Dental Caries Causes

Dental caries is produced by the interrelationship of four factors :

1. The susceptible tooth surface (host)

2. Specific microorganisms (bacteria)

3. Fermentable carbohydrates predominantly in the form of sucrose (substrate)

4. Time[1]

Dental plaque is composed of a variety of acidogenic microorganisms. Streptococcus mutans is the specific causative microorganism implicated in dental caries. These microorganisms have the potential to synthesize carbohydrates into extracellular polysaccharides (dextrans, levans, and other glucans and fructans) and intracellular polysaccharides, which are stored. Extracellular polysaccharides assist in the formation and adherence of plaque to the tooth.

Streptococcus sanguis and streptococcus mitis are involved in enamel caries, whereas Actinomyces viscosus and Actinomyces naeslundii are involved in root caries.[2]

When a fermentable carbohydrate is eaten, enzymes in the bacterial plaque break down the foodstuff and form an acid. The acid demineralizes the tooth surface, and eventually, with repeated exposures to fermentable carbohydrates, particularly sucrose, a carious lesion results. In the absence of cariogenic foods, stored intracellular polysaccharides can convert to an acid.

The formation of acid begins immediately when the sucrose from food becomes incorporated into the bacterial plaque. The pH drops to an average level of 5.0 and remains at that acidity for approximately 20 minutes for each cariogenic exposure. It takes 1 to 2 years from the initial attack of organic acids on the tooth surface to form a clinically detectable carious lesion. [3]

A diminished salivary flow can also contribute to caries by interfering with the proper oral clearance of cariogenic foodstuffs. The natural buffering capacity of the saliva, which functions to neutralize acids formed during carbohydrate fermentation, is impaired when salivary volume decreases. Flow rate is less in females, when in darkness, when lying down, and diminishes with age or during warmer weather.[4]

References :

[1] Newbrun, E, 1983, Cariology, Baltimore, William & Wilkins

[2] World Health Organization : 1972, The Etiology and Prevention of Dental Caries. WHO Technical Report Series, #494. Geneva, World Health Organization

[3] Nizel, A.E., Papas, A.S., 1989, Nutrition in Clinical Dentistry, 3rd Ed. Philadelphi, W. B. Saunders

[4] Dunning, J.M., 1986, Principles of Dental Public Health. 4th Ed. Cambridge, MA, Harvard University Press