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Operative > Overview of Biomaterials- Amalgam and Intro to Composite > Flashcards

Overview of Biomaterials- Amalgam and Intro to Composite Flashcards

1
Q

Any substance, other than a drug, that can be used to treat,

augment, or replace any tissue, organ, or function of the body is a

A

biomaterial

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2
Q

•All dental materials which involve exposure to patients are

considered

A

biomaterials

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3
Q

4 Major Classes of Dental Materials

A

Metals and Alloys
Porcelains and Ceramics
Polymers
Composites

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4
Q

Polymers (2)

A

◦ Elastomeric (impression materials)

◦ Plastics (denture base, sealants)

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5
Q

Composites (1)

A

◦ Polymers with fillers

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6
Q

American Dental Association specifications (2)

A

◦ More than 10 specifications for dental materials, instruments, and equipment
◦ Restorative material specifications: related to material properties that should reflect clinical function

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7
Q

Restorative material specifications: related to material properties that should reflect clinical function (3)

A

◦ In vitro (in glass)- tested in the laboratory
◦ In vivo (in the living being)
◦ Extrapolation of in vitro data to in vivo conditions should be done with caution

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8
Q

skipped

Food and Drug Administration (4)

A

◦ Safety, Efficacy
◦ Protect the public from hazardous or ineffective medical materials and devices
◦ 2009 FDA reclassification
◦ Direct to Consumer Orthodontics?

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9
Q

2009 FDA reclassification (3)

A

◦ Reclassified amalgam from class I to class II
◦ Class I: lowest risk à Class III: highest risk
◦ Same as composites, crown and bridge alloys

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10
Q

Performance of all dental materials depends on their

A

atomic structure

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11
Q

Atomic structure determines (2) of materials

A

mechanical and physical properties

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12
Q

Types of interatomic bonds (2)

A

◦ Primary: Ionic, covalent, metallic

◦ Secondary: Hydrogen bonds, Van der Waals force

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13
Q

Primary Bonds: Ionic

A

Electrostatic attraction of positive and negative charges

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14
Q

Primary Bonds: Ionic

Involves — — between ions

A

electron transfer

◦ One becomes positive, one becomes negative ex. NaF)

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15
Q

Primary Bonds: Ionic

Properties (2)

A

◦ non-directional, strong bonds (100-200kcal/mole)

◦ No free electrons, good thermal and electrical insulator

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16
Q

Primary Bonds: Ionic examples (2)

A

◦ Ceramics, gypsum

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17
Q

Primary Bonds: Covalent

A

2 atoms share an electron

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18
Q

Primary Bonds: Covalent

Properties (3)

A

◦ Directional bonds (50-100kcal/mole)
◦ Low electrical and thermal conductivity
◦ Water insoluble

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19
Q

Primary Bonds: Covalent

Examples (4)

A

◦ Water, glass, polymers, composite

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20
Q

Primary Bonds: Metallic

A

Cluster of positive metal ions surrounded by a gas of electrons

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21
Q

Primary Bonds: Metallic

Properties (2)

A

◦ Non-directional bonds (100 kcal/mole)

◦ High electrical and thermal conductivity

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22
Q

Primary Bonds: Metallic

Examples (2)

A

◦ Amalgam and gold alloys

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23
Q

Classification of Material Properties (4)

A

Biological
Surface
Physical
Mechanical

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24
Q

Biological Properties

A

The biological response to a material when in contact with the human body

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25
Q

Biological Properties

Dental examples: (3)

A

◦ Allergies
◦ Pulp response
◦ Gingivitis, inflammation

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26
Q

Surface Properties

A

The unique properties of a material associated with its surface

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27
Q

Surface PropertiesExamples

A

Surface energy/tension; surface wetting

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28
Q

skipped

Dental examples of importance of surface wetting (6)

A 
◦ Making and pouring impressions
◦ Investing and casting
◦ Tooth pellicle
◦ Denture retention
◦ Fluoride treatment
◦ Adhesive bonding
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29
Q

