Digital evaluation of the postoperative effects of orthognathic surgery on mandibular function in skeletal class III patients: a retrospective cohort study

Objectives Combined orthodontic-orthognathic intervention is the central approach for treating severe skeletal Class III malocclusion. This study quantifies longitudinally postoperative mandibular movement capacity as well as occlusal and condylar stability in patients with skeletal Class III using three-dimensional digital jaw-motion analysis. Materials and methods The study included 20 patients with skeletal Class III malocclusion undergoing orthognathic surgery and 20 patients in the non-intervention control group. Functional measurements were obtained in the intervention group at a preoperative baseline after orthodontic decompensation (T0), and at the following five defined postoperative time points: T1 (2–3 weeks), T2 (6 weeks), T3 (3–4 months), T4 (6–9 months) and T5 (12–15 months). The patients followed a standardised surgical and rehabilitation protocol. The mandibular movement capacity and the occlusal and condylar stability during mouth opening, protrusion and laterotrusion were assessed using the Zebris JMA Optic three-dimensional jaw registration system. These were then compared with those of the control group. Results Mandibular movement capacity decreased markedly during the early postoperative period and subsequently recovered in a movement-specific manner. At T5, mouth opening did not differ significantly from presurgical baseline ( p = 0.224) or the control group, whereas condylar excursion during mouth opening remained significantly reduced compared with controls. Protrusion ( p = 0.009) and right and left laterotrusion (both p = 0.002) exceeded baseline values and were comparable with controls at T5. Condylar recovery during protrusion and laterotrusion varied according to movement direction and side. Incisal-point stability improved from T0 to T5 across all movements ( p = 0.002–0.031), although residual differences from controls remained after mouth opening ( p = 0.003) and protrusion ( p = 0.030). Condylar stability showed no significant longitudinal changes (all p ≥ 0.052), but no significant differences from controls remained at T5. Conclusion Three-dimensional jaw movement analysis revealed movement-specific, time-dependent recovery over 12–15 months after orthognathic surgery in patients with skeletal Class III malocclusion. Selected protrusive and laterotrusive measures exceeded presurgical levels, whereas mouth opening recovery remained less complete. Overall, postoperative recovery is an ongoing adaptive process which can result in improved function compared to pre-surgery levels. This supports long-term functional monitoring and further comparative evaluation of treatment and retention protocols.