Synthesis of a Ca₃ SiO₅ -Ca₂ SiO₄ -Ca₃ Al₂ O₆ cement system with rapid setting capacity by spray-pyrolysis coupled with sol-gel method.

Abstract

A modified mineral-trioxide-aggregate (mMTA) with rapid setting capacity was newly synthesized by spray-pyrolysis following a sol-gel reaction. Its faster setting capacity and initially higher compressive strength compared with Portland cement (PC) were evaluated. The precursor solution of the mMTA was prepared through condensation following hydrolysis among Ca(NO₃ )₂ ·4H₂ O, Si(OC₂ H₅ )₄ , and Al(NO₃ )₃ ·9H₂ O under nitric acid. The mMTA powder was then synthesized by spray-pyrolysis at 1500°C. The particle shape was spherical with an average particle size of 0.8 ± 0.3 μm, while PC particles were irregular and 3.9 ± 3.0 μm in size. The mMTA consisted of mostly Ca₃ SiO₅ , Ca₃ Al₂ O₆ , and partial Ca₂ SiO₄ phases, while the PC comprised mainly Ca₃ SiO₅ , Ca₂ SiO₄ , and partial Ca₃ Al₂ O₆ phases. The final setting times of mMTA and PC measured under 95% relative humidity were about 11 min and 3 h, respectively. The early stage of setting in mMTA was dominated by the rapid formation of hexagonal-plate-like Ca₃ Al₂ O₆ ·6H₂ O crystals, while that in PC was dominated by needle-like calcium-silicate-hydrate gels and columnar-shaped Ca(OH)₂ crystals. The late stage of setting in mMTA was dominated by calcium-silicate-hydrate gels and Ca(OH)₂ crystals, while that in PC was dominated by Ca₃ Al₂ O₆ ·6H₂ O crystals. The compressive strengths of mMTA and PC after 30 min of setting were 4.5 and 0.2 MPa, respectively. The results suggest that mMTA has potential to be used as a filling material for accidental pulp-exposure or pulpal floor perforation cases that require rapid setting capacity and initial good strength. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1440-1451, 2019.