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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

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
how are smear layers created
Created by any mechanical cutting of dentine, and formatted as dentine debris of variable thickness
26
what do smear layers protect the dentine and pulp against
* penetration of bacteria
27
what other properties does the smear layer provide?
Eliminates diffusion of dentinal fluid and can impair the bond of composite to dentine
28
what 4 strategies have been used to achieve optimum bonding using the smear Layer
leaving the smear layer, removing the smear layer, or modifying it, or a combination of both.
29
what is the mechanism of bonding to enamel and dentin
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
what is the hybridisation
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
what is the hybrid layer
layer between collagen fibre and resin
32
what is etched dentine
when collagen fibres are exposed
33
what is etched dentine
when collagen fibres are exposed
34
what is the primer used for an when do we add it
- after etching - provides hydrophobic surface for resin - then we apply resin on top and bond
34
what is the primer used for an when do we add it
- after etching - provides hydrophobic surface for resin - then we apply resin on top and bond
35
why do we etch
* 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
why do we use primer
* 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
why do we use bonding adhesive
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
why do we use bonding adhesive
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
why is etch good for enamel
- gives us good bonding area
39
why is etch good fro dentine
removes, modifies the smear layer and exposes dentinal tubules
39
why is etch good fro dentine
removes, modifies the smear layer and exposes dentinal tubules
40
what are the 3 types of primers
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
what is the 3 step
etch primer resin
42
what is the 2 step
etch and one bottle
43
what are self etch primers
Without the need for rinsing, application time of self-etch adhesives is shorter and sensitivity is lower
44
For a self-etch primer to be effective, it must:
o Dissolve the smear layer o Decalcify intratubular dentine Penetrating to embed superficial collagen and produce an effective hybrid layer
45
what's the problem with self etching material
self etching material don't etch enamel well
46
what are self etch adhesives
combine the (self-etch) primer with the adhesive resin
47
what is challenge for self etch primers and adhesives
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
A pathway for successful bonding to dentine:
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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