Custom design of a temporomandibular joint prosthesis: A kinematic approach evaluated by finite element analysis.

Abstract

Statement of problem: Designing temporomandibular joint (TMJ) prostheses that accurately replicate natural kinematic movement and stress distribution remains a challenge because standardized methods for determining the prosthetic kinematic center are lacking. Current designs often rely on empirical placements without considering individualized kinematic parameters, which can compromise functionality and longevity.

Purpose: The purpose of this study was to establish an optimal prosthetic kinematic center location for a custom TMJ prosthesis based on invariant TMJ anatomic landmarks to improve design efficiency, kinematic accuracy, and standardization in patient-specific applications.

Material and methods: A woman diagnosed with TMJ dysfunction was selected for this study. A 3-dimensional model of her TMJ was reconstructed from computed tomography scans to create a custom prosthesis based on the Walter Lorenz model. Finite element analysis simulated mechanical responses to prosthetic kinematic center placements using anatomic references to guide positioning. Analyses included von Mises stress, minimum principal stress, and kinematic translation under set boundary conditions. The TMJ prosthesis was evaluated based on bone mechanical properties and constraints to replicate natural joint movement accurately.

Results: The optimized prosthetic kinematic center location improved anteroposterior movement, effectively addressing translational deficiencies often caused by lateral pterygoid muscle resection. Maximum von Mises stress was recorded at 31 MPa, and minimum principal stress at -52.68 MPa, both within the material's tolerance, confirming structural stability. These results demonstrate consistent stress distribution and alignment with natural TMJ kinematics, suggesting potential improvements in prosthetic performance and patient comfort.

Conclusions: This prosthetic kinematic center-based design approach enhances kinematic precision and biomechanical function in TMJ prostheses, closely aligning prosthetic movement with natural condylar action. The method provides a standardized framework for individualized TMJ prosthesis design, potentially extending prosthesis longevity and functionality. Studies with larger sample sizes are recommended to verify the clinical applicability and long-term benefits of this approach.