Materials

Question 1

What is alginate?

Answer 1

Alginate is a material that is used to take dental impressions. Irreversible Hydrocolloid impression material.

Question 2

Alginate constituents

Answer 2

PACS - CAPS

• Potassium alginate
• Calcium sulphate
• Sodium phosphate
• Potassium sulphate
• Ammonium salts and chlorhexidine
• Glycols
• Diatomaceous earth or other fillers

Question 3

What do you look for in your alginate impression for a good study model?

Answer 3

• Clear well-defined teeth and soft tissues.
• No air blows
• No drag marks
• Impression material adhered to the impression tray
• Full dental arch

Question 4

Why is a wax bite important?

Answer 4

This will be used to occlude the models in the correct position prior to
trimming study models (gnatho statically trimmed)

Question 5

Describe the laboratory stages for the casting of orthodontic study models?

Answer 5

• Ensure that the impressions are clean of debris and disinfected
• Check the lab ticket for the prescription and the insisal relationship (depending if it is CIII or CII will determine on the initial basing of the impressions)
• Dry the impression and write on it an identifying marker (initials / study
model number) that will transfer onto the model.
• Mix crystacal R plaster with water in a vacuum mixer
• Pour into impressions using a vibrating plate to remove any air bubbles
• Turn them onto a plaster base.
• Once set place the wax bite between them and trim to the correct angles
• Smooth any ridges and label