Physical Properties

Depend on

A

the type of atoms and the bonding present in material

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30
Q

Physical Properties

Size/Shape Effect

A

no effect

-structure insensitive

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31
Q

Physical Properties

Examples (3)

A

◦ Optical (color, translucency, gloss)
◦ Electrochemical: Tarnish, Corrosion
◦ Thermal: Conductivity, Diffusivity, Coefficient of thermal expansion

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32
Q

Thermal conductivity

A

◦ Quantity of heat passing through 1cm thickness of material

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33
Q

Thermal diffusivity

A

◦ How quickly crown interior approaches temperature of exterior

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34
Q

skipped

Thermal Expansion Coefficient

A

(α)(20-50°C)
Α= final length-original length
original length x (*C final - *C original)

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35
Q

Mechanical Properties

A

Reaction of a material to the application of an external force

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36
Q

Mechanical Properties

Size/Shape effect

A

Size and shape of specimen affect properties

◦ Structure sensitive

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37
Q

Mechanical Properties

Applied force referred to as —

A

load

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38
Q

Stress

A

When load (force) applied to material, STRESS develops in response

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39
Q

Stress=

A

Load per unit area

◦ Measured in psi, MPa, kg/cm2

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40
Q

Fracture Stress- Strength

A

There is a limit to how much force a material can withstand before it breaks

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41
Q

Strength of material=

A

stress at fracture

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42
Q

Type of strength measured is dependent on

A

type of force applied

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43
Q

Types of Force/Stress (5)

A 
Tensile
Compressive
Torsion
Shear
Flexure
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44
Q

Tensile Strength- PULLING force

A

Measure of the stress necessary to fracture a material by 2

opposing forces directed away from each other

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45
Q

Lowest strength for most materials

A

Tensile Strength- PULLING force

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46
Q

Tension pulls the

A

atoms and structure apart

◦ Failure occurs at lower loads

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47
Q

Highest strength measure for most materials

A

Compressive Strength- PUSHING force

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48
Q

Compressive Strength- PUSHING force

A

Measure of the stress necessary to fracture a material by 2 opposing forces directed toward each other

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49
Q

Compression pushes

A

atoms and structure closer

◦ Usually require higher loads to cause failure

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50
Q

Torsion Strength- TWISTING force (4)

A 
Not relevant to direct or indirect dental restorations
Torque wrench (torsion) used to place dental implants
Torsion test of experimental dental implant-bone interface stability/strength of
osseointegration
Torsional fatigue of endodontic rotary files
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51
Q

Shear Strength- SLIDING force (3)

A

Typically, intermediate strength between compressive and tensile
Stress necessary to rupture a material by 2 opposing parallel forces directed
toward each other but not in the same plane
Clinical situation with shear force/shear strength- implant bone interface

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52
Q

skipped

Shear stress/strength at implant-bone interface (2)

A

Cylinder (press fit) implants: high shear

Threaded implants

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53
Q 
skipped
Threaded implants (2)
A

◦ Compressive stress below each thread (More ideal bone loading)
◦ Tension above thread, often see bone loss to level of 1st thread

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54
Q

Flexural Strength- BENDING force (2)

A

Measure of stress to cause failure in bending

Flexural stress/strength relevant in numerous clinical situations

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55
Q

3-point Bend test (2)

A

◦ Compressive load

◦ Combination of compressive & tensile stress

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56
Q

Flexural strength is vital due to occlusal load (3)

A

◦ On direct restorations (Amalgam and composite)
◦ Indirect restorations (Bridges/FDPs, single crowns, onlays)
◦ Removable prosthodontics (Palatal flex in maxillary denture)

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57
Q

Examples of DENTAL STRESS (2)

A

Protrusive movement

Posterior occlusion

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58
Q

Protrusive movement (2)

A

◦ Anterior teeth

◦ Flexure load on incisors

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59
Q

Posterior occlusion (3)

A

◦ Chewing = compressive load
◦ At marginal ridge contact areas
◦ At fossa areas

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60
Q

Occlusal Stress=

A 
Occlusal load (force)/
Occlusal contact area
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61
Q

TRIPODIZED occlusal contacts

A

◦ Allows distribution of occlusal load across
maximum area
◦ = minimized stress

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62
Q

Premature contact results in decreased —

A

AREA

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63
Q

Premature contact results in decreased AREA

occlusal force? occlusal stress?

