材料厚度对无托槽隐形矫治器固位力影响的实验研究

目的研究材料厚度对无托槽隐形矫治器在不同牙位脱位时固位力大小的影响，为临床设计附件及指导患者摘戴矫治器提供理论参考。方法制作标准下颌牙列阳模四副及相应的无托槽隐形矫治器四副。研究分为4组：1．00mm厚度无附件组，0．75mm厚度无附件组，1．00mm厚度有附件组，0．75mm厚度有附件组。采用万能材料试验机测试在不同牙位脱位时矫治器固位力的大小。结果不同材料厚度及附件设计影响下四组间矫治器固位力有统计学差异（F=10．10，P〈0．01）。附件能明显增加隐形矫治器固位力，1．00mm有附件组、0．75mm有附件组与其他无附件组比较，平均脱位力值大（P〈0．05）；1．00mm厚度有附件组比0．75mm厚度有附件组平均脱位力值大（P〈0．05）；脱位部位不同对固位力影响有统计学差异（F=12．03，P〈0．01），在第二磨牙颊侧及第一磨牙舌侧测试时平均脱位力值较小。结论附件能够显著增加隐形矫治器固位力；1．00mm厚度有附件隐形矫治器固位力较大。

Effect of thickness of the clear aligners on retentive force of the appliances

Objective To investigate the retentive force of China-made removable clear aligners of different thickness. Methods Four models of lower arch and their removable clear orthodontic appliances were produced. The appliance designs were divided into 4 groups： （1） 1.00 mm thickness without attachment; （2） 0. 75 mm thickness without attachment; （3） 1.00 mm thickness with attachment; （4） 0. 75 mm thickness with attachment. Repeated placement and removal were tested on 7 different points of appliances and retentive force was evaluated using a universal testing machine. Results Significant statistics difference were found among the 4 groups. The attachment could increase retentive force of the appliances. The group of 1.00 mm thickness has greater retentive force than 0. 75 mm group. The retentive forces at removing-points on buccal surface of second molar and lingual surface of first molar were smaller than that at other points. Conclusions China-made clear removable orthodontic appliances of 1. 00 mm thickness apply greater retentive force than 0. 75 mm thickness appliances. The attachments increase significantly the retentive force of the clear aligners. Removing the appliances from buccal or lingual surface of molar should be easier.