Antimicrobial activity of several calcium hydroxide preparations in root canal dentin

The purpose of this study was to evaluate the antimicrobial activity of sev eral calcium hydroxide (Ca(OH)(2)) preparations in root canal dentin infect ed with Enterococcus faecalis. Roots of extracted bovine incisors were prep ared to standardized cylindrical test specimens of 5 mm in height; the smea r layer was removed, and the specimens were incubated for 24 h at 37 degree sC in bacteriological culture medium that contained 7.0 x 10(4) colony form ing units per milliliter of E. faecalis. The specimens were mounted in indi vidual 4-mm diameter culture wells, and the test material was applied to fi ll the canal lumen. There were five treatment groups: group 1, a thick mixt ure of Ca(OH)(2) USP (1.0 g/ml H2O); group 2, a thin mixture of Ca(OH)(2) U SP (0-1 g/ml H2O); group 3, Pulpdent TempCanal(TM) paste; group 4, sterile H2O (positive control); and group 5, 25 dentin specimens in sterile, uninoc ulated brain-heart infusion broth that were included as negative controls. Quantitative microbiological analysis of dentin at various depths was compl eted after 24 h. All groups showed a significant (p < 0.001) decrease in nu mbers of E. faecalis in all depths of dentin compared with the control. Gro ups 2 and 3 demonstrated significantly greater antimicrobial activity (73%- 86% reduction) at all depths of dentin tested compared with group 1 (13%-26 %) (p < 0.05). These results suggest that Ca(OH)(2) can decrease the number s of E. faecalis at all depths of dentinal tubules within 24 h and that thi n preparations of Ca(OH)(2) may be more effective in the elimination of E. faecalis from dentinal tubules than thick preparations.