The most common bacteria associated with dental cavities are Streptococcus mutans, Streptococcus eminentis, Streptococcus sobrinus, and Lactobacillus. However, carcinogenic bacteria (those that can cause disease) are present in dental plaque, but they are usually in concentrations that are too low to cause problems unless there is a shift in the balance.[26] This has been attributed to local environmental change, such as frequent sugar intake or insufficient biofilm removal (toothbrushing).[27] If left untreated, the disease can lead to pain, tooth loss, and infection.[28]
The mouth contains a wide variety of oral bacteria, but only a few specific types of bacteria are believed to cause tooth decay: Streptococcus mutans and Lactobacillus species are among them. Streptococcus mutans are Gram-positive bacteria that form biofilms on the surface of teeth. These organisms can produce high levels of lactic acid after fermenting dietary sugars and are resistant to the harmful effects of low pH, properties necessary for carcinogenic bacteria.[23] Because the surface of root surfaces is more easily demineralized than enamel surfaces, a wide variety of bacteria can cause root caries, including Lactobacillus acidophilus, Actinomyces spp., Nocardia spp., and Streptococcus mutans. Bacteria collect around the teeth and gums in a sticky, cream-colored mass called plaque, which acts like a biofilm. Some sites collect plaque more commonly than others, eg sites with a reduced rate of salivary flow (molal fissures). Grooves on the occlusal surfaces of molar and deciduous teeth provide microscopic retention sites for plaque bacteria, as do interdental sites. Plaque may also collect above or below the gums, where they are referred to as supragingival or peri-gingival plaque, respectively.
These bacterial strains, most notably S. mutans, can be inherited by a child from a temporary kiss or through early feeding.[29]
