Comparison of changes in the dental transverse and sagittal planes between patients treated with self-ligating and with conventional brackets

ABSTRACT Introduction: Several advantages have been established regarding the efficiency of self-ligating brackets (SL). In spite of some controversy surrounding this question in the literature, clinical results confirm that “arch development” requires fewer extractions. Objective: The objective of this study was to compare changes in the transverse and sagittal planes in patients treated with conventional ligating brackets (CL)as well as in patients treated with SL brackets and oversized arches. Methods: A sample was selected from a pool of 300 consecutive cases treated by a single clinician: 51 patients with SL brackets and oversized wires, and 55 with CL brackets. These two groups were compared with a control group of 20 patients. All plaster models were scanned and dental landmarks were measured to identify changes from commencement (T0) to conclusion (T1) of treatment. Lateral cephalograms were analyzed for changes in the lower incisor (IMPA) and the first lower molar distal angulation (MAng). Intraoperator reliability was tested with linear regression analysis. To assure all groups were comparable at T0, an ANOVA test with a 95%confidence interval (CI) was performed for all values. To assess changes from T0 to T1 in all groups, a Student’s t-test with 95% CI was used. Finally, results from the three groups were compared using an ANOVA-test (95% CI) and a post-hoc test. Results: Increases in all the transverse variables were recorded in the two groups treated (SL and CL), except for the lower intercanine distance in the SL group. IMPA difference from T0 to T1 was higher in the CL group, and molar distal angulation (MAng) took place in the SL group. Conclusions: Self-ligating brackets with oversized arches and conventional ligating brackets showed increases in all variables in the transverse plane, except for the SL group at the mandibular intercanine distance. In comparison with the CL group, fewer different IMPA values were observed in the SL group, in which distal molar angulation occurred.

摘要
引言：自锁托槽（self-ligating brackets, SL）的矫治效率已被证实具备多项优势。尽管学界对此问题尚存争议，但临床结果证实，“牙弓扩展”所需的拔牙操作更少。
研究目的：本研究旨在对比传统结扎托槽（conventional ligating brackets, CL）组与自锁托槽配合超尺寸弓丝组患者的横向与矢状向平面变化。
研究方法：样本取自同一位临床医师连续接诊的300例病例，其中自锁托槽配合超尺寸弓丝组51例，传统结扎托槽组55例，另设20例患者作为对照组。对所有石膏模型进行扫描，并测量牙体标志点，以明确矫治起始（T0）至矫治结束（T1）的各项变化。通过头颅侧位片分析下切牙指标（IMPA）与下颌第一磨牙远中倾斜角度（MAng）的变化情况。采用线性回归分析检验术者自身测量信度。为确保三组在T0时具有可比性，对所有指标采用95%置信区间（confidence interval, CI）的方差分析（ANOVA test）进行验证。为评估各组T0至T1的变化情况，采用95%置信区间的配对t检验（Student’s t-test）。最后，采用95%置信区间的方差分析及事后检验（post-hoc test）对三组结果进行比较。
研究结果：两组矫治组（自锁托槽组与传统结扎托槽组）的所有横向测量指标均出现升高，自锁托槽组的下颌尖牙间宽度除外。传统结扎托槽组的IMPA从T0到T1的变化幅度更大，而下颌第一磨牙远中倾斜角度（MAng）的变化则出现于自锁托槽组。
结论：自锁托槽配合超尺寸弓丝与传统结扎托槽均可使横向平面的各项指标出现升高，仅自锁托槽组的下颌尖牙间宽度除外。与传统结扎托槽组相比，自锁托槽组的IMPA变化差异更小，且该组出现了下颌第一磨牙远中倾斜角度的变化。