A Rapid Palatal Expander (RPE) is an upper appliance that places pressure on the upper jaw (maxilla) by turning a midline screw. The pressure separates the mid palatal suture thus making the maxilla wider, which can correct crossbites and create space. RPEs are used often to correct posterior crossbites.
We can correct posterior crossbites as soon as we see them because we can obtain more room for other unerupted teeth. Also, a posterior crossbite, if it’s only on one side, can cause the lower jaw to grow asymmetrically to that side. Therefore, correction of a posterior crossbite helps prevent asymmetrical growth of the lower jaw.
Since we are separating a mid palatal suture, it is better to do this procedure at a younger age before the palatal suture becomes fused.
With adults, the maxilla can be expanded by using an RPE and having surgery performed by an oral surgeon. This procedure is called Surgically Assisted Rapid Palatal Expander (SARPE). During the surgery the palatal suture is opened with side releasing incisions and all the expansion is completed at one time. Some orthodontists will have the patient turn the expander after the surgery but most let the oral surgeon complete the task.