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Dental Materials II - Midterm > Midterm > Flashcards

Midterm Flashcards

1
Q

define amalgam alloy

A

a combination of two or more metals (NO MERCURY!!)

metals include: silver (Ag), tin (Sn), copper (Cu), zinc (Zn)

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2
Q

define amalgam

A

a combination of a metal alloy + MERCURY

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3
Q

what is the setting reaction for conventional amalgam?

A

Ag3Sn + Hg → Ag3Sn (γ) + Ag2Hg3 (γ1) + Sn7Hg(γ2)

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4
Q

in the 3 phase setting reaction process for conventional amalgam, which is the strongest & most corrosion resistant product?

A

(γ) Ag3Sn

*this is the unreacted particle

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5
Q

in the 3 phase setting reaction process for conventional amalgam, which is the weakest and least corrosion resistant product?

A

(γ2) Sn7Hg

*slides show this product as Sn7-8Hg or Sn8Hg

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6
Q

in the 3 phase setting reaction process for conventional amalgam, which product would you want to get rid of and why?

A

(γ2) Sn7Hg because it is the weakest and most susceptible to corrosion

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7
Q

in the 4 phase setting reaction process for conventional amalgam, what is the weakest phase?

A

voids

*if asked about the 4 phase process rather then the 3 phase process, the weakest product is voids and NOT γ2

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8
Q

in the 3 phase setting reaction process for conventional amalgam, list the reaction products from strongest & most corrosion resistant to weakest and least corrosion resistant

A

(γ) Ag3Sn > (γ1) Ag2Sn3 > (γ2) Sn7Hg

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9
Q

is there any unreacted mercury left in the setting reaction for conventional amalgam?

A

NO!!!

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10
Q

are there any unreacted products left in the setting reaction for conventional amalgam?

A

yes, (γ) Ag3Sn - silver and tin

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11
Q

under condensation of amalgam causes

A

↓ strength
↑ expansion
↑ corrosion
↑ creep

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12
Q

what are the disadvantages of tin in amalgam?

A
  • weakened alloy (decreased strength)

- increased tarnish/corrosion (decreased corrosion resistance)

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13
Q

what are the advantages of tin in amalgam?

A

it quickens amalgamation (decreases the amalgamation time)

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14
Q

what is the purpose of zinc in amalgam alloy composition?

A

it is a oxide scavenger (it absorbs oxygen during manufacturing)

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15
Q

what are the problems caused by zinc if contaminated by water?

A
  • post-op pain
  • blister formation
  • delayed expansion (gas production)
  • recurrent decay
  • increased tarnish/corrosion
  • decreased strength
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16
Q

what are the advantages of silver in amalgam?

A

it is corrosion resistant

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17
Q

what are the problems with too much Hg (>55%) in amalgam?

A

↓ strength
↑ expansion
↑ corrosion
↑ creep

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18
Q

what are the problems with under trituration of amalgam?

A

↓ strength
↑ expansion
↑ corrosion
↑ creep

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19
Q

what was the mechanism behind the significant improvement in dental amalgam that occurred about 40-50 years ago?

A

we began using a silver-copper (AgCu) eutectic which eliminated the (γ2) Sn7Hg from final set amalgam, using this new system allows the Cu to be more reactive thus removing γ2 from the system

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20
Q

what is the proper alloy to mercury ratio?

A

1:1

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21
Q

how much copper might you find in conventional amalgam alloy?

A

up to 5%

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22
Q

how much copper is in high-copper amalgam alloys?

A

12-28% Cu

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23
Q

what is a clinical observation you may see with the new high-copper alloys compared to the older conventional alloys?

A

increased incidence of ditching at margins

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24
Q

it is absolutely NOT acceptable to replace amalgam restorations for which two reasons?

A
  • ditching at the margins

- they are tarnished

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25
Q

amalgam restorations SHOULD be replaced under which two primary conditions?

A
  • fracturing

- recurrent decay is present

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26
Q

what is the best description for management of the interface between amalgam and tooth structure?

A

the seal of the margin can be made effective at first with the use of varnish, but the amalgam will eventually seal itself off even though the varnish is hydrolyzed and eliminated

27
Q

which condition of chronic Hg toxicity is somewhat specific?

A 
intention tremors (ataxia)
you don't show signs of tremors until you intend to do something
28
Q

what is the major constituent of copper amalgam?

A

mercury (Hg)

29
Q

what is the major constituent of high-copper amalgam alloy?

A

silver (Ag)

30
Q

what is the most significant concern addressed by regulatory agencies about the use of dental amalgam?

A

environmental contamination

31
Q

what is the “threshold limit value” mean to the use of amalgam?

