Tooth decay is an infectious disease characterized by the progressive dissolution of the hard tissues of the tooth, due to the production of acid corrosive metabolites by some bacteria that inhabit the oral cavity.
With the close contact between the mouths of two people, for example with a kiss, it is therefore possible that the bacteria responsible for caries are transmitted from one person to another. In this regard, however, it must be considered that many microbial species abound in the mouth, of which only a few are harmful to the enamel. All these species form a sort of community, characterized by deep mutual interactions and mechanisms of cohabitation that are difficult to disturb. It should also be considered that the bacterial flora of the oral cavity is never the same between one individual and another, being strongly influenced by eating habits, the level of oral hygiene and hereditary factors. Therefore, it is unlikely (even if theoretically not impossible) that the balance of one's oral microflora is permanently altered by the simple contact with another person's saliva through a kiss.
The possibilities of contagion between mother and child are much more consistent. It has in fact been shown that often the bacterial strains found in the saliva of children are the same found in the saliva of their mothers. This led scholars to conclude that the main source of oral cavity infection by cariogenic bacteria is maternal saliva.
Given the profound correlation between the conditions of hygiene and oral health of mothers and the development of dental caries in their children, it would be appropriate for mothers to treat their oral hygiene scrupulously, especially in the first months and years of the child's life. In the case of cariorecjectivity of the parents (or of those who take care of the child such as the baby sitter or the grandparents) it would also be appropriate to avoid risky behaviors, such as the contact of the mouth directly on the baby's, the use of the same cutlery, drink from the bottle to check its temperature, clean the pacifier with its own mouth, etc.
