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Cleaning & Shaping the Root Canal
System Using Rotary Instruments
Part I
Main Objectives of The lectures
!   Why we need NiTi rotary instruments over hand filing
!   What is the physical properties of NiTi vs SS files
!   What is the main concepts that we need to keep in
mind, before using any rotary system in the market
!   Why would I change from one system to another?
!   How are we advancing in that field?
!   What is the future of endodontics?
FRAMEWORK FOR ROOT
CANAL TREATMENT
—  Endodontic treatment has an important role in retaining natural
teeth in function and esthetics.
—  Biological Aims of Root Canal Treatment:
—  To cure or prevent periradicular periodontitis.
—  Prevent the sensation of pain
—  RCT Has Favorable Outcome:
—  Up to 95% for teeth with irreversible pulpitis.
—  Up to 85% with necrotic teeth.
Primary Objectives of Cleaning and Shaping the
Root Canal System
1. 
Remove infected soft and hard tissue during C&S
2. 
Use proper disinfecting irrigants with proper access of these
irrigants to the apical canal space.
3. 
Prepared canals should include the original canal shape
4. 
Prepared canals should maintain apical constriction
5. 
During preparation, create a space for the delivery of medicaments
and subsequent obturation material
6. 
Prepared canals should be tapered from crown to apex.
7. 
Retain the integrity of radicular structures
Different Approaches for C&S
!   Hand Instruments
!  
!  
K-files, H-Files, Reamers & Broaches etc.
Various hand movements
!   Engine-driven instruments
!  
!  
Current NiTi systems
Others: Historical systems
!   Other techniques
!  
!  
Laser
Non-instrumentation techniques (Regenerative Endodontics)
Nickel-Titanium Rotary Instruments
—  Since the early 1990s, several instrument systems
manufactured from nickel-titanium have been
introduced into endodontic practice. The specific
design characteristics vary, such as tip sizing, taper,
cross section, and helix angle.
—  Most of the rotary instruments are manufactured by a
grinding process, although some are produced by laser
etching.
—  Surface quality also is an important detail , because cracks that
arise from superficial defects play a role in instrument fracture.
—  Attempts have been made to improve surface quality by
electropolishing the surface and by coating it with titanium
nitride. The latter process also seems to have a beneficial effect
on cutting efficiency.
—  Two main properties of the NiTi alloy are of particular interest in
endodontics:
1. 
Super-elasticity (Shape memory)
2. 
High resistance to cyclic fatigue
—  NiTi rotary instruments have reduced the incidence of several clinical
problems, such as blocks, ledges, transportation, and perforation.
However, they also have a tendency to fracture more easily than hand
instruments.
Physical Properties and Phases
of NiTi Instruments
NiTi Rotary VS Hand
!   Working length was maintained significantly more in
NiTi than stainless steel (SS) files.
!   No edge in NiTi VS 30% in SS
!   Apical zipping occurs 31.7% less in NiTi than SS
!   Stripping was less in NiTi than SS
Himel et al., OOOE, 1995
•  Study on Undergrad in Lab Exam using
plastic curved canals teeth!
NiTi Rotary VS Hand
• 
NiTi has less canal transportation
• 
NiTi remove less dentin
• 
NiTi more efficient
• 
NiTi produce more centered canals
Gambill et al., JOE 1995
* Instrumentation of canals using CT
NiTi Rotary
Instruments
Group I
LightSpeed
Group II
ProFile
Group III
ProTaper
RaCe
NiTi Instruments
Concepts of Improving Rotary Systems
and Reasons of changing from one
system to another
!   Increase safety of using specific file
!   Better resistance to fracture
!   By changing file geometry
!   By changing file manufacturing methods and NiTi file
phase…
!   Decreasing operating time
!   By decreasing number of files used
!   By increasing cutting efficiency
!   File that gives desirable canal shaping and maintain the
original canal shape with less operating errors such as canals
transportation, zipping etc.
LightSpeed Instruments
!  
Has long, thin, noncutting shaft and
0.25 to 2 mm anterior cutting part.
!  
set consists of 25 instruments in sizes
#20 to #100, including half sizes .
!  
The recommended working speed is
1500 to 2000 rpm.
!  
More flexible than any other
instrument on the market because of
the relatively thin noncutting shaft.
!  
cyclic fatigue is lower than all other
instruments, allowing the use of higher
rpm speeds.
LightSpeed
—  Has a noncutting round tip
—  Requires a specific instrument
sequence.
—  Has a low incidence of canal
transportation and preparation
errors.
25 instruments to prepare a canal!!
ProFile
!   Introduced by Dr.
