Gypsum Flashcards

1
Q

gypsum

A

soft sulphate, made of calcium sulphate, casts

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2
Q

gypsum uses

A

study model/cast - positive replica of dentition
cast, die, mould material

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3
Q

types of gypsum

A

plaster - heated in open vessel, large porous
dental stone - heated in autoclave, regular crystals
densite - heated in presence of chloride, compact particles
crystalline structure determines properties

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4
Q

setting reaction

A

dihydrate crystals form, expansion occurs

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5
Q

properties of gypsum

A

reproduction of surface detail, strength, surface hardness, setting time, expansion, porous [rough surface], low surface hardness
develops over 24hr period, dendrite the stronges

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6
Q

adv and disadv of gypsum

A

adv - dimensionally accurate and stable, low expansion of stone/densite, good colour contrast
disadv - low tensile strength, poor abrasion resistanc,e very brittle, surface detail less than elastomer impression, poor wetting of some impression materials

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