There are several kinds of expanders but the basic premise of a palatal expander is to widen or expand the upper jaw. This is accomplished by placing pressure on the maxillary (upper jaw) bones as directed by the orthodontist. The expansion of the maxilla is most predictably and effectively accomplished in a pre-pubescent child. At this age, the maxilla is two separate bones separated by a soft suture that runs along the middle of the palate. Expansion is easily accomplished with minimal discomfort. However, as a child reaches puberty, the soft suture begins to fill in with bone thus causing the maxilla to become one solid bone. Once this happens, palatal expansion becomes less predictable and often can only be accomplished with the help of an oral maxillofacial surgeon who can surgically split the maxilla. This is obviously not an ideal scenario and can all be avoided by treating a narrow maxilla at an early age.
The most common reason to treat with a palatal expander is for children who have a crossbite. A normal bite is when the upper teeth slightly overlap the lower teeth. A crossbite is diagnosed when a childs bite is reversed (when on one or both sides, the lower teeth overlap the upper teeth). Left untreated, a crossbite can result in many undesired problems: the lower jaw asymmetrically deviating to one side, frequent discomfort from biting on the inside of the cheek, excessive crowding/crooked upper teeth, and possibly TMJ disorders in adulthood. Another common reason to treat with an expander is when a child has moderate to severe dental crowding. In normal conditions, the majority of dental crowding is expressed in the front six teeth. The amount of crowding can often be diagnosed at an early age. Expansion is a great way to create space for the crowded adult teeth. This will often result in orthodontic treatment taking less time and also significantly reduce the possibility of having to extract adult premolar teeth to create space in the future.
Palatal expansion is usually not painful. A child may feel some pressure for a short period of time as it is being expanded. Usually the biggest issue is just getting use to it. Speech and eating may be affected for a few days but once acclimated, children dont even realize that it is in their mouths. The expansion process typically takes only a few weeks. It is then left in the mouth for several additional months to allow the maxilla to stabilize while bone grows into the soft suture.