pH Dose-response of a Cycling Model for Initial Enamel Erosion

Objectives: In vitro models should mimic situations close to the real conditions and pH is an important chemical factor that influences dental erosion, ranging from 2.0 in soft drinks to 4.0 in juices. Thus, the aim of this study was to evaluate the pH dose-response effect of a cycling model for initial enamel erosion.
Methods: The model lasted 5 days and bovine enamel slabs (n=12/group), selected according to surface hardness and profilometric analysis, were immersed in human saliva for 1 h at 37°C for the formation of acquired pellicle in the beginning of each day. To evaluate the pH dose-response, the slabs were treated 4 times daily for 1 min with citric acid solutions (25 mL/mm² enamel area) at pH 2.5; 3.5; 4.5; 5.5 or 7.0 and cacodylate solution pH 7.0 was used as negative control. The concentration of the solutions was 47.6 mM. Between the treatments and during the night, the slabs were immersed in artificial saliva at 37°C. Daily, at the end of the cycling, and after immersion in artificial saliva during the night, the slabs were evaluated for surface hardness to calculate the percentage of surface hardness loss (%SHL) and, at the end of the experiment, profilometry analysis was performed again. The results were analyzed by ANOVA and Tukey test.
Results: The results showed a gradual increase in %SHL as a function of days in most of the groups. On the 4^th cycling day, a dose-response effect was found because significant differences were observed among all groups (p<0.05). Regarding profilometry, slabs treated with citric acid pH 2.5 and 3.5 for 5 days showed the highest surface losses, differing from each other and from all the other groups (p<0.05).
Conclusions: The findings suggest that the 4-day model is suitable to estimate the effect of pH of dietary products on early enamel erosion.