A

the max concentration allowed in the air of a workplace in which mercury is used

32
Q

what are the 4 statements required by the FDA that you must tell patients about amalgam restorations?

A
  • amalgam is an effective restoration material
  • mercury (Hg) is toxic
  • amalgam does release some mercury
  • not enough Hg is released from dental amalgam to cause toxicity
33
Q

what is the most basic monomer in denture base resin?

A

methyl methacrylate

34
Q

what is the most basic polymer in denture base resin?

A

polymethyl methacrylate

35
Q

what is the major component of the powder used in denture base resin?

A

polymethyl methacrylate polymer beads

36
Q

what is the major component of the liquid used in denture base resin?

A

methyl methacrylate monomer

37
Q

what is the initiator in the powder of denture base resin?

A

benzoyl peroxide

38
Q

benzoyl peroxide allows for ___________

A

control of the setting material in the powder of denture base resins

39
Q

what is the catalyst in the liquid monomer used in denture base resins?

A

tertiary amines

40
Q

tertiary amines are commonly used as a catalyst for ________

A

cold-curing (autocuring)

41
Q

what is the best way to store a denture when not in the mouth?

A

clean with denture cleanser, rinse throughly, then store wet (in water)

42
Q

what is the primary cause of internal porosity in the thick portion of a denture base?

A

using too high a temperature during the polymerization process

43
Q

what makes the addition of Lucitone 199 to methacrylate a better denture base?

A

it has a primary polymethyl methacrylate phase and a secondary phase that is butadiene rubber

44
Q

what is the average polymerization shrinkage of powder/liquid polymethyl mehtarcylate polymer bead/methyl methacrylate monomer cold-cure resin?

A

6-8%

*slides say 7%

45
Q

what is the most significant difference between a chair side temporary hard reline material and a denture repair material?

A

the temporary reline material should have al lower exotherm during polymerization

46
Q

what type of material is used by most dentist to make whitening trays for professionally directed home whitening?

A

thermoplastic, ethyl vinyl acetate, 0.040 inches thick

47
Q

what type of material is used by most dentist to make temporary occlusal splints?

A

thermoplastic, polyproylene, 0.040-0.080 inches thick

48
Q

why is it important to know that tooth-colored temporary crowns are made of polycarbonate?

A

because polymethyl methacrylate will not chemically adhere to polycarbonate

49
Q

dimethacrylate monomer polymerizes to form _____________

A

cross-linked polymers

50
Q

what are the components of a composite system used in making dental restorations?

A
  • glass filler
  • resin matrix
  • silane coupling agent
  • chemicals to initiate and/or catalyze the polymerization
51
Q

what are the two most significant concerns/disadvantages of posterior composites?

A
  • lack of abrasion resistance

- imperfect bonding to tooth structure

52
Q

what are 2 reasons composite will change its color/appearance when light cured?

A

some of the photoinitiator photobleaches and resin changes its refractive index during curing

53
Q

which of the following is the best comparison of aerosil to the new nanofiller materials?

A

the aerosil is not radio-opaque and most of the new nanofiller materials are

54
Q

what wavelength is the greatest absorption of activation light for camphorquinone the way it is used in dentistry?

A

470-475 nm

55
Q

what is the major disadvantage of most LED curing lights?

A

they may not have a bandwidth sufficient to initiate a second photoinitiator (too narrow a bandwidth)

56
Q

what is the range of polymerization shrinkage of regular filled composite restorative materials?

A

about 1-3%

57
Q

methods for decreasing polyermization shrinkgage

A

controlled by dentist:
- incremental placement (layering technique)

controlled by manufacturer:

  • increase filler volume (more filler)
  • increase the size of the monomer
  • add a miscible set of monomers that phase separate when polymerized (polymerization induced phase separation - PIPS)
  • ring opening of the polymer
58
Q

how could a manufacturer making microhybrids formulate a flowable composite for use in posterior composite restorations?

A

they should keep the same glass filler type but increase the volume fraction a little

59
Q

what happens if a dentist uses a curing light with twice the radiance recommended for use for composite?

A

the composite would be exposed to the light for half the recommended curing time

60
Q

what is an inhibitor of polymerization that is ubiquitous to the environment?

A

oxygen

61
Q

list the three inhibitors of polymeriaztion

A
  • oxygen
  • hydroquinone (HQ)
  • butylated hydroxytoluene (BHT)
62
Q

what material would generally produce the greatest amount of polymerization shrinkage?

A

flowable composite

63
Q

what is the current risk level of bisphenol-A?

A

it may be of some concern in infants and small children from all types of exposure
*slides say exposure is not sufficient to cause any toxic effect

Dental Materials II - Midterm (1 decks)

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