In vitro Susceptibility of Streptococcus oralis to Different Mouthwashes.

Aim: The use of mouthwashes represents, in many cases, the first option for the chemical control of dental biofilm. To evaluate in vitro susceptibility of Streptococcus oralis (ATCC 10557) to commercial mouthwashes available on the Brazilian market. Methods: Seven mouthwashes were evaluated: Equate®, Colgate Plax Overnight®, Sanifill®, Cepacol Cool Citrus® and Oral-B® (cetylpyridinium chloride), Listerine® (Thymol) and Peroxyl® (hydrogen peroxide). A 0.12% chlorhexidine digluconate oral rinse (Periogard®) served as a positive control. The antibacterial activity of the mouthwashes in 7 dilutions (1:0 to 1:32) was evaluated by determining the maximum inhibitory dilution (MID) in Muller Hinton agar supplemented with 5% blood. Fifty microliters of each ready-to-use solution and their dilutions were poured into wells perforated in the solid culture medium and the dishes were incubated in bacteriological incubators at 37°C for 24 hours. The analysis of MID data was based on the measurement of the zones of bacterial growth inhibition (in mm) formed around the wells (only inhibition zones with a diameter ≥10 mm were considered). Results: The following MIDs were obtained: 1:2 for Equate® and Oral-B®, 1:1 for Sanifill®, and 1:4 for Plax®, Cepacol® and Periogard®. Peroxyl® and Listerine® did not show antibacterial activity against S. oralis. In conclusion, S. oralis presented susceptibility to the mouthwashes evaluated in this study, except for Peroxyl® and Listerine®. Conclusion: These results suggest that cetylpyridinium chloride and chlorhexidine gluconate, which are the most important active components of the tested brands of mouthwashes, are important agents in the chemical control of dental biofilm. [ABSTRACT FROM AUTHOR]