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BDS3 Endodontics > Instrumentation of the root canal system > Flashcards

Instrumentation of the root canal system Flashcards

1
Q

What is the purpose of instrumentation of the root canal? (4)

A
  • Remove infected soft and hard tissue
  • Give disinfecting irrigants access to apical canal space
  • Create space for the delivery of medicaments and subsequent obturation
  • Retain the integrity of radicular structures
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2
Q

What do you want to achieve when instrumenting a canal? (4)

A
  • Get all the stuff out
  • Widen it to allow you to put bleach in
  • Make it easier to fill
  • Keep it the same shape as before
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3
Q

What are the design objectives when doing RCT? (3)

A
  • Create a continuously tapering funnel shape
  • Maintain apical foramen in original position
  • Keep apical opening as small as possible
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4
Q

What is the purpose of the chemo part in chemo-mechanical preparation? (2)

A
  • Irrigate to kill microorganisms

- Remove smear layer

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5
Q

What is the purpose of the mechanical part in chemo-mechanical preparation? (2)

A
  • Prepare shape

- Flush out debris and microorganisms when we irrigate

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6
Q

What is the aim of the mechanical part of chemo-mechanical disinfection? (3)

A
  • Shape the canal
  • Allows delivery of sodium hypochlorite to working length
  • Creates shape to obturate
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7
Q

What are the possible challenges of root canal preparation? (3)

A
  • The root canal system is very complex
  • The number, length, curvature and diameter of canals can vary considerably
  • Vertucci classification
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8
Q

What is the estimated working length?

A
  • Estimated length at which instrumentation should be limited. Obtained by measuring pre-operative radiograph to determine distance between coronal reference point and radiographic apex then subtracting 1mm
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9
Q

What is the corrected working length?

A
  • Length at which instrumentation and subsequent obturation should be limited. Obtained by the use of an electronic apex locator and/or working length radiograph
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10
Q

What is the master apical file?

A
  • The largest diameter file taken to working length and therefore represents the final prepared size of the apical portion of the canal at the working length
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11
Q

What are the different types of motion? (5)

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

Explain the ‘watch-winding’ motion?

A
  • Backward and forward oscillation of 30-60 degrees

- Light apical pressure

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13
Q

Which type of file works effectively with a watch winding motion?

A
  • K files
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14
Q

What is the watch-winding motion useful for?

A
  • Useful for passing small files through canals
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15
Q

Explain the balances force tehcnique?

A
  • Insert file and engage clockwise into the dentine 1/4 turn
  • With continued pressure go counter clockwise 1/2 turn to strip the dentine away
  • Do this 1-3 times before removing the file to remove debris and check the file
  • Remove
  • Clean
  • Reintroduce, working your way to WL
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16
Q

Explain the ‘envelope of motion’ movement?

A
  • Very important
  • Remembering that in a lot of endodontic treatment you find that you can place a file in the canal in a particular way but you have to debride dentine 360 degrees round the canal - not just one wall
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17
Q

What is the initiate irrigation protocol for the canal? (3)

A
  • EDTA for 17% for 1 minute
  • Sodium hypochlorite 3%, 30ml for 10mins
  • Slow injection, Don’t use thumb!
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18
Q

What is a ‘barbed broach’ used for?

A
  • Used for extirpating, NOT enlarging

- Spiky bit of metal - can be used to get rid of bits of debris out of the root canal system

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19
Q

How are ‘barbed broach’ files formed?

A
  • Formed from a tapered round shaft by lifting up portions of metal of the shaft almost at a right angle to the shaft
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20
Q

What MUST barbed broach files not engage?

A
  • Must not engage canal walls
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21
Q

What may happen if a barbed broach file is misused?

A
  • Extremely fragile instrument and will break easily if misused
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22
Q

How do the elevated barbs of the barbed broach instrument work?

A
  • The elevated barbs engage the pulp tissue and remove it from the canal
  • Use the largest size broach which will fit freely in the canal selected
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23
Q

What is another name for a K file?

