Comparison of posterior support strategies with pterygoid implants for full-arch implant rehabilitation in the atrophic maxilla: a finite element study.

Abstract

<h4>Background</h4>Rehabilitation of the atrophic maxilla is challenging due to bone resorption and anatomical limitations. Although the All-on-Four concept offers a predictable treatment strategy, posterior cantilevers may increase biomechanical risk. Pterygoid implants have been proposed as an alternative to enhance posterior support without the need for bone grafting. This study aimed to compare stress distributions in bone and prosthetic components using three different implant-supported treatment strategies for the atrophic maxilla.<h4>Methods</h4>Three three-dimensional finite element models were developed based on cone-beam computed tomography scans of an edentulous maxilla. Model 1 included four implants following the All-on-Four protocol. Model 2 consisted of five implants, including two pterygoid implants for posterior support. Model 3 comprised six implants, also including two pterygoid implants. Stress distributions in cortical and trabecular bone, implants, abutments, and prosthetic frameworks were analyzed under oblique occlusal loading conditions.<h4>Results</h4>Model 3 demonstrated the most favorable biomechanical profile, with reduced maximum and minimum principal stresses and strain values in both cortical and trabecular bone. Model 1 exhibited the highest stress concentrations, particularly around posterior implants (up to 110 MPa) and prosthetic components (28-45 MPa), likely due to the cantilever effect. In contrast, Model 3 showed lower maximum principal stress in the cortical bone (0.4 MPa) compared to Model 1 (1.54 MPa). Additionally, the von Mises stress in the first and second implants decreased in Model 3 (28 MPa and 63.6 MPa, respectively) compared to Model 1 (39 MPa and 110.5 MPa) and Model 2 (20 MPa and 80.0 MPa).  In terms of strain distribution, all models remained within physiological thresholds but Model 3 exhibited a more balanced and uniform strain pattern, particularly around posterior implant sites. This suggests improved load transfer and reduced risk of biomechanical overload.<h4>Conclusions</h4>Increasing the number of implants and incorporating pterygoid implants enhances biomechanical stability in the atrophic maxilla. These strategies reduce stress and strain concentrations in both bone and prosthetic components and offer a less invasive alternative to bone grafting procedures. Optimizing implant number and posterior support is critical for improving long-term success in full-arch implant rehabilitation.