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Are Cavities Contagious from Mom to Baby?


By Alice Callahan,

You’ve heard the warning before: Don’t share saliva with your baby. No sharing utensils, food, or toothbrushes. No “cutting” grapes in half with your own teeth. No cleaning the crud off the corner of her mouth with a little spit on your finger. No blowing on your baby’s hot food or tasting it yourself first. All of these things can spread mama’s saliva to baby and infect her mouth with cavity-causing bacteria.

I’ve heard these warnings, but all I can say is, “Seriously?” In my mind, a little saliva-sharing between mom and baby is unavoidable. I have tried. It wasn’t too difficult for the first few months of BabyC’s life, but then she started fish-hooking my mouth with her finger while she nursed, and it’s been down hill over since.

So what’s the deal? Are cavities contagious? If so, what can we do about it?

Bacteria that colonize the mouth cause cavities, or dental caries. Mutans streptococci (MS) are the most common bacteria implicated, but several other species are also associated with caries. The bacteria consume food particles, particularly sugar and starch, and produce acid, which causes demineralization of the tooth.

We aren’t born with bacteria-infested mouths – we have to be infected. Cavities are contagious in the sense that MS can be passed from mom’s saliva to baby’s mouth, where they quickly set up shop. MS is detected in some infants within the first few months of life, even before their first teeth erupt, and studies conducted in the 1980’s identified mom as the primary source of bacterial colonization in an infant’s mouth. Of course, you’ve got to wonder if a bit of colonization blame has shifted towards fathers or other caregivers since the 80’s, since fathers are sharing more of the balance of childcare these days.

Studies have also shown that children colonized with MS earlier in life have a greater risk of cavities in childhood. For example, Kohler et al studied 78 Swedish children, beginning at 15 months and continuing until age four. Of the children that were colonized with MS at two years of age, a full 89% had cavities by the time they were four. Among the children infected between ages three and four, only 36% had cavities at age four. Preventing or even just delaying colonization may protect children from later tooth decay, since soft baby teeth are extra-susceptible to decay in the first few years of life. Plus, I’m guessing (hoping) that dental hygiene becomes easier and more effective as kids get older.

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