Evaluation of different pH levels of calcium hydroxide on Enterococcus faecalis: an in vitro study

摘要

The aim of the study was to determine the effective pH of calcium hydroxide Ca(OH)2 against Enterococcus faecalis , the most frequently isolated bacterial species in endodontic failure. Solutions of Ca(OH)2 with different pH values of 9, 11 and 12.5 were prepared by dissolving 1 mg of Ca(OH)2 in distilled water. The test solutions were grouped as follows: Group I, vials containing phosphate buffered saline pH of 7.2 as control; Group II, aqueous calcium hydroxide with pH of 9; Group III, aqueous calcium hydroxide with pH of 11; Group IV, aqueous calcium hydroxide of pH 12.5.Forty sterile paper points were transferred to Trypticase Soy Agar broth containing Enterococcus faecalis for a period of 10 min, then transferred to vials containing 1 mL of the test solutions and incubated for 1 h at 37°C. The paper points were then transferred to neutralizing broth with glass beads to resuspend the microorganisms. Ten-fold serial dilutions were performed using aliquots of 250 μL from the broth and the same amount was plated onto blood agar plates. The plates were incubated anaerobically at 37oC for 24 h. The number of colony forming units for each dilution was counted using the colony counter. The inhibitory effects of different pH groups on the bacteria were as follows: Group IV > Group III > Group II > Group I in an ascending order. This study revealed that Ca(OH)2 at a pH 12.5 was effective in complete elimination of Enterococcus faecalis.