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Pres/Res > Midterm - Biomaterials > Flashcards

Midterm - Biomaterials Flashcards

1
Q

Polymer Structure

A

many parts, may have amorphous or crystalline regions

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2
Q

Homopolymer

A

one type of building unit (can be linear or branched)

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3
Q

Copolymer

A

two or more building units (can be randomly arranged, in block formation, or grafted)

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4
Q

Croos-linked

A

contains “bridges” between linear molecules forming a 3-D network

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5
Q

Molecular Weight

A

polymers reported with average MW
increase MW/chain length - increased rigidity, strength, melting temps
increase cross links - changes MW, alters physical properties, increased rigidity, resistance to solvents

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6
Q

Elastic Deformation of Polymers

A

crystalline regions and cross-links help prevent plastic deformation and allow full recoil from the elastic formation
-after stretching with force, returns to original shape

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7
Q

Plastic Deformation of Polymers

A

permanent deformation, one chain slides over another and becomes relocated

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8
Q

Viscoelastic

A

time dependent recovery of elastic strain, length of deformation determines if it will return to original conformation or not, could be partially changed

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9
Q

Thermoplastic

A

soften by heating and solidify when cooling

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10
Q

Thermosetting

A

solidify during fabrication but do not soften by heating

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11
Q

Solvation Properties of Polymers

A

dependent on MW and cross linking

  • longer chain, higher MW dissolve slower
  • solvents break chains and take up space between them
  • crosslinking retards dissolution (makes it harder to dissolve)
  • swelling can effect fit, eventually shrinks
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12
Q

Polymerization

A

chemical linking of monomers to form high MW molecules

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13
Q

Types of Polymerization Reactions

A

Condensation

Addition

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14
Q

Condensation

A

step growth, components all become reactive simultaneously while producing low MW by products such as water (ex. impression materials)

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15
Q

Addition

A

addition of monomers sequentially in a chain that begins as an active venter via free-radical polymerization

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16
Q

Steps of Free-Radical Polymerization

A

induction (activation, initiation)
propagation
chain transfer
termination

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17
Q

Poly(Methyl Methacrylate) PMMA

A

used for denture base

thermosetting material example

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18
Q

Gutta Percha

A

used for filling canal space after root canals
natural polymer
classified as rubber (trans-isoprene)
thermoplastic material example

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19
Q

Polyurethane

A

used for orthodontic ligatures, modules, chains

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20
Q

Polycarbonate

A

plastic orthodontic brackets

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21
Q

Polyether, Polysulfide, Polyvinyl Siloxane

A

impression materials

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22
Q

Composite

A

a mixture of two classes of materials

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23
Q

Dental Composite

A

mixture of polymer (resin matrix) and ceramic (glass particle, fillers)

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24
Q

Dental Composite Components

A

matrix
filler
coupling agent

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25
Q

Matrix

A

a plastic resin material that forms a continuous phase (matrix) that binds the filler particles
dimethacrylate matrices
can have varying viscosities

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26
Q

Filler

A

reinforcing particles and/or fibers dispersed in the matrix (50-85% of composite weight)
Ceramics - silica, aluminum silicates strontium, zinc glass
Increases flexure, compressive strength, hardness, reduces polymerization shrinkage, reduces coefficient to thermal expansion, increases thermal conductivity

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27
Q

Coupling Agent

A

bonds the filler to the matrix (increases wear, fatigue, fracture resistance) treat the filler with agent before bonding to matrix
organic silicon compounds: silanes

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28
Q

Other Components of Dental Composites

A

initiators, activators, accelerators, inhibitors, pigments, opacifiers

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29
Q

Composite Classification

A 
activation mode (light, chemical, dual cured)
usage (anterior, posterior, universal)
filler characteristics
30
Q

Filler Characteristics

A

particle size - small, microfilled, hybrid, traditional (large)
distribution

31
Q

Ideal Composite

A

obtain the smoothness of microfilmed and the higher mechanical advantages of large particle composites

32
Q

Hybrid Composites

A

(1) microfill (0.04um)

2) second particle - small (0.1-2um), middle (0.1-10um), large (1-20um

33
Q

Hybrid Flower Variation

A
  • more filler = packable, used where condensation is needed

- less filler = flowable, less viscous, higher shrinkage, water sorption, thermal expansion

34
Q

Polymerization Considerations

A

oxygen inhibition layer
degree of conversion
polymerization shrinkage
contraction stress

35
Q

Oxygen Inhibition Layer

A

oxygen diffuses into the resin and oxidizes the free radicals into peroxides, reduced monomer reactivity and less polymerization
-susceptible to staining
-reduced polymerization –> less strength
4-40um thick, uppermost layer

36
Q

Degree of Conversion

A

the % of C=C converted to single bonds in addition polymerization (typically 50-70%)

  • residual monomer could leach if unreacted
  • higher % more strength
37
Q

Polymerization Shrinkage

A

polymer organizes the monomers and they occupy less space, shrink - generally 2-5%
-leakage, secondary caries at the margin

38
Q

Contraction Stress

A

a pull on tooth structure from composite shrinkage

  • more conversion = more stress = higher stress
  • cavity configuration factor (C factor) - ratio bonded to unbonded, the higher the more stress
39
Q

How to Lower Contraction Stress

A

formulation (large monomers, non-bonded fillers, adding inhibitors to slow curing, different monomer systems)
liners to act as stress absorbers
limit constraints and curing in increments
horizontal, vertical, oblique increments of placement
light cure protocols (ramp, step, pulse, concept) to slow polymerization to allow for flow before gel point

40
Q

Do low shrink composites reduce shrinkage stress?

A

no, stress will still be present

41
Q

Composite Properties: thermal expansion

A

higher than enamel and dentin

42
Q

Composite Properties: water absorption

A

less with more filler

43
Q

Composite Properties: wear

A

abrasion
attrition
marginal ditching
corrosion

44
Q

Composite Properties: translucency

A

varies, layer to achieve natural tooth look

45
Q

Composite Properties: shade

A

may shift with polymerization, differs between manufacturers, should shade select prior to rubber dam placement

46
Q

Composite Properties: finishing and polishing

A

smooth surface will increase longevity, reduce plaque accumulation
abrasive discs, strips, cutting carbide, diamonds, stone, rubberized abrasives, pastes and powders

47
Q

Composite Properties: failure

A

0-5 years: composite failure

6-17 years: secondary caries

48
Q

Bulk Fill Composite

A

placed in larger increments, less filler, thicker layers from light cure, get a composite cap at the top

49
Q

Indirect Composite Resin

A

made in labs
inlays, onlays, crowns, veneers, bridges
cured with light cure box/machine

50
Q

CAD/CAM

A

composite resin blocks used for milling in 3D scans

51
Q

MUSOD Direct Composite Resin

A 
TPH Spectra (sim lab) - universal, nano hybrid and microfiller components 
Synergy D6 (clinic) - universal, nano hybrid 
SureFil SDR (clinic eventually)
52
Q

Light Cure Types

A

Quartz-tungsten-halogen
LED (light-emitting diode)
Plasma Arc (PAC)
Argon Laser

53
Q

Light Cure Types: QTH

A

broad wavelength distribution

54
Q

Light Cure Types: LED

A

distinct, narrow wavelength distribution, or multiple distributions

55
Q

Light Cure Types: PAC

A

broad wavelength distribution

56
Q

Light Activation

A

Camphorquinone (CQ) - photoinitiator and amine activator

Note: the spectral emission of the light curing unit should overlap the absorption spectrum of the photo initiator

57
Q

Light-Curing Reciprocity Law

A

comparable material properties will result as long as the same radiant exposure is obtained
-radiant exposure=irradiancextime

58
Q

Irradiance Variability

A

the light exiting light-curing units is not necessarily uniform

59
Q

Light Attenuation

A

light intensity decreases with distance, cure in layers 2mm or less

60
Q

Light Angulation

A

restoration perpendicular to emitted light without touching - angles reduce energy delivery

61
Q

Light Cure Safety

A

need blue light filtering glasses, one second exceeds max daily exposure - cornea damage and accelerated retinal aging/degeneration
-high levels cause immediate, irreversible retinal damage

62
Q

Smear Layer

A

instrumentation blocks dentin tubules with debris and reduces permeability, very soluble layer that weak acids remove
0.5-5 um

63
Q

Bonding Agent Ingredients

A

etchant
primer
adhesive

64
Q

Etchant

A

conditioner, phosphorus acid solutions or gels

pH 1 to remove smear layer and mineral from around collagen fibrils in dentin

65
Q

Primer

A

hydrophilic monomers in a solvent

66
Q

Adhesives

A

hydrophobic, dimethacrylate
TEGDMA, Bis-GMA, UDMA
should be compatible with monomers used in primer and composite

67
Q

Enamel-Resin Bond

A

micromechanical bond with penetration of adhesive into etched enamel by primer

68
Q

Dentin Hybrid Layer

A

penetration of resin (monomers) into etched dentin around collagen fibrils
-50% resin, 50% collagen matrix

69
Q

Etch and Rinse

A

separate etch and rinse phase, sometimes called total etch

three step or two step

70
Q

Self Etch

A

non-rinse acidic monomers

two or one step

71
Q

MUSOD Bonding

A

Etch and Rinse 3 step (Optibond)

Self Etch 2 step (Clearfil)

Pres/Res (3 decks)

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