Tomographic Evaluation of TMJ Loading Affected by Occlusal Pivots

Purpose: The purpose of this study was to clarify the direction and magnitude of condyle displacement during clenching with occlusal pivots. Temporomandibular joint (TMJ) loading and flexibility and the clinical significance of orthopedic appliance therapy are also discussed. Materials and Methods: Participants were 16 volunteers with a mean age of 25.8 years. Maxillary and mandibular flat occlusal devices were fabricated. TMJ tomogram series were taken first with tripod support and then with maxillary clenched anterior pivot support and/or unilateral posterior pivot support. Condyle positions on the TMJ tomograms were analyzed using the digital subtraction technique. Results: When clenching with the anterior pivot, the anterior reference point (A) on the mandibular condyle was translated 0.1 mm posteriorly (P > 0.05) and 0.2 mm superiorly (P < 0.01) from the tripod-support reference point. In the case of the ipsilateral posterior pivot, point A was rotated 1.2 degrees (P < 0.01) and was translated 0.4 mm (P < 0.01) posteriorly and 0.18 mm superiorly (P > 0.05). Conclusion: Condyle displacement during clenching with the anterior and posterior unilateral pivot was found, which supports previous findings. However, the direction and magnitude of the displacement differed from those of previous studies using jaw-tracking devices, and individual values differed greatly among subjects.