Effect of Topical Acidulated Phosphate Fluoride on Percentage of Streptococcus mutans and Streptococcus sanguis in Plaque

Abstract

The percentage of Streptococcus mutans and Streptococcus sanguis in pooled occlusal plaque and in pooled approximal plaque following 8–10 daily applications of either an acidulated phosphate fluoride (APF) gel or a placebo gel was determined. S. mutans averaged about 9% of the colony forming units (CFU) in the occlusal plaque and 1% of the CFU in the approximal plaque prior to treatment. S. sanguis accounted for about 5% of the approximal isolates and 8% of the occlusal isolates prior to treatment. The APF treatment caused a persistent 45–75% reduction in the percentage of S. mutans in the occlusal samples but did not have an effect on the percentage of S. mutans in the approximal plaque. Great individual variability in the percentages of S. mutans prevented the demonstration of significant differences between the APF and placebo group when parametric statistical tests were employed. When ranking procedures were used, i.e. Kruskal Wallis, Willcoxon tests, the APF was found to have a specific antimicrobial effect against S. mutans in the occlusal plaque, but not in the approximal plaque. This effect was still apparent 12 weeks after the last treatment. There was no effect of the APF on the percentages of S. sanguis in either sample, except at one week after treatment, where the approximal samples showed a significant increase. The plaque and gingivitis scores in the APF group were significantly less than in the placebo group.

Tight-adherence genes of Actinobacillus actinomycetemcomitans are required for virulence in a rat model

“…Sampling of specific sites may allow for more consistent and effective recovery of the colonizing A. actinomycetemcomitans, because viable counts will not be diluted out by total mouth sampling. This sampling problem has previously been encountered during enumerations of other oral pathogens (55). Additionally, in future studies, it will be interesting to examine other organs, such as the heart and brain, for colonization by A. actinomycetemcomitans.…”

pH-dependent bactericidal effects of acidulated fluoride gels on preformed plaque aggregates of Streptococcus mutans 6715

“…In this study, it is noteworthy that daily fluoride applications exhibited marked cariostatic effects, apparently without being lethal to the cariogenic flora. Studies by Loesche et al (16,17) have shown that daily applications of APF gels (12,300 ,ug of fluoride per ml at pH 3.2) significantly reduced proportions of S. mutans after 6 and 12 weeks posttreatment compared with pretreatment levels. Although it was speculated that a bactericidal effect might be responsible for the observed reductions (15), other mechanisms of suppression besides bactericidal action might be involved (6).…”

“…The exact mechanism(s) responsible for this inhibition, however, remains unclear. Several studies have reported reductions in proportions of cariogenic bacteria such as Streptococcus mutans for various intervals after topical fluoride applications, suggesting that fluoride, when present in these high concentrations, might exert marked inhibitory and even bactericidal effects on these bacteria (2,16,17, 26).Attempts have been made to examine the antibacterial properties of fluoride on cariogenic bacteria with various in vitro assays. For example, broth dilution (2,4,8,18) and pellet culture (19) assays clearly indicate that fluoride is capable of exerting both inhibitory and bactericidal effects on strains of S. mutans, depending upon the concentrations of the organisms and fluoride, duration of exposure, and pH of the medium, among other factors.…”

“…The exact mechanism(s) responsible for this inhibition, however, remains unclear. Several studies have reported reductions in proportions of cariogenic bacteria such as Streptococcus mutans for various intervals after topical fluoride applications, suggesting that fluoride, when present in these high concentrations, might exert marked inhibitory and even bactericidal effects on these bacteria (2,16,17, 26).…”

“…Because S. mutans has been implicated as a major etiological agent in dental caries in humans (9) and several studies have suggested that topical fluoride applications exert their anticaries effect via their antimicrobial properties (3,(15)(16)(17), we used the PPA assay to examine the bactericidal properties of several commercially available acidulated phosphate fluoride (APF) preparations against S. mutans. When the commercial preparations were found to be incapable of exerting lethal effects on aggregates of S. mutans, we prepared NaF gels in which we manipulated both the fluoride concentration and pH, since acidification enhances the bactericidal properties of fluoride (4,19).…”