Armstrong David, Shen Gang, Petocz Peter, Darendeliler M Ali
Department of Orthodontics, Faculty of Dentistry, Sydney Dental Hospital, The University of Sydney, Surry Hills, New South Wales, Australia.
Eur J Orthod. 2007 Oct;29(5):430-6. doi: 10.1093/ejo/cjm037. Epub 2007 Jul 27.
The placement of orthodontic brackets is guided either by localizing the centre of the clinical crown (CC) or by measuring the distance from incisal edge (ME). The purpose of this study was to examine if there are any significant differences in the accuracy of bracket positioning between these two techniques. Typodont models were simulated with a Class I malocclusion with severe crowding. Nineteen experienced orthodontists (12 males, seven females) with a mean age of 40.6 years bonded pre-adjusted straight-wire brackets (Victory MBT) on the typodonts. Each orthodontist was asked to bond 20 brackets on one typodont using the CC method and 20 brackets on another typodont using the ME method. The teeth were removed from the typodont and photographed for imaging analysis. The errors of bracket placement in the vertical, mesiodistal, and angular/tip dimensions were measured and the data were statistically assessed. An overall test of significance, using all the data, rather than the means, demonstrated a significant vertical difference between the CC and ME methods, with the ME method more accurate vertically (mean CC = 1.19, mean ME = 1.10, P = 0.002) but no significant differences for mesiodistal (mean CC = -0.08, mean ME = -0.05, P = 0.28) or for tip (mean CC = -1.61, mean ME = -1.35, P = 0.34) errors. Analysis of the overall means and the arches independently showed that there was no significant difference in bracket accuracy between the two techniques (P > 0.05). Analysis of the teeth individually showed that the ME method was better in the vertical positioning for several upper and lower anterior teeth (P < 0.01) and poorer for the upper first premolars. The mean time taken to bond the 20 brackets showed no significant difference between two methods (CC 28.53 +/- 9.51 versus ME 28.21 +/- 10.43 minutes, P > 0.05). It is suggested that bracket bonding guided by measuring the distance from incisal edge may result in improved placement for anterior teeth. Archwire bending or bracket repositioning is still necessary to compensate for the inaccuracies with both techniques.
正畸托槽的定位可通过确定临床冠中心（CC）或测量切缘距离（ME）来引导。本研究的目的是检验这两种技术在托槽定位准确性上是否存在显著差异。用伴有严重牙列拥挤的I类错颌畸形模拟牙颌模型。19名经验丰富的正畸医生（12名男性，7名女性），平均年龄40.6岁，在牙颌模型上粘结预调整直丝弓托槽（Victory MBT）。要求每位正畸医生使用CC法在一个牙颌模型上粘结20个托槽，使用ME法在另一个牙颌模型上粘结20个托槽。将牙齿从牙颌模型上取下并拍照以进行影像分析。测量托槽在垂直、近远中以及角度/倾斜维度上的定位误差，并对数据进行统计学评估。使用所有数据而非均值进行的总体显著性检验表明，CC法和ME法在垂直方向上存在显著差异，ME法在垂直方向上更准确（CC均值 = 1.19，ME均值 = 1.10，P = 0.002），但在近远中方向（CC均值 = -0.08，ME均值 = -0.05，P = 0.28）或倾斜方向（CC均值 = -1.61，ME均值 = -1.35，P = 0.34）的误差上无显著差异。对总体均值和牙弓分别进行分析表明，两种技术在托槽定位准确性上无显著差异（P > 0.05）。对各个牙齿进行分析表明，ME法在上下颌几颗前牙的垂直定位上更好（P < 0.01），而在上颌第一前磨牙上较差。粘结20个托槽的平均用时在两种方法之间无显著差异（CC法28.53 +/- 9.51分钟，ME法28.21 +/- 10.43分钟，P > 0.05）。建议通过测量切缘距离引导托槽粘结可能会改善前牙的定位。仍需要进行弓丝弯制或托槽重新定位以弥补两种技术的不准确性。
