Done Dental Materials Ch. 9 Gypsum

Front 1

Study model

Back 1

Plan treatment and observe teeth

Front 2

Cast

Back 2

Restorations are febricated

Front 3

Die

Back 3

Model of a single tooth

Front 4

Gypsum

Back 4

Fine powders mixed with water to be poured and shaped into a mass

Front 5

Desirable properties

Back 5

Accuracy,Stability,

Reproduce fine detail,Strength to abrasion,

Compatibility with impression material,

Color,Biological safety,Easy,Cost

Front 6

What are gypsum products made of

Back 6

Gypsum rock that is ground into a fine powder and heated

Front 7

Calcination

Back 7

Heating gypsum and driving off part of the water of crystallization

Front 8

Plaster

Back 8

1st product

Grinding rock down and heating in open container

Pourous and irregular

Weak but cheap

Prelim casts and attaching to an articulator

White

Type II

Front 9

Articulator

Back 9

Simulated occlusion and mastication process.

Front 10

Stone

Back 10

Heated in a closed container with steam pressure.

More regular and less porous.

Stronger and more expensive than plaster

Makes casts for diagnostic purposes and casts for denture construction.

Light tan

Type III

Front 11

High strength or improved stone

Back 11

Calcined in a calcium chloride solution.

Very dense and cuboidal and reduced surface area.

Strongest and most expensive.

Makes casts and dies for crown bridge and inlay fabrication

Type IV

Front 12

Water/powder ratio

Back 12

Proportion of water to powder to make a workable mix

Plaster needs more

Stone needs some

Improved stone needs the least

Front 13

Working time or initial Setting time

Back 13

Length from start of mix until mass reaches semi hard stage.

Time for manipulating product

5-7 minutes

Front 14

Final settling time

Back 14

Length of tkme from start or mix until mass is completely hard and can be seperated from impression.

30-45 minutes

Front 15

To increase your setting time (slower)

Back 15

Less mixing

Higher water/powder ratio (thinner)

Add retarders such as borax

Front 16

Solubility

Back 16

Slightly soluble in water

Water should be saturated with gypsum to prevent erosion

Front 17

Things needed

Back 17

Mixing bowl, spatula, room temp water, and gypsum product

Front 18

Tech of use

Back 18

Measure water in cylinder

Measure powder in grams

Add powder to water

Hand mix until smooth, homogenous workable and free of bubbles

Use vibratory to reduce bubbles

1 minute

Front 19

Filing impression

Back 19

Flow ahead of itself from one end of the impresión.

Use dental vibratorio

Front 20

Decreased setting time (faster)

Back 20

More mixing

Lower water to powder ratio (thicker)

Addition of an accelerator (potassium sulfate)

Front 21

Setting expansion

Back 21

Plaster -most

Stone-meh

High strength stone-little

Front 22

What will make expansion go up

Back 22

Thicker mix with more mixing

Front 23

What will decrease expansion

Back 23

Thinner mix with decreased mixing

Front 24

Hygroscopic expansion

Back 24

The expansion of gypsum materials when immersed in water.

Front 25

Strength

Back 25

Measured in terms of crushing or compressive strength

Front 26

Wet strength

Back 26

Strength measured when sample contains all of the water in excess of what is needed for hydration.

Front 27

Dry strength

Back 27

Measure when excess water is not present in sample.

Front 28

Factors that affect strength

Back 28

Thicker mixes increase strength

Thinner mixes decrease strength.