Nekoofar M H, Adusei G, Sheykhrezae M S, Hayes S J, Bryant S T, Dummer P M H
Endodontology Research Group, School of Dentistry, Cardiff University, Cardiff, UK.
Int Endod J. 2007 Jun;40(6):453-61. doi: 10.1111/j.1365-2591.2007.01236.x. Epub 2007 Apr 24.
To examine the effect of condensation pressure on surface hardness, microstructure and compressive strength of mineral trioxide aggregate (MTA).
White ProRoot MTA (Dentsply Tulsa Dental, Johnson City, TN, USA) was mixed and packed into cylindrical polycarbonate tubes. Six groups each of 10 specimens were subjected to pressures of 0.06, 0.44, 1.68, 3.22, 4.46 and 8.88 MPa respectively. The surface hardness of each specimen was measured using Vickers microhardness. Cylindrical specimens of 4 mm in diameter and 6 mm in height were prepared in polycarbonate cylindrical moulds for testing the compressive strength. Five groups of 10 specimens were prepared using pressures of 0.06, 0.44, 1.68, 3.22 or 4.46 MPa. Data were subjected to one-way anova. The microstructure was analysed using a scanning electron microscope (SEM) after sectioning specimens with a scalpel.
A trend was observed for higher condensation pressures to produce lower surface hardness values. A condensation pressure of 8.88 MPa produced specimens with significantly lower values in terms of surface hardness than other groups (P<0.001). A condensation pressure of 1.68 MPa conferred the maximum compressive strength; however, it was not statistically different. Higher condensation pressures resulted in fewer voids and microchannels when analysed with SEM. In specimens prepared with lower condensation pressures distinctive crystalline structures were observed. They tended to appear around microchannels.
Condensation pressure may affect the strength and hardness of MTA. Use of controlled condensation pressure in sample preparation for future studies is suggested.
研究凝结压力对三氧化矿物凝聚体（MTA）表面硬度、微观结构及抗压强度的影响。
将白色ProRoot MTA（美国田纳西州约翰逊城登士柏 Tulsa 牙科公司生产）混合并填充到圆柱形聚碳酸酯管中。每组10个样本，共6组，分别施加0.06、0.44、1.68、3.22、4.46和8.88 MPa的压力。使用维氏显微硬度计测量每个样本的表面硬度。在聚碳酸酯圆柱形模具中制备直径4 mm、高6 mm的圆柱形样本以测试抗压强度。使用0.06、0.44、1.68、3.22或4.46 MPa的压力制备5组每组10个样本。数据进行单因素方差分析。用手术刀切割样本后，使用扫描电子显微镜（SEM）分析微观结构。
观察到较高的凝结压力会产生较低的表面硬度值的趋势。8.88 MPa的凝结压力产生的样本在表面硬度方面显著低于其他组（P<0.001）。1.68 MPa的凝结压力赋予最大抗压强度；然而，无统计学差异。用SEM分析时，较高的凝结压力导致孔隙和微通道较少。在较低凝结压力制备的样本中观察到独特的晶体结构。它们倾向于出现在微通道周围。
凝结压力可能影响MTA的强度和硬度。建议在未来研究的样本制备中使用可控的凝结压力。
