In Vitro Comparison of Anti-Bacterial Effect of Shirazian and T. deanesis Essential oil and their Effective Ingredients Thymol and Carvacrol on S. mutans Strain

Use of chemical mouthwashes to control caries can cause side effects, and disturb the balance of the buccal cavity. As a result, the use of natural materials such as plants has been recently considered. Considering the antibacterial features of Thymol and Carvacrol as the key ingredients of Thymus vulgaris and T. deanesis, respectively, this study aimed toward a comparative assessment of the antibacterial effects of T. vulgaris and T. deanesis and their effective ingredients Thymol and Carvacrol on S. mutans strain. This study was experimental. S. mutans strain was received from Iranian Institute of Pasteur, Thymol and Carvacrol were provided by Sigma- Aldrich and T.vulgaris and T.deanesis essential oils were obtained from the leaves of these two plants by the distillation method using Clevenger apparatus. The antibacterial effect was assessed by determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and zone of inhibition (ZOI) by macrodilution with disc diffusion at concentrations 15.3-100% of each four materials at 24, 48, and 72 h.Data were analyzed using SPSS 22 software and ANOVA (α=0.05). The MIC and MBC of T.vulgaris and T. deanesis essential oils and that of Thymol and Carvacrol on S. mutans strain were 6.25-6.25%, 6.25-3.125%, 3.125-3.125%, and 3.125-3.125%. The results revealed that ZOI increased significantly with the increasing concentrations (P <0.001). In T. deanesis, with a time increase from 24 to 72h, ZOI indicated a significant difference (P =0.043); however, in the other three substances, ZOI was not statistically significant over time (Carvacrol, P=0.254; Thymol, P =0.237, T. vulgaris, P =0.062). Moreover, the results revealed that ZOI of Thymol and Carvacrol not statistically significant (P =0.971), and ZOI of T. vulgaris and T. deanesis essential oil also were not significantly different (P =0.984); however, ZOI of Thymol and Carvacrol was higher in comparison to T.vulgaris and T.deanesis (P