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BDS2 CDS DMS > cavity lining materials > Flashcards

cavity lining materials Flashcards

1
Q

what is the most widely used lining material?

A

glass ionomer

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2
Q

why is glass ionomer a good lining material?

A

it can bond and seal dentine
it can bond to the composite on top
it releases fluoride over time and can be cariostatic

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3
Q

why is glass ionomer easy to use?

A

mixing is simple two paste
light cured so command set
long working time short setting time

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4
Q

what is GIC thermal conductivity and diffusivity lower than?

A

dentine

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5
Q

how is thermal expansion in GIC compared to dentine?

A

similar

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6
Q

what is the compressive strength of GI lining materials?

A

> 170MPa

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7
Q

what are the benefits of glass ionomer linings?

A

radiopaque
marginal seal best as there is a chemical bond to enamel and dentine
only material to predictable seal dentinal tubules
-reduced microleakage & post op sensitivity

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8
Q

compare GIC to RMGIC

A

GIC greater solubility
GIC less soluble than other liners except zinc phosphate cement
RMGIC less soluble than any other cement

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9
Q

what are the disadvantages of glass inonomers?

A

fluoride release possible & cariostatic
benzoyl iodides and bromides released during polymerisation reaction
-cytotoxic and can be effective against residual cavity bacterial
complete cure required as unreacted HEMA may damage pulp

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10
Q

what lining material require etching but no surface tx?

A

glass ionomer

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11
Q

when is RMGIC used?

A

for cavities in dentine for amalgam and larger composite cavities

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12
Q

when is calcium hydroxide used?

A

only when cavity approaches pulp

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13
Q

what should calcium hydroxide be covered with?

A

RMGIC

-protects and prevents dissolution beneath rest.

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14
Q

what are the base constituents of Ca OH liner?

A

calcium hydroxide 50%
zonc oxide 10%
zinc stearate
N-ethyl toluene sulphonamine 40%

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15
Q

what are the catalyst constituents of Ca OH?

A

butylene glycol disaliclate
titanium dioxide
ca sulphate
ca tungstate

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16
Q

what is the setting reaction of a Ca OH liner?

A

chelation reaction between ZnO and butylene glycol disalicylate

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17
Q

what is the initial pH of Ca OH?

A

12

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18
Q

how is CaOH bactericidal to cariogenic bacteria?

A

highly alkaline liner kills bugs

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19
Q

how does CaOH irritation lead to reparative dentine formation?

A

cement causes irritation to odontoblast layer, causes necrosis -> tertiary dentine -> calcified bridge walling base of cavity from pulp

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20
Q

what are the properties of CaOH liners?

A 
quick setting time
radiopaque
easy to use
low compressive strength
unstable
soluble
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21
Q

what are the zinc oxide based cements?

A 
zinc phosphate
zinc polycarboxylate
zinc oxide eugenol
resin modified ZOE
ethoxybenzoic acid ZOE
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22
Q

describe zinc phosphate cement

A 
acid base reaction
powder & liquid
excellent clinical service
easy to use
cheap
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23
Q

what are the powders in zinc phosphate cement?

A 
zinc oxide 90%
magnesium dioxide 
-colour
-compressive strength
other oxides
-improved physical properties
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24
Q

what are the liquids in zinc phosphate cement?

A

aqueous solution of phosphoric acid
oxides which buffer the solution
-aluminium oxide
-zinc oxide

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25
Q

what are the 2 reactions of zinc phosphate?

A

acid base

hydration

26
Q

what are the problems with zinc phosphate cement?

A 
initial pH 2
exothermic setting reaction
not adhesive
not cariostatic
final set takes 24 hrs
brittle
opaque
27
Q

describe the setting of zinc phosphate

A

aluminium oxide prevents crystalisation leading to amorphous glassy matrix of acid salt surrounding unreacted ZnO powder
matrix almost insoluble, porous contains free water from setting reaction
cement subsequently matures binding water leading to strong, less porous material

28
Q

what is zinc polycarboxylate cement?

A

similar to zinc phosphate but phosphoric acid replaced by polyacrylic acid

29
Q

what are the advantages of zinc polycarboxylate cement?

