Canal preparation 1 Flashcards
List two phases of canal preparation
- Debridement
2. Shaping
Debridement
Removal of all tissue and bacteria from root canal system
Shaping
Create shape to facilitate obturation
Describe warnings of debridement
- MUST confine instruments within root canal
- Avoid pushing debris out root apex
- Create shape within canal for chemical irrigant
Describe warnings of shaping canal
- Maintain special relationship of root canal within dentine
- Establish a “seat/stop” at apical termination
- Create tapering funnel
- Eliminate all surface irregularities along root canal walls
Endodontic failure is usually due to?
Colonizing of the filled canal system after treatment.
Primary goal of endodontic treatment?
Optimize root canal debridement and disinfection
Most favourable prognosis of end of canal instrumentation
Terminate at apical constriction
Least favourable prognosis of end of canal instrumentation
Working beyond apical constriction
List end of canal instrumentation aim and reference point
- End instrumentation at transition point between pulp and periodontal tissue (cemento-dentinal junction)
- Reference point: 0.5 - 1.5 mm inside apical foramen
- Aim to create smallest wound surface
In general, file is _____ to apex than it appears in the radiograph
Closer
When file is placed _____ in radiograph, it is actually ______ to apical foramen than it appears.
Short; closer
When file is placed __________ in radiograph, it is actually _______ past apical foramen than it appears.
Long; further
List landmarks of end of canal instrumentation
- Apical constriction
- Apical foramen
- Radiograph vertex
List recommended apical termination points
- 1.0 mm from radiographic vertex where no bone resorption occurs
- 1.5 mm from radiographic vertex where only bone resorption occurs
- 2.0 mm from radiographic vertex where bone and root resorption occurs
List goals of preparation
- Create continuously tapering funnel
- Minimize canal transportation
- Apical termination point of canal preparation should be kept as small as possible.
Minimizing canal transportation
Position of apical foramen and apical constriction should remain unchanged.
File
Tapered and pointed metal instrument with cutting edges used to enlarge the root canal by filing action
K-file
- File with square cross-section
- USed in all zones, but mostly in apical zone
- Use “Watch-winding” technique and “push-pull” action
H-file
- File with circular cross-section
- Used in coronal and middle zone only
- Use “pulling” action only
Flexofile
- File with triangular cross-section
- Flexible
- None-aggressive tip
Taper
The increase in file diameter with every 1 mm from the tip.
0.02 Taper means?
The filer gets 0.02 mm wider with every 1 mm from the tip
Circumferential (perimetre) filing
Repeat filing motion along entire inner perimeter of canal
Gates-Gliddens burs used when? Fracture rate?
Used only in Coronal zone.
- Easy to fracture in canal
Speed of Gates-Gliddens burs?
Use at low speed
Action of Gates-Gliddens burs?
- Passively insert into canal
- Withdraw from canal with light “paint-stroke” action along a wall
- Keep GG bur spinning until fully removed
Only use No. 2 GG bur when?
Only use No. 2 GG bur after #40 H-file has been used. Then sequentially use No. 3 GG bur and No. 4 GG bur (only in large canals)
List benefits of crown-down instrumentation
- Most important benefit -> provides a glide path
- Facilitates irrigant exchange
- Provides coronal escape-way for filing debris
- Reduces piston-pump effect
- Reduces apical extrusion of debris
- Improves instrument and irrigant access to apical canal
- Reduces potential for vapour lock
Lsit the steps of modified crown-down technique
- Access cavity preparation
- Determine working length (allows checking of canal patency and prep. configuration)
- Coronal one-third preparation
- Middle one-third preparation
- Apical one-third preparation
Describe file size choice
- 3 sizes bigger than the first file that binds
- Variation depends highly on curvature of root
List the preparation zones (only applies when Working length WL < 19 mm)
- Coronal one-third = WL - 8 mm
- Middle one-third = WL - 4 mm
- Apical one-third = WL
Phases of canal preparation: describe access cavity
- Access cavity should mirror the coronal pulp chamber
- Follows the long axis of tooth, not just crown long-axis
- Law of concentricity = Walls of pulp chamber are concentric to the external outline of tooth at level of CEJ
Define “Law of concentricity”
Walls of pulp chamber are concentric to the external outline of tooth at level of CEJ
Instrumentation for access cavity
- Pre-curve instrument: Match curvature of radiographic image
- ALWAYS have irrigant in the canal during instrumentation (need fluid for lubrication)
Define “Stem winding action”
CW/CCW twisting of file no more than 30 deg with positive apical pressure
- Pre-curved files can be rotated less or none
- Pre-curved files have increased risk of transporting canal
Phase of canal preparation: tactile negotiation
- Use Stem-winding action
- Stem-winding insertion to working length
- Do NOT screw instrument into canal
- Only use with K-Files
How to establish working legnth?
Use radiograph with file in canal
Describe circumferential filling
- Stem winding insertion to working length
- Cutting stroke on withdrawal of file
- No rotation of file in circumferential filing
After each incremental size increase in file, the ___________- is re-introduced for what?
Recapitulation file (i.e. original file used to measure working length) is re-introduced to working length to ensure canal remains patent and check for wall irregularities.
Recapitulation purposes?
- checks canal configuration
- Reduces vapour lock
- Facilitates irrigant transfer to apical zone of canal
- Prevents compaction of debris at bottom of canal
Apical patency
Technique where apical portion of canal is maintained free of debris by recapitulation with a small file through the apical foramen
Never re-use a _____ file and why?
Never reuse a loaded file therefore tooth debris file flutes.
- Clean file with gauze
- check the length of file
Equipment for canal preparation in coronal one-third?
Gates glidden burs or Hedstroem Files
Equipment for canal preparation in middle one-third?
Use Hedstroem Files and K Files
Equipment for canal preparation in apical one-third?
Use K-files only
