Babies who suck their thumbs or use pacifiers are more likely to grow up with crooked teeth. But breastfed babies may be more likely to develop a nicer smile.

Domenico Viggiano, MD, and colleagues studied about 1,000 preschool children aged 3-5 in the southern Italian town of Cava de’ Tirreni. The kids had all participated in an oral health study organized by the local school.

Data included how the children were fed during their first three months of life and whether any children had used pacifiers or sucked their thumbs for more than one year, which the researchers call “non-nutritive sucking.”

A dentist examined all the children’s teeth to flag any flaws in their mouths.

The researchers found that breastfeeding appeared to have a “protective effect” against posterior cross-bite, which occurs when the top back teeth bite inside the bottom back teeth.

Bottle-fed children accounted for 11 percent of cross-bite cases, compared with 4 percent of breastfed kids.

Non-nutritive sucking may have exaggerated the problem.

Bottle-fed children who had also sucked their thumbs or used pacifiers made up 13 percent of posterior cross-bite cases. Five percent of kids with posterior cross-bite were breastfed children who had sucked their thumbs or used pacifiers.

Pacifiers and thumb sucking were linked to two other baby teeth problems.

A third of all participants had malocclusion, meaning the teeth are not lined up properly. Those who had used pacifiers or sucked their thumbs were twice as likely to have malocclusion as those who did not.

In addition, 89 percent of children with anterior open bite (when the front teeth do not touch) had been thumb suckers or pacifier users, write the researchers in the December issue of the journal Archives of Disease in Childhood.

The type of feeding didn’t affect open bite and was less important in malocclusion, say Viggiano and colleagues.

Baby teeth eventually fall out, but it’s believed they set the pattern for adult teeth. The different actions required for breastfeeding and bottle use could affect development of the mouth and face, say the researchers.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Viggiano, D. Archives of Disease in Childhood, December 2004; vol 89: pp 1121-1123. News release, BMJ Specialist Journals.