Composition of saliva
The composition of saliva is subject to individual variation. It consists of 99.5% water and 0.5% dissolved substances that are made up of:
■ Salivary proteins. These include:
- Glycoproteins (mucoids): lubricate oral tissues; the acquired pellicle provides tooth protection.
- Enzyme amylase: converts starch to maltose.
- Lactoferrins: ferric iron is an essential microbial nutrient; lactoferrins bind to ferric ions, producing an antibacterial effect.
- Lysozomes: attack the cell walls of bacteria, protecting the oral cavity from invading pathogens.
- Sialoperoxidase (lactoperoxidase): controls established oral flora by controlling bacterial metabolism.
- Histatins: inhibit Candida albicans.
- Statherin: inhibits precipitation of calcium phosphates.
- Proline-rich proteins: encourages adhesion of selected bacteria to the tooth surface. They inhibit precipitation of calcium phosphates.
- Salivary immunoglobulins: produce protective antibodies which help to prevent infection.
■ Inorganic ions: bicarbonate and phosphate ions provide a buffering action, which regulates the pH of the oral cavity. Calcium and phosphate ions maintain the integrity of teeth by providing minerals for newly erupted teeth which helps with the post-eruptive maturation of enamel and prevents tooth dissolution by enhancing the remineralisation of enamel. Small amounts of sodium, potassium, chloride and sulphate can also be found in saliva.
■ Gases: newly formed saliva contains dissolved oxygen, carbon dioxide and nitrogen.
■ Other additives: urea is formed as a waste product.
Saliva also contains a vast number of microorganisms and remnants of food substances.