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Year 3 Operative and endo > Bonding of tooth coloured restoratives to tooth structure > Flashcards

Bonding of tooth coloured restoratives to tooth structure Flashcards

1
Q

example of

a. macromechanical retention
b. micromechanical retention
c. chemical retention

A

a. macromechanical retention: amalgam (undercuts)
b. micromechanical retention: composite/compomer
c. chemical retention: GIC

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2
Q

4 materials sometimes in proprietary pastes which used to be thought to affect etching potential

A
  • pumice
  • oil
  • glycerine
  • fluoride
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3
Q

4 possible etchant materials

A
  • 36% buffered ortho-phosphoric acid
  • 10% ortho-phosphoric acid
  • 10% maleic acid
  • 2.5% maleic acid
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4
Q

are etchant liquids or gels preferable? why?

A

gels - easier to control and see

both are equally effective

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5
Q

3 possible etch patterns

A

intra-prismatic
inter-prismatic
mixed

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6
Q

which etch pattern is more retentive

A

equal

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7
Q

depth of
a. aprismatic enamel removed from surface
b. prismatic enamel removed from core/periphery
c. resin infiltrated in to enamel
INTERPRET

A

a. aprismatic enamel removed from surface: 10um
b. prismatic enamel removed from core/periphery: 40um
c. resin infiltrated in to enamel: 25um

–> There is space under resin infiltrated area of enamel that we have etched

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8
Q

4 functions of etching enamel and applying an unfilled resin (bond)

A
  • micromechanical retention
  • reduces microleakage
  • eliminates marginal stain
  • reduces secondary caries
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9
Q

etching/washing time and why

A

15s (at least, usually 30s enamel 15s dentine)

at least same time washing otherwise calcium/phosphate ions precipitate on surface

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10
Q

what to do if salivary contamination occurs and why

A

re-etch enamel for 5 seconds

glycoproteins precipitate on to surface

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11
Q

3 ways to isolate teeth

A
  • rubber dam
  • cotton wool rolls
  • saliva ejector
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12
Q

why is rubber dam so important when etching/bonding

A

only way to stop humidity of pt breath

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13
Q

how to apply bonding resin

is it hydrophilic or hydrophobic

A
  • allow to penetrate pores for 20s (25um)
  • air dried
  • cured

hydrophobic

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14
Q

strength of composite bonding to a.enamel

b. dentine
c. GIC to dentine

A

a. 30mPa
b. dentine: 20-25mPa
c. 5-9mPa

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15
Q

4 ways bond efficiency composite-enamel can be reduced

A
  • clinical technique (lack of bevel)
  • contamination after etching
  • micro-cracks developing from cavity prep
  • unsupported/fractured enamel margins
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16
Q

is composite bonding better to enamel or dentine? why

A

better to enamel
dentine has different:
-composition SEE TABLE: 12xmore water and 2x more organic material
-structure: heterogenous structure, diff amounts of HA/ collagen in peritubular/intertubular dentine

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17
Q

what is the smear layer composed of

A

smeared HA crystals in matrix of partially degraded collagen matrix
outer layer: thick, lying on peri and inter-tubular dentine
inner layer: thin, consisting of plugs in dentinal tubules

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18
Q

thickness of smear layer with

a. water spray
b. tungsten carbide burs
c. diamond burs

A

a. water spray: 7um
b. tungsten carbide burs: 7um
c. diamond burs: 15um

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19
Q

when is the smear layer removed and why

A

etching. opens tubules, outward flow of fluid –> exposes collagen for bonding

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20
Q

4 potential adverse effects of removing smear layer

A
  • tissue fluid outflow
  • bacterial invasion
  • dentine sensitivity
  • adverse pulpal response
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21
Q

4 ideal properties of adhesive resin

A
  • non toxic to pulp
  • hydrophilic (due to dentinal tubule fluid)
  • good wetting of surface (low contact angle, enters pores)
  • long term stability
22
Q

bond strength of composite-dentine

A 
20-25mPa
BUT vary due to 3
-roughness of cut dentine surface
-site from which dentine selected
-source of dentine eg bovine/human
23
Q

3 components of dentine bonding resin

A

MRX

  • Methacrylate to bond with overlying composite
  • Radical (organic linking molecule)
  • X hydrophilic molecule that interacts with etched dentine surface (prisms organised so X is next to dentine)
24
Q

how does bond to dentine surface

A

-80% ENTANGLEMENT: remove smear layer and apatite crystallites –> collagen bundles in inter-tubular dentine exposed by etching –> resins flow 1.around collagen triple helix and polymerise 2.in to dentinal tubules by displaceing water and polymerises–> hybrid zone formed

