Dental Specialty Centre, Brazilian Military Police, Minas Gerais, Brazil.
Department of Endodontics, Fluminense Federal University, Niterói, Brazil.
Int Endod J. 2022 Mar;55 Suppl 1:178-226. doi: 10.1111/iej.13660. Epub 2021 Nov 27.
The purpose of this narrative review was to discuss the scientific milestones that led to the current understanding of the root dentinal microcrack phenomenon based on the interplay between the usage of micro-computed tomography (micro-CT) as an analytical tool alongside a close-to-mouth experimental model. In 2009, reports on the development of dentinal microcracks in extracted teeth after root canal preparation triggered an awareness of the potential for vertical root fractures (VRFs) of endodontically treated teeth could be developed from defects created by the mechanical stress of nickel-titanium preparation systems on dentine. This assumption was taken for granted, even though no cause-effect relationship had been scientifically demonstrated. Since then, several studies using the sectioning method with extracted teeth have been published and the large discrepancy amongst their outcomes soon become evident. Moreover, the high frequency of reported dentinal microcracks largely contrasted with the clinical incidence of VRFs, raising doubts on their methodological reliability. Using micro-CT technology, it was demonstrated by several studies that, in extracted teeth, dentinal defects already existed before the endodontic procedures, indicating that the initial reports framed a non-existing cause-effect relationship between canal preparation and dentinal microcracks. Although these new findings contributed to a better comprehension of this phenomenon, the misconception that microcracks were the starting point for VRFs was only surpassed with a new in situ approach using fresh cadavers. Surprisingly, microcracks were not identified in sound teeth. As a conclusion, dentinal microcracks in extracted teeth can be considered a non-natural occurrence observed only in a laboratory set-up as a consequence of dehydration and storage conditions. Thus, dentinal microcracks shall not be considered as the starting point for VRFs as they do not manifest in non-extracted teeth. Identifying dentinal microcracks as a laboratory phenomenon highlights the impact of recent scientific developments to disclaim the clinical relevance of laboratory-obtained outcomes.
本文旨在通过探讨使用微计算机断层扫描（micro-CT）作为分析工具与接近口腔的实验模型之间的相互作用，来讨论导致当前对根管预备后牙本质根部微裂纹现象的科学认识的里程碑。2009 年，有关根管预备后提取牙中牙本质微裂纹发展的报告引发了人们的关注，即根管治疗牙的垂直根折（VRF）可能是由镍钛预备系统对牙本质产生的机械应力造成的缺陷引起的。尽管尚未从科学上证明因果关系，但这一假设被认为是理所当然的。从那时起，已经发表了几篇使用提取牙进行切片法的研究报告，其结果之间的巨大差异很快就变得明显了。此外，报告的牙本质微裂纹的高频率与 VRF 的临床发生率形成鲜明对比，这对其方法学的可靠性提出了质疑。使用 micro-CT 技术，几项研究证明，在提取的牙齿中，根管治疗前牙本质就已经存在缺陷，这表明最初的报告构建了根管预备与牙本质微裂纹之间不存在的因果关系。尽管这些新发现有助于更好地理解这一现象，但微裂纹是 VRF 起始点的误解仅被一项使用新鲜尸体的新原位方法所超越。令人惊讶的是，在健康的牙齿中没有发现微裂纹。总之，提取牙中的牙本质微裂纹可以被认为是一种非自然发生的现象，仅在脱水和储存条件下的实验室环境中观察到。因此，牙本质微裂纹不应被视为 VRF 的起始点，因为它们在未提取的牙齿中并不表现出来。将牙本质微裂纹识别为实验室现象突出了最近科学发展对否认实验室获得的结果的临床相关性的影响。
