Kata Rošin-Grget

The cariostatic mechanisms of fluoride.

UNLABELLED This article discusses the possible cariostatic mechanisms of the action of fluoride. In the past, fluoride inhibition of caries was ascribed to reduced solubility of enamel due to incorporation of fluoride (F-) into the enamel minerals. The present evidence from clinical and laboratory studies suggests that the caries-preventive mode of action of fluoride is mainly topical. There is convincing evidence that fluoride has a major effect on demineralisation and remineralisation of dental hard tissue. The source of this fluoride could either be fluorapatite (formed due to the incorporation of fluoride into enamel) or calcium fluoride (CaF2)-like precipitates, which are formed on the enamel and in the plaque after application of topical fluoride. Calcium fluoride deposits are protected from rapid dissolution by a phosphate -protein coating of salivary origin. At lower pH, the coating is lost and an increased dissolution rate of calcium fluoride occurs. The CaF2, therefore, act as an efficient source of free fluoride ions during the cariogenic challenge. The current evidence indicates that fluoride has a direct and indirect effect on bacterial cells, although the in vivo implications of this are still not clear. CONCLUSION A better understanding of the mechanisms of the action of fluoride is very important for caries prevention and control. The effectiveness of fluoride as a cariostatic agent depends on the availability of free fluoride in plaque during cariogenic challenge, i.e. during acid production. Thus, a constant supply of low levels of fluoride in biofilm/saliva/dental interference is considered the most beneficial in preventing dental caries.

Antimicrobial effect of different brushing frequencies with fluoride toothpaste on Streptococcus mutans and Lactobacillus species in children with fixed orthodontic appliances

Objective To evaluate the antimicrobial effect of different frequencies of brushing with fluoride toothpaste on the levels of salivary mutans streptococci and lactobacilli in children undergoing fixed orthodontic treatment. Methods The study included 22 patients scheduled for fixed orthodontic therapy distributed between 2 groups with different hygiene regimes. All the subjects received identical braces, bands, and brackets bonded with the same material. Stimulated saliva samples were obtained before placement of the appliance and at 6, 12, and 18 weeks during the therapy. Saliva samples were cultured on selective microbial agar for the detection of microorganisms. Results Salivary mutans streptococci were significantly suppressed throughout the experimental period in the group that brushed 4 times a day as compared to the group that brushed twice a day. Salivary lactobacilli were not significantly affected by the frequency of brushing with 0.32% sodium fluoride (NaF) toothpaste. Conclusions The use of 0.32% NaF-containing toothpaste more than 3 times a day has effective antimicrobial activity on mutans streptococci but not lactobacilli in the saliva of children with fixed orthodontic appliances.

In vitro Fluoride Uptake by Enamel from Different Amine Fluoride Concentrations

The aim of this in vitro study was to examine whether the concentration of amine fluoride solution influences the uptake of fluoride by enamel after topical treatment. Four slabs were prepared from each of 31 impacted third molars and selected at random so that one slab from each tooth was present in each group. One group of slabs served as an untreated control (D). The slabs of the other three groups were shaken for 3 min in an amine fluoride solution on 3 successive days: group A (1% F), group B (0.5% F) and group C (0.25% F). The amounts of KOH-soluble fluoride produced with 1 and 0.5% amine fluoride solution did not differ significantly and were superior to 0.25% amine fluoride solution. A statistically significant increase in structurally bound fluoride was observed in groups A, B and C compared with control group D. The difference in the amounts of structurally bound fluoride was significant only between 1 and 0.25% F concentrations. These data suggest that the fluoride content in an amine fluoride solution (1%) can be decreased by half without reducing its ability to form alkali-soluble or structurally bound fluoride. The results of this study are consistent with those of previous clinical studies.

The Effect of Saliva on the Formation of KOH-Soluble Fluoride after Topical Application of Amine Fluoride Solutions of Varying Fluoride Concentration and pH

The effect of saliva on the amount of KOH-soluble fluoride formed on a sound enamelsurface after application of amine fluoride solution of varying fluoride concentrations (1, 0.5 and 0.25% F) and pH (5.3, 4.5 and 4.0) was examined in an in vitro study. The saliva pretreatment increased the amount of KOH-soluble fluoride at the highest pH value. For any given fluoride concentration, the presence of saliva did not influence the amount of KOH-soluble fluoride. These data suggest that saliva could enhance the amount of KOH-soluble fluoride if the topical fluoride preparations are not highly acid.

Anticaries Effect of Different Amine Fluoride Concentrations in Schoolchildren

A double-blind 3-year clinical trial was conducted in a nonfluoridated water community in which 354 schoolchildren aged 9-10 years were assigned randomly to three groups (A, B and C) and subjected to a treatment with 1 of 3 different concentrations of amine fluoride solution every 2 months. Clinical examinations were conducted at baseline and after 1, 2, and 3 years. For group A (positive control) receiving topical applications of amine fluoride solution (1%), the 3-year DMFT and DMFS increments were 4.0 +/- (SD) 2.7 and 8.5 +/- 5.6, respectively. For group B (0.5% F), the DMFT and DMFS increments were 4.4 +/- 3.0 and 8.4 +/- 5.7, respectively; these differences being statistically not significant. The mean caries increments in group C (0.25% F) were 5.1 +/- 2.9 for DMFT and 10.0 +/- 5.5 for DMFS. The differences in incremental caries scores between group C and groups A or B were statistically significant (p < 0.05). Thus, the amine fluoride solution, in which the fluoride content was reduced by half, provided similar caries reductions in schoolchildren as did a standard amine fluoride solution with 1.0% F.

Caries-preventive effect of two different topical fluoride concentrations with two different frequencies of application in preschool children.

The effects of standard topical amine fluoride solution (1% F) and a low-fluoride solution (0.5% F) with two different frequencies of application (5 and 10 times a year) on 2 years dental caries increment were compared in a double-blind clinical trial involving 199 kindergarten children. The results suggest that increased frequency of application of a low fluoride topical solution (10 times a year) may provide caries protection in preschool children with relatively high caries activity.