Tilted Implants in Full-arch Fixed Prostheses: A Nonlinear FEA Study

Objectives: This nonlinear 3D-finite element analysis (FEA) study evaluated the effect of implant number and distal implant tilting on stress distribution in cortical peri-implant bone, abutment and prosthetic screws in mandibular full-arch fixed prostheses.
Methods: Six nonlinear 3D-FEA models with mandibular full-arch fixed prostheses were created with five, four or three parallel implants (5P, 4P, 3P) and with tilted distal implants (5T, 4T, 3T). A 100 N static load was applied at the first molar region (cantilever) of each model to compare the von Mises tensions in selected points: cortical peri-implant bone, abutment screw, and prosthetic screw.
Results: The implant adjacent to the loading area showed the highest stress magnitudes at the cortical peri-implant bone, abutment screw, and prosthetic screw for all models. For the abutment screw, peak stress increased 40% from five to four implants and 100% from five to three implants. Tilting the implants without distalizing the implant platforms increased Von Mises tensions in the cortical peri-implant bone region. For prosthetic screw, peak stress increased 150% from 5P to 5T and 100% from 4P to 4T.The prosthesis supported by three implants showed higher stress values than the models with four and five implants.
Conclusions: The results suggest that stresses in the cortical peri-implant bone, abutment and prosthetic screws increase with tilting the posterior implants without distalizing the implant platforms and reducing the number of implants.