Gypsum products Flashcards
Types of Gypsum
Types I, II, III, IV, V.
Type I Gypsum
Impression plaster
Type II Gypsum
Model plaster / dental plaster
Type III Gypsum
Dental stone
Hydro cal
Class I stone
Type IV Gypsum
Class II Dental stone
Improved dental stone
Densite
High strength dental stone
Type V Gypsum
- Dental stone with high strength and high expansion
- Extra hard, improved dental stone
W/P Ratio for Impression plaster
0.5 - 0.75
W/P Ratio for Gypsum type II
0.45 - 0.50
W/P Ratio for hydro cal
0.28 - 0.30
W/P Ratio for densite
0.22 - 0.24
W/P Ratio for extra hard, improved dental stone
0.18 - 0.22
Setting time - Gypsum type I
4 - 5 minutes
Setting time - Gypsum types II, III, IV, V
12 - 15 minutes
Setting expansion for impression plaster
0.15%
Setting expansion for model plaster
0.30%
Setting expansion for Class I stone
0.20%
Setting expansion for high strength dental stone
0.10%
Setting expansion for dental stone with high strength and high expansion
0.30%
Compressive strength of impression plaster
800 psi
Compressive strength of dental plaster
1300 psi
Compressive strength of dental stone
3000 psi
Compressive strength of Class II Dental stone
5000 psi
Compressive strength of Extra hard, improved dental stone
7000 psi
Uses of impression plaster
- Final wash impressions
2. Mucostic impression technique
Use of model plaster
To fill the flask in denture construction
Use of hydro cal
Construction of casts
Use of improved dental stone
Die material
Use of extra hard, improved dental stone
Improved die material
