Evaluation of the Effects of Hybrid Prostheses Prepared from Different Materials on Pterygoid and Cancellous – Anchored Posterior Maxillary Implants of Varying Lengths Using Three – Dimensional Finite Element Analysis

Introduction: The treatment of atrophic edentulous maxilla with implants becomes complex due to issues such as poor bone quality in the posterior region, insufficient bone volume, and anatomical constraints of the maxillary sinus. Rehabilitation using dental implants placed in the pterygomaxillary region posteriorly and between the maxillary sinuses anteriorly allows overcoming these limitations. Purpose: The aim of this study is to investigate the stresses generated in the bone, implant, substructure materials, and aesthetic materials of hybrid prostheses prepared from three  different substructure materials placed at different lengths in the pterygomaxillary region of completely edentulous maxillae using three-dimensional finite element analysis (FEA). Material and Methods: Implants of two different lengths, 11.5 mm and 18.0 mm, were placed in the pterygomaxillary region. The 18.0 mm long implant has bicortical anchorage. Hybrid prostheses were prepared using three different substructure materials: PEEK, Ti, and Zr. A force of 150 N was applied unilaterally at an angle of 30 degrees from the palatal direction to the buccal side. Results: Models with PEEK substructures exhibited greater displacement and shear stress values compared to those with Ti and Zr substructures. An increase in Von Mises stresses was observed in the apical region of the 18 mm long dental implants where cortical anchorage was achieved. In cortical bone, higher Pmax and Pmin values were noted in certain areas of the models with PEEK substructures. Conclusion: Different substructure materials have varying effects on the prosthesis, bone, and implant. It is suggested that the use of substructure materials with high elastic modulus would be more appropriate to reduce potential prosthetic complications in hybrid prostheses and achieve predictable stress distribution in the bone. The use of maxilla-restricted dental implants should be considered when sufficient cortical bone anchorage is present around the neck region of the implants. However, in cases where cortical bone support in the neck region is insufficient, the use of implants providing bicortical anchorage may be more beneficial.