Tam Laura E, Lim Mindy, Khanna Swati
Restorative Dentistry, Faculty of Dentistry, University of Toronto, 124 Edward Street, Toronto, Ontario, Canada M5G 1G6.
J Dent. 2005 Jul;33(6):451-8. doi: 10.1016/j.jdent.2004.10.022. Epub 2004 Dec 19.
The objective of this study was to determine the effects of carbamide peroxide (CP) and hydrogen peroxide (HP) bleaching on the flexural strength (FS) and flexural modulus (FM) of dentin.
2x2x20mm bovine dentin specimens were immersed in the bleaching agents to simulate overnight (10 or 15% CP, 6h daily, 2 weeks), exaggerated overnight (10% CP, 6h/day, 5 days/week, 2 months), daytime (6.5 or 7.5% HP, 1h daily, 3 weeks) and in-office (35% HP, 1h/day, 2 days/week, 3 weeks) treatment protocols. Distilled water (DW) and a placebo gel acted as control immersion materials. After immersion, the specimens were rinsed and stored in DW. Mechanical testing was performed 24h after the last treatment using an Instron Universal Testing Machine with a crosshead speed of 0.75 mm/min. The results were analyzed by ANOVA and Tukey's tests (p<0.05).
There were significant reductions in the FS and FM of dentin after 2-week and 2-month exposures to CP. There were no significant differences in the FS or the FM of the dentin among the HP treatment and control groups.
Direct in vitro application of CP bleaches caused significant decreases in dentin FS and FM. Similar decreases were not observed among the HP-treated dentin groups, which were exposed to shorter treatment times. Further research is needed to determine the effect of CP and HP on dentin in vivo.
本研究的目的是确定过氧化脲（CP）和过氧化氢（HP）漂白对牙本质弯曲强度（FS）和弯曲模量（FM）的影响。
将2×2×20mm的牛牙本质标本浸泡在漂白剂中，以模拟过夜（10%或15% CP，每天6小时，共2周）、过度过夜（10% CP，每天6小时，每周5天，共2个月）、日间（6.5%或7.5% HP，每天1小时，共3周）和诊室（35% HP，每天1小时，每周2天，共3周）治疗方案。蒸馏水（DW）和安慰剂凝胶作为对照浸泡材料。浸泡后，将标本冲洗并保存在DW中。在最后一次治疗24小时后，使用Instron万能试验机以0.75 mm/min的十字头速度进行机械测试。结果通过方差分析和Tukey检验进行分析（p<0.05）。
在接触CP 2周和2个月后，牙本质的FS和FM显著降低。在HP治疗组和对照组之间，牙本质的FS或FM没有显著差异。
CP漂白剂的直接体外应用导致牙本质FS和FM显著降低。在治疗时间较短的HP处理牙本质组中未观察到类似的降低。需要进一步研究以确定CP和HP在体内对牙本质的影响。
