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BDS3 DMS > Luting Agents > Flashcards

Luting Agents Flashcards

1
Q

What are the 4 different materials that can be considered luting agents?

A
  1. dental cements
  2. composite resins
  3. self-adhesive composite resins
  4. surface modifying chemicals
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2
Q

What are the properties that must be considered for luting agents?

A
  • viscosity and film thickness
  • ease of use
  • radiopacity
  • marginal seal
  • aesthetics
  • solubility
  • cariostatic ability
  • biocompatibility
  • mechanical properties
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3
Q

Discuss the importance of viscosity and film thickness in luting agents

A
  • viscosity and film thickness should be low to allow seating of the restoration without interference
  • viscosity must increase as the material sets
  • film thickness should be as thin as possible (<25um)
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4
Q

How do filler particles differ in luting agents and filling materials?

A
  • smaller filler particles in luting agents
  • viscosity and film thickness dependant on the size of the filler particles
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5
Q

Discuss the importance of ease of use of luting agents

A
  • should be easy to mix
    • encapsulated with clicker system
  • working time should be long to allow seating
  • setting time should be short
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6
Q

Discuss the importance of radiopacity of luting agents

A
  • highlights crown-tooth margin
  • makes marginal breakdown easier to identify
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7
Q

Discuss the importance of marginal seal of luting agents

A
  • should chemically bond to tooth and restoration
  • bond should be permanent and impenetrable
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8
Q

Discuss the importance of aesthetics of luting agents

A
  • should be tooth coloured
  • variations of shade and translucency should be available
  • if not translucent can affect the veneer on top
  • some material may be visible so should match the colour of the restoration
  • non-staining
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9
Q

Discuss the solubility of luting agents

A
  • must be low solubility
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10
Q

Discuss the importance of cariostatic behaviour in luting agents

A
  • prevents secondary caries around crown margins
  • can be fluoride releasing or antibacterial
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11
Q

Discuss the importance of biocompatibility of luting agents

A
  • must be non-toxic
  • must not damage the pulp
    • inappropriate pH (especially low)
    • heat on setting
  • low thermal conductivity
    • indirect restorations are often metal based
    • heat must not reach pulp
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12
Q

Discuss the desired mechanical properties of luting agents

A
  • high compressive strength
  • high tensile strength
  • high hardness value
  • Young’s modulus similar to tooth
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13
Q

Give two examples of dental cements

A
  • zinc phosphate
  • zinc polycarboxylate
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14
Q

Give two examples of glass ionomer cement

A
  • conventional
  • resin modified
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15
Q

Give three examples of composite resin luting agents

A
  • total etch for use with DBA
  • self-etch
  • bonding agent incorporated
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16
Q

What are the advantages of zinc phosphate?

A
  • excellent clinical service
  • easy to use
  • cheap
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17
Q

What are the components of zinc phosphate cement powder?

A
  • zinc oxide
    • > 90%
    • main reactive ingredient
  • magnesium dioxide
    • <10%
    • provides white colour
    • increases compressive strength
  • metal oxides
    • e.g. alumina and silica
    • improve physical properties
    • alter shade of material once set
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18
Q

What are the components of zinc phosphate cement liquid?

A
  • phosphoric acid
    • aqueous solution around 50%
  • oxides
    • buffer solution
    • aluminium oxide (ensures even consistency)
    • zinc oxide (slows reaction)
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19
Q

Describe the reaction that takes place in zinc phosphate cement

A
  • acid base reaction:
    ZnO + 2H3PO4 —-> Zn(H2PO4)2 + H2O
  • hydration reaction:
    ZnO + Zn(H2PO4)2 + 2H2O
    —->
    Zn3(H2PO4)2.4H2O
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20
Q

Discuss the setting of zinc phosphate cement after the acid-base and hydration reactions

A
  • aluminium oxide prevents crystallisation resulting in an amorphous glassy matrix of acid salt surrounded by ZnO powder
  • matrix is insoluble but porous
  • hydration reaction fills spaces with free water
  • cement matures and binds water leading to a stronger less porous material
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21
Q

Discuss the disadvantages of zinc phosphate cement

A
  • low initial pH
    • around pH2
    • can cause plural irritation
    • low pH for around 24 hours
  • exothermic setting reaction
    • heat generated
  • not adhesive to tooth or restoration
    • retention may be slightly micro mechanical
    • best for non-retentive cavities
    • removed with ultrasonic scaler
  • not cariostatic
  • final set takes 24 hours
  • brittle
  • opaque
    • yellow/white in colour
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22
Q

What is the component that varies between zinc phosphate cement and zinc polycarboxylate cement?

A

the phosphoric acid is replaced with poly acrylic acid

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23
Q

What are the advantages of zinc polycarboxylate cement?

A
  • bonds to tooth surface in a similar way to glass ionomer cements
  • reduced exothermic reaction
  • less time at low pHs
  • long chain acids do not readily penetrate dentine
  • cheap
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24
Q

What are the disadvantages of zinc polycarboxylate cement?

