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Pre-BDS3 Endodontics > Instrumentation of the root canal system > Flashcards

Instrumentation of the root canal system Flashcards

1
Q

What is the function of instrumentation

A

• It removes infected soft and hard tissue
• It gives disinfecting irrigants access to apical canal space
• It creates space for the delivery of medicaments and subsequent obturation
It retains the integrity of radicular structures

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2
Q

What is the function of the chemical preparation

A

Irrigate to kill microorganisms

Remove the smear layer

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3
Q

What is the function of the mechanical preparation

A

Prepare shape

Allows irrigant to flush out debris and microorganisms

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4
Q

What are the chemomechanical aims

A

Shape the canal
Allow delivery of sodium hypochlorite to working length
Create a shape that makes it easier to obturate

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5
Q

What are the challenges of root canal preparation

A

• The root canal system is very complex which can make it difficult to get the irrigant there
• The number, length, curvature and diameter of canals can vary considerably
Vertucci’s classification shows this

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6
Q

What is the estimated working length

A

○ Length at which instrumentation should be limited
Obtained by measuring pre-operative radiograph to determine distance between coronal ref point and radiographic apex, then subtracting 1mm

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7
Q

What is the corrected working length

A

○ Length at which instrumentation and subsequent obturation should be limited
Obtained by use of an electronic apex locator and/or working length radiograph

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8
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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9
Q

What are the types of instrument motions

A 
filing
reaming (warning)
watch-winding
balanced force motion 
envelope motion
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10
Q

What is watch winding

A

○ Back and forward oscillation of 30 to 60 degrees
○ Use light apical pressure
○ Effective with k files
Useful for passing small files through canals

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11
Q

What is balanced force motion

A

○ Insert file and engage into dentine with a quarter turn clockwise
○ With continued apical pressure turn the other way with a half turn anticlockwise
Do this a few times before removing file

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12
Q

What is the irrigation protocol

A
  • EDTA 17% for 1 minute to remove the smear layer
    • Sodium hypochlorite 3%, 30ml for 10 minutes
    • Do a slow injection and do not use the thumb
      Revise restorative synopsis and chemomechanical disinfection section
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13
Q

What are barbed broach instruments

A
  • Used for extirpating, NOT enlarging
    • Formed from a tapered round shaft by lifting up portions of metal of the shaft almost at a right angle to the shaft
    • Must not engage the canal walls
    • Extremely fragile instrument and will break easily if misused
    • The elevated barbs engage the pulp tissue and remove it from the canal
      The largest size broach which will fit freely in the canal is selected
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14
Q

Describe the iso color coding

A 
○ Pink = 06
		○ Pale pink = 08
		○ Purple = 10
		○ White = 15 
		○ Yellow = 20 
		○ Red = 25
		○ Blue = 30 
		○ Green = 35 
Black = 40
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15
Q

Describe the iso sized instruments

A

○ All have 16mm cutting flutes
○ Each file is named according to its diameter at the first rake angle
○ Taper is 0.32 over the 16mm or 0.02 per mm
Diameter at D2 = apical size + 0.32mm

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16
Q

Describe Hestrom files

A
  • Machined steel bank
    • Used in a filing motion, cuts on withdrawal
    • Good cutting efficiency but can cause iatrogenic damage, can easily separate as well
    • No longer used for canal preparation
      Useful for removing gutta percha or fractured instruments in cases of retreatment
17
Q

Describe Reamer files

A
  • Manufactured by twisting a tapered triangular shaft
    • Cutting edges nearly parallel to long axis
    • 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 may break
18
Q

Describe K files

A
  • Manufactured by twisting, or grinding a square tapered shaft
    • Cutting edges almost perpendicular to the long axis of the instrument
    • 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. This is repeated circumferentially until canal enlarged
      Do not use larger instruments too quickly
19
Q

Describe nickel-titanium alloy

A
  • It has a high resistance to fatigue

- It has super elasticity

20
Q

What is the advantage the super elasticity of NiTi

A

○ This means it can be strained more than other alloys before permanent deformation
○ It allows NiTi files to be placed in curved canals with less lateral force exerted
§ This means less transportation, zipping and ledging if used correctly
More centrally placed preparation in harmony with the original canal shape

