Effects of pH and concentration of citric, malic and lactic acids on enamel, in vitro

Objective: Dental erosion associated with soft drink consumption probably r esults from the contained dietary acids in the formulations. The pH value o f any formulation is an important variable in acid erosion but not necessar ily the only important factor. The aim of this study was to measure enamel erosion by citric, malic and lactic acids at pH values and acid concentrati ons representative of a range found in soft drink formulations and to deter mine the effect of adding calcium to citric acid. Methods: Flat ground enamel samples were prepared from unerupted human thir d molar teeth. Groups of five specimens were placed in citric, malic and la ctic acid solutions of different pH and acid concentration for three by 10 min exposures at 35 degrees C. Enamel loss was measured by profilometry. En amel specimens were also exposed to citric acid solutions containing calciu m at different pH values and at the same pH with different concentrations o f calcium. Results; Numerical data and contour plots for each acid showed a similar pa ttern for increasing erosion with decreasing pH and increasing acid concent ration and vice versa for decreasing erosion, increasing the concentration of calcium in a fixed pH citric acid solution resulted in decreased erosion . This effect was most marked at higher pH. Conclusions: This study has shown that under highly controlled conditions t he erosion of enamel by solutions of dietary acids is influenced by the int erplay of pH, acid concentration and presence of calcium. These variables a nd in particular the concentration of calcium could be manipulated to produ ce soft drinks with reduced erosivity to enamel. (C) 2000 Elsevier Science Ltd. All rights reserved.