saliva

biochemistry

Also known as: salivary secretion

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Related Topics:: salivary gland; bolus

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saliva, a thick, colourless, opalescent fluid that is constantly present in the mouth of humans and other vertebrates. It is composed of water, mucus, proteins, mineral salts, and amylase. As saliva circulates in the mouth cavity it picks up food debris, bacterial cells, and white blood cells. One to two litres of fluid are excreted daily into the human mouth. Three major pairs of salivary glands and many smaller glands scattered in the surface tissue of the cheeks, lips, tongue, and palate contribute to the total amount of saliva. Small amounts of saliva are continually being secreted into the mouth, but the presence of food, or even the mere smell or thought of it, will rapidly increase saliva flow.

The functions of saliva are numerous. Primarily, it lubricates and moistens the inside of the mouth to help with speech and to change food into a liquid or semisolid mass that can be tasted and swallowed more easily. Saliva helps to control the body’s water balance; if water is lacking, the salivary glands become dehydrated, leaving the mouth dry, which causes a sensation of thirst and stimulates the need to drink. Saliva reduces tooth decay and infection by removing food debris, dead cells, bacteria, and white blood cells. It also contains small amounts of the digestive enzyme amylase, which chemically breaks down carbohydrates into simpler compounds.

This article was most recently revised and updated by Michele Metych.

public health dentistry

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public health dentistry

Written by Malvin E. Ring

Fact-checked by The Editors of Encyclopaedia Britannica

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Related Topics:: dentistry

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public health dentistry, dental specialty concerned primarily with prevention of dental decay and of periodontal disease (disease of the tissues surrounding the teeth). Public health dentistry is practiced generally through governmentally sponsored programs, which are for the most part directed toward public-school children in the belief that their education in oral hygiene is the best way to reach the general public. The pattern for such programs in the past was a dentist’s annual visit to a school to lecture and to demonstrate proper tooth-brushing techniques. The 1970s saw the emergence of a more elaborate program that included a week of one-hour sessions of instruction, demonstration, and questions and answers, conducted by a dentist and a dental assistant and aided by a teacher who had previously been given several hours of instruction. Use was also made of televised dental health education programs, which parents were encouraged to observe.

On a larger scale, public health dentistry has been concerned with the improvement of oral health in large populations. Thus, the fluoridation of municipal water supplies in the mid-1940s resulted from research studies conducted by the U.S. Public Health Service. This service is also involved in the delivery of dental care to specialized populations, including Native Americans on reservations, as well as the Eskimo population of Alaska.

Malvin E. Ring