Chemical factors - Acids

Acid content is the main chemical factor and the basis for erosive processes.

Acids:


1. Definition:

  • A compound that has a pH below 7 when dissolved in water.
  • The amount of hydrogen ions (H+) freed from acid molecules defines the reduction in pH of the solution and the acidity of the compound.


2. Characterization:

  •  The general reaction equation for the dissociation of an acid (HA) is: HA <–> A- + H+    (HA = acid).
  • Acids vary their ability to dissociate, which is defined by the pKa or the acid dissociation constant. In principle, the pKa reflects the ratio between the concentration of dissociated and undissociated acid. The lower the pKa, the stronger the acid.
     
a. Titratable acidity:
  • Acids have varying titratable acidities.
  • Titratable acidity measures the total amount of a defined base needed to neutralise a liquid.
  • Acids can be neutralised with bases to form water and salts.

b. Saturation:
  • The erosive potential of a compound largely depends on its saturation with tooth minerals (Ca2+, CO32-, F- from hydroxyapatite) as during erosive processes, acids (H+ ions) react with anions from tooth minerals.
  • The higher the saturation of tooth minerals in a compound, the lower the erosive potential.


3. Summary:


The erosive potential of foods and drinks is determined by their degree of saturation with tooth minerals and other chemical characteristics (Lussi & Jaeggi 2006a).

Below are different chemical factors that influence the erosive potential of food and beverages:
  • pH and titrable acidity of the product
  • Type of acid (pKa values) and acid concentration
  • Adhesion of the product to the dental surface
  • Chelating properties of the product
  • Calcium, phosphate and fluoride concentration