Expansion

Rapid Maxillary Expansion (RME) is the widening of the maxilla(upper jaw) by controlled stretching of the midpalatal suture (the soft connection between the two halves of the upper jaw), which is then returned to normal through the formation of new bone.

RME is needed when the maxilla is narrow compared to the mandible (lower jaw). Usually this presents as a posterior crossbite. Teeth are in crossbite when the lower teeth overlap the upper teeth. There are two important exceptions caused by tipping of the teeth: 1)  there is no crossbite present even though a RME is needed.  2) a crossbite is present even though RME is not indicated.

Tipping of the teeth can be evaluated clinically, but it is more precisely evaluated with digital study models that allow viewing and measuring in infinite ways. Once tipping has been taken into account, the amount of expansion needed can also be calculated by measuring the virtual study models.

Rapid Maxillary Expansion (RME) is the widening of the maxilla(upper jaw) by controlled stretching of the midpalatal suture (the soft connection between the two halves of the upper jaw), which is then returned to normal through the formation of new bone.

RME is needed when the maxilla is narrow compared to the mandible (lower jaw). Usually this presents as a posterior crossbite. Teeth are in crossbite when the lower teeth overlap the upper teeth. There are two important exceptions. 1) When the maxillary posteriors are tipped buccally and/or the mandibular posteriors are tipped lingually, a crossbite may not be present even though a TMMI exists and RME is indicated.  2) When the maxillary posteriors are tipped palatally and/or the mandibular posteriors are tipped buccally a crossbite may be present even though a TMMI does not exist and RME is not indicated.

Tipping of the teeth can be evaluated clinically, but it is more precisely evaluated with digital study models that allow viewing and measuring in infinite ways. Once tipping has been taken into account, the amount of expansion needed can also be calculated by measuring the virtual study models.

Several appliances are available for expansion.  The Rapid Palatal Expander (RPE) or “Hyrax” appliance is the most precise with the fewest potential complications. The RPE, when used correctly, is one of the most effective and predictable orthodontic appliances available. When fabricated properly it is also the appliance most easily tolerated by patients.

Once the first molars have grown in, distance between them doesn’t change.  Failure to expand where indicated will prevent correct occlusion and cause uneven jaw growth that can only be corrected with surgery as an adult. 

While expansion has the “bonus” effect of improving “crowding”, it should not be used as a treatment for crowding in the absence of a narrow upper jaw. This would result in the creation of a malocclusion.

Recently two other “bonus” benefits of RME have been identified.  In patients with conductive hearing loss, RME was 100% effective in improving hearing.  More puzzling was the effect on patients with nocturnal enuresis or “bedwetting”.  Patients who had RME were 50% more likely to exhibit improvement as compared to a control group.

While all patients with crossbite should have an orthodontic consultation, it is more prudent to for all children to have an orthodontic evaluation by 7 or 8 years of age.Several appliances are available for expansion.  The Rapid Palatal Expander (RPE) or “Hyrax” appliance is the appliance taht I prefer. It is the most precise with the fewest potential complications. The RPE, when used correctly, is one of the most effective and predictable orthodontic appliances available. When fabricated properly it is also the appliance most easily tolerated by patients.

Once the first molars have grown in, the distance between them doesn’t change.  Failure to expand where indicated will prevent correct occlusion and cause uneven jaw growth that can only be corrected with surgery as an adult. 

While expansion has the “bonus” effect of improving “crowding”, it should not be used as a treatment for crowding in the absence of a narrow upper jaw. This would result in the creation of a malocclusion.

Recently two other “bonus” benefits of RME have been identified.  In patients with conductive hearing loss, RME was 100% effective in improving hearing.  More puzzling was the effect on patients with nocturnal enuresis or “bedwetting”.  Patients who had RME were 50% more likely to exhibit improvement as compared to a control group.

While all patients with crossbite should have an orthodontic consultation, it is more prudent to for all children to have an orthodontic evaluation by 7 or 8 years of age.

Dr Frank R. Egan

www.TeethOnTheMove.com