Comparative biomechanical analysis of all-ON-4® and trefoil™ implant treatment protocols

Objective: The objective is to evaluate the stresses on bone, implant, implant components, and the prosthesis under an oblique force applied by immediate loading of All-on-4 system, the Trefoil concept, and 5-implant-supported treatment allowing hybrid prostheses in edentulous mandible, using finite element stress analysis. Material and Method: A fully edentulous atrophic mandible model was formed digitally. For All-on-4 and 5-implant-supported models, 11.5-mm long implants having a diameter of 5.0-mm placed between mental foramina were used, with 30°-angle multi-unit abutments in the posterior region. In the Trefoil system, 11.5-mm long Trefoil implants having a diameter of 5.0-mm were used. For the Trefoil model, a prefabricated titanium bar was modeled and applied as the infrastructure, and an immediate acrylic hybrid prosthesis was applied to all models. Applying 100-N oblique force to a 1.5-mm area in the distal triangular region of the first molar tooth to mimic chewing forces, the stress values and distributions in the implant, the bone, implant components, and the prosthesis were compared using finite element stress analysis. Results: The highest compressive and tensile stress values in the cortical and spongious bone were observed in the posterior implant in the All-on-4 model. The highest von Mises stress values were observed in the posterior implant in the All-on-4 model, and in abutment screws and protheses in the Trefoil model. Conclusion: The risk of bone, implant, and abutment complications is higher in the All-on-4 treatment protocol, and the risk of the prosthesis and abutment-screw complications is higher in the Trefoil treatment protocol. Key Words: All-on-4, trefoil, immediate loading, finite element stress analysis.