Alginate And Impressions Flashcards
What is an impression?
A negative reproduction of the dental structures
What are the constituents in of alginate?
- potassium alginate
- calcium sulphate
- sodium phosphate
- potassium sulphate
- glycols
- diatomaceous earth/fillers
- ammonium salts and chlorhexidine
What are the advantages of alginate?
- easy to use
- good surface detail
- low cost
- pleasant taste ?
- rapid set time
- sets relatively firm
- compatible with oral tissues
What are the disadvantages of alginate?
- tears easily
- poor dimensional stability
- poor test adhesion
- difficult to disinfect
- can distort easily
What is the ideal impression material?
- accuracy
- non tearing
- short setting time
- easy mix
- biocompatibility
- easy disinfection
- long shelf life
- pleasant taste
- cost effective
What must be checked after taking an impression?
- air blows
- drag
- adhesion to tray
- sulcus
- good definition
How is an impression disinfected?
- Rinse under cold water
- Immerse in hydrochloride 0.1% for 10 minutes
- Rinse under cold water
- Wrap impression in damp paper towel and place in bag
- Label bag to send to lab
Why does an alginate impression need to be wrapped in a damp paper towel?
The impression can fry out and distort
What is the process of taking an impression?
Take consent from the patient and explain the process
Position the patient and yourself
Check the tray size is appropriate
Mix the material and load the tray
Rotate loaded tray into patients mouth
Sit tray posterior then anterior- moving the lip out of the way - midline of tray and teeth must match
Muscle trim
Wait for material to set
Break seal in sulcus and carefully remove by rotating out the mouth
Check impression is good
What do you look for in a good alginate impression?
- good detail of all erupted teeth
- free of bubbles or voids
- extend past the last tooth in the arch
- have good external roll
- be symmetrical in the tray
- have a smooth surface
- no impression of the lips or tongue
- include the buccal sulcus and palate
- no tears or drags
Why is a wax bite important?
Allows the lac to know where the teeth occlude when trimming the models
What is a study model?
A positive reproduction of the dental structures
