A qualitative and quantitative investigation into the effect of fluoride formulations on enamel erosion and erosion–abrasion in vitro

Abstract

Objectives To investigate the effect of a single application of highly concentrated SnF 2 and NaF solutions and a NaF/CaF 2 varnish on human enamel subjected to hydrochloric acid erosion and tooth brush abrasion. Methods Forty enamel samples were prepared from human third molars and NaF (9500 ppm, pH 8.0), SnF 2 (9500 ppm, pH 2.6) solutions; Bifluorid10 ® varnish (42,500 ppm, NaF 5%, CaF 2 5%) and deionized water (control) was applied to the enamel. Following this three, six and nine cycles of erosion [1 cycle = erosion (0.01 M HCl, pH 2.2, 2 min) + artificial saliva (1 h, pH 7.0)] and erosion–abrasion [1 cycle = erosion (0.01 M HCl, pH 2.2, 2 min) + artificial saliva (1 h, pH 7.0) + abrasion (120 linear strokes in artificial saliva from Tepe medium soft brushes 200 g loading)] were carried out. The fluoride treated enamel was analysed using Knoop microhardness, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Results For erosion alone, there was significantly less microhardness reduction in the Bifluorid10 ® group after three and six cycles of erosion ( P < 0.05), however no other groups showed statistically different hardness ( P > 0.05). The EDS analysis showed that only the Bifluorid10 ® group had any detectable fluorine following erosion and erosion–abrasion (0.1 wt.% and 0.2 wt.% fluorine respectively). The surface fluorine was found to have been removed after erosion and erosion–abrasion for all other surface treatments. Although precipitates were observed after application of the surface treatments, following erosion–abrasion, no visible surface effects from any fluoride preparation remained. Conclusions Enamel surface precipitates from application NaF, SnF 2 solutions appear to not be able to provide protection against gastric erosion and tooth brush abrasion. The NaF/CaF 2 varnish provided limited protection against erosion but the role for such varnishes in gastric erosion and tooth brush abrasion remains uncertain.