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.
Keywords: MTA; compressive strength; fast setting; sol-gel reaction; spray-pyrolysis.
© 2018 Wiley Periodicals, Inc.