cleaning and shaping of root canal therapy

1. INTRODUCTION
2. OBJECTIVES
-MECHANICAL
-BIOLOGICAL
-CLINICAL
3.EVIDENCE AND STRATEGIES
4. INSTRUMENTS USED IN ROOT PREPARATION
5. INSTRUMENT MOVEMENTS FOR SHAPING
1. WATCH WINDING
2. REAMING
3. FILING
4. ROTARY
6. POTENTIAL SHAPES
7. REQUIREMENTS FOR AN IDEAL ROOT PREPARATION

8. PRECURVATURE OF FILES
9. RECAPITUALTION
10. PREPARATION TECHNIQUES
-STANDARDIZED
-STEP BACK
-ANTICURVATURE
-STEP DOWN
-BALANCED FORCE
-CROWN DOWN PRESSURELESS
-DOUBLE FLARE
-DEDUES
11. MANAGEMENT OF CURVED CANALS
12. NON-TRADITIONAL METHODS
1. -LASER
2. -NON INSTRUMENTATION
3. SONIC & ULTRASONIC INSTRUMENTATION
13. PROCEDURAL ERRORS
14. CONCLUSION
15. REFERNCES

Introduction
• Schilder introduced these terms to the endodontic
vocabulary in 1974
• Universally used to indicate the principal goals of
canal preparation..

CLEANING
The purpose of cleaning is to remove all intracanal material,
whether of pulpal origin, vital or necrotic, of microorganisms, from
the root canal system

SHAPING
The instruments give the canal such a shape that the space
obtained within may then be easily filled three-dimensionally.
The shape to be given to the root canal depends on the
obturation technique.
shaping facilitates cleaning!
shaping facilitates obturation!!

Objectives in Cleaning &
Shaping

• Remove infected soft and hard tissue
• Give disinfecting irrigants access to the apical canal
space
• Create space for the delivery of medicaments and
subsequent obturation.
• Retain the integrity of radicular structures

Schilderhas listed the “mechanical” and
“biological” objectives of shaping of the root canal to
receive the warm gutta-percha obturation

Mechanical objectives
1. A continuously tapering preparation
2. Cross-sectional diameter diminish in a corono-
apical Direction
3. The conicity must exist in multiple planes and
must give a sense of “flow.”
4. The apical foramen should not be transported
but should be preserved in its original position
and shape.
5. The apical foramen must be kept as small as
practical.

Biologic Objectives
Limit the instrumentation to within the root canal.
Don’t force necrotic material beyond the foramen.
Scrupulously remove all tissue debris + bacterial
byproducts.
Complete the cleaning and shaping of individual canals in a
single visit.
During the enlargement of the canals, create a space sufficient to
contain any exudate that may form.

Clinical Objectives
• Evaluate the tooth- favourable prognosis
• Straight line access – remove overlying dentin and flare and
smooth the internal walls
• Instruments & irrigants must go deeper into the canal
• After Obturation- complete seal (pulp chamber and access
cavity)- prevent microleakage
• Permanent restoration- function, form, esthetics
• Regular Recall Review

Evidence and Strategiesfor shaping the root canal system

• The minimum size to which a root canal should be enlarged
cannot be standardised and varies from case to case.
• A study shows molar tooth canals should be enlarged upto #40
for effective cleaning.
• Another rstudy shows canals shaped with 6% taper instrumemt
upto #30 have cleaner canals without smear layer or debris.

Instrument Movements While
Shaping

WATCH-WINDING
• The least aggressive
• Because the instrument tip is not forced into apical region with
each motion.
• Most desirable in the early phases of
root canal instrumentation.
• Recommended by most clinicians.

• Rotations of a quarter turn using small (size #08 or #10) K-files
to reach WL or to explore the canal prior to coronal flaring.
• copious irrigation and constant cleansing of the instrument
necessary.
• The back and forth oscillation of the endodontic instrument
RIGHT AND LEFT as it is advanced into the canal.
• Angle of rotation- 30-60 degrees
• Efficient with k-type file or reamer.

