Which bacterium is the main species associated with human dental caries, or tooth decay?

Streptococcus mutans is the bacterium most strongly associated with human dental caries, or tooth decay.

The species lives in dental plaque, the biofilm that develops on tooth surfaces. It uses sugars from food and drinks, especially sucrose, to produce acids and sticky extracellular substances. The acids can dissolve minerals in tooth enamel and dentine, while the sticky materials help the bacterial community remain attached.

S. mutans is not the only microorganism involved in cavities. Dental caries is a polymicrobial disease influenced by diet, saliva, oral hygiene, fluoride exposure, and the broader plaque community. However, S. mutans became the classic laboratory and textbook example because of its acid production and ability to form plaque-associated biofilms.

A common mix-up is confusing it with Streptococcus pyogenes, which causes strep throat, or Streptococcus pneumoniae, which can cause pneumonia and meningitis. Regular brushing with fluoride toothpaste helps reduce the conditions that allow acid-producing plaque bacteria to damage teeth.