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BDS 2: Dental Materials > Cavity Lining (Acid-Base Cements) > Flashcards

Cavity Lining (Acid-Base Cements) Flashcards

1
Q

What are some general uses of acid-base dental cements? (5)

A
  • Cavity liner
  • Permanent/Temporary filling
  • Root canal sealer
  • Permanent/Temporary luting of crown/bridge
  • Attachment of orthodontic appliances
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2
Q

Name some of the ideal properties of an acid-base cement (11)

A
  • Non-irritant and non-toxic to the oral tissues
  • Insoluble in oral fluids or anything taken into the mouth
  • Adhesive to the tooth structure
  • Adequate mechanical properties
  • Thermally, chemically and electrically insulating
  • Provide a therapeutic effect, e.g. bacteriostatic and obtundent
  • An appropriate thermal expansion coefficient
  • Good optical properties (aesthetics)
  • Radio-opaque
  • Appropriate rheological properties
  • Easily manipulated
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3
Q

Definition of acid-base cement

A

Mixing of powder and liquid, which, through an acid-base reaction, produces a solid matrix that binds the mass together.

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4
Q

What does the unreacted powder in the set cement act as? What does this do?

A

The unreacted powder particles act as a filler. Increasing strength of the set cement

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5
Q

How does particle size affect setting of a cement?

A

The smaller the particle size the greater the specific surface area and the faster the setting reaction

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6
Q

How does powder:liquid affect setting of a cement?

A

A higher powder content will give a faster set

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7
Q

How does temperature affect setting of a cement?

Why does it have this affect?

A
  • Increasing the temperature will increase the setting rate

- Setting reaction is exothermic so may further accelerate set

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8
Q

How does moisture affect setting of a cement?

A

Presence of moisture accelerates setting of some of the cements but slows it down for other cements

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9
Q

What are the 6 types of acid-base cements?

A
  • Zinc phosphate cements
  • Zinc polycarboxylate cements
  • Glass ionomer cements (GICs)
  • Zinc oxide eugenol (ZOE) cements
  • Calcium hydroxide cements
  • Ethoxybenzoic acid (EBAs) cements
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10
Q

Type I acid-base cements;

Use?
Particle size?

A
  • Luting

- ~25µm

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11
Q

Type II acid-base cements;

Use?
Particle size?

A
  • Restorative or a lining

- ~40µm

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12
Q

Type III acid-base cements;

Use?

A

Lining or base

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13
Q

Which acid-base cements are phosphate bonded?

A

Zinc phosphate cements

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14
Q

Which types of acid-base cements are polycarboxylate bonded? (2)

(Chemical bond!!)

A
  • Zinc polycarboxylate cements,

- Glass ionomer cements

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15
Q

Which types of acid-base cements are phenolate bonded? (3)

A
  • Calcium hydroxide cements
  • Zinc oxide/eugenol cements (ZOE)
  • EBA-based cements
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16
Q

Which types of acid-base cements are water based? (3)

A
  • Zinc phosphate
  • Zinc polycarboxylate,
  • Glass ionomer
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17
Q

Which types of acid-base cements are oil based? (3)

A
  • Calcium hydroxide
  • Zinc oxide/eugenol (ZOE)
  • EBA
18
Q

What powder do all cements except GIC use?

A

Zinc oxide

19
Q

What is the main reactant in a zinc phosphate cements?

What are the minor reactants?

A
  • Roughly 90% ZnO

- 10% MgO, aluminum oxide and silicon dioxide

20
Q

Advantages of having ZnO in based cements?

A
  • Low cost
  • Good radiopacity and whiteness
  • Low toxicity
  • Reactivity can be controlled
21
Q

What is the primary liquid component used in zinc phosphate cements?

A

Phosphoric acid (H3PO4)

22
Q

What is the correct way to mix zinc phosphate cements?

A

Mix using a cool mixing slab and incorporate the powder in small amounts

23
Q

What are some disadvantages of zinc phosphate cements? (6)

A
  • Low initial pH
  • Slow to neutralise
  • Brittle
  • High acidic solubility
  • No chemical adhesion
  • Setting shrinkage
24
Q

What can be used to modify the set of Zinc polycarboxylate cements?

A

Bismuth salts

25
Q

What is the advantage of having SnF2 (Stannous Fluoride) in cements? (3)

A
  • Fluoride source
  • Improves mixing
  • Increases strength
26
Q

What is the primary liquid component used in zinc polycarboxylate cements?

A

Polyacrylic acid (PAA)

27
Q

Disadvantages of Zinc polycarboxylate cements (3)

A
  • Lower compressive strength than zinc phosphate cements
  • Short working time
  • Not necessarily adhesive to all surfaces
28
Q

What is cavity varnish designed to do? (3)

A
  • Seal dentine
  • Reduce diffusion through dentine
  • Decrease microleakage
29
Q

What is cavity liner designed to do? (2)

A
  • Seal exposed dentine

- Promotes health of pulp

30
Q

What is cavity base designed to do? (4)

A
  • Act as dentine replacement
  • Strengthens restoration
  • Blocks out undercut
  • Insulates tooth
31
Q

What will happen to Zinc eugenolate in the presence of excess water?

A

The complex is not stable and the setting reaction will reverse in the presence of excess water

32
Q

What is the..

Mixing time?
Working time?
Setting time?

Of ZOE cement

A
  • 60-90 seconds
  • 2-3 minutes
  • Less than 5 minutes
33
Q

What are the disadvantages of ZOE cements? (4)

A
  • Low compressive and tensile strengths
  • High water solubility
  • Eugenol is potential allergen
  • Eugenol inits C=C polymerisation so cannot be used with composites
34
Q

How are ZOE cements reinforced? (2)

Add what to the powder?
Add what to the liquid?

A
  • 10-40% of a synthetic resin is added to the powder

- Styrene or MMA is added to liquid

35
Q

Advantages of reinforced ZOE? (3)

A
  • Increased compressive strength
  • Increased tensile strength
  • Reduced water solubility
36
Q

Compare EBA cements with ZOE cements (2)

A
  • EBA cements have better strength

- EBA cements have lower water solubility

37
Q

What is a disadvantage of EBA cements?

A

Poor handling characteristics

38
Q

If a patient is allergic to eugenol what other oils can form a cement with ZnO instead?

A

Nonaoic acid

39
Q

What is the..

Mixing time?
Working time?
Setting time?

Of a Calcium hydroxide cement

A
  • 5-30 seconds
  • 30-60 seconds
  • 1-2 minutes
40
Q

Disadvantages of calcium hydroxide cements (4)

A
  • Low strength
  • Weakened by moisture
  • Dissolved by acidic conditions
  • Can undergo plastic deformation at mouth temperature
41
Q

Compare ZOE cements to Calcium hydroxide cements (4)

A
  • ZOE stronger and less soluble than CH
  • ZOE has a calming effect
  • CH is alkaline, antibacterial
  • CH stimulates secondary dentine formation

BDS 2: Dental Materials (13 decks)

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