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3 DMS > Endodontic Materials > Flashcards

Endodontic Materials Flashcards

1
Q

What are the uses of endo instruments?

A

Mechanical phase of chemomechanical disinfection
Metal files used to remove soft and hard tissues
Removes micro-organisms
Creates spaces for disinfectants/medicaments
Creates appropriate shape for obturation

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2
Q

What is a stress concentration point?

A

Abrupt changes in the geometric shape of a file that leads to a higher stress at that point

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3
Q

What is plastic deformation?

A

Permanent bond displacement occurring when elastic limit is exceeded

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4
Q

What is plastic limit?

A

The point at which a plastic deformed file breaks

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5
Q

What are the different types of failure of endo instruments?

A

Cyclic fatigue
Torsional fatigue

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6
Q

What are the different types of endo instruments?

A

Manually operated
Low-speed
Engine driven nickel-titanium
Engine driven that adapt to canal shape
Engine driven reciprocating instruments
Ultrasonic instruments

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7
Q

Describe work hardening

A

Strengthening of a metal by plastic deformation
Crystal structure dislocates
Dislocations interact and create obstructions in crystal lattice
Resistance to dislocation formation develops
Observed work hardening

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8
Q

What is Nitinol?

A

Equiatomic alloy of Ni and Ti
Super elastic

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9
Q

What are shape memory alloys?

A

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

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10
Q

What are the components of an endo rotary instrument?

A

Taper
Flute
Leading/cutting edge
Land
Relief
Helix angle

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11
Q

What are the properties of irrigants?

A

Facilitate removal of debris
Lubrication
Dissolution of organic and inorganic matter
Penetration to canal periphery
Kill bacteria/yeast/viruses
Biofilm disruption
Biological compatibility
Does not weaken tooth structure

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12
Q

Describe Sodium Hypochlorite (NaOCl)

A

NaOCl ionises in water into NA+ and OCl-
Responsible for antibacterial activity

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13
Q

What factors affect NaOCl function?

A

Concentration
Volume
Contact
Mechanical agitation
Exchange

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14
Q

Describe the smear layer formed during prep for obturation

A

Organic pulpal material and inorganic dentinal debris
Bacterial contamination interferes with disinfection
Prevents sealer penetration

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15
Q

How is the smear layer removed?

A

17% EDTA
10% Citric acid
MTAD
Sonic and ultrasonic irrigation

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16
Q

Give examples of irrigant interactions?

A

Interaction with NaOCl forms para-chloroaniline
This is cytotoxic and carcinogenic

17
Q

What are the ideal properties of an obturation material?

A

Easily manipulated with good working time
Dimensionally stable
Seals the canal laterally and apically
Non-irritant
Moisture resistant
Unaffected by tissue fluids
Inhibits bacterial growth
Radiopaque
Doesn’t discolour tooth
Sterile
Easily removed if necessary

18
Q

What is found in gutta percha?

A

20% Gutta-percha
65% Zinc oxide
10% Radiopacifiers
5% Plasticisers

19
Q

Describe the phases of gutta percha

A

Exists in two crystalline forms - alpha and beta
Alpha phase is naturally occurring
When heated above 65ºC melts into amorphous phase
If cooled slowly returns to alpha phase
If cooled rapidly recrystallises as beta phase

20
Q

What are the functions of sealers?

A

Seals space between dentinal wall and core
Fills voids and irregularities in canal, lateral canals and between gutta percha points used in lateral condensation
Lubricates during obturation

21
Q

What are the ideal properties of a sealer?

A

Tacky to provide good adhesion
Establishes a hermetic seal
Radiopaque
Easily mixes
No setting shrinkage
Non-staining
Bacteriostatic or doesn’t encourage growth
Slow set
Insoluble in tissue fluids
Soluble on re-treatment

22
Q

What different sealers are commonly used?

A

Zinc oxide eugenol
GI
Resin eg - Epiphany, EndoRez
Calcium silicate

23
Q

Why are medicated sealers not used?

A

Some contain paraformaldehyde, lead and mercury which are toxic

24
Q

What are the advantages a of zinc oxide eugenol sealer?

A

Can be modified with germicides
Good dentine adhesion
Antimicrobial effects

25
Q

What are the advantages of a GI sealer?

A

Dentine bonding properties

26
Q

What are the disadvantages of GI sealers?

A

Removal upon retreatment is difficult
Minimal microbial activity
Little clinical data to support use

27
Q

What are the advantages of resin sealers?

A

Good sealing ability
Good flow
Biocompatible
Good radiopacity

28
Q

What are the advantages of calcium silicate sealers?

A

High pH - 12.8 during initial 24 hours of setting
Enhanced biocompatibility
Doesn’t shrink on setting
Excellent sealing ability
Easy to use

3 DMS (8 decks)

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