Calcium Hydroxide Treatment Does Not Alter the Susceptibility of Enterococcus faecalis Biofilms to Sodium Hypochlorite

OBJECTIVE: To investigate the influence of calcium hydroxide (Ca(OH)(2)) on susceptibility to disinfection with sodium hypochlorite (NaOCl) of biofilm bacteria. METHODS: Monospecies biofilms of eight Enterococcus faecalis strains were subjected to a 2-h challenge with Ca(OH)(2). After a recovery phase, the biofilms were treated with a concentration of NaOCl that was lower than the minimum inhibitory concentration. In a metabolic assay, the efficacy of NaOCl disinfection in Ca(OH)(2)-challenged biofilms and unchallenged biofilms was evaluated. The data were analyzed with Mann-Whitney U and Kruskall- Wallis tests. A P value of less than 0.05 was considered statistically significant. RESULTS: There were marginal differences in susceptibility to NaOCl among the E. faecalis strains. After the Ca(OH)(2) challenge, seven strains remained equally susceptible to NaOCl disinfection whereas one strain became more resistant to NaOCl (P=0.03). CONCLUSION: After a Ca(OH)(2) challenge, in general E. faecalis remained equally susceptible to disinfection with NaOCl.