Wang Yu-Chih, Liou Eric J W
Department of Orthodontics and Craniofacial Dentistry, Chang Gung Memorial Hospital, Taipei, Taiwan.
Am J Orthod Dentofacial Orthop. 2008 Jan;133(1):38-43. doi: 10.1016/j.ajodo.2006.01.042.
A predrilled miniscrew, when used as a temporary anchorage device in the infrazygomatic crest of the maxilla, can be displaced under orthodontic loading. The purpose of this retrospective cephalometric study was to compare the loading behavior of predrilled and self-drilling miniscrews placed in the infrazygomatic crest of the maxilla.
The subjects were 32 women who had miniscrews in the infrazygomatic crest of the maxilla as skeletal anchorage for en-masse anterior retraction and intrusion; 16 had predrilled miniscrews, and 16 had the self-drilling type. The miniscrews were all 2 mm in diameter and 10 to 17 mm long. They were loaded with nickel-titanium closed-coil springs 2 weeks after placement. All the miniscrews remained stable, without detectable mobility or loosening, throughout the treatment period. Cephalometric radiographs were taken immediately before force application (T1) and at least 5 months later (T2). The T1 and T2 cephalometric tracings were superimposed to determine whether any displacement of the miniscrews had occurred.
The predrilled and self-drilling miniscrews were all significantly displaced in accordance with the force direction of the nickel-titanium coil springs. The amounts of miniscrew displacement were similar between the predrilled and self-drilling miniscrews, and were correlated to the length of the loading period. The displacements were 0.0 to 1.6 mm with extrusion, 1.5 mm with forward or backward tipping at the screw tail, and 1.5 mm with forward tipping at the screw head.
The loading behaviors of predrilled and self-drilling miniscrews were similar in the infrazygomatic crest of the maxilla. These miniscrews were all subject to displacement under orthodontic loading, and the amount of the displacement was correlated to the length of the loading period, although they remained stable without detectable mobility or loosening.
预钻孔微型螺钉作为临时支抗装置用于上颌颧下嵴时，在正畸加载力作用下可能会发生移位。本回顾性头影测量研究的目的是比较预钻孔微型螺钉和自攻型微型螺钉在上颌颧下嵴处的加载行为。
研究对象为32名女性，她们在上颌颧下嵴处植入微型螺钉作为整体前牙后缩和压低的骨骼支抗；其中16名植入预钻孔微型螺钉，16名植入自攻型微型螺钉。微型螺钉直径均为2mm，长度为10至17mm。植入2周后用镍钛闭合曲弹簧加载。在整个治疗期间，所有微型螺钉均保持稳定，未检测到松动或移动。在施加力之前（T1）和至少5个月后（T2）拍摄头影测量X线片。将T1和T2头影测量描记图叠加，以确定微型螺钉是否发生任何移位。
预钻孔微型螺钉和自攻型微型螺钉均根据镍钛螺旋弹簧的力方向发生明显移位。预钻孔微型螺钉和自攻型微型螺钉的微型螺钉移位量相似，且与加载期的长短相关。挤压移位为0.0至1.6mm，螺钉尾部向前或向后倾斜移位为1.5mm，螺钉头部向前倾斜移位为1.5mm。
预钻孔微型螺钉和自攻型微型螺钉在上颌颧下嵴处的加载行为相似。这些微型螺钉在正畸加载力作用下均会发生移位，移位量与加载期的长短相关，尽管它们保持稳定，未检测到松动或移动。
