Endodontic Materials

Question 1

What are endodontic files used for?

Answer 1

The mechanical part of chemo-mechanical disinfection.
- remove hard and soft tissues, remove micro-organisms, make space for disinfectants/medicaments, create appropriate shape for obturation.

Question 2

What is plastic deformation?

Answer 2

The stress applied to the material has overcome the elastic limit and the material will no longer go back to its original shape.

Question 3

What is elastic deformation?

Answer 3

The stress applied to the material is less than the elastic limit and so, once the stress has been removed, the material will go back to its original shape.

Question 4

What is the plastic limit?

Answer 4

The point at which a plastic deformed material breaks.

Question 5

What is the elastic limit?

Answer 5

A set value representing the maximal strain that when applied to a file, allows the file to return to original dimensions.

Question 6

What is cyclic fatigue?

Answer 6

Instrument is freely rotating in a curvature, generates tension/compression cycles from different sides of the instrument.

Question 7

What is torsional fatigue?

Answer 7

Bonding of an instrument at one point while the other point is rotated.
Rotated past the point of which it can return to it’s original form and then eventually fractures.

Question 8

What material are endodontic files made from?

Answer 8

Stainless steel or Nitinol (nickel titanium alloy).

Question 9

What compound is present over the outer layer of stainless steel?

Answer 9

Chromium oxide- prevents rusting.

Question 10

How are metals strengthened in endodontic files?

Answer 10

Work hardening.

Question 11

What is work hardening?

Answer 11

Strengthening of a metal by plastic deformation.
Crystal structure dislocation, the dislocations interact and create obstructions in the crystal lattice.
Resistance to dislocation formation develops.
Hardens the instrument.

Question 12

What property of Nitinol is present, that is not present in stainless steel?

Answer 12

Super-elasticity.
- does not result in usual proportional strain.

Question 13

What is shape memory?

Answer 13

Materials that can be deformed at one temperature but when heated or cooled, return to their original shape.

Question 14

What is the role of an irrigant in endodontic treatment?

Answer 14

Facilitate removal of debris
Lubrication
Dissolution of organic and inorganic matter
Kill bacteria/yeasts/viruses
Biofilm disruption

Question 15

What material is used as an irrigant in endodontic treatment?

Answer 15

Sodium hypochlorite

Question 16

What factors are important for sodium hypochlorite function?

Answer 16

Concentration
Volume
Mechanical agitation
Exchange

Question 17

What does sodium hypochlorite do during endodontic treatment?

Answer 17

Antibacterial, removes bugs from the canal.

Question 18

Why must you remove the smear layer prior to obturation?

Answer 18

Smear layer is formed by organic material and inorganic dentinal debris.
If you do not remove the smear layer, it prevents sealer penetration.

Question 19

What material is used to remove the smear layer during endodontic treatment?

Answer 19

17% EDTA for 1 minute as the penultimate rinse.

Question 20

Why should sodium hypochlorite and EDTA never be in the same call at the same time?

Answer 20

Forms para-chloroaniline.
This is cytotoxic and carcinogenic.

Question 21

What material is used for obturation canals?

Answer 21

Gutta Percha

Question 22

What is Gutta percha made from?

Answer 22

20% gutta percha
65% zinc oxide
10% radio pacifiers
5% plasticisers

GP is a polymer of the same monomer- isoprene

Question 23

What are the ideal properties of an obturation material?

Answer 23

Easily manipulated
Dimensionally stable
Seals the canal laterally and apically
Non-irritant
Impervious to moisture
Unaffected by tissue fluids
Inhibits bacterial growth
Radiopaque
Easily removed if necessary

Question 24

What is the function of a sealer?

Answer 24

Seals the space between dentinal wall and the core.
Fills voids and irregularities in canal, lateral canals and between GP points.

Question 25

What are the ideal properties of a sealer?

Answer 25

Good adhesion
Radiopaque
Easily mixed
No shrinkage on setting
Bacteriostatic or does not encourage growth
Slow set
Insoluble in tissue fluids
Tissue tolerant
Soluble on retreatment

Question 26

What materials can be used as a sealer?

Answer 26

ZOE
Glass ionomer
Epoxy resin

Question 27

What are bioceramic sealers?

Answer 27

Calcium Silicate

Can be difficult to retreat a canal that has been previously treated with this.

Question 28

What is an example of a bioceramic cement?

Answer 28

Biodentine- calcium silicate cement.

Question 29

What is biodentine used for?

Answer 29

Direct and indirect pulp cap
Treatment of root perforations or plural floors
Internal and external resorption
Apexification
Retrograde root canal obturation
Pulpotomy
Temporary feeling of cavities

Question 30

How long does Biodentine take to set?

Answer 30

12-15 minutes

Question 31

How long does biodentine need to be mixed for?

Answer 31

30 seconds.

Question 32

What does biodentine stimulate?

Answer 32

Stimulates tertiary dentine formation in a vital pulp.
Releases calcium and hydroxyl ions to form hydroxyapatite crystals on the surface after contact with phosphate containing liquids.

Question 33

What are the advantages of using biodentine over calcium hydroxide?

Answer 33

Mechanically stronger
Less soluble
Produces tighter seals

Question 34

What two approaches can be adopted to restore a tooth that has been treated with biodentine?

Answer 34

1. Wait 12-15 minutes once biodentine is set and then restore with composite in the same appointment.
2. Apply biodentine and then wait 48 hours to 6 months later to cut back the biodentne and then restore with composite.