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3d. BDS3 CDS Endodontics > L20. Instrumentation of the Root Canal System > Flashcards

L20. Instrumentation of the Root Canal System Flashcards

1
Q

What is the purpose of instrumentation of the root canal?

A
  • Remove infected soft and hard tissue;
  • Creating space for irrigants to access apical space;
  • Creating space for medicaments and subsequent obturation;
  • Retain the integrity of radicular structures.
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2
Q

What are Herbert Schilder’s design objectives?

A
  • Create a continuously tapering funnel shape;
  • Maintain apical foramen in original position;
  • Keep apical opening as small as possible.
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3
Q

What is the apical foramen?

A

An opening at the apex of the tooth where the nerves and blood enter to supply the pulp

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4
Q

What are the risks of over enlarging the apical foramen?

A
  • Extrusion of irrigants into the periapical tissues;

- Effecting the long-term prognosis of the tooth (harder to create an apical seal).

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5
Q

What are the chemical aims of chemomechanical disinfection? [irrigation]

A
  • Kill microorganisms;

- Remove smear layer.

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6
Q

What are the mechanical aims of chemomechanical disinfection? [filing]

A
  • Shape the canal;
  • Allow delivery of NaOCl to working length;
  • Create shape to obturate.
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7
Q

Why is it important to consider a minimum apical diameter during preparation of a root canal?

A

To deliver NaOCl to complex structures within the root canal system

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8
Q

What is the estimated working length?

A
  • Maximum estimated length at which instrumentation should be carried out;
  • Obtained via pre-operative radiographs (distance between coronal reference point and apex -1mm).
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9
Q

What is the corrected working length?

A
  • Length at which instrumentation and subsequent obturation should be carried out;
  • Obtained via electronic apex locator and/ or working length radiograph.
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10
Q

What is the master apical file?

A

The largest diameter of file taken to working length (therefore represents the final prepared size of the apical portion of the canal)

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11
Q

What are the different types of file motions used in endodontics?

A
  • Filing;
  • Reaming (warning);
  • Watch-winding;
  • Balanced forced motion;
  • Envelope of motion.
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12
Q

What is the watch winding technique?

A
  • Back and forward oscillation of 30-60 degrees;
  • Light apical pressure;
  • Effective with K files;
  • Useful for small files.
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13
Q

What is the balanced force technique?

A
  • 90 degrees clockwise;
  • Apical pressure;
  • With continued pressure, 180 degrees anticlockwise;
  • Do this 1-3 times;
  • Effective with larger K files and protaper files.
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14
Q

What is the envelope of motion technique?

A

360 degree rotation around the canal

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15
Q

What’s involved with a modified double flare technique?

A
  • Balanced force;

- Step-back.

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16
Q

What are proper instruments made from?

A

Nickel titanium

17
Q

What are barbed broach instruments used for?

A

Extripating pulp/ materials from the root canal, not to be engaged with canal walls

18
Q

What is the ISO colour code?

A
  • White (15, 45);
  • Yellow (20, 50);
  • Red (25, 55);
  • Blue (30, 60);
  • Green (35, 70);
  • Black (40, 80).

N.B. up in 5s but no 65 or 75

19
Q

What length of cutting flutes do ISO-sized stainless steel instruments have?

A

16mm

20
Q

What are Hedström files used for?

A

GP removal in cases of retreatment (filing motion, cuts on withdrawal)

[can also be used to remove fractured instruments]

21
Q

Describe the shape, use and angle (to the long axis) of a reamer instrument.

A
  • Triangular cross-section;
  • Cutting edge is almost parallel to long axis of instrument;
  • Rotated 1/4 to a 1/2 clockwise;
  • Cuts as it is advanced.
22
Q

Describe the shape, use and angle (to the long axis) of a K-file instrument.

A
  • Square cross-section;
  • Cutting edge almost perpendicular to long axis of instrument;
  • Used in filing or balanced force motion;
  • Withdrawn while applying lateral pressure.
23
Q

What are the advantage of nickel-titanium instruments over stainless steel?

A
  • Superelasticity of Niti;
  • Higher resistance to fatigue;
  • Better cutting efficiency;
  • Good for curved canals without exerting too much lateral force (leading to ledges).
24
Q

What are the disadvantages of nickel-titanium instruments over stainless steel?

A
  • Can still fracture (usually operator’s fault!);
  • Expense;
  • Difficult to access posterior teeth;
  • Unsuitable for complex canal anatomy.
25
Q

What is the sequence of protaper files?

A
  • S1 (purple), coronal third;
  • S2 (white), middle third;
  • Sx (orange), auxiliary orifices;
  • F1 (yellow), 0.20mm tip;
  • F2 (red), 0.25mm tip;
  • F3 (blue), 0.30mm tip;
  • F4 (black), 0.40mm tip;
  • F5 (yellow), 0.50mm tip.

[S: shaping, F: finishing]

26
Q

What is true reciprocation, with regards to filing motion techniques?

A

Equal clockwise and anticlockwise rotation

27
Q

What type of access should be created when using a rotary instrument? (Gates Glidden/ protaper)

A

Straight line access

28
Q

What guidelines must be considered when using a rotary instrument?

A
  • Straight line access (so files don’t go in at too steep an angle);
  • Cross-sectional diameter (don’t put too big a instrument into canal too early);
  • Root canal system anatomy;
  • Speed and sequencing (torque);
  • Lubrication and a ‘light touch’ (don’t drive instrument into tooth).
29
Q

Why is it important to create a glide path?

A
  • Confirm straight-line access;
  • Explore anatomy (w small K file);
  • ISO-10, watch winding technique and appropriate irrigation;
  • Repeat with ISO-15 and 20.
30
Q

What motion is used in RECIPROC instrumentation (controlled by computer)?

A
  • Like balance force;
  • 150 degrees anticlockwise;
  • 30 degrees clockwise.
31
Q

What are the three RECIPROC file sizes?

A

R25, 40 and 50

32
Q

What is latency filing?

A

Use of a small file to just pass through the apical foramen to maintain communication with periapical tissues

33
Q

What is cyclic fatigue?

A
  • Generation of tension/ compression cycles;
  • Leading to fatigue;
  • Eventually failure.
34
Q

Describe the progress to the plastic phase, through torque.

A
  • When an instrument binds, exerted to torque;
  • Elastic phase (up to elastic limit) where stress is reversible;
  • Elastic limit at 400 degrees;
  • After this is the plastic phase where instrument starts to deform;
  • The more stress applied, the more likely it is to fracture.

3d. BDS3 CDS Endodontics (8 decks)

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