If you want your babies to have perfect smiles breastfeed them, Italian research suggests.
Another good reason to breastfeed
Babies who were bottle-fed and had sucked their thumb or a dummy were twice as likely to have crooked milk teeth as breastfed infants.
Breastfeeding appeared to protect against thumb and dummy sucking damage, possibly down to its affect on mouth and palate muscle development.
The University of Milan findings appear in Archives of Disease in Childhood.
The sucking mechanism for breast and bottle feeding is different.
Babies who breastfeed draw milk up by squeezing the lips and tongue rather than sucking.
In comparison, babies feeding from a bottle use the tongue with a piston-like motion to compress the artificial teat against the palate.
This results in a more powerful sucking activity of the lips and cheeks.
The authors believe this might affect the development of the muscles of the mouth and palate in some way, which in turn could affect how the teeth and jaw align.
Although milk teeth will be replaced, the positioning and spacing of these teeth is increasingly thought to be crucial for correct jaw alignment and positioning of permanent teeth.
Of the 1,099 children aged 3-5 years studied, over a third of the children had misalignments and poor spacing, called altered occlusion when examined by a dentist.
The front teeth of one in eight (13%) children didn't touch, a condition known as anterior open bite.
And 7% had "posterior cross bite" when the top back teeth bite inside the bottom back teeth.
Children who sucked on dummies or thumbs for more than the first year of life were twice as likely to have misalignment as those who did not.
They were four times as likely to have open bite.
Breast or bottle?
How the children were fed in the first few months of their lives had no impact on the development of open bite.
But posterior cross bite was significantly more common in children who were bottle fed, as well as in those who sucked on dummies or thumbs past their first birthday.
Breastfeeding seemed to protect against the development of posterior cross bite, even when children sucked on dummies or thumbs.
The authors said: "The evidence suggests that while open bite spontaneously resolves once children stop sucking on pacifiers or thumbs, posterior cross bite persists."
Rosie Dodds from the National Childbirth Trust said: "This may be helpful information for parents unsure how useful it is to reduce the use of a dummy as the child gets older."
A spokeswoman for the British Dental Association said: "The nutritional benefits of breast-feeding are well-documented and this new research suggests that there may be a dental benefit too.
"The British Dental Association has long recommended to parents that they limit their reliance on dummies to calm children down, as they may introduce bacteria into the mouth.
"We also advise them to stick to milk or water in feeding bottles. Even fruit juice, despite its other health benefits, can damage children's teeth due to the high acid content."