ch 10 dental mat cont

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jackiedh
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73491
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ch 10 dental mat cont
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2011-03-17 18:12:46
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dental mat cont
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dental mat ch 10 cont
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  1. which two base metals are added to gold to increase harness?
    copper and silver
  2. why is it important for the modulus of elasticity (stiffness) of base metals be 2X more than gold based alloys?
    for partial denture framework use
  3. what are the two disadvantages of base metals?
    • harder = hard to cut and polish
    • higher casting temp = more cost for equip
  4. what forms after metal cools post melting and casting?
    crystals (grains)
  5. which are more desirable in crystal formation, small or large grains?
    small
  6. what two components are added to gold-based alloys to keep crystals from growing too large?
    iridium and ruthenium
  7. what is annealing?
    it can improve properties of ____-_____ alloys
    • reheating
    • gold-based
  8. annealing base-metal alloys will ______ the properties
    degrade
  9. what four components are added to form oxides on the metal to bond porcelain?
    • indium
    • iron
    • gallium
    • tin
  10. what is heated at high temp to form oxides on the surface when dealing with pfms?
    substructure
  11. porcelain ______ fuses to the oxide layer
    CHEMICALLY
  12. t/f there is a slight change in metal composition to withstand high heat of firing porcelain (turning into glass)
    true
  13. why is opaque porcelain placed on metal?
    to hide color (keeps the oxide color from showing through the porcelain and the main color is used for the crown)
  14. t/f less tooth reduction is necessary for porcelain than for full metal cast crowns
    FALSE! MORE tooth reduction
  15. the "coping" metal for a pfm is ___-___mm thick
    0.3-0.5
  16. what must the coping of a pfm be besides at least .3mm thick to prevent distortion at high temps?
    • NO SHARP ANGLES
    • CONVEX
  17. what does the thickness of the porcelain need to be in order to obtain a solid structure for a crown?
    1.5mm
  18. what are the three types of porcelain alloys?
    • high-noble
    • noble
    • base-metal
  19. why do the metal and porcelain have compatible rates of thermal expansion?
    to keep them from cracking
  20. the tooth structure for a pfm must be reduced _____mm thick
    1.8
  21. what are the most common base metal alloys for removable prosthetic casting alloys? (2)
    • chrome-cobalt
    • nickel-chrome
    • (chromium content that gives corrosive resistance of these)
  22. ____-fusing porcelains are used more because they produce less wear of opposing enamel than medium or high-fusing porcelains
    LOW
  23. t/f noble metals are more biocompatible with oral tissues
    true
  24. ____ metals corrode less than base metals
    noble
  25. which corrosion products are responsible for allergic responses?
    base metals
  26. t/f higher allergy rate for a male compared to a female is 10:1
    FALSE! for a FEMALE compared to a MALE is 10:1 (jewelry might be the factor that sensitizes them)
  27. where would an allergic rxn to nickel in the oral cavity most likely be located?
    around the free gingival tissues from a crown
  28. t/f some rxns to nickel cause skin rxns even if it is coming from the mouth
    true
  29. what are solders used for?
    to repair cast restorations (usually gold-based alloys)
  30. what four things do gold-based solders do?
    • join units of a bridge together
    • add contacts
    • close holes in the occlusal surface from grinding
    • marginal deficiencies
  31. the HIGHER fineness number of gold solder, the _______ the gold content, the ________ the melting point of the solder
    • HIGHER
    • LOWER
  32. ______ is added to both gold & silver solders to lower the melting range
    TIN
  33. What kind of solder is used for orthodontics-fixed space maintainer components, solder wire components together
    Pediatric Dentistry-space maintainer?
    SILVER solder
  34. Wrought alloy metals are formed _____ the metal is cast
    AFTER
  35. what are wrought metal alloys?
    alloys that have been mechanically changed metal into another form
  36. a wrought alloy metal is ______ and has a ________ yield strength than just an alloy
    • harder
    • greater
  37. wrought metal alloys may be annealed (heat modified) to create what?
    resistance to deformity
  38. t/f overheating a wrought metal alloy can degrade the properties of the metal
    true
  39. what kind of wire is used for clasps of a removable prosthesis?
    wrought
  40. which wire is used for ortho arch wires?
    wrought
  41. _______ wires in ortho or oral surgery are made out of wrought metal
    ligature
  42. endodontic files and reamers are made out of what type of wire?
    wrought wire
  43. what is it in an arch wire that exerts the forces that move the teeth?
    the "memory"
  44. what creates memory in the wire so it tries to reassume its original shape?
    resistance to deformity
  45. Arch wire held to ortho bracket by _______ wire or _______
    • ligature
    • elastics
  46. brackets and bands in ortho are either _____ or _____to teeth
    bonded or cemented
  47. what type of wrought wire makes up multiple cutting edges?
    (sick and) TWISTED wire
  48. which are more flexible, nickel-titanium or stainless steel files?
    nickel files
  49. reamers have ______ twists than files
    fewer
  50. reamers cut _____
    fast
  51. t/f hand held or rotary files/reamers are used in a root canal
    true
  52. what is the canal from a root canal sealed with so bacteria does not grow in its space?
    gutta percha
  53. what is the purpose of endodontic posts?
    to retain core buildup (the big giant filling)
  54. ______ posts engage the root canal surface with threads like a screw
    active
  55. ______ posts are cemented into the canal space engaging canal walls
    passive
  56. what post transmits less stress to the root than tapered, and forces are evenly distributed?
    parallel
  57. with a _____ post, a wedging force on the root has a higher risk of root fracture
    tapered

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