REAMING
• Reamers are instruments designed to enlarge or taper pre-
existing spaces.
• The cut is made during retraction.
• penetration, rotation, and
retraction.

• When WL is reached, the next size instrument is used, and so on.
• produces a round, tapered preparation
• used only in perfectly straight canals
(rotated one-half turn before retracting.)
• slightly curved canal, a reamer should be rotated only one-
quarter turn
• reaming alone is contraindicated-used
alternately in conjunction with filing

FILING
• A purposeful motion that cleans and enlarges the endodontic
cavity space harmlessly,
• while maintaining the natural pathway of the space.
• PUSH-PULL Action
• The primary cutting action is on withdrawal.
• It will cut in the push motion as well
• Must try to engage all the walls of the canal circumferentially.
• The tooth structure should be removed preferentially from the
outer wall of the curve of the root canal system to gain the
straightest possible access to the foramen.

instrument is
placed into the
canal at the
desired length
pressure is
exerted against
the canal wall
this pressure is
maintained,
instrument is
withdrawn
without turning
The file need
not contact all
walls
simultaneously.
FILING
 Hedstro¨m files
 K files
 NiTi rotary instruments,
 ProSystem GT (Dentsply Tulsa Dental,
Tulsa, OK)
 ProTaper (Dentsply Maillefer),

WATCH WINDING + PULL
• for H-Files
• As it cuts only in Pull Motion.
Instrument
moved
apically
Rotating
right or left
in an arc
Pull it out If
resistance
is felt

ROTARY MOVEMENTS
• Continuous rotary movement was thought undesirable for shaping
curved canals due to the danger of instrument fractures.
• Strip perforations occurred with indiscriminate use of GG or Peeso
drills.
• NiTi alloy-invented.
• Rotary/ Endodontics movement with NiTi instruments with
noncutting tips creates shapes with little or no incidence of
preparation errors.

• Several systems to prepare canal with hand or engine
driven instruments were described.
• There are two principally different approaches:
-The ‘‘apex first’’
o WL is reached and the apical area is prepared
first with increasingly larger instrument sizes.
-The ‘‘Coronal first’’ techniques.
o uses descending instrument sizes to prepare
coronal canal areas first and apical ones last.

POTENTIAL SHAPES
of the root canal system

• Variations in apical shape have received special
attention and varying recommendations.
• These configurations were named as ‘‘apical stop,’’
‘‘apical box,’’ ‘‘apical capture or control zone.’’
• The intent of all the described techniques is two-
fold:
a) allow irrigants access to the apical root canal
system
b) prevent filling material from being extruded into
the periapical space.

• Kast’akova et al. demonstrated
that an apical stop, prepared to follow the
recommendation to prepare three sizes larger
than the first file to bind at WL, did not prevent
sealer or gutta-percha extrusion.
• Finally, they found
A Tapered apical preparation would reduce the
incidence of over preparation that may occur following
a length determination error and an apical stop
preparation.

• The following are a list of requirements for an ideal root
preparation:
1. Complete access.
The preparation should allow unobstructed visibility of the
pulp chamber and convenient access to the root canal system at
every level.
2. A continuously tapering shape.
This aids in the removal of debris, facilitates finishing and
irrigation and prevents the displacement of filling material or
provides retention for that material.

3. Maintenance of the original anatomy.
The outline of the cavity preparation is dictated by the
anatomical outline of each tooth. Thus, the orifice, the pathway of
the canal and the apical foramen remain in their original spatial
location during and after preparation.
4. Conservation of tooth structure.
The conservation of tooth structure provides resistance to
fracture and decreases the incidence of perforation.

Furthermore, if the integrity of the apex is maintained
and the apical foramen is kept small, transportation of
the apex is eliminated and the opportunity to seal the
apex is enhanced.

“A straight k file is a dumb instrument”

• To maintain the curvature of the root canal system and to
capture the tortuosity of that anatomy in all dimensions, the
clinician must adapt instruments that not only duplicate the
original anatomy of the system but also address the directional
shifts that occur as the instrument is manipulated during use.
• As a general rule , all hand instruments should be precurved
before placing in the canal
• Exception of instruments is in balanced force technique.

