Dental caries could be defined as demineralization of the inorganic and destruction of organic portions of the calcified tissues of the tooth.

It is one of the leading causes of tooth loss amongst children

This is a slow and continuous process with periods of arrest in the progress to even partial repair. There is no clear stage where one can say that this is the initial stage.

Even within a single mouth, individual sites of each tooth vary greatly in their susceptibility.

The earliest manifestation of progression of caries could be the subsurface demineralization of the tooth enamel due to acids produced on fermentation of carbohydrates by plaque bacteria.

The measure of the number of teeth that are diseased, missing of filled is known as the DMF [diseased missing or filled] index. This is the most common epidemiological measure of dental caries. When expressed as the number of teeth, the index is called DMFT. WHO had stated that by 2000 AD no country should have a DMFT of more than 3 by the age of 12.

Proposed causative factors for caries: [in any order]

- improper dental hygiene

- eating foodstuffs with higher glycemic index

- improper food habits

- dental infections

- Persistent dry mouth.[xerostomia]

Earlier, carries was seen in the developed countries since they were more inclined to eat sugar rich food, in-between meals. On the other hand, the underdeveloped and developing countries could not afford such frequent meals and their diet consisted to high fiber and hence did not develop caries.

However, by the 80s, the developed nations took notice of this and introduced a slew of measures like,

- increased dental hygiene awareness

- fluoridation of water

- antibiotic use

- preventive dentistry

- more dentists

What we are seeing now is that the incidence of caries in western world has decreased and it is becoming prevalent in developing and under developed nations due to urbanized lifestyle and fast food culture. In short the pattern which was seen in the developed countries before the 80s.

Acidogenic theory:

In 1889, WD Miller postulated that "acids formed due to the fermentation of dietary carbohydrates by oral bacteria leads to progressive decalcification of the tooth structures with subsequent disintegration of the organic matrix"

This is the most widely accepted theory in the pathophysiology of dental caries.

Miller described four important factors which he believed that lead to dental caries.

- microorganisms

- dietary carbohydrates

- acids

- dental plaque

Microorganisms:

Though there are a large number of microorganisms in our oral cavity, the ones which play a significant role in caries tooth are Streptococcus mutans and lactobacilli, of which S. mutans is the clear culprit.

S. mutans readily ferment dietary carbohydrates to produce acids

Lactobacilli are acidophilic; they thrive in acidic environment and are an indicator of active caries lesions.

Dietary carbohydrates

Glucose, sucrose and fructose are rapidly fermented by the above mentioned bacteria to produce acids causing demineralization of tooth

Sucrose is the most important of all since it is readily taken up by S. mutans

When sucrose is replaced by sorbitol or xylitol [non-fermentable carbohydrates], the incidence of caries reduced drastically.

Acids:

A lot of concern is shown in keeping the pH of the tooth minerals above the critical level of pH 5.5.

When the pH falls below this level, the subsurface demineralization starts causing, incipient caries formation.

Dental plaque:

It is a transparent film produced on the surface of the tooth and it harbors the caries forming microorganisms. It allows the acids to remain viable for a longer duration by shielding it from the buffering action of the saliva.

Preventive and Curative measures:

Regular dental check up

Reduce or eliminate sucrose from diet.

Avoid consumption of sucrose in the in-between meals

Regular mouth rinse by chlorhexidine

Antibiotic treatment [tetracycline and vancomycin]

Regular brushing and floss to eliminate plaque

Restore tooth surface by sealing etc

Increase salivary flow by having chewing the food bolus properly.

Caries vaccine, usually given before 6 months of age, could be an effective mode of preventing caries