Sodium fluoride effect on erosion–abrasion under hyposalivatory simulating conditions

Abstract

ObjectivesTo investigate the effect of fluoride (0, 275 and 1250ppm F; NaF) in combination with normal and low salivary flow rates on enamel surface loss and fluoride uptake using an erosion–remineralization–abrasion cycling model. DesignEnamel specimens were randomly assigned to 6 experimental groups (n=8). Specimens were individually placed in custom made devices, creating a sealed chamber on the enamel surface, connected to a peristaltic pump. Citric acid was injected into the chamber for 2min followed by artificial saliva at 0.5 (normal flow) or 0.05 (low flow) ml/min, for 60min. This cycle was repeated 4×/day, for 5 days. Toothbrushing with abrasive suspensions containing fluoride was performed for 2min (15s of actual brushing) 2×/day. Surface loss was measured by optical profilometry. KOH-soluble fluoride and enamel fluoride uptake were determined after the cycling phase. Data were analysed by two-way ANOVA. ResultsNo significant interactions between fluoride concentration and salivary flow were observed for any tested variable. Low caused more surface loss than normal flow rate (p<0.01). At both flow rates, surface loss for 0 was higher than for 275, which did not differ from 1250ppm F. KOH-soluble and structurally-bound enamel fluoride uptake were significantly different between fluoride concentrations with 1250>275>0ppm F (p<0.01). ConclusionsSodium fluoride reduced enamel erosion/abrasion, although no additional protection was provided by the higher concentration. Higher erosion progression was observed in low salivary flow rates. Fluoride was not able to compensate for the differences in surface loss between flow rates.