What is a popular synthetic cast?

A synthetic cast is a lighter synthetic alternative to the conventional, good old plaster of Paris. Synthetic cast is made of fiber glass and is sometimes called glass fiber reinforced plastic (GFRP) or just  glass reinforced plastic (GRP). It consists of a plastic matrix reinforced by fine fibers of glass.

Why is it popular? 
1. It is three times stronger than plaster of Paris and only one third in weight.
2. It is more durable
3. It requires less maintenance
4. It comes in any colors and some doctors even let the patient choose their color.

Like its counterpart the plaster of Paris, fiberglass cast is applied in cases of fracture treatment but never applied in acute settings because it is less accommodating to swelling or where reduction of fragments call for molding. 
Therefore fiberglass casts are mostly used where the healing process has already began.

Answer: pathogensstep by step solution:

"observation" would be the correct answer