Prosthetic Fabrication & Fitting Flashcards

During the color-matching process for a silicone prosthesis, metamerism refers to:

Answer: A color match that appears accurate under one light source but mismatches under another

Metamerism occurs when two color samples match under one illuminant (e.g., daylight) but not another (e.g., incandescent), making multi-light evaluation essential in prosthetic color matching.

A substructure (internal framework) made of acrylic resin is sometimes incorporated into a large auricular silicone prosthesis primarily to:

Answer: Provide rigidity and maintain the prosthetic shape against distortion during wear

Large silicone prostheses can distort under their own weight or patient handling; a rigid internal acrylic substructure preserves anatomical contours during daily use.

In craniofacial anaplastology, the term 'undercut' in mold making refers to:

Answer: A concave area in the impression or model that would trap a rigid mold material and prevent removal

Undercuts are geometric concavities where rigid mold material would lock, requiring blocking out with wax or using flexible impression materials before pouring stone.

Skin adhesives used for extra-oral prosthesis retention are most commonly tested for biocompatibility according to:

Answer: ISO 10993 biological evaluation standards for medical devices

ISO 10993 provides the framework for biological safety testing — including cytotoxicity, sensitization, and irritation — for materials that contact skin or tissue.

When fabricating a nasal prosthesis, the columella is sculpted to ensure that:

Answer: The central septum-like projection aligns with the philtrum and upper lip midline for natural aesthetics

The columella provides midline orientation and facial balance; misalignment creates an obvious deviation from the philtrum that undermines the aesthetic result.

Platinum silicone mixed at an incorrect base-to-catalyst ratio (e.g., too little catalyst) will typically result in:

Answer: A permanently tacky or incompletely cured silicone mass

Insufficient platinum catalyst leaves unreacted silicone polymer chains, producing a surface that remains sticky and a bulk that lacks adequate mechanical properties.

A pressure pot is used during silicone processing primarily to:

Answer: Compress air bubbles introduced during mixing so they become microscopic and invisible

Pressurizing the mold (typically 15–20 psi) compresses residual air voids to a size invisible to the naked eye, eliminating surface and internal porosity in the cured prosthesis.