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）的矫治效率优势已得到学界广泛证实。尽管相关研究对此尚存一定学术争议，但临床结果证实，采用牙弓扩展策略可降低拔牙矫治的病例比例。
研究目的：本研究旨在对比接受传统结扎托槽（conventional ligating brackets, CL）治疗的患者，与接受自锁托槽联合超大尺寸弓丝治疗的患者，其牙弓横向与矢状向的矫治变化差异。
研究方法：研究样本取自同一位临床医生接诊的300例连续矫治病例，其中51例接受自锁托槽联合超大尺寸弓丝治疗，55例接受传统结扎托槽治疗，另设20例患者作为对照组。对所有患者的石膏模型进行扫描并测量牙齿解剖标志点，以确定治疗起始（T0）至治疗结束（T1）阶段的矫治变化。通过头颅侧位片分析下切牙角（IMPA）与下颌第一磨牙远中倾斜角（MAng）的变化情况。采用线性回归分析检验操作者内部信度。为确保三组患者在T0时基线特征可比，对所有测量指标采用95%置信区间（CI）的方差分析（ANOVA）进行验证。为评估各组T0至T1时段的矫治变化，采用95%置信区间的配对t检验（Student’s t-test）进行分析。最后，采用95%置信区间的方差分析与事后检验对三组的研究结果进行比较。
研究结果：两组治疗组（自锁托槽组与传统结扎托槽组）的所有横向测量变量均出现显著提升，仅自锁托槽组的下颌尖牙间距离除外。传统结扎托槽组T0至T1时段的下切牙角（IMPA）变化幅度更大，而自锁托槽组则出现了下颌第一磨牙远中倾斜角（MAng）的变化。
结论：自锁托槽联合超大尺寸弓丝治疗与传统结扎托槽治疗，均可使牙弓横向的各项指标得到提升，仅自锁托槽组的下颌尖牙间距离例外。与传统结扎托槽组相比，自锁托槽组的下切牙角（IMPA）变化差异更小，且该组出现了下颌第一磨牙远中倾斜角的变化。