Ben Johnson in 1994.
!   Has an increased taper compared with
conventional hand instruments.
!   First was sold as a series of 29 hand
instruments with a constant proportion of
diameter increments (29%).
!   Soon became available in #.04 and #.06 taper.
ProFile
!   Cross sections of a ProFile is a U-shape with radial lands
!   Tip: noncutting.
!  
Together with a neutral or slightly negative rake angle, this
configuration ensures a reaming or scraping action on dentin
rather than cutting. Also, debris is transported coronally and is
effectively removed from the root canals.
!   The recommended rotational speed is 150 to 300 rpm
Rake angle
ProTaper Universal
—  Just 6 instruments, 3 shaping files and 3
finishing files.
—  Designed by Dr. Cliff Ruddle, Dr. John
West, and Dr. Pierre Machtou.
—  Cross section: a modified K-type file with
sharp cutting edges and no radial lands ;
this creates a stable core and sufficient
flexibility for the smaller files ( convex
triangle).
—  The three shaping files have tapers that increase
coronally, and the reverse pattern is seen in the
three finishing files.
—  Used at 300 rpm.
—  Better for narrow canal than wide.
ProTaper Universal
ProTaper NEXT vs ProTaper
Protaper Universal
http://www.youtube.com/watch?v=Er0EFN4wcUQ
ProTaper NEXT
http://www.youtube.com/watch?v=9PfKU1x2HBs
ProTaper NEXT File
Property
http://www.youtube.com/watch?v=nkooEoya32I
Cleaning & Shaping the Root Canal
System Using Rotary Instruments
Part II
Main Objectives of The lectures
!   Why we need NiTi rotary instruments over hand filing
!   What is the physical properties of NiTi vs SS files
!   What are the main concepts that we need to keep in
mind, before using any rotary system in the market
!   Why would I change from one system to another?
!   How are we advancing in that field?
!   What is the future of endodontics?
What are the main concepts that we need to
keep in mind, before using any rotary system
in the market
!   Read about the system you are about to use! Never start
working with a system that you don’t know its
properties and manufacture recommendation
!   Try using the file system in extracted teeth before using
it in patients
!   Before using the file system, look at the motor screen
and make sure you selected the right file settings
Key Points to look for in the
Endo Motor before you start
using it
•  The pre-set endo system at the motor!
•  Rpm (Rotation per minute)
•  Follow the file company
recommendation
• 
Torque setting
•  Auto-reverse mode
• 
Hand piece setting in the motor
•  1:8, 1:16 etc (Torque reduction HP).
Motors and Devices
—  Electric motors with gear reduction are more suitable for
rotary NiTi systems because they ensure a constant rpm level.
—  Torque-controlled motors increase operational safety.
—  In many cases the working torque is greater than the torque
required to fracture the instrument's tip. However, the tip will
not break if a passive glide path has been verified.
Motor Settings
http://www.youtube.com/watch?v=VmRMlUjqg2I
Why would I change from one system to another?
!   Evidence research show it is safer and efficient than
other systems in the market
!   Works good in your hand!!
RECIPROC ROTARY
SYSTEM
Balanced Force Technique
RECIPROC ROTARY
SYSTEM
Reciproc System
http://www.youtube.com/watch?v=v9NGXmJhIRM
Reciproc System
http://www.youtube.com/watch?v=v9NGXmJhIRM
How are we advancing in that field?
Evidence-Based-Dentistry
Fracture Mechanisms
—  Instruments used in rotary motion break in two distinct modes:
—  Torsional fracture occurs when an instrument tip is locked in
a canal while the shank continues to rotate. (Torsional fatigue)
—  Flexural fracture occurs when the cyclic load leads to metal
fatigue. Usually happen around a curve (Cyclic fatigue)
Torsional & Cyclic Fatigues
http://www.youtube.com/watch?v=X8JCl9maB40
!  Stainless steel develops fatal fatigue after only a few cycles,
NiTi instruments can withstand several hundred flexural
cycles before they fracture
—  Torque generated during canal preparation depends on the
contact area.
—  A crown-down approach is recommended to reduce torsional
loads by preventing a large portion of the tapered rotating
instrument from engaging root dentin (taper lock).
Crown-down technique
The principle of these techniques is that the coronal aspect of the root
canal is widened and cleaned before the apical part.
Advantages of these methods over the stepback are as follows
. It permits straighter access to the apical region
. It eliminates dentinal interferences found in the coronal two-thirds of the
canal.
. The bulk of the pulp tissue debris and microorganisms are removed
before apical instrumentation reduces the risk of extruding material
through the apical foramen .
