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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
do dental resins contain and leach bisphenol A
no- some sealants do thho
26
two types of polymerization
1. chemical cure (auto-cure 2 paste) 2. photo activation (VLC)
27
what is combined in chemical cured composite
tertiary amine and benzoyl peroxide
28
in chemically cured composited when combined, what happens
free radical are generated that start the polymerization of bis GMA
29
are chemicallly cured composite usually caries free
yes
30
what are activating compounds that generate free radicals in composites
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
what do free radicals originate from
ketone source such as diketones or aromatic ketons
32
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
free radical
33
do fre radical amines participae in the chemical reaxion as in the chemically cured materials
NO!!!
34
must the light source be specific?
yes
35
visible light activation using wavelengths greater than one
400 nanometers
36
what is the most effect light activation
468nm 480 nm
37
in terms of intensity, most modern LED lights have irradiance of what? some claim up to what?
at least 600 mW/cm2 some claim up to 3200 mW/cm2
38
what initiate the polymerizatin of bisGMA or urethane dimethacylate
free radicals
39
you must have proper what of light to initiate free radicals
proper wavelength
40
the ___ of light source must be high enough to initiate free radical
intensity
41
what are factors that influence cure
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
advantages of VLC resins
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
___ = organic = soft ___ = inorganic = hard
- resin = organic = soft - filler = inorganic = hard
44
what is the 1st step in wearing process
soft resin matrix begins to erode
45
what leads to a rough surface which is plaque retentive
porosity
46
what causes reduced compressive strength because restoration is not as dense
porosity in resin
47
why do almost all composited exhibit the same pattern of wear?
because they are two phase materials (resin + filler)
48
the end result and rate of occurrence to mechanism of wear is what?
different due to difference in filler particles and effectiveness which they are bound to the resin
49
as filled size decreased, more fillers can be incorporated to [increase or decrease] strength
increase hence, effects of plucking not as noticeable
50
what are problems that can occur with smaller particles
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
are silica filler radiopaque? explain
NOT radiopaque - must be coated with radiopaque coupling agents to improve radiodensity
52
is there better smoothness with smaller or larger particles?
smaller
53
are nanoparticles radiopaque
yes
54
characteristics of resin
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
if you increase resin in formulation, what happens
Increase coefficient of thermal expansion Increase smoothness Increase Shrinkage Decrease Wear Resistance
56
if you decrease resin in formula, what happens
Decrease coefficient of thermal expansion Decrease smoothness Decrease Shrinkage Increase Wear Resistance
57
what are pure organic resin matrix with two or more sizes of pure inorganic fillers aded
hybrids (nano-hybrids)
58
wht are the 2 distinct sizes of fillers
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
advantages of hybrid (nano-hybrid) composites
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
___ had a greater filler particle loading to increase strength, but it also increased opacity
Posterior hybrids
61
Development of ___ to reduce the complexity involved in selection of a material (considered a nano-hybrid)
Total Performance Hybrids (TPH)
62
what are considerations for using composites
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
resin advantages
1. enhanced esthetics 2. no bases for thermal protection 3 no galvanism 4. potential for adhesive bond to tooth 5. achieves max strength early with light curing
64
resin disadvantages
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
how to advise patients of materials limitations
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
does available nanocomposite materials hold any significant advantage over hybrid composites in terms of strength and composite
no
67
factors that affet wear
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
2 types of post op sensitivity
1. hot/cold 2. biting pressure
69
etiologies of post-op sensitivity
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

23 Operative (15 decks)

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