high strength, high work of fracture and an internal architecture conducive to bone infiltration, could provide optimal implants for structural bone repair.

  2. Big bearings. Unsung hero; Kyodaina jikuuke. Hitome ni tsukanai hatarakimono

    Energy Technology Data Exchange (ETDEWEB)

    Nanba, S. [Koyo Seiko Co. Ltd., Osaka (Japan)

    1997-03-05

    This paper introduces examples of the use of big bearings. Bearings are divided largely into those used for radial load supporting and those used for thrust load supporting, while big bearings are often used for the latter usage. Thrust bearings include a cutter heat supporting bearing for tunnel excavator working underground, in addition to those used for swing motion of parabolic antennas and tower cranes. A bearing used in an excavator has an outer diameter of about half that of the excavator. The outer diameter of a shielding machine practically used in tunnel drilling currently has an outer diameter of 14,140 mm, and the outer diameter of the bearing is 7200 mm (bearing weighing 45 tons). Other big thrust bearings may include a swing tower swinging thrust bearing used in a continuous casting facility. Big radial bearings are used in iron and steel making facilities. This paper describes two examples of bearings used in this application. A spherical roller bearing to support converter trunion should be of an ultra big size to withstand total weight of about 1400 tons composed of a converter weight and weight of steel to be processed. A four-row cylindrical roller bearing to support the backup roll of a thick plate rolling mill is a bearing with durability against large loads to support reduction rolls whose size have become increasingly large. 2 refs., 5 figs.

  3. Microstructure and properties of nitrogen ion implantation/AlN/CrAlN/MoS{sub 2}-phenolic resin duplex coatings on magnesium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Zhiwen [University of Science and Technology Liaoning, Anshan 114051 (China); Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714 (China); Chen, Qiang, E-mail: 2009chenqiang@163.com [Southwest Technique and Engineering Research Institute, Chongqing 400039 (China); Chen, Tian [Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714 (China); Gao, Xu; Yu, Xiaoguang; Song, Hua; Feng, Yongjun [University of Science and Technology Liaoning, Anshan 114051 (China)

    2015-06-15

    The novel nitrogen ion implantation/AlN/CrAlN/MoS{sub 2}-phenolic resin duplex coatings are fabricated on the AM60 magnesium alloys. The microstructure, tribological and electrochemical properties of the duplex coatings are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, nano-indenter, electrochemical corrosion and wear tester. These studies reveal that the MoS{sub 2}-phenolic resin coating has a two-phase microstructure crystalline MoS{sub 2} particles embedded in the amorphous phenolic resin matrix. The single-layer MoS{sub 2}-phenolic resin enhances the corrosion resistance of magnesium alloys, but shows poor wear resistance due to the low substrate's load bearing capacity. The addition of nitrogen ion implantation/AlN/CrAlN interlayer in the MoS{sub 2}-phenolic resin/substrate system greatly enhances the substrate's load bearing capacity. The AlN/CrAlN/MoS{sub 2}-phenolic resin duplex coating with a high load bearing capacity demonstrates super wear resistance (i.e., long wear life and low friction coefficient). In addition, the nitrogen ion implantation/AlN interlayer greatly depresses the effect of galvanic corrosion because its potential is close to that of the magnesium alloys, but the nitrogen ion implantation/AlN/CrAlN interlayer is inefficient in reducing the galvanic corrosion due to the large potential difference between the CrN phase and the substrate. As a result, the nitrogen ion implantation/AlN/MoS{sub 2}-phenolic resin duplex coating shows a better corrosion resistance compared to the nitrogen ion implantation/AlN/CrAlN/MoS{sub 2}-phenolic resin. - Highlights: • Ion implantation/AlN/CrAlN/MoS{sub 2}-phenolic resin duplex coatings were presented. • Ion implantation/AlN/CrAlN interlayer greatly enhanced the load bearing capacity. • Ion implantation/AlN interlayer greatly depressed the effect of galvanic corrosion. • The

  4. Stabilizing gas bearing in free piston machines

    Science.gov (United States)

    Dhar, Manmohan (Inventor)

    1992-01-01

    In a free piston engine, to reduce dynamic loads on the reciprocating elements caused by a time varying pressure gradient across the gas bearing and close clearance seals provided therein, drain galleries are incorporated at the ends of the gas bearings to isolate the same, and circumferentially spaced grooves are incorporated in the close clearance seal region.

