Hofpeter Kevin, Zehnder Matthias, Hülsmann Michael, Al-Jadaa Anas, Deari Shengjile
Division of Endodontology, Department of Conservative and Preventive Dentistry, Center for Dental Medicine, University of Zurich, Zurich, Switzerland.
Department of Clinical Sciences, College of Dentistry, Ajman University, Ajman, United Arab Emirates.
Int Endod J. 2024 Jan;57(1):78-86. doi: 10.1111/iej.13988. Epub 2023 Oct 15.
The aim was to develop a standardized curved root canal model in bovine dentine and to assess whether that natural substrate would behave differently from the resin in standard plastic training blocks when prepared chemo-mechanically. The impact of substrate microhardness on simulated canal transportation was considered.
High-precision computer numerical control (CNC) milling was used to recreate a simulated root canal from a resin training block (Endo Training Bloc J-Shape, size 15) in longitudinally sectioned, dis- and re-assembled bovine incisor roots. Optical overlays obtained from 10 resin blocks were used to identify an average canal and program the CNC milling apparatus accordingly. Resin and dentine microhardness were measured. Simulated root canals in resin training blocks and their bovine counterparts were then instrumented at 37°C using Reciproc R25 instruments (VDW) with water or 17% EDTA (n = 10). Open-access image processing software was used to superimpose and analyse pre- and postoperative images obtained with a digital microscope. Centering ratios were averaged to indicate canal transportation. The effects of substrate and irrigant on canal transportation were assessed by two-way anova.
Superimposed images showed that resin blocks under investigation varied considerably in terms of simulated canal length and curvature, whilst the milled canals were highly similar. The microhardness of dentine was more than three times higher than that of the resin. Conversely, canal transportation was considerably greater in dentine compared to resin, and in dentine had a tendency to be increased by EDTA. There was a strong effect of substrate on canal transportation (p < .001), no overall effect of irrigant, and a marginally significant interaction between irrigant and substrate (p = .077).
CNC milling allows to create standardized simulated curved root canals in bovine dentine. These models may be useful to test and compare materials and concepts of chemo-mechanical root canal instrumentation. Microhardness is a bulk feature that does not predict the response to chemo-mechanical instrumentation of a composite material such as dentine.
本研究旨在构建一个标准化的牛牙本质弯曲根管模型，并评估在化学机械预备时，这种天然底物与标准塑料训练块中的树脂相比，其表现是否不同。同时考虑了底物显微硬度对模拟根管偏移的影响。
采用高精度计算机数控（CNC）铣削技术，在纵向剖切、分离并重新组装的牛切牙根中，从树脂训练块（Endo Training Bloc J-Shape，尺寸15）中重建模拟根管。从10个树脂块获得的光学叠加图用于确定平均根管，并据此对CNC铣削设备进行编程。测量树脂和牙本质的显微硬度。然后在37℃下，使用Reciproc R25器械（VDW），分别用水或17%乙二胺四乙酸（EDTA）对树脂训练块中的模拟根管及其牛牙本质对应根管进行预备（n = 10）。使用开放式图像处理软件对数码显微镜获取的术前和术后图像进行叠加和分析。计算定心率的平均值以指示根管偏移情况。通过双向方差分析评估底物和冲洗液对根管偏移的影响。
叠加图像显示，所研究的树脂块在模拟根管长度和弯曲度方面差异很大，而铣削后的根管高度相似。牙本质的显微硬度比树脂高3倍多。相反，与树脂相比，牙本质中的根管偏移明显更大，并且在牙本质中，EDTA有增加根管偏移的趋势。底物对根管偏移有强烈影响（p < 0.001），冲洗液无总体影响，冲洗液与底物之间有微弱的显著交互作用（p = 0.077）。
CNC铣削技术可在牛牙本质中创建标准化的模拟弯曲根管。这些模型可能有助于测试和比较化学机械根管预备的材料和概念。显微硬度是一个整体特征，无法预测牙本质等复合材料对化学机械预备的反应。
