Crack propagation is one of the issues associating with dental composites which can significantly affect their performance. Current solutions for preventing and stopping the cracks include maximizing the filler to matrix ratio as well as fiber reinforcing of composites which are not always reliable. The precipitation of calcium carbonate (CaCO3) minerals by the generally recognized as safe (GRAS) bacteria can be seen as a novel approach to address this shortcoming. In the present study, the effect of microbially induced calcium carbonate precipitation (MICP) on filling dental composites' cracks and cavities was studied. In this first step, the capability of different GRAS bacteria to induce CaCO3 precipitation was investigated. In the next step, the capability of potent bacteria to initiate MCIP in solid matrix was evaluated. For this purpose, the CaCO3-bacteria along with necessary nutrients were introduced into different dental composites in two ways, namely, powder and paste form. The light-cured composites were analyzed using optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDS) to identify and characterize the precipitated CaCO3 crystals. It was shown that the incorporation of powder healing compound in two composites resulted in precipitation of CaCO3, while no crystals were formed when a paste form of healing compound was mixed with composites. The results evidently show that MICP can be a feasible alternative to current inefficient approaches to address microcracking issues in dental composites.

中文翻译：

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微生物诱导的碳酸钙沉淀，以设计一种新型的生物自愈牙科复合材料。

裂纹扩展是与牙科复合材料相关的问题之一，它可能会严重影响其性能。当前用于防止和阻止裂纹的解决方案包括最大化填料与基体的比率以及复合材料的纤维增强，这些复合材料并不总是可靠的。通常被认为是安全（GRAS）细菌的碳酸钙（CaCO3）矿物的沉淀可被视为解决此缺点的一种新方法。在本研究中，研究了微生物诱导的碳酸钙沉淀（MICP）对填充牙科复合材料的裂缝和腔的影响。在第一步中，研究了不同GRAS细菌诱导CaCO3沉淀的能力。在下一步中，评估了有效细菌在固体基质中引发MCIP的能力。以此目的，CaCO3-细菌与必要的营养物质通过两种方式（粉状和糊状）引入不同的牙科复合材料中。使用光学显微镜，扫描电子显微镜（SEM）和能量色散X射线（EDS）对光固化的复合材料进行分析，以鉴定和表征沉淀的CaCO3晶体。结果表明，在两种复合材料中掺入粉末愈合剂会导致CaCO3沉淀，而将糊剂形式的愈合剂与复合物混合时则不会形成晶体。结果显然表明，MICP可以替代当前低效的方法来解决牙科复合材料中的微裂纹问题。使用光学显微镜，扫描电子显微镜（SEM）和能量色散X射线（EDS）对光固化的复合材料进行分析，以鉴定和表征沉淀的CaCO3晶体。结果表明，在两种复合材料中掺入粉末愈合剂会导致CaCO3沉淀，而将糊剂形式的愈合剂与复合物混合时则不会形成晶体。结果显然表明，MICP可以替代当前低效的方法来解决牙科复合材料中的微裂纹问题。使用光学显微镜，扫描电子显微镜（SEM）和能量色散X射线（EDS）对光固化的复合材料进行分析，以鉴定和表征沉淀的CaCO3晶体。结果表明，在两种复合材料中掺入粉末愈合剂会导致CaCO3沉淀，而将糊剂形式的愈合剂与复合物混合时则不会形成晶体。结果显然表明，MICP可以替代当前低效的方法来解决牙科复合材料中的微裂纹问题。结果表明，在两种复合材料中掺入粉末愈合剂会导致CaCO3沉淀，而将糊剂形式的愈合剂与复合物混合时则不会形成晶体。结果显然表明，MICP可以替代当前低效的方法来解决牙科复合材料中的微裂纹问题。结果表明，在两种复合材料中掺入粉末愈合剂会导致CaCO3沉淀，而将糊剂形式的愈合剂与复合物混合时则不会形成晶体。结果显然表明，MICP可以替代当前低效的方法来解决牙科复合材料中的微裂纹问题。