  5. Oral health-related quality of life changes after placement of immediately loaded single implants in healed alveolar ridges or extraction sockets: a 5-year prospective follow-up study.

    Science.gov (United States)

    Raes, Stefanie; Raes, Filiep; Cooper, Lyndon; Giner Tarrida, Luis; Vervaeke, Stijn; Cosyn, Jan; De Bruyn, Hugo

    2017-06-01

    The impact of single implants on oral health-related quality of life (OHRQoL) is scarcely investigated, especially when combined with immediate placement and loading in extraction sockets. The aim was to describe prospectively the changes of OHRQoL with single implants placed in the esthetic zone in healed ridges or in extraction sockets after 5 years. Ninety-six patients, enrolled at three clinical centers, received 102 single implants placed in a healed ridge (n = 54 implants/50 patients) or in extraction sockets (n = 48 implants/46 patients). Implants were immediately provisionalized, and permanent crowns were cemented after 12 weeks. Oral health impact profile questionnaires (OHIP-14) were completed before surgery, after 1 (provisional crown), 6 (permanent crown), 12 and 60 months, respectively. The overall OHIP-14 score pertains to seven domains with two items each and was assessed on a Likert scale of 0-4 (0 = never and 4 = very often). The evolution of the total OHIP-14 score and changes within all OHIP domains over time and between groups were assessed with a linear mixed-effect model analysis. After 5 years, overall implant survival was 98%. The total OHIP-14 score for both groups combined decreased from 0.50 at baseline to 0.17 at 6 months (P < 0.001), indicative of improvement. For both groups, this remained stable up to 5 years (P = 0.41). However, after 5 years, the total OHIP-14 score revealed a statistically significantly higher improvement in the healed group compared with the extraction group (P = 0.027). Missing a single tooth in the maxillary esthetic zone leads to limited OHRQoL problems as reflected by a low overall OHIP score. However, OHRQoL improves less in the extraction group, reflecting that replacing a missing tooth is perceived as more beneficial than replacing a present tooth. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  6. Management of peri-implantitis

    Directory of Open Access Journals (Sweden)

    Jayachandran Prathapachandran

    2012-01-01

    Full Text Available Peri-implantitis is a site-specific infectious disease that causes an inflammatory process in soft tissues, and bone loss around an osseointegrated implant in function. The etiology of the implant infection is conditioned by the status of the tissue surrounding the implant, implant design, degree of roughness, external morphology, and excessive mechanical load. The microorganisms most commonly associated with implant failure are spirochetes and mobile forms of Gram-negative anaerobes, unless the origin is the result of simple mechanical overload. Diagnosis is based on changes of color in the gingiva, bleeding and probing depth of peri-implant pockets, suppuration, X-ray, and gradual loss of bone height around the tooth. Treatment will differ depending upon whether it is a case of peri-implant mucositis or peri-implantitis. The management of implant infection should be focused on the control of infection, the detoxification of the implant surface, and regeneration of the alveolar bone. This review article deals with the various treatment options in the management of peri-implantitis. The article also gives a brief description of the etiopathogenesis, clinical features, and diagnosis of peri-implantitis.

