The traditional way of viewing dental diseases, such as cavities and bleeding gums, is that they result from poor oral hygiene (a dirty mouth), too much sugar in the case of cavities, and possibly from some genetic component (soft teeth). There are very few treatment options other than meticulous oral hygiene, the placement of dental fillings and the extraction of diseased teeth. The dental problem could persist for a lifetime, or until the tooth is lost. This view, which I have called the Non Specific Plaque Hypothesis, is based on the observation that for most individuals with dental diseases, the bacteria which normally live on the tooth surfaces have overgrown, giving rise to visible accumulations of bacteria on the teeth in what is clinically called dental plaque.

Our research has been directed toward showing that both dental decay (caries) and periodontal disease (gum disease) are mainly specific bacterial infections due to the overgrowth of a limited number of bacterial types on the tooth surfaces. This concept we have called The Specific Plaque Hypothesis. This hypothesis has important implications in regard to treatment, as it states that only those individuals with an infection need to be treated, and once successfully treated, the individual may go for years without a recurrence of the infection. Thus, once a infection that causes dental decay is treated, the individual may not develop any more decay or cavities for the rest of his life. Of course there would be exceptions to this generalization, but these exceptions probably can be clearly identified with an external precipitating cause, such as a snacking habit involving sucrose containing compounds, reduced salivary flow, perhaps secondary to the use of anti-depressant medications, or to radiation treatment for oral cancer.

This generalization would also apply to periodontal disease although the bacteria and treatment involved are different. More information on each of these subjects can be accessed by clicking on the highlighted word.

This concept is illustrated in the text and figure below, which shows that three types of plaque can exist on the tooth surfaces:

1) a non-disease associated plaque,which results when good oral hygiene is practiced and frequent ingestion of sucrose is avoided.

2) a cariogenic plaque, which evolves from the non-disease associated plaque, occurs when sucrose is frequently ingested.

3) a periodontal plaque, which also evolves from the non-diseased associated plaque, occurs when oral hygiene is poor.

The majority of individuals have non-disease associated plaque on their tooth surfaces. A dental infection occurs when various members of the bacterial community are able to overgrow due to selection pressures in the environment. In the case of the cariogenic plaque, the frequent ingestion of sucrose selects for particular bacteria, like the mutans streptococci, that can efficiently use sugar . In the case of periodontal plaque, there is a selection of anaerobic bacteria that can grow in stagnant, low oxygen environments. The goal of dental treatment would be to restore an environment, on and around the tooth surfaces, that promotes the growth of those bacteria that are found in the non-disease associated plaque. There are various ways in which this can be accomplished (See Subsequent Sections under "Education").

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