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Year 2 CSA > Tooth coloured materials 1 > Flashcards

Tooth coloured materials 1 Flashcards

1
Q

how are fillers classified?

A

by material, shape and size

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2
Q

what shape are fillers?

A

irregular or spherical

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3
Q

why are spherical particles easier

A

easier to incorporate into a resin mix and to fill more space leaving less resin.

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4
Q

why do we add different size spherical fillers

A

One size spherical particle occupies a certain space.
Adding smaller particles fills the space between the larger particles to take up more space.

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5
Q

what does inorganic filler reduce

A
  • polymerisation shrinkage
  • water sorption
  • thermal expansion
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6
Q

what does inorganic filler increase:

A
  • compressive/ tensile strength
  • modulus of elasticity
  • abrasion resistance
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7
Q

what is the general role of the coupling agent

A

creates a chemical bond
between filler particle and resin matrix
transfers stresses

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8
Q

give eg of coupling agent

A

organisilane (bifunctional molecule)

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9
Q

how does organisilane work

A

siloxane end bonds to hydroxyl groups on filler
methacrylate end polymerizes with resin

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10
Q

why are coupling agents used

A

-improves adherence of resin to filler surfaces
- chemically coat filler surfaces and increase strength

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11
Q

what are disadvantages of silane

A

age quickly in a bottle and becomes ineffective

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12
Q

what are silanes sensitive to

A

water so the silane filler bond breaks down with moisture.
Water absorbed into composites results in hydrolysis of the silane bond and eventual filler loss.

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13
Q

eg of common silane agents

A

vinyl triethoxysilane
methacryloxypropyltrimethyloxysilane(MOPS)

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14
Q

what are flowable composites resins

A
  • percentage filler content by weight (50% to 70%) less than that of traditional hybrid composite resins= give lower viscosity
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15
Q

why are flowables bad?

A
  • they have lower filler volumes so they give increased shrinkage
    and wear with decreased strength
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16
Q

what are packable composites

A
  • AKA bulk placed composite
  • stiffer material
  • can be packed in like amalgam
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17
Q

what particle type do packable composites have

A
  • larger filler particles or even fibres to improve packing qualities
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18
Q

why are packable composites more difficult to sculpt and voids are more common

A

because they have higher viscosities

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19
Q

why do we need bonding agents to enamel

A

composites are hydrophobic
but bonding to enamel is easy as its 95% mineral HAP essentially a ceramic

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20
Q

what is etch made up of

A

an acid 30-40% phosphoric acid

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21
Q

ph of etch

A

0.2 which decalcifies in 5-8 secs

22
Q

what does etching do

A

decalcifies portions of enamel rods does this by
- the calcium salts becoming dissolved which exposes inter prismatic and prism areas for interlocking tag formation with the bonding resin when u apply it
- this is a mechanical bind not true adhesion

23
Q

what is the bond strength of etching

A

20mpa

24
Q

why is bonding to tooth difficult

A

dentine contains type 1 collagen and filler and loads of water
- moist conditions make it difficult for hydrophobic bonding

25
Q

how are smear layers created

A

Created by any mechanical cutting of dentine, and formatted as dentine debris of variable thickness

26
Q

what do smear layers protect the dentine and pulp against

A
  • penetration of bacteria
27
Q

what other properties does the smear layer provide?

A

Eliminates diffusion of dentinal fluid and can impair the bond of composite to dentine

28
Q

what 4 strategies have been used to achieve optimum bonding using the smear Layer

A

leaving the smear layer, removing the smear layer, or modifying it, or a combination of both.

29
Q

what is the mechanism of bonding to enamel and dentin

A

exchange process involving the replacement of minerals (removed from either of the hard dental tissues) by resin monomers. Once they set, they become micro-mechanically interlocked in the created porosities.

30
Q

what is the hybridisation

A

the infiltration of resin monomers into the collagen fibrillar matrix of demineralised dentine followed by polymerisation= it creates a molecular level mixture of adhesive polymers and dental hard tissues

31
Q

what is the hybrid layer

A

layer between collagen fibre and resin

32
Q

what is etched dentine

A

when collagen fibres are exposed

33
Q

what is etched dentine

A

when collagen fibres are exposed

34
Q

what is the primer used for an when do we add it

A
  • after etching
  • provides hydrophobic surface for resin
  • then we apply resin on top and bond
34
Q

what is the primer used for an when do we add it

A
  • after etching
  • provides hydrophobic surface for resin
  • then we apply resin on top and bond
35
Q

why do we etch

A
  • Improves the retention of the restoration
  • Increases the surface layer of the dentine
  • Removes the ‘smear layer’ from prep
  • Allows for penetration of bonding agent into dentin
  • Protect pulp exposures before using
36
Q

why do we use primer

A
  • Resin monomer, amphiphilic and low viscosity
    o Solvents are added to adjust primer viscosity and improve wetting
  • Improves the wettability of the prep – optimised for dentine than enamel
  • Penetrates etched dentin tubules
  • Applied in a thin layer, thinned further with air, and blotted
  • May require light curing
37
Q

why do we use bonding adhesive

A

Unfilled/lightly filled resin
* Adhesively bonds to collagen fibres in dentin that mechanically lock in (forms a
hybrid layer)
* Applied in a thin, uniform layer
* Light-cured for 10-20 seconds before dental composite is applied

37
Q

why do we use bonding adhesive

A

Unfilled/lightly filled resin
* Adhesively bonds to collagen fibres in dentin that mechanically lock in (forms a
hybrid layer)
* Applied in a thin, uniform layer
* Light-cured for 10-20 seconds before dental composite is applied

38
Q

why is etch good for enamel

A
  • gives us good bonding area
39
Q

why is etch good fro dentine

A

removes, modifies the smear layer and exposes dentinal tubules

39
Q

why is etch good fro dentine

A

removes, modifies the smear layer and exposes dentinal tubules

40
Q

what are the 3 types of primers

A

Sub-classified by the primer solvent
o Acetone based (such as All-bond 2 or One step)
o Ethanol based (such as Optibond Solo)
o Water based (such as Scotchbond MP or Scotchbond 1)

41
Q

what is the 3 step

A

etch
primer
resin

42
Q

what is the 2 step

A

etch and one bottle

43
Q

what are self etch primers

A

Without the need for rinsing, application time of self-etch adhesives is shorter and sensitivity is lower

44
Q

For a self-etch primer to be effective, it must:

A

o Dissolve the smear layer
o Decalcify intratubular dentine
Penetrating to embed superficial collagen and produce an effective hybrid layer

45
Q

what’s the problem with self etching material

A

self etching material don’t etch enamel well

46
Q

what are self etch adhesives

A

combine the (self-etch) primer with the adhesive resin

47
Q

what is challenge for self etch primers and adhesives

A

The acidity of the bonding agent can interfere with the setting of self-cure composites; it must create a surface that is compatible with hydrophobic restorative materials.

48
Q

A pathway for successful bonding to dentine:

A

wetting
infiltration to produce a ‘hybrid zone’
mechanical interlocking
stress resistanceUltimate goal is marginal integrity and sealing tubules to prevent ingress of bacteria

Year 2 CSA (6 decks)

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