  7. Experimental Study and Dynamic Modeling of Metal Rubber Isolating Bearing

    International Nuclear Information System (INIS)

    Zhang, Ke; Zhou, Yanguo; Jiang, Jian

    2015-01-01

    In this paper, dynamic shear mechanical properties of a new metal rubber isolating bearing is tested and studied. The mixed damping model is provided for theoretical modeling of MR isolating bearing, the shear stiffness and damping characteristics of the MR bearing can be analyzed separately and easily discussed, and the mixed damping model is proved to be an rather effective approach. The test results indicate that loading frequency bears little impact over shear property of metal rubber isolating bearing, the total energy consumption of metal rubber isolating bearing increases with the increase in loading amplitude. With the increase in loading amplitude, the stiffness of the isolating bearing will reduce showing its “soft property”; and the type of damping force gradually changes to be close to dry friction. The features of “soft property” and dry friction energy consumption of metal rubber isolating bearing are very useful in practical engineering application. (paper)

  8. Corrosion resistance of titanium ion implanted AZ91 magnesium alloy

    International Nuclear Information System (INIS)

    Liu Chenglong; Xin Yunchang; Tian Xiubo; Zhao, J.; Chu, Paul K.

    2007-01-01

    Degradable metal alloys constitute a new class of materials for load-bearing biomedical implants. Owing to their good mechanical properties and biocompatibility, magnesium alloys are promising in degradable prosthetic implants. The objective of this study is to improve the corrosion behavior of surgical AZ91 magnesium alloy by titanium ion implantation. The surface characteristics of the ion implanted layer in the magnesium alloys are examined. The authors' results disclose that an intermixed layer is produced and the surface oxidized films are mainly composed of titanium oxide with a lesser amount of magnesium oxide. X-ray photoelectron spectroscopy reveals that the oxide has three layers. The outer layer which is 10 nm thick is mainly composed of MgO and TiO 2 with some Mg(OH) 2 . The middle layer that is 50 nm thick comprises predominantly TiO 2 and MgO with minor contributions from MgAl 2 O 4 and TiO. The third layer from the surface is rich in metallic Mg, Ti, Al, and Ti 3 Al. The effects of Ti ion implantation on the corrosion resistance and electrochemical behavior of the magnesium alloys are investigated in simulated body fluids at 37±1 deg. C using electrochemical impedance spectroscopy and open circuit potential techniques. Compared to the unimplanted AZ91 alloy, titanium ion implantation significantly shifts the open circuit potential (OCP) to a more positive potential and improves the corrosion resistance at OCP. This phenomenon can be ascribed to the more compact surface oxide film, enhanced reoxidation on the implanted surface, as well as the increased β-Mg 12 Al 17 phase

  9. CLINICAL CASE WITH IMMEDIATE PLACEMENT OF IMPLANTS AND EARLY LOADING WITH MOVABLE PROSTHETIC STRUCTURE OF A PATIENT WITH GENERALIZED PERIODONTITIS AND II - III DEGREE MOBILITY OF THE TEETH

    Directory of Open Access Journals (Sweden)

    Tihomir Georgiev

    2010-12-01

    Full Text Available One of the most common inflammation disease in the oral cavity for the past few years is the chronic form of parodontitis. Every 2nd or 3rd patient who has been to the dentist has the illness. If a person has this illness he cannot have an implant treatment done, because it is temporarily contraindicated until the oral hygiene and status is restored. Patients with reoccurring chronic periodontitis, who need an implant treatment are a real challenge for the dental surgeon and the prosthetis.

  10. Nonlinear Dynamic Response of Compliant Journal Bearings

    Directory of Open Access Journals (Sweden)

    Glavatskih S.

    2012-07-01

    Full Text Available This paper investigates the dynamic response of the compliant tilting pad journal bearings subjected to synchronous excitation. Bearing compliance is affected by the properties of pad liner and pad support geometry. Different unbalance eccentricities are considered. It is shown that bearing dynamic response is non-linear. Journal orbit complexity increases with pad compliance though the orbit amplitudes are marginally affected at low loads. At high loads, the journal is forced to operate outside the bearing clearance. The polymer liner reduces the maximum oil film pressure by a factor of 2 when compared to the white metal liner. The nonlinear dynamic response of compliant tilting pad journal bearings is thoroughly discussed.

