CTO Orthotic Materials & Fabrication Techniques 2

Question 1

Which thermoplastic material is most appropriate for fabricating a rigid ankle-foot orthosis (AFO) requiring high durability and resistance to deformation under load?

Accepted Answer

Polypropylene

Answer

Polypropylene is the standard rigid thermoplastic for AFOs due to its high durability, stiffness, and resistance to deformation under body weight.

Question 2

When using a heat gun during thermoplastic molding, what is the primary risk if the material is overheated?

Accepted Answer

The material may bubble, thin unevenly, or burn

Answer

Overheating thermoplastic can cause bubbling, uneven thinning, and burning, compromising structural integrity.

Question 3

Which type of orthotic padding is best suited for accommodating a bony prominence to relieve focal pressure?

Accepted Answer

Closed-cell polyethylene foam

Answer

Closed-cell polyethylene foam (e.g., Plastazote) is preferred for accommodating bony prominences because it conforms and does not bottom out as quickly as open-cell foam.

Question 4

In lamination fabrication, what is the purpose of the PVA (polyvinyl alcohol) bag used during the process?

Accepted Answer

To create a vacuum-sealed barrier between resin and stockinette

Answer

The PVA bag creates an airtight barrier that prevents resin from contaminating the vacuum pump and ensures even resin distribution.

Question 5

Which rivet type is most commonly used when permanently joining two rigid thermoplastic components in orthotics?

Accepted Answer

Pop (blind) rivet

Answer

Pop (blind) rivets are most commonly used in orthotics because they can be installed from one side without access to the back of the joint.

(CTO) Certified Orthotic Technician Practice Test

(CTO) Certified Orthotic Technician Practice Test

CTO Orthotic Materials & Fabrication Techniques 2