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23 Operative > 20 - Glass Ionomers and Composite Resins > Flashcards

20 - Glass Ionomers and Composite Resins Flashcards

1
Q

how are glass ionomers cured

A

chemical and light cured

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2
Q

how does phase I GI rexn occur

A
  • silica gel coating on glass particles formed
  • matrix formed between glass particles
  • matrix begins to attach silica gel coating on the glass
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3
Q

how long does phase I GI rxn take

A

4-5 minutes

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4
Q

is glass ionomer reaction sensitive to H2O solution or upratke during this phase

A

YES

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5
Q

what happens if GI reaction has moisutre during pahse I

A

GI becomes soft and weaekt

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6
Q

what happens during GI phase II

A
  • matrix formation completed and GI forms bond to tooth
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7
Q

how long does GI phase 2 take

A

several minutes to several hours

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8
Q

what phase is very sensitive to moisutre loss or dehydration

A

phase II

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9
Q

what is the liquid in GI

A

polyacrylic

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10
Q

what are the different sets in chemical cure

A
  1. initial set
  2. final set
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11
Q

what happens sduring initial set of chemical cure

A
  1. cross linkages between PAA and aluminosilicate glass
  2. moisture sensitive and acid soluble
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12
Q

final set of chemical cure

A
  1. achieves more permanent set than light cured
  2. bonds to tooth structurel carboxyl groups attach to calcium or dentin
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13
Q

how does VLC cure GI

A

Resin component
cures in 30 seconds
Not as moisture
sensitive because
resin forms
protective scaffold,
once polymerized

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14
Q

strengths of class ionomers

A

Pulpal response
Conservation of tooth structure
Chemically bonds to dentin and cementum
Potentially anti-cariogenic
Fluoride leaches out into surrounding tooth structure
Good retention rates

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15
Q

weakness of GI

A

Lack of translucency
Rough surface
Technique sensitive
Delay required for finishing
Chemical cure (~6 minutes!!)
Solubility–water
Poor abrasion resistance
Do not use in area of function or wear
But can be great for kids and geriatrics

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16
Q

What can GI be used for

A
  1. fixed luting agent
  2. cavity liner
  3. cavity base
  4. core build-up material
  5. restorative material
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17
Q

cavity conditioner for GI

A

20% polyacrylic acid (KNOW THIS)

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18
Q

how to use cavity conditioner for GI

A
  1. 10-20 second scrub in prep
  2. rinse well
  3. blot dry of high vac
  4. apply Fuji IX or Fuji II LC
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19
Q

what is a resin modified GI cement that LUTES and does not conventionally BOND like composite?

A

Fuji plus

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20
Q

what GI requires a dual cure

A

Fuji II LC

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21
Q

what is a packable GI (after some setting)

A

Fuji IX

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22
Q

composition of composite resins

A
  1. bisGMA or dimethacrylate resin
  2. filler particles (usually glass or ceramic particles)
  3. coupling agents (silane compound)
  4. pigments
  5. UV light inhibitor (preservative)
  6. photo-initiatoar (ketone source)
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23
Q

what determines the composite resin?

A

fillers and resin base

(glass particle size, glass type/distribution, type of resin)

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24
Q

what must you consider regarding biocompatibility of composite resin

A
  1. mostly biocompatible but some problems
  2. hass allergic potential
  3. organic compound release during degradation and funcitonal use
  4. resin does not totally polymerize in degradation and leaching of constiutents
  5. POLYMERIZATION SHRINKAGE!!
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25
Q

do dental resins contain and leach bisphenol A

A

no- some sealants do thho

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26
Q

two types of polymerization

A
  1. chemical cure (auto-cure 2 paste)
  2. photo activation (VLC)
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27
Q

what is combined in chemical cured composite

A

tertiary amine and benzoyl peroxide

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28
Q

in chemically cured composited when combined, what happens

A

free radical are generated that start the polymerization of bis GMA

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29
Q

are chemicallly cured composite usually caries free

A

yes

30
Q

what are activating compounds that generate free radicals in composites

A
  1. diketones (Camphoroquinone)
  2. aromatic ketones (biacetyl)
  3. reducing agents (tertiary amines)
  4. proprietary agents (like Ivocerin in a ulk fill composite like Teric EvoCeram Bulk Fill)
31
Q

what do free radicals originate from

A

ketone source such as diketones or aromatic ketons

32
Q

what have a reducing agent (alpiphatic tertiary amine) which is present to lwoer the energy in the bonds of the ketone source so they will be split to form free radical

A

free radical

33
Q

do fre radical amines participae in the chemical reaxion as in the chemically cured materials

A

NO!!!

34
Q

must the light source be specific?

A

yes

35
Q

visible light activation using wavelengths greater than one

A

400 nanometers

36
Q

what is the most effect light activation

A

468nm 480 nm

37
Q

in terms of intensity, most modern LED lights have irradiance of what? some claim up to what?

