pH and Buffering

Salivary pH is important, but highly variable due to several factors. A healthy resting saliva pH falls between 6.8 to 7.2. Saliva in this range favors homeostasis, creating an environment that supports remineralization, the suppression of pathogenic microbes, and favors the growth of non-pathogenic commensal oral microflora. Healthy saliva also contains sufficient levels of bicarbonate ions, other proteins that can buffer acids, and sufficient levels of calcium and phosphorus.2,31,32,36 Patients with low salivary flow rates typically exhibit a more acidic salivary pH.37

When salivary glands are stimulated, the quality of saliva improves, due to an increased concentration of protein, sodium, chloride, and bicarbonate. Bicarbonate concentration, also known as buffering capacity, can immediately neutralize oral acids.2,30,31,38,39 Salivary proteins provide a secondary pathway for neutralizing plaque acids.2,31 A number of microbes metabolize the amino acid arginine via the three-enzyme pathway known as the arginine deaminase system (ADS). The metabolic biproduct of the ADS is alkaline, which functions to neutralize oral acids, as well as create an environment that supports a healthy commensal microbial community.40