Žižka Radovan, Čtvrtlík Radim, Tomaštík Jan, Fačevicová Kamila, Gregor Ladislav, Šedý Jiří
Institute of Dentistry and Oral Sciences, Faculty of Medicine and Dentistry, Palacky University, Olomouc, Czech Republic.
Czech Educational and Dental Research Innovative Group (CEDRIG), Brno, Czech Republic.
Iran Endod J. 2018 Winter;13(1):20-24. doi: 10.22037/iej.v13i1.15561.
The purpose of this study was to examine the microhardness and modulus of elasticity (MOE) of White ProRoot MTA (Dentsply Tulsa Dental, Tulsa, OK) after setting in moist or dry intracanal conditions.
To simulate root canal system, 14 polyethylen molds with internal diameter of 1 mm and height of 12 mm were used. These molds were filled with 9-mm thick layers of White ProRoot Mineral Trioxide Aggregate (MTA; Dentsply Tulsa Dental, Tulsa, OK). The experimental group (=7) had a damp cotton pellet with 1.5 mm height and a 1.5 mm layer of resin composite placed on it. In control group (=7) the whole 3 mm above MTA were filled with resin composite. The specimens were kept in 37C and relative humidity of 80% for 4 days in order to simulate physiological conditions. Specimens were longitudinally sectioned and nanoindentation tests were carried out using Berkovich indenter at loading rate of 2 mN/s at 4×5 matrices of indents which were located in the coronal, middle and apical thirds of the specimen's cross section, to evaluate the microhardness and modulus of elasticity of the specimen to appraise the progression of the setting process. Differences were assessed using nonparametric generalized Friedman rank sum and Wilcoxon Rank-Sum tests.
Statistical analysis showed that there was a significant difference in microhardness and MOE between control and experimental groups at coronal (<0.001), middle (<0.001) and apical (<0.001) thirds of the simulated rod from simulated apical foramen. Kruskal-Wallis test showed no significant effect of depth on microhardness of material in experimental or control groups.
Within limitations of this study, it seems that moist intracanal environment improves setting of MTA in various depths.
本研究的目的是检测白色ProRoot MTA（登士柏 Tulsa 牙科公司，塔尔萨，俄克拉荷马州）在潮湿或干燥的根管内环境中凝固后的显微硬度和弹性模量（MOE）。
为模拟根管系统，使用了14个内径为1毫米、高度为12毫米的聚乙烯模具。这些模具中填充了9毫米厚的白色ProRoot三氧化矿物凝聚体（MTA；登士柏 Tulsa 牙科公司，塔尔萨，俄克拉荷马州）层。实验组（n = 7）有一个高度为1.5毫米的湿棉球，并在其上放置一层1.5毫米厚的树脂复合材料。对照组（n = 7）在MTA上方整个3毫米的区域都填充树脂复合材料。为模拟生理条件，将标本置于37°C和80%相对湿度的环境中4天。将标本纵向切片，并使用Berkovich压头以2 mN/s的加载速率在标本横截面的冠部、中部和根尖三分之一处的4×5压痕矩阵上进行纳米压痕测试，以评估标本的显微硬度和弹性模量，从而评估凝固过程的进展。使用非参数广义Friedman秩和检验和Wilcoxon秩和检验评估差异。
统计分析表明，在模拟根管从模拟根尖孔开始的冠部（<0.001）、中部（<0.001）和根尖部（<0.001）三分之一处，对照组和实验组之间的显微硬度和MOE存在显著差异。Kruskal-Wallis检验表明，深度对实验组或对照组材料的显微硬度没有显著影响。
在本研究的局限性范围内，似乎潮湿的根管内环境可改善MTA在不同深度的凝固。