-IONIC BDGMP
bonding to APATITE SALTS in etched dentine: ionic bonding to calcium ions in enamel/ dentine/ GIC via phosphated esters of bis GMA (penta, mdp)

-COVALENT HYDROPHILIC HAP
bonding to ORGANIC COLLAGEN MATRIX of etched dentine via hydrophilic resins: HEMA, PMDM, aldehyde

25
Q

what is MDP

A

new bis GMA phosphated ester used to bond ionically to calcium ions in enamel/dentine/GIC
newer, bigger, better than PENTA

26
Q

what does HEMA stand for

A

2-hydroxyl ethyl methacrylate

27
Q

what does PMDM stand for

A

pyro mellitic di-anhydride methacrylate

28
Q

describe the total etch technique

TABLE OF ETCH-PRIME-ADHESIVE METHODS

A
  • etchant gel 15-30s on enamel, less than 15s on dentine
  • wash >15s (at least as long as it was washed)
  • gently air dry 2-3s (do not desiccate dentine)
29
Q

function of acetone/alcohol in primer

A

water chaser: displaces water from collagen due to volatility

30
Q

name 2 1 step etch-primer-adhesive

A

Prompt L-pop

Xeno

31
Q

how does xeno work

A
  1. HYDROLYSIS OF PYRO-EMA:
    pyro-EMA (liquid B) + water –> hydrolysed pyro-EMA
    1 molecule:2 phosphates,4 methacrylate rings –> 2 molecules, 1 phosphoric acid 2 methacrylate groups
  2. NEUTRALISATION OF (hydrolysed) PYRO-EMA:
    hydrolysed pyro-EMA –> neutralised bc Ca ions from etched HA forms calcium phosphate w 2 phosphate ions
32
Q

desribe structure of dentine

a. before xeno
b. before evaporation of butanol/eater solvent
c. after removal of solvent

A

desribe structure of dentine

a. before xeno: smear layer + dentine
b. before evaporation of butanol/eater solvent: modified smear layer + dentine
c. after removal of solvent: adhesive layer, hybrid layer (resin, collagen, dentine tubules), dentine

33
Q

what are polyalkenoate cements

A

GIC

34
Q

how do GICs bond

A

dynamic ionic bond: polyalkenoic acid penetrates enamel/dentine
–> carboxyl group displaces PO4—
phsphate takes calcium ions to maintain neutral charge
–> combine with cement matrix to form ion-rich mineral ‘soup’ at interface of tooth-cement –> bound to tooth and cement
-eventual bonding to collagen via hydrogen bonding, metallic ion bridges polyacid carboxyl groups- amino acids of collagen
NOT MICROMECHANICAL

35
Q

what is the ‘soup’ of GIC bond

A

calcium/strontium phosphate/alkenoate in crystalline structure

36
Q

steps of GIC application

A

-smear layer removal (conditioning/etch): 10% polyacrylic acid for 10s–> washed with water 15s –> dried with oil free compressed air

37
Q

purpose of dentine conditioning in GIC

A

removes outer smear layer but leaves plugs in tubule ends –> limits fluid movement, allows dry surface

38
Q

strength of GIC

A

5-9mPa

39
Q

where GICs fail

A

between glass particles (within structure, not along ionic bond interface)

40
Q

size of filler particles in composite

a. traditional
b. microfilled

A

a. traditional: 10-20um

b. microfilled:10-50nm

41
Q

normal % setting shrinkage for composite

A

2-3%

42
Q

What are

a) silane
b) silorane
c) siloxane

A

a) silane: coupling agent in composite, forms covalent bond between filler and resin. Eg γMPTS
b) silorane: cyclic monomer, decreases setting shrinkage of composite to 1%
c) siloxane: backbone of silorane, along with oxiranes

43
Q

MATERIALS

define ductility

A

amount of plastic strain before fracture point

44
Q

define resilience and toughness

A

resilience: elastic region only; energy absorbed can be released again
toughness: plastic and elastic regions. total energy absorbed before fracture

45
Q

corrosion of

a. ceramics
b. metals/alloys
c. plastics

A

a. ceramics: dissolution
b. metals/alloys: oxidation
c. plastics: breakdown of polymer chains

46
Q

difference between stress and strain

A

stress= pressure (force/area)
strain= outcome of stress (change in length/original length)
these are directly proportional

47
Q

main setting reaction of compomers

A

polymerisation

48
Q

compare F content/release of GIC and compomer

A

compomer is less but it can be recharged eg toothpaste)

49
Q

main way compomer adheres to tooth

A

via bonding agent

50
Q

common resin of resin-modified GICs

A

HEMA

Year 3 Operative and endo (6 decks)

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