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CSA Dental materials > CSA tooth coloured materials 1 resin compo > Flashcards

CSA tooth coloured materials 1 resin compo Flashcards

1
Q

What are composites?

A

material with 2 phases:
o Inorganic glass filler (glass)
o Organic binder (polymer matrix)

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2
Q

How do we bond composite?

A

silane coupling agent

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3
Q

What does composite contain

A
  • camphorquinone- allows for lighting

- chemicals to stabilise and increase shelf life

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4
Q

What are the advantages of composites?

A
  • Good aesthetics
  • Conserves tooth structure & minimally invasive
  • Adhesion to tooth surface occurs via bonding system
  • Low thermal conductivity
  • Good alternative to amalgam now that minimata convention phasing it out
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5
Q

What are disadvantages of composite?

A
  • good moisture control is required
  • Polymerisation shrinkage
  • Lower wear resistance than amalgam
  • No chemical adhesion to tooth like GIC
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6
Q

What does polymerisation shrinkage lead to?

A

leads to marginal leakage, secondary caries, staining

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7
Q

What chemicals involved in placing composite?

A
  • Acid etch – opens prisms, exposes collagen & dentinal tubules
  • Bond – Forms hybrid layer between hydrophilic dentine & hydrophobic composite
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8
Q

What is chemical activation of composite?

A
  • Chemical  Organic amine + Organic peroxide

* Light  Camphorquinone + blue light (450-490nm) – more common method of setting

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9
Q

What is part 1 of the initiation stage?

A

camphorquinone splits under presence of blue light (photo initiator) & forms a free radical

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10
Q

What is part 2 of initiation stage ?

A

Free radical attacks weak pi bond in monomer of double bond and causes it to split open, this activated monomer

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11
Q

What is propagation ?

A

• activated monomer acts as radical and joins other monomers, breaking open their double bonds and forming a string of reactions to form very long chain of monomers (polymers)

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12
Q

What is termination ?

A

• 2 radicals (can be very long chain of monomers) collide and reaction ceases

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13
Q

What is shrinking?

A

distance between monomers decreases during polymerisation

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14
Q

What is polywave for setting?

A

more than 1 wavelength (450-490 nm) to set composite to ensure max. amount of monomer is polymerised

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15
Q

What happens when composite pulled away from enamel/dentine?

A

o Poor retention
o Staining
o Sensitivity
o Secondary caries

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16
Q

What types of monomers are there?

A
  • Bisphenol A glycidyl methacrylate (Bis-GMA) –
  • Urethane dimethylacrylate (UDMA)
  • Triethylene glycol dimethacrylate (TEGMA) –
  • All are dimethylacrylates
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17
Q

Why is Bis GMA?

A

Viscous due to benzene ring

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18
Q

What does TEGMA act as ?

A

diluent for Bis-GMA and makes composite easier to work with, increases polymer conversion more cross linking but more shrinkage

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19
Q

How are they all dimethylacrylates?

A

C=C on each end of molecule that makes polymerisation possible

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20
Q

What happens during light curing?

A

o Stresses form at bonding interface due to shrinking, as monomers cross link

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21
Q

When are stresses relieved during curing?

A

“gel point” > composite is no longer a liquid and loses ability to flow

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22
Q

What happens after gel point?

A

composite becomes unyielding/stiff and stresses is transferred to tooth

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23
Q

What is recommended to decrease stress transfer?

A

2mm curing depth

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24
Q

What does composite filler do ?

A

decrease strength & wear resistance of material

• Materials include: strontium glass, barium glass, quartz, borosilicate glass, ceramic, silica or prepolymerised resin

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25
Q

What is filler classified by?

A

material ,shape and size

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26
Q

What shape is filler?

A

regular or spherical

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27
Q

What are spherical shapes easier to do?

A

add to resin matrix & fill more space (less matrix/resin)

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28
Q

What does adding smaller filler particles do?

A

particles fills space between larger particles & take up more space  Less resin remaining so less shrinkage on curing

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29
Q

What do inorganic fillers reduce?

A

o Polymerisation shrinkage
o Thermal expansion
o Water sorption

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30
Q

What do inorganic fillers increase?

A

o Compression/Tensile strength
o Modulus of elasticity (Inc. stiffness)
o Abrasion resistance

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31
Q

What are different types of composites ?

A
  • Traditional
  • Microfill
  • Hybrid
  • Microhybrid
  • Nanohybrid
  • Nanofilled
32
Q

what leads to loss of polish with composite?

A

• Matrix wears away faster than filler

33
Q

What can toothbrushing do to composite?

A

• Leads to poor light refraction of material  Decreases aesthetics

34
Q

Microfilled composite benefit ?

A
  • Filler is smaller

* Matrix & filler wear at same time so reasonable aesthetics is achieved

35
Q

Nanofilled/hybrid composites ?

A

filler size was smaller than microfilled

• Most composites nanofilled or nanohybrid (including universal composites)

36
Q

What do coupling agents do?

A

bonds filler particles to the resin matrix (allows for transfer of stress)

37
Q

What is coupling agent in the form of?

A

organosilane
o siloxane end bonds to OH group in filler
o methacrylate end polymerises within resin

38
Q

What are advantages to coupling agent?

A
  • Inc. resin to filler surfaces

- Chemically coat filler surfaces & increase strength

39
Q

What are disadvantages to coupling agent?

A
  • Ages quickly & becomes useless

- Sensitive to water – water absorbed into material hydrolyses silane bond leading to filler attachment loss

40
Q

What are common coupling agents?

A

o Vinyl triethoxysilane

Methacryloxypropyltrimethyloxysilane

41
Q

What are general properties of composites?

A
  • Compressive strength
  • Tensile strength
  • Co-efficient of thermal expansion
  • Polymer shrinkage 3%
42
Q

What are the different types of composite used?

A
  1. Universal
  2. Flowable composites
  3. Packable composites
43
Q

What is packable composite ?

A

SDR and Bulkfil

44
Q

What is packable composite like?

A

o More firm/ viscous than flowable composite
o Large filler particles
o Very viscous so difficult to sculpt material
- voids commonly seen
o Less shrinkage

45
Q

How to use packable ?

A

don’t require placement of 2mm increments, light cure whole thing & place aesthetic composite on top

46
Q

What is flowable composute?

A

50-70% filler content by weight - have less viscosity

47
Q

What does Bis GMA monomer contain?

A

BPA

48
Q

What is shrinkage dependant on ?

A

cement type and thickness

49
Q

What does etching do?

A

decalcifies portions of enamel rods

o Calcium salts dissolved and interprismatic areas exposed for interlocking tag formation with bonding resin

50
Q

What do bonding agent form?

A

pure mechanical bond with tooth surface’s enamel

51
Q

What is benefit of etching?

A
  • Removes debris + surface enamel (5 micrometres)
  • SA increased by 10-20 folds
  • Increase free surface energy of enamel so exceeds surface tension of resin
  • Increases wetting
52
Q

What is volume of dentine?

A
  • 33% vol. of organic component (mainly type 1 collagen
  • 45% vol. of inorganic component (Mainly HAP)
  • 23% volume of water
53
Q

Why is hard for composite to bond to dentine?

A

high moist area

54
Q

What is aim of dentine bonding agents?

A
  • bond hydrophobic highly viscous material (composite) to hydrophilic surface
  • change surface properties of dentine to hydrophilic to hydrophobic
55
Q

How is smear layer formed?

A

cutting of dentine, it blocks the dentinal tubules

56
Q

What does smear layer do ?

A

o protect dentine/pulp from bacterial penetration – tubules blocked
o Prevents diffusion of dentinal fluid
o Impairs bond of composite to dentine
o Can harbour bacteria

57
Q

What is mechanism of bonding ?

A
  • replacement of minerals removed from hard tissues (by etch) by resin monomers
    o Bond mechanically interlocked with porosities created upon setting
58
Q

What is dentine hybrid layer formed at dentinal surface ?

A

due to hybridisation

59
Q

What is hybridisation ?

A

Infiltration of resin monomers (within bond) into collagen fibrillar matrix at superficial layer of demineralised dentine

60
Q

what causes mechanical bond?

A

resin tags

61
Q

Why must we gently dry after etch ?

A

over dry causes collagen meshwork to collapse – primer cannot penetrate onto collagen & bonding fails

62
Q

What are advantages of etching ?

A
  • Increased retention
  • Increases SA of dentine (more collagen is exposed)
  • Removes smear layer
  • Allows for penetration of bonding agent onto dentine (resin tags)
63
Q

What is priming with HEMA resin monomer ?

A

o solvent helps HEMA penetrate denial tubules easily & removes residual moisture

64
Q

What does priming help create?

A

penetrates tubules, helps create resin tags

65
Q

What does bonding do ?

A
  • Adheres to hydrophobic ends of HEMA & forms a hybrid layer/resin tags
  • Composite adheres to bonding surface
66
Q

What etch systems are there?

A

etch and rinse
self etch system
all in one system

67
Q

What etch and rinse primers are used?

A 
oAcetone based (e.g. All-bond 2, one step)
oEthanol based (e.g. optibond solo)
oWater based (scotchbond MP, Scotchbond 1)
68
Q

What is self etch system?

A
  • 2 step system
  • Acidic monomers simultaneously etch & prime dentine THEN BOND
  • No rinsing/ drying as no chance of scaffolding collapsing
69
Q

advantage of Self etch SE system?

A

takes less time & is less technique sensitive

70
Q

What is problem with acid organic monomers in SE?

A

Phosphoric acid better in opening enamel prisms & better at exposing collagen & dentinal tubules

71
Q

What does SE primer need to do ?

A

o Dissolve smear layer & decalcify intertubular dentine

o Whilst exposing superficial collagen & produce an effective hybrid layer

72
Q

Why isn’t SE system used much ?

A

unstable

73
Q

What is the all in one system?

A

• SE primer combined with bonding resin so 1 application

74
Q

problem with all in one system?

A

same problems as with SE system & must now also create a hydrophobic surface for composite to bond to
• acidity of bonding resin may interfere with setting of self-cure composite

75
Q

What components used in all in one system?

A

HEMA Phosphate
TEGDMA
HEMA
Additives- solvents, filler

CSA Dental materials (7 decks)

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