CCA Techniques & Materials 3 — Questions and Answers
Question 1: Which polymerization method produces the least dimensional shrinkage when fabricating a hard acrylic prosthetic base?
- Cold-cure (self-curing) acrylic
- Heat-cured acrylic under pressure (Correct answer)
- Microwave-cured acrylic
- UV-cured resin
Correct answer: Heat-cured acrylic under pressure
Heat-curing under pressure (e.g., in a hydraulic press) minimizes porosity and shrinkage compared to cold-cure systems, yielding more dimensionally stable prosthetics.
Question 2: When color-matching a facial prosthesis under natural daylight conditions, which phenomenon must the anaplastologist account for?
- Fluorescence
- Metameric mismatch (metamerism) (Correct answer)
- Diffraction
- Polarization
Correct answer: Metameric mismatch (metamerism)
Metamerism means two colors that appear identical under one light source (e.g., fluorescent) may look different under daylight, requiring matching under multiple illuminants.
Question 3: In the lost-wax casting process for anaplastology, what happens to the wax pattern after the mold investment material sets?
- It is removed by mechanical scraping
- It is eliminated by heating (burnout), leaving a void for the prosthetic material (Correct answer)
- It is left in place as a structural core
- It is dissolved with acetone before investing
Correct answer: It is eliminated by heating (burnout), leaving a void for the prosthetic material
The lost-wax technique involves burning out (eliminating) the wax pattern in a furnace, leaving a precise negative space into which the final material is injected or packed.
Question 4: Which property of medical-grade platinum-cure silicone makes it preferable over tin-cure silicone for ear and nose prostheses?
- Lower material cost
- Minimal shrinkage and improved long-term stability (Correct answer)
- Faster surface cure
- Greater opacity
Correct answer: Minimal shrinkage and improved long-term stability
Platinum-cure (addition-cure) silicone exhibits virtually no by-product off-gassing and very low shrinkage, producing more dimensionally accurate and durable prostheses.
Question 5: When using bar-retained osseointegrated implants for a nasal prosthesis, the bar framework is fabricated from which material?
- Flexible vinyl
- Titanium or gold alloy (Correct answer)
- High-impact acrylic
- Carbon fiber composite
Correct answer: Titanium or gold alloy
Titanium or gold-alloy bars are milled or cast to connect implant abutments, providing a rigid, biocompatible superstructure for the nasal prosthesis retention system.
Question 6: Which technique allows the anaplastologist to characterize blood vessel details (telangiectasia) on a silicone prosthesis surface?
- Sandblasting with fine alumina
- Painting fine red/blue threads with diluted silicone pigments (Correct answer)
- Immersion dyeing in pigment bath
- Acid etching
Correct answer: Painting fine red/blue threads with diluted silicone pigments
Fine synthetic fibers or capillary-fine brush strokes of tinted silicone are applied to the prosthesis surface or embedded near the margin to simulate superficial vasculature.
Question 7: What is the function of a scleral impression for an ocular prosthesis patient?
- To create a mold of the external eyelid only
- To record the exact contour of the anophthalmic socket for a custom-fitted shell (Correct answer)
- To measure pupillary distance
- To determine iris color
Correct answer: To record the exact contour of the anophthalmic socket for a custom-fitted shell
A scleral impression captures the unique three-dimensional contour of the orbit and socket tissues, enabling fabrication of a custom prosthetic eye that fits precisely and moves naturally.
CCA Techniques & Materials 3
Which polymerization method produces the least dimensional shrinkage when fabricating a hard acrylic prosthetic base?