How is an orthodontic chin cup fitted?

An orthodontic chin cup is an extraoral (outside of the mouth) appliance. The appliance is used to effect an orthopedic (skeletal) change in the relationship between the upper and lower jaws. Young patients that have a larger than normal mandible (lower jaw) will usually present with an "underbite" and possibly a slightly concave profile. When the lower jaw is growing at a much faster rate than the upper jaw an orthopedic appliance like a chin cup is used to help reduce its rate of growth.

The appliance has a chin cup that is pre-made for a child, usually around the age of 7-9. The cup is then attached to straps that go up and over the crown of the head. Between the straps on the crown and the chin cup are elastic or metal coils that place a traction force on the chin cup both up and back. The force used is usually between 150-400 grams per side. This force, both up and back, has been shown to restrict the growth of the mandible (lower jaw). As the lower jaw growth is restricted, the upper jaw is allowed to grow normally and "catch up" with the lower jaw, and thus correct the discrepancy between the upper and lower jaw. The amount of force used must be titrated for each individual patient. The force should feel tight, and might produce slight discomfort, but should not create any pain.