FEA of Peri-Implant Stresses in Fixed Partial Denture Prostheses with Cantilevers

To compare stresses in the peri-implant bone produced by fixed partial prostheses with mesial and distal cantilevers, when cemented or screwed onto implants.

The experimental design consisted of four 3D models obtained by volumetric computerized tomography and analyzed using finite element analysis (FEA). Stresses were simulated in two stages. Stage 1 consisted of application of the preload. A 288 N load was applied to pillar screws of the cemented prosthesis, resulting in 389 MPa peak; 257 N was applied to the intermediate screw (multi-unit) resulting in 390 MPa peak; and 111 N was applied to the prosthesis infrastructure screw in the screwed prostheses, resulting in 390 MPa peak. In stage 2, the axial and oblique loads were applied. The axial load consisted of 50 N for molar implants and 30 N for premolar implants. The oblique load (on the buccal slope of the buccal cusp of each crown) consisted of 30 N for premolar implants and 50 N for molar implants, with a buccolingual vector at a 45° angle with the occlusal plane. The response variables were the axial and oblique stresses on the peri-implant bone, according to the following groups: group 1-models of fixed partial prostheses cemented onto implants with mesial or distal cantilevers; group 2-models of fixed partial denture screwed onto implants with mesial or distal cantilevers. Data were recorded, evaluated, and compared.

Oblique loads produced higher peak values than axial loads, and were located at the bone crest of the implant closest to the cantilever, regardless of the prosthesis type. In the cemented prosthesis models, oblique loads produced the highest peaks in the primary implant region when compared with the screwed prosthesis models.

The screwed fixed prostheses caused less stress on peri-implant bone regardless of whether the cantilever was located mesially or distally.