The bacteria that cause tooth decay can be transmitted:
From an adult to a baby
Between 2 toddlers
At birth, the mouth of a baby does not contain the bacteria that cause tooth decay. However, bacteria can get into the baby’s mouth through food or objects contaminated by other people’s saliva.
As an adult, you can take certain precautions to avoid transmission of bacteria, including the following:
Kissing a baby on the lips
Using the same spoon to taste the baby’s food and then to feed them
Putting the baby’s pacifier in your mouth to clean it