[Three-dimensional analysis for changes in dentigerous cyst-associated maxillary canines after marsupialization in adolescents].

OBJECTIVE: To observe three-dimensional changes of dentigerous cyst-associated maxillary canines (DCAMC) in adolescents after marsupialization by using cone beam computed tomography (CBCT).
 Methods: A total of 34 DCAMC patients with dentigerous cyst aged 10-14 were divided into central type and lateral type, while canines on the non-cyst side served as a control. A three-dimensional reference frame was set up to analyze the position, angle changes and influential factors for DCAMC by using CBCT before operation and in 3-6 month after operation.
 Results: 1) Compared with pre-operation, there was significant vertical movement in DCAMC after marsupialization. Tip of tooth moved labially while tooth axis inclined mesiodistally; 2) Horizontal, vertical movement and mesiodistal inclination of DCAMC were significantly greater than those in the health side; 3) Compared with the lateral type DCAMC, the central type DCAMC showed a significant changes in labial inclination; 4) Horizontal movement, mesiodistal and labial inclination of lateral type DCAMC were all evidently greater than those of the central type DCAMC; 5) Vertical movement and inclination of DCAMC after marsupialization were significantly correlated to the time interval (r=0.354, 0.374, both P<0.05), while vertical movement of cuspid in health side was significantly negative correlated with the patients' age and the level of root formation (r=-0.506, -0.721, both P<0.01).
 Conclusion: DCAMC in adolescents can obtain obvious changes in position and angles after marsupialization regardless of the level of root formation, which is beneficial for further orthodontic treatment.

[Three-dimensional morphological features of temporomandibular joint in skeletal malocclusion Class III patients with different vertical skeletal facial types].

OBJECTIVE: To investigate three-dimensional morphological features of temporomandibular joint in skeletal malocclusion Class III with different vertical skeletal facial types.
 Methods: A total of 46 adults with skeletal malocclusion Class III were enrolled and allocated into a normal-angle, a high-angle and a low-angle groups. All patients were undergone cone beam computed tomography (CBCT). Images of temporomandibular joint were reconstructed and analyzed by Invivo 5. Nine measurements relevant to the positions and forms of condyle as well as joint spaces were performed.
 Results: Significant differences were not observed between the 2 sides of each group among skeletal malocclusion Class III (P>0.05). Compared with the high-angle and normal-angle patients, the low-angle patients had larger superior spaces, bigger gradients of the articular tublecle, longer condyle, and larger internal spaces between the condyle and the fossa. Compared with the low-angle and normal-angle patients, the high-angle patients had smaller condylar antero-posterior diameters.
 Conclusion: Class III malocclusion patients with different vertical skeletal patterns have different positions and forms of condyles, which should be paid attention to in clinic.

[Esthetic evaluation of frontal smile on different crown heights of lateral incisor and canine].

OBJECTIVE: To investigate the effect of different crown heights of lateral incisor and canine on smile esthetics perception between orthodontists and patients.
 Methods: A total of 31 orthodontists and 56 patients on smile aesthetics perception were investigated. We adjusted the height of lateral incisor and canine to get 20 kinds of anterior tooth area morphology by Photoshop and asked interviewees to grade. Scores of satisfaction were recorded by Likert method.
 Results: Subjects in the 2 groups preferred smiles with upper anterior teeth edge parallel to lower lip. There was better acceptance for longer canines and less satisfaction at shorter lateral incisors in patients. Patients also got higher discrete degree of evaluation results and more rigorous about smile esthetics than orthodontists.
 Conclusion: Orthodontists and patients have different satisfaction at esthetics of anterior teeth. Esthetics preference should be considered in orthodontic treatment schedule.

[Characteristics of mandible and mandibular dentition according to vertical facial skeletal features of adolescents].

OBJECTIVE: We aim to examine teenagers with varying vertical facial skeletal types with near-normal occlusion. We further aim to identify and study mandibular morphology and dentition characteristics to establish normal ranges and variations for future clinical reference. METHODS: According to the results of the case studies, 42 adolescents with near-normal occlusion were divided into three groups, namely, low- (7 cases), average- (23 cases) and high-angle (12 cases) groups. We used Invivo 5 software for Digital Imaging and Communications in Medicine (DICOM) data to calculate the cant of occlusal plane, axis corner of L6, ∠L1/MP, ∠L6/MP, Balkwill angle and Bonwill triangle of each group. RESULTS: Markedly, the finding shows that the cant of occlusal plane and axis corner of L6 in the low-angle group were smaller than those of the other two groups. In the average-angle group, ∠L1/MP was larger than that of the high-angle group. Lastly, in the high-angle group, ∠L6/MP was smaller than those of the two other groups. On the one hand, these differences were considered statistically significant (P<0.05). On the other hand, other measurements show that these differences were considered statistically non-significant (P>0.05). CONCLUSIONS: In the low-angle group, the parallelisation of the occlusal plane tends to be more obvious compared with the two other groups. In the coronal section of the low-angle group, the axis of the mandibular first molar is up-right, whereas it is distally tilted in the sagittal section of the high-angle group. Furthermore, a number of differences are noted in the adult groups. Factors, such as aging and development in the craniofacial region, lead to changes in functional occlusion.

A squamous odontogenic tumor following an orthodontic micro-screw: A rare case report and review of the literature.

We reported a very rare case of squamous odontogenic tumor(SOT) in a 23-year-old female. The tumor arose after an implanting operation of an orthodontic micro-screw, and was definitely diagnosed by the histopathological examination. Based on the case report and a review of the literature, we discussed about the general features, differential diagnosis and pathogenesis of SOT.