Clinical failures Flashcards
rough or uneven impression surface
- incompletepolymerization
- improper mixing or ratio of components
- FOR ADDITION SILICON= surface agents like latex contaminate material and inhibit polymerization
- FOR CONDENSED SILICON= excessively high accelerator/base ratio with
bubbles
air incorporated when mixing
irregularly shaped voids
moisture or debris on surface of teeth
rough or chalky stone cast
- inadequate cleaning of impression
- excess water still present
- excess wetting agent still on impression
- premature removal of caste
- improper W/P ratio
- ADDITION SILICON= failure to delay pour for at least 20 minutes (so it doesn’t contain salt?)
distortion
*movement of tray during polymerization
*resin tray not aged sufficiently
*lack of adhesion of elastomer to tray
*excessive bulk of materiel used
*elastic properties develop in material before tray is set
*premature or improper removal of impression from mouth
delayed pouring of addition silicone or condensed silicon impression
*lack of mechanical retention to impression tray
Inadequate bulk causes what?
Tearing
Leaving case in impression too long causes what?
Rough or chalky cast
Having a too low W/P ratio causes?
Grainy material
Impression not poured immediately causes?
Distortion
Air incorporation during mixing causes?
Bubbles