Cavity lining materials

Question 1

what materials are placed into cavities?

5

Answer 1

composite resin
glass ionomer
amalgam
precious metal
ceramic

Question 2

what are the disadvantages of restoratives?

3

Answer 2

may not make immediate contact with the tooth surface - secondary caries
heat released during setting/curing can damage pulp
release of chemicals may irritate pulp

Question 3

what do cavity lining materials do?

2

Answer 3

prevent gaps
act as a protective barrier

Question 4

what are the differences between cavity bases and linings?

Answer 4

cavity base
* thick mix placed in bulk
* dentine replacement to minimise bulk of material or block out undercuts
cavity lining
* thin coating over exposed dentine
* dentine sealer to promote health of pulp

Question 5

what is the purpose of a cavity liner?

3

Answer 5

• pulpal protection from chemical stimuli, thermal stimuli and bacteria and endotoxins
• therapeutic to reduce inflammationn within pulp
• palliative to reduce symptoms prior to definitive treatment

Question 6

what are the properties of lining materials?

9

Answer 6

• ease of use
• thermal properties
• mechanical properties
• radiopaque
• marginal seal
• solubility
• cariostatic
• biocompatible
• compatible with restorative materials

Question 7

how are lining materials easy to use?

3

Answer 7

easy to mix
long working time to allow easy placement
short setting time

Question 8

what are the thermal properties of lining materials?

3

Answer 8

low thermal conductivity
similar thermal expansion coefficient to dentine
similar or lower thermal diffusity to dentine

Question 9

what are the mechanical properties of lining materials?

2

Answer 9

high compressive strength
modulus similar to dentine

Question 10

why should lining materials be radiopaque?

2

Answer 10

should be easy to see the difference between lining and tooth
easier to see of there are any leakages or secondary caries

Question 11

why should the lining material be a marginal seal?

Answer 11

should form a chemical bond to dentine which is permanent and impermeable

Question 12

how soluble should a lining material be?

Answer 12

low solubility

Question 13

how is a lining material cariostatic?

3

Answer 13

releases fluoride
antibacterial
prevents secondary caries around restoration

Question 14

how is the lining material biocompatible?

3

Answer 14

non-toxic
doesn’t damage pulp (ph neutral, no excess heat when setting)
low thermal conductivity

Question 15

what types of materials can be bases or liners?

4

Answer 15

setting calcium hydroxide: liner
zinc oxide based cements: base
glass ionomer and resin modified glass ionomer: base or liner
palliative cements: base

Question 16

what kind of reaction occurs with setting calcium hydroxide and what is the reaction between? what does it result in?

3

Answer 16

setting reaction is a chelation reaction
between ZnO (filler material) and butylene glycol disalicylate (reactive element)
results in a cement with an initia pH of around 12

Question 17

how does setting calcium hydroxide work?

2

Answer 17

• kills cariogenic bacteria as creates a highly alkaline environment
• irritates the odontoblast layer to start making reparative tertiary dentine (calcified bridge forms at base - calcium comes from pulp)

Question 18

what are the properties of setting calcium hydroxide?

5

Answer 18

quick setting time ✓
radiopaque ✓
easy to use ✓
low compressive strength ✖
unstable and soluble ✖

soluble=if cavity leaks then lining disappears-may be due to wet dentine

Question 19

what are examples of zinc oxide based cements?

5

Answer 19

zinc phosphate
zino polycarboxylate
zinc oxide eugenol (ZOE)
resin modified ZOE
ethoxybenzoic acid (EBA) ZOE

Question 20

what makes up the powder and liquid components of zinc phosphate cement?

Answer 20

powder
* zinc oxide
* magnesium dioxide
* alumina and silica oxides
liquid
* phosphoric acid (aq)
* oxides which are buffers - aluminum and zinc oxides

aluminium oxide - even consisteny, zinc oxide - slows reaction

Question 21

what reaction occurs with zinc phosphate cement and what is the end product?

3

Answer 21

ZnO + 2H3PO4 -> Zn(H2PO4)2 + H2O (acid base reaction)
ZnO + Zn(H2PO4)2 + H2O -> Zn3(H2PO4)2.4H2O (hydration)
crystalised phosphate matrix produced

Question 22

what are problems with the zinc phosphate cement?

7

Answer 22

• low initial pH around 2 = pulpal irritation
• exothermic setting reaction (gives off heat)
• not adhesive to tooth or restoration
• not cariostatic
• final set takes 24 hours
• brittle
• opaque

Question 23

what are the advantages with zinc polycarboxylate cement?

4

Answer 23

• bonds to tooth surface
• less heat from reaction
• low initial pH but returns to neutral quickly
  cheap

Question 24

what are the disadvantages with zinc polycarboxylate cement?

5

Answer 24

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

Question 25

what can ZOE and related materials be used for? | 4

Answer 25

* linings/base in deep cavities * temporary restorations * root canal sealer * periodontal dressings

Question 26

what is and what kind of reaction occurs with ZOE? | 2

Answer 26

acid base reaction and chelating reaction ZnO + 2C10H12O2 -> C20H24O5Zn zinc oxide base + eugenol acid = zinc oxide eugenolate (ZOE)

Question 27

what are the properties of ZOE? | 6

Answer 27

adequate working time ✓ relatively rapid setting time ✓ low thermal conductivity ✓ radiopaque ✓ low strength ✖ high solubility - eugenol is constantly released and replaced with water which disintegrates it but reduced pulp pain ✓✖

Question 28

what is ZOE not used with?

Answer 28

composite resins as eugenol inhibits setting

Question 29

what is the difference between resin modified ZOE and ZOE? | 4

Answer 29

resins added to powder and liquid * gives a stronger backbone * increases compressive strength * greatly decreases solubility

Question 30

what are the consituents of ethoxybenzoic cement (EBA ZOE)?

Answer 30

powder * ZnO * quartz or alumina * hydrogenated rosin liquid * eugenol * ethoxybenzoic acid

Question 31

what is the setting reaction for EBA ZOE?

Answer 31

same as with ZOE but with EBA ZnO + C10H12O2 + C9H10O3 -> C19H22O6Zn zinc oxide base + eugenol + ethoxybenzoic acid = ethoxybenzoic acid zinc oxide eugenolate

Question 32

what is the importance of EBA and quartz/alumina in EBA ZOE? | 2

Answer 32

EBA - reactive quartz/alumina - reinforcing

Question 33

what are the properties of EBA ZOE | 2

Answer 33

* stronger than ZOE or RMZOE * less soluble

Question 34

what are the advantages of glass ionomer liners? | 6

Answer 34

* bonds to and seals dentine * bonds to composite resin * releases fluoride over time and can be cariostatic * easy to use * light cured - command set * long working time and short setting time

Question 35

what are the properties of glass ionomer liners? | 6

Answer 35

* thermal conductivity and diffusivity lower than dentine * thermal expansion similar to dentine * compressive strength higher than ZnO materials * radiopaque * good marginal seal * less soluble than other liners

Question 36

what are the guidelines for lining? | 3

Answer 36

* cavities in dentine - RMGIC lining fro amalgam and larger composite cavities * calcium hydroxide should only be used when cavity reaches pulp * calcium hydroxide should be covered with RMGIC prior to final restoration