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Dental Materials Y2 > Cavity Lining Materials > Flashcards

Cavity Lining Materials Flashcards

1
Q

Describe cavity lining materials

A

Intermediate restorative materials lining the cavity, applied before the placement of the restorative, not temporary but permanent.

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2
Q

What is the purpose of the cavity lining materials

A

Protection, palliative and therapeutic barrier to stop penetration through the dentinal tubules to protect the pulp.

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3
Q

What are the choices we have for using cavity lining materials before we add the restorative

A

Nothing
Cavity varnish
Cavity liner
Cavity base

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4
Q

What are some of the cavity lining material groups that we can use

A
  • Varnishes
  • Calcium Hydroxide cements
  • Zinc oxide based cements
  • Glass ionomer cements
  • Resin modified glass ionomer cements
  • Visible light cured resins
  • Calcium silicate based cements
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5
Q

AY BAWS CAN I HABE DE NOTE PLZ

A

Based on the kind of restorative we use different cavity lining materials to protect the pulp

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6
Q

What kind of pulp protection do cavity varnishes provide

A

Chemical protection

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7
Q

What kind of pulp protection do cavity liners provide

A

Pulp medication

Thermal/electrical protection

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8
Q

What kind of pulp protection do cavity bases provide

A

Thermal/electrical protection

Mechanical protection

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9
Q

What is cavity varnish designed to do

A
  • Seal dentine
  • Reduce diffusion through dentin
  • Decrease microleakage
  • No strengthening
  • Does not bond chemically to dentin
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10
Q

Describe the composition of cavity varnish

A
  • Natural resins e.g. copal
  • Synthetic resins e.g. polystyrene
  • Solvent e.g. alcohol, acetone, ether
  • Some calcium hydroxide and/or zinc oxide
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11
Q

What does cavity liner seal and do

A

Seals exposed dentin

Promotes health of the pulp and adheres to the tooth structure and has antibacterial action

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12
Q

Name some types of cavity liner

A

Calcium hydroxide
Zinc Oxide eugenol
Zinc oxide non-eugenol

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13
Q

What does cavity base do

A 
Replaces dentin 
Blocks out undercuts
Insulation
High strength
Minimises bulk of restorative as it is quite thick
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14
Q

What is an undercut

A

When the cavity goes into the dentin and errr yh the cavity base can fill that

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15
Q

Name some cavity base materials

A
  • Reinforced zinc oxide eugenol
  • Visible light cured resins
  • Zinc phosphate
  • Zinc polycarboxylate
  • Glass ionomer
  • Resin modified glass ionomer
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16
Q

What are the 2 forms of zinc oxide eugenol cement

A

Two paste or powder-liquid form

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17
Q

Describe the composition of the powder component of zinc oxide eugenol cement

A
  • Main component (ZnO/MgO)
  • Fillers SiO2, Al2O3
  • Dicalcium phosphate, mica or rosin - Improves mixing
  • Zinc salt 1% accelerates set
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18
Q

Describe the composition of the liquid component of zinc oxide eugenol cement

A
  • Eugenol or oil of cloves
  • other oils may also modify viscosity
  • Acetic acid 1% - accelerates set
  • Water - small amount - essential to set
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19
Q

Describe the setting reaction of zinc oxide eugenol cement

A
  • Acid-base reaction
  • Reaction of zinc oxide with eugenol to form zinc eugenolate, a chelate complex
  • Water initiates the reaction and is a by product of the reaction
    ZnO + 2HE ZnE2 + H2O
20
Q

Describe the basic features of the chemical structure of eugenol

A

A substituted phenol

Weakly acidic

21
Q

What will produce a faster and stronger set of zinc oxide eugenol cement

A

Higher powder to liquid ratio and smaller particle size

22
Q

Describe the pH changes in the zinc oxide eugenol setting process

A

Initial pH of 5.5-6 and then goes up 6-8 in the set cement

23
Q

What are the advantages of zinc oxide eugenol cement

A
  • Easy mix and handle
  • Fast set in the mouth
  • Moisture accelerates set
  • Non irritant pH close to the neutral
  • Obtudant (calming effect on the pulp) when placed on dentin
  • Good sealing characteristics
  • Protects the pulp from chemical irritation
  • Good thermal insulator
24
Q

