Stress analysis of implant-supported partial prostheses in anisotropic mandibular bone: in-line versus offset...

Three-dimensional, anisotropic finite element models were executed to investigate the biomechanical effects of in-line and offset placements of implants on implant-supported partial prostheses. Three implant placements of finite element models were created: in-line, buccal offset and lingual offset placements. The mesh models of a cadaver mandibular segment and a three-united crown containing the 2nd premolar, the 1st molar and the 2nd molar were constructed by computer tomography images. The material properties of mandible were applied as transversely isotropic and linearly elastic. Two loading modes (100N), vertical and oblique, were evaluated in all models. Insignificant difference was observed in implant stresses between the in-line and offset placements under the vertical loading mode. Under the oblique loading, however, the offset placement decreased the implant stress by a maximum of 17%. The maximum stress at cortical bone and trabecular bone around each implant did not show conspicuous difference between the in-line and offset placements. This study demonstrated the mechanisms of how stresses were distributed between the in-line and offset placements. Even though the offset placements showed the benefit of decreasing implant stresses, justified from the bone stress the offset placements provided no advantage for the stress decreasing over the in-line placement.