Effect of additives on the physical properties of mineral trioxide aggregate

Abstract

Mineral Trioxide Aggregate has gained popularity among clinicians, in respect to other endodontic materials, due to the superiority of its biological and physical properties. However, the main disadvantage of MTA is its prolonged setting time. MTA may gain wider acceptance in endodontic applications if its setting time could be shortened to a single appointment time frame. The purpose of this study was to investigate the effects of additives on setting time, strength, microleakage, and pH of an experimental version of Mineral Trioxide Aggregate (EMTA). The tested additives were 3%, 6%, 9%, 12%, 15%, 18% calcium chloride; 10%, 20%, 30% silicon; 10%, 20%, 30% Bioactive Inorganic Element (BIE); and were compared to control (EMTA). Setting time was determined by measurement of penetration depths at fixed intervals using a dial indicator microgauge. The biaxial flexural strength was determined with an Instron universal testing machine after 1, 7 and 21 days of setting. A fluid filtration method was used for quantitative evaluation of apical microleakage. The quality of seal of each specimen was measured after 1, 7, 14, 21, 28, 42 and 56 days. The pH of storage solutions of each specimen in 20 ml of deionized water was measured after 6 hours, 1, 2, 7 and 21 days. The data were statistically analyzed with both one-way ANOVA and Tukey’s HSD test methods. The results showed that the setting time and rate of EMTA was significantly shortened (p[less than]0.001) by the addition of calcium chloride at concentrations of 6% or greater. Calcium chloride also increased the rate of strength development by improving the 1 day biaxial flexural strength (p[less than]0.001); however, it exerted negative effects on the final strength values. Addition of silicon increased the final strength (p[less than]0.05), while BIE decreased the strength. The samples containing calcium chloride exhibited a better seal (p[less than]0.001) and were slightly less alkaline than the control. Under the conditions of this study it appears that addition of calcium chloride may shorten the setting time to a single treatment visit time frame, without adversely affecting the microleakage and physical properties of MTA.