Effect of Rhus coriaria L. water extract on five common oral bacteria and bacterial biofilm formation on orthodontic wire

Background and Objectives: Recently, use of herbal medicine and plant extracts as a substitute for commercially available chemical drugs for control of infectious diseases such as dental caries and periodontal disease has become increasingly popular. The present study was aimed to evaluate the effect of Rhus coriaria L. water extract on five common oral bacteria and bacterial biofilm formation on orthodontic wire. Materials and Methods: For primary assessment of the antibacterial properties of Rhus coriaria L. water extract, the well-plate method in BHIA (Brain Heart Infusion Agar, Merck, Germany) medium was used. Using macrodilution method, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the extract against each microorganism were determined. The effect of Rhus coriaria L. on bacterial biofilm formation on orthodontic wire was assessed using viable cell count in biofilm medium (BM) containing 3% sucrose. In the final phase, after fixation of samples in alcohol and glutaraldehyde, samples were prepared for SEM (Scanning Electron Microscopy) analysis. Results: The diameter of the zone of growth inhibition was proportionate to the tested concentrations of the extract. The lowest MIC (0.390 mg/ml) and MBC (1.5 mg/ml ) of the Rhus coriaria L. were found to be against Streptococcus sobrinus ATCC 27607. Rhus coriaria L. water extract decreased bacterial biofilm formation on orthodontic wire at MIC and 1/8 of MIC by S. sanguinis ATCC 10556, S. sobrinus ATCC 27607, S. salivarius ATCC 9222, S. mutans ATCC 35608 and E. faecalis CIP 55142 by24.2%-43%, 68.5%-91.6%, 10.6%-79.1%, 22.2%-86.1% and 40.6%-76.4%, respectively. Conclusion: Based on the results, Rhus coriaria L. water extract had significant antibacterial properties against five common oral bacteria and was able to inhibit bacterial biofilm formation on orthodontic wire. Further investigations are recommended for widespread clinical use of this extract.