Silicone Materials & Color Matching Flashcards

Which Shore hardness range is most appropriate for a nasal tip prosthesis requiring natural tissue compliance?

Answer: Shore A 20-35

Shore A 20-35 provides natural tissue compliance for nasal prostheses, balancing softness for comfort with durability for edge integrity.

What causes silicone prostheses to develop a sticky surface texture after prolonged wear?

Answer: Oxidative degradation and extraction of low-molecular-weight siloxane species

Oxidative degradation and migration of low-molecular-weight siloxane oligomers to the surface create tackiness in aged prostheses.

When performing color correction on a silicone prosthesis that appears too yellow under natural daylight, which pigment addition is most appropriate?

Answer: Add a small amount of violet/purple to neutralize yellow

Violet/purple is the complementary color to yellow, so adding a small amount neutralizes excessive yellow without dramatically altering the overall tone.

Thixotropic additives are sometimes incorporated into silicone formulations for anaplastology. What is their primary function?

Answer: Increase silicone viscosity to prevent sagging during fabrication

Thixotropic agents increase viscosity at rest to prevent material migration during mold filling and curing, especially for complex anatomical geometries.

A patient with Fitzpatrick Type VI skin tone requires prosthetic matching. Which pigment combination best approximates deep brown-black skin tones?

Answer: Burnt umber, raw umber, and small amounts of black with deep red

Deep skin tones in Type VI patients are best approximated with earth pigments (burnt/raw umber) combined with deep red and minimal black to achieve natural warmth.

What is the clinical significance of the 'pot life' specification for two-component silicone systems?

Answer: It specifies the working time available after mixing before viscosity increases prevent proper mold filling

Pot life is the window after mixing during which the silicone remains workable; exceeding it results in incomplete mold adaptation and prosthesis defects.

For an orbital prosthesis, which silicone characteristic is most important to minimize patient discomfort around the sensitive periorbital tissue?

Answer: Low durometer (softness) and biocompatibility

Low durometer silicone minimizes pressure and irritation on sensitive periorbital skin, while biocompatibility ensures no adverse tissue reactions.