Biocompatibility of Accelerated Mineral Trioxide Aggregate in a Rat Model

Introduction: The purpose of this study was to evaluate the biocompatibility of gray mineral trioxide aggregate (MTA) mixed with selected accelerants by examining the inflammatory response through histological analysis after implantation into rat mandibles. Methods: Sixty rats were randomly divided into experimental groups of calcium chloride (CaCl(2)), calcium nitrite/nitrate (CaN/N), or calcium formate (CaF) mixed with MTA and compared with controls of MTA mixed with sterile water (MTA control) and unfilled osteotomies. Material was implanted into an osteotomy prepared between the roots of the mandibular molars and the incisors in the mandible. After 2 or 8 weeks, tissues were collected and processed for hematoxylin and eosin staining and light microscopic evaluation. Blinded evaluators graded the inflammatory response along the MTA-bone interface on an ordinal scale. Data were analyzed using the Kruskal-Wallis test, and interobserver agreement was determined by the kappa analysis. Results: Interobserver agreement was good with kappa = 0.72. No statistically significant differences were noted between experimental and control groups at the 2-week time point (p > 0.05). At this time, all groups displayed a range of inflammatory responses from none to severe with mostly mild to moderate reactions. At the 8-week time point, the inflammatory reaction of CaF mixed with MTA was statistically different from the controls (p = 0.03). CaCl(2) and CaN/N were not statistically different from the controls, and the MTA control displayed no inflammation at this time point. Conclusions: The findings of this study indicate that MTA mixed with accelerants may be a biocompatible alternative when a rapid set is indicated clinically. (J Endod 2010;36:1851-1855)