Discoloration of White Mineral Trioxide Aggregate With Various Radiopacifiers

Objectives: Mineral trioxide aggregate (MTA) is a widely used pulp capping material in endodontics. Although it has a high success rate, many cases of discoloration have been noted, mainly due to the use of bismuth oxide radiopacifier. This study aimed to investigate the color stability of white MTA using various radiopacifiers.
Methods: We chose three radiopacifiers, bismuth oxide (BM), zirconium oxide (ZO), and barium oxide (BO), and added them to MTA as 5, 10, 20, and 40 wt%, respectively. For the setting property, we used a fixed portion of calcium sulfate hemihydrate (5 wt%), and mixed the remaining with white Portland cement (90, 85, 75, and 55 wt%, respectively), and coded the compound with two capital letters of the radiopacifiers and its portion. The OrthoMTA^TM ([OM], BioMTA, Korea), and the no radiopacifier containing groups (NC) were used as control. We measured the radiopacity according to the International Organization for Standardization 6876 (2012), and observed the change in color after immersion (24 hours) in 5 % sodium hypochlorite (NaOCl) by viewing on digital photographs and using a spectrophotometer. The discoloration and radiopacity were analyzed using two-way analysis of variance followed by Tukey. The level of statistical significance was set at p<0.05.

Results: The BM containing groups were exhibited clinically perceptible discoloration after immersion in NaOCl; however, no discoloration was observed in various portions of the ZO and BO, OM, and NC containing groups (p>0.05). Regarding radiopacity, all the test groups showed more radiopacity compared to the NC group; however, the BO group showed irregular radiopacity.
Conclusions: We observed that in preventing discoloration with equivalent radiopacity, ZO showed a good potential to be used as a radiopacifier in white MTA.