By Amy Norton
New York - Nasal allergies, bottle-feeding and thumb-sucking may all contribute to certain types of tooth misalignments in young children, a study shows.
In a study of nearly 1 200 children between the ages of 4 and 5, Mexican researchers found that those who were bottle-fed, used pacifiers or sucked their thumb before the age of 1 were more likely to have a posterior crossbite - where the upper teeth in the back of the mouth bite down behind, rather than in front of, the lower teeth.
Similarly, children with nasal allergies were more likely to develop an open bite, in which the top and bottom teeth in the front of the mouth do not connect when the jaw closes.
Many studies have linked bottle-feeding, pacifier use and thumb-sucking to teeth misalignments, but the evidence regarding allergies has been mixed.
The new findings suggest that all of these factors contribute to teeth misalignment, though only certain types, according to the study authors, led by Dr Francisco Vazquez-Nava of the Autonomous University of Tamaulipas.
They report the results in the journal Archives of Disease in Childhood.
When babies suck on bottles, pacifiers or their fingers, the muscles of the head and face move differently than they do when breast-feeding. This could hinder the "harmonious" development of the jaw and hard palate, misaligning the baby teeth and possibly the permanent teeth, Vazquez-Nava explained.
In particular, he told Reuters Health, giving babies bottles and pacifiers early in life, and continuing to do so beyond the first year, may interfere with normal development of the dental structures.
Research suggests that about two-thirds of children who suck their thumbs or use pacifiers for at least four months in their first year of life have some form of dental misalignment, Vazquez-Nava said.
With nasal allergies, the misalignment may stem from the tendency of children to chronically breathe with their mouths open and to move the tongue along the roof of the mouth to relieve itching.
The risk of tooth misalignment is one more reason to diagnose and treat allergies sooner than later, Vazquez-Nava said.
SOURCE: Archives of Disease in Childhood, October 2006.