CCA Silicone Materials & Color Matching 2 — Questions and Answers
Question 1: Which platinum catalyst concentration is typically used to achieve a Shore A hardness of 25-35 for facial prostheses?
- 0.1% by weight
- 1-3% by weight (Correct answer)
- 10-15% by weight
- 25% by weight
Correct answer: 1-3% by weight
Platinum catalyst concentrations of 1-3% by weight are standard for achieving clinically appropriate Shore A hardness in facial prosthetics.
Question 2: What is the primary disadvantage of using cadmium-based pigments in silicone prostheses?
- They fade rapidly under UV exposure
- They are toxic and pose biocompatibility concerns (Correct answer)
- They cannot be dispersed in silicone base
- They cause premature vulcanization
Correct answer: They are toxic and pose biocompatibility concerns
Cadmium-based pigments are toxic and fail biocompatibility requirements, making them unsuitable for skin-contact prosthetic devices.
Question 3: A prosthesis appears orange-toned in fluorescent office lighting but matches skin in natural daylight. What phenomenon explains this?
- Simultaneous contrast
- Metamerism (Correct answer)
- Iridescence
- Bezold effect
Correct answer: Metamerism
Metamerism occurs when two colors appear to match under one light source but differ under another due to different spectral reflectance curves.
Question 4: Which silicone property is most critical for fabricating a thin-edged auricular prosthesis margin?
- High tear strength (Correct answer)
- Low viscosity
- High refractive index
- Low platinum content
Correct answer: High tear strength
High tear strength prevents thin feathered margins from tearing during placement and removal of auricular prostheses.
Question 5: When mixing intrinsic silicone colorants, which color is used to neutralize excessive redness in a prosthesis?
- Yellow
- Blue-green (Correct answer)
- Orange
- White
Correct answer: Blue-green
Blue-green is the complementary color to red on the color wheel and is used to neutralize excessive redness in silicone matching.
Question 6: Room-temperature vulcanizing (RTV) silicone differs from high-temperature vulcanizing (HTV) silicone primarily in that RTV:
- Requires an autoclave for curing
- Cures at ambient temperature using a condensation or addition reaction (Correct answer)
- Has superior UV resistance
- Cannot be pigmented
Correct answer: Cures at ambient temperature using a condensation or addition reaction
RTV silicones cure at room temperature via condensation or addition reactions, making them practical for clinical prosthetic fabrication without specialized equipment.
Question 7: Which property of silicone is described by its ability to return to original shape after deformation without permanent set?
- Plasticity
- Viscoelasticity
- Resilience (Correct answer)
- Creep resistance
Correct answer: Resilience
Resilience describes the ability of silicone elastomers to recover their original shape after elastic deformation, which is essential for prosthetic fit and function.
CCA Silicone Materials & Color Matching 2
Which platinum catalyst concentration is typically used to achieve a Shore A hardness of 25-35 for facial prostheses?