A normal bite is when the teeth on the top jaw generally sit just over the bottom teeth. When the back teeth, or molars, sit in back of the bottom molars when the jaw is closed, dentists usually call it a posterior crossbite. The problem can be on one side or both sides of the mouth. It sometimes involves one tooth, but more than one or all of them can be affected. Orthodontists can correct the problem with braces, removable devices called retainers, or with implantable devices that spread the palate bones to a normal position.
With a posterior crossbite, the entire row of top teeth, called the dental arch, is typically arranged in a V shape instead of a U. It is generally referred to as a unilateral crossbite if it occurs on one side and a bilateral crossbite if both sides are affected. Children and adults can develop a posterior crossbite and usually, the sooner it is treated the better. Serious dental problems can result if this condition isn’t corrected, so early treatment can be an important preventative measure.
Teeth can wear down much faster if there is a posterior crossbite. Misalignment of the posterior teeth sometimes leads to gum disease, loss of bone around the roots of teeth, and even abnormal jaw development. People can develop chewing patterns that are abnormal as well. There are various causes for posterior crossbite, but it sometimes develops from thumb or pacifier sucking, restricted airways, and genetic reasons. The bite pattern generally does not return to a normal bite if it is not treated by an orthodontist.
To correct posterior crossbite, there are different kinds of orthodontic treatments. Braces are sometimes used to fix the bite. Appliances such as retainers are often used to move the back teeth into the right position. These are typically removable, but sometimes a surgically implanted device is used to expand the palate. The palate can be pushed apart when a screw is turned, and the separated bones usually grow together once they are repositioned.
There are also spring-loaded, fixed devices that usually do not require adjustment during the treatment. In clinical studies, when a posterior crossbite of baby teeth is treated, it is generally less likely that the problem will happen with the adult set of teeth. The choice of treatment typically does not affect the outcome. Some patients, however, can require more aggressive procedures than others.