Cleaning and Shaping of the Root Canal System

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Cleaning and Shaping of the Root Canal System

• Edit by Hou Tiezhou
• 02988088507

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Objectives of Canal Preparation

• Start with the end in mind

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Objectives of root canal preparation

• The root canal system must be
• Cleaned of its organic remnants
• Shaped to receive a three dimensional filling of
  the entire root canal space

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Objectives of root canal preparation

• The canal is
• Cleansed primarily by irrigation
• Shaped primarily by instrumentation

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Hence cleansing and shaping
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Cleansing of the root canal

• Objectives
• Removal of organic debris
• Elimination of bacteria

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Irrigation

• An ideal irrigant
• Is nontoxic
• Dissolves vital and necrotic tissue
• Is bactericidal
• Lubricates the canal
• Removes the smear layer

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Sodium hypochlorite

• Dissolves vital and necrotic tissue
• Is bactericidal
• Lubricates the canal

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Sodium Hypochlorite
Cannot be considered non-toxic!!!
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Prolube
EDTA and carbamide peroxide in a water soluble
base
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Prolube

• Facilitates placement of file
• Entraps debris
• Aids in removal of the smear layer

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EDTA

• Chelating agent
• Effectively removes smear layer

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Shaping of the root canal

• Canal shape produced by instrumentation
• Objective is a smooth tapered preparation

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Shaping of the root canal
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Instruments

• Instruments differ according to
• Metal
• Taper
• Tip design
• Cross sectional geometry
• Length of cutting blades
• Sizing

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Metals

• Nickel titanium Stainless steel
• Excellen flexibility Less flexible
• Conforms to canal Straightens and
• curvature transports canal
• Plastic deformation Permanent deformation

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Metals
Stainless steel files demonstrate permanent
deformation
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Metals
Nickel titanium files demonstrate plastic
deformation
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Taper

• Definition
• Increase in diameter per unit length

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What is Taper?
D16
D1
0.96 mm diameter increase
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What is taper?
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Taper

• Taper of instruments in U of M file kit
• Stainless steel files 0.02 taper
• OS variable tapers ranging from 0.05 to 0.08
• Series 29 rotary Profiles 0.06 taper
• NiTi hand files 0.04 taper

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Tip Design

• Non-cutting tip
• Bullet nose (60 degree) tip
• Smooth transition angle where tip meets flat
  radial lands

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Tip Design

• Designed to follow a pilot hole
• Guides instrument through canal during preparation

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Tip Design
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Cross-sectional geometry

• Three radial lands
• Each contains bidirectional cutting edges
• Keep instrument centered in the canal
• Cutting edges scrape dentin

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Cross sectional geometry
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Cross sectional geometry
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Cross sectional geometry

• Radial lands separated by three u-shaped flutes
• Provide space for accumulation of debris
• Moves debris out of canal

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Length of cutting blade

• Traditionally 16 mm
• Orifice shapers 10 mm

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Sizing of instruments

• ISO sizes
• Number refers to tip diameter in tenths of mm
• The tip diameter increases by 0.05 mm from sizes
  10 to 60, then by 0.10 mm

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Sizing of instruments

• increase in diameter from 10 to 15 file is
  50
• Difference between 55 and 60 is only 9

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Sizing of instruments

• Series 29
• Progressive 29 increase in tip diameter
• Instruments are better spaced
• More instruments in smaller sizes and fewer large
  instruments

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Crown Down Technique

• The coronal portion is prepared before the apical
  portion
• Follows medical principle of cleansing before
  probing a wound

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Crown Down Technique
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Crown Down Technique

• Eliminates constrictions in the coronal region
• Reduces effect of canal curvature
• Improves tactile awareness during apical
  preparation

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Crown Down Technique

• Allows more effective irrigation
• Removes majority of tissue and microbes before
  apical third is approached
• Reduces change in working length during apical
  preparation

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Crown Down Technique

• Coronal third Orifice shapers
• Middle third 0.06 taper rotary Profiles
• Apical third 0.04 taper hand Profiles

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Clinical Procedure

• Estimate working length
• Parallel radiograph
• Estimated working length is the distance from the
  reference point to the radiographic apex

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Parallel Radiograph
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Clinical Procedure

• Establish straight line access to apical third

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Clinical Procedure

• Explore canal patency
• Ensure that canal is negotiable to radiographic
  apex
• Small file 10 K-file
• May need to precurve these SS files

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Clinical Procedure

• Files used in a push/pull or quarter turn pull
  motion
• Never rotate these files through 360 degrees

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Clinical Procedure
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Clinical Procedure
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Clinical Procedure

• Estimate canal size
• Radiographic appearance
• Crown/root morphology
• Standardized tables

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Estimation of canal size
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Estimation of canal size
See Table in manual
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Clinical Procedure

• Actual WL determination
• Preparation should terminate at
• Apical constriction
• 1 mm short of radiographic apex

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Clinical Technique

• Actual WL determination
• Radiograph
• Apex locator

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Clinical Procedure
Actual Working Length Determination
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Clinical Procedure
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Clinical Procedure

• Apex Locator

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Clinical Procedure

• Crown down cleaning and shaping of canals

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Clinical Procedure

• This technique applies only to teeth ranging from
  18 23 mm in length
• Coronal third measurement is WL minus 8 mm
• Middle third measurement is WL minus 4 mm
• Apical third measurement is WL

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Preparation of the coronal third

• Coronal third measurement is working length minus
  8 mm
• Prepared using Profile orifice shapers

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Preparation of the coronal third

• Profile orifice shapers
• In sequence larger to smaller

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Preparation of coronal third

• Measure WL minus 8 mm on largest OS
• Lubricate the canal with Prolube

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Preparation of coronal third

• Rotate OS at 300 rpm
• Note Orifice shaper should be rotating at 300
  rpm before it is placed in the canal
• Advance the OS in 1 mm increments
• When resistance is encountered retract OS while
  still rotating
• Never force any instrument apically

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Preparation of the coronal third

• This OS will not extend to WL minus 8 mm
• Irrigate copiously

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Irrigation
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Preparation of coronal third

• Move to next smallest OS
• This will extend further than previous
  instrument
• Repeat the steps described for largest OS
• Move to next smallest OS
• Continue this sequence until working length minus
  8 mm is reached

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Preparation of coronal third

• Return to largest OS
• This will now extend further into the canal than
  it did previously
• Repeat this sequence until this (the largest) OS
  reaches WL minus 8 mm

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Preparation of the coronal third

• Never force any instrument apically
• Irrigate after every instrument
• Use copious amounts of Prolube

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Preparation of coronal third
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Preparation of middle third

• Middle third measurement is WL minus 4 mm
• Prepared using 0.06 taper Series 29 rotary
  Profiles in sequence larger to smaller

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Preparation of middle third
Prepared with 0.06 Series 29 NiTi rotary Profiles
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Preparation of middle third

• Measure working length minus 4 mm on the largest
  0.06 taper series 29 rotary file
• Set green rubber stop at that length
• Lubricate the canal with Prolube

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Preparation of middle third

• Rotate at 300 rpm
• File must be rotating at 300 rpm before it is
  placed in canal
• Advance file in 1 mm increments
• When resistance is encountered retract file while
  still rotating
• Copious irrigation with NaOCl

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Preparation of middle third
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Preparation of the apical third

• Prepare to actual working length
• Use 0.04 taper NiTi hand files in sequence
  smaller to larger

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Preparation of apical third
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Preparation of apical third

• Measure working length on 15 file
• Set rubber stop at that length
• Lubricate the canal with Prolube

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Preparation of apical third

• Advance size 15 file to working length
• Rotate file through 360 degrees
• Irrigate copiously with NaOCl after each file

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Preparation of the apical third

• Advance size 20 file to working length
• Continue through sequence, seating each file to
  working length

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Preparation of apical third

• The largest file that extends to working length
  is the Master Apical file (MAF)
• For large canals minimum MAF 40 - 50
• For small canals minimum MAF 35 - 40

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Master Apical File

• Take a radiograph with MAF in place. This
  confirms
• Length
• Placement

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Mission accomplished

• Smooth tapered preparation