Comparative Evaluation of Antimicrobial Activity of Licorice, Green Tea, Their Combined Extracts, and Sodium Fluoride Mouthwashes against Streptococcus mutans: An In Vitro Study

Abstract

Background: The current lifestyle has made children more susceptible to carious lesions all around the world. One of the major contributing microorganisms is Streptococcus mutans, which causes initiation of enamel caries and is a major etiological pathogen. For the prevention of caries and therapeutic purposes, mouthwashes or mouth rinses are promoted a lot. The first mentioned mouth rinse was seen around 2700 BC in Chinese medicine. Among antimicrobial agents, chlorhexidine is considered gold standard but it has side effects such as extrinsic stain formation and bitter taste. Glycyrrhiza (licorice), a herb, which has medicinal value and was used in ancient times as a remedy for a great diversity of ailments and sweetener. Roots of Glycyrrhiza contain a high concentration of saponin and glycyrrhizin, which are supposed to be sweetening agents. Green tea, which is very rich in fluoride, with its catechin content attribute to its benefits. Polyphenols and various flavonoids such as catechin, catechin gallate, and catechin proanthocyanidin are its main constituents. Hence, the aim of the study was to evaluate and compare the antimicrobial activity of ethanolic licorice extract with and without green tea extract and sodium fluoride mouthwash against S. mutans. Materials and methods: In the first part of the study, various concentrations of ethanolic licorice and green tea extract were prepared in the laboratory of Pharmacy College. Further, mouthwash formulations were done using the same extracts. A combination of green tea and licorice mouthwash was made too. It was then subjected to microbiological assay to determine its zone of inhibition using agar disk diffusion test and minimum inhibitory concentration (MIC) was measured against S. mutans. Sodium fluoride (Kidodent) mouthwash was used as a positive control. Results: Significant difference was seen with the following groups: Kidodent and green tea, Kidodent and licorice; green tea and green tea + licorice, and licorice and green tea + licorice. No significant difference was seen for the following group comparison: Kidodent and green tea + licorice, and green tea and licorice. Also, out of all the mouthwashes, the maximum zone of inhibition in millimeters was seen for 30.75 ± 1.16 mm for green tea mouthwash, 29.75 ± 1.03 mm for licorice mouthwash, and 27.875 ± 1.12 mm for the combination. Conclusion: Early establishment of cariogenic microbes such as S. mutans in children less than 4 years is an indicator of higher caries susceptibility. Also, it requires parental overseeing during the usage of commercial fluoride mouthwashes. These are known to cause various toxic effects both chronic and acute especially in kids smaller than 6 years of age. Significant differences were seen with the following groups: Kidodent and green tea mouthwash, Kidodent and licorice mouthwash, green tea and green tea + licorice mouthwash, and licorice and green tea + licorice mouthwash. Thus, investing the knowledge and sources toward herbal alternative will help for a safer future and brighter smiles.