Deposition of Fluoridated Apatite during Remineralisation in situ

Method: In situ remineralisation data were analysed retrospectively. Briefly, enamel blocks containing artificial carious enamel lesions were worn intra-orally for two weeks, during which time subjects’ diets provided the sole cariogenic challenge. Four toothpaste formulations were tested in a randomised full cross-over design: 0ppmF, 250ppmF (as sodium fluoride (NaF)), 1100ppmF (as NaF, Aquafresh Fresh&Minty) and 1100ppmNaMFP (sodium monofluorophosphate). Subjects brushed with toothpaste for 60s twice-daily. Surface micro-hardness (SMH) was measured before and after treatment. Enamel fluoride uptake (EFU) was also determined. 

The mass of mineral deposited was calculated using the SMH data and the mass of fluoride deposited was calculated using EFU data. DS was expressed as a fraction of the value for complete substitution (pure fluorapatite). It was assumed that fluoride was associated predominantly with newly deposited mineral. A possible dose-response between toothpaste fluoride concentrations and DS was included (Pearson’s) (NaF only) and DS values were analysed (ANOVA). Differences were deemed to be significant at p < 0.05.  

Results: A significant positive dose-response relationship between DS and toothpaste fluoride concentration was observed. Mean DS values (SE) for 0ppmF, 250ppmF, 1100ppmF and 1100ppmNaMFP were 18.7(5.44)^a, 27.1(4.90)^b, 35.1(5.33)^c and 28.5(5.53)^b respectively (means with the same letter not significantly different).

Conclusion: The DS value resulting from use of the 1100ppmF (NaF) toothpaste approached the value associated with minimum fluorhydroxyapatite dissolution.