Department of Endodontology, Academic Center for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Amsterdam, The Netherlands.
Department of Endodontology, Academic Center for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Amsterdam, The Netherlands.
J Endod. 2018 Jan;44(1):120-125. doi: 10.1016/j.joen.2017.07.025. Epub 2017 Nov 2.
Water loss strongly affects the mechanical behavior of dentin. Micro-computed tomography (μCT) studies exploring the influence of endodontic procedures on root cracking often lack information on the hydration state of the scanned samples. This study explores the relationship between dehydration and crack formation in root dentin with and without endodontic instrumentation.
Fifty-three extracted teeth were used. Thirty canals were not instrumented, and 23 canals were instrumented with ProTaper files until F3. All teeth were imaged with visible light or x-rays, both moist (100% relative humidity) and after dehydration, thus allowing every tooth to serve as its own control. The presence of cracks was determined both before and after dehydration by microscopy on two-dimensional (2D) slices and in by μCT in three dimensions (3D). The μCT data were used to determine the total surface area of newly formed cracks after dehydration, which was correlated with dentin cross section.
Both 2D and 3D data revealed cracking with increasing dehydration. Drying led to damage in >50% of roots, with a significant number of cracks appearing within 24 hours of ambient air-drying at 35%-55% relative humidity. Some cracking was occasionally observed even within minutes. More cracks were identified in 3D by μCT as compared with 2D microscopy. A correlation was found between dentin cross section and the total newly formed crack areas.
Dehydration may induce cracks in dentin regardless of canal instrumentation. The in vitro observed correlation between root dentin mass and newly formed cracks implies that dehydration engenders stresses that may significantly damage roots.
水分流失会强烈影响牙本质的机械性能。在研究根管治疗程序对牙根裂纹影响的微计算机断层扫描（μCT）研究中，通常缺乏对扫描样本水合状态的信息。本研究探讨了未经根管器械处理和经根管器械处理的牙本质在脱水和裂纹形成之间的关系。
使用 53 颗离体牙。30 个根管未经器械处理，23 个根管用 ProTaper 锉扩至 F3。所有牙齿均在潮湿（100%相对湿度）和脱水后分别用可见光和 X 射线成像，从而使每颗牙齿都可以作为自身对照。通过二维（2D）切片显微镜和三维（3D）μCT 在脱水前后确定裂纹的存在。利用μCT 数据确定脱水后新形成裂纹的总表面积，并与牙本质横截面相关联。
2D 和 3D 数据均显示随着脱水程度的增加而出现裂纹。干燥导致超过 50%的牙根受损，在相对湿度为 35%-55%的环境空气中干燥 24 小时后，会出现大量裂纹。有时甚至在几分钟内就偶尔观察到裂纹。与 2D 显微镜相比，μCT 在 3D 中可识别出更多的裂纹。牙本质横截面与新形成的总裂纹面积之间存在相关性。
无论根管是否器械处理，脱水都可能导致牙本质出现裂纹。体外观察到的牙本质质量与新形成的裂纹之间的相关性表明，脱水会产生可能严重损坏牙根的应力。
