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目的：研究模拟应用氟化物防龋的口腔环境下，不同浓度氟化物对镍钛拉簧的应力衰减的影响。方法：选取两种国内常用品牌0.010 inch 镍钛拉簧各40根，随机将每种拉簧平均分入四个浓度组（0.05 %、0.10 %、0.15 %和对照组），将相同浓度组的不同品牌弹簧分别固定于间距为20 mm 的四个支架的两端。将四个支架分别放入37 ℃人工唾液中水浴。将实验组按浓度分组放入不同浓度氟化人工唾液（0.05 %、0.10 %、0.15 %）中处理5 min，每天三次。分别于实验前、实验后1 周、2 周、3 周、4 周用拉伸机测量每根弹簧拉伸至20 mm 时的应力。对实验结果使用重复测量的方差分析。结果：时间因素对两种镍钛拉簧拉伸应力的衰减的影响有统计学意义，氟化物浓度有辅助效应，二者有交互作用。氟化物作用下不同品牌镍钛拉簧的应力腐蚀变化不同。（P<0.05)。结论： 1.氟化物的存在可以增加镍钛拉簧的应力衰减。2.在正畸治疗的临床工作中在使用氟化物时应考虑增加镍钛拉簧的更换频率。

英文摘要:

Objective:The main objective of this study was to examine stress decay of nickel titanium closed coil springs in solution environment of different medical concentrations of fluoride.Methods:Two domestic commonly used brands of 0.010 in nickel-titanium closed coil springs manufactured by different companies were selected. For each brand, 40 springs were randomly assigned into four concentration groups(0.05 %, 0.10 %, 0.15%and control group). The springs of each concentration groups were fixed to a bracket, and maintained in their stretched position between two hooks 20 mm apart. The four brackets were stored in 37 ℃ artificial saliva. According to different experimental groups, the brackets were kept in different fluoride artificial saliva (0.05 %, 0.10 %, 0.15 %) respectively for 5 min three times a day. Force measurements were performed at six time intervals (initial, 1 week, 2 weeks, 3 weeks, and 4 weeks). The experimental results were analyzed by ANOVA of repeated measurement data.Results:The impact of time factor of two nickel-titanium closed coil springs tensile stress decay was statistically significant. Fluoride concentration played as secondary effects of a cofactor. There was interaction between them. In fluoride environment, stress corrosion of different brand nickel-titanium closed coil springs is various (P<0.05).Conclusion:1.The presence of fluoride can increase stress decay of a nickel-titanium closed coil spring. 2 When using fluoride during the orthodontic treatment, nickel-titaniumclosed coil spring might be replaced more often.

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