  11. The effects of simulated bone loss on the implant-abutment assembly and likelihood of fracture: an in vitro study.

    Science.gov (United States)

    Manzoor, Behzad; Suleiman, Mahmood; Palmer, Richard M

    2013-01-01

    The crestal bone level around a dental implant may influence its strength characteristics by offering protection against mechanical failures. Therefore, the present study investigated the effect of simulated bone loss on modes, loads, and cycles to failure in an in vitro model. Different amounts of bone loss were simulated: 0, 1.5, 3.0, and 4.5 mm from the implant head. Forty narrow-diameter (3.0-mm) implant-abutment assemblies were tested using compressive bending and cyclic fatigue testing. Weibull and accelerated life testing analysis were used to assess reliability and functional life. Statistical analyses were performed using the Fisher-Exact test and the Spearman ranked correlation. Compressive bending tests showed that the level of bone loss influenced the load-bearing capacity of implant-abutment assemblies. Fatigue testing showed that the modes, loads, and cycles to failure had a statistically significant relationship with the level of bone loss. All 16 samples with bone loss of 3.0 mm or more experienced horizontal implant body fractures. In contrast, 14 of 16 samples with 0 and 1.5 mm of bone loss showed abutment and screw fractures. Weibull and accelerated life testing analysis indicated a two-group distribution: the 0- and 1.5-mm bone loss samples had better functional life and reliability than the 3.0- and 4.5-mm samples. Progressive bone loss had a significant effect on modes, loads, and cycles to failure. In addition, bone loss influenced the functional life and reliability of the implant-abutment assemblies. Maintaining crestal bone levels is important in ensuring biomechanical sustainability and predictable long-term function of dental implant assemblies.

  12. Failure location prediction by finite element analysis for an additive manufactured mandible implant.

    Science.gov (United States)

    Huo, Jinxing; Dérand, Per; Rännar, Lars-Erik; Hirsch, Jan-Michaél; Gamstedt, E Kristofer

    2015-09-01

    In order to reconstruct a patient with a bone defect in the mandible, a porous scaffold attached to a plate, both in a titanium alloy, was designed and manufactured using additive manufacturing. Regrettably, the implant fractured in vivo several months after surgery. The aim of this study was to investigate the failure of the implant and show a way of predicting the mechanical properties of the implant before surgery. All computed tomography data of the patient were preprocessed to remove metallic artefacts with metal deletion technique before mandible geometry reconstruction. The three-dimensional geometry of the patient's mandible was also reconstructed, and the implant was fixed to the bone model with screws in Mimics medical imaging software. A finite element model was established from the assembly of the mandible and the implant to study stresses developed during mastication. The stress distribution in the load-bearing plate was computed, and the location of main stress concentration in the plate was determined. Comparison between the fracture region and the location of the stress concentration shows that finite element analysis could serve as a tool for optimizing the design of mandible implants. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

  13. Maintenance in dental implants

    Directory of Open Access Journals (Sweden)

    Giselle Póvoa Gomes

    2008-01-01

    Full Text Available In implants, maintenance is a decisive factor for obtaining success when implant supported overdentures and dentures are used. The present stud presents, a clinical case of a patient, a 70 year-old white man, with a completely edentulous mandibular alveolar ridge, severe bone resorption with presence of basal bone only, and absence of vestibule. Initially, treatment consisted of the placement of a mandibular overdenture, supported on three implants in the anterior inter-foramen region, as the left implant was transfixed in the basal bone of 2 to 3 millimeters. Eleven years later, another two implants were placed in the anterior area and an immediate load was performed up to the first molars, for the placement of an implant supported fixed. Throughout the entire treatment, meticulous maintenance was carried out, with follow-up for fourteen years, interrupted by the patient’s death. From the third month after the opening the three implants initially placed, the presence of keratinized mucosa, definition of the vestibule, maturation of the alveolar ridge and bone formation in the mento region were observed. It was concluded that good planning, allied to mastery of the technique and adequate maintenance were the prerequisites necessary for obtaining favorable results, success of the present case, and for the patient to have a better quality of life.

