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

Abstract

The aim of the study was to determine the effective pH of calcium hydroxide Ca(OH) 2 against Enterococcus faecalis, the most fre-quently isolated bacterial species in endodon-tic 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 o C. The paper points were then transferred to neu-tralizing 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 incu-bated anaerobically at 37 o C for 24 h. The num-ber 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.