Dr. MH. Nekoofar

DDS, MSc, DoIBoE, PhD

Tag: Microhardness

  • The Effect of Operator-Induced Variability on the Physical Properties of ProRoot MTA

    Abstract

    Aims: The aim of this study was to compare the influence of operators on the microhardness and compressive strength of mineral trioxide aggregate (MTA). Materials and Methods: Forty dental specialists were asked to prepare a series of MTA samples. The tested material was ProRoot MTA (DentsplyMaillefer, Switzerland). Each participant prepared one sample to a consistency they considered acceptable for use in practice(improvised group) and another one according to the manufacturer’s recommended water‑to‑powder(WP) ratio(pre‑weighed group). The samples were incubated at 37°C and 95% humidity for 4days. Parameters evaluated in this study were microhardness and compressive strength. Results: Operators mixed MTA samples with varying WP ratios. However, there was no significant difference between the microhardness and compressive strength values of MTA samples between the improvised, the pre‑weighed and the control groups. MTA was mixed in a thicker consistency than the manufacturers recommended ratio (0.33) by 62.5% of the operators. Conclusion: According to the results of this study, even though the WP ratios that were utilized in the clinical setting vary, microhardness and compressive strength values of MTA was not significantly affected.

    Keywords: Compressive Strength, Microhardness, MTA, Surface Microhardness, Water-to-Powder Ratio

  • Acid and Microhardness of Mineral Trioxide Aggregate and Mineral Trioxide Aggregate–like Materials

    The aim of this study was to compare the surface microhardness of BioAggregate, ProRoot MTA, and CEMCement when exposed to an acidic environment or phosphate-buffered saline (PBS) as a synthetic tissue fluid. Methods: Ninety cylindrical molds made of polymethyl methacrylate with an internal diameter of 6 mm and height of 4 mm (according to ASTM E384 standard for microhardness tests) were fabricated and filled with BioAggregate (n = 30), tooth-colored ProRoot MTA (n = 30), or CEM Cement (n = 30). Each group was then divided into 3 subgroups of 10 specimens consisting of those exposed to distilled water, exposed to PBS (pH = 7.4), or exposed to butyric acid (pH = 5.4). After 1 week the Vickers surface microhardness test was performed. Statistical analysis included 2-way analysis of variance, followed by post hoc Dunnett T3 in cases with lack of homoscedasticity and Tukey honestly significant difference in cases with homoscedasticity. 
    Results: The indentations obtained from the CEM Cement specimens exposed to an acidic pH were not readable because of incomplete setting. There was a significant difference between the microhardness of the materials regardless of the environmental conditions (P < .001). In all the environmental conditions, MTA had significantly higher and CEM Cement had significantly lower microhardness values (P < .001). All experimental cements had significantly higher microhardness values when exposed to PBS (P < .001) and had significantly lower microhardness values when exposed to butyric acid (P < .001). Conclusions: The surface microhardness of BioAggregate, ProRoot MTA, and CEM Cement was reduced significantly by exposure to butyric acid and increased significantly by exposure to PBS. In all environmental conditions, MTA had significantly higher microhardness values. (J Endod 2014;40:432–435)

     Acid and Microhardness of Mineral Trioxide Aggregate.pdf