A
  • difficult to mix
  • difficult to manipulate, jelly like material
  • soluble in the oral environment at lower pHs
  • opaque
  • lower modulus and compressive strength than zinc phosphate
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25
Q

Are zinc phosphate and zinc polycarboxylate used now?

A

No - mainly historic

  • materials with chemical bonding more valuable
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26
Q

What is the difference between glass ionomer cement and glass ionomer filling material?

A
  • the particle size of the glass particles
    • less than 20um in cement
    • allows for suitable film thickness
    • crown can be fitted completely
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27
Q

Describe the acid base reaction between acid and glass which occurs in glass ionomer cement

A
  • glass (SiO2, Al2O3, CaF2)
  • polyacid mixture of acrylic, malice and itaconic acid (+copolymers)
  • reaction goes through dissolution, gelation and hardening stages
28
Q

Describe the bond between glass ionomer cement and tooth tissue

A
  • ion exchange with the calcium in enamel and dentine
  • hydrogen bonding with collagen in dentine
  • family strong and durable bond with tooth
  • no chemical bond with restoration
  • restoration must be sandblasted to allow for mechanical adhesion
29
Q

Describe the clinical ease and durability of glass ionomer cement

A
  • no shrinkage
  • long term stability
  • relatively insoluble once set (7 days)
  • aesthetically better than Zinc Phosphate
  • self adhesive to tooth substance
  • fluoride releasing
  • cheap (£15 per bottle)
30
Q

What is the additional component contained in resin modified glass ionomer cement compared to conventional?

A
  • HEMA
    • hydrophilic monomer in liquid
    • HydroxyEthyl MethAcrylate
31
Q

What is the effect of light activation on HEMA?

A

polymerisation of HEMA and copolymers leading to a rapid initial set

32
Q

What are the three setting reactions for resin modified glass ionomer

A
  • light activation
  • acid base reaction
  • redox
33
Q

What properties are positively affected by the addition of resin?

A
  • shorter setting time
  • longer working time
  • high compressive and tensile strengths
  • higher bond strength to tooth tissue
  • decreased solubility
  • command setting
34
Q

What are the potential disadvantages of resin modified glass ionomer cements

A
  • HEMA is cytotoxic
    • must be no monomer released
    • can damage pulp
  • HEMA swells due to moisture
    • water soluble
    • 1-2% expansion experienced
    • not suitable for porcelain crowns (crack)
    • not suitable for post crowns (root fracture)
  • no bond to restoration
35
Q

What must be used with composite luting agents?

A

a suitable dentine bonding agent

36
Q

What are the disadvantages of composite luting agents?

A
  • technique sensitive
  • reduced physical properties in some cases
    • for dual cure that isn’t light cured
    • light cannot penetrate crowns/onlays/etc.
37
Q

Give an example of a brand of composite luting agent

A

NX3
- Nexus Third Generation

38
Q

Describe the bond between composite luting agents and indirect composites

A
  • micro mechanical
    • touch internal surface of restoration
  • chemical
    - remaining C=C bonds on fitting surface

dual cure must be used as light penetration will not be adequate

39
Q

How do dentine bonding agents bond tooth tissue to composite luting resins?

A

They have hydrophobic and hydrophilic ends
- hydrophobic to composite
- hydrophilic to tooth

40
Q

Why is the bond between porcelain and tooth important?

A

porcelain is brittle and requires a bond to prevent fracture

41
Q

Describe the way in which porcelain is bonded to tooth tissue

A
  • untreated porcelain is smooth/non-retentive
  • treated with HF/HCl to etch surface
  • roughened surface but is not hydrophobic
  • surface wetting agent required
  • phosphoric acid cannot be used to etch surface as interacts with oxide groups in the porcelain
42
Q

What is the purpose of a silane coupling agent?

A

Gamma-methacryoxypropyltrimothoxysilane

  • applied to porcelain as a monolayer
  • double ended molecule with oxide and C=C
  • forms strong bond with oxide on porcelain
  • C=C bond with the composite resin
  • same way in which DBA acts with tooth/composite
43
Q

Describe bonding between composite luting agents and metal

A
  • no bond between composite and metal
    • metal must be roughened
    • can be done by etching or sandblasting
    • chemical bonding is required for strength
44
Q

What does the process of etching metal involve?

A
  • electrolytic etching removes the different phases of the alloy at different rates
    • retentive surface produced
    • technique sensitive
    • Beryllium (in alloys) is carcinogenic
    • precious metals cannot be etched
    • rarely used technique
45
Q

How is bonding to non-precious metals achieved?

A
  • MDP and 4-META
    • carboxylic and phosphoric derived
    • resin monomers
  • acidic end and C=C end
    • acidic end reacts with metal oxide
    • creates hydrophobic surface
46
Q

What are the necessary considerations for bonding to metal?