  14. On the computation of electrical resistance of hydrodynamic journal bearing

    Directory of Open Access Journals (Sweden)

    Eleonora Pop

    2014-12-01

    Full Text Available The paper approaches the mathematical model of electrical resistance of hydrodynamic journal bearing under different parameters of operation so as to predict bearing performance and safe load carrying capacity. The currents circulating in the journal bearing of electrical machine causes reducing of lifespan by appearance of pitting on their surface and the degradation of the lubricant. In a hydrodynamic journal bearing, the zone of minimum film thickness, load-carrying oil film varies along the circumference of a bearing through its length. This has been found to form a capacitor of varying capacitance between the journal and the bearings dependent on permittivity of the lubricant used, the bearing length, the eccentricity ratio and the clearance ratio. Besides this, load-carrying on oil film offers resistance that depends on operating parameters and resistivity of the lubricant.

  15. Gearbox Reliability Collaborative Gearbox 3 Planet Bearing Calibration

    Energy Technology Data Exchange (ETDEWEB)

    Keller, Jonathan [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2017-03-24

    The Gearbox Reliability Collaborative gearbox was redesigned to improve its load-sharing characteristics and predicted fatigue life. The most important aspect of the redesign was to replace the cylindrical roller bearings with preloaded tapered roller bearings in the planetary section. Similar to previous work, the strain gages installed on the planet tapered roller bearings were calibrated in a load frame. This report describes the calibration tests and provides the factors necessary to convert the measured units from dynamometer testing to bearing loads, suitable for comparison to engineering models.

  16. Effects of different numbers of mini-dental implants on alveolar ridge strain distribution under mandibular implant-retained overdentures.

    Science.gov (United States)

    Warin, Pongsakorn; Rungsiyakull, Pimduen; Rungsiyakull, Chaiy; Khongkhunthian, Pathawee

    2018-01-01

    To investigate the strains around mini-dental implants (MDIs) and retromolar edentulous areas when using different numbers of MDIs in order to retain mandibular overdentures. Four different prosthetic situations were fabricated on an edentulous mandibular model including a complete denture (CD), and three overdentures, retained by four, three or two MDIs in the interforaminal region with retentive attachments. A static load of 200N was applied on the posterior teeth of the dentures under bilateral or unilateral loading conditions. The strains at the mesial and distal of the MDIs and the retromolar edentulous ridges were measured using twelve strain gauges. Comparisons of the mean microstrains among all strain gauges in all situations were analyzed. The strain distribution determined during bilateral loading experienced a symmetrical distribution; while during unilateral loading, the recorded strains tended to change from compressive strains on the loaded side to tensile strains. Overall, the number of MDIs was found to be passively correlated to the generated compressive strain. The highest strains were recorded in the four MDIs followed by three, two MDIs retained overdenture and CD situations, respectively. The highest strain was found around the terminal MDI. The use of a low number of MDIs tends to produce low strain values in the retromolar denture-bearing area and around the terminal MDIs during posterior loadings. However, when using a high number of MDIs, the overdenture tends to have more stability during function. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  17. Development and Evaluation of Titanium Spacesuit Bearings

    Science.gov (United States)

