Dental Materials

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Author:
cassiedh
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62588
Filename:
Dental Materials
Updated:
2011-02-02 18:02:47
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ch15
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ch15
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  1. hard replicas of hard and soft tissue of the pts oral cavity made from gypsum products also referred to as models
    casts
  2. the weakest most porous form of gypsum product used in dentistry
    model plaster
  3. a stronger less porous form of gypsum than model plaster that is used in dentistry
    dental stone
  4. replicas of the prepared teeth that are general removable from working cast
    dies
  5. the densest form of gypsum product used in dentistry
    die stone
  6. casts genreally made from dental plaster or stone and used for pt education, treatment planning and tracking the progress of treatment as with orthodontic models these casts are also know as study models
    diagnostic casts
  7. casts generally made from one of the dental stones that are strong enough to resist the stresses of fabricating an indirect restoration or prosthesis these casts are also known as master casts
    working casts
  8. pouring the cast referes to the process of vibrating the flowable gypsum product into the impression this process must produce a cast that is the exact replica of the impression
    pouring
  9. the precess of removing excess hardened gypsum from the cast for ease in working with the cast and appearance in presentation
    trimming
  10. what mineral do you start with?
    calcium sulfate Di-hydrate
  11. what is the formula for calcium suflate di-hydrate
    CaSO4 2 H2O
  12. what type of gypsum has the highest setting expansion?
    plater type II gypsum
  13. what type of gypsum has a low setting expansion
    stone type III gypsum
  14. plaster type II is a ____ calcium sulfate hemi-hydrate
    beta
  15. what is the w/p ratio for plaster type II gypsum
    0.45
  16. stone type III gypsum is a _____ calcium sulfate hemi-hydrate
    alpha
  17. what is the water to powder ratio for stone type III gypsum
    0.30
  18. what is the difference in the water content of the types of gypsum?
    lots of water is neeeded to turn into a di-hydrate, it is very porous and soaks up water.
  19. t/f it takes more water to take a type II mpression than a type IV why?
    • true
    • takes more or less water to turn it into a di-hydrate
  20. die stone, type IV gypsum is an ____ calcium suflate hemi-hydrate
    alpha
  21. what type of gypsum has the highest compressive strength, is the most wear resistant and has the lowest expansion?
    die stone, type IV gypsum
  22. what is the water to powder ratio for die stone, type IV gypsum
    0.23
  23. die stone, type IV gypsum has the best _____ detail with PVS which is an _____ silcon
    • surface
    • addition
  24. t/fpowder is sifted into the water
    true
  25. what happens if spatulation is increase?
    • shortens setting time
    • increases rate setting expansion
  26. properties of gypsum products are ______ related to their water to powder ration
    DIRECTLY
  27. an increase in water causes what three things?
    • weaker
    • less accurate model
    • longer set time
  28. what is the initial set time for regular set products?
    7-9 minutes
  29. what is a sign that initial set has begun
    loss of glossy appearance
  30. why type of reaction happens during the final setting time?
    exothermic reaction
  31. how long must you wait before separation?
    1 hour
  32. waiting 24 hours the model is now ____times harder
    3
  33. failure to separate model within _____ will have detrimental effects on characteristics of model?
    1 hour
  34. what is slurry water?
    set gypsum (CaSO4) particles in runoff water from trimming
  35. if changes are made in the final setting time one sacrifices ____ ____, ______ or _____ ____
    • working time
    • strength
    • setting expansion
  36. how long must you wait for the second pour in the double pour technique?
    10 minutes
  37. t/f the gypsum can absorb the water from the air
    true
  38. what type of container do you want to store gypsum in?
    air tight
  39. ___ exposure to gypsum accelerates set
    air
  40. prolonged air exposure ____ gypsum
    retards
  41. why must the mixing bowls and spatulas be meticulously clean?
    if not it accelerates setting time
  42. t/f put excess material down the drain
    false! in the trash it does NOT drain
  43. before trimming you must ____ the base of the stone model in _____ for __-__ minutes BEFORE trimming but NEVER ____ the anatomic portion
    • soak
    • water
    • 5-10
    • soak
  44. t/f the anatomic portion of the model must be soaked before trimming and never the base
    false! soak base not anatomic portion
  45. t/f you must soak the base after trimming
    false- BEFORE
  46. the base should be ___/___ of the model and the anatomic should be ___/___
    • 1/3
    • 2/3
  47. the occlusal plane must be ______ to base
    PARALLEL
  48. how is the anterior of a maxillary trimmed
    to a point
  49. how is the madibular trimmed?
    rounded from cuspid to cuspid
  50. more ____=greater expansion and less strength
    water
  51. what are four things to describe plaster?
    • softer
    • less accurate
    • greater porosity=less surface detail
    • lower compressive strength
  52. what are three characteristics of diestone
    • hardes
    • most accurate
    • highest compressive strength
  53. what is added to accelerate set?
    potassium sulfate
  54. what is added to slow the set
    borax
  55. air incorporated with mix results in surface _____
    irregularities
  56. water should be _______ and gypsum should be _____ to mix
    • MEASURED
    • WEIGHED
  57. the model base is trimmed to be _______ to midline between the central incisors
    perpendicular
  58. silicone and polyether impression + gypsum=____ ____ ___
    best surface detail
  59. plaster=
    betta
  60. stone=
    alpha
  61. t/f plaster is more soluble than stone
    true
  62. _____ exposing models to water for long periods of time
    AVOID

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