Combined Antibacterial Activity of Cetylpyridinium Chloride in the Presence of Two Herbal Extracts Against Streptococcus mutans

Background: Dental caries is one of the most prevalent chronic human infections worldwide. It begins with bacterial adherence to the tooth surface and the formation of dental plaques. Among various microorganisms involved, mutans streptococci are the principal oral microorganisms involved in the initiation and development of dental caries. Cetylpyridinium chloride (CPC), a quaternary ammonium with a rapid bactericidal effect, is widely used as the active ingredient of antiseptic oral mouthrinses. Plants extracts are also extensively employed in oral hygiene products for their antimicrobial, anti-inflammatory, and astringent properties. The present study aimed to investigate the combined antibacterial activity of CPC in combination with two plant extracts that are extensively utilized in dental hygiene products. Methods: The aerial parts of Matricaria chamomile and hydroalcoholic extracts of Quercus infectoria galls were prepared by maceration. Dried extracts were investigated for antibacterial activity against Streptococcus mutans by determining the minimum inhibitory concentrations (MICs). A checkerboard method was applied to investigate the combined antibacterial activity of CPC in the presence of M. chamomile aerial parts and Q. infectoria gall extracts. Results: The results of this study indicated a synergistic effect between CPC and the hydroalcoholic extract of Q. infectoria galls. However, the presence of the extract of M. chamomile aerial parts had an antagonistic effect on the antibacterial activity of CPC against S. mutans. Conclusion: Accordingly, despite several beneficial properties, plant extracts should be cautiously used in the formulation of antimicrobial products due to the probability of unwanted antagonistic interactions that destroy the product’s efficacy.