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DENTAL MATERIALS > 7 - Luting Cements > Flashcards

7 - Luting Cements Flashcards

1
Q

2 types of restorations? describe how each is done + give 3 examples of each

A
  • direct restoration: material placed in/on a cavity which hardens into a solid (chemically or by light curing)
    e. g. amalgam, composite, GI restorations
  • indirect restorations: a solid object made outside of the mouth which is placed in/on a prepared tooth
    e. g. crowns, bridge, veneer, inlays, onlay
  • can be provisional/temporary or definitive
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2
Q

die relief - helps to do what?

A

die relief helps to accommodate the thickness of luting cements

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3
Q

what is a luting cement? what are its 2 main purposes?

A

it is a material used for the

1) retention of indirect restorations, and to
2) seal the space between restoration and the tooth

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4
Q

choice of luting cement depends on?

A
  • choice of luting cement depends on the type of restoration being cemented
    1. provisional/temporary?
    2. material of indirect restoration:
  • metal? ceramic? composite?
    3. type of restoration?
  • veneer? resin retained bridge? conventional bridge?
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5
Q

2 types of luting cement?

A
  • active luting material

- passive luting material

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6
Q

active luting material: what does it do? and what are its roles?

A
  • it bonds to the tooth and the restoration
  • helps with retention
  • provides a marginal seal
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7
Q

passive luting material: what does it do? how does it bring retention?

A
  • it fills the gap between tooth and restoration
  • there is no bond between tooth and restoration, instead retention is brought about by method of tooth tooth preparation
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8
Q

what are the methods of tooth preparation?

A
  • taper
  • preparation height
  • surface roughness
  • mechanical interlocking
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9
Q

general ideal properties of a luting cement?

A
  • biocompatible
  • retention
  • mechanical properties
  • marginal seal
  • low film thickness
  • ease of use
  • pseudoplastic
  • radiopacity
  • aesthetics: ceramic restorations
  • inhibit plaque accumulation
  • antibacterial
  • clear up of excess
  • good shelf life
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10
Q

ideal luting cement: importance of biocompatibility?

A

able to contact with tooth tissue and periodontal tissues

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11
Q

ideal luting cement: importance of retention?

A

additional bonding for active luting cements, preparation morphology and mechanical interlocking of irregularities for passive luting cements

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12
Q

ideal luting cement: examples of ideal mechanical properties?

A

high tensile strength, fracture toughness, fatigue strength, wear resistance

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13
Q

ideal luting cement: importance of marginal seal?

A

low solubility. advantageous for active luting, reduced hypersensitivity

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14
Q

ideal luting cement: importance of low film thickness?

A
  • allows full seating of restoration

- good marginal adaptation

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15
Q

ideal luting cement: in what ways should it be easy to use?

A
  • powder:liquid ratios

- working and setting times

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16
Q

ideal luting cement: describe how it should be pseudoplastic?

A

it should coat the fit surface of the restoration without slumping, but it should also flow readily under pressure on fitting

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17
Q

ideal luting cement: how can it inhibit plaque accumulation

A

it should be easy to polish

it should eliminate the air inhibition layer in resin composites

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18
Q

passive luting cements: 4 examples? what are they based on?

A
  • zinc phosphate
  • zinc polycarboxylate
  • glass ionomer luting materials
  • resin modified glass ionomer luting cements
  • all are water based
19
Q

zinc phosphate luting cements: what is its presentation?

A
  • powder: zinc oxide, up to 10% magnesium oxide (improves compressive strength, adds colour)
  • liquid: aqueous phosphoric acid (45-64%)
20
Q

zinc phosphate:
working time?
how to extend setting time?
what does using a chilled glass slab help with?

A
  • 3-6 minutes
  • by slaking the fluid; small amount of powder added to fluid about 1 minute before
  • increases working time
    increases powder incorporated
    increase strength
    decreases solubility
21
Q

zinc phosphate: setting reaction

  • what kind of reaction?
  • describe the reaction that occurs
  • how does viscosity change?
  • how much strength in 10 mins? how long does it take to reach full strength?
  • how does the size change on setting?
  • antibacterial effect?
A
  • acid base reaction
  • dissolution of surface of ZnO powder. insoluble hydrated zinc phosphate matrix crystals effective bind to the unreacted ZnO particles
  • viscosity increases rapidly
  • 50% strength in 10mins, 100% str in 24 hours
  • shrinks slightly on setting
  • no antibacterial effect
22
Q

zinc phosphate

  • initially unset material has what pH
  • pH depends on?
  • what is this relevant to?
  • describe properties
A
  • 1.6-3.6
  • depends on thickness of mix
  • relevant to vital pulp
  • good compressive strength,
    low tensile strength (brittle)
    high solubility
23
Q

zinc polycarboxylate

  • presentation?
  • alternative presentation?
A
    1. powder: zinc oxide + up to 10% magnesium oxide
      1. aqueous copolymer of polyacrylic acid (30-40%), high viscosity
  • acid freeze dried and added to powder
  • liquid: distilled water
24
Q

