Department of Endodontics, Georgia Health Sciences University, Augusta, Georgia 30912-1129, USA.
J Endod. 2012 May;38(5):680-3. doi: 10.1016/j.joen.2011.12.036. Epub 2012 Jan 24.
Prolonged exposure of root dentin to calcium hydroxide alters the fracture resistance of dentin. Calcium silicate-based materials (CSMs) used in endodontics release calcium hydroxide on setting. This study examined whether prolonged contact of dentin with CSMs adversely affects its mechanical properties.
Dentin beams prepared from extracted human molars (7 × 3 × 0.3 mm) were divided into 3 groups on the basis of the material to which dentin was exposed (Biodentine, MTA Plus, and untreated control beams). Three-point flexure to failure was performed for each beam at designated exposure times (24 hours, 1, 2, and 3 months; n = 10). Data were analyzed with 2-factor repeated-measures analyses of variance to determine the effects of material and aging time on flexural modulus, flexural strength, and modulus of toughness (α = 0.05).
For flexural modulus, there was no significant difference for material (P = .947) or aging time (P = .064) when compared with baseline control. For flexural strength, significant differences were associated with aging time (P < .001) but not with material (P = .349). Flexural strength of dentin exposed to Biodentine decreased significantly after 2 and 3 months, whereas that exposed to MTA Plus decreased significantly after 3 months of aging (P < .05). For modulus of toughness, significant declines were observed for both material (P < .004) and aging time (P < .001).
Both CSMs alter material toughness more than the strength and stiffness of dentin after aging in 100% relative humidity. Because dentin toughness is attributed to its collagen matrix, the amount of collagen extracted from mineralized dentin and changes in collagen ultrastructure should be further examined after exposure of dentin to CSMs.
根牙本质长时间接触氢氧化钙会改变牙本质的抗断裂能力。在牙髓治疗中使用的硅酸钙基材料（CSMs）在凝固时会释放氢氧化钙。本研究检测了牙本质与 CSMs 长时间接触是否会对其机械性能产生不利影响。
从人磨牙中制备出 7×3×0.3mm 的牙本质梁，根据牙本质暴露的材料将其分为 3 组（Biodentine、MTA Plus 和未处理的对照组）。对每组牙本质梁在指定的暴露时间（24 小时、1、2 和 3 个月；n=10）进行三点弯曲失效测试。采用双因素重复测量方差分析来确定材料和老化时间对弯曲模量、弯曲强度和韧性模量的影响（α=0.05）。
对于弯曲模量，与基线对照组相比，材料（P=0.947）或老化时间（P=0.064）均无显著差异。对于弯曲强度，与老化时间（P<0.001）有关，而与材料无关（P=0.349）。暴露于 Biodentine 的牙本质的弯曲强度在 2 和 3 个月后显著降低，而暴露于 MTA Plus 的牙本质的弯曲强度在 3 个月老化后显著降低（P<0.05）。对于韧性模量，材料（P<0.004）和老化时间（P<0.001）都有显著下降。
在 100%相对湿度下老化后，两种 CSMs 都会改变牙本质的材料韧性，而不是牙本质的强度和刚度。由于牙本质的韧性归因于其胶原基质，因此应该进一步研究牙本质暴露于 CSMs 后从矿化牙本质中提取的胶原量和胶原超微结构的变化。
