In vitro Evaluation of Acidified Toothpastes with Low Fluoride Content

Abstract

Fluoride toothpastes are a risk factor for the development of dental fluorosis. Products with low fluoride content offer a higher security, but their effectiveness must be proven. The aim of this in vitro study was to compare two acidified toothpastes with low fluoride concentration (412 and 550 µg F/g) with neutral toothpastes. Bovine enamel blocks were selected by surface microhardness (SMH) and randomized to twelve groups of 13, according to the fluoride concentration in toothpaste (placebo, 275, 412, 550 or 1,100 µg F/g) and pH (7.0 or 5.5). Two commercially available toothpastes were also studied: a 1,100-µg F/g, pH 7.0 paste (positive control) and a children’s paste (500 µg F/g, pH 7.0). The blocks were subjected to pH cycling for 7 days. The toothpaste treatment was done twice daily. Surface and cross-sectional microhardnesses were assessed to calculate the percentage change of SMH (%SMH) and the mineral loss (ΔZ). The amount of fluoride, calcium and phosphorus in the solutions after the pH cycling was also analyzed. Compared to neutral toothpastes, the acidified toothpastes reduced the %SMH in all F concentrations. Higher F and lower Ca and P concentrations were found in solutions for the acidified toothpastes. Regarding ΔZ, only the positive control, 1,100-µg F/g (acidified and neutral) groups were not statistically different. The acidified toothpastes showed a dose-response relationship with all variables. For the low-fluoride toothpastes evaluated, only the 550-µg F/g acidified paste had the same anticariogenic action as the 1,100-µg F/g neutral paste.

Impact of Different Toothpastes on the Prevention of Erosion

“…Zendium slurry (pH 5.21) and the Meridol slurry (pH 4.74) were slightly acidic and would be expected to provide higher F intensity than the neutral ones. Brighenti et al [2006] found a smaller decrease in percent SMH in a pH cycling model for 7 days when using acidified toothpastes compared to neutral ones. In our study no overall better performance could be shown of the slightly acidic toothpaste slurries compared to the neutral ones.…”

Effect of Slow-Release Fluoride Devices and Casein Phosphopeptide/Amorphous Calcium Phosphate Nanocomplexes on Enamel Remineralization in vitro

“…The use of bovine enamel has been verified in a number of in vitro studies to evaluate the effect of anticariogenic agents on enhancing enamel remineralization and inhibiting enamel demineralization [Brighenti et al, 2006;Lennon et al, 2006;ten Cate et al, 2006]. There are some reported variations in the characteristics of bovine enamel in comparison to human enamel; such as it provides a less variable response to both the cariogenic challenge and the anticariogenic agents, the composition of bovine enamel is less variable than human enamel [Mellberg, 1992].…”

Comparison of Methods for Evaluating Mineral Loss: Hardness versus Synchrotron Microcomputed Tomography

“…Among the in vitro models used worldwide, pH cycling simulates caries development under controlled condi- tions [White, 1995] and gives information on surface and subsurface enamel in caries dynamics [ten Cate and Mundorff-Shrestha, 1995]. The pH cycling model of Vieira et al [2005] for bovine teeth, based on the studies of ten Cate and Duijsters [1982] and Featherstone et al [1986], is a sensitive methodology for verifying the fluoride dentifrice dose-response relationship [Brighenti et al, 2006;Alves et al, 2007;Takeshita et al, 2009]. As a short-term pH cycling model, it provides a lower demineralization and a surface layer and lesion depth considered 'small'.…”