CPO CPO Materials Science & Technology 1 — Questions and Answers
Question 1: Which thermoplastic material is most commonly used for low-temperature custom orthotic fabrication due to its workability at approximately 60–70°C?
- Polypropylene
- Low-temperature thermoplastic (e.g., Orfit, Aquaplast) (Correct answer)
- Carbon fiber composite
- Copolymer polyethylene
Correct answer: Low-temperature thermoplastic (e.g., Orfit, Aquaplast)
Low-temperature thermoplastics such as Orfit and Aquaplast soften at 60–70°C, allowing safe custom molding directly on or near the patient's body.
Question 2: Carbon fiber composite prosthetic components offer a primary advantage over aluminum components primarily because they:
- Are less expensive to manufacture
- Provide higher stiffness-to-weight ratio (Correct answer)
- Are easier to adjust in the clinic
- Offer greater corrosion resistance in aquatic environments
Correct answer: Provide higher stiffness-to-weight ratio
Carbon fiber composites provide a superior stiffness-to-weight ratio compared to aluminum, allowing stronger, lighter prosthetic components that reduce metabolic cost.
Question 3: When fabricating a total contact cast (TCC) for a diabetic foot ulcer, which property of plaster of Paris makes it preferred over fiberglass in some clinical protocols?
- Greater strength
- Faster curing time
- Conformability and ease of molding for precise total contact (Correct answer)
- Waterproof properties
Correct answer: Conformability and ease of molding for precise total contact
Plaster of Paris is more conformable than fiberglass, allowing the clinician to achieve true total contact that distributes plantar pressure more uniformly.
Question 4: Which material property describes a material's ability to return to its original shape after deformation, which is critical for prosthetic socket fit under cyclic loading?
- Plasticity
- Viscoelasticity
- Resilience / Elasticity (Correct answer)
- Creep resistance
Correct answer: Resilience / Elasticity
Elasticity (resilience) describes a material's ability to recover its original shape after deformation, essential for socket liners and flexible inner sockets that must maintain fit under repeated loading.
Question 5: Silicone suspension liners for transtibial prostheses primarily achieve suspension through which mechanism?
- Suction created by a one-way valve
- Pin-lock or lanyard engagement with the socket (Correct answer)
- Atmospheric pressure differential
- Friction between liner and socket wall
Correct answer: Pin-lock or lanyard engagement with the socket
Most silicone pin-lock liners achieve suspension via a distal metal pin that engages a ratchet lock mechanism within the prosthetic socket.
Question 6: What is the primary reason polyethylene foam (Plastazote) is used as an interface material in diabetic insoles?
- High durability and long service life
- Excellent energy return during push-off
- Closed-cell structure providing cushioning and pressure distribution (Correct answer)
- Anti-microbial properties preventing infection
Correct answer: Closed-cell structure providing cushioning and pressure distribution
Plastazote's closed-cell foam structure provides cushioning and conforms to foot shape, distributing plantar pressure to protect insensate diabetic feet from ulceration.
CPO CPO Materials Science & Technology 1
Which thermoplastic material is most commonly used for low-temperature custom orthotic fabrication due to its workability at approximately 60–70°C?