Introduction: The purpose of this study was to examine the effect of fetal bovine serum (FBS) on the setting of 2 white mineral trioxide aggregates (MTAs) and to determine if calcium chloride (CaCl2) alters the setting behavior of both MTAs under this condition. Methods: Two types of MTA cements (ProRoot MTA [Dentsply Tulsa Dental, Tulsa, OK] and MTA-Angelus [Angelus Dental Solutions, Londrina, Brazil]) were mixed with either distilled water (DW) or 10% CaCl2 solution. Mixed MTA was placed in a polyethylene mold, and each mold was then placed in saline or FBS-soaked Oasis. After storing for 4 days, the MTA samples were removed from the molds, and the microhardness was independently measured at 3 different levels: 0.5 mm, 2 mm, and 4 mm away from the bottom in contact with the immersion solution. Results: None of the samples mixed with DW and exposed to FBS for 4 days had set at the 0.5-mm and 2-mm levels. CaCl2 was effective in reducing (the 0.5-mm level) or eliminating (the 2- and 4-mm levels) the adverse effect of FBS. The groups with short-term exposure to FBS had the same surface microhardness as the groups stored in saline-soaked Oasis. Conclusions: MTA did not set when the mixed MTA was exposed to FBS for 4 days. In these cases, 10% CaCl2 helped the setting of MTA, and the effect was more pronounced in ProRoot MTA than in MTA-Angelus. In contrast, short-term exposure to FBS had minimal or no detrimental effects on the setting behaviors of both MTAs.
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