Clear-aligner orthodontic treatment after condylectomy for patients with unilateral condylar hyperplasia: a Cone Beam Computed Tomography study

Objective To analyze the morphological changes in the mandible and condyle using cone-beam computed tomography (CBCT) before surgical treatment for unilateral condylar hyperplasia (S0), before orthodontic treatment (S1), and after orthodontic treatment (S2). Additionally, to identify potential differences in treatment outcomes among different subtypes of condylar hyperplasia (horizontal, vertical, and mixed types). Method A total of 26 patients who accepted condylectomy for unilateral condylar hyperplasia (UCH) and subsequent postoperative orthodontic treatment were included. Patients were classified into horizontal, vertical, and mixed subtypes. Basic demographic characteristics (age, gender) and CBCT data were collected for each patient at three stages: before surgical treatment for UCH and before and after orthodontic treatment. Three-dimensional reconstructions were performed to measure the following variables: distance from the condylar apex to the inferior border of the mandibular body (Co-T2), condylar length, ramus length (R3-T2), body length (Go-Me), bilateral mandibular angle height difference, bilateral height difference of the mesiobuccal cusp of the maxillary first molars, deviation of chin, anterior space (AS), superior space (SS), and posterior space (PS). Differences among all variables were analyzed and compared. Results Patients with horizontal-type UCH exhibited significantly greater bilateral mandibular angle height differences and ramus length differences compared to other subtypes, while no significant differences were observed in other variables among the three subtypes. Combined condylectomy for UCH and orthodontic treatment significantly improved bilateral mandibular angle height differences (P < 0.05) and chin deviation (P < 0.005), with minimal impact on the unaffected condyle. In patients with mixed-type UCH, condylar length and the height difference of the mesiobuccal cusp of the maxillary first molars showed significant improvement post-treatment (P < 0.05). Additionally, the articular superior and posterior spaces on the affected side significantly increased post-surgery (P < 0.01) but decreased after orthodontic treatment (P < 0.05). Changes in the joint spaces on the unaffected side were minimal, with only the articular posterior space on the unaffected side in vertical-type UCH showing significant changes (P < 0.05). Conclusion condylectomy of unilateral condylar hyperplasia effectively reduces the length of the affected condyle, reduce mandibular asymmetry and chin deviation, and has minimal impact on the unaffected condyle. Post-surgical orthodontic treatment eliminates dental compensation, adjusts occlusion, and further improves mandibular deviation. Additionally, the affected condyle undergoes adaptive remodeling in terms of morphology and position, and the unaffected condyle has no significant difference.