Bacteria
The primary bacteria involved in the pathogenesis of caries is Streptococcus mutans, but many other bacteria have also been implicated, including S sobrinus, Actinomyces sp, and Lactobacillus sp. Recent evidence demonstrates that these bacteria can be found in the mouths of predentate infants, having been transmitted from the mouth of the primary caregiver (usually the mother). Increased numbers of bacteria increases a child’s risk for caries.

Plaque is composed of salivary proteins that adhere to teeth, as well as bacteria and their byproducts. Plaque harbors the bacteria that initiate the demineralization process, and frequent removal can reduce the likelihood of developing dental caries. S mutans is concentrated in the pits and fissures of teeth, so the grooved surfaces of the molars are the most common site for caries.

The virulence patterns of Strep mutans vary with the strain, and families usually have the same strains. The type of S mutans cannot be modified, but the number of bacteria present can be altered. The following methods can be used to decrease the number of bacteria and minimize caries:

		Brushing.
		Flossing.
		Professional dental cleanings to physically remove plaque.
		Fluoride use. (See Chapter 6: Fluoride)
		Chlorhexidine mouthrinses and Xylitol: A crystalline alcohol C5H12O5 that is a derivative of xylose, used as a sweetener. Xylitol use.

S mutans is transmitted from the primary caregiver to infant by saliva, with earlier colonization increasing a child’s risk for caries. Transmission rates increase when parents participate in the following activities:

		Allowing a child to place their fingers into an adult's mouth. (They will go back into the child's mouth.)
		Sharing utensils or toothbrushes.
		Tasting the infant’s food or drink before serving it.
		“Cleaning” a dropped pacifier with saliva.