MTA Setting Reactions Monitored for up to One Year

Dental literature suggests that Mineral Trioxide Aggregate (MTA), composed of modified Portland cement, bismuth oxide, and gypsum, continues to increase in mechanical properties for up to 1 month.  However, few studies, if any, have examined MTA's properties or setting reactions for longer periods.  This study reports continuing data (2007 IADR #2658) of MTA setting for up to one year.

Objectives:  To evaluate MTA setting reaction products for up to one year using differential scanning calorimetry (DSC).

Methods:  ProRoot MTA was prepared per manufacturer's instructions and placed in aluminum crucibles for DSC thermal analysis using a scan from 37°C to 640°C at 10^oC/min.  Specimens (n=3) were evaluated after 7 days, 1 month, 3 months, and 1 year of storage at 37^oC/100% humidity. DSC thermogram peaks were identified and integrated to yield enthalpy to serve as an indicator of reaction product formed over time.  Quantitative results were analyzed with ANOVA/Tukey (a=.05).

Results:  An endothermic peak at 450-550°C was identified and attributed to Ca(OH)₂ decomposition, a reaction product formed from hydration of MTA's calcium silicate constituents.  The observed enthalpy (mean ± standard deviation) associated with this peak is displayed. No significant difference (p>.05) in endotherm enthalpy was observed over time although a trend of less Ca(OH)₂ present at 3 months and 1 year is noted.