Introduction: This in vitro study aimed to compare the antimicrobial effect of lavandula -0fficinalis extract, with sodium hypochlorite (NaOCL) and chlorhexidine gluconate (CHX), as root canal irrigants, on Enterococcus faecalis (EF).

Materials &Methods: Seventy five extracted single-rooted premolars were selected. Root canals were prepared using rotary ProTaper system and were infected with the culture of E. faecalis. Specimens were randomly divided into five groups (n = 15), Group 1, 2: lavandula extracts (0.26 and 0.52 mg/mL), Group 3: 2.5%NaOCL, Group 4: 2%CHX, Group 5: Normal Saline. Irrigation was performed for each group for 5, 10 and 15 min. The viable bacteria obtained by collecting the canal dentin chips. Data analysis was performed with Kruskal-Wallis and Mann-Whitney u tests.

Results: The mean number of viable bacteria was significantly reduced after 5 min exposure to lavandula solutions (p<0.05). A significant difference also existed between different times in the NaOCL group, being significant between 5 and 15 min (p<0.05), but there was no significant difference between different times in the CHX group. Comparison of the mean number of viable bacteria between different groups at different exposure times revealed that the difference between lavandula and NaOCL solutions with CHX was significant at 5 and 10 min (p<0.05), however, no statistically significant difference was observed between lavandula solutions and NaOCL.

Conclusion: lavandula extract was effective in killing of EF.  Further studies are necessary to fully understand its other properties such as tissue solubility, removal of smear layer and impact on dentin structure.