Grigoratos D, Knowles J, Ng Y L, Gulabivala K
Department of Conservative Dentistry, Eastman Dental Institute for Oral Health Care Sciences, University College London, 256 Grays Inn Road, London WC1 8LD, England, UK.
Int Endod J. 2001 Mar;34(2):113-9. doi: 10.1046/j.1365-2591.2001.00356.x.
The aim of this study was to evaluate the effect of sodium hypochlorite (NaOCl) solutions (3%, 5%) and saturated calcium hydroxide (Ca(OH)2) solution, individually and consecutively, on the flexural strength and modulus of elasticity of standardized dentine bars.
Standardized plano-parallel dentine bars (n = 121) were divided into five test groups and one control group. The control group 1 consisted of dentine bars, stored in normal saline until testing. The dentine bars in the five test groups were treated by exposure to the following solutions; group 2--3% NaOCl, 2 h; group 3--5% NaOCl, 2 h; group 4--saturated Ca(OH)2 solution, 1 week; group 5--3% NaOCl, 2 h and then saturated Ca(OH)2 solution 1 week; group 6--5% NaOCl, 2 h and then saturated Ca(OH)2 solution 1 week. The dentine bars were then loaded to failure in a three-point bend test.
The data revealed a significant (P < 0.001) decrease in the modulus of elasticity and flexural strength of the dentine bars treated with 3% and 5% NaOCl. There was no significant difference in the flexural strength and the modulus of elasticity between the 3% and 5% NaOCl groups. Exposure to Ca(OH)2 significantly (P < 0.001) reduced the flexural strength but had no significant effect on the modulus of elasticity. The groups treated with sodium hypochlorite followed by calcium hydroxide did not have moduli of elasticity and flexural strengths that were significantly different from those treated only with sodium hypochlorite.
NaOCl (3 & 5%) reduced the modulus of elasticity and flexural strength of dentine. Saturated Ca(OH)2 reduced the flexural strength of dentine but not the modulus of elasticity. Sequential use of NaOCl and Ca(OH)2 has no additional weakening effect.
本研究旨在评估次氯酸钠（NaOCl）溶液（3%、5%）和饱和氢氧化钙（Ca(OH)₂）溶液单独及连续作用于标准化牙本质条的抗弯强度和弹性模量的效果。
将标准化的平行平面牙本质条（n = 121）分为五个试验组和一个对照组。对照组1由保存在生理盐水中直至测试的牙本质条组成。五个试验组中的牙本质条分别接受以下溶液处理：第2组——3% NaOCl，2小时；第3组——5% NaOCl，2小时；第4组——饱和Ca(OH)₂溶液，1周；第5组——3% NaOCl，2小时，然后饱和Ca(OH)₂溶液1周；第6组——5% NaOCl，2小时，然后饱和Ca(OH)₂溶液1周。然后在三点弯曲试验中将牙本质条加载至破坏。
数据显示，用3%和5% NaOCl处理的牙本质条的弹性模量和抗弯强度显著降低（P < 0.001）。3%和5% NaOCl组之间的抗弯强度和弹性模量没有显著差异。暴露于Ca(OH)₂显著降低了抗弯强度（P < 0.001），但对弹性模量没有显著影响。先用次氯酸钠再用氢氧化钙处理的组，其弹性模量和抗弯强度与仅用次氯酸钠处理的组没有显著差异。
NaOCl（3%和5%）降低了牙本质的弹性模量和抗弯强度。饱和Ca(OH)₂降低了牙本质的抗弯强度，但没有降低弹性模量。依次使用NaOCl和Ca(OH)₂没有额外的弱化作用。
