It is a fixed or removable orthodontic appliance that will be fixed to the upper back molars and placed on the palate to expand it and widen the upper jaw, the appliance is generally worn for several months to correct the problem.
 

When Palatal Expansion Appliance is Needed?

Palatal expansion appliance is used when the upper jaw is narrow and there is no space for the teeth to erupt ,in this case the expander will help avoiding teeth extraction by expanding the palate and creating more space for the teeth to align together, other cases that this appliance is used to correct crossbite cases.