A

◦ Patient’s occlusal force stays the same

◦ BUT OCCLUSAL STRESS IS INCREASED

64
Q

BUT OCCLUSAL STRESS IS INCREASED (2)

A

◦ Potential restoration failure

◦ Potential pain/discomfort for patient on biting

65
Q

Strain

A

The DEFORMATION that occurs in a material when force is

applied to the material

66
Q

Strain=

A

change in length (deformation)/

unit original length

67
Q

how are stress and strain interrelated?

A

◦ If you have one, you will have the other

68
Q

ELASTIC Strain

A

The TEMPORARY distortion of a material by applied force

69
Q

elastin strain:

Strain is BELOW THE

A

ELASTIC LIMIT

70
Q

elastic strain:

When force is removed, materials

A

reverts to original form

◦ Ex. Rubber band

71
Q

PLASTIC Strain

A

PERMANENT distortion of a material

72
Q

plastic strain:

Strain is

A

BEYOND the elastic limit
◦ Elastic portion of strain recovered
◦ Plastic portion of strain NOT recovered

73
Q

plastic strain:

When force is removed, shape

A

remains changed

◦ Ex: bending a paper clip

74
Q

Many benefits to amalgam: (4)

A

Easy to manipulate
Can be placed in its plastic state and carved before it hardens
Excellent physical properties
Cost effective (Including time to place)

75
Q

Excellent physical properties (4)

A

◦ Strong and predictable
◦ Self-sealing
◦ Due to corrosion over time
◦ = effective barrier against recurrent caries

76
Q 
Amalgam composition:
Kerr Contour Amalgam:
Ag --%
Sn --%
Cu: --%
--% spherical, --% lathe cut
A

41
31
28

70
30

77
Q

Amalgam- Composition

In capsule with powder, mixed with

A

liquid mercury in triturator

78
Q

Conventional Amalgam (2)

A

◦ Similar to G.V. Black’s original formula

◦ “low copper”

79
Q

High Copper Amalgam (3)

A

◦ Contain 9-30% copper
◦ Superior to conventional
◦ Presence of copper nearly eliminates gamma-2 phase, resulting in stronger restoration

80
Q

Phases of amalgam setting: (3)

A

Gamma
Gamma 1
Gamma 2

81
Q

Gamma

A

◦ Tin and silver react with mercury, forms silver-mercury (gamma-1) and tin-mercury (gamma-2)
◦ Strong, corrosion resistant

82
Q

Gamma-1

A

◦ Silver-mercury

◦ Weaker, susceptible to corrosion

83
Q

Gamma-2

A

◦ Tin-mercury

◦ Weakest, most susceptible to corrosion

84
Q

Add Copper=

A

creates a copper-tin phase (eta), eliminates tin-mercury gamma-2 phase

85
Q

Lathe (2)

A

◦ Outdated- particles formed by cutting block of alloy with a lathe
◦ Resulted in large, irregular particles

86
Q

Admixed (4)

A

◦ Lathe type particles mixed with small spheres
◦ Require more condensation force
◦ Most commonly used type of amalgam
◦ Low early strength (1-hour)

87
Q

Spherical (4)

A

◦ Spherical shape
◦ Higher early strength (1-hour) and higher 24-hour strength than Admixed
◦ May be more difficult to achieve interproximal contact
◦ Require less condensation force

88
Q

•Mercury to Alloy ratio (4)

