OCC Casting Materials & Techniques 2

Question 1

What is the primary chemical reaction that causes plaster of Paris to harden?

Accepted Answer

Hydration of calcium sulfate hemihydrate

Answer

Plaster of Paris hardens through hydration: calcium sulfate hemihydrate reacts with water to form calcium sulfate dihydrate (gypite).

Question 2

Which type of cast material is preferred when the patient requires MRI imaging during the treatment period?

Accepted Answer

Fiberglass with fiberglass splints

Answer

Fiberglass cast materials are MRI-compatible because they contain no ferromagnetic metals, making them safe in magnetic fields.

Question 3

When applying a short arm cast, the wrist should typically be positioned in how many degrees of dorsiflexion?

Accepted Answer

10–20 degrees

Answer

The wrist is typically positioned in 10–20 degrees of dorsiflexion for a functional short arm cast, allowing optimal hand function.

Question 4

What is the purpose of the 'ear' or 'window' cut into a cast?

Accepted Answer

To allow inspection or relieve pressure over a specific area

Answer

A cast window allows the clinician to inspect the underlying skin, relieve localized pressure, or access a wound beneath the cast.

Question 5

Fiberglass casting tape should be dipped in water at approximately what temperature for optimal working time?

Accepted Answer

Room temperature water (20–25°C)

Answer

Room temperature water is recommended for fiberglass tape to provide adequate working time; warm water accelerates the setting reaction.

(OCC) Orthopedic Casting Certification Practice Test