Rehabilitation of Atrophic Posterior Maxilla with Pterygoid Implants: A 3D Finite Element Analysis

Elizabeth Wilkirson/Ravi Chandran, DMD, PhD/Yuanyuan Duan, BDS, PhD: Purpose: Clinical cases have shown that pterygoid implants are a successful alternative solution for the rehabilitation of atrophic posterior maxillae; however, little research on the biomechanical behavior has been produced. This study created 3D models of pterygoid implant-supported prostheses and compared the stress and strain distributions in the pterygoid implants and surrounding bone using finite element analysis. Materials and Methods: Three-dimensional models of a standardized human skull, pterygoid implants, and conventional dental implants were created using Simpleware, based on microcomputed tomography (micro-CT) and CBCT images. Six constructs with varying implant positions and numbers were designed to simulate various clinical scenarios for patients with complete maxillary edentulism. Finite element volume meshes were created and exported to ABAQUS, where the modulus of elasticity and Poisson ratio were assigned for each respective structure. Two load scenarios were simulated with conditions as follows: (1) 150-N axial loading; and (2) 150-N axial loading with simultaneous 50-N lateral loading. Then, the Von Mises stress and maximum principle strain distributions for all models were collected, analyzed, and compared. Results: The maximum stress and strain in the pterygoid implants and surrounding bone under both loading scenarios were found in model 4, which had two pterygoid implants and two anterior implants, at the implant-abutment connection and crestal bone of the premolar region, respectively. The stress and strain in the pterygoid implants for all constructs analyzed were at values within the limit of material strength. Additionally, the stress and strain in the surrounding bone for all constructs analyzed were at values within the bone resorption threshold. The maximum stress in the surrounding bone for all models with pterygoid implants was lower than the stress in the control model, which contained no pterygoid implants. Conclusion: Pterygoid implants decreased the stress and strain level in the surrounding bone for all cases studied. Additional concern should be placed on the crestal bone of the premolar region and the implant-abutment connections of the pterygoid implants, since these locations had the highest recorded values.