Gypsum Flashcards
Study Model
used to plan treatment and observe progress
Cast
replica on which appliances are fabricated. more accurate, more than 1 tooth (quad or full arch)
Die
working replica of a single tooth. removable part of a cast
Study Model Components
Art Portion + Anatomical Portion. Base/Front/Side/Heel
Study Model Qualities
accuracy, stability, fine detail, strength, compatible w impression material
Types of Gypsum
5 Types: 1. Impression Plaster 2. Plaster (weakest) 3. Dental Stone (we use) 4. Improved Stone 5. High Strength
Chemical Formula of Gypsum b4 manufacturing
Calcium Sulfate Dihydrate
Chemical Formula AFTER manufacturing
Calcium Sulfate Hemihydrate! Powder form, 1.5 moles water removed
Type 3 Stone
what we use, yellow or white; heated under pressure - particles uniform, less pourus, denser, stronger
Type 4 High Strength Stone
boiled w chloride; denser, harder, stronger, cuboidal particles
Exothermic Reaction
liberation of heat during setting, post mixing hemihydrate w water = dihydrate
Water Ratios
higher strength, smoother particles = less water
Type 3 Stone W/P Ratio
28-30mL / 100gms
Working Time
5-7 minutes
Initial Set
loss of gloss, no longer flows