Alginate and Pouring Impressions

Question 1

What is alginate?

Answer 1

irreversible hydrocholloid

Question 2

What is alginate used for in clinics?

Answer 2

• recording accurate impressions
• of teeth and tissue

Question 3

For record impressions, two key points

Answer 3

• appropriate selection of stock trays
• follow manufacturers instructions for mixing and using alginate

Question 4

How to check an impression?

Answer 4

• check for no unsupported overhangs
• extend tray with greenstick if suitable larger tray is unavailable

Question 5

Protocol for once impression is done

Answer 5

• disinfection protocol
• place impressions with moist gauge in sealed bag
• with the prescription requesting study models

Question 6

What happens to impressions on arrival at the lab?

Answer 6

• inspected for accuracy
• washed

Question 7

Explain syneresis

Answer 7

• impressions shouldn’t be let to dry out
• it causes shrinkage

Question 8

Explain imbibition

Answer 8

• impressions shouldn’t be stored in excess moisture
• can cause expansion

Question 9

What is done with unsupported overhangs?

Answer 9

• trimmed away
• to prevent distortion when pouring

Question 10

Explain technical pouring of alginate

Answer 10

• dental stone (Kaffir D) mixed in 3:1 ratio with cold water and vibrated into impressions
• impressions filled to excess
• left to set
• models based with dental plaster 2:1 ratio and left to set

Question 11

What happens when alginate removed?

Answer 11

• placed in clinical waste
• models are trimmed
• occlusion checked - remove blips and ensure teeth occlude