Dental caries is a biofilm disease that results in the localized destruction of tooth tissues by acid, such as lactic acid, that is produced in the mouth as oral bacteria ferment dietary carbohydrates. If the pH in the environment surrounding tooth tissues becomes too acidic, dropping below a pH of 5.5, then demineralization of tooth enamel–essentially dissolution of tooth structure–begins to occur. The early stages are reversible, because the natural process of remineralization can replace lost enamel. However, if demineralization continues over time, enough mineral content may be lost so that the soft organic matrix left behind disintegrates, forming a cavity.
Dental caries is an infectious disease, but technically, although it is transmissible, one does not “catch” dental caries. The oral bacteria that cause dental caries when they thrive under certain specific conditions populate the oral cavity of all humans, first entering the body when a baby passes through the birth canal. It is more accurate to consider caries as caused, not by an infectious agent, but by a shift in oral microflora to caries-causing bacterial types in response to a shift to an acidic pH caused by metabolism of sugars.
Theories about what cause cavities go as far back as 2500 BC in ancient China when it was thought that “toothworms” caused cavities.3 This belief continued for several centuries in many different cultures. Later, in 350 BC, Aristotle and others acknowledged that sweets and figs caused decay.4 It wasn’t until 1819, that Levi Parmly hinted at the real cause of caries: that decay begins on the surface of the teeth by bacteria growing on food particles which lodge around and between teeth, causing destruction of tooth structure.5
Caries theory was marked in the 1880s by Miles and Underwood stating in 1881 that acid and “germs” were necessary for decay, while W.D. Miller formulated the concept of caries as a local phenomenon associated with carbohydrate retention and acidogenic bacteria in 1889.6 In the early to mid-1900s, dental research uncovered several important findings: In 1938, H. Trendley Dean linked fluoride to caries reduction, and in later studies, high sugar consumption was linked to caries, but only in an environment where oral bacteria were present.6,7
In 1955, Procter & Gamble introduced Crest®, the first fluoride toothpaste clinically proven to be effective in preventing dental caries. It was hailed as a major scientific breakthrough, and received an endorsement from the American Dental Association (ADA) as an “effective decay-preventive dentifrice that can be of significant value.” In the 1990s, and repeatedly since, the ADA has emphasized the benefit of fluoride, stating: “A comprehensive analysis of the fifty-year history of community water fluoridation in the United States further demonstrated that the inverse relationship between higher fluoride concentration in drinking water and lower levels of dental decay discovered a half-century ago continued to be true.”8