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BDS3 DMS > Luting Agents > Flashcards

Luting Agents Flashcards

1
Q

What should the viscosity and film thickness of a luting agent be?

A

LOW to allow seating of the restoration without interference
- ideally 25um or less

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2
Q

Why is it important that luting agents are radiopaque?

A

Makes it easier to see marginal breakdown

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3
Q

Why is it ideal if a luting agent is tooth coloured?

A

Don’t want to be able to see it through a veneer

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4
Q

What should the solubility of a luting agent be?

A

LOW to avoid marginal breakdown

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5
Q

What are the different types of luting agents?

A
  • dental cement
  • glass ionomer cement
  • composite resin luting agent
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6
Q

What are examples of dental cements that are used as luting agents?

A
  • zinc phosphate
  • zinc polycarboxylate
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7
Q

What type of reaction does zinc phosphate undergo?

A

Acid base reaction (powder & liquid)

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8
Q

What are the constituents of the powder in a zinc phosphate cement?

A
  • zinc oxide
  • magnesium dioxide
  • alumina & silica oxides
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9
Q

What are the constituents of the liquid in a zinc phosphate cement?

A
  • phosphoric acid
  • aluminium oxide
  • zinc oxide
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10
Q

What is the function of magnesium dioxide in a zinc phosphate cement powder?

A

gives white colour and increases compressive strength

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11
Q

What is the function of alumina oxide and silica oxide in a zinc phosphate cement powder?

A
  • improve physical properties
  • alter shade of set material
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12
Q

What is the initial acid base reaction of zinc oxide cement?

A

ZnO + 2H(3)PO(4) —> Zn(H2PO4) + H2O

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13
Q

What is the secondary hydration reaction of a zinc oxide cement?

A

ZnO + Zn(H2PO4)2 + 2H2O —> Zn3(H2PO4)2.4H2O

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14
Q

what are the problems associated with zinc phosphate cements?

A
  • low initial pH approx 2
  • exothermic setting reaction
  • not adhesive to tooth or restoration (actually works like grout and just fills space)
  • not cariostatic
  • final set takes 24hrs
  • brittle
  • opaque
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15
Q

How is zinc polycarboxylate different from zinc phosphate as a luting agent?

A

Zinc polycarboxylate
- bonds to tooth surfaces
- less heat during reaction
- pH low to begin with but returns to neutral quicker
- cheap

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16
Q

What are the problems associated with zinc polycarboxylate as a luting agent?

A
  • difficult to mix
  • difficult to manipulate
  • soluble in oral environment at lower pH
  • opaque
  • lower modulus & compressive strength than zinc phosphate
17
Q

How does glass ionomer luting cement differ from glass ionomer filling material?

A

particle size of glass in luting cement version is less than 20um to allow for suitable film thickness

18
Q

Why are glass ionomer cements a good luting agent option?

A
  • no shrinkage
  • long term stability
  • relatively insoluble once fully set
  • aesthetically better than ZnPhos
  • self adhesive to tooth substance
  • fluoride release
  • cheap
19
Q

How do resin-modified glass ionomer cements differ from conventional GIC?

A
  • the liquid of RMGIC contains HEMA (hydrophilic monomer)
  • REDOX reaction occurs
20
Q

how do RMGIC properties positively differ from conventional GIC?

A
  • shorter setting time
  • longer working time
  • higher compressive & tensile strength
  • higher bond strength to tooth
  • decreased solubility
21
Q

how do RMGIC properties negatively differ from conventional GIC?

A
  • HEMA is cytotoxic (super important that no monomer remains as it can damage pulp)
  • HEMA swells in a wet environment
22
Q

what is porcelain treated with before bonding it to a tooth?

A

hydrofluoric acid

23
Q

What is used as a surface wetting agent between porcelain and tooth?

A

silane coupling agent

24
Q

How is porcelain cemented to a tooth?

A

tooth —> dentine bonding agent —> composite luting resin —> silane coupling agent —> porcelain (treated with HF acid)

25
Q

How is metal prepared before bonding to a tooth?

A

etching or sandblasting

BDS3 DMS (8 decks)

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