Dental Pulp 15

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  1. Define thermal conductivity:
    amount of heat that passes per second through a body 1m thick, area of 1m2, temp gradient is 1K
  2. Materials with low thermal conductivity are:
    enamel, dentin, porcelain, cements, resins, and GP
  3. Define specific heat:
    amount of heat to raise temp of 1Kg of substance by 1K (water is high, metal 10% of)
  4. Metals in terms of specific heat and thermal conductivity?
    low specifc heat, high conductivity (heat and cool more rapidly)
  5. Define thermal diffusivity?
    thermal conductivity divided by specific heat times density
  6. Define the linear coefficient of thermal expansion (LCTE):
    change in length per unit length of material for a 1K change in temperature

    gold, GI, porcelain equal to dentin

    GP is not, it contracts, therefore you need compaction pressure as it cools
  7. What is the washed field technique?
    Tooth surface is expose to air-water spray for 5 seconds before cutting. 1 second up and 4 seconds cut afterwards.
  8. Pulpal reactions to restorative procedures may be caused indirectly, not to excessive heat production, how?
    1. rate of expansion of dentinal fluid creates shear forces tearing the cell membrane

    2. Evaporative fluid flow, outward flow that is so fast it tears membranes
  9. Dental procedures can elevate pulpal temps:
  10. During tooth preparations what determines the amount of frictional heat produced?
    • 1. force to bur
    • 2. cooling effficency of irrigant
    • 3. prior wear/design of bur (fissure vs. diamond)
  11. What chemical mediator can be used as a marker of tooth pulpal insult?
  12. Operative variables rated in protection of pulp? bur speed, smear layer removal, RDT, resotrative materials?
    RDT>bur speed>smear layer removal

    not restorative material
  13. System B range of 200-600C produced what temp increase in root surface? Floren 1999 study
  14. WVC shown to increase apical temp by only __C and cervical temps by only __C.
    • 4
    • 12.5
  15. Hydrated mineralized dentin denature temp?
  16. Dehydrated dentin denature temp?
  17. Demineralized hydrated dentin denature temp?

    can happen with MTAD irrigant, which demineralizes up to 10um deep
  18. What temp rise causes irreversible damage to PDL?
    10C for greater than a minute
  19. What Laser stand for?
    light amplification by stimulated emission radiation
  20. Laser differ from coventional light, how? 3
    monochromatic (single wavelength)

    very low divergence (collimated)

    coherence (photons in phase)
  21. Which lasers emit invisible light?
    CO2 ER:YAG and Nd:YAG

    Excimer are visible
  22. Lasers will do four things when interacting with tissue
    • 1. through (no injury)
    • 2. reflect (no injury)
    • 3. scattered (less intense, less precise)
    • 4.  absorbed (converted to thermal energy)
  23. Most effective laser on tissues with high water content and is highly absorbed by all biologic hard and soft tissues?
    CO2 will damage pulp
  24. Most effective laser on pigmented or vascular tissues?
  25. Laser interacts with pulp very well, all vascularized tissues?
  26. Which lasers would be ideal for cleaning and shaping root canals?
    Nd:YAG, argon, Er:YAG, Er:YSGG, and excimer
  27. Extent of interaction of laser energy with tissue will be determined by: (2)
    1. specific wavelength

    2. optical characterisitcs of the particular target tissue
  28. Clinician controls four parameters with laser use:
    • 1. power density
    • 2. energy density
    • 3. pulse reptition
    • 4. continous vs pulsed energy and direct contact or no contact with target tissue
  29. Four approaches to reducing pulpal temp rise with lasers?
    • 1. cooling air water spray
    • 2. brief pulse
    • 3. excimer lasers that operate in the UV range with short pulses
    • 4. occlusion of dentinal tubules (done with Nd:YAG and excimer lasers)
  30. Limitation of laser use in root canals?
    • 1. light emitted at end instead of side
    • 2. guide must be small ~.2um
    • 3. stiff but no brittle
  31. First ype of laser used in densitry?
    Ruby lasers
  32. CO2 laser and dentin permeability?
    inc 1.4-24 fold with removal of plugs and smear layer

    creates severe thermal damage
  33. The laser that harms the hybrid layer creating by bonding with dentin adhesive?

    vaporizes exposed collagen fibrils
  34. Name laser: little thermal damage, improved cutting efficency

    vaporizes water so rapidly to create microexplosions, mechanical ablation
  35. Name laser: UV range photons, reduced heat absorption and reduced dentin cracking
    Excimer lasers, photoacoustic distruction
  36. Two mechanisms for dentinal tube occlusion by lasers for hypersensitivity?
    1. melting and fusing dentin or the smear layer or coagulating proteins in tubes

    2. directly reduce neuronal activity

    Nd:YAG most studied

    65%-72% reduction (air/probing)

    combined with Fl varnish, 90% reduction
  37. Another term for airborne particle abrasion?
    kinetic cavity preparation
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Dental Pulp 15
2013-10-26 23:22:18
Quiz 15

Dental Pulp 15
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