Antimicrobial Activity of Several Calcium Hydroxide Preparations in Root Canal Dentin

The purpose of this study was to evaluate the antimicrobial activity of several calcium hydroxide (Ca(OH) 2 preparations in root canal dentin infected with Enterococcus faecalis. Roots of extracted bovine incisors were prepared to standardized cylindrical test specimens of 5 mm in height; the smear layer was removed, and the specimens were incubated for 24 h at 37°C in bacteriological culture medium that contained 7.0 × 10 4 colony forming units per milliliter of E. faecalis. The specimens were mounted in individual 4-mm diameter culture wells, and the test material was applied to fill the canal lumen. There were five treatment groups: group 1, a thick mixture of Ca(OH) 2 USP (1.0 g/ml H 2O); group 2, a thin mixture of Ca(OH) 2 USP (0.1 g/ml H 2O); group 3, Pulpdent TempCanal™ paste; group 4, sterile H 2O (positive control); and group 5, 25 dentin specimens in sterile, uninoculated brain-heart infusion broth that were included as negative controls. Quantitative microbiological analysis of dentin at various depths was completed after 24 h. All groups showed a significant (p < 0.001) decrease in numbers of E. faecalis in all depths of dentin compared with the control. Groups 2 and 3 demonstrated significantly greater antimicrobial activity (73%–86% reduction) at all depths of dentin tested compared with group 1 (13%0-26%) (p < 0.05). These results suggest that Ca(OH) 2 can decrease the numbers of E. faecalis at all depths of dentinal tubules within 24 h and that thin preparations of Ca(OH) 2 may be more effective in the elimination of E. faecalis from dentinal tubules than thick preparations.