OBJECTIVETo study the effect of calcium hydroxide solutions at different pH values on the cell-surface hydrophobicity of starved Enterococcus faecalis.

METHODSE. faecalis in starvation were harvested and incubated in freshly prepared calcium hydroxide solutions at the pH values ranging from 7.3 to 10.3 for 15 min or 60 min. The cell-surface hydrophobicity of the starved E. faecalis was evaluated by measuring microbial adhesion to hydrocarbons (MATH). Scanning electron microscopy was used to investigate the adhesion capability of starved E. faecalis cells incubated on human dentin at different pH levels.

RESULTSFor the same duration of treatment, increased pH value of calcium hydroxide solution significantly enhanced the cell-surface hydrophobicity of starved E. faecalis (P<0.01). At the same pH value, the cell-surface hydrophobicity of the bacterium increased significantly with time (P<0.05, 15 min vs 60 min). Scanning electron microscopy revealed a significantly increased adhesion of the starved cells on human dentin as the pH value and incubation time increased.

CONCLUSIONCalcium hydroxide solutions promote the adhesion of starved E. faecalis by modifying its cell-surface hydrophobicity.