Dental Materials Final

  1. what causes post op sensitivity with amalgmas?
    • microleakage-shrinkage
    • expanding amalgam
    • dentinal tubules exposed
  2. Wha causes corrosion of amalgam?
    chemical reaction between amalgam and substances in saliva or food resulting in OXIDATION of amalgam
  3. how do you prevent corrosion of amalgam?
    using high copper alloys (no gamma 2 phase) or polish low copper amalgams
  4. what is the purpose of merucry?
    causes amalgamation and binds it all together
  5. what is murcury's most dangerous form?
  6. what componenets are needed to produce galvanism?
    two dissimilar metals
  7. what causes expansion in amalgam? 3
    • compostion of alloy particles
    • ratio of mercury-alloy powder (by weight)
    • saliva/moisture contamination
  8. why do you need to polish amalgam?
    to reduce the rate of corrosion
  9. what does polishing remove? 4
    • surface tarnish
    • stains
    • flash
    • roughness
  10. how does an amalgam get retention in a tooth? 3
    • bonded
    • undercut walls
    • mechanical retention
  11. how do you detect overhangs
  12. what is the relationship of zinc and corrosion of amalgam?
    zinc INHIBITS corrosion by reducing oxidation of other metals
  13. what are the three noble metals?
    • gold
    • platinum
    • palladium
  14. which noble metal is the most corrosive resistant?
  15. which noble metal has good gorrosive resistance, increases hardness of alloy and is less expensive than gold?
  16. ____% noble = no gold requirement
  17. high noble = ___ % noble/ _____% gold by weight
    • 60
    • 40
  18. when is the best time of day to view esthetic materials?
  19. when viewing esthetic materials a natural _____ light is great
  20. fluorescent lights=_____ and incandenscent lights= _____
    • more blue light
    • more yellow light
  21. t/f you want to take the shade in the light the patient is seen in most often
  22. the dental unit light ______ shade brightness and _____ color intensity
  23. what are the two fluoride RELEASING composites
    • glass ionomers
    • hybrid (resin-modified) ionomer
  24. what are the componenets of dental compostie/resin materials?
    • organic resin matrix (Bis-GMA or bisphenol-A, glycidal methacrylate, UDMA-urethrane dimethacrylte)
    • inorganic SILICA filler
    • SILANE coupling agent
  25. what are themost common filler particles?
    • silicate
    • quartz
    • glass
  26. what is the purpose of fillers?
    make resin stronger, reduce shrinkage and more wear resistant
  27. what is added to resin for radiopacity?
    barium stronium
  28. the ____ the filler the stronger and more ____ ____ the resin will be
    • HIGHER
  29. what is the advantage of light cured composites over self cured composites?
    light cured are LESS porous than self cured
  30. what causes post op sensitivity in composties?
    leakage, shrinkage (large composite increments)
  31. t/f adjusting water/powder ration is only recommended to increase the working time of gypsum products
    false-adjusting water/powder ration is NOT recommended-follow manufacturers instructions
  32. what increases/decreases work and setting time?
    • water temperature
    • cold water=longer set
    • warm water=shorter set
  33. how is the setting time affected by cold water? warm water?
    • cold water=longer set
    • warm water=shorter set
  34. what is being described: beta, weaker, irregular, porous particle, used for diagnostic casts, more soluble than stone, white in color, W/P=.45
    plaster (TYPE II)
  35. what is being described: alpha, strongest, less water needed, less porous, better than plaster, working casts/study model, white or yellow color, takes less water to turn into dihydrate, W/P=.30
    stone (TYPE III)
  36. what are the four effects of air incorporated into gypsum?
    • air exposure ACCELERATES set
    • prolonged exposure RETARDS set
    • water absorption
    • surface irregularities
  37. what is the initial set of regualr set gypsum?
    7-9 minutes from start to mix
  38. what is the working time for the intial set of gypsum?
    6-8 minutes to pour impression
  39. how can you tell if the initial set has begun with gypsum?
    loss of glossy appearance
  40. what type of reaction is the final set of gypsum?
    exothermic reaction
  41. how long must the regular set gypsum set before separation?
    1 hour
  42. at how many hours is the regular set gypsum 3x harder
    24 hours
  43. when can you disinfect regular set gypsum?
    24 hours=3x harder
  44. t/f failure to separate modle within 1 hour will have detrimental effects on characteristics of model
  45. what impression material is used for: study models, preliminary impression for complete dentures, partial denture framework
    opposing casts for crown and bridge treatments
    reparis of partial and complete dentures, provisional restorations, custom trays for fluoride or bleaching, sports protector andnight guards, removable orthodontic appliances?
    irreversible hydrocolloid
  46. what is the most widely used impression material?
    irreversible hydrocolloid
  47. what is irreversible hydrocolloid impression material not good for? 5
    • crown and bridge
    • inlays
    • onlays
    • titanium remobable partial dentures
  48. which impression material is agar?
    reversible agar
  49. what impression material is alginate?
    irreversible hydrocolloids
  50. what are the five elastic impression materials?
    • reversible (agar) hydrocolloid
    • irreversible (alginate) hydrocolloid
    • plysulfides (elastomer)
    • silicone rubber (elastomer)
    • polyether (elastomer)
  51. what are the four types of inelastic impression materials?
    • type I gypsum
    • plaster
    • compound
    • zinc-oxide eugenol
  52. what is used as a disinfectant for impression materials?
    sodium hypochlorite and iodophors
  53. how long should an impression be disinfected for before the pour?
    10 minutes
  54. what are the four purposes of diagnostic casts?
    • study model/diagnostic casts
    • reproduce preparations for final restoration
    • postive reproduction of teeth and tissues
    • impression=negation reproduction
  55. how is gelation time increased or decreased?
  56. what state is gelation if chilled? heated?
    • chilled=gle, semisolid (jell-o)
    • heated=reverse into a liquid suspension (sol)
  57. what retards the set of gypsum products?
    borax and agar
  58. what are the ingredients of reversible hydrocolloid (agar)? 4
    • seweend extract
    • potassium sulfate
    • borax
    • alkyl benzoate
  59. what is the antifungal in agar?
    alkyl benzoate
  60. what is the gel strengthener in agar?
  61. what are the ingredients of irreversible hydorcolloid (alginate)? 2
    • potassium or sodium alginate
    • seweed derivative
  62. what is added to keep alginate from interfering with the set of gypsum productes?
    postassium sulfate
  63. how do you store an alginate impression before pouring?
    • rinse and disinfect 10 minutes
    • wrap impression in wet paper towel
    • place in ziploc bag expressed of air
  64. how quickly should you pour an impression?
    pour withing one hour
  65. the sol to gel state is a ____ reaction ONLY, _____ dependent
    • physical
    • temperature
  66. wghat happens during hysteresis when the reversible hydrocolloid is cooled?
    turns to a solid or gel
  67. what happens to the reversible hydrocolloid during syneresis when left standing?
    gels contact and squeeze out, liquid forming an exudate on the surface (susceptible to imbibition-absorb moisture)
  68. what are the three advantages to reversible hydrocolloids?
    • moist field
    • accuracy
    • inexpensive (exept for equipment(
  69. what are the disadvantages of reversible hydrocolloids? 3
    • dimensionally unstable -pour immediately after disinfection
    • only ONE pour
    • deformation upon hard compression
  70. what are the 2 advantages for irreversible hydrocolloids?
    • not temp dependent
    • popular for study models
  71. what are the disadvantages for irreversible hydrocolloids?
    • imbibition
    • syneresis
Card Set
Dental Materials Final
amalgams through the END