Alginates

Question 1

What are three ways alginate can deform?

Answer 1

1. Syneresis - fluid loss from gel to surface (shrinkage)
2. Evaporation (shrinkage)
3. Imbibition - swelling if immersed in water (distortion/swelling)

Question 2

THREE advantages of alginates?

Answer 2

• Easy to use (simple to make and manipulate)
• Setting time can be manipulated
• Hydrophilic
• Relatively cheap

Question 3

THREE disadvantages of alginates?

Answer 3

• Surface detail not very high (records minimal details)
• Not dimensionally stable
• Cannot be poured more than once (single cast)

Question 4

What is the mixing, working and setting times of Halas Alginate used in ADH?

Answer 4

At room temp 23 degrees C:
> Mixing time (45 secs)
> Working time (1 min 45 secs - time to insert into mouth)
> Setting time (30 secs - time in mouth)
Total: 3 mins (purple to pink)

Question 5

TWO ways setting time of alginate impression material can be manipulated?

Answer 5

1. Water temp

2. W:P ratio

Question 6

What SEVEN intraoral features should we note before taking impressions?

Answer 6

• Dental arch (shape/size)
• Palatal vault shape/size (e.g. Tori/exostosis)
• Axial inclination
• Mobile teeth
• Implants
• Lip tightness
• Food debris

Question 7

What FIVE criteria do we use to critique alginates?

Answer 7

MSTAR:

• Mix (homogenous)
• Size (of tray)
• Time (set properly)
• Amount (over/underload)
• Removal (no drag marks)