Introduction: Enterococcus faecalis is commonly associated with persistent periapical infections. The physiologic state of the cells in the canal is probably closest to the starvation state. However, the biofilm formation capability of starved E. faecalis cells on human dentin and the susceptibility of the biofilm to 5.25% sodium hypochlorite remain poorly understood.
Methods: E. faecalis American Type Culture Collection (ATCC) 29212 in different growth phases were incubated on human dentin and polystyrene blocks. Scanning electron microscopy and biofilm assay were used to investigate the biofilm formation capability of these cells. The susceptibility of the biofilm to 5.25% NaClO was also determined by the plate count method.
Results: Scanning electron microscopy and biofilm assay showed that starved cells were able to form biofilm on dentin with reduced efficiency as compared with the cells in the exponential phase and stationary phase (p < 0.05). Biofilm grown on dentin harbored more cells than polystyrene (p < 0.05). Biofilms of starved cells were more resistant to 5.25% NaClO than those of stationary cells (p < 0.05), and the impact of 5.25%NaClO on them decreased as the biofilm matured.
Conclusion: E. faecalis cells in the starvation phase could develop biofilm on human dentin, which is responsive to 5.25% NaClO. It may contribute to the predominant role of E. faecalis involved in persistent periapical infections.
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