What are the disadvantages of zinc oxide eugenol cement

A
  • Low compressive and tensile strengthes
  • High water solubility
  • Eugenol is a potential allergen, smells strong and is a mild irritant when in direct contact with the pulp
  • Eugenol inhibits vinyl polymerisation so can’t be used under composites and compomers
25
Q

What are the uses of Zinc oxide eugenol cement

A

ZOE cements are used in applications where strength isn’t important but low irritancy is

  • Not in direct contact with the pulp
  • Thermal insulating base
  • Temporary restorations
  • Intermediate restorations
  • Long term cementation
  • Endodontic use
  • Periodontal dressing
26
Q

Describe the composition of the powder component of EBA cement

A

ZnO - 60-75%
Fillers - SiO2, Al2O3 - 20-35%
Hydrogenated rosin - 6%

27
Q

Describe the composition of the liquid component of EBA cement

A
  • 50-65% of the eugenol in ZOE cement is replaced by o-ethoxybenzoic acid
  • 35-50% eugenol
28
Q

Is o-ethoxybenzoic acid more acidic than eugenol

A

yup

29
Q

What are the properties and uses of EBA cements

A
  • Properties similar to ZOE
  • EBA cements have better strength
  • EBA cements have lower water solublility
  • Poor handling characteristics
  • Uses similar to ZOE cements but used little in reality as other materials are available
30
Q

What are the 2 pastes for calcium hydroxide cements called

A

Base and catalyst

31
Q

What can the base pastes for calcium hydroxide cements be made of

A

Salicylate ester 40% e.g. butylene glycol disalicylate

Filler e.g. TiO2, CaSO4, BaSO4

32
Q

What can the catalyst pastes for calcium hydroxide cements be made of

A

Ca(OH)2 50%
ZnO 10%
Plasticiser 40% e.g. toluene sulphonamide, zinc stearate

33
Q

Describe the calcium hydroxide cement setting reaction

A

Acid-base reaction:

  • Disalicylate reacts with Ca(OH)2 and ZnO
  • Calcium and zinc disalicylate forms
34
Q

What are the advantages of calcium hydroxide cements

A
  • Easy to mix and handle
  • Rapid hardening in thin layers
  • Moisture accelerates set
  • Good seal
  • Alkaline pH 9-12, can neutralise acid materials e.g. zinc phosphate cements
  • Antibacterial
  • Stimulate reparative/sclerotic/ secondary dentin - contact with pulp causes necrosis layer that calcifies
  • compatible with composites
35
Q

What are the disadvantages of calcium hydroxide cements

A
  • Low strength even when fully set
  • Weakened by exposure to moisture
  • Can dissolve completely acid conditions where marginal leakage occurs
  • Can undergo plastic deformation at mouth temperature
36
Q

What are the uses of calcium hydroxide cement

A
  • Cavity lining, especially in deep cavities, pulp capping
  • With composites as ZOE cements inhibit setting of composites
  • Care must be taken when acid etching
  • Strong enough to withstand amalgam condensation pressures
  • Thermal insulating agents
  • Endodontic use
37
Q

What accelerates the setting of ZOE and CH cements

A

Moisture in the mouth

38
Q

AY BAWS CAN I HABE DE NOTE PLZ

A

CH cements stimulate secondary dentin formation

39
Q

What is a suspension liner and what is it made of

A

This is a non-setting, thick layer of a suspension of calcium hydroxide in water. Methyl or ethyl cellulose can be added for strength

40
Q

What visible light cured dental composites can be used as cavity liners

A

BisGMA
UDMA
Phosphonated

41
Q

Name some fillers that are used in visible light cured resins

A

Ca(OH)2
Fluoride releasing glass
Hydroxtapatite
Calcium Silicate

42
Q

What are the advantages of using visible light cured resins as cavity liners

A
  • Tougher and less soluble
  • Increased resistance to etchants
  • Can have alkaline surface pH~11 but not antibacterial
43
Q

What are the properties and uses of Calcium Silicate base or MTA cements

A
  • Mainly used in endodontic applications
  • High Strength
  • Alkaline pH
  • Bioactive pulp repair
44
Q

What is added to reinforce ZOE cements

A

10-40% of a synthetic resin is added to the powder and coated round the powder particles. Styrene or MMA is added to the liquid.

45
Q

What does reinforcing ZOE cement result in

A
  • Increased compressive strength 40 MPa
  • Increased tensile strength
  • Reduced water solubility

Dental Materials Y2 (13 decks)

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