Biomechanical effects of different fixed partial denture designs planned on bicortically anchored short, graft-supported long, or 45-degree-inclined long implants in the posterior maxilla: a three-dimensional finite element analysis.

Purpose: The purpose of this study was to analyze the functional stresses around implants and supporting tissues placed in different combinations in the grafted and nongrafted atrophic posterior maxilla and to consider the acceptability of various fixed partial denture treatment options.

Materials And Methods: A computer model of the atrophic posterior maxilla was created from the computed tomography images of an actual patient. Three different treatment scenarios were modeled with partial denture restorations, grafted and nongrafted maxillary sinuses, and various implant inclinations. Oblique forces were applied to simulate chewing movements. Stress analyses were performed with a three-dimensional finite element analysis computer program, and the von Mises and minimum principal stresses on the implants and supporting tissues were compared.

Results: In all models, minimum principal (compressive) stress peak points were the highest within the crestal cortical bone (49.761 MPa), lower within sinus cortical (14.144 MPa) and trabecular bone (4.347 MPa), and lowest within grafted bone (0.049 MPa). The second molar implant in the third model (5×11-mm implant, inclined 45 degrees) showed the highest von Mises stresses (499.50 MPa), and the second molar implant in the first model (6×5-mm implant) showed the lowest (219.63 MPa) von Mises stresses.

Conclusion: The stress absorption capacity of graft material is not sufficient and is much lower than that of other supporting tissues. For a fixed partial prosthesis, the use of short, wide implants with sinus floor bicortical fixation was found to be the most feasible approach for the atrophied posterior maxilla.