• Root canal instruments are manufactured from straight metal
blanks
• And are resistant to bending.
• The concept of elastic memory can only be overcome by over
bending the instrument while it is being prepared for use.

• The degree and extent of over bending that is applied depends
on the curvature of the canal and the flexibility of that
instrument.
• When the precurved instrument is placed in a canal and worked,
the shape of that instrument is altered very quickly.
• Thus, the instrument must be removed from the canal
repeatedly and recurved.

• As the preparation of the primary canal continues, the degree of
curvature of the canal and the tortuosity of the pathway is
reduced.
• Thus, the length of the canal as well as the length of the
instrument must also be reduced.

• The ideal instrument for precurving endodontic
instruments in a predictable and repeatable way
without minimally changing the blades is
represented by the Endobender

RUBBER STOPS
• Are used to regulate the working length.
• The stops must be easily applied and easily movable
• The stop must be seated 90° to the long axis of the instrument;
• it should not be tilted.
If the stop is positioned obliquely, the instrument’s
working length can vary by as much as 2 mm.
• the stops must be directional.

• Term- Schilder
• The sequential re-entry or recapture of that portion of the
root canal system that has been previously enlarged during
preparation.
• regardless of the methodology used.
• sequence and frequency -is dependent of the complexity
of the anatomy of each root canal system.
• Using previously used smaller instruments than the
currently employed, frees the root canal off the
accumulating dentinal shavings.
• Insures the continuously tapering shape.

History
• Ingle : 1961 Standardized instrumentation
• Clem, Weine Schilder : 1969–1974 Step-back, serial
preparation
• Abou-Rass : 1980 Anticurvature filing
• Marshall : 1980 Crown-down pressureless
• Goerig : 1982 Step-down
• Fava : 1983/1992 Double flare, with
modifications
• Roane : 1985 Balanced force
• Torabinejad : 1994 Passive step back
• Siqueira : 2002 Alternate rotary motion

STANDARDIZED
• ‘‘Single-length technique,’’
• Negotiation of fine canals is initiated with fine files.
• These are advanced to the WL
worked until a next larger instrument may be used.
the final shape is predicted by the last-used instrument
(MAF)
• A single matching gutta-percha point may then be used for
root canal filling

• This concept suffers from two factors of variation:
-first,
Canals (those with curvatures), shaped with the
standardized technique, end up wider than the instrument size.
-second,
Production quality is insufficient, both for instruments and
for gutta-percha cones, leading to size variations.
• ProTaper (Dentsply Maillefer)
• MTwo(Sweden and Martina, Padova, Italy)
• NiTi rotary instruments.

STEP-BACK
• “telescopic/ Flare / serial RC preparation technique.”
• Stepwise reduction of WL for larger files, typically in 1- or 0.5-
mm steps, resulting in flared shapes with 0.05 and 0.10 taper,
respectively
• Schilder suggested a ‘‘serial preparation’’ that included enlarging
to a file size #30 or #35 and then serially reducing WL for the
following instruments.

• Coffae and Brilliant,
• described a serial procedure that entailed the use of a
#35 file to WL,
• stepwise reduction of WL for subsequent files up to
size #60,
• and then the use of GG drills Nos. 2 and 3 into the
canal
-----superior debridement with serial
preparation compared to standardized shapes

• Mullaney -the step-back technique as particularly effective
in fine canals
• He divided the step-back preparation into two phases.
• Phase I is the apical preparation starting at the apical
constriction.
• Phase II is the preparation of the remainder of the canal,
gradually stepping back while increasing the instrument size.
• The completion of the preparation is the Refining Phase IIa
and IIb to produce the continuing taper from the apex to the
cervical
•

To start Phase I instrumentation,
the canal should have been explored with a fine
instrument
the WL established.
Lubricate
MAF size has to be used to full WL
Repeat till MAF as #30 k-file as minimum.
Recapitulate

Phase 2 :
Place next file in the series
Place the rubber stopper at 1mm short of the WL
Insert with watch winding motion
Do circumferential filing
Remove it
Irrigate
Recapitulate with #10 file

• Repeat