Impression Materials and Methods Flashcards
What is the purpose of retraction cord when taking impressions for a crown?
Used to push gum tissue away from the prepared margins of the tooth.
Soaked in astringant to minimise gingival bleeding.
What type of astringant should be used when taking impressions for a crown?
Ferric sulphate for metal
Aluminium chloride for porcelain to avoid staining
When taking impressions for a crown, what steps can be taken if retraction is inefective?
Give OHI and reappoint
Electrosurgery
Laser surgery
Gingivosurgery
Outline the steps for taking an impression of a crown prep?
Assess gingival condition
Select tray
Apply adhesive
Place retraction cord
Remove retraction cord
Assess gingiva
Wash and dry gingiva
Select light body silicon or medium body polyether
Take impression using one or two stage technique
Take bite registration using silicone bite reg paste
What is a one stage impression technique?
Light body silicone is placed on the prep, gingiva, and occlusal surfaces of all teeth in that arch.
A medium body silicone is placed over the top of this, and allowed to set.
What is a two stage impression technique?
Heavy body silicone is used with a spacer. It is allowed to set full and then removed.
Light body placed in prep, gingiva, and occlsual surfaces of all teeth. It is also placed into heavy body impression and reseated.