zinc polycarboxylate - setting reaction

  • acid dissolves what?
  • zinc ions form cross links between what?
  • unreacted powder bound where?
A
  • zinc oxide
  • zinc ions form cross links with carboxyl groups on polyacrylic acid polymer chains
  • unreacted powder bound in matrix of zinc polyacrylate
25
Q 
zinc polycarboxylate:
working time?
- how can it be extended?
what causes it to have a short working time? what can altering the ratio have an impact on?
appears viscous but is actually \_\_\_\_\_?
A
  • 30-40s
  • extended by adding tartaric acid and mixing on a cold glass slab
  • high powder:liquid ratio. altering the ratio would have an impact on the physical properties
  • appears viscous but is actually pseudoplastic
26
Q 
zinc polycarboxylate:
initial pH? how does this relate to pulp?
how does the pH change?
antibacterial effect?
adhesive to?
A
  • initial low pH (3-4)
  • less injurious to pulp
  • pH increases rapidly
  • it has antibacterial properties
  • adhesive to enamel, dentine, and some metals (via oxide layer)
27
Q

zinc polycarboxylate:

  • describe its compressive str and tensile strength
  • how much strength is reached in 1 hour?
  • soluble in?
  • clean up?
A
  • low compressive strength, high tensile strength
  • 80% str
  • soluble in acid
  • messy to clean up
28
Q

glass ionomer:
how is it different from the restorative glass ionomer?
presentation?
alternative presentation?

A
  • same chemistry, but luting GI has smaller glass particle size
  • presentation:
    1. powder: fluoro-alumino-silicate glass
    2. liquid: aqueous poly alkenoic acid
  • alternatively:
    1. acid freeze-dried, added to powder
    2. liquid: distilled water
29
Q

glass ionomer
setting reaction?
+ what element is responsible for strong cross linking?

A
  • chemical set
    1. dissolution: calcium ions released first, then aluminium
    2. gelation
    3. hardening: aluminium trivalent, slower to be released from glass, ensures strong cross linking of polymer chains
30
Q 
glass ionomer: 
setting reaction - 
- dissolution and initial set: how long?
- seated by how long? 
- hardening can take up to how long?
- need protection to prevent what?
A
  • 3-6minutes
  • 2-2.5mins
  • up to 7 days
  • need to prevent dissolution or contamination
31
Q

glass ionomer - properties?
what may cause pulpal inflammation?
how does it compare to zinc oxide cements?

A
  • anti-caries effect via fluoride release
  • initial acidity may cause pulpal inflammation
    1. better compressive str
      1. low tensile str and fracture toughness
      2. less soluble
32
Q

resin modified glass ionomer:

constituents?

A
  1. components of GI + monomer (HEMA, Bis-GMA)

* no photo initiator, chemical cure only (acid base reaction of GI)

33
Q

resin modified glass ionomer: advantages over GI?

A
  • low solubility
  • improved biocompatability
  • improved fluoride release
  • improved physical properties
  • improved adhesion to tooth tissue
34
Q

RMGI cements - disadvantages?

A
  • can undergo hygroscopic expansion
  • avoid under conventional all-ceramic crowns
  • suitable under zirconia core / CAD-CAM crowns
35
Q

resin based luting cements: what are the constituents that are in restorative composite resins as well?
why does it have lower viscosity?
how are most of them cured?

A
  • silenated filler
  • resin e.g. bis GMA
  • low filler content -> low viscosity
  • mostly dual cured (chemical and light)
36
Q

resin based luting cements:

conventional resin luting cements - for use with?

A
  • all ceramic restorations

- indirect composite or quartz fibre posts e.g. veneers, dentine bonded crowns

37
Q

chemically adhesive resin luting cements: for?

A
  • for adhesively bonding to metals

resin retained bridges, metal veneers, poorly retained indirect restorations

38
Q

resin luting cements: bonding to ceramic

  • how does it bond to tooth?
  • when bond has to fit surface of cermic: etched with? what is applied before cementing? what kind of bond is each one?
A
  • conventional way: acid etch, rinse, dry, DBA
  • etched with hydrofluoric acid - micromechanical bond
  • silane coupling agent applied and air dried - chemical bond
39
Q 
hydrofluoric acid:
why lab use only?
why must it be neutralized?
why will it not etch periphery of veneers well?
- can cause damage to?
A
  • because it is very toxic
  • to prevent it from leaching out and causing tissue damage
  • because it tends to slump
  • to periphery of ceramic
40
Q

veneers: how does try in paste change its appearance?

A
  • it causes more light to be transmitted, less light reflected
41
Q

veneers: what is applied on top of enamel to be treated?

A
  1. etch and DBA
  2. resin luting cement
    - hydrofluoric acid etch fit surface + silane coupling agent
42
Q

bonding to metal

- how to bring micromechanical retention?

A
  • roughen the fit surface with 50micrometer alumina grit
43
Q 
bonding to metal -
chemically adhesive resin luting cement:
what kind of chemical?
name 2 monomers
both have high affinity for?
A
  • modified bis-GMA resin
  1. carboxylic monomer (4 META), e.g. C&B Superbond
  2. phosphate monomer (MDP), e.g. Panavia 21, F
  • both have high affinity for metal oxide on base metal alloy
44
Q

bonding to metal - precious alloys:

  • chemically adhesive resin luting cement?
  • how to modify fit surface?
A
  • low affinity
  • tin plate: irregular surface, attracted to tin oxide on alloy surface
  • silica coating to metal: then use silane coupling agent
  • metal primers: bifunctional monomers - one end methacryl group, other mercapto or thiol group

DENTAL MATERIALS (10 decks)

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