Osseous changes of the mandibular condyle affect backward-rotation of the mandibular ramus in Angle Class II orthodontic patients with idiopathic condylar resorption of the temporomandibular joint

Objective: To evaluate whether osseous changes of the temporomandibular joint (TMJ) condyle affect backward rotation of the mandibular ramus in Angle Class II orthodontic patients with idiopathic condylar resorption (ICR). Methods: Twenty Japanese women with Class II malocclusion with ICR (ICR group) and 24 women with Class II malocclusion without ICR (non-ICR group) were examined. Pre-treatment panoramic radiographs were used to measure condylar ratios. Pre-treatment lateral cephalograms were used to evaluate maxillofacial morphology. Results: The ICR group had a significantly smaller condylar ratio, greater backward rotation of the ramus, less labially inclined upper incisors, and a steeper occlusal plane. The increased backward rotation of the ramus in the ICR group was significantly associated with a smaller condylar ratio. Conclusion: Angle Class II patients with ICR had shorter condylar height attributable to osseous changes of the TMJ condyle, and the shorter condylar height may affect subsequent backward rotation of the ramus.