Effect of Timing of Fluoride Treatment on Enamel De- and Remineralization in vitro: A pH-Cycling Study

Abstract

An in vitro pH-cycling experiment was completed to determine the effect of the timing of fluoride toothpaste application on de- and remineralization. Both initially sound enamel and artificially produced enamel lesions were subjected to a pH-cycling scheme. The lesions were either formed in an undersaturated calcium-phosphate-fluoride-acetate system (CPF lesions) or in a MHDP-containing lactate buffer (MHDP lesions). The two systems produced subsurface demineralization which differed in porosity, depth and surface layer characteristics. Changes in the enamel mineral content were assessed either by microhardness evaluation of the specimens at the end of the cycling period or by calcium uptake and loss during the pH-cycling period. The results show that a fluoride dentifrice treatment is very effective in inhibiting lesion formation in initially sound enamel as well as in inhibiting lesion progression. The latter was found to be primarily due to a significant decrease in mineral loss during the demineralization cycles. This observation was made irrespective of the timing of the fluoride dentifrice treatment, which was either given before or after the demineralization challenge. For the CPF lesions this inhibition was between 40 and 50%, while the corresponding value for the MDHP lesions was 15–30%. Differences between the two lesion types were also found in the dentifrice effect on lesion remineralization. In the case of the CPF lesions a small inhibition of mineral deposition was observed, while in MHDP lesions the fluoride treatment enhanced the remineralization. These observed differences are explained in terms of the differences in characteristics between these two types of lesions.

Timing of fluoride toothpaste use and enamel-dentin demineralization

“…The use of SH loss to evaluate enamel-dentin demineralization is supported by the available literature. 8,20 Although our results contradict those found by ten Cate et al, 1 these authors used an in vitro design, which may account for the observed differences compared to our in situ study.…”

“…Although F toothpaste is able to provide F ions to the oral cavity to interfere with both phenomena, 4,5 its effect when used before or after demineralizing challenges has only been studied in vitro. 1 In this in vitro study, 1 no difference was observed between F toothpaste used to inhibit the demineralization process or to enhance the mineral repair that occurs during the subsequent remineralization. However, the effect of the timing of brushing with F toothpaste has not been studied under conditions that simulate clinical F use, and the effect of this timing on root dentin demineralization is completely unknown.…”

“…1,2,3 However, the extent to which each of these effects influences caries development is unknown, because they are difficult to isolate. Although F toothpaste is able to provide F ions to the oral cavity to interfere with both phenomena, 4,5 its effect when used before or after demineralizing challenges has only been studied in vitro.…”

Effect of Fluoride Concentration on Remineralization of Carious Enamel an in vitro pH-Cycling Study

“…Sections in groups B, C, D, E, F and G were immersed for 5 min every day in neutral sodium fluoride solutions containing 1, 250, 500, 1,000, 1,750 and 2,500 ppm fluoride, respectively. In this study, treatment with the fluoride solution was always carried out immediately after the demineralizing cycle although it has been shown [ten Cate et al, 1988] that inhibition of lesion progression will be observed irre spective of the timing of the fluoride therapy. The demineralizing and artificial saliva solutions were regularly analysed for fluoride; the levels were always found to be below 0.03 ppm.…”

High Resolution Fluoride Profiles of Artificial in vitro Lesions Treated with Fluoride Dentifrices and Mouthrinses during pH Cycling Conditions

“…Sev eral different versions of the pH-cycling technique have been described [ten Cate and Duijsters, 1982;Featherstone et al, 1986Featherstone et al, , 1988Gcrrard and Winter, 1986;White, 1987;Damato et al, 1988;ten Cate et al. 1988;White, 1988].…”