This article is based on an original article in Swedish which can be found here

BACKGROUND

The amount and composition of saliva vary intra- and interindividually (1). Its quantity and composition affect the risk of developing various oral pathological conditions, including dental caries, dental erosions, and oral candidiasis, and play a significant role in the patient's self-perceived oral comfort as well as impacting overall quality of life.

Saliva is produced by three paired major salivary glands: the parotid gland, sublingual gland, and submandibular gland, as well as a large number of minor accessory salivary glands. Salivary secretion is usually differentiated into glandular saliva and mixed saliva. Glandular saliva is the saliva formed by acinar cells in the salivary glands and consists of water (>99%), proteins, and electrolytes. Mixed saliva contains, in addition to these substances, bacteria, leukocytes, and desquamated epithelial cells originating from the passage through the ducts and from the oral environment.

The stimulated saliva, whose secretion amount can be ten times greater than that of resting saliva, is primarily produced by the parotid gland, but the submandibular and sublingual glands as well as the small accessory glands also contribute to the total amount. The production is largely controlled by mechanoreceptors that respond to chewing, but also by taste and smell. It has been shown that individuals consuming a liquid diet exhibit reduced secretion of stimulated saliva (2, 3) and that there is a positive correlation between the intake of hard food, the presence of measured increased bite force, and increased stimulated salivary secretion (4, 5). The unstimulated saliva is primarily produced by the submandibular and sublingual glands. Since the composition of saliva produced in the different glands varies, the stimulated and unstimulated saliva also differ in terms of viscosity and other properties.

Parotid gland produces the thin, serous saliva that is important for oral clearance and buffering of acids. It contains a high concentration of amylase and electrolytes, which among other things contribute to the breakdown of starch, have antimicrobial properties, and promote remineralization. The sublingual gland, submandibular gland, and the minor glands produce the mucous, viscous saliva whose primary function is to lubricate mucous membranes and teeth, thereby contributing to comfort and protecting mucous membranes (6).

Humans have a baseline flow of saliva that is influenced by several factors such as circadian rhythm, season, diseases, and medication. Anatomical and physiological factors can also affect salivary secretion. With age, there is often a reduction in salivary secretion, particularly regarding saliva production from the submandibular and sublingual glands (1). Healthy physiological aging does not automatically lead to reduced salivary secretion.

There are several methods for measuring salivary secretion, but this document will only describe the most common method that is easy to perform clinically. Additionally, the methodology for buffering tests and quantitative measurement of cariogenic bacteria in saliva will be presented.

ETIOLOGY/INDICATION

The most common causes of reduced salivary secretion are

• Side effects of medication
• Pathological conditions (general and local)
• As a side effect after chemotherapy

For more information, see article on Dry Mouth

It is of intrest to perform salivary diagnostics on all caries patients, but specifically on those who have not responded to previous treatment or where the cause of the disease could not be determined.