Kissing can transmit bacteria that promote tooth decay, such as Streptococcus mutans . The largest reservoir from which babies acquire this cariogenic microbe is from their parents, through mouth-to-mouth contact. Before the appearance of the first tooth, half of 6-month-old children have this streptococcus as a host in their mouth, and after one year they have already developed a considerable colony. The contagion can be delayed if the parents follow correct oral hygiene .
Something similar happens between adults. Intimate kissing increases the risk of a perforated tooth .





