Salivary pH Kinetics After Using Solutions with Varying pHs/Titratable Acidities

Objectives: The pH and titratable acidity of beverages has been considered the main factors responsible for their erosive effect on dental surface, overcoming the salivary buffer capacity, but the effect of these parameters on salivary pH has not been studied in details. Therefore, we evaluated the kinetics of salivary pH after the use of acidic solutions with distinct pHs and titratable acidities. Methods: In a crossover study of 6 phases, 20 adult volunteers were subjected to one of the groups of treatments: Solutions of pH 2.5 or 3.5 adjusted with HCl and solutions of pH 2.5 and 3.5 buffered with 25 or 100 mM of citric acid. The volunteers kept 15 mL of each test solution in the mouth for 10 s and the pH of the expectorated was determined. Further, aliquots of saliva were collected for up 2 min (at 15, 30, 45, 60, 90 and 120 s) for pH determination. Salivary baseline pH was determined before each test. The pH was determined using a pH microelectrode. Data were analyzed by two-way ANOVA and Tukey test. Results: Baseline salivary pH averaged 7.4±0.3. The pH of the expectorated solution was significantly lower for the groups with the lower pH (p<0.05). After 15 and 30 s, lower salivary pH was observed for the groups using the highest concentration of citric acid (4.9±0.7 at 15 s and 5.8±0.8 at 30 s) and higher in groups not buffered (6.6±0.4 at 15 s and 6.7±0.5 at 30 s) (p<0.05), with no significant effect of pH (p>0.05). From 60 s, there was no difference between groups (p>0.05). Conclusions: The results suggest that while pH per se is an important factor for the erosive effect of a beverage when it is being drunk, the titratable acidity enhances this effect delaying the return of salivary pH to normal.