Dental caries is arguably the most prevalent disease in man, affecting most of the dentate population at some time in their lives. In the United States, dental caries is the most common chronic disease in childhood, with 42% of children between the ages of 2 and 11 having had caries in primary teeth and 23% of children in this same age group having untreated dental caries.1 Among dentate adults aged 20 to 64, 91% have caries in permanent teeth.2 Commonly termed “tooth decay,” caries is the localized destruction of tooth tissues over time by acid that is produced in the mouth when oral bacteria, such as Streptococcus mutans, ferment dietary carbohydrates. These bacteria aggregate in dental plaque that forms on the outer surface of teeth. In a healthy mouth environment, the bacteria that populate plaque are harmless, but when the environment becomes acidic, the population changes to bacteria that thrive in acidity and are linked to caries. A combination of several factors and sub-factors are required for dental caries to develop, including some that are innate to the oral environment, making caries a multifactorial disease that can be difficult to manage and completely prevent. The caries process, the multiple factors that influence caries development, and plaque as a microbial biofilm ecosystem, are discussed.