A
  • Less mercury in final restoration is superior
  • Better strength and corrosion resistance
  • Proper condensation and finishing results in less mercury in final restoration
  • Admixed alloys ~50% mercury, Spherical alloys slightly less
89
Q

•Trituration (3)

A
  • Mixing the amalgam
  • Longer and faster trituration= sets faster
  • Follow manufacturer’s guidelines
90
Q

•Condensation (2)

A
  • Most critical variable

* Undercondensation is the most common error made by dentists

91
Q

•Carving and Finishing (1)

A

• Pre-carve and post-carve burnish recommended with high copper alloys

92
Q

Overwhelming evidence that supports the safety of amalgam (3)

A

◦ Mercury vapor is released in chewing
◦ No side effects at such low doses (Such as those from having amalgam restorations in your mouth)
◦ Dental Professionals exposed to more mercury vapor than non-dental professionals (Would expect more adverse health affects due to exposure, but that is not the case)

93
Q

Most of the “data” that suggests amalgam is

A

unsafe is anecdotal

◦ (Looks like they’re going after root canal treatment now)

94
Q

Amalgam has not been found to play a role in — diseases

A

neurodegenerative

95
Q

Why not remove amalgam due to mercury concerns? (3)

A

◦ Unwarranted loss of tooth structure
◦ Unnecessary expense
◦ Limited longevity when replaced with inappropriate tooth colored restoration

96
Q

Ways to classify composites (3)

A

◦ *Filler
◦ Handling
◦ Activation

97
Q

Curing-

A

lights and methods

98
Q

SKIPPED

History of Tooth-colored Materials

A 
Silicate cement, 1870’s, high solubility
Polymethyl methacrylate (PMMA), 1940’s
◦ Unfilled resin
◦ MMA resin mixed with PMMA polymer beads
◦ High polymerization shrinkage (7%),
High thermal expansion (90 ppm/°C)
◦ Marginal leakage
◦ Low strength
Composite resin, 1960’s
99
Q

Composite

Definition:

A

a physical mixture of 2 or more materials with superior

properties as compared to the individual components.

100
Q

Composite examples (4)

A

◦ Concrete: cement + gravel
◦ Fiberglass
◦ Dentin: collagen matrix + hydroxyapatite crystals
◦ Dental composites: Resin + Filler particles or Fibers

101
Q

Dental Composite Uses (5)

A
  1. Tooth-colored restorative material
  2. Bonding agents (filler may be present)
  3. Sealants (filled)
  4. Composite resin luting agents (cement)
  5. Resin-modified glass ionomer material
102
Q

Dental Composite:
— colored restorative material
Resin matrix phase reinforced by —
May be referred to as: (4)

A

Tooth
dispersed filler particle phase bound to the resin by a silane coupling agent
composite resin, resin composite, composite

103
Q

Dental Composite Components (6)

A

a. Resin matrix- Bis-GMA, TEGDMA
b. Filler particles - (Quartz, colloidal
silica)
c. Coupling agent
d. Activator-Initiator systemPhotoinitiator-camphorquinone
(sensitive to 470 nm visible light)
(Yearn, 1985)
e. Polymerization inhibitors
f. Optical modifiers

104
Q

Bis-GMA:

A

bisphenol A diglycidyl methacrylate

◦ Matrix in US products

105
Q

TEGDMA: triethyleneglycol dimethacrylate (3)

A

◦ ~30% added to Bis-GMA or UDMA
◦ diluting agent
◦ used to dilute the BisGMA and UDMA, which is very viscous

106
Q

Too much TEGDMA will however increase the amount of

A

polymerization shrinkage. Helps to promote
extensive cross linking and results in a matrix that is more resistant to degradation by solvents. TEGDMA
is another difunctional monomer.

