Reactions of connective tissue to mineral trioxide aggregate and amalgam

The purpose of this study was to evaluate the subcutaneous connective tissue reactions to ProRoot, mineral trioxide aggregate (MTA; Dentsply), and Oralloy, high-copper amalgam (Coltene). These materials were placed in polyethylene tubes and implanted into dorsal connective tissue of Wistar albino rats, and tissue biopsies were collected and histologically examined 7, 15, 30, 60, and 90 days after the implantation procedure. The presence of inflammation, predominant cell type, calcification, and thickness of fibrous connective tissue were recorded. Scores were defined as follows: 0, none or few inflammatory cells, no reaction; 1, <25 cells, mild reaction; 2, 25 to 125 cells, moderate reaction; 3, greater than or equal to125 cells, severe reaction. Fibrous capsule was categorized as "thin" when thickness was < 150 mum and "thick" at > 150 mum. Necrosis and formation of calcification were recorded. Both materials were well tolerated by the tissues in a 90-day evaluation period. One notable finding is the presence of dystrophic calcification in connective tissue adjacent to MTA; this finding is consistent with the hypothesis of hard tissue induction by this material.