Cytocompatibility and antibacterial activity of the ethanolic leaf extract of Rhodomyrtus tomentosa on Enterococcus faecalis biofilm.

PURPOSE: This study aimed to investigate the antibacterial activities of the ethanolic leaf extract of Rhodomyrtus tomentosa against Enterococcus faecalis (E. faecalis) and its cytocompatibility to human periodontal ligament (hPDL) cells. METHODS: The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the ethanolic extract of Rhodomyrtus tomentosa leaf (RTE) against E. faecalis were determined using the broth microdilution method. Biofilm inhibition was assessed using the crystal violet assay. Ultrastructural changes were observed via transmission electron microscopy (TEM), whereas biofilm and dentin surface change of root specimens were examined using scanning electron microscopy (SEM). Cytotoxicity was evaluated on hPDL cells using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. RESULTS: RTE exhibited potent antibacterial activity with MIC and MBC of 1 and 32 µg/mL, respectively. RTE significantly inhibited biofilm formation in a concentration-dependent manner and outperformed sodium hypochlorite (NaOCl) at sub-MIC levels. TEM revealed morphological disruption of E. faecalis cells following RTE treatment. SEM confirmed effective bacterial reduction without causing erosion of radicular dentin. RTE at sub-MICs demonstrated relatively low cytotoxicity compared with NaOCl. CONCLUSION: RTE exhibited strong antibacterial and antibiofilm properties while preserving dentin structure and demonstrating cytocompatibility.