Casting and impressions are techniques commonly used in healthcare to create a replica of a body part or surface. Casting involves the use of a moldable material such as plaster or fiberglass, which is applied directly to the body part being treated. The material hardens and is then removed, leaving a negative impression that can be used to create a positive model or brace. Impressions, on the other hand, involve the use of a material such as alginate or silicone that is applied to a body part or surface and then removed once it has set. The resulting impression can be used to create a custom-fitted device or to diagnose certain medical conditions. Both casting and impressions are important tools in healthcare, used for a variety of purposes including the diagnosis and treatment of orthopedic injuries and the creation of prosthetic devices.