The main objective of the present research study is to evaluate the association between the occurrence of buccally displaced canine (BDC) and the palatal as well as the craniofacial morphology in adolescents in accordance at the early permanent dentition. As the experimental group, 100 adolescents of Chinese ethnicity (mean age 13.05 years) with crowding and buccally displaced canine (BDC-c) were selected in comparison with the same number of candidates (mean age 12.59 years) without BDC and crowding as control group. Digital dental casts and cephalograms were collected for three dimensional (3D) and cephalometric measurements. An independent sample T-test was used to compare the cephalometric values between the two groups. Logistic regression as commonly statistical methods used in empirical study including categorical dependent variables was used to identify the joint effects of the dental variables' 3D measurements. When comparing the groups with above analysis, patients with BDC showed a statistically significant narrower and higher palatal vault. For the cephalometric variables, the anterior cranial base length, sagittal position of the maxilla (SNA), sagittal position of the mandible (SNB), and skeletal relationship between maxilla and mandible (ANB) appeared to be smaller, whilst palatal plane angle (SN-PP), Frankfort-mandibular plane angle (FMA), anterior facial height, and lower facial height were larger in BDC-c control group (p < 0.05). A smaller inter-first premolar width was significant in the prediction model (p = 0.002). This study highlights that BDC-c participants in early permanent dentition exhibited a narrower dental arch and higher palatal vault, of which a smaller inter-first premolar width would significantly increase the occurrence of BDC.

Objective To investigate the effects of cortical bone thickness (CBT), miniscrew implant root proximity (MRP) and other related factors on the success rate of miniscrew implant (MSI). Materials and Methods Four hundred and five MSIs placed in 171 patients were analysed in this retrospective study. The primary predictor variables were CBT and MRP at MSI insertion sites. The predictor variables also included patient, location, MSI design and procedure related factors. The outcome variable was the survival of MSI. The differences in measurement data between success group and failed group were evaluated by the analysis of variance and independent samples t tests. Patient, location, MSI design and procedure related factors associated with the MSI prognosis were analysed by survival analysis with Cox proportional hazard regression model. The P value was set at .05. And the survival curves of independent factors were plotted. Results The overall success rate of MSI was 82.7%. The age of MSI host, CBT, interdental root distance (IRD) and MRP at MSI sites showed no significant differences between failed group and success group. CBT and insertion jaws were independent prognosis factors screened out by Cox proportional hazard regression model. Failure risk (hazard ratio) of MSI with CBT <1 mm was 4.72. The failure risk in the mandible was 3.80 times as high as that in the maxilla. Conclusion Inadequate CBT (<1 mm) contributed to the failure of MSI. MSI placed in the maxilla showed better prognosis compared to the mandible. MRP had no significant effect on the prognosis.

头影测量是正畸医生诊断与治疗设计的重要手段,与传统二维头影测量相比,三维头影测量提供的信息更加准确、完整,但目前尚未形成统一的三维头影测量参考坐标系建立标准.为建立完善的三维头影测量参考坐标系,本文综述了锥形束CT三维头影测量中参考坐标系建立的研究进展,按包含整个颅面部的整体参考坐标系和针对不同面部单位的局部参考坐标系,分别研究了坐标系的建立、特点及应用,以期为三维参考坐标系的标准化、统一化提供参考.