In situ remineralisation of eroded enamel lesions by NaF rinses

Objective: The purpose of this pilot study was to evaluate the remineralisation of eroded enamel by NaF rinses in an intra-oral model. Methods: Serving as their own control, subjects (N = 80) participated in a randomised, four-leg (20 subjects/leg), 28-day, parallel design study. In each leg, each participant wore a customised orthodontic bracket attached to a mandibular molar that contained one tooth block having an initial erosive lesion (0.3% citric acid, pH 3.75, 2 h). Within the 28-day period, participants engaged in twice-daily brushing for 1 min with a fluoride-free dentifrice followed by 1-min rinsing with one of the following aqueous rinses: fluoride-free (0 ppm F), 225 ppm F, 225 ppm F plus functionalised β-tricalcium phosphate (fTCP), and 450 ppm F. Following intra-oral exposure, appliances were removed and specimens were analysed using surface microhardness (SMH) and transverse microradiography (TMR). Results: Statistically significant (p < 0.05) remineralisation, as determined by SMH and TMR, of the eroded enamel relative to baseline occurred for each fluoride system. No significant differences in SMH were observed amongst the fluoride groups (p > 0.05), however, 225 ppm plus fTCP produced 27% and 7% SMH indent length reduction relative to 225 ppm F and 450 ppm F, respectively. No significant differences in TMR were observed amongst the fluoride groups (p > 0.05), however, 225 ppm F plus fTCP and 450 ppm F produced significant (p < 0.05) mineral gains relative to the fluoride-free control, whilst 225 ppm F did not (p > 0.05). Relative to the 225 ppm F group, the 450 ppm F and 225 ppm F plus fTCP groups produced 65% and 61% greater mineral change, respectively. Conclusions: These pilot results demonstrate this model is sensitive to fluoride and that addition of fTCP to an aqueous rinse containing 225 ppm F may provide significant remineralisation benefits. Therefore, the combination of relatively low levels of fluoride and fTCP might be an effective alternative to a high fluoride treatment for anti-erosion benefits.