Effects of orthodontic treatment with fixed functional orthopaedic appliances on the condyle-fossa relationship in the temporomandibular joint: a magnetic resonance imaging study (Part I)

This study aimed to verify the effects that corrective treatment for skeletal Class II malocclusions with fixed functional orthopaedic appliances has on the positions of the condyle within the glenoid fossa. Orthodontic treatment progress was monitored in 20 patients by magnetic resonance imaging (MRI) at four defined points in time. Metric analysis of the temporomandibular joints was performed on the central slices of the images obtained in the closed-mouth position. To assess the positional relationship between condyle and fossa, the width of the joint spaces was measured. To compensate for individual variation of the condyle sizes, the Joint Space Index was calculated. The displacement of the condyle from the fossa was measured in the ventral and in the caudal dimension and the effective condyle reposition was computed. Upon adoption of the therapeutic position, the condyles were displaced from the centric position within the fossa toward caudal and ventral. At the end of treatment, they returned to their original position. No significant differences compared with initial findings were found in the width of the anterior or posterior joint spaces. For patients who received functional orthopaedic treatment for skeletal Class II correction with a fixed functional appliance, reduction to a physiological condyle-fossa relationship occurred bilaterally in the region of the joints. Our study suggests that the improved dental occlusion was not achieved at the price of a change to an unphysiological position in the temporomandibular joints.