Effect of bismuth oxide on white mineral trioxide aggregate: chemical characterization and physical properties

Aim To assess the effect of bismuth oxide ( B i 2 O 3 ) on the chemical characterization and physical properties of W hite mineral trioxide aggregate ( MTA ) A ngelus. Methodology Commercially available White MTA A ngelus and W hite MTA A ngelus without B i 2 O 3 provided by the manufacturer especially for this study were subjected to the following tests: R ietveld X ‐ray diffraction analysis ( XRD ), energy‐dispersive X ‐ray analysis ( EDX ), scanning electron microscopy ( SEM ), compressive strength, V ickers microhardness test and setting time. Chemical analysis data were reported descriptively, and physical properties were expressed as means and standard deviations. Data were analysed using S tudent's t ‐test and Mann–Whitney U test ( P  = 0.05). Results Calcium silicate peaks were reduced in the diffractograms of both hydrated materials. Bismuth particles were found on the surface of W hite MTA A ngelus, and a greater amount of particles characterized as calcium hydroxide was observed by visual examination on White MTA without B i 2 O 3 . The material without B i 2 O 3 had the shortest final setting time (38.33 min, P  = 0.002), the highest V ickers microhardness mean value (72.35 MPa, P  = 0.000) and similar compressive strength results ( P  = 0.329) when compared with the commercially available W hite MTA A ngelus containing B i 2 O 3 . Conclusion The lack of B i 2 O 3 was associated with an increase in V ickers microhardness, a reduction in final setting time, absence of B i 2 O 3 peaks in diffractograms, as well as a large amount of calcium and a morphology characteristic of calcium hydroxide in EDX / SEM analysis.