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d1 spring - operative dentistry i > 2/8: Composite Resins > Flashcards

2/8: Composite Resins Flashcards

1
Q

When was Silicate cement used?

A

1870s

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2
Q

What is silicate cement?

A
  • high solubility
  • severe surface wear
  • low mechanical properties
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3
Q

When was polymethylmethacrylate (PMMA) used?

A

1940s

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4
Q

What is polymethylmethacrylate?

A
  • initially unfilled: high curing shrinkage
    -high thermal expansion and contraction
  • stress at the cavity margins (marginal leakage)
    -Later, filler added (without coupling agent-no
    bonded) = poor wear resistance and staining.
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5
Q

When was composite resin used?

A

1960s

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6
Q

What is composite resin?

A
  • BisGMA
  • fillers bonded (silane coupling agent)
    *Improved properties:
  • low thermal coefficient of
    expansion and dimensional change
    on setting
  • higher wear resistance
  • improved clinical performance
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7
Q

What is the definition of composite?

A

material containing at least two components (phases) with distinct chemical and physical properties that after blended, they show unique and superior properties as compared to the individual
components.

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8
Q

What are examples of composite?

A

Concrete: cement + gravel
Dentin: collagen matrix + hydroxyapatite crystals
Dental composites: Resin + Filler particles

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9
Q

What are tooth colored restorative materials?

A

composite resin, resin composite, composite

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10
Q

What is the resin matrix reinforced by?

A

dispersed filler particle phase bound to the resin by a silane coupling agent and an initiator-accelerator system

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11
Q

What are uses of composites?

A
  1. Tooth-colored restorative material (direct or indirect rest. technique)
  2. Bonding agents (filler may be present)
  3. Sealants (filled)
  4. Composite resin luting agents (cement)
  5. Resin-modified glass ionomer material
  6. Light-activated liner materials
  7. CAD/CAM blocks
  8. Resin endodontic sealers, etc.
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12
Q

How is dental composite packaged?

A

To protect against visible light (opaque) and moisture
* Plastic syringes
* Unit-dose capsules
* Dual paste syringes (dual curing – core build-ups)

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13
Q

What are components of composite?

A
  1. Resin matrix
  2. Filler particles
  3. Coupling agent
  4. Activator-initiator system
  5. Pigments and other components
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14
Q

What 3 things make up the resin matrix?

A

Bis-GMA
UDMA
TEGDMA

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15
Q

What are the filler particles of composite?

A

Crystalline silica (quartz), Ba, Li, Al silicate glass, amorphous silica

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16
Q

Where are filler particles disbursed and what does the distribution vary depending on?

A
  • dispersed in resin matrix
  • varies dependent on material (filler loading %, expressed by weight or volume & filler size/combination)
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17
Q

What are the benefits of filler particles?

A

Reinforcement of resin matrix
* Increase the mechanical and physical prop. (hardness,
strength, elastic modulus, and wear resistance)
DECREASED polymerization shrinkage
-The reduced shrinkage is proportional to the filler vollume
DECREASED thermal expansion and
contraction
* Higher filler amount reduces the thermal expansion
and contraction coefficients
Viscosity control
* Improved workability, handling
DECREASED water sorption
* Decreases the water sorption
INCREASED radiopacity
* Barium, Strontium, Zirconium

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18
Q

What does silane act as?

A

Interfacial bridge (strongly binds the filler to the resin matrix)

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19
Q

What are the benefits of silane as a coupling agent?

A
  • Better stress distribution
    between resin matrix and
    filler particles
  • Improves the mechanical
    properties
  • Decreased water sorption
    along filler-resin interface
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20
Q

Describe composites as chemicals

A

Monomers to be converted into polymers

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21
Q

What is the process of activating and initiating triggered by?

A

Free radicals (Chemical activation, heat or light)

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22
Q

What is the activator and initiator of chemical or self-curing composite?

A
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23
Q

What is the activator and initiator of light-cured composite?

A
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24
Q

What do polymerization inhibitors prevent?

A

Spontaneous polymerization

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25
Q

What do polymerization inhibitors stop?

A

Polymerization from brief room light exposure (reacts with free radicals)

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26
Q

What happens once the blue light is used on composite?

A

All inhibitor quickly consumed = polymerization chain reaction starts

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27
Q

What chemicals increase the shelf-life of composite resins?

A

Butylated hydroxytoluene (BHT)
- food preservative, reduce oxidation
Hydroquinone

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28
Q

What are pigments of optical modifiers?

A

Metal oxides

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29
Q

What are opacifiers?

