Evaluation of the antibacterial effects of three natural formulated mouthwashes against Streptococcus mutans: An in vitro study

Streptococcus mutans (S. mutans)is a well-known bacterial cause of dental caries. The aim of this study was to develop an herbal mouthwash with anti-biofilm activity and compare it with a commercial preparation containing 2% chlorhexidine. The main components of the mouthwashes included Punica granatum, pomegranate rind, Eugenia caryophyllata, Rhus coriaria L., etc. (No. 1); Pistacia lentiscus L., Punica granatum, Areca catechu L., etc. (No. 2); Cyperus articulatus, Terminalia chebula Retzius, Cinnamomum zeylanicum, Elettaria cardamomum, Zingiber zerumbet, Punica granatum, etc. (No. 3). Plants were weighed and soaked into sterile distilled water. Filtration and sterilization were performed using Whatman and Millipore filters, respectively. The antibacterial susceptibility assay was performed by an agar well diffusion method according to Clinical and Laboratory Standards Institute (CLSI). Anti-biofilm activity of mouthwashes and chlorhexidine was evaluated on polystyrene microtiter plates by a broth dilution method. Finally, a comparative analysis of the results was done by Tukey and analysis of variance (ANOVA) tests. No positive effect of mouthwash No. 1 was observed in the agar well diffusion method. This mouthwash showed an effect on biofilm formation only at 50% concentration. In agreement with well diffusion, the effect of mouthwash No. 2 was moderate and similar to 2% chlorhexidine. The mouthwash No.3 showed an excellent effect (even at 3.125%) against S. mutans. Overall, mouthwash No.3 appears to be suitable as an herbal anti-biofilm solution. Further studies are necessary to identify the active ingredients of the plants.