Effects of chlorhexidine, listerine and fluoride listerine mouthrinses on four putative root-caries pathogens in the biofilm.

OBJECTIVE: To investigate the effects of chlorhexidine (CHX), Listerine and Fluoride Listerine on putative root-caries pathogens in the biofilm in the artificial mouth model.
METHODS: A total of 24 human dentine discs were prepared. A biofilm composed of Streptococcus mutans, Streptococcus sobrinus, Lactobacillus rhamnosus and Actinomyces naeslundii was cultured on the surfaces of human dentine discs in an artificial-mouth model. Sucrose was supplied by computer-controlled release on a daily basis to simulate the real-life situation. Three treatment reagents, CHX, Listerine and Fluoride Listerine, were supplied at a flow rate of 15 ml/h for 6 min twice a day. The dentine discs with biofilm were removed from the artificial mouth after being cultured for 1, 2, 3, 4, 5 and 6 days. The bacteria in the biofilm were analysed by plating on BHIS agar and the colony-forming units of each species were counted.
RESULTS: The total number of bacteria in the CHX group was significantly lower than in the other three groups (including control). There was no decline in the number of bacteria in the Listerine group. S. mutans was reduced significantly in the CHX group compared with the control group. The number and proportion of A. naeslundii in the CHX group were significantly lower than in the other three groups. The proportion of L. rhamnosus in the CHX group was significantly higher than in the other three groups.
CONCLUSION: CHX has the most significant effect on inhibition of the putative root-caries bacteria, with the exception of L. rhamnosus. Both Listerine and a combination of fluoride and Listerine could not effectively reduce the numbers of bacteria in the biofilm. The effects of CHX, Listerine and Fluoride Listerine on root caries prevention need further investigation.