A
  • ISO instruments
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24
Q

How long are the cutting flutes of ISO instruments?

A
  • All have 16mm cutting flutes
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25
Q

What is each ISO file named according to?

A
  • Named according to its diameter at the tip
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26
Q

What is the taper of ISO instruments?

A
  • Taper is 0.32 over the 16mm, or 0.02 per millimetre
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27
Q

What is the diameter of an ISO instrument at the end of the cutting surface closest to the handle?

A
  • Diameter = apical size + 0.32mm
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28
Q

What is the cross-sectional shape of a k-reamer instrument?

A
  • Triangle
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29
Q

What is the cross-sectional shape of a k-file instrument?

A
  • Square
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30
Q

What is the cross-sectional shape of a H-file instrument?

A
  • Comma (,) shaped
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31
Q

What kind of motion is used for a Hedstrom file?

A
  • Used in a filing motion, cuts on withdrawal
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32
Q

Do Hedstrom files have a good cutting efficiency?

A
  • Yes, have a good cutting efficiency but can cause iatrogenic damage
33
Q

Are Hedstrom files still used for canal preparation?

A
  • No
34
Q

What are Hedstrom files useful for?

A
  • Useful for removing GP or fractured instruments in cases of retreatment
35
Q

How are reamers manufactured?

A
  • Manufactured by twisting a tapered triangular shaft
36
Q

What are the cutting edges of reamers almost parallel to?

A
  • Almost parallel to the long axis
37
Q

How do we use reamers to allow us to get an effective cut? (2)

A
  • Rotated 1/4 to 1/2 turn clockwise to cut as advanced to length
  • Must be in contact with the walls of the canal in order to be effective, must not bind or it will break
38
Q

How are K files manufactured?

A
  • Manufactured by twisting or grinding a square tapered shaft (square cross-section)
39
Q

Why must we take care in instrumenting canals with k files, that you don’t try to put big instruments in too quickly?

A
  • As this is how ledges form and how you can create iatrogenic problems or the file can break in the canal
40
Q

What are the cutting edges of K files like?

A
  • Almost perpendicular to the long axis of the instrument
41
Q

What kind of motion is used for k files?

A
  • Can be used in a filing motion - advanced to the full working length rotated 1/4 to 1/2 turn clockwise, and withdrawn while applying lateral pressure. Repeated circumferentially until canal enlarged
42
Q

What are 2 properties of nickel-titanium alloy?

A
  • Shape memory effect after heat treatment

- Super-elasticity

43
Q

What is meant by super-elasticity of nickel-titanium alloy?

A
  • Can be strained more than other alloys before permanent deformation
44
Q

What does the super-elasticity of nickel-titanium alloys allow the files to do?

A
  • Allows NiTi files to be places in curved canals with less lateral forces exerted
  • Less transportation, zipping and ledging
  • More centrally placed preparation in harmony with the original canal shape
45
Q

What is the ‘taper’ of an endodontic rotary instrument?

A
  • Diameter change along the working surface
46
Q

What is the ‘flute’ of an endodontic rotary instrument?

A
  • Groove to collect dentine and soft tissue
47
Q

What is the ‘ledging/cutting edge’ of an endodontic rotary instrument?

A

Forms and deflects dentine chips

48
Q

What is the ‘land’ of an endodontic rotary instrument?

A

Surface extending between flutes

49
Q

What is the ‘relief’ of an endodontic rotary instrument?

A

Reduction in surface of land

50
Q

What is the ‘helix angle’ of an endodontic rotary instrument?

A

Angle cutting axis forms with long axis of file

51
Q

What does the ‘positive rake angle’ on an endodontic instrument do?

A
  • Provides the active cutting action of the K3
52
Q

What does the ‘wide radial land’ on an endodontic instrument do?

A
  • Provides blade support while adding peripheral strength to resist torsional and rotary stresses
53
Q

What does the ‘radial land relief’ on an endodontic instrument do?

A
  • Reduces friction on the canal wall
54
Q

What does the ‘third radial land’ on an endodontic instrument do?

