Objectives: The purpose of this study was to investigate the effects of (1) the bite forces for both force direction and location, and (2) the implant designs of alignment (in-line and off-line) and size of the implants on stress distribution of the implant-supported partial prostheses. Methods: Three dimensional finite element models were constructed by the combination of the computed tomographic (CT) images of a human mandible and the solid models of cylindrical dental implants. All models were meshed with quadrics tetrahedral elements and the nodes at the bottom surfaces of the mandibular bone were constrained in x, y, and z directions. Results: The results showed that high stress regions were located at the neck of and the alveolar crest around the implants. The stress concentration patterns appeared to concur with the clinical observations for the implant fracture sites and the initial location of alveolar bone loss. The wider implant diameter reduced stress magnitudes in both the implant neck and the alveolar crest. This was partially due to the increased implant-bone contact area and the large moment inertia of wide implant. The oblique force yielded much higher (five times) stresses in cortical bone than the vertical force. However, the off-line implant alignment alone did not always decrease stress the values. Conclusion: There exists a complicated interaction between implant alignment, loading direction and the shape of mandible block simulated. (Whitaker Foundation RG97-455)

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