Objective To classify facial asymmetry (FA) phenotypes in adult patients with skeletal Class III (C-III) malocclusion. Methods A total of 120 C-III patients who underwent orthognathic surgery (OGS) and whose three-dimensional computed tomography images were taken one month prior to OGS were evaluated. Thirty hard tissue landmarks were identified. After measurement of 22 variables, including cant (°, mm), shift (mm), and yaw (°) of the maxilla, maxillary dentition (Max-dent), mandibular dentition, mandible, and mandibular border (Man-border) and differences in the frontal ramus angle (FRA, °) and ramus height (RH, mm), K-means cluster analysis was conducted using three variables (cant in the Max-dent [mm] and shift [mm] and yaw [°] in the Man-border). Statistical analyses were conducted to characterize the differences in the FA variables among the clusters. Results The FA phenotypes were classified into five types 1) non-asymmetry type (35.8%); 2) maxillary-cant type (14.2%; severe cant of the Max-dent, mild shift of the Man-border); 3) mandibular-shift and yaw type (16.7%; moderate shift and yaw of the Man-border, mild RH-difference); 4) complex type (9.2%; severe cant of the Max-dent, moderate cant, severe shift, and severe yaw of the Man-border, moderate differences in FRA and RH); and 5) maxillary reverse-cant type (24.2%; reverse-cant of the Max-dent). Strategic decompensation by pre-surgical orthodontic treatment and considerations for OGS planning were proposed according to the FA phenotypes. Conclusions This FA phenotype classification may be an effective tool for differential diagnosis and surgical planning for Class III patients with FA.

A 29-year-old female patient with unilateral condylar hyperplasia (UCH) of the left side presented with facial asymmetry, maxillary transverse occlusal plane (MXTOP) cant, posterior open bite, and Class III relationship. Treatment consisted of proportional condylectomy of the left condyle for management of UCH, and fixed orthodontic treatment with intrusion of the left maxillary molars to correct the MXTOP cant and remaining chin point deviation (CPD). Proportional condylectomy with a 14-mm resection of the left condylar head improved the CPD from 11.5 mm to 7.8 mm and resolved the posterior open bite on the left side. However, it produced a Class II relationship on the right and left sides, posterior open bite on the right side, and anterior open bite. Fixed orthodontic treatment with 1.8-mm intrusion of the left maxillary molars using miniscrews corrected the MXTOP cant from 3.5 mm to 1.7 mm, reduced the remaining CPD from 7.8 mm to 3.7 mm, produced counterclockwise rotation of the mandible, and resolved the posterior open bite on the right side and the anterior open bite. After 16 months of total treatment, normal overbite/overjet and Class I relationship were obtained. Treatment results were well maintained after 5 years of retention. For the correction of UCH, it is important to determine the amount of condylar head resection and accurately simulate the correction of CPD and MXTOP cant through intrusion of the maxillary molars.

The emergence time and development position of ST and the root development of IPT should be considered to determine the timing for the removal of ST and forced eruption of IPT.

ObjectiveThe purpose of this study was to compare the static (SFF) and kinetic frictional forces (KFF) of a computer-aided design and computer-aided manufacturing lingual bracket (CAD/CAM-LB) with those of conventional LB (Con-LB) and Con-LB with narrow bracket width (Con-LB-NBW) under 3 tooth displacement conditions.MethodsThe samples were divided into 9 groups according to combinations of 3 LB types (CAD/CAM-LB [Incognito], Con-LB [7th Generation, 7G], and Con-LB-NBW [STb]) with 3 displacement conditions (no displacement [control], maxillary right lateral incisor with 1-mm palatal displacement [MXLI-PD], and maxillary right canine with 1-mm gingival displacement [MXC-GD]; n = 6/group). While drawing a 0.016-inch copper or super-elastic nickel-titanium archwire with 0.5 mm/min for 5 minutes in a chamber maintained at 36.5℃, SFF and KFF were measured. The Kruskal-Wallis method with Bonferroni correction was performed.ResultsThe Incognito group demonstrated the highest SFF, followed by the 7G and STb groups ([STb-control, STb-MXLI-PD, Stb-MXC-GD] < [7G-MXC-GD, 7G-MXLI-PD, 7G-control] < [Incognito-MXLI-PD, Incognito-control, Incognito-MXC-GD]; p < 0.001). However, there were no significant differences in SFF among the 3 displacement conditions within each bracket group. Within each displacement condition, the Incognito group demonstrated the highest KFF, followed by the 7G and STb groups ([STb-control, STb-MXLI-PD] < Stb-MXC-GD < 7G-MXLI-PD < [7G-control, 7G-MXC-GD] < [7G-MXC-GD, Incognito-MXLI-PD, Incognito-control] < [Incognito-control, Incognito-MXC-GD]; p < 0.001). MXC-GD exhibited higher KFFs than MXLI-PD in the same bracket group.ConclusionsThe slot design and ligation method of the CAD/CAM-LB system should be modified to reduce SFF and KFF during the leveling/alignment stage.