1. Modeling materials

2. Impression materials
Impression materials are used to make an accurate replica of the hard and soft tissues.
The impression gives a negative reproduction of the tissues.

4. 1.1 Definition What is the modeling materials?
Model material is a material with which we can fill the impression , a positive cast is made that can be removed after the model material has set.

6. 1.2 Classify of Gypsum products
1. Dental plaster 熟石膏
2. Dental stone 人造石
3. High-strength / low expansion
dental stone 高强度/低膨胀人造石
4. High-strength /high expansion
dental stone 高强度/高膨胀人造石

9. What is the Gypsum products?
生石膏 CaSO4. 2 H2O
The dihydrate form of calcium sulfate ,called gypsum, is usually white to milky yellowwish in color and is found in a compact mass in nature. Deposits of gypsum, however, are found in most countries.

10. 1. Dental plaster 熟石膏
2. Dental stone 人造石
3. High-strength dental stone
These 3 types have identical chemical formulas of calcium sulfate hemihydrate,CaSO4.1/2 H2O, but they posses different physical properties, which makes each of them suitable for a different dental purpose.

11. 2. Dental plaster 2.1 Manufacture dehydration by heat Gypsum Plaster
CaSO4. 2 H2O CaSO4. 1/2 H2O+ 11/2H2O
110~120°C
Gypsum Plaster

12. Manufacture of dental plaster, stone,and high-trength stone
dehydration
by heat or formulation
Mineral other means Plaster Model plaster
Gypsum Lab plaster
Hydrocal Dental stone
Densite High-strengt
dental stone

13. 2.2 Composition of plaster:
1) Calcium sulfate hemihydrate 75~85%
2) Gypsum (CaSO4.2H2O) ~8%
3) Calcium Sulfate (CaSO4) 5~8%
4) A few of other materials %

14. 2.3 Mechanism of Setting
CaSO4.1/2 H2O+11/2H2O
CaSO4.2H2O+3900cal/g.mol
The reaction is exothermic, and whenever 1 g mol of CaSO4.1/2 H2O is reacted with 1.5 g mol of water, 1 g mol of CaSO4.2H2O is formed, and calories of heat are developed.

15. 2.4 Properties
1) Control of Setting Time:
Atmosphere (water),
Temperature ,
Water/powder ratio,
Rate of mixing,
Time of mixing,
Accelerator and retarder

16. 2) Viscosity
High-strength dental stones
Impression plaster

17. 3) Compressive strength
4) Surface hardness and
abrasion resistance
5) Tensile strength
6) Reproduction of dental
7) Setting expansion

18. 2.5 Manipulation Mixing : 1. Using a metal spatula with a stiff blade
Using a hand-mechanical spatulator
1 minute / 2 revolutions per second
3. By a power-driven mechanical spatulator
20 seconds / low-speed drive

19. Pouring: vibration
Separated: 45~60 minutes
Disinfect the models: