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BDS3 DMS > Endo Materials > Flashcards

Endo Materials Flashcards

1
Q

When would you use chlorhexidine 2% as an irrigant?

A

When sodium hypochlorite is contra-indicated or you suspect iatrogenic damage

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2
Q

What is cyclic fatigue?

A

Cyclic fatigue occurs when there is repeated compression and tension cycles in the instrument that occur from rotation.
Causes unwanted work hardening and eventual failure.

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3
Q

What is torsional fatigue?

A

When the tip of an endo instrument gets stuck in a canal but the motor continues to rotate.
Eventually leads to fracture

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4
Q

Why is NiTi a desirable endo instrument?

A

It has super-elasticity - application of stress does not result in usual proportional strain.
Compared to SS instrument NiTi has:
Increased flexibility
Increased elasticity
Improved resistance to cyclic fatigue

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5
Q

What happens to a NiTi instrument when the temperature changes?

A

The characteristics change when the temperature changes.
Crystal lattice structure changes from martensite to austenite.

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6
Q

What is the main purpose of an irrigant in endodontics?

A

An anti-microbial agent that dissolves organic tissue within the root canal space.

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7
Q

What pH is sodium hypochlorite?

A

pH 9

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8
Q

Why must the smear layer be removed in endodontics?

A

Must be removed to facilitate adequate disinfection and sealer penetration into dentinal tubules

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9
Q

Why do you have to use EDTA following use of sodium hypochlorite?

A

Sodium hypochlorite does not completely remove smear layer by itself.

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10
Q

What are the properties of an ideal obturation material?

A

Easily manipulated with ample working time
Seals canal laterally and apically
Non-irritant
Impervious to moisture
Radio-opaque
Sterile
Easily removed if necessary

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11
Q

What is the most common obturation material used in dentistry and what form is it?

A

Gutta-percha
Beta form - rapidly cooled GP that re-crystallises

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12
Q

What are the functions of sealer?

A

Seals space between dentinal wall and core - creates a fluid-tight seal

Fills voids and irregularities in canal, lateral canals and between GP points used in lateral condensation

Lubricates during obturation

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13
Q

Give 2 examples of sealers used in dentistry?

A

Zinc oxide and eugenol
Epoxy resin - AH plus

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14
Q

What are some properties of the ideal sealer?

A

Tacky to provide good adhesion/ seal
Radio-opaque
Easily mixed
No shrinkage on setting
Slow set
Soluble on re-treatment
Bacteriostatic - does not encourage growth

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15
Q

What is the main problem with zinc oxide and eugenol?

A

Dissolution of material with time
Apical seal is diminished over time

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16
Q

What is a common material used for root-end filling?

A

MTA

17
Q

What is the definition of working length?

A

The distance from a coronal reference point to the point at which the canal prep and obturation should terminate -between 1-2mm short of the apical foramen

18
Q

What are 2 reasons to change the estimated working length to corrected working length during instrumentation?

A

Root curvature
Remnants of previous obturation materials in the canal

19
Q

What are the timings for irrigation?

A

NaOCl 3% - 3ml for 1 minute
EDTA 17% - 3ml for 1 minute
NaOCl 3% - 30ml for 10 minute - soak

20
Q

Why is non-setting CaOH an ideal inter-appointment medicament?

A

Highly radio-opaque
Anti-microbial

21
Q

What are reasons for obturating?

A

To prove you got to working length
To seal dentinal tubules and canal space to prevent bacterial ingress
To eliminate space in the canal

22
Q

What is cold lateral compaction?

A

Placing a single cone of GP with sealer in prepared canals and adding secondary GP cones that are compacted with a spreader.

23
Q

What are the constituents of GP?

A

GP 20%
Zinc oxide 65%
Radio-pacifiers 10%
Plasticisers 5%

24
Q

Why use sealer during CLC?

A

Sealer fills space/ voids between GP points
Lubricates for easier insertion of the GP points
Penetrates dentinal tubules, and accessory canals where the GP cannot

25
Q

What component in stainless steel Endo-files are for corrosion resistance?

A

Chromium

BDS3 DMS (7 decks)

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