Changes in condylar position during orthodontic treatment depending on the amount of incisor retraction: a cone-beam computed tomography study.

OBJECTIVES: Orthodontic treatment may be associated with temporomandibular disorders through changes in the condylar position. This study aimed to evaluate changes in the condylar position among different amounts of maxillary incisor retraction during orthodontic treatment using cone-beam computed tomography images. MATERIALS AND METHODS: Fifty-four participants were enrolled and divided into minimal (n = 14), moderate (n = 20), and maximal (n = 20) retraction groups based on the amount of incisor retraction (< 1, 1-6, and > 6 mm, respectively). Changes in condylar position before (T0) and after (T1) orthodontic treatment were assessed for the superior, anterior, posterior, and medial joint spaces (SJS, AJS, PJS, and MJS, respectively). Changes in joint spaces were compared between T0 and T1 in each group using paired t-tests and among the three groups using analysis of variance. RESULTS: Anterior movement of the condyle was observed in the maximal retraction group with a 0.2 mm decrease in ΔAJS and a 0.2 mm increase in ΔPJS, significantly greater than those in the minimal retraction group. The AJS and PJS showed statistically significant differences between T0 and T1 (P < 0.05) in the maximal retraction group. CONCLUSIONS: The condyle may show a statistically significant but clinically insignificant forward movement in the maximal incisor retraction group, whereas it was relatively stable in the minimal and moderate incisor retraction groups. CLINICAL RELEVANCE: More attention should be paid to the signs and symptoms of the condyle in patients with excessive incisor retraction during orthodontic treatment.

Mandibular Stability After Sagittal Split Ramus Osteotomy With Hybrid Technique in Asymmetric Patients.

ABSTRACT: The hybrid technique after bilateral sagittal split ramus osteotomy is an internal fixation method using monocortical mini-plates and additional bicortical positional screws. In this study, we analyzed the postoperative stability of 23 patients with mandibular asymmetry who underwent bilateral sagittal split ramus osteotomy and hybrid fixation with or without LeFort I osteotomy. Anatomical landmarks of the deviated and non-deviated sides of the jaw were established to measure the angle and distance to the reference plane in three-dimensional cone beam computed tomography images. We analyzed the positional changes and correlations of the reference points at preoperative (T1), postoperative 2 weeks (T2), and postoperative 1 year (T3). There were significant differences in preoperative position of the upper and lower molar cervix alveolar crest to the reference plane (U6-X and L6-X) and the condylion angles between deviated and non-deviated sides. Postoperatively (T2-T3), each reference point had no statistically significant positional change. Pearson correlation coefficient between the amount of menton deviation (ME-X at T1) and positional change of menton after surgery (T2-T3) was 0.30, and P value was 0.168. The hybrid fixation technique is an effective fixation method for achieving postoperative stability for mandibular asymmetry.