M Hammad A-K Sallal H Darmani Authors’ affiliations: M. Hammad, Department of Preventive Dentistry, Faculty of Dentistry, Jordan University of Science and Technology, Irbid, Jordan A.-K. Sallal, H. Darmani, Department of Applied Biological Sciences, Faculty of Science, Jordan University of Science and Technology, Irbid, Jordan Correspondence to: H. Darmani Department of Applied Biological Sciences Faculty of Science Jordan University of Science and Techno- logy, Irbid Jordan Tel.: +962 795 978834 Fax: +962 272 01071 E-mail: darmani@just.edu.jo Dates: Accepted 2 April 2007 To cite this article: Int J Dent Hygiene 5, 2007; 232–235 Hammad M, Sallal A-K, Darmani H. Inhibition of Streptococcus mutans adhesion to buccal epithelial cells by an aqueous extract of Thymus vulgaris. Ó 2007 The Authors. Journal compilation Ó 2007 Blackwell Munksgaard Inhibition of Streptococcus mutans adhesion to buccal epithelial cells by an aqueous extract of Thymus vulgaris Abstract: Objectives: The aim of this study was to investigate the effect of an extract of Thymus vulgaris (thyme) on the growth of Streptococcus mutans (S. mutans) and the adhesion of this bacterium to human buccal epithelial cells. Methods: Different concentrations of an aqueous extract of thyme were prepared and the effects investigated on growth of S. mutans. Furthermore, the effect of these extracts on adhesion of S. mutans to buccal epithelial cells was also investigated and compared with the effects of chlorhexidine digluconate. Results: The data revealed that exposure of S. mutans to thyme extract showed a time and concentration-dependent decrease in bacterial viability. The greatest effect was observed when S. mutans had been exposed to 20% thyme extract for a period of 48 h which resulted in 96% inhibition of bacterial growth. Furthermore, the adhesion of S. mutans to buccal epithelial cells was also reduced when either buccal epithelial cells or S. mutans had been pre-incubated with different concentrations of aqueous thyme extracts (83–98% and 75–89% inhibition respectively). There was also greater reduction in the adherence of bacterial cells to buccal epithelial cells after mouth rinsing with 20% aqueous thyme extract compared to rinsing with chlorhexidine digluconate (45% and 89% inhibition of bacterial adhesion respectively). Conclusion: The diminished adherence of S. mutans to buccal epithelial cells after exposure to various concentrations of aqueous thyme extract as well as the antimicrobial properties of this plant may have clinical relevance. Key words: adhesion; chlorhexidine digluconate; Streptococcus mutans; thymus vulgaris ORIGINAL ARTICLE 232 Int J Dent Hygiene 5, 2007; 232–235