Impression Techniques & Molding Flashcards
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Read the first 7 Impression Techniques & Molding flashcards as text
Which impression material is most appropriate for capturing fine surface detail on a hairless scalp area for a cranial prosthesis?
Answer: Vinyl polysiloxane (VPS)
Vinyl polysiloxane provides superior dimensional stability and captures fine detail with minimal distortion, making it ideal for cranial prosthetic impressions.
What is the primary reason a two-part (matrix and core) mold is used for complex auricular prostheses?
Answer: To allow removal of undercut areas without tearing the prosthesis
A two-part mold allows the anaplastologist to demold prostheses with undercuts without distortion or tearing of the silicone material.
When taking a facial impression for an orbital prosthesis, the patient's eye should be:
Answer: Closed with a protective conformer or gauze in place
A protective conformer or gauze shields the orbital cavity and remaining ocular structures from impression material during the procedure.
What does the term 'working time' refer to in the context of impression materials?
Answer: Time available to manipulate the material after mixing before it begins to set
Working time is the window during which the clinician can seat, adapt, and position the impression material before gelation or polymerization begins.
Which type of separator (release agent) is most commonly applied to stone or plaster molds before packing intrinsic silicone?
Answer: Silicone mold release spray
Silicone-specific mold release agents prevent adhesion between cured silicone and the mold surface without interfering with color or cure.
An impression of the nasal defect yields a distorted model. The most likely cause is:
Answer: Premature removal of the impression before adequate set
Removing an impression before it has fully set causes elastic rebound and permanent distortion of the recorded anatomy.
When fabricating a mold for a nasal prosthesis using Type III dental stone, what is the purpose of vibrating the stone during pour?
Answer: To eliminate air bubbles and ensure complete adaptation to surface detail
Vibration encourages entrapped air bubbles to rise and escape, producing a void-free stone model that accurately reproduces surface detail.