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.

Clinical Significance Snapshots

Simply put, what causes dental decay? How can I explain it to my patients?

Dental decay is caused when bacteria that accumulate on the surfaces of the teeth feed on sugars in the diet, and convert the sugars into acids that then dissolve the hard tooth material. This results in the loss of minerals, which in turn results in cavities.

Nearly every mouth contains the bacteria that can cause decay. The mouth can withstand several attacks each day from the bacteria that turn sugar into acid. During times between meals (with sugar), it is possible for the tooth to repair itself, replacing the minerals that have been dissolved by the acids. Fluoride in toothpaste helps make teeth more resistant to the acid attack. It is important to clean teeth well to remove as much bacteria as possible, and for those at high risk of developing caries to finish meals with items that are rich in calcium, such as yogurt, milk, or cheese.

Once sufficient mineral has been lost, the tooth forms a cavity that can only be repaired by the dentist placing a filling. The decay process starts with the appearance of a white spot on the surface of the tooth.

Of all the factors listed, what are the most important to control in order to prevent the onset of dental caries?

The frequency of intake of sugars should be reduced as much as possible, and, ideally, limited to mealtimes, so that acids in dental plaque are only produced 3 or 4 times a day, and that there is plenty of time between meals for saliva to act by replacing any minerals that have been dissolved by the acid production during mealtimes. The presence of fluoride makes enamel more resistant to acid dissolution and encourages the process of remineralization. Removal of plaque biofilm is important too, though it is impossible to remove all decay-causing bacteria from the mouth. Therefore, the next most important action, after reducing the frequency of sugars in the diet, is to brush at least twice a day with a fluoride toothpaste that strengthens the enamel against acid attack, encourages remineralization, and removes the plaque biofilm.