107
Q

UDMA:

A

urethane dimethacrylate

◦ Matrix in European products, instead of Bis-GMA

108
Q

Filler Particles

A 
Crystalline silica (quartz),
Ba, Li, Al silicate glass, amorphous silica
109
Q

Filler Particles are dispersed in

A

resin matrix

110
Q

Filler Particles distribution varies depending on the

A

material
◦ filler loading %, expressed by weight or by volume
◦ filler size, and
◦ filler

111
Q

Benefits of Filler Particles (6)

A

1.Reinforcement of resin matrix:
◦ Increase hardness, strength, elastic modulus, and wear resistance
2.DECREASED polymerization shrinkage: ~10% to ~2%
3.DECREASED thermal expansion and contraction
1.Fillers don’t expand or contract
4.Improved workability, handling
5.DECREASED water sorption
6.INCREASED radiopacity (Barium, Strontium, Zirconium)

112
Q

Filler Size Distribution

Good distribution necessary to

A

incorporate maximum amount of filler

113
Q

Silane (4)

A

◦ Couples filler to resin matrix
◦ Allows stress transfer from flexible matrix to higher
modulus (aka less flexible) filler particle
◦Improves the mechanical properties
◦ Decreased water sorption along filler-resin
interface

114
Q 
Resin polymerization (free radical
addition rxn)
◦ Activation: 
◦ Initiation: 
◦ Propagation: 
◦ Termination
A

◦ Activation: Activator converts initiator into a free radical
◦ Initiation: Free radical initiator starts the addition reaction
◦ Propagation: continued polymer chain growth
◦ Termination

115
Q

Polymerization Inhibitor

Prevent

A

spontaneous polymerization when dispensed

116
Q

Polymerization Inhibitor

Stop polymerization from

A

brief room light exposure (reacts with free

radicals)

117
Q

Polymerization Inhibitor

Once the blue light is used,

A

all inhibitor quickly consumed= polymerization

chain reaction starts.

118
Q

Butylated hydroxytoluene (BHT)

A

◦ Food preservative, reduce oxidation

119
Q

Pigments:

A

metal oxides

120
Q

Opacifiers: (4)

A

◦ Titanium and aluminum oxide
◦ Control opacity or translucency
◦ Brand differences
◦ Dentin vs enamel composite shades

121
Q

Different ways to classify composites based on: (3)

A
  • Filler particle size and size distribution
  • Handling characteristics
  • Type of polymerization
122
Q

Classification by Filler Size and Distribution (4)

A
  1. Macrofill
  2. Midifill
  3. Microfill
  4. Hybrids
123
Q
  1. Hybrids (3)
A

a. Midi-Micro Hybrid (Midi- or Microhybrid)
b. Mini-Micro Hybrid (Microhybrid)
c. Mini-Nano Hybrid (Nanohybrid)

124
Q

skipped

Macrofill & Midifill Composites

A 
NOT USED MUCH TODAY
10-100 µm (macro)
1-10 µm (midi)
65-70 wt%
Large fillers
◦ Rough surface finish
Not good size distribution
◦ Increased inter-filler resin space, low wear resistance
Prone to staining
Brands: Adaptic (macro)
Concise (midi), still on market
125
Q

skipped

Microfill Composite

A 
0.01-0.1 µm particles, colloidal silica
40-60 wt%
◦ Due to large filler surface area, difficult to increase filler fraction, too viscous
Excellent finish, Best wear resistance
Weakest
Use for esthetic, low-stress sites
◦ Class III
◦ Layer over hybrid, kit systems
Brands: Durafill VS, Epic TMPT, Renamel, Heliomolar
126
Q

skipped

Hybrid Composites

A 
Midi-Micro Hybrid (First hybrids)
◦ Typically called Microhybrids
◦ Mix of midi and microfillers,
1-10 & 0.01-0.1 µm
◦ 75-80 wt%
◦ Improved surface finish
compared to macro and midi composites
◦ High strength
◦ Many of the of current materials are hybrid
◦ Z250, Z100, Herculite, TPH, APH, Point 4
127
Q

skipped

Mini-Micro Hybrid

A

a. Also called Microhybrids
b. Mix of mini and microfillers,
0. 1-1 and 0.01-0.1 µm
c. 80-85 wt%
d. Newer material
1) Smoother finish than midi-micro hybrid
2) Slightly lower strength
e. Clearfil APX, 4-Seasons, Miris, Vitalescence, Synergy, Tetric, EsthetX

