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BDS3 Dental Materials Sciences > Luting Agents > Flashcards

Luting Agents Flashcards

1
Q

What are the ideal properties of a dental luting agent?

A
  • low viscosity and film thickness
  • easy to use
  • radiopaque
  • good marginal seal
  • aesthetics
  • low solubility
  • biocompatible
  • cariostatic
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2
Q

what influences the viscosity and film thickness of a luting agent?

A

the size of powder or filler particles in the material

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3
Q

What are the ideal mechanical properties of a dental luting agent?

A
  • high compressive strength
  • high tensile strength
  • high hardness value
  • Young’s modulus similar to tooth
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4
Q

Types of materials that can be used as dental luting agents

A
  • dental cement
  • GIC
  • composite resin luting agents
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5
Q

Constituents of zinc phosphate cement

A

powder
- zinc oxide >90%
- magnesium dioxide <10%
- alumina and silica oxides - improves physical properties

liquid
- aqueous solution of phosphoric acid approx 50%
- aluminium oxide
- zinc oxide

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6
Q

why is magnesium oxide added to zinc phosphate cement?

A
  • gives white colour
  • improves compressive strength
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7
Q

What are the downsides of zinc phosphate cement?

A
  • initial pH approx 2 = causes plural irritation
  • exothermic setting reaction
  • not adhesive to tooth or restoration
  • not cariostatic
  • final set takes 24 hours
  • opaque
  • brittle
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8
Q

How does zinc polycarboxylate cement differ form zinc phosphate cement?

A
  • phosphoric acid replaced by poly acrylic acid
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9
Q

what are.the advantages of zinc polycarboxylate cement over zinc phosphate?

A
  • bonds to tooth
  • less heat of reaction
  • pH returns to neutral more quickly
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10
Q

what are the downsides of zinc polycarboxylate cement?

A
  • difficult to mix
  • difficult to manipulate
  • soluble in oral environment at lower pH
  • opaque
  • Lower modulus and compressive strength than zinc phosphate
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11
Q

How does GIC bond to the tooth surface?

A
  • ion exchange with calcium in enamel and dentine
  • hydrogen bonding with collagen in dentine
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12
Q

Advantages of glass ionomer cements

A
  • low shrinkage
  • long term stability
  • relatively insoluble once fully set
  • beter aesthetics than zinc phosphate
  • self adhesive to tooth substance
  • fluoride releasing
  • cheap
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13
Q

What is meant by the term ‘marginal seal’?

A

the luting agent should bond chemically to the tooth and the indirect restoration with a permanent and impenetrable bond

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14
Q

How does GIC bond to tooth surfaces?

A

ion exchange with calcium in enamel and dentine
hydrogen bonding with collagen in the dentine

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15
Q

Glass ionomer cement advantages

A

clinically easy to use and durable
low shrinkage
long term stability
relatively insoluble when set
aesthetically better than zinc phosphate cements
self adhesive to tooth surface
fluoride releasing
cheap

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16
Q

How does GIC/RMGIC differ from GI/RMGI filling material?

A

glass particle size is smaller to allow acceptable film thickness

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17
Q

Benefits of RMGIC?

A

incorporation resin improves some material properties:
- shorter setting time
- longer working time
- higher compressive and tensile strengths
- higher bond strength to tooth
- decreased solubility

18
Q

RMGIC potential problems

A

HEMA is cytotoxic
- important no monomer remains as it can damage the pulp
- HEMA swells, expands in a wet environment
- cannot be used to cement convention porcelain crowns as they may crack
- may split the root if used to cement posts
no bond to indirect restoration

19
Q

Composite luting agents - advantages

A

better physical properties
aesthetics
lower solubility

20
Q

downsides of composite luting agents

A

dual cure composite must be used with DBA
- physical properties are reduced by 25% if they are not light cured
technique sensitive

21
Q

features of composite luting agents

A

can be dual cured or light cured
must be used in conjunction with suitable DBA

22
Q

why is a silane coupling agent used to bond porcelain to composite?

A

porcelain is smooth and non retentive
must be etched with HF
produces a rough retentive surface but still not hydrophobic and compatible with composite resin luting agents

23
Q

Function of a silane coupling agent

A

applied to etched porcelain surface
forms very strong bond between oxide groups on porcelain surface and the silane
other end of silane molecule has c=c bond which reacts with composite resin luting agent

24
Q

How is metal usually etched?

A

by sandblasting

25
Q

Downsides of sandblasting

A

roughens surface but doesn’t give the undercut surface of etching
- chemical bond required to strengthen bond

26
Q

What type of composite resin luting agent would you use to bond to porcelain?

A

dual cured composite
- only use light cure if restoration is thin - must increase curing time

27
Q

Ideal luting agents for an MCC?

A

GIC
RMGIC

28
Q

Ideal luting agent for a metal post?

A

GIC

29
Q

ideal luting agents for a fibre post?

A
  • dual cure composite and dentine bonding agent
  • self adhesive composite
30
Q

ideal luting agent for a veneer?

A

light cure composite + dentine bonding agent

31
Q

ideal luting agent for an adhesive bridge

A

anaerobic cure composite

32
Q

ideal luting agents for a zirconia crown

A
  • GIC
  • RMGIC
  • dual cure composite + DBA
  • anaerobic cure composite
  • self adhesive composite
33
Q

ideal luting agents for a composite inlay?

A
  • dual cure composite + DBA
  • self adhesive composite
34
Q

ideal luting agents for a porcelain inlay?

A
  • dual cure composite + DBA
  • self adhesive composite
35
Q

ideal luting agents for a gold restoration?

A
  • GIC
  • RMGIC
36
Q

What are temporary cements?

A

Materials which are made to cement temp restorations in place while definitive restoration is being fabricated

37
Q

Temporary cements - properties

A

soft for easy removal
- some do not set at all
- prep must be physically retentive

38
Q

constituents of temporary cements

A

supplied as two paste systems
- base and catalyst/accelerator
- base contains ZnO, starch and mineral oil
- accelerator contains resins, eugenol or orthodontic-EBA and carnauba wax

39
Q

Two main types of temporary cements

A

those with and without eugenol

40
Q

why should eugenol containing materials not be used to cement provisional restorations where the permeant restoration will be cemented with a resin cement?

A

residual eugenol may interfere with the setting of resin luting agents

BDS3 Dental Materials Sciences (10 decks)

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