The Effect of Varying the Amount of Fluoride in Milk and The Frequency of Its Application on Demineralisation/Remineralisation of Bovine Dental Enamel In Vitro

Aim: To investigate the remineralisation and/or demineralisation of artificially created white spot lesions (WSL) on bovine enamel following a daily or intermittent exposure to 0.5 mg F or 1.0 mg F added to bovine milk using a pH- cycling in vitro model and whether the higher dose would result in a better preventive effect. Methods: Bovine teeth were collected and sectioned for the creation of artificial carious lesions while ensuring that there was a margin of sound enamel surrounding the white spot lesion (n=151). The prepared enamel slabs were randomly allocated to one of 6 groups: Group 1: Dipped into 0.0 mg F in milk, in an interrupted frequency manner. Group 2: Dipped into 0.5 mg F in milk, in an interrupted frequency manner. Group 3: Dipped into 1.0 mg F in milk, in an interrupted frequency manner. Group 4: Dipped into 0.0 mg F in milk, in a daily frequency manner. Group 5: Dipped into 0.5 mg F in milk, in a daily frequency manner. Group 6: Dipped into 1.0 mg F in milk, in a daily frequency manner. The enamel slabs underwent a 60 day pH-cycling regimen where the slabs were subjected to fluoridated milk twice daily (before and after pH-cycling). The quantitative light fluorescence (QLF) machine was used as the method of analysis as it measures the percentage change of demineralised enamel fluorescence in relation to the surrounding sound enamel. Images were obtained at baseline and on completion of the study. Statistical Analysis: Shapiro-Wilk test was used to test the normality of the data. Analysis of variance (one way ANOVA) was used to compare the different concentrations of fluoride in milk while the paired sample T-Test was used to compare between the two frequencies (Interrupted and Daily) as well as between baseline and final
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readings. Results: Significant improvement (p<0.05) between baseline and final readings was obvious within all QLF parameters: ∆F (average loss of fluorescence), Area of the lesion and ∆Q (lesion volume) for all the fluoride concentration levels including the control (0.0 ppm F). When considering the frequencies separately ∆F and ∆Q showed a significant difference (p<0.05) between the control and 1.0 ppm F for the interrupted frequency while a significant difference for the daily frequency was found when comparing the highest fluoride concentration to the control and 0.5 ppm F. As for the comparison between both frequencies, it was apparent that although there was a general improvement in lesion remineralisation for all groups, ∆Q was only statistically significantly different (p<0.05) at the 0.5 ppm F level in favour of the interrupted frequency. Conclusions: Fluoridated milk was shown to be effective in remineralisation of artificially created sub-surface enamel lesions in bovine enamel with the most improvement demonstrated at 0.5 mg F used in an interrupted frequency manner. The results need to be interpreted with caution and there is still a need for more randomised clinical studies to confirm these findings.