Evolution of tricalcium silicate crystalline phase by differential scanning calorimetry for the development of endodontic calcium silicate-based cements

Abstract

Endodontic calcium silicate-based cement is the most used materials in root-end filling and/or repairing perforations. However, the relatively high cost associated with these cement is a drawback that necessitates improvements in their manufacturing process through the development of alternatives. This study used differential scanning calorimetry (DSC) and high-temperature X-ray powder diffraction observations of the tricalcium silicate (C3S) crystalline phase to identify and quantify important parameters of hydration reactions such as the degree of hydration. A C3S reference was prepared with pure chemical reagents to develop a novel biomaterial variety of calcium silicate-based cement which was predefined to preserve the significant properties and clinical applications typical of calcium silicates. A methodology of cycled synthesis was used to obtain almost pure, highly crystalline C3S phase. With temperatures that can reach 1450–1500 °C, the thermal processing of the mixture of raw materials gives rise to thermochemical reactions of the formation of the main phases: 2CaO·SiO₂ (C2S), 3CaO·SiO₂ (C3S), and 3CaO·Al₂O₃ (C3A). The formation of the C3S phase is aided by the fusion of calcium aluminates (C3A). The use of Al₂O₃ and MgO as liquid phase-forming agents and the stabilization of the phases in cooling, allowed the liquid phase to provide the greatest precipitation of the C3S solid phase of interest. The X-ray diffraction confirmed the formation of the highly C3S crystalline phase in the material after cooling at the end of the five thermal cycles. The results obtained indicated that such a material could be derived through bottom-up synthesis routes that aim to attain the proper balance between the C3S phase and the use of other cementitious materials.