    Rhodes, Richard; Battisti, Brian; Ytuarte, Raymond, Jr.; Schultz, Bradley

    2016-01-01

    The Z-2 Prototype Planetary Extravehicular Space Suit Assembly is a continuation of NASA's Z-series of spacesuits, designed with the intent of meeting a wide variety of exploration mission objectives, including human exploration of the Martian surface. Incorporating titanium bearings into the Z-series space suit architecture allows us to reduce mass by an estimated 23 lbs per suit system compared to the previously used stainless steel bearing race designs, without compromising suit functionality. There are two obstacles to overcome when using titanium for a bearing race- 1) titanium is flammable when exposed to the oxygen wetted environment inside the space suit and 2) titanium's poor wear properties are often challenging to overcome in tribology applications. In order to evaluate the ignitability of a titanium space suit bearing, a series of tests were conducted at White Sands Test Facility (WSTF) that introduced the bearings to an extreme test profile, with multiple failures imbedded into the test bearings. The testing showed no signs of ignition in the most extreme test cases; however, substantial wear of the bearing races was observed. In order to design a bearing that can last an entire exploration mission (approx. 3 years), design parameters for maximum contact stress need to be identified. To identify these design parameters, bearing test rigs were developed that allow for the quick evaluation of various bearing ball loads, ball diameters, lubricants, and surface treatments. This test data will allow designers to minimize the titanium bearing mass for a specific material and lubricant combination and design around a cycle life requirement for an exploration mission. This paper reviews the current research and testing that has been performed on titanium bearing races to evaluate the use of such materials in an enriched oxygen environment and to optimize the bearing assembly mass and tribological properties to accommodate for the high bearing cycle life for an

  18. Fault tolerant homopolar magnetic bearings with flux invariant control

    International Nuclear Information System (INIS)

    Na, Uhn Joo

    2006-01-01

    The theory for a novel fault-tolerant 4-active-pole homopolar magnetic bearing is developed. If any one coil of the four coils in the bearing actuator fail, the remaining three coil currents change via an optimal distribution matrix such that the same opposing pole, C-core type, control fluxes as those of the un-failed bearing are produced. The homopolar magnetic bearing thus provides unaltered magnetic forces without any loss of the bearing load capacity even if any one coil suddenly fails. Numerical examples are provided to illustrate the novel fault-tolerant, 4-active pole homopolar magnetic bearings

  19. Two-stage implant systems.

    Science.gov (United States)

    Fritz, M E

    1999-06-01

    Since the advent of osseointegration approximately 20 years ago, there has been a great deal of scientific data developed on two-stage integrated implant systems. Although these implants were originally designed primarily for fixed prostheses in the mandibular arch, they have been used in partially dentate patients, in patients needing overdentures, and in single-tooth restorations. In addition, this implant system has been placed in extraction sites, in bone-grafted areas, and in maxillary sinus elevations. Often, the documentation of these procedures has lagged. In addition, most of the reports use survival criteria to describe results, often providing overly optimistic data. It can be said that the literature describes a true adhesion of the epithelium to the implant similar to adhesion to teeth, that two-stage implants appear to have direct contact somewhere between 50% and 70% of the implant surface, that the microbial flora of the two-stage implant system closely resembles that of the natural tooth, and that the microbiology of periodontitis appears to be closely related to peri-implantitis. In evaluations of the data from implant placement in all of the above-noted situations by means of meta-analysis, it appears that there is a strong case that two-stage dental implants are successful, usually showing a confidence interval of over 90%. It also appears that the mandibular implants are more successful than maxillary implants. Studies also show that overdenture therapy is valid, and that single-tooth implants and implants placed in partially dentate mouths have a success rate that is quite good, although not quite as high as in the fully edentulous dentition. It would also appear that the potential causes of failure in the two-stage dental implant systems are peri-implantitis, placement of implants in poor-quality bone, and improper loading of implants. There are now data addressing modifications of the implant surface to alter the percentage of

  20. Osteoporotic rat models for evaluation of osseointegration of bone implants

    NARCIS (Netherlands)

    Alghamdi, H.S.A.; Beucken, J.J.J.P van den; Jansen, J.A.

