Methods: Silicon tubes were filled with either mineral trioxide aggregate (MTA; ProRoot® MTA, Dentsply Tulsa) or a hard-set calcium hydroxide cement (LifeTM, Sybron Kerr), and subcutaneously implanted into the back of Wistar rats (n = 9). As a control group, solid silicon rods were implanted in animals in the same manner. At 7, 14, and 28 days after the implantation (n = 3, each), connective tissues adjacent to the implants were retrieved. After the fixation of the samples, frozen tissue sections were prepared and double immunoperoxidase staining was carried out using ED1 (anti-macrophages and dendritic cells) and OX6 (anti-MHC class II molecules). Then, the density of ED1+/OX6- cells (MHC class II-negative macrophages), and ED1+/OX6+ cells (MHC class II-expressing macrophages and dendritic cells) was enumerated.
Results: At 7, and 14 days, the density of ED1+/OX6+ cells, and ED1-/OX6+ cells in MTA-implanted tissues was significantly higher than that in either or both Life-implanted and control tissues (P < 0.05, Mann Whitney U-test with Bonferroni correction). At 28 days, however, no significant differences in the density of ED1+/OX6- and ED1+/OX6+ cells were noted among the groups.
Conclusions: Under the present experimental condition, MTA induced more pronounced infiltration of macrophage/dendritic lineage cells in the subcutaneous tissue during earlier time points after implantation. These results suggest that MTA elicits inflammatory and immunogenic responses related to these cells in the connective tissue, which could result in the generation of pro-inflammatory and/or tissue-reparative bioactive substances.