Bone and cortical bone characteristics of mandibular retromolar trigone and anterior ramus region for miniscrew insertion in adults.

INTRODUCTION: The aim of this study was to evaluate bone depth, cortical bone thickness, and vestibulolingual bone dimension of the mandibular retromolar trigone and anterior ramus region to evaluate what are its most suitable sites for miniscrew insertion in adults. METHODS: The sample included cone-beam computerized tomography (CBCT) records of 60 adult subjects retrospectively evaluated. All CBCT examinations were performed with the use of an i-CAT CBCT scanner (Imaging Sciences International). Each exam was converted into DICOM format and processed with the use of Osirix Medical Imaging software. On reproducible sagittal scan views, bone depth and cortical bone thickness were evaluated on specific lines parallel and at a 45° angle to the occlusal plane, and at 3 mm and at 6 mm distance from it. Vestibulolingual bone dimension was computed in 4 different cross-section scans and at 3 different levels of depth (0, 6, and 11 mm). RESULTS: All of the considered insertion sites showed on average more than 10 mm of bone depth. Inferential statistics showed significantly (P <0.05) greater bone depth (+3 mm) in cross-sectional scans parallel to the occlusal plane compared with those at a 45° angle to it. Cortical bone thickness showed average values from 3 mm to 5 mm. Vestibulolingual bone dimension showed a significant (P <0.05) reduction (-10 mm) in the posterior region of retromolar region. No significant differences were found between subjects with and without third molars. CONCLUSIONS: The retromolar trigone and anterior ramus region showed enough bone quantity and adequate bone quality for safe miniscrew insertion in adults.

In vitro evaluation of resistance to sliding in self-ligating and conventional bracket systems during dental alignment / 대한치과교정학회지

OBJECTIVE: To investigate the resistance to sliding (RS) in self-ligating and conventional ligation bracket systems at 5 different second-order bracket angulations by using low-stiffness alignment wires in a 3-bracket experimental model and to verify the performance of the main RS components in both systems when these wires are used. METHODS: Interactive self-ligating brackets with closed and open slides were used for the self-ligating (SL) and conventional ligation (CL) groups, respectively; elastomeric ligatures (1 mm inner diameter) were used in the latter system. The alignment wire used was 0.014 inch heat-activated NiTi (austenitic finish temperature set at 36degrees C by the manufacturer). A custom-made testing machine was used to measure frictional resistance. Tests were repeated 5 times at every angulation simulated. All data were analyzed statistically. RESULTS: The RS increased significantly with increasing angulation in both SL and CL groups (p < 0.0001). However, the RS values were significantly higher at every angulation (p < 0.0001) in the CL group. CONCLUSIONS: Despite the relevance of the binding phenomenon, ligation forces predominantly affect the RS when low-stiffness alignment wires are used.