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 be- came 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.