Biomechanical Evaluation of Temporomandibular Joint Implants Under Complete Mastication Cycle

Background To ensure the long-term success of temporomandibular joint implants, it is imperative to understand their biomechanical performances under the mastication cycle. Purpose This study aims to compare the biomechanical performance of two commercially available stock implants under a complete mastication cycle. This study has been further extended to understand the influence of bone-implant interface conditions on pre-clinical testing of implants. Methods In the present study, patient-specific QCT-based finite element models of a human mandible were developed. The left temporomandibular joint was virtually replaced by stock implants (narrow and standard). A complete mastication cycle involving six clenching tasks was simulated. A comparative biomechanical assessment between the intact and the implanted mandibles was performed based on maximum principal stress and strain distributions on the mandible. Results As compared to contralateral occlusion, ipsilateral clenching resulted in higher strains in the mandible. However, contralateral occlusion produced a larger von Mises stress on the implant than ipsilateral occlusion. Furthermore, intercuspal biting was found to have produced the highest strain (1750-1880 µ ε ) and stress (16.02-16.54 MPa) in the mandible. As compared to immediate post-operative non-osseointegrated conditions, an overall reduction of stress (narrow implant: 0.14 MPa; standard implant: 0.12 MPa) and strain (narrow implant: 30 µ ε ; standard implant: 20 µ ε ) was observed in post-operative osseointegrated phase. Conclusions Although stresses and strains in mandible and implants are reduced in osseointegrated condition, standard temporomandibular joint implant produced higher stresses in cortical bone compared to narrow implant during non-osseointegrated conditions, which suggests the possible preference of narrow implant over standard ones.