How are custom/prescription orthotics made?

While orthotics can be made by several different processes, most experts recommend the use of a plaster cast or a foam impression of the patient's feet. This is called a negative impression. The cast is then sent to a laboratory with a prescription of recommended modifications. At the lab, a positive cast is made by pouring plaster into the negative cast. When this dries it forms a perfect reproduction of the bottom of the foot. Using the Chiropractor's recommendations for correction, the lab technicians custom mold the orthotics that incorporate the necessary adjustments.