DML2: Cavity lining materials Flashcards Preview

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Flashcards in DML2: Cavity lining materials Deck (43)
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1

What are cavity lining materials

- Intermediate restorative materials lining the cavity
- Applied before the placement of the restorative
- They can remain permanently within deep cavities

They are protective, palliative and therapeutic barriers for penetration through the dentinal tubules for pulp protection

2

What factors should be taken into account for cavity linings

- cavity position
- tissue conduction
- cavity size and depth
- oral health
- restorative to use

3

What are the different options for cavity lining materials (7)

1. Varnishes
2. Calcium hydroxide cements
3. Zinc oxide based cements
4. GICs
5. Resin modified GICs
6. Visible light cured resins
7. Calcium silicate based cements

4

How do cavity liners protect the pulp

Because they can protect the pulp from the leakage of unpolymerised resin at the margin

5

What can provide the pulp with chemical protection

Cavity varnish

6

What provides the pulp medication

Cavity liners

7

What provides the pulp with thermal and electrical protection

Cavity liners or base

8

What provides the pulp with mechanical protection

Cavity base

9

What is cavity varnish

This is the thinnest cavity liner which is painted onto the cut surface and is designed to act as a barrier to penetration of chemicals by doing the following
- seal dentinal tubules
- reduce diffusion through dentine
- reduce microleakage

It doesnt provide added strength because it isnt chemically boned to dentine

10

What are cavity varnishes composed of

1. Natural resins e.g. copal
2. Synthetic resins e.g. polystyrene
3. Solvent e.g. alcohol, acetone, ether
4. Some contain calcium/zinc hydroxide

11

Why do cavity varnishes contain solvents

Because this allows the varnish to be painted on with a brush onto cut surfaces and the solvent will then evaporate

12

What is a cavity liner

This is thicker than cavity varnish and will seal the exposed dentine = 0.5mm

It promotes health of pulp as it adheres to the tooth structure and has antibacterial action

13

Give examples of cavity lining materials

1. Calcium hydroxide (for pup capping)
2. ZOE
3. Zinc oxide non-eugenol

14

Why is calcium hydroxide cavity lining used for pulp capping

Because it doesn't contain eugenol which cannot be placed directly onto the pulp

15

What is a cavity base

A thick mix which is placed in bulk and can act as a dentine replacement = >0.75mm

This is used in deep caries as it reduces the bulk of the restorative

It is insulating and of higher strength and blocks out undercuts

16

Give examples of cavity base materials

1. Reinforced ZOE
2. Visible light cured resins
3. Zinc phosphate
4. Zinc polycarboxylate
5. Glass ionomer
6. Resin modified glass ionomer

17

What is in the powder component of ZOE cements

- ZnO (MgO)
- SiO2, Al2O3 fillers
- Dicalcium phosphate, mica or rosin (to improve mixing)
- Zinc salts (accelerates set)

18

What is in the liquid component of ZOE cements (4)

- eugenol
-olive oil (modifying viscosity)
- acetic acid 1% (accelerates set)
- water (small amount is essential to setting)

19

What is the ZOE cement setting reaction

An acid-base reaction to form zinc eugenolate = chelate complex; this is initiated by water which is also a byproduct of this reaction

20

What is the issue with the zinc eugenolate complex not being stable

The setting reaction will reverse in the presence of excess water

21

How is ZOE mixed

- on a glass slab / oil resistant paper
- incremental powder addition (2)
- mixing time of 60-90 seconds
- 2-3 mins working time
- sets in less than 5 mins

22

What produces a faster and stronger set in ZOE cements

A higher powder to liquid ratio and smaller particle size

23

What are the advantages of ZOE cements

- easy to mix an handle
- fast set in mouth due to temp and moisture which both accelerate set
- non-irritant pH (close to neutral)
- obtundant (calming effect on pulp due to eugenol when placed on dentine)
- good sealing characteristics
- protects pulp from chemical irritation
- good thermal insulator

24

What are the disadvantages of ZOE cements

1. Low compressive + tensile strengths 15-25MPa
2. High water solubility
3. Eugenol is a potential allergen and mild irritant
4. Eugenol inhibits vinyl polymerisation (-C=C-) so cannot be used under composites and compomers

25

What is reinforced ZOE

e.g. IRM

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

26

What does the addition of powder, coated particles and styrene or MMA result in in reinforced ZOE composites

1. Increased compressive strength 40MPa
2. Increased tensile strength
3. Reduced water solubility

27

What are the uses of ZOE cements

- Used where strength isnt important but low irritancy is
- Not in direct pulpal contact
- Thermal insulating base = cavity lining
- Temporary restorations
- Intermediate restorations
- Long-term cementation
- Endodontic useage

28

What is a ZOE cement alternative

Ethoxybenzoic acid cement = EBA

29

What is in the powder part of EBA cements

1. ZnO = 60-75%
2. Filler SiO2, Al2O3 = 20-35%
3. Hydrogenated rosin = 6% (helps add viscosity)

30

What is in the liquid part of EBA cements

1. 50-60% of the eugenol in ZOE is replaced by ethoxybenzoic acid
2. 35-50% eugenol