A functional appliance is a device designed to alter the relationship between the upper jaw and the lower jaw. It is best used on patients whose bones are still growing, thus taking advantage of the relative immaturity of these bones. These appliances are custom-made and specifically designed to realign the jaws so that they are in good relation to each other and ultimately allow the teeth to fit together in a proper bite.

The Frankel appliance is removable – it can therefore be removed when eating. The Frankel works best when left in place 20 to 24 hours a day to take advantage of the slow growth that occurs within bones.

If worn properly, the Frankel appliance will provide proper dental function and good facial balance. This appliance is almost always used prior to conventional orthodontic appliances.