A

➢ Titanium and aluminum oxide
➢ Control opacity or translucency (enamel vs. dentin)
➢ Brand differences

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30
Q

What are the different classifications of composites?

A

✓ Filler particle size and size distribution
✓ Handling characteristics
✓ Type of polymerization

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31
Q

How can you classify composite by filler size and distribution?

A
  1. Macrofill
  2. Midifill
  3. Microfill
  4. Hybrids
    a. Midi-Micro Hybrid (Midi- or Microhybrid)
    b. Mini-Micro Hybrid (Microhybrid)
    c. Mini-Nano Hybrid (Nanohybrid)
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32
Q

What kind of classification is not used much today?

A

Macrofill and midfill composites

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33
Q

What are macrofill and midfill composites?

A

✓ Large fillers (Rough surface finish)
✓ Fillers poorly distributed (Increased inter-filler resin space, low wear
resistance)
✓ Prone to staining

34
Q

What are microfill composites?

A

✓ Excellent finish
✓ Low mechanical and surface properties (hardness)
✓ Use for esthetic, low-stress sites (Class III, Layer over hybrid, kit systems)

35
Q

What are hybrid composites?

A
  • mix of midi and microfillers
    ✓ Improved surface finish as compared to macro and midi composites
    ✓ High strength
    ✓ Universal composites (anterior and posterior)
    Many of the of current materials are hybrid
36
Q

What are mini-micro hybrid aka microhybrid composites?

A

Mix of mini and microfillers
Newer material
1) Smoother finish than midi-micro hybrid
2) Slightly lower strength

37
Q

What are minni-nano hybrid composites aka naohybrids?

A

Mix of mini, and nanofillers
Newest materials
✓ Strength comparable to microhybrids and finish equivalent to microfills

38
Q

What are the classifications by handling characteristics?

A
  1. Packable (conventional/regular)
  2. Flowable
  3. Bulk fill
39
Q

What are the classifications of packable composite?

A

✓ Regular or conventional
✓ Medium viscosity
- Macrofill, microfill, hybrid, nanohybrid…
✓ Most widely used

40
Q

What is flowable composite classified as?

A

Low viscosity - reduced filler content
Lower filler percentage, decreased modulus, increased flexibility

41
Q

What is flowable composite used for?

A

Conventional composite at gingival floor of class II
- Thought may compensate for polymerization shrinkage stress and reduce gap formation at gingival floor.

42
Q

What is flowable composite not?

A

Not Radiopaque

43
Q

Why is the lack of radiopaqueness of flowable composite a problem?

A

Difficult to distinguish from recurrent caries

44
Q

What is the point of bulk fill composite?

A
  • To avoid incremental placement (“one bulk placement”)
    ✓ Highly filled with pre-polymerized particles
    ✓ Larger size fillers (reduces the light scattering)
    ✓ more translucent filler particles (increases the light penetration and polymerization)
    ✓ 5 mm increments
45
Q

What kind of lights are used for bulk fill?

A

High output lights

46
Q

What is condensable composite?

A
  • Packable with high viscosity
    ✓ Mini and midi fillers, >80 wt%
    ✓ Supposed to be handled like amalgam (amalgam alternatives in the market)
    ✓ Bulk cure inadequate
47
Q

What kind of composite is not well accepted? Why?

A

Condensable composite
- fractures at marginal ridges, changes on surface texture and color match

48
Q

Rank the types of composite from high to low viscosity

A
49
Q

What are the three classifications of polymerization activation?

A
  1. Chemical cure
  2. Light cure
  3. Dual cure
50
Q

What is the activator and initiator of chemical cure composite?

A

Activator: Aromatic tertiary amine
Initiator: Benzoyl peroxide (BPO)

51
Q

What are the advantages and disadvantages of chemical cure?

A

Advantage: bulk placement
Disadvantages: Mixing (incorporate bubbles, decrease strength);
No control of working time; Amine (not color stable)

52
Q

What is the activator and initiator of light cure composite?

A

Activator: Blue light
Initiator: Camphorquinone (photosensitive ~470 nm) and DMAEMA
(accelerator)

53
Q

What are the advantages and disadvantages of light cure?

A

Advantages:
-Mixing not required, less porosity, increased strength.
-Aliphatic amine (DMAEMA) more color stable than self-cure aromatic
tertiary amine
-Better control of working time
Disadvantages:
-Limited light penetration
- ≤ 2mm increments, 20 sec
-Blue light, retina damage – use orange shield

54
Q

What are the four steps of reaction of polymerization?

