Dent 1.4 gypsum products Flashcards Preview

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Flashcards in Dent 1.4 gypsum products Deck (15):
1

The ________ is the basis for all gypsum used in dentistry

Hemihydrate

2

what is the gypsum rock

CaSO4-2H2O (calcium sulfate dyhydrate)

3

what three types of materials are derived from partial dehydration of gypsum rock

Plaster
Stone
High Strength Stone

4

List the final products of the following
1) Plaster
2) Hydrocal
3) densite

1) model lab
2) Dental stone
3) High strength stone

5

what three things Characterize Nucleated re-crystallization

1)Continuous solution of hemimydrate
2) diffusion of calcium and sulfate ions to nucleated centers
3) precipitation of microscopic gypsum crystals

6

Less water = _________

Less Porosity

7

Less porosity =

More strength

8

what causes thick mixes (low W/P ratio) to harden more quickly

Nucleated centers are concentrated in a smaller volume.
The interaction of growing solids occurs earlier and is more effective

9

decreased W/P = _________

denser cast

10

Increased W/P ratio = __________

decreased strength (more porosity)

11

Gypsom is used as a _______ in materials commonly employed in castin of dental _____ _____ and is generally not hated above 700 degrees celsius

Binder, Gold alloys

12

what provides expansion to compensate for gold shrinkage

Refractrory

13

what are two types of Binders

Calcuim sulfate hemihydrate (Gold)
Phosphate, ethyl silicate (high temp alloys)

14

what are the two phases that exist in Silica

Low temperature phase (Alpha)
High temperature phase (Beta)

15

within practical limits increasing amount of silica...(4)

1. increased manipulation time
2. Increased setting expansion
3. increased thermal expansion
4. Decreased compressive strength