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20 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Mineral found in nature |
Gypsum |
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Replica of oral cavity Postitice reproduction |
Gypsum - diagnostic cast (study model) - working cast (working model) - dies |
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When is gypsum used? |
For lab procedure/ clinically |
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Desirable qualities of gypsum |
Acute, reproduction of fine detail, dimensional stability, strength & resistance to abrasion, minimal solubility, easy to use, cost, color, safe |
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Calcium sulfate Dihydrate -> solid mass + heat/pressure-> hemihydrate powder |
Calcination |
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Hemihydrate + water = flowable mixture When reaction complete : |
Hemihydrate convert back to dihydrate (exothermic reaction) |
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Heated in oPen vat? |
model Plaster |
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Heated in closed container (under pressure in steam @high temp) |
Dental stone |
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Increase pressure/heat High strength / Low expansion |
Die stone |
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Gypsum physical properties |
Size, Shape, Porosity Plaster - larger, irregular, high porosity Stone - smaller, symmetrical, less porosity |
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Main difference btw plaster & stone? |
Particle size & Shape |
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What affects strength & resistance to abrasion of final gymsum? |
Shape of particle & Porosity |
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(Gyp behavior) setting expansion |
Only occurs during hardening = crystal growth as particle join |
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Highest expansion rate 빨라 |
Plaster |
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Lowest expansion rate 느려 High strength, low expansion stone? |
Die stone |
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Solubility & Positity [direct correlation] |
Avoid expose model to water for long time |
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ADA classification of gypsum |
Type I Impression pl Type II Model pl Type III Dental stone Type IV Die stone (high strength, low expansion) die dental stone Type V Investment (high strength, high expansion) 물 제일적게넣어 |
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Pattern wax |
Inlay w Casting w Baseplate w |
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Processing wax |
Boxing w Utility (periphery w) Sticky w |
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Impression wax |
Corrective impression w Bite registration w |
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