A

at least 600 mW/cm2
some claim up to 3200 mW/cm2

38
Q

what initiate the polymerizatin of bisGMA or urethane dimethacylate

A

free radicals

39
Q

you must have proper what of light to initiate free radicals

A

proper wavelength

40
Q

the ___ of light source must be high enough to initiate free radical

A

intensity

41
Q

what are factors that influence cure

A
  1. Time
  2. Distance of light from resin
  3. Shade of resin
  4. Type of filler
  5. Thickness of resin
  6. Output of light (bulb life and line voltage)
42
Q

advantages of VLC resins

A
  1. Increased restoration density
  2. Decreased surface staining
  3. Increased working time
  4. Improved color stability
  5. Improved shelf life
  6. Higher degree of resin polymerization
43
Q

___ = organic = soft
___ = inorganic = hard

A
  • resin = organic = soft
  • filler = inorganic = hard
44
Q

what is the 1st step in wearing process

A

soft resin matrix begins to erode

45
Q

what leads to a rough surface which is plaque retentive

A

porosity

46
Q

what causes reduced compressive strength because restoration is not as dense

A

porosity in resin

47
Q

why do almost all composited exhibit the same pattern of wear?

A

because they are two phase materials (resin + filler)

48
Q

the end result and rate of occurrence to mechanism of wear is what?

A

different due to difference in filler particles and effectiveness which they are bound to the resin

49
Q

as filled size decreased, more fillers can be incorporated to [increase or decrease] strength

A

increase

hence, effects of plucking not as noticeable

50
Q

what are problems that can occur with smaller particles

A
  1. Smaller particles have a larger combined surface area, therefore they exert a strong thickening effect (increased viscosity) when added to a liquid such as bisGMA
  2. this can limit particle loading
51
Q

are silica filler radiopaque? explain

A

NOT radiopaque - must be coated with radiopaque coupling agents to improve radiodensity

52
Q

is there better smoothness with smaller or larger particles?

A

smaller

53
Q

are nanoparticles radiopaque

A

yes

54
Q

characteristics of resin

A
  1. high coefficient of thermal expansion
  2. high polymerization shrinkage
  3. resin weak and has poor abrasion resistance
  4. high resin content with small filler particle size allows for smoother surface finish of microfills
55
Q

if you increase resin in formulation, what happens

A

Increase coefficient of thermal expansion
Increase smoothness
Increase Shrinkage
Decrease Wear Resistance

56
Q

if you decrease resin in formula, what happens

A

Decrease coefficient of thermal
expansion
Decrease smoothness
Decrease Shrinkage
Increase Wear Resistance

57
Q

what are pure organic resin matrix with two or more sizes of pure inorganic fillers aded

A

hybrids (nano-hybrids)

58
Q

wht are the 2 distinct sizes of fillers

A
  1. Larger particles are “reinforced” with smaller particles that occupy the spaces between the larger particles
  2. The largest particle size range is used to define the hybrid type
59
Q

advantages of hybrid (nano-hybrid) composites

A

Favorable optical properties-translucent
Better wear resistance than microfills
Improved surface morphology
Radiopacity achievable
Hybrids have a lower polymerization shrinkage than microfilled resins, therefore adaptation to preparation walls
could be expected to be better

Coefficient of thermal
expansion is closer to
enamel than previous
versions (very similar
to silver amalgam
also)

60
Q

___ had a
greater filler
particle loading
to increase
strength, but it
also increased
opacity

A

Posterior
hybrids

61
Q

Development of
___ to
reduce the
complexity
involved in
selection of a
material
(considered a
nano-hybrid)

A

Total
Performance
Hybrids (TPH)

62
Q

what are considerations for using composites

A
  1. No galvanism
  2. Low thermal conductivity
  3. Adhesive bond to tooth
  4. Achieves maximum strength early
  5. Contains no mercury
  6. Shelf life can be prolonged by limiting exposure to heat and light
  7. Setting reaction is inhibited by a copal resin cavity varnish and eugenol (historical)
63
Q

resin advantages

A
  1. enhanced esthetics
  2. no bases for thermal protection
    3 no galvanism
  3. potential for adhesive bond to tooth
  4. achieves max strength early with light curing
64
Q

resin disadvantages

A
  1. Poorer wear resistance than amalgam? (but getting better)
  2. Microleakage-poor bond, bond breaks down
  3. Radio-opacity compared to tooth-better now
  4. Poor surface finish-??, better with newer composites
  5. Limited color stability-they do pick up stain especially as they wear
  6. Difficult to place (does NOT condense like amalgam!) Contact/Voids
  7. Placement time-I could have been
    done already if this was an amalgam!
  8. Technique sensitivity-High
  9. Pulpal irritation if placed within 1mm from the pulp-place a liner or base
  10. Uniform loss of restorative
    material
65
Q

how to advise patients of materials limitations

A
  1. 5/7/10 years or more
  2. use good judgement
  3. develop clinical skills
  4. good isolation - SA might be better option
  5. must keep up with advances in tech
66
Q

does available nanocomposite materials hold any significant advantage over hybrid composites in terms of strength and composite

A

no

67
Q

factors that affet wear

A
  1. B/L prep width
  2. Molar vs premolar
  3. Check occlusal scheme
    3a. Prefer minimal or no involvement with centric stops
    3b. Minimize abrasion of restorative material
  4. Examine tooth for cracks or craze lines
  5. REMEMBER POLYMERIZATION SHRINKAGE!
68
Q

2 types of post op sensitivity

A
  1. hot/cold
  2. biting pressure
69
Q

etiologies of post-op sensitivity

A
  1. etchant contact w dentin (hot/cold)
  2. toxicity of resin (hot/cold)
  3. polymerization shrinkag: 2-7% by volume (minimized by incremental build up)
70
Q
A

23 Operative (15 decks)

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