Effect of BSSRO on disc-condyle relationship of the temporomandibular joint in skeletal Class III malocclusion patients

Purpose: To analyze dynamic and static changes in the disc-condyle relationship in patients with skeletal Class III malocclusion after orthognathic surgery.

Methods: The surgical group comprised 30 patients with skeletal Class III malocclusion, and the magnetic resonance imaging and mandibular movement data were obtained at T0 (preoperatively), T1 (3 months postoperatively), and T2 (at the end of orthodontic treatment). The control group included 20 patients with normal occlusion, and the mandibular movement data were recorded.

Results: The maximum mouth opening at T1 decreased compared with that at T0 and recovered close to the preoperative level at T2. The marginal movement of the mandible at T1 decreased compared with that at T0 (P > 0.05), among which the movement distances of the condyles during mouth opening and closing decreased significantly compared with those at T0(P < 0.05). Following postoperative orthodontics in patients with skeletal Class III malocclusion, RET-L was significantly lower than that in the control group(P < 0.05).Regarding the temporomandibular joint of ADDwR, the CPL at T1 decreased significantly compared with that at T0(P < 0.05). At T2, the LPM, LLM, and CPL increased significantly compared with those at T1(P < 0.05), and the LPM and LLM levels at T2 exceeded those at T0 significantly (P < 0.05).

Conclusions: In the short term, after orthognathic surgery, the marginal movement of the mandible showed a certain degree of decline; however, in the long term, it recovered or even exceeded the preoperative level. Orthognathic surgery results in a particularly significant improvement in the functional movement of the ADDwR joint. In addition, it improves TMD in patients with skeletal Class III malocclusion and has a positive effect on improving the position of the joint disc position.