A cast is a rigid dressing used to protect an injured body part, and keep it from moving. It is used with a fracture or dislocation. There are two major types of cast materials, plaster and fiberglass.
Plaster is inexpensive and easy to use, but can be fragile.
It can fall apart if it gets wet. It may require additional applications if it weakens or starts to fall apart. Fiberglass casts are made of synthetic material, which is more expensive than the plaster cast. However, fiberglass casts are stronger and lighter. They tend to dry more quickly and, if they get wet, do not fall apart.