Investigation of force distribution in hybrid prostheses with different designs supported by subperiosteal implants and manufactured from various substructure materials using the finite element analysis method

In this study, the effects of different substructure designs, substructure materials, and superstructure materials used in subperiosteal implant-supported hybrid prostheses on the stress distribution in the implant, substructure, superstructure, and bone were analyzed using the finite element stress analysis method. Ten virtual three-dimensional models of hybrid prostheses supported by subperiosteal implants were created for the rehabilitation of atrophic edentulous maxilla. Bar and Toronto designs were used as substructure designs, while cobalt-chromium (Co-Cr), zirconia (Zr), and polyetheretherketone (PEEK) were used as substructure materials, and polymethylmethacrylate (PMMA), zirconia, and lithium disilicate as superstructure materials. In the study, a rigid foodstuff with a radius of 1 cm was modeled, and a vertical force of 200 N was applied unilaterally to the foodstuff positioned between the second premolar and the first molar. As a result of the loading, the maximum and minimum principal stresses in the cortical bone around the osteosynthesis screws and the Von Mises stress values in the subperiosteal implant, substructure, and superstructure were analyzed. The results showed that bar substructure designs caused higher stresses in the bone compared to Toronto designs. Substructure materials with a higher modulus of elasticity were found to reduce stresses on the implant and superstructure but increased stresses in the substructure and bone. Superstructure materials with a higher modulus of elasticity did not significantly affect stresses on the bone and implant but reduced stresses in the substructure while increasing stresses in the superstructure. In conclusion, using rigid materials such as Zr and Co-Cr instead of PEEK, preferring the Toronto design over the bar design, and employing rigid superstructure materials such as zirconia and lithium disilicate instead of PMMA positively influenced the stress distribution and magnitude in the implant-prosthesis system.