Three-dimensional analysis for changes in dentigerous cyst-associated maxillary canines after marsupialization in adolescents / 中南大学学报(医学版)

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.

Characteristics of mandible and mandibular dentition in patients with near-normal occlusion and different vertical facial skeletal types / 华西口腔医学杂志

Objective The aim of our work is to characterize individual normal occlusions to establish appropriate treatment standards for different vertical facial types. Methods A total of 30 patients with near-normal occlusion were grouped into high-angle group (eight cases), medium-angle group (12 cases), and low-angle group (10 cases) according to vertical facial skeletal type. Invivo5 software was used and digital imaging and communications in medicine data were rebuilt to measure the ∠L1/MP, ∠L6/MP, axis corner of L6, cant of occlusion plane, Balkwill angle, and Bonwill triangle of each group. Results Among the groups, the low-angle group had the smallest ∠L6/MP (P<0.05) and largest cant of occlusion. No significant difference was observed among the three groups with regard to the other parameters (P>0.05). Conclusion Patients with low-angle vertical facial skeletal type requires a modified treatment standard. In this group, the treatment standard must ensure that the cant of occlusion plane is more parallel to the Frankfurt horizontal plane compared with those of the other groups, and the axis of L6 is tilted distally relative to the mandibular plane.