Abstract: Change the loading time of thin foil and compare the differentiation of tooth movement to investigate the relationship between effect of tooth movement and the loading time. Methods Totally 9 New Zealand white rabbits were selected，which were randomly assigned into 3 groups：experimental group 1 and 2，and control group，3 rabbits in each group. Then use clear aligners of 0.625mm and 0.75mm to move lower centrals of experimental group distalized to produce space in 12 days. Each step was designed 0.33mm tooth movement of lower centrals. At each step，the experimental group 1 had 4 steps and wore 0.625 mm aligner for 1 day and 0.75 mm for 2 days while the experimental group 2 had 3 steps and wore 0.625 mm and 0.75 mm aligner 2 days individually. The control group wore aligners without tooth movement in it. Measure the specific data of tooth movement after per step. And compare the amount, velocity and accuracy of tooth movement among three groups. Results The double-foil clear aligners could achieve the effective tooth movement，and compared with before orthodontic treatment，the amount of tooth movement had statistical significance（P < 0.05）. Compared with experimental group 2，experimental group 1 had higher tooth movement rate at the same site. There was no statistical difference in the amount of tooth movement per step in experimental group 1（P >0.05）， in which the loading time of thin foil was shortened. Compared with experimental group 2，experimental group 1 had slightly lower accuracy of tooth movement for the same step at the gingival point，while the accuracy was the same at the incisal and middle point. The tooth movement of experimental groups were both tipping，but there was no significant difference in tipping level. Conclusion Shorten the loading time of thin foil can improve the rate of tooth movement effectively without decreasing the amount of tooth movement ，but it may decrease the accuracy at the gingival point. Clinicians can shorten the loading time of thin foil properly to increase the tooth movement rate so as to shorten the period of treatment and provide better subjective feelings for patients，especially for cases with tipping movement.

Key words: clear aligners, thermoplastic materials, loading time, tooth movement

摘要： 目的 探讨不同双膜透明矫治器戴用时间对正畸牙移动效果的影响。方法 选取9只新西兰大白兔，随机分为实验1组、实验2组和对照组，每组3只。对两个实验组动物采用薄膜（0.625 mm）和厚膜（0.750 mm）两种厚度膜片透明矫治器进行矫治，均设计为每一步矫治使左右下中切牙各远中移动0.33 mm，总矫治时长为12 d；其中实验1组（缩短薄膜矫治器戴用时间）的每步矫治时长为3 d（薄膜矫治器1 d、厚膜矫治器2 d），共进行4步矫治；实验2组的每步矫治时长为4 d（薄膜矫治器2 d、厚膜矫治器2 d），共进行3步矫治。对照组配戴厚膜矫治器，但不进行牙移动。测量矫治前及每步矫治结束后实验动物临床冠切点、中点、龈点的牙移动相关指标。对实验组每一步矫治前后及两个实验组之间的牙移动量、牙移动速率及牙移动表达精确度进行比较分析。结果 （1）戴用双膜透明矫治器可有效完成牙移动，与矫治前比较，牙移动量具有统计学意义（P < 0.05）；（2）同一位点实验1组牙移动速率均高于实验2组（P < 0.05）；（3）实验1组缩短薄膜佩戴时间，与实验2组的单步矫治牙移动量差异无统计学意义（P > 0.05）；（4）在进行同一步骤矫治时，实验1组龈点牙移动表达精确度稍低于实验2组，在切点和中点两组的牙移动表达精确度无差异；（5）实验1组和实验2组的牙移动方式均为倾斜移动，且两组的倾斜程度差异无统计学意义（P > 0.05）。结论 （1）缩短薄膜戴用时间可有效提高牙移动速率，且牙移动量无明显差异，但龈点牙移动量表达精确度可能稍有降低；（2）临床可适当缩短薄膜戴用时间，以提高正畸牙移动速率，并可缩短疗程、优化患者感受，尤其适用于需要倾斜移动的病例。

关键词: 透明矫治器, 热压膜材料, 戴用时间, 牙移动