Evaluation of residual antibacterial activity of three concentrations of new root canal irrigation solution

The purpose of this in vitro study was to compare the antimicrobial substantivity of three concentrations (100%, 10%, 1%) of MTAD in bovine root dentin. One hundred and ten dentin tubes prepared from bovine incisors were infected in vitro for 14 days with Enterococcus faecalis. The specimens were divided into five groups as follows: MTAD 100%; MTAD 10%; MTAD 1%; infected dentin tubes (positive control); and sterile dentin tubes (negative control). Dentin chips were collected with round burs into tryptic soy broth (TSB). After culturing, the number of colony-forming units (CFU) was counted. In all experimental groups, CFU was minimum in the first cultures; the results obtained were significantly different from each other at any time period (P < 0.05). In the first culture, the MTAD 100% group and MTAD 1% group showed the lowest and highest number of CFU, respectively. In each group, the number of CFUs increased significantly by time-lapse (P < 0.05). In conclusion, the substantivity of MTAD100% was significantly greater than two other concentrations of MTAD.