Efficacy of combining soluble calcium and pyrophosphate with sodium fluoride in inhibiting enamel caries progression: An in vitro study

Objective

This study aimed to compare the effects of a combination of sodium fluoride, soluble calcium, and pyrophosphate (FCaP) versus fluoride alone in inhibiting enamel caries progression.

Design

Different FCaP solutions were prepared, and two were selected for testing (FCaP-1: F = 76 mmol/L, Ca = 7.6 mmol/L, P = 7.6 mmol/L, FCaP-5: F = 76 mmol/L, Ca = 23 mmol/L, P = 23 mmol/L). Fluoride solution (F = 76 mmol/L) was used as a control. Fluoride and calcium bioavailability in the solutions were measured, and NMR analysis was used to identify fluorine-containing complexes. Sound bovine enamel samples (n = 24 / group) underwent a 4-day pH cycling protocol followed by an additional 3 days of demineralization. Micro-hardness testing and fluoride concentration measurements were performed.

Results

FCaP-1 and FCaP-5 demonstrated nearly 100 % fluoride and calcium bioavailability. NMR analysis confirmed the formation of fluorine-containing complex. Enamel treated with FCaP-5 exhibited significantly less reduction in subsurface hardness after pH cycling and additional demineralization compared to fluoride alone. Interestingly, fluoride concentration and acid resistance on enamel surfaces treated with FCaP-5 was lower than with fluoride alone (Steel’s multiple comparison test, p < 0.05).

Conclusions

FCaP effectively inhibits caries progression in subsurface enamel layers under pH cycling conditions by providing bioavailable calcium, indicating that FCaP increases the effectiveness of fluoride in caries management. FCaP may be a valuable addition to clinical practice, particularly for improving the effectiveness of fluoride-containing oral care products in individuals with low salivary calcium levels.