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Operative Lecture > Biomaterials: Composite Resin > Flashcards

Biomaterials: Composite Resin Flashcards

1
Q

What tooth-colored materials were around in 1870s?

A

silicate cement
- high solubility
- severe surface wear
- low mechanical properties

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2
Q

What tooth-colored materials were around in 1940s?

A

polymethylmethacrylate (PMMA)
- initially unfilled: high curing shrinkage
- high thermal expansion and contraction
- stress at the cavity margins

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3
Q

What tooth-colored materials were around in 1960s?

A

composite resin
- fillers bonded
- improved properties: low thermal coefficient of expansion, higher wear resistance, improved clinical performance

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4
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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5
Q

What do you use composite for?

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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6
Q

What are the components of dental composite?

A
  1. Resin matrix
  2. Filler particles
  3. Coupling agent
  4. Activator-initiator system
  5. Pigments and other components
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7
Q

What are the different types of resin matrix?

A
  • Bis-GMA (most used)
  • UDMA
  • TEGDMA
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8
Q

What are the characteristics of filler particles in composite resin?

A
  • crystalline silica quartz (Ba, Li, Al silicate glass, amorphous silica)
  • dispersed in resin matrix
  • distribution varies
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9
Q

What are the benefits of filler particles?

A
  • Reinforcement of the resin matrix
  • decreased polymerization shrinkage
  • decreased thermal expansion
  • viscosity control
  • decreased water sorption
  • increased radiopacity
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10
Q

What does the coupling agent (silane) allow for?

A

better stress distribution between resin matrix and filler particles

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11
Q

What are the two types of initiators?

A

for chemical/self-cure
- benzoyl peroxide

for light-cured
- camphoroquinone
- DMAEMA (amine)

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12
Q

What are the two types of activators?

A

for chemical/self-cure
- tertiary amine

for light-cured
- blue light (465 mn)

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13
Q

What is the benefit of polymerization inhibitor?

A

✓ Prevent spontaneous polymerization
✓ Stop polymerization from brief room light exposure (reacts with free radicals)
✓ Increase the shelf-life of the composite resins

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14
Q

What are examples of polymerization inhibitor?

A

butylated hydroxytoluene (BHT)
hydroquinone

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15
Q

What are some optical modifiers for composite resin?

A
  • pigments: metal oxides
  • opacifiers: titatnium/aluminum oxide
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16
Q

What are the different filler sizes?

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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17
Q

What are the characteristics of macrofill/midifill?

A
  • large fillers
  • poorly distributed
  • prone to staining
  • not used much anymore
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18
Q

What are the characteristics of microfill?

A
  • excellent finish
  • low mechanical and surface properties
  • esthetic, low-stress areas
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19
Q

What are the characteristics of hybrid composite filler Midi-Micro hybrid?

A
  • improved surface finish (compared to macro/midi)
  • high strength
  • many of the current materials
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20
Q

What are the characteristics of mini-micro hybrids?

A
  • smoother finish
  • slightly lower strength than midi-micro hybrids
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21
Q

What are the characteristics of mini-nano hybrids?

A
  • newest material
  • strength is comparable to mini-micro hybrids
  • finish is equivalent to midi-micro hybrids
22
Q

What are the three classes of composite based on handling characteristics?

A
  1. Packable (Conventional/Regular)
  2. Flowable
  3. Bulk fill
23
Q

What are the characteristics of packable composite?

A

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

24
Q

What are the characteristics of flowable composite?

A

✓ Low viscosity - reduced filler content; 40-60 wt%, adapts better without handling
✓ Lower filler percentage, decreased modulus, increased flexibility
✓ Used under conventional composite at gingival floor of Class II
Many are not radiopaque
✓ Big problem= difficult to distinguish from recurrent caries
✓ Distinguish between composite and recurrent caries
✓ Barium,strontium, zirconium filler

25
Q

What are the characteristics of bulk fill?

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
✓ Need high output lights ~ 1000 mW/cm2

26
Q

What are the characteristics of 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
✓ Not well-accepted

27
Q

What are the advantages and disadvanges of chemical cure?

A

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

28
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

29
Q

What are the steps of the polymerization reaction?

A

activation
initiation
propagation
termination

30
Q

What are some light-cure variables?

A
  • exposure time
  • tip size: smaller tip = increase output, increase heat
  • darker shades absorb light more
  • smaller filler particles increase light scatter
  • curing through tooth decreases output
31
Q

What happens to the output when you increase the distance when light-curing?

A

decreased output

32
Q

What are the different types of curing units?

A
  1. Quartz-tungsten-halogen
  2. Plasma Arc
  3. Laser
  4. Light-emitting diodes (LED)
33
Q

What are the characteristics of the quartz-tungsten-halogen (QTH) light curing machine?

A

✓ QTH source consists of a tungsten filament that is surrounded by a clear, crystalline quartz bulb containing a
chlorine-based halogen gas.
✓ Broad emission spectrum (~400 to 500 nm)
✓ Cooling system is noisy
✓ Relatively low irradiance
✓ Heating in the output (pulp cell damage) – don’t touch the tip
✓ Retinal damage (Never look directly at the light)

34
Q

What are the characteristics of the plasma-arc light (PAC) light curing machine?

A

✓ Broad emission spectrum (390 to 510 nm)
✓ High radiant power and high irradiance
✓ PAC lights are expensive
✓ Noisy, large, not portable, cannot be battery operated
✓ Become less popular with the introduction of LED curing lights

35
Q

What are the characteristics of the argon-ion laser light curing machine?

A

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

36
Q

What are the characteristics of the light-emitting diodes (LED) light curing machine?

A

✓ Introduced in the 1990’s
✓ Many advantages:
- solid state, lightweight, battery driven
- more efficient (at least 10 times more than QTH)
-extremely long working life
✓ First and second generation: relatively narrow emission
spectrum
✓ Third generation: Multiwave, Multipeak, Polywave

37
Q

What can reduce the light curing 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
38
Q

What is the oxygen inhibited layer?

A

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

39
Q

What are the problems with deficient polymerization?

A

marginal staining
microleakage
secondary caries
enamel microcracks
disadaptation
increased wear
postoperative sensitivity
bulk fracture of the restoration
release of chemicals

40
Q

What are the 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
41
Q

What is the C factor?

A

Stress level will vary, depending on the type of restoration configuration factor

42
Q

What does incremental placement do to the C factor?

A

decrease
- stress is reduced

43
Q

What is important about wear resistance?

A

✓ Biofilm formation = bacterial acids = soften of resin matrix
✓ Higher filler amount = higher wear resistance

44
Q

What is important about surface finish?

A

✓ Type and size of filler
✓ Lower filler size = higher surface finish

45
Q

What is important about marginal infiltration?

A

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

46
Q

What is important about water sorption?

A

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

47
Q

What is important about radiopacity?

A

✓ Important to distinguish carious tissue and marginal adaptation, air bubbles (defects)

48
Q

What is important about color stability?

A

✓ Color change after 2-5 years
✓ Food, smoking, beverages

49
Q

What are bonding agents?

A

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

50
Q

What is the purpose of acid etching?

A

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

51
Q

What is the mechanism of action of the universal adhesives?

A

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

Operative Lecture (17 decks)

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