A CBCT evaluation of molar uprighting by conventional versus microimplant-assisted methods: an in-vivo study

ABSTRACT Objective: The aim of this prospective study was to compare the three-dimensional effects of the conventional helical uprighting spring (CA) and the mini-implant assisted helical uprighting spring (MIA), using CBCT scans. Methods: Twenty patients with mesially tipped second mandibular molars were divided into two groups: CA group, in which 10 patients were treated using a conventional helical uprighting spring with conventional anchorage; and MIA group, in which 10 patients were treated using a mini-implant supported uprighting spring. Molar uprighting was observed in both groups for a period of four months. Two standardized 11×5-cm CBCT sections of the mandible were taken, being one prior to uprighting and one at the end of the four month follow-up. Statistical analyses at the beginning of treatment and after a 4 month follow-up were performed, with a significance level of p< 0.05. Results: The mean amount of change in mesiodistal angulation in the MIA group was 8.53 ± 2.13o (p< 0.001) and in the CA group was 9.8 ± 0.5o (p< 0 .001). Statistically significant differences were found between the two groups with regard to buccolingual inclination of canine, first and second premolars (p< 0.05), second molar (p< 0.001) and extrusion of second molar (p< 0.05). Conclusions: The mean amount of change in the mesial angulation of the second molar in the CA as well as the MIA groups was similar. MIA, which used mini-implant as a source of anchorage, was more effective in preventing movement of the anchorage teeth as well as preventing extrusion of the second molar in the vertical plane, when compared to the CA group, which used dental units as a source of anchorage.

摘要
研究目的：本前瞻性研究旨在借助锥形束计算机断层扫描（cone beam computed tomography，CBCT），对比传统螺旋直立弓（conventional helical uprighting spring，CA）与微型种植体辅助螺旋直立弓（mini-implant assisted helical uprighting spring，MIA）的三维矫治效果。
方法：选取20例下颌第二磨牙近中倾斜患者，分为两组：CA组（传统螺旋直立弓组），共10例，采用传统螺旋直立弓配合常规支抗进行矫治；MIA组（微型种植体辅助螺旋直立弓组），共10例，采用微型种植体支持的直立弓进行矫治。两组均开展为期4个月的磨牙直立矫治。分别于矫治前及4个月随访结束时，拍摄2张标准化的11×5cm下颌骨CBCT断面图像。于治疗初始及4个月随访结束时进行统计学分析，检验水准设为p<0.05。
结果：MIA组下颌第二磨牙近远中向角度平均变化量为8.53±2.13°（p<0.001），CA组为9.8±0.5°（p<0.001）。两组在尖牙、第一及第二前磨牙的颊舌向倾斜度（p<0.05）、第二磨牙倾斜度（p<0.001）以及第二磨牙垂直伸长量（p<0.05）方面均存在统计学显著性差异。
结论：CA组与MIA组的下颌第二磨牙近中向角度平均变化量相近。相较于以牙体单位作为支抗来源的CA组，以微型种植体作为支抗来源的MIA在预防支抗牙移位以及防止第二磨牙垂直向伸长方面效果更优。