Randomised study of the effects of fluoride and time on in situ remineralisation of acid-softened enamel

M Nehme,A. T. Hara,D. T. Zero,C. R. Parkinson

doi:10.1007/s00784-019-02900-5

Abstract

ObjectivesThis single-centre, randomised, crossover study used a short-term in situ dental erosion remineralisation model to explore the remineralisation of acid-softened enamel in the 4-h period immediately following brushing with an anti-erosion, dentin hypersensitivity test dentifrice containing 1150 ppm fluoride (as sodium fluoride [NaF]) or a placebo dentifrice with no fluoride.Materials and methodsFifty participants wearing a palatal appliance holding surface-softened bovine enamel specimens brushed their natural teeth with their assigned dentifrice. Specimens were removed at 5-, 10-, 15-, 30-, 60-, 120- and 240-min post brushing. Enamel remineralisation effect was evaluated at each timepoint by percent surface microhardness recovery (%SMHR) and enamel fluoride uptake (EFU). After a second in vitro erosive challenge, the percent relative erosion resistance (%RER) was calculated.ResultsStatistically significant differences in %SMHR were observed for the test dentifrice compared with the placebo dentifrice from the 60-min timepoint onwards (all p < 0.02; mean difference of 8.66 [95% CI 3.46, 13.87] at 60 min). At each specimen removal time, %RER and EFU were statistically significantly higher for the test dentifrice compared with the placebo dentifrice (p < 0.0001 for all). No treatment-related or serious adverse events were reported.ConclusionsThe NaF-containing anti-erosion, dentin hypersensitivity dentifrice improved remineralisation of acid-softened enamel starting at 60 min of intra-oral exposure. It also improved enamel erosion resistance and fluoride uptake as early as 5 min after exposure to fluoridated dentifrice slurry.Clinical relevanceBrushing with a NaF-containing dentifrice can rapidly improve remineralisation, enamel erosion resistance and fluoride uptake.

Highlights

Dental erosion lesions are characterised by dissolution of the hydroxyapatite component of enamel, leading to demineralisation of the tooth surface and formation of a softened enamel surface zone [1, 2]
%SMHR At the 5- to 30-min specimen removal times, %SMHR was numerically higher for the test dentifrice compared with the placebo dentifrice; there was no statistically significant differences between them
Averaged across the 4-h assessment period, the mean %SMHR was 5.68 units higher in the test dentifrice group compared with the placebo dentifrice group

Summary

Introduction

Dental erosion lesions are characterised by dissolution of the hydroxyapatite component of enamel, leading to demineralisation of the tooth surface and formation of a softened enamel surface zone [1, 2]. At this stage, as the mineral and organic scaffold remains, the enamel surface can be repaired through remineralisation. It is generally established that calcium and phosphate, super-saturated in saliva, are deposited on the softened enamel surface during remineralisation, replacing the mineral structure lost during enamel dissolution and subsequently rehardening the surface [6, 7]

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