A
  1. Activation
  2. Initiation
  3. Propagation
  4. Termination
55
Q

What are procedural factors of light-cure variables?

A

-Exposure time
-Tip size: smaller tip= increase output, increase heat
-Distance: decrease Output when you increase distance

56
Q

What are clinical factors of light cure composite?

A

-Darker shades absorb light – affect light penetration
-Smaller filler particles: increase light scatter
-Curing through tooth decrease output

57
Q

What are types of curing units?

A
  1. Quartz-tungsten-halogen
  2. Plasma Arc
  3. Laser
  4. Light-emitting diodes (LED)
58
Q

What is the quartz tungsten halogen light system?

A

QTH source consists of a tungsten filament that is surrounded by a clear, crystalline quartz bulb containing a
chlorine-based halogen gas

59
Q

What kind of emission does the quartz tungsten halogen light system use?

A

Broad emission spectrum

60
Q

What are characteristics of the quartz tungsten halogen light system?

A
  • Cooling system is noisy
  • Relatively low irradiance (increase exposure between 30 to 60 s to polymerize 2-mm-
    thick of composite resin)
  • Heating in the output (pulp cell damage) – don’t touch the tip
  • Retinal damage (Never look directly at the light)
61
Q

What kind of emission do plasma-arc light (PAC) systems use?

A

Broad emission spectrum (390 to 510 nm)
High radiant power and high irradiance (to cure 2-mm thick composite resin in 3 to 5 s)

62
Q

What are characteristics of plasma-arc light (PAC) systems?

A
  • expensive
  • Noisy, large, not portable, cannot be battery operated
  • Become less popular with the introduction of LED curing lights
63
Q

What are characteristics of the argon-ion laser?

A

✓ High irradiance in only 10 seconds (could rapidly cure dental resins)
✓ Produces several intense and narrow emission peaks
✓ Argon-Ion Lasers are expensive
✓ Become less popular with the introduction of LED curing lights

64
Q

What are advantages of the light-emitting diodes (LED)?

A
  • solid state, lightweight, battery driven
  • more efficient (at least 10 times more than QTH)
    -extremely long working life
65
Q

What are factors reducing output?

A
  1. Degradation (light reflector, fiber optic bundle, bulb)
  2. Tip contamination by resin buildup - lower output
  3. Sterilization problems - frosting the tip
  4. Infection control barriers - need longer curing times
66
Q

What is the oxygen inhibited layer?

A

~15 microns thick, on the outer layer which facilitates addition and wetting of subsequent layers

67
Q

What are deficient polymerization problems?

A
68
Q

What are important properties of dental composite?

A
  1. Polymerization shrinkage and stress
  2. Wear resistance
  3. Surface finish
  4. Marginal infiltration
  5. Water Sorption
  6. Radiopacity
  7. Color stability
69
Q

What does polymerization yield?

A

Shrinkage
Consequently, stress occurs at the composite-tooth interface
✓ Stress level will vary, depending on the type of restoration
configuration factor, C-factor

70
Q

What is C factor?

A

Bonded/unbonded surfaces

71
Q

What happens with higher c-factor?

A

Higher stress

72
Q

What is failure at the interface reduced by?

A

Reduced by effective bonding and lower c-factor

73
Q

Higher filler amount =

A

Higher wear resistance

74
Q

Lower filler size =

A

Higher surface finish

75
Q

What is marginal infiltration?

A

✓ Decreased with improvement of adhesive systems
✓ Failure “gap” between tooth and composite
✓ Secondary caries, marginal staining and fracture, post-operative sensitivity

76
Q

What is water sorption?

A

✓ Lower filler amount, higher water sorption = higher expansion
✓ BisGMA and TEGDMA: higher sorption as compared to UDMA

77
Q

What is radiopacity important for?

A

Distinguish carious tissue and marginal adaptation, air bubbles (defects)

78
Q

What are adhesive systems for bonding agents?

A

agents that bond micromechanically
or/and chemically the restorative material (or luting
agent) to tooth substrate through an interface

79
Q

What does acid etching do?

A

◦ To remove the minerals from dental substrate
(micro-retentions on enamel and exposing the
collagen matrix)
◦ Allowing the adhesive infiltration

80
Q

What is the mechanism of action of universal adhesives chemical bonding?

A

A phosphate
monomer that chemically interacts via ionic
bonding to calcium in hydroxyapatite

81
Q

What are the steps of the bonding procedure at UMKC?

A
  1. Acid etch
  2. Rinse
  3. Vivapen
  4. Light cure for 10 sec
  5. Place resin

d1 spring - operative dentistry i (12 decks)

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