The gradual recovery of the plaque pH is influenced by various factors. These include the buffering capacity of saliva, whether fermentable carbohydrate remains in the mouth, the pH value (which may be unfavorable to bacterial enzyme systems) and the diffusion of acids from plaque into saliva or teeth. It is also influenced by base production in plaque. Ammonia from the deamination of amino acids and breakdown of urea in saliva are examples of reactions that contribute to the pH rise. These bases are important to neutralise acid when carbohydrate intake is moderate.13 The rise in pH may also be assisted by the removal of acids by bacteria, such as those from the genus Veillonella that use lactate as a substrate, metabolising it to less acidic products.6
Figure 7. How Veillonella reduces caries risk by reducing plaque pH acidogenicity.