The effects of smoothies on enamel erosion: an in situ study

Aims: To measure, in vitro, the pH and titratable acidity (TA) of various soft drinks and to assess the effect of smoothies on erosive tooth surface loss of enamel following a 21-day pH cycling protocol using an in situ model. Methods: The inherent pH of various soft drinks was measured using a pH meter. The TA was determined by titration with NaOH. An upper removable appliance capable of retaining two enamel slabs was constructed and worn by 14 volunteers. The drinks under test were Innocent® strawberries and bananas smoothie and citric acid. Participants were instructed to dip the appliance in the test solutions extra-orally five times daily for two minutes for 21-days. Measurements of enamel loss were made by surface profilometry and microhardness. Results: Diet Coke was found to be the most acidic drink (pH=2.61) while Innocent® mangoes and passion fruit smoothie was the least (pH=3.9). With regard to TA, Innocent® blackberries, strawberries and blackcurrants smoothie had the highest TA requiring 10.8 mol of NaOH to reach pH 7.0 while citric acid required only 3.1 mol of NaOH to reach the same pH value. The mean tooth surface loss following exposure to citric acid and Innocent® strawberries and bananas smoothie was 28.43 μm (S.D±10.25) and 2.88 μm (S.D±2.13) respectively. Citric acid caused a significantly greater tooth surface loss compared to smoothie. A statistical significant difference (change) in indentation length and enamel microhardness was found before and after exposure to test materials. Citric acid caused significantly greater difference (change) in indentation length and enamel microhardness compared with smoothie. Conclusion: Smoothies are acidic and have high TA levels. Innocent® strawberries and bananas smoothie had an erosive potential to the teeth. However, its erosive effect was significantly less compared to citric acid after 21-days pH cycling protocol using an in situ model.