The effect of pH on the erosion of dentine and enamel by dietary acids in vitro

The reported incidence of tooth erosion caused by acidic soft drinks has be en increasingly documented. Citric and phosphoric acids are the two main di etary acids present in these soft drinks. Many variables need to be determi ned in order to assess risk-factors for dental erosion caused by beverage c onsumption including pH, titratable acidity, pKa, buffering capacity, hence the aim of these in vitro investigations. Methodologies included profiling flat enamel and dentine samples (< +/- 0.3 <mu>m profile) from unerupted h uman third molars. Groups of five specimens were placed in acidic solutions adjusted with alkali over the available pH range; citric, phosphoric and h ydrochloric acid were adjusted with sodium hydroxide and citric acid with t risodium citrate. Tissue loss was calculated by profilometry. Results showe d that under these conditions citric acid caused far more erosion over the pH range employed than phosphoric acid for both tissue types. Citric acid c ompared with hydrochloric acid highlighted dissolution and chelation effect s. Phosphoric acid caused minimal erosion over pH 3 for enamel and pH 4 for dentine. These factors could be considered in order to reduce the erosivit y of acidic soft drinks.