Kim Kyung-Ho, Chung Chun-Hsi, Choy Kwnagchul, Lee Jeong-Sub, Vanarsdall Robert L
Department of Orthodontics, College of Dentistry, Yonsei University, Seoul, Korea.
Am J Orthod Dentofacial Orthop. 2005 Oct;128(4):477-82. doi: 10.1016/j.ajodo.2004.04.027.
The purpose of this study was to evaluate the effects of prestretching on time-dependant force decay of synthetic elastomeric chains.
Five-unit (12.5 mm) and 6-unit (15.5 mm) modules (Generation II, Ormco, Glendora, Calif) were prestretched 100% for 1 hour (n = 12), 24 hours (n = 12), 2 weeks (n = 12), and 4 weeks (n = 12) in 37 degrees C distilled water. The prestretched and unprestretched (control) modules were then stretched to 30 mm in 37 degrees C water, and their forces were measured at 0 hour, 1 hour, 24 hours, and weekly for 4 weeks with a digital force gauge.
The prestretched 5- and 6-unit modules yielded significantly lower initial force than the controls. All 5- and 6-unit prestretched and control groups showed substantial force decay during the first hour. However, at 1 hour, similar remaining forces were found in the 5-unit prestretched and control groups (P > .05), and small differences were seen in the 6-unit groups. The rates and patterns of force decay from 1 hour to 4 weeks were quite similar between the control and the prestretched modules of both the 5- and 6-unit groups.
The effects of prestretching on force decay of elastomeric chains were noted mainly in the first hour. Thus, the clinical value of prestretching a synthetic elastomeric chain is questionable.
本研究的目的是评估预拉伸对合成弹性链随时间变化的力衰减的影响。
将五单元（12.5毫米）和六单元（15.5毫米）模块（第二代，奥美科公司，加利福尼亚州格伦多拉）在37摄氏度的蒸馏水中分别预拉伸100%，持续1小时（n = 12）、24小时（n = 12）、2周（n = 12）和4周（n = 12）。然后将预拉伸和未预拉伸（对照）的模块在37摄氏度的水中拉伸至30毫米，并用数字测力计在0小时、1小时、24小时以及之后4周每周测量其力。
预拉伸的五单元和六单元模块产生的初始力明显低于对照组。所有五单元和六单元的预拉伸组和对照组在最初1小时内均表现出显著的力衰减。然而，在1小时时，五单元预拉伸组和对照组的剩余力相似（P > 0.05），六单元组存在微小差异。五单元和六单元组的对照组与预拉伸模块从1小时到4周的力衰减速率和模式相当相似。
预拉伸对弹性链力衰减的影响主要在最初1小时内出现。因此，预拉伸合成弹性链的临床价值值得怀疑。
