Objectives: To evaluate the condyle-fossa relationship in adolescents with various skeletal patterns using cone-beam computed tomography (CBCT). Materials and Methods: CBCT images obtained in 120 adolescent patients were used for this study. The patients were divided into 3 groups according to 3 criteria: (1) age (early, middle, and late adolescence); (2) facial height ratio or Jarabak quotient (hyperdivergent, normodivergent, and hypodivergent); and (3) ANB classification (Class I, Class II, and Class III). Temporomandibular joint space (TMJS: AS, anterior space; SS, superior space; PS, posterior space; MS, medial space; LS, lateral space), width and depth of the condyle (MLT, mediolateral thickness; APT, anteroposterior thickness), articular slope (ArS) and vertical height of the fossa (VHF) were measured and compared using CBCT. Results: Differences in condyle-fossa relationships were not significantly different between male and female adolescents, but were significantly different (P < .05) between left and right sides. The mean values showed no statistical differences according to age and skeletal pattern. Most measurements in the sagittal view showed that SS was the greatest, and the mean ratio of AS to SS to PS was 1.00 to 1.27 to 1.19, respectively. The mean values of coronal MS and LS were not significantly different. Conclusions: There were almost no statistical differences in the TMJS in adolescents across various factors except between left and right sides.

The purposes of this study were to establish normative data for mesiodistal tooth crown diameters and arch dimensions in Mongolian adults and to compare them with those of Japanese adults. The study materials comprised dental casts of 100 modern Mongolian and 100 Japanese subjects (50 males, 50 females for each) with Angle Class I normal occlusion. The mean ages were 20 years 8 months for the Mongolian subjects and 20 years 0 months for the Japanese subjects. On the dental casts, the mesiodistal tooth crown diameters (excluding wisdom teeth) and dental arch dimensions were measured. The following arch dimensions were measured: inter-canine lingual, inter-premolar lingual, inter-molar lingual, inter-molar central, coronal arch length, basal arch length, and basal arch width. In the Mongolian samples, significant sex differences were noted, and most of the items were significantly larger in males than in females. Significant differences between the Mongolian and Japanese samples were mainly noted in the premolar and molar regions, rather than in the anterior region, and were significantly smaller in the Mongolian samples. In the Mongolian samples, the molar section widths and basal arch width and length were significantly larger in males and females compared with the Japanese samples. These results suggest that the tooth crown size and arch dimensions in the Mongolian samples differed from those in the Japanese samples, and that establishment of the clinical norm for Mongolian adults might be helpful in formulating treatment plans for Mongolian patients, given that these parameters are the basic tools for diagnosis.

Treatment to improve malocclusion in patients with skeletal mandibular protrusion often involves the combined use of surgical treatment in orthodontic treatment to improve not only occlusion but also facial appearance. Mandibular setback surgery is known to cause displacement of the hyoid bone and affect the morphology of the respiratory tract. However, although there have been previous reports regarding displacement of the body of the hyoid bone, few reports have verified hyoid bone rotation taking complex muscle adhesion into consideration. Therefore, the aim of the present study was to comparatively investigate the position of the hyoid bone and morphological changes of pharyngeal airway taking preoperative and postoperative inclination into consideration in patients who underwent setback of the mandible with orthognathic surgery. The subjects comprised 14 patients who underwent sagittal split ramus osteotomy to treat skeletal mandibular protrusion, exhibited at least 8.0 mm (mean : 9.0mm) of mandibular retraction with model surgery directly before surgical treatment and consented to participate after being given an outline of this study. Data comprising lateral roentgenographic cephalograms taken directly before and one year after orthognathic surgery were used to measure reference points before and after surgery and measurement items determined with the following method. When analyzing hyoid bone displacement, the hyoid bone upper projection (H1) , lower projection (H2) and lowest point of the third cervical vertebra (C3) were set as reference points. Measurement items were ∠ NSH1, ∠ NSH2, ∠ H1C3H2, C3-H1 and C3-H2. Hyoid bone rotation and displacement of the body of the hyoid bone were then evaluated. Morphology of the pharyngeal airway was analyzed by measuring respiratory tract diameter before and after surgery in the nasopharynx region, soft palate area, uvula area, angle of mandible area and epiglottis area. Results indicated that ∠ NSH1 and ∠ NSH2 increased significantly.However, no differences were observed in ∠ H1C3H2, C3-H1 or C3-H2, with the results clarifying that the hyoid bone had moved downward and backward without rotating. Evaluation of pharyngeal airway morphology found no differences in APW1-PPW1 and APW2-PPW2, which correspond to the upper section of the pharyngeal airway but APW3-PPW3 and APW4-PPW4, which correspond to the middle section, and APW5-PPW5, which corresponds to the lower section, were found to have 1)

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