A

Stabilises and keeps the instrument centred in the canal and minimises ‘over-engagement’

55
Q

What are the advantages of NiTi versus SS instruments? (4)

A
  • Increased flexibility in larger sizes and tapers
  • Increased cutting efficiency
  • If used appropriately good safety in use
  • Can be more user friendly with less instruments and simple sequences
56
Q

What are the disadvantages of NiTi preparation? (4)

A
  • Instrument fracture
  • Expense
  • Access can be difficult in posterior teeth
  • Unsuitable for complex canal anatomy
57
Q

What are the 3 protaper rotary instruments?

A
  • S1, S2 and Sx
58
Q

What is the S1 protaper instrument used for?

A
  • Used for the coronal third of the preparation
59
Q

What is the S2 protaper instrument used for?

A
  • Is for the middle third of the preparation
60
Q

What is the Sx protaper instrument used for?

A
  • This is an auxiliary file that you sometimes need to open up the orifice of the tooth (might use before the gates glidden)
61
Q

What are F files?

A
  • Finishing files
62
Q

What is an F2 equivalent to?

A
  • F2 has equivalent to an ISO 25 so 0.25mm

- All of the F files have an equivalent K file

63
Q

What is the downside of F files?

A
  • Downside of these is if have a particularly large root canal and find F5 (tip size of 0.5mm)has not engaged the dentine then perhaps you need to revert to a modified double flare technique to use a 60 or 70 ISO file to prepare the root canal
64
Q

What is the protaper sequence of the files that you would use?

A
  • K10
  • K15
  • S1
  • (Sx)
  • K10
  • K15
  • S1
  • S2
  • F1

Then if needed:

  • F2
  • F3
  • F4
  • F5
65
Q

What is true reciprocations?

A
  • This is equal clockwise/anticlockwise turning

- Mimics manual movement

66
Q

What does true reciprocation reduce the risks of?

A
  • Reduces risks associated with continuously rotating a file through canal curvatures
67
Q

Does true reciprocation increase or decrease the cutting efficiency?

A
  • Decreases cutting efficiency
68
Q

What does true reciprocation require an increase of?

A
  • Requires an increase of inward pressure
69
Q

What does true reciprocation have a limited capacity to do?

A
  • Has a limited capacity to auger debris out of a canal
70
Q

What are the guidelines for rotary instruments? (5)

A
  • Straight line access
  • Cross-sectional diameter (don’t want to put too bug an instrument in too quickly)
  • Root canal system anatomy
  • Speed and sequencing
  • Lubrication and a ‘light touch’
71
Q

How would you create a glide path? (6)

A
  • Confirm straight-line access
  • Explore anatomy
  • Always introduce files 10-25 to resistance only (coronal only)
  • Coronal flare
  • Size 10 with watch winging establish apex
  • Irrigate and repeat using sizes 15 (WW) and 20 (BF)
72
Q

If you get a file stuck in a canal what should you do?

A
  • Don’t panic if get the file stuck just try to use watch winding action to get it out
73
Q

When using reciproc what is the file controlled by?

A
  • Controlled by a computer motor
74
Q

Slides on the protocol for reciproc instruments in the lecture

A
  • Go look at the protocol
75
Q

Instrument separation can be due to Torsional stress or Flexural stress. What is Torsional stress and how does it cause instrument separation?

A
  • Extensive instrument surface encounters excessive friction on canal walls
  • Instrument tip is larger than canal section to be shaped (tip may lock, torque exceeds critical level)
76
Q

Instrument separation can be due to Torsional stress or Flexural stress. What is Flexural stress and how does it cause instrument separation?

A
  • Repeated cyclic metal fatigue (cannot be influenced by clinician)
77
Q

What is cyclic fatigue?

A
  • Freely rotating in a curvature
  • Generation of tension/compression cycles
  • Cyclic fatigue
  • Failure
78
Q

Want to use an aseptic technique when undergoing RCT. How can we do this?

A
  • By placing dental dam and by the use of hypochlorite

BDS3 Endodontics (8 decks)

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