Micro-XRD Investigation of Phase Formation During Setting of MTA Flow™

MTA’s success in endodontics in combination with its inherent drawbacks have led to the development of countless derivatives. In vitro testing, specifically Micro‐X‐ray diffraction analysis (XRD), allows for efficient preliminary characterization of novel bioceramics and their proprietary mixes. Identifying phases thought to be responsible for MTA’s bioactivity through XRD provides insight into new materials’ efficacy. Methods: Ten human third molars were sectioned axially using a diamond saw (Isomet, Buehler). Three 3mm by 3mm cylindrical preparations were made in dentin to simulate root end preparations. MTA Flow™ (Ultradent) was injected into the preparations. The filled tooth-slot specimens were placed in simulated body fluid to maintain 100% humidity for three months. Micro-XRD patterns were obtained from the surface of MTA Flow™ after filling, 2hr, 4hr, 12hr, 1 day, 7 days, 1 month, and 3 months. The International Centre for Diffraction Data pure powder standards was referenced to index peaks for phase identification. The goodness-of-fit for the peak positions was compared. Micro-XRD patterns demonstrated continuous phase (di/tricalcium silicates) transformation up to 24 hours. Subsequently, the patterns stabilized, with little differences in the phases present from the 1-week to 3-month periods. The major final phases appeared to be tricalcium silicate, tricalcium aluminate and bismuth oxide. Conclusions: Use of the propitiatory gel accelerates the setting reaction of MTA Flow™ for the first 24-hour period, as evidenced by early crystalline phase formation. Some phases that formed during the first 24 hours became less evident at longer time periods.