128
Q

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Mini-Nano Hybrid (Nanohybrid)

A

◦ Nanometer: 10-9 Micrometer: 10-6
◦ Mix of mini, and nanofillers,
0.1-1 and 0.001-0.01 µm (1-10 nm)
◦ ~80 wt%
◦ Newest materials: Filtek Supreme Ultra (what is used in clinic), Premise,
TPH3 (what you use in lab), Simile
◦ Strength comparable to microhybrids and finish
equivalent to microfills
◦ Not all “nanocomposites” contain nanofiller (<100
nm), filler size reported in nm,
i.e. 300 nm

129
Q

Classification by Handling Characteristics (2)

A
  1. Flowable

2. Packable

130
Q

Flowable Composite

A

Low viscosity hybrid
reduced filler,
40-60 wt%, adapts better without handling ◦ Lower filler percentage, decreased modulus, increased flexibility
◦ Used under conventional composite at gingival floor of Class II
◦ Thought may compensate for polymerization shrinkage stress and reduce gap formation at gingival
floor; however, research does not support theory.
Many are not radiopaque

131
Q

Many are not radiopaque

◦ Big problem=

A

difficult to distinguish from recurrent

caries

132
Q

RADIOPACITY

Distinguish between

A

composite and recurrent caries

Barium, strontium, zirconium filler

133
Q

Flowable vs Hybrid

A

handling characteristic

filler characteristic

134
Q

Flowable (2)

A

◦ more shrinkage (is lower filled)

◦ less stress (has more resin to relieve the stress as it cures)

135
Q

Hybrid (2)

A

◦ less shrinkage (is higher filled)

◦ more stress

136
Q 
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Bulk fill
Newer technology- 
Need high output lights ~ 
Are highly filled with...
A

bulk fill
1000 Mw/cm2

more translucent fillers (which do not shrink) and less resin matrix (which shrinks)
◦ Higher filled have more stress because there is less resin to relieve the stress when it cures

137
Q

Classification by Polymerization

Activation (3)

A
  1. Self-cure, chemical activator
  2. Light-cure, blue light activator
  3. Dual-cure, combination of both
138
Q

Light-cure Composite

A 
One-paste system
Activator: Blue light (~470 nm)
Initiator:
◦ Camphorquinone (CQ), photoinitiator
◦ DMAEMA, alphiatic amine (accelerator)
139
Q

Light-cure Composite

Advantages (3)

A

a. Mixing not required, less porosity, increased
strength
b. Aliphatic amine (DMAEMA) more color stable
than self-cure aromatic tertiary amine
c. Better control of working time

140
Q

Light-cure Composite

Disadvantages (2)

A

a. Limited light penetration, ≤ 2mm increments, 20
sec
b. Blue light, retina damage – use orange shield

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Q

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Curing equipment factors (4)

A

◦ Bulb output, ≥ 300-400 mW/cm2 (11mm tip)
(Not below 300 mW/cm2, Not below 550 mW/cm2 for TPH3 or Filtek Supreme)
◦ Fiber-optic bundle breakage
◦ Tip contamination or damage
◦ Infection barrier

142
Q

Types of curing units: (4)

A
  1. Quartz-tungsten-halogen
  2. Plasma Arc
  3. Laser
  4. Light-emitting diodes (LED)
143
Q 
Light-cure Variables
Procedural factors (3)
A

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

144
Q 
Light-cure Variables
Restoration factors (3)
A

◦ Darker shades absorb light
◦ Smaller particles: increase light scatter
◦ Curing through tooth (decrease output)

145
Q

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Curing Lights: Quartz tungsten halogen
(QTH)

A

Usually tested with an 11 mm diameter light tip
◦ However, if a 3 mm diameter tip is used then the output can increase 8 fold which also can
heat up the tooth greater than the 5-8 degrees that can cause pulp cell death
Don’t touch the tip to the material being cured
At 6.0 mm distances from the restoration the output at the tip can be 1/3 what
it should be.
Never look directly at the light it can cause retinal damage.