A

bonds to tooth surfaces like glass ionomer
less reaction heat
pH low to begin but becomes neutral faster
cheap

30
Q

what are the disadvantages 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
31
Q

what are the uses of ZOE and related materials?

A 
linings in deep cavities
-under amalgam
temporary restorations
root canal sealer
periodontal dressings
32
Q

what is the reaction of ZOE?

A

acid base
base is ZnO
acid is eugenol

33
Q

describe the setting reaction of ZOE

A

chelation reaction of zinc oxide with eugenol to form zinc eugenolate matrix
matric bonds unreacted ZnO particles

34
Q

what are the properties of ZOE?

A 
adequate working time
relatively rapid setting time
low thermal conductivity
low strength (20MPA)
radiopaque
35
Q

what are the consequences of ZOE high solubility?

A

eugenol constantly released
eugenol replaced by water -> disintegration of the material
eugenol when liberated has obtundant effect on pulp and can reduce pain

36
Q

why should ZOE materials not be used under composite resin materials?

A

eugenol inhibits set of resin based materials

-softens and can cause discoloration

37
Q

describe resin modified ZOE

A 
resins added to powder and liquid
-PMMA 
-polystrene in kalzinol
do not take part on reaction but give a stronger backbone to set material
increases compressive strength (40MPa)
decreases solubility
38
Q

what are the powder components of EBA cement?

A

ZnO 65%
quarts/alumina 35%
hydrogenated rosin 6%

39
Q

what are the liquid components of EBA cement?

A

eugenol 37%

ethoxybenzoic acid EBA 63%

40
Q

describe EBA setting

A

as with ZOE but EBA

-encourages crystalline structure which imparts greater strength to the set material

41
Q

what are the properties of EBA?

A

stronger that ZOE/resin modified ZOE (60MPa)

less soluble

42
Q

why are lining materials needed?

A

restoratives:

  • may not make intimate contact w/ tooth surface
  • heat released during setting/curing
  • release of chemicals
  • pulpal irritant
43
Q

what is the function of lining material?

A

prevents gaps

acts as a protective barrier

44
Q

what is a cavity base?

A

thick mix placed in bulk
dentine replacement used to minimise bulk of material or block out undercuts
more common in metal rest.

45
Q

what is a cavity lining?

A

thin coating over exposed dentine

46
Q

what does a liner protect the pulp from?

A

chemical stimuli from unreacted chemicals in filling material
thermal stimuli eg exothermic setting
bacterial and endotoxins eg microleakage

47
Q

what is the therapeutic purpose of a liner?

A

to calm down inflammation w/i pulp and promote pulpal healing

48
Q

what is the palliative purpose of a liner?

A

to reduce px syptoms prior to definitive tx carried out

-common in reversible pulpitis

49
Q

what are the properties of lining materials

A 
ease of use
thermal properties
mechanical properties
radiopaque
marginal seal
solubility
cariostatic
biocompatible
compatible with rest material
50
Q

what is ease of use?

A

easy to mix
long working time
setting time short
-ideally command set

51
Q

what are thermal properties?

A

thermal conductivity should be low
thermal expansion coefficient should be similar to dentine
thermal diffusivity should be similar to dentine or lower

52
Q

what is thermal conductivity?

A

how well heat energy is transferred through a material

53
Q

what is thermal expansion coefficient?

A

change in length per unit length for a temp rise of 1 degree

ideally liner should match tooth

54
Q

what is thermal diffusivity

A

similar to conductivity

ideally as low as tooth

55
Q

what are mechanical properties?

A

high compressive strength
-allow placement w/o brealomg
modulus similar to dentine

56
Q

describe radiopaque

A

should be easy to see dif between lining and tooth

-easier to see if there is any leakage/secondary caries

57
Q

describe marginal seal

A

ideally lining should form a chemical bond to dentine

bond should be permanent and impenetrable

58
Q

what should solubility be?

A

low

59
Q

what is cariostatic?

A

fluoride releasing
antibacterial
prevents secondary caries

60
Q

what is biocompatibility?

A 
non-toxic
not damaging to pulp
-pH
-excessive heat
low thermal conductivity

BDS2 CDS DMS (16 decks)

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