3-D Finite element stress analysis in screw-type, cement-type, and combined-type implant fixed partial denture designs / 대한치과보철학회지

STATEMENT OF PROBLEMS: Stress analysis on implant components of the combined screw- and cement-retained implant prosthesis has not investigated yet. PURPOSE: The purpose of this study was to assess the load distribution characteristics of implant prostheses with the different prosthodontic retention types, such as cement-type, screw-type and combined type by using 3-dimensional finite element analysis. MATERIAL AND METHODS: A 3-dimensional finite element model was created in which two SS II implants (Osstem Co. Ltd.) were placed in the areas of the first premolar and the first molar in the mandible , and three-unit fixed partial dentures with four different retention types were fabricated on the two SS II implants. Model 1 was a cement-retained implant restoration made on two cement-retained type abutments (Comocta abutment; Osstem Co. Ltd.), and Model 2 was a screw-retained implant restoration made on the screw-retained type abutments (Octa abutment; Osstem Co. Ltd.). Model 3 was a combined type implant restoration made on the cement-retained type abutment (Comocta abutment) for the first molar and the screw-retained type abutment (Octa abutment) for the first premolar. Lastly, Model 4 was a combined type implant restoration made on the screw-retained type abutment (Octa abutment) for the first molar and the cement-retained type abutment (Comocta abutment) for the first premolar. Average masticatory force was applied on the central fossa in a vertical direction, and on the buccal cusp in a vertical and oblique direction for each model. Von-Mises stress patterns on alveolar bone, implant body, abutment, abutment screw, and prosthetic screw around implant prostheses were evaluated through 3-dimensional finite element analysis. RESULTS: Model 2 showed the lowest von Mises stress. In all models, the von Mises stress distribution of cortical bone, cancellous bone and implant body showed the similar pattern. Regardless of loading conditions and type of abutment system, the stress of bone was concentrated on the cortical bone. The von-Mises stress on abutment, abutment screw, and prosthetic screw showed the lower values for the screw-retained type abutment than for the cement-retained type abutment regardless of the model type. There was little reciprocal effect of the abutment system between the molar and the premolar position. For all models, buccal cusp oblique loading caused the largest stress, followed by buccal cusp vertical loading and center vertical loading. CONCLUSION: Within the limitation of the FEA study, the combined type implant prosthesis did not demonstrate more stress around implant components than the cement type implant prosthesis. Under the assumption of ideal passive fit, the screw-type implant prosthesis showed the least stress around implant components.

Certificate Education for Geriatric Physician: Satisfaction and Feasibility / 예방의학회지

OBJECTIVES: Korea faces a number of challenges to meet demands in the area of geriatric professional medicine in a country with a rapidly ageing population. We evaluated the satisfaction and feasibility of the current education certification for geriatric physicians. METHODS: Geriatric physicians who were deemed qualified by the Korean Geriatrics Society during the period of 2001 to 2005 (n=2,200) were asked to complete structured questionnaires sent to them by mail about their satisfaction of and need for certificates of education, as well as their opinions on their geriatric specialty training. A total of 419 physicians responded. Descriptive analysis and hierarchical regression were performed to rate the respondents.satisfaction, the characteristics of the need for clarity and utility in education certification, and the characteristics of their patients. RESULTS: Although most respondents were satisfied with their education certification, those who had more elderly patients, aged 65 or older, and those who had more cognitively impaired patients, rated their education as significantly lower than did other physicians. Both groups expressed the need for more the comprehensive care and assessment concerning of their education. Multiple regression analysis indicated that satisfaction with geriatric physician qualification was associated with a physician's age, specialty, and percentage of elderly patients. CONCLSIONS: This study suggests that the current system of education certification is limited in terms of feasibility and physician satisfaction.