21
Q

What are the components of an endo rotary instrument

A
  • Taper = diameter change along the working surface
    • Flute = groove to collect dentine and soft tissue
    • Leading/cutting edge = forms and deflects dentine chips
    • Land = surface extending between flutes
    • Relief = reduction in surface of land
      Helix angle = angle cutting axis forms with long axis file
22
Q

What is the advantage of NiTi vs SS

A
  • Increased flexibility in larger sizes and tapers
    • Increased cutting eficiency
    • If used appropriately good safety in use
      Can be more user friendly with less instruments in simple sequences
23
Q

What is the disadvantage of NiTi prep

A
  • Instrument fracture
    • Expense
    • Access can be difficult in posterior teeth if head of the handpiece is large or patient cannot open their mouth very wide
      Unsuitable for complex anatomy
24
Q

Describe S files

A 
S1 = coronal third
S2 = middle third
S3 = an axillary file sometimes used to open up an orifice, can be used instead of gates gliden
25
Q

Describe F files

A

The F files are coloured coded like ISO
F2 has the equivalent tip size of ISO25
Almost all files whether ISO or not ISO are generally all the same length so can be difficult so if the root is longer than these files then you cannot use the standard pro-taper universal

26
Q

What is true reciprocation

A
  • Is equal clockwise and anti-clockwise turning
    • Mimics manual movement
    • Reduces risks associated with continuously rotating a file through canal curvatures and the risk of this is ending up with a ledge or maybe even a perforation
    • Decreased cutting efficiency
    • Requires increased inward pressure
    • Limited capacity to auger debris out of a canal
27
Q

What does rotary endodontics do

A

○ Gates Glidden drill - can only be used for a sraight path
○ Development of NiTi
○ Greater flexibility (NiTi)
Greater taper (NiTi)

28
Q

What are guidelines of rotary instruments

A
  • Straight line access
    • Cross sectional diameter
    • Root canal system anatomy (curvature and diameter of the tooth)
    • Speed sequencing
      Lubrication and a ‘light touch’
29
Q

How do you create a glide path

A
  • Confirm straight line access
    • Explore anatomy
    • Always introduce files 10-25 to resistance only (coronal only)
    • Coronal flare
    • Size 10 with watch winding establish apex
    • Irrigate and repeat using sizes 15 WW and 20 (BF)
30
Q

What is reciprocation

A
  • The file in rotary handpiece is controlled by the computer
    ○ Angles of reciprocation
    ○ 150 degrees counterclockwise
    ○ 30 degrees clockwise
    • In a narrow canal a R25 should be used
    • For a wide/medium canal, if the hand instrument ISO 20 does not go passively to working length you use a R25
    • For a wide/medium canal, if the hand instrument ISO 20 goes passively to working length then you use a R40
    • For a wide or medium canal, the hand instrument ISO 30 goes passively to working length
31
Q

Describe the canal prep for reciprocation

A
  1. Estimate the working length from a pre-operative radiograph
  2. Place irrigant in the access cavity
  3. Introduce the RECIPROC blue instrument into the access cavity by pressing the motor foot pedal when the orifice is reached
  4. Move the instrument in a slow in-and-out pecking motion. The amplitude of the in-and-out movements should not exceed 3mm. Only very light pressure should be applied. The instruments will advance easily in the canal. One in-and-out movement is a peck
  5. Clean the debris rom the flutes in the Interim stand
  6. Irrigate the canal
    Make sure the canal is free to 1mm beyond the prepared canal section with an ISO size 10
32
Q

What is instrument separation due to

A
  • Torsional stress

- Flexural stress

33
Q

What is torsional stress

A

Extensive instrument surface encounters excessive friction on canal walls

Instrument tip is larger than canal section to be shaped

Tip may lock, torque

34
Q

What is flexural strength

A

○ Repeated cyclic metal fatigue

Cannot be influenced by clincician

35
Q

What is cyclic fatigue

A
  • Freely rotating in a curvature
    • Generation of tension/compression cycles
    • Cyclic fatigue
      Failure
36
Q

What is torsional fatigue

A

After reaching the elastic limit then you get into the plastic phase where the instrument deforms and if it keeps going and keeps turning each time it will be likely to fracture

37
Q

What is the summary

A
  • Use a method you are comfortable with and that you find predictable
    • Respect canal anatomy during shaping
    • Irrigation protocol is key
      Aseptic technique (dental dam and use of hypochlorite)

Pre-BDS3 Endodontics (13 decks)

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