Dental Materials

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Dental Materials
2011-02-02 18:02:30

ch 14
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  1. the purpose of an impression is to make a _________ reproduction of teeth and tissues then once poured in gypsum is to make a _______ reproduction of teeth and tissues
    • negative
    • positive
  2. what are the two hydrocolloids, give examples
    • reverisble: Agar
    • irreversible: Alginate
  3. what are three types of elastomers
    • polysulfides
    • silicone rubber
    • polyethers
  4. what are the two categories of elastic impressions
    hydrocolloids and elastomers
  5. what are three types of inelastic materials?
    • plaster-type I gypsum
    • compound
    • zinc-oxide/ eugenol
  6. reversible hydrocolloid unergoes what type of reaction?
    physical only
  7. the solid to gel state of a reversible hydrocolloid is temperautre dependent?
  8. temp solidifies but not temp liquifies
  9. absorbs moisture
  10. contract and squeeze out liquid
  11. reversible hydrocolloid (agar) is popular for ______ preparations but ______
    • multiple
    • unstable
  12. solidification by called is called?
  13. ______ ______ is needed for proper set gypsum for the reversible hydrocolloid
    potassium sulfate
  14. what is the gel strengthener for reversible hydrocolloid?
  15. what is the antifungal for the reversible hydrocolloid?
    alkyl benzoate
  16. _____ and _____ retard set of gypsum products
    borax and agar
  17. what cancels the effect of borax and agar?
    potassium sulfate
  18. what are three advanatages to the reversible hydrocolloid (agar)
    • moist field
    • accuracy
    • inexpensive
  19. an example of irreversible hydrocolloid is?
  20. what type of reaction does irreversible hydrocolloid undergo?d
  21. t/f irreversible hydrocolloid is temperature dependent by
    false not temperature dependent
  22. how can you delay or accelerate the setting up of irreversible hydrocolloid (alginate)
    • delay-cold water
    • accelerate-warm water
  23. t/firreversible hydrocolloids are susceptible to imbibition but not syneresis
    false susceptible to both
  24. what is the most widely used impression material?
    irreversible hydrocolloid (alginate)
  25. what is added to keep alginate from interfering with set of gypsum products?
    potassium sulfate
  26. what is the mixing time for regular set alginate?
    2-3 min
  27. what ist he workingtime for fast set alginate?
    1.25-2 min
  28. what is not recommended with preparing alginate to affect the setting time?
    adjusting water to powder ration
  29. how long do you rinse and disinfect an impression
    10 minutes
  30. you must pour an impression within _____ hour of taking the impression, why?
    • 1 hour
    • looses moisture and changes shape
  31. why does an impression change shape over time?
    due to water loss (shrinkage)
  32. what must be covered on the maxillary of an impression? mandibular?
    • max-hamular notch
    • man-retromolar pad
  33. when loading a tray you load ____ increments and load ____
    • large
    • quickly
  34. a right handed clinician must stand _____ pt at ____oclock position
    • behind
    • 11
  35. a left handed clinician must stand _____ pt at ___oclock position
    • behind
    • 1
  36. hydrocolloids are _____ and elastomers are ___ _____
    • aqueous
    • nonaqueous
  37. t/f elastomers are hydrophobic
  38. silicone rubber is a ______ reaction silicion
  39. polyvinyl siloxane (PVS) is ______ reaction silicion
  40. what type of material has the smallest dimensional change?
    polyvinyl siloxane PVS
  41. when must you pour a PVS impression
    within one week
  42. what type of gloves must be worn when mixing PVS? why?
    • vinyl
    • latex interferes with set
  43. what type disinfectants are appropriate for alginate and silicone
    • sodium hypochlorite
    • iodophors
  44. how long must you disinfect an impression?
    10-30 min