Impression materials and digital impressions Flashcards
What is an impression
Negative record of the tissues of the mouth
It is used to reproduce the from of the teeth and surrounding tissues
Mode of setting elastic materials
Alginate, polysulfide, polyether, silicone
Chemical reaction (irreversible)
Mode of setting non elastic materials chemical
Impression plaster, zinc oxide Eugenol
Chemical reaction (irreversible)
Mode of setting elastic materials physical
Agar
Mode of setting non elastic physical
Impression compounds, impression waxes
Why does hydrophilicity matter for impression materials
Allows impression materials to capture accurate details in a moist environment, ensuring better adaptation to wet oral tissues and reducing the risk of voids or bubbles in the impression
Alginate dimensional stability
Short term stability, ideal for quick impressions
Water sensitive, can swell if exposed to water or shrink if allowed to dry out
What is dimensional stability
Ability of an impression material to maintain its shape and size over time after setting
Without experiencing distortion, shrinkage or expansion
Alginate tear strength
Moderate tear strength
Typically lower compared to elastomeric materials, which can make them less ideal for highly detailed impressions
Handling of alginate
Careful technique is required during removal to prevent tearing
Use a gentle rocking motion, to reduce stress on the material
What is tear strength
Ability of an impression material to resist tearing or rupture WHEN it is removed from the mouth
What is Alginate less suitable for
Precise restorations like crowns and bridges
Agar setting reaction
Cooling at 37-45
Heating at 70-100
Agar dimensional stability short term
High initial accuracy, excellent at fine details due to its low viscosity in the sol state
Agar dimensional stability long term
Poor
Syneresis: loss of water from the gel leadin to shrinkage
Inhibition: uptake of water causing expansion