. It allows better penetration of the irrigating solution to the entire root
canal system
Benefits of Using a Combination of
Instruments for Endodontic
!   Instruments can be used in a manner that
promotes their individual strengths and avoids
their weaknesses (most important).
!   Hand instruments secure a patent glide path.
!  
Tapered rotary instruments efficiently enlarge
coronal canal areas.
!   Less tapered instruments allow additional
apical preparation.
Concepts and Clinical Strategies to keep in
mind when using NiTi rotary instruments
1. 
Straight line access:
2. 
Create a glide path:
It is defined as a smooth radicular tunnel from the canal orifice of the canal to
the physiologic terminus of the root canal. A glide path is achieved when the
file forming it can enter from the orifice and follow the smooth canal walls
uninterrupted to the terminus. This confirms that there is a pathway for rotary
instruments to passively follow in the canal.
3.
Maintain Patency.
Patency file is a small K-file (usually a size #10 or #15) that is passively
extended just through the apical foramen This step is believed to remove
accumulated debris and help maintain working length
Concepts and Clinical Strategies to keep in
mind when using NiTi rotary instruments
4. 
Recapitulation: Taking small file to the correct WL to
loosen debris apically.
5. 
Never force the file in the canal
6. 
Don’t overuse the file:
7. 
Always test the file system in vito then in your patient.
8. 
Avoid cutting with the whole file length!
9. 
Never start and stop the file in the canal
10.  Length control is important
Concepts and Clinical Strategies to keep in
mind when using NiTi rotary instruments
11. Apical diameters
How big the apical stop should be?
!   Difficult to assess clinically
!   This is a crucial point because the initial canal size determines
the desired final apical diameter.
Factors Governing the Potential for NickelTitanium Rotary Instrument Fractures
!  
Clinician’s handling (most important)
!  
!  
!  
!  
Knowledge & clinical experience
Handling the motor settings
Knowing the advantages & limitations of file system you are
using
Root canal anatomy
!  
!  
!  
Study the preoperative radiograph before you start
Take different angles
Not necessary every canal will be treated the same way and using
the same rotary system
!  
Combination of torsional load, bending, and axial fatigue
(complex cases)
!  
Manufacturing process and quality
Pre assessment
Straight access cavity
Five commonly encountered canal paths, canals that:
Ruddle C: Cleaning and shaping the root canal system. , St Louis, 2002, Mosby.
Irrigation with agitation
!  
While we aim to decrease of files per canal, then we need to think
about irrigation!
!  
Irrigations need to reach to all RC system including isthmuses and
lateral canals to insure most bacteria are eliminated before
obturation.
!  
Irrigation with agitation
!  
!  
!  
Endo-Activator
Ultrasonic
Using irrigation syringe with in & out pumping motion
EndoActivator
http://www.youtube.com/watch?v=xE8p0mJGtxE
What is the future of endodontics?
!   Regenerative Endodntics; Revascularization;
Revitalization..
!   We can only achieve this by having the right amount/
quality of all three!!
Stem
Cells
Scaffold
Growth
Factors
Common Mistakes Students Always Do!
!  
They never know or read about the system there want to use in clinic
!  
They never check the motor setting
!  
If they are using Reciproc, they enlarge all canals using size R25! Keep in
mind not all canals are the same size “apically!”
!  
Enlarging R25 to palatal and distal canals without apical enlargement!
!  
If they did apical enlargement to distal canals manually to
size 45 they still use matching file R25 gutta percha to
obturate the canal!
o 
They prepare central incisors with R25 or R40 then obtrurate the canal
with match cone GP.. What about the coronal part of the canal that you are
suppose to brush it? You will end up with a space!
o 
They rarely measure the master cone before obturation, to see if it reached
the WL!
Take Home Massage
!  
I need all of you to remember!
!  
What makes you a great endodontist or differentiate you from others
NOT WHICH FILE SYSTEM YOU USE!!
!  
!  
!  
!  
!  
!  
!  
!  
!  
If you understand the biology & scientific evidence behind what you do!
If you are always a good listener!
If you always diagnose it right!
If you always can manage to do it with NO PAIN!
If you explain to the patient what should he/she expect during and after the
treatment, and make sure you will always be on control!
If you know how to manage other people mistakes, and importantly, yours if
it happened!
If you can treat complicated cases as treating easy ones
If you can deal with post-endodontic complications
If you do it fast, but importantly, with excellent quality and high success rates!
References
!   Cohen’s pathway of the pulp chapter book (Ch. 9)
!   You should see all videos presented in the lectures.
Links are below each video.
!   Lecture notes.
!   Supporting Articles
Thank you