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CSA Dental materials > CSA glass polyalkenotes > Flashcards

CSA glass polyalkenotes Flashcards

1
Q

how do we activate glass polyalkenoate?

A

Chemical activation

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2
Q

what is light AND chemical activation for?

A
  • Fissure sealants
  • Dental composites
  • Polyacid Modified Resins
  • Resin modified polyalkenoate
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3
Q

What are glass polyakkenoates aka glass ionomer cements?

A

composite & comprised of 3 distinct components in the reacted (set) material
o Polymer
o Silica gel
o Ionomer glass

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4
Q

What is the setting reaction?

A

ionomer glass & polyacrylic acid packaged together & are mixed with liquid (water)

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5
Q

What is the chemical activation once powder and liquid have mixed?

A

polymer chains acidic:

o Polyacid + Base > Polysalt + water

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6
Q

What are polysalts formed made into?

A

cohesive solid glass polyalkenoate cements

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7
Q

What are the specifics of setting reaction ?

A
  1. acid dissolves in water forming a viscous aqueous solution with glass dispersed
  2. H+ ions displaced from polyacid then displace cations on surface of glass
  3. cations migrate away and react with negatively charged polymer ions
  4. modified glass surface becomes silica gel; reaction continues as further ions diffuse through gel to surface
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8
Q

What happens when cations migrate away and react with negative polymer ions?

A

Cross linking them to become long polymer chains (Polysalts)

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9
Q

When does GIC reach full strength?

A

after 1 week, petr. jelly used to reduce cracking after a week

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10
Q

What does GPAC do?

A
  • Releases fluoride
  • GPAC acts a fluoride sponge
  • GPAC reacts with calcium ions in tooth
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11
Q

What does GPAC releasing fluoride react wtih?

A

neighbouring HAP tooth tissue forming fluroapatite, has greater acidic resistance and prevent secondary caries

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12
Q

What does GPAC fluoride sponge do?

A

absorbing fluoride from toothpaste etc. and then release it over a longer period of time

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13
Q

What happens when GPAC reacts with calcium ions?

A
  • create direct chemical bond with GPAC & tooth

- seals the surface between the 2 materials, preventing entry of microbes

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14
Q

How to improve strength of GPAC?

A
  • hybrid of GPAC known as cermets

- copolymer of polyvinyl phosphoric acid + polyacrylic acid

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15
Q

What are disadvantages of GPAC?

A
  • Wear resistance is poor
  • too opaque
  • grey appearance of cermets
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16
Q

What can’t GPAC be used on?

A

occlusal surfaces for restorations

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17
Q

What are the advantages of GPAC?

A
  • No cavity prep
  • used as intermediate material > under amalgam or composite
  • Good as a luting cement
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18
Q

how is structure of dental composites different to GPAC?

A

glass in glass polyalkenotes is inert & plays no part in the addition reaction

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19
Q

Why is inert filler included in structure?

A
  1. Decreases shrinkage of polymer & shrinkage of composite overall
  2. Decreases swelling due to water absorption & chance of staining.
  3. Decreases thermal expansion > Dec risk of tooth fracture >Dec sensitivity
  4. Fillers improve strength, increase young’s modulus, increase wear resistance, better aesthetics of composite
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20
Q

What does a decrease in shrinkage of polymer do?

A

decreases risk of tooth fracture

21
Q

What does high coefficient of polymer mean?

A

o Decreases sensitivity caused by fluid movement in tubules

22
Q

What is microfilled composite?

A

o Smaller filler used to improve surface finish

o incr. filler SA, more matrix required to produce workable product

23
Q

What is hybrid composite?

A

o Mixture of conventional (5-10 micrometres) intermediate and small (0.04 micrometre) fillers
o 75-85% by volume of filler

24
Q

What is the polymer matrix?

A

Bisphenol glycidyl methacrylate (Bis-GMA) blended with urethane dimethacrylate (UDMA)

25
Q

What are drawbacks of composites?

A
  • Blue light used to cure so built up incrementally
  • Blue light bulb ages 
  • Material is hydrophobic so needs to be dry
  • Doesn’t bond to teeth so bonding agent required
  • Polymerisation shrinkage
26
Q

Why do we build up incrementally ?

A

reduce shrinkage and RO fracture

27
Q

What does polymerisation shrinkage lead to?

A

bacterial ingress so prone to recurrent caries

28
Q

What are current bonding agents?

A

unfilled resin which is diluted with a carrier which may be hydrophilic

29
Q

What does etch remove?

A

SMear layer created by cavity prep

30
Q

What is smear layer?

A

layer of debris caused by cutting into dentine which blocks tubules

31
Q

How is mechanical bonding achieved ?

A

tags forming, enter dentinal tubules

32
Q

Whys is silaine coupling agent added to surface of glass filler?

A

filler & matrix will bond

33
Q

What are resin modified polyalkenoates?

A

light cured glass ionomers where polyacid modified to have functional groups

34
Q

How is RMGIC different to GPAC?

A

polished immediately after light activated reaction therefore less susceptible to desiccation

35
Q

What is HEMA Hydroxyethyl methacrylate used for

A

addition polymerisation cross links

36
Q

What are polyacid modified resins (compomers) ?

A

o Dental composite precursors changed so have acid groups

- material is light activated

37
Q

What happens once compomers take in water from saliva?

A

causes disassociation of acid groups

  • acid base reaction is initiated with ionomer glass (Secondary reaction)
  • primary reaction isaddition polymerisation reaction
38
Q

What are advantages of compomers?

A

Superior aesthetics to GPAC

Fluoride released

39
Q

What are disadvantages of compomers?

A

System takes in oral fluids  risk of staining

40
Q

When is strength higher ?

A

with materials of high addition polymerisation reaction occurring

41
Q

What are advantages of composites?

A
  • Good strength & good aesthetics

- Command set ability

42
Q

What are disadvantages of composites?

A
  • Poor bonding to tooth tissue

- No fluoride release

43
Q

When are fissure sealants used?

A

seal vulnerable fissures on occlusal surfaces of posterior teeth and prevent ingress of microbes

44
Q

IS FS similar to composite?

A

no filler is present FS more flowable

45
Q

What is FS unable to do?

A

bond directly to enamel and requires etch

46
Q

An advantage of GPAC?

A

doesn’t require etch

47
Q

Why are FS pigmented?

A

pigmented (for aesthetics) or clear for clinician to monitor caries formation underneath

48
Q

What source of fluoride can be used under FS?

A

3M ESPE incorporated TBATFB

CSA Dental materials (7 decks)

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