What does the expander do?
An expander is an appliance designed to widen the upper jaw. It is used when necessary as part of orthodontic treatment in order to correct a narrow upper jaw, crossbite, or to accommodate more teeth in the mouth.
What makes up an expander?
An expander is attached to the teeth by bands, these fit around the molars. The expansion screw is what widens as the screw is turned. This part stretches across the width of the mouth and connects the bands. As the screw is turned, pressure is placed on the teeth with bands and this force translates to the upper jaw. Sometimes there are arms on both sides of the expander that reach forward and apply pressure to other teeth as well.
How does it work?
An expander is usually placed no earlier then age 7 and no later than age 11 or 12. This is because the upper jaw is still malleable at this age to adapt quickly to orthodontic treatment. With each turn of the screw, the appliance widens 1/4 of a millimeter. When it is turned every day for a month, totaling 7 mm, this creates enough pressure to widen the upper jaw but is slow enough that the tissues can adapt to the changes without great discomfort to the patient.
Here is a patient treated with an expander for the first 6 months of her treatment. Braces were placed after two months. She initially had a narrow upper jaw causing a crossbite on the left. The crossbite was resolved after 3 months of expansion. The expander was left in place for an additional 3 months in order to maintain the result and allow the tissues to adapt to their new position.