A
  • dual curing material must be used
    • light cannot penetrate metal
    • crowns/bridges/posts possible
  • technique sensitive
    • moisture control
  • glass ionomer
    • dissolution where wet
    • less strong in areas
  • composite luting agents
    • dissolution where wet
    • no bond in these areas
47
Q

How is bonding to precious metals achieved?

A
  • composition must be changed to allow oxide formation
    • increase copper content (heat 400 degrees)
    • tin plate fitting surface (oxide rich)
    • sulphur based chemistry in bonding agent
48
Q

What is a self-adhesive composite resin?

A
  • metal coupling agent incorporated into resin
    • simplified bonding process
    • anaerobic self cured material
49
Q

What are the advantages and disadvantages of self-adhesive composite resins

A

Advantages:
- consistent results over many years
- good film thickness

Disadvantages
- opaque (only used under metal)
- moisture sensitive
- expensive

50
Q

Describe the key features of Panavia composite resin

A
  • phosphoric acid gel, DBA, cement
  • MDP used in Panavia cement
  • edges covered with oxiguard or vaseline
51
Q

What are self etching composite resin cements?

A
  • combination of composite resin cement and self etching dentine bonding agent
    • Rely X Unicem
    • contain metal bonding agent
    • good moisture control required
    • questionable bond strength
  • not excellent properties but multi-functional
52
Q

How do self etching composite resins work?

A
  • acidic groups bind to calcium
  • ions from dissolution of filler neutralise remaining acidic groups forming chelate
  • chelate reinforced methacrylate network
  • limited removal of smear layer
  • limited infiltration to tooth surface
  • good bond strength to dentine
53
Q

How do self etching composite resin luting agents compare to composite luting cements

A

all mechanical properties are lesser than composite luting cements

54
Q

Describe the bonding capabilities of self etching composite resin luting agents

A
  • bonding to enamel
    • lower than to dentine
    • acid etch required prior to application
  • bonding to dentine
    • better than to enamel
    • no acid etch recommended
  • bonding to ceramics
    • brand specific
    • RelyX Unicem good with sandblasted Zirconia
  • bonding to metal
    • better to non-precious
    • not used for ortho brackets
  • good for crowns
  • not good for resin retained bridgework
55
Q

what can be used to cement MCCs?

A

Yes:
- GIC
- RMGIC

Maybe:
- Dual cure composite +DBA
- Anaerobic cure composite
- Self adhesive composite

No:
- Light cure composite +DBA

56
Q

what can be used to cement metal posts?

A

Yes:
- GIC

Maybe:
- Dual cure composite +DBA
- Anaerobic cure composite
- Self adhesive composite

No:
- RMGIC
- Light cure composite +DBA

57
Q

what can be used to cement fibre posts?

A

Yes:
- Dual cure composite +DBA
- Self adhesive composite

Maybe:

 - Anaerobic cure composite

No:
- GIC
- RMGIC
- Light cure composite +DBA

58
Q

what can be used to cement veneers?

A

Yes:
- Light cure composite +DBA

Maybe:
- Dual cure composite +DBA
- Self adhesive composite

No:
- GIC
- RMGIC
- Anaerobic cure composite

59
Q

what can be used to cement adhesive bridges?

A

Yes:
- Anaerobic cure composite

Maybe:
- Dual cure composite +DBA
- Self adhesive composite

No:
- GIC
- RMGIC
- Light cure composite +DBA

60
Q

what can be used to cement Zirconia crowns?

A

Yes:
- GIC
- RMGIC
- Dual cure composite +DBA
- Anaerobic cure composite
- Self adhesive composite

No:
- Light cure composite +DBA

61
Q

what can be used to cement composite inlays?

A

Yes:
- Dual cure composite +DBA
- Self adhesive composite

No:
- GIC
- RMGIC
- Light cure composite +DBA
- Anaerobic cure composite

62
Q

what can be used to cement porcelain inlays?

A

Yes:
- Dual cure composite +DBA
- Self adhesive composite

No:
- GIC
- RMGIC
- Light cure composite +DBA
- Anaerobic cure composite

63
Q

what can be used to cement gold restorations?

A

Yes:
- GIC
- RMGIC

Maybe:
- Dual cure composite +DBA
- Self adhesive composite
- Anaerobic cure composite

No:
- Light cure composite +DBA

64
Q

What properties are desirable for temporary cements?

A
  • soft, for easy removal
  • potentially non-setting
  • retentive prep required
65
Q

What are the components of temporary cements?

A
  • two paste systems
    • base
    • catalyst/accelerator
  • base
    • ZnO
    • starch
    • mineral oil
  • catalyst/accelerator
    • resins
    • eugenol (not used for resin cements)
    • ortho-EBA
    • carnauba wax (prevents full set)
  • vaseline can be mixed into the material to reduce the retention

BDS3 DMS (10 decks)

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