    2014-01-01

    Osseointegration of dental and orthopedic bone implants is the important process that leads to mechanical fixation of implants and warrants implant functionality. In view of increasing numbers of osteoporotic patients, bone implant surface optimization strategies with instructive and drug-loading

  1. Research on the Mechanical Properties of "Z" Type Double-Decker Ball Bearings.

    Science.gov (United States)

    Yu, Chengtao; Xu, Longxiang; Yu, Xudong

    2014-01-01

    The mechanical model of a "Z" type double-decker ball bearing under the action of radial load is established in this paper on the basis of the Hertz contact theory. According to the security contact angle theory, the influences of inner and outer bearings' internal clearances on the bearing's static load carrying capacity, radial deformation, radial stiffness, and load distribution of balls are analyzed. This model is verified in both stationary and rotational loading experiments. Moreover, the simulation results show that the static load carrying capacity of Z type bearing is smaller than that of either inner bearing or outer bearing that is contributed to compose the Z type bearing. The static load carrying capacity of a Z type bearing reduces with the increase of the inner and outer bearings' internal clearance. These simulation results also indicate that the contact angle of the maximum loaded ball in the outer bearing easily exceeds its security contact angle compared with the inner bearing, which, as the main factor, may cause the Z type bearing to overload and to fail. In this sense, the investigated Z type bearings are unfit to apply to situations with heavy load, high speed, or high precision.

  2. Improving osseointegration of dental implants.

    Science.gov (United States)

    Elias, Carlos Nelson; Meirelles, Luiz

    2010-03-01

    In the beginning of implantology, the procedures adopted for treating patients were performed in two surgical phases with an interval of 3-6 months. Nowadays, it is possible to insert and load a dental implant in the same surgical procedure. This change is due to several factors, such as improvement of surgical technique, modifications of the implant design, increased quality of implant manufacturing, development of the surgical instruments' quality, careful patient screening and adequate treatment of the implant surface. The clinical results show that adequate treatment of surfaces is crucial for reducing healing time and treating at-risk patients. The surface properties of dental implants can be significantly improved at the manufacturing stage, affecting cells' activity during the healing phase that will ultimately determine the host tissue response, a fundamental requirement for clinical success. This review focuses on different types of dental implant surfaces and the influence of surface characteristics on osseointegration.

  3. [Ceramic-on-ceramic bearings in total hip arthroplasty (THA)].

    Science.gov (United States)

    Sentürk, U; Perka, C

    2015-04-01

    The main reason for total hip arthroplasty (THA) revision is the wear-related aseptic loosening. Younger and active patients after total joint replacement create high demands, in particular, on the bearings. The progress, especially for alumina ceramic-on-ceramic bearings and mixed ceramics have solved many problems of the past and lead to good in vitro results. Modern ceramics (alumina or mixed ceramics containing alumina) are extremely hard, scratch-resistant, biocompatible, offer a low coefficient of friction, superior lubrication and have the lowest wear rates in comparison to all other bearings in THA. The disadvantage of ceramic is the risk of material failure, i.e., of ceramic fracture. The new generation of mixed ceramics (delta ceramic), has reduced the risk of head fractures to 0.03-0.05 %, but the risk for liner fractures remains unchanged at about 0.02 %. Assuming a non-impinging component implantation, ceramic-on-ceramic bearings have substantial advantages over all other bearings in THA. Due to the superior hardness, ceramic bearings produce less third body wear and are virtually impervious to damage from instruments during the implantation process. A specific complication for ceramic-on-ceramic bearings is "squeaking". The high rate of reported squeaking (0.45 to 10.7 %) highlights the importance of precise implant positioning and the stem and patient selection. With precise implant positioning this problem is rare with many implant designs and without clinical relevance. The improved tribology and the presumable resulting implant longevity make ceramic-on-ceramic the bearing of choice for young and active patients. Georg Thieme Verlag KG Stuttgart · New York.

