CaCO3 addition effect on the hydration and mechanical strength evolution of calcium aluminate cement for endodontic applications

Calcium aluminate cement (CAC) hydrates conversion can be inhibited by adding CaCO3, leading to C3A·CaCO3·11H (3CaO·Al2O3·CaCO3·11H2O) formation. However, despite its benefits, the stability of this monocarbonate hydrate is not fully understood, especially when the samples are kept in contact with liquid during the curing step. Thus, taking into account the increasing interest in the CAC application as a biomaterial in the endodontic area, this work addresses the evaluation of the mechanical strength and phase transformations of a commercial cement (Secar 71) containing 15 or 20 wt% of CaCO3. Compressive strength, apparent porosity, dimensional linear changes, X ray diffraction and thermogravimetric tests were carried out to evaluate samples immersed in water and kept at 37 °C between 1 and 30 days of curing. According to the collected results, CAH10 and C2AH8 formation were inhibited in CaCO3 containing compositions and the presence of the C3A.CaCO3.11H phase led to a significant cement mechanical strength increase. Nevertheless, the partial decomposition of this monocarbonate hydrate was detected at 37 °C in the range of 1–7 days and the continuous hydration of CA and CA2 also affected the compressive strength behavior of the evaluated samples.