Efficacy of chlorhexidine solution with fluoride varnishing in preventing enamel softening by Streptococcus mutans in an artificial mouth

For study of the enamel-protective effect of chlorhexidine-fluoride applications, the labial surfaces of pieces of bovine incisors were treated with 0.2% chlorhexidine gluconate solution, with Duraphat fluoride varnish, or with both of the above agents, while one group was treated with distilled water and one was left as an untreated control. Furthermore, a placebo varnish was used in the chlorhexidine- and distilled-water-treated groups; all the varnishes were removed after 24 h. The enamel slabs were mounted pairwise in an artificial mouth to form approximal contacts. The teeth were continuously rinsed with a common pool of artificial saliva to which was added 3% sucrose, and which was infected on the first day with Streptococcus mutans , "Ingbritt". The saliva was renewed daily and the incubation at 37°C lasted for 10 days. The appreciable softening found in the distilled-water- and placebo-varnish-treated group tended to be prevented by the chlorhexidine and even more by the fluoride treatment, while the chlorhexidine-fluoride treatment prevented enamel softening completely. The saliva, infected only on the first day, and renewed daily, tended to become more acidified toward the end of the experimental period, obviously because the fermenting organisms had infected the surfaces of the model and formed plaque-like coatings on the enamel.