  4. Bioelectric analyses of an osseointegrated intelligent implant design system for amputees.

    Science.gov (United States)

    Isaacson, Brad M; Stinstra, Jeroen G; MacLeod, Rob S; Webster, Joseph B; Beck, James P; Bloebaum, Roy D

    2009-07-15

    The projected number of American amputees is expected to rise to 3.6 million by 2050. Many of these individuals depend on artificial limbs to perform routine activities, but prosthetic suspensions using traditional socket technology can prove to be cumbersome and uncomfortable for a person with limb loss. Moreover, for those with high proximal amputations, limited residual limb length may prevent exoprosthesis attachment all together. Osseointegrated implant technology is a novel operative procedure which allows firm skeletal attachment between the host bone and an implant. Preliminary results in European amputees with osseointegrated implants have shown improved clinical outcomes by allowing direct transfer of loads to the bone-implant interface. Despite the apparent advantages of osseointegration over socket technology, the current rehabilitation procedures require long periods of restrictive load bearing prior which may be reduced with expedited skeletal attachment via electrical stimulation. The goal of the osseointegrated intelligent implant design (OIID) system is to make the implant part of an electrical system to accelerate skeletal attachment and help prevent periprosthetic infection. To determine optimal electrode size and placement, we initiated proof of concept with computational modeling of the electric fields and current densities that arise during electrical stimulation of amputee residual limbs. In order to provide insure patient safety, subjects with retrospective computed tomography scans were selected and three dimensional reconstructions were created using customized software programs to ensure anatomical accuracy (Seg3D and SCIRun) in an IRB and HIPAA approved study. These software packages supported the development of patient specific models and allowed for interactive manipulation of electrode position and size. Preliminary results indicate that electric fields and current densities can be generated at the implant interface to achieve the

  5. Cochlear Implants

    Science.gov (United States)

    ... implant, including: • How long a person has been deaf, •The number of surviving auditory nerve fibers, and • ... Implant, Severe Sensoryneurial Hearing Loss Get Involved Professional Development Practice Management ENT Careers Marketplace Privacy Policy Terms ...

  6. Rolling Bearing Life Prediction, Theory, and Application

    Science.gov (United States)

    Zaretsky, Erwin V.

    2016-01-01

    A tutorial is presented outlining the evolution, theory, and application of rolling-element bearing life prediction from that of A. Palmgren, 1924; W. Weibull, 1939; G. Lundberg and A. Palmgren, 1947 and 1952; E. Ioannides and T. Harris, 1985; and E. Zaretsky, 1987. Comparisons are made between these life models. The Ioannides-Harris model without a fatigue limit is identical to the Lundberg-Palmgren model. The Weibull model is similar to that of Zaretsky if the exponents are chosen to be identical. Both the load-life and Hertz stress-life relations of Weibull, Lundberg and Palmgren, and Ioannides and Harris reflect a strong dependence on the Weibull slope. The Zaretsky model decouples the dependence of the critical shear stress-life relation from the Weibull slope. This results in a nominal variation of the Hertz stress-life exponent. For 9th- and 8th-power Hertz stress-life exponents for ball and roller bearings, respectively, the Lundberg-Palmgren model best predicts life. However, for 12th- and 10th-power relations reflected by modern bearing steels, the Zaretsky model based on the Weibull equation is superior. Under the range of stresses examined, the use of a fatigue limit would suggest that (for most operating conditions under which a rolling-element bearing will operate) the bearing will not fail from classical rolling-element fatigue. Realistically, this is not the case. The use of a fatigue limit will significantly overpredict life over a range of normal operating Hertz stresses. (The use of ISO 281:2007 with a fatigue limit in these calculations would result in a bearing life approaching infinity.) Since the predicted lives of rolling-element bearings are high, the problem can become one of undersizing a bearing for a particular application. Rules had been developed to distinguish and compare predicted lives with those actually obtained. Based upon field and test