Chelating effect of citric acid is negligible for development of enamel erosions

Abstract

Aim

Citric acid (CA) is a component in beverages responsible for dental erosion. The aim of this study was to examine the influence of CA with different pH, titratable acid and buffer capacity (ß), and the impact of the chelating effect of CA on development of enamel erosions.

Material and methods

In a superfusion model, hydroxy apatite (HAp) dissolution of bovine enamel was measured in four experiments (EXP 1-4) with 27 experimental groups (n = 8 per group). The samples were superfused with different CA variations and respective controls. EXP-1: Dilution series of HCl (pH 2.15–3.02). EXP-2: Dilution series of natural CA (56–1.75 mmol l⁻¹; pH 2.15–3.02). EXP-3: CA solutions (56 and 14 mmol l⁻¹, ß: 39.7 and 10.2 mmol l⁻¹ pH⁻¹, respectively) with different titratable acidity at equal pH values. EXP-4: CA concentrations (56–1.75 mmol l⁻¹) neutralized to pH 7.

Results

CA led to higher HAp-dissolution than HCl. With higher pH, the difference in HAp-dissolution rate between the two acids became increasingly smaller. At equal pH, HAp-dissolution was higher for the CA with the higher amount of titratable acid. However, no clear correlation between erosion and titratable acid or ß could be found. Only minimal amounts of HAp were dissolved by neutralized CA compared to CA with natural pH.

Conclusion

Under the chosen conditions chelating effects of CA do not have a relevant influence of HAp-dissolution of enamel. Moreover, amount of HAp-dissolution by CA is not attributed to a single factor alone. The interplay between the different parameters of CA seems to be responsible for its erosive potential.

Clinical relevance

The erosive potential of solutions containing citric acid with unknown concentrations could not be predicted using a single parameter alone, and should at best determined in experimental set-ups.