Saliva is secreted by the salivary glands
Saliva is produced in the mouth both by small salivary glands in the mucosa and also by the large salivary glands – the glandula parotis (parotid gland), the glandula submandibularis (sub-mandibular gland) and the glandula sublingualis (sub-lingual gland).
Depending on the gland the saliva is rather watery (serous) or slimy (mucous). The small glands mainly produce mucous saliva, the large mainly serous. In the oral cavity there is therefore a mixture of these different types of saliva. An adult produces about 0.6 to 1.5 litres of saliva per day. Even without absorbing nutrition saliva is produced constantly.
Saliva contains many different components, including complex polysaccharides, various proteins, ions (such as calcium, kalium, natrium and chloride) and traces of fluoride and rhodanide. Blood group components and antibodies are also to be found in saliva.
Saliva contains numerous mineral salts necessary to maintain the hardness of dental enamel and to protect it from the attack of acids. Almost every time we eat something bacteria convert the sugar contained in the food into acid. This causes caries since it attacks the surface of the tooth and destroys the minerals there. The natural protective function goes into action: saliva contains natural mineral components which dilute and destroy these acids. In addition saliva supports the absorbtion (remineralisation) of minerals in the enamel which harden the teeth, thereby acting against the creation of caries. As long as there is a balance between demineralisation and remineralisation there won’t be problems.
However, too many snacks containing carbohydrates eaten between meals will overload this defence system.
The first sign of oncoming caries (initial caries) is a white spot. There’s more about this in the video ‘Initial Caries’. At this stage the process can be reversed with fluorides. More about this in the videoSealing Caries. Our saliva doesn’t only protect our teeth, however; by keeping our mouths wet it enables us to swallow, speak and taste. Saliva also has an antibacterial effect through the substances it contains, such as lysozyme, immunoglobin A, lactoferrin and histatin. In addition saliva promotes the absorbtion of vitamin B12.
A temporary increase in the flow of saliva is usually a reflex triggered by particular external influences:
- Taste: stimulation of the taste buds by materials put in the mouth
- Touching: stimulation of the sensory nerves in the mouth
- Smell: stimulation of the olfactory nerves in the nasal sinuses
- Sight: stimulation of the optical nerves in the orbits
- Stimulation of the stomach and intestinal nerves in the digestive tract
If over-production of saliva persists – a condition called sialorrhoea – this can be a sign of illness, as can under-production of saliva – xerostomia. There’s more about these conditions in the videos with the same names.