146
Q

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Curing Lights: QTH– soft start or ramp cure

A

Starts low intensity, intensity increases
over time of cure
The theory is that a soft cure can allow
some stresses to be relieved in the
composite resin before it reaches the gel
stage; forms stronger long-chain polymers, decreases polymerization shrinkage

147
Q

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Light Curing: equipment factors
Factors that reduce light output (4)

A

◦ Frosting of bulb, Light reflector degradation, Fiber optic bundle breakage
◦ Tip contamination by resin buildup - lower output
◦ Sterilization problems - frosting the tip
◦ Infection control barriers - need longer curing time

148
Q

Classified by Activation:

Dual-cure Composite (4)

A

Both light and chemical activator/initiator systems present
Used under ceramic inlays, onlays, crowns
◦ Composite cement
◦ Accommodate thicker areas, light may not penetrate adequately

149
Q

Oxygen inhibited layer

A

~15 microns thick, on the outer layer which facilitates addition and wetting of subsequent
layers.
Just-cured composite may have 50% of the unreacted methacrylate groups to copolymerize
with the newly added material
Older restorations – will fully cure over time, do not have the unreacted methacrylate
groups
◦ Repair strength will be 50% of the original restoration. (Roughen with diamond)

150
Q

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Important Properties of Dental
Composite (7)

A
  1. Thermal expansion and contraction
  2. Sorption
  3. Surface finish
  4. Wear resistance
  5. Strength, elastic modulus
  6. Degree of Conversion
  7. Polymerization shrinkage
151
Q

With polymerization shrinkage, stress occurs at the composite-tooth
interface. (3)

A

◦ Stress level will vary, depending on the type of restoration
configuration factor, C-factor
◦ C-factor = bonded/unbonded surfaces
Highest stress is Class I restoration (~13-17 Mpa)

152
Q

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Gap formed between adhesive and tooth

A

~ 5-20 microns

153
Q

Managing Polymerization Shrinkage/Stress (5)

A 
Incremental placement
◦ ¯ bonded/unbonded, each increment
◦ ¯ C-Factor, ¯ polymerization stress
◦ Is shrinkage reduced?
◦ No, stress is reduced

Self-cure composite
◦ Slower polymerization rate
◦ Internal flow, compensates for shrinkage

Soft-start cure - ¯ initial light intensity
◦ Decreased stress, disadv. - maybe ¯ conversion

Light-directed polymerization
◦ Composite does not shrink toward the light

Low shrinkage composite: Filtek LS 0.9% shrinkage ◦ Silorane resin, ring opening

154
Q

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Bonding Agent
Primer/Adhesive Resin

A

◦ Resin matrix phase, unfilled
◦ Flows into etched dentin and enamel, micromechanical union
◦ Macro and micro resin tags, enamel
◦ 1-5 micron thick hybrid layer, dentin
◦ Co-polymerizes with the composite material
◦ Chemical union

155
Q

Universal adhesives

Chemistry game changer is

A

10-MDP Methacryloyoxy-decyl-dihydrogen-phosphate

156
Q

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10-MDP Methacryloyoxy-decyl-dihydrogen-phosphate (4)

A

Mechanism of action : A monomer that chemically interacts via ionic bonding to calcium in hydroxyapatite

Single bottle, no mix adhesive system

Can be used in total etch, self-etch or selective-etch mode (etch enamel only with phosphoric acid and rest of tooth with universal adhesive)

Monomer is a phosphate ester

Operative (11 decks)

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