Objectives

The objective of the present study was to elucidate the mechanism of bioactive molecule extraction from mineralized dentin by calcium hydroxide (Ca(OH)₂) and tricalcium silicate cements (TSC).

Methods and results

Transmission electron microscopy was used to provide evidence for collagen degradation in dentin surfaces covered with Ca(OH)₂ or a set, hydrated TSC for 1–3 months. A one micron thick collagen degradation zone was observed on the dentin surface. Fourier transform-infrared spectroscopy was used to identify increases in apatite/collagen ratio in dentin exposed to Ca(OH)₂. Using three-point bending, dentin exposed to Ca(OH)₂ exhibited significant reduction in flexural strength. Using size exclusion chromatography, it was found that the small size of the hydroxyl ions derived from Ca(OH)₂ enabled those ions to infiltrate the intrafibrillar compartment of mineralized collagen and degrade the collagen fibrils without affecting the apatite minerals. Using ELISA, TGF-β1 was found to be extracted from dentin covered with Ca(OH)₂ for 3 months. Unlike acids that dissolve the mineral component of dentin to release bioactive molecules, alkaline materials such as Ca(OH)₂ or TSC released growth factors such as TGF-β1 via collagen degradation.

Significance

The bioactive molecule extraction capacities of Ca(OH)₂ and TSC render these dental materials excellent for pulp capping and endodontic regeneration. These highly desirable properties, however, appear to be intertwined with the untoward effect of degradation of the collagen matrix within mineralized dentin, resulting in reduced flexural strength.

中文翻译：

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氢氧化钙和硅酸三钙水泥从矿化牙本质中提取生物活性分子的机理

目标

本研究的目的是阐明通过氢氧化钙（Ca（OH）₂）和硅酸三钙水泥（TSC）从矿化的牙本质中提取生物活性分子的机理。

方法与结果

透射电子显微镜用于提供证据证明胶原蛋白在覆盖有Ca（OH）₂或固定的水合TSC 1-3个月的牙本质表面降解。在牙本质表面观察到1微米厚的胶原蛋白降解区。傅里叶变换红外光谱用于确定暴露于Ca（OH）_2的牙本质中磷灰石/胶原蛋白比率的增加。使用三点弯曲，暴露于Ca（OH）_2的牙本质显示出明显的抗弯强度降低。使用尺寸排阻色谱法发现，小尺寸的Ca（OH）₂衍生的氢氧根离子使这些离子渗入矿化胶原蛋白的纤维内腔并降解胶原蛋白原纤维，而不会影响磷灰石矿物质。使用ELISA，发现从覆盖有Ca（OH）_2的牙本质中提取了3个月的TGF-β1 。与溶解牙本质的矿物质成分以释放生物活性分子的酸不同，诸如Ca（OH）₂或TSC之类的碱性物质通过胶原降解释放诸如TGF-β1之类的生长因子。

意义

Ca（OH）₂和TSC的生物活性分子提取能力使这些牙科材料非常适合牙髓封闭和牙髓再生。然而，这些高度期望的性质似乎与矿化的牙本质内胶原基质降解的不良作用交织在一起，导致抗弯强度降低。