Biomechanical instrumentation lecture

1. Rotary Canal
Preparation
Dr. Ebtissam Al-Madi
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2. Outline
• Objectives of Cleaning & Shaping
– Biological
– Clinical
– Mechanical
• Instrumentation Techniques
– Stepback technique
– Crowndown technique
– Rotary Instrumentation
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3. • Biological Objectives
– Removal of all tissue, bacteria and bacterial
products and substrates from the root
canal system
• Mechanical
– Shaping of the root canal system to
facilitate placement of a root canal filling
• Clinical
– Eliminate apical periodontitis and return
tooth to normal function
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4. Cleaning
Endodontic
Triad
Shaping Filling
Shaping to facilitate cleaning and Filling
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5. Restoration
Obturation
Cleaning & Shaping
of the canal
Access
Preparation
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6. Stepback
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7. Stepback Technique
(1960’s)
• The most widely used preparation
technique
• Replaced Non-tapering Preparation
technique
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8. Stepback Technique
• Apical Preparation:
1. Establish access (straight
line)
2. Establish working length
3. File Instrument (watch-winding,
file, ream, etc)
4. Place next larger file,
instrument, and repeat till
you reach file 3-4 sizes
larger (MAF)
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9. Stepback Technique
• Step back:
1. Place next larger file to a
length 1 mm shorter of
working length, file, irrigate
and recapitulate
2. Repeat process with
successively larger files at 1
mm increments shorter than
preceding file.
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10. Stepback Technique
• Variations to the classic stepback
technique
– Initially enlarge coronal aspect with GG
burs
– Complete coronal preparation with GG
burs
– Use of small GG burs in mid-root level
– Use of Hedstrom files to flare the
preparation
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11. Stepback technique
• Advantages
– Minimize
procedural errors
(transportation,
ledging, apical
perforation)
• Disadvantages
– Significant apical
extrusion of debris
(post-operative
pain)
– Apical blockage
– Canal deviation
– Alteration of
working length
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12. Crown down
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13. Crowndown Technique
• More recent technique
• Produce similar result to step-back
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14. Crowndown technique
• Development of straight-line access
• Eliminate pulp chamber obstructions
and check patency
• GG enlargement with size 4-3-2,
irrigate
• Coronal to mid root enlargement with
instruments from large to small,
irrigate
• Establish working length, irrigate
• Introduce progressively smaller files
deeper into the canal until resistance
is encountered
• Establish apical preparation size
• Complete preparation Al-Madi, 491 Den 14

15. Crowndown technique
• Variations to the classic crowndown
technique
– Crown-down pressure-less technique
– Roane technique
– Double flare technique
– Modified double flare technique
– Rotary Instrumentation
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16. Crowndown technique
• Advantages
– Reduce apical
extrusion (reduce
pain)
– Elimination coronal
interferences
– Improved irrigation to
apical part of canal
– Facilitate working
length determination
• Disadvantages
– Early blockage of
canal
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17. Instruments
Hand
Instruments
Rotary
Instruments
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18. Hand instruments
• Been in use for over 100
years
• Still integral part of
cleaning & shaping
• Better tactile sensation
• ISO standardization
• Broaches, k-files, Flex-
R files, NiTi files, H-files
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19. Hand engine driven
• Properties of NiTi Alloy
– Superelasticity
– High resistance to cyclic fatigue
• Series 29
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20. Rotary Files
• Advantages
– Less transportation
and ledging
– Shape canal
uniformly
– Reduced operator
fatigue
– Improved
efficiency
• Disadvantages
– Cannot be used in
some cases
– Buildup of debris
– Cannot use beyond
apical foramen
– Fracture can occur
suddenly
– Initial cost
– Loss of tactile
sensation
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21. Rotary Instruments
• Lightspeed
• Profile
• Hero
• Quantec
• K3
• Flexmaster
• GT
• Protaper
• Sequence
• RaCe
• V-taper
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22. Design characteristics
• Non-cutting vs cutting
tip
• Tip size
• Taper
• Cross section
• Rake angle
• Helix angle
• Pitch
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23. • Tip could be
non-cutting,
cutting
Tip shape
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24. Tip Size
• Can be the same as ISO hand
tips sizes- color coded accordingly
• Can be half sizes (12.5, 17.5,
etc) as in Light Speed.
• Can skip sizes ( only 20,30, 40)
as in GT rotary
• Can be nonspecific sizes
(according to percentages ex.
18.5, 20..) as in ProTaper.
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25. Tip Taper
Taper ranges from 0.02 to 0.12
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26. • Constant taper- Variable tip
– Hand files (0.02)
– Profile 0.04
• Graduating taper- constant
tip size
– GT series
– Quantec
• Varying taper- different
tip sizes
– ProTaper
Tip Taper
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27. Cross section- Radial Lands
A radial land is a surface that projects axially
from the central axis, between flutes, as far as
the cutting edge
Non-cutting tips and
radial lands keeps a file
centered in the canal.
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28. Cross section- Radial Lands
Smaller radial land
equals decreased
strength for blade
support
Increased radial land
increases peripheral
strength behind the
cutting blade
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29. Rake Angle
The rake angle is the angle formed by the cutting
edge and a cross section taken perpendicular to the
long axis of the instrument
Rake angles affect the
cutting efficiency and
the aggressiveness of
the file
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30. Overly Positive Rake Angle
Positive Rake Angle
Neutral Rake Angle
Negative Rake Angle
Rake Angle
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31. • As the flute angle is
increased more debris
can be carried away
from canal.
Helical flute angles
The helical angle is the angle that the cutting edge
makes with the long axis of the file
• Constant helical flute
angles allow debris to
accumulate and are more
susceptible to the effect
of “screwing in” forces.
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32. Al-Madi, 491 Den 32

33. Al-Madi, 491 Den 33

34. Pitch
Pitch is the number of spirals or threads per
unit length.
Constant pitch and
constant helical angles
produce a “pulling” or
“sucking down into” the
canal.
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35. Al-Madi, 491 Den 35

36. Lightspeed
(Senia & Wildey 1990’s)
• Long, thin non-cutting
shaft
• U shape design
• Most flexible RI
• Low incidence of
transportation,
preparation errors,
and loss of working
length
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37. Profile
(Ben Johnson 1994)
• Increased taper
• Began as series 29
#0.02 taper, then
#0.04 and 0.06 tapers
• Profile (maillefer-
Europe) manufactured
tips similar to ISO
• Negative rake angle
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38. • Coronally pre-enlarge
• Use of Orifice shapers
• Alternative use of #.04
and #.06 tapers as well
as alternate tip sizes
• Same basic technique
for similarly designed
files
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39. Profile
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40. Profile
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41. K3
(McSpadden)
• Predecessors:
Quantec
• Unique cross
sectional design
with +ve rake
angle, 3 wide radial
lands, peripheral
blade relief
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42. ProTaper
(Cliff Ruddle, John West, Pierre Matchou)
• Only 6 instruments
• Modified k file
with no radial lands
• Varying taper that
increase coronally
in shaping files and
opposite in
finishing files
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43. ProTaper
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44. Hybrid technique
• Instruments can be used in a manner that
promotes their individual strengths and
avoids their weaknesses
• Hand instruments secure a patent glide
path
• Tapered rotary instruments efficiently
enlarge coronal canal areas
• Less tapered instruments allow additional
apical enlargement
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45. Newer Rotary
Instruments?
• Light Speed
• Hero 642
• GT files
• Quantec
• Flexmaster
• RaCe
• V-Taper
• Endo Sequence
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46. More information
• Pathways of the Pulp 9th e-edition
• Endodontics- Ingle 5th CD editon
• Advanced Endodontics- Rhodes
• Endodontics- Stock
• JOE
• IEJ
• Company brochures & Videos
• Internet
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47. How & Where to learn?
• Read & understand the brochure-
Don't be fooled!
• Read the literature in textbooks and
journals- Be an informed consumer.
• Try on extracted teeth till you
master the technique- try before you
buy.
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