What is the primary caries-causing bacterium in the oral cavity?

The primary caries-causing bacterium in the oral cavity is Streptococcus mutans. This bacterium is a key contributor to dental caries due to its ability to metabolize sugars and produce acid as a byproduct. The acid production from carbohydrate fermentation leads to demineralization of the tooth enamel, creating an environment conducive to cavity formation.

Streptococcus mutans is particularly successful because it can adhere to the tooth surface, forming biofilms known as dental plaque. This biofilm provides a protective environment for the bacteria and enhances their ability to produce acid over time, further contributing to enamel breakdown and carious lesion development.

While other bacteria such as Lactobacillus casei and Actinomyces naeslundii also play roles in caries development, they are not considered the primary initiators. Lactobacillus is often more involved in the progression of caries rather than the initial formation. Escherichia coli, while a common bacterium in the gut, is not typically associated with oral health and caries. Thus, recognition of the predominant role of Streptococcus mutans is essential in understanding the etiology of dental caries.