Correlation of Cetylpyridinium Chloride Availability and Antimicrobial Efficacy in Mouthwash

Objectives: Cetylpyridinium chloride (CPC) is a well-known antimicrobial agent in oral care products, especially in mouthwash, and was classified by the US FDA as safe and efficacious for the treatment of plaque-induced gingivitis. However, positively charged CPC molecule can be deactivated by certain anions which may impact antimicrobial activity. The objective of this investigation was to study the correlation of CPC's availability and activity in mouthwash via two different in vitro methods. Methods: CPC availability was accessed by an in-vitro Disk Retention Assay (DRA) recommended by the FDA. This method measures the amount of chemically available CPC in a mouthwash formal. Briefly, CPC binds to a cellulose disk during filtration. The bound CPC reacts with an acid fuschin dye. CPC-dye complex is measured colormetrically to determine the amount of CPC. The higher the absorbance, the greater the amount of CPC chemically is available in a mouthwash. Growth Inhibition Test (GIT) evaluated the antimicrobial efficacy of a mouthwash. Actinomyces naeslundii and Streptococcos mutans were grown in culture media with CPC mouthwash for 24hr. Antimicrobial effect was determined spectrophometrically at O.D. 630 nm. Results: The results showed a positive correlation of DRA and GIT in a mouthwash. High DRA levels showed higher availability of CPC, which also showed higher growth inhibition in GIT. Conclusions: This study suggests that combined use of DRA and GIT would provide a useful tool to evaluate CPC mouthwash. The positive correlation of DRA and GIT can help improve formula efficacy and aid to develop efficacious oral care product.