A differential scanning calorimetry study of the setting reaction of MTA

P>Aim To evaluate the setting of mineral trioxide aggregate (MTA) at various time intervals using differential scanning calorimetry (DSC). Methodology Hydrated MTA and Portland cement were examined with DSC at the following intervals: immediate (0 h), 2 h, 4 h, 12 h, 24 h, 1 week, 1 month, 3 months and 1 year. DSC analysis consisted of a temperature scan from 37 to 640 degrees C, resulting in thermograms with reaction product decomposition endotherms. The thermogram peak attributed to calcium hydroxide product formation was identified and quantified to serve as an indicator of reaction product formation over time. Unmixed powders of both cements and individual components of MTA were also studied using DSC. The results were analysed with repeated measures anova between time intervals and a t-test between cements. Results A low temperature endotherm attributed to various calcium silicate hydrates showed continual maturation of MTA up to 1 year. The rate of calcium hydroxide formation was greatest between 4 and 24 h after mixing with maximum amounts present at 7 days. Specimens aged greater than 1 month showed a decrease in calcium hydroxide content, presumably because of carbonation reactions. Portland cement had similar thermogram peaks, although the amount of calcium hydroxide formed was generally smaller compared to MTA. The endothermic peaks from the various powders and components were helpful in corroborating the peaks formed in the hydrated cements. Conclusions Hydration reactions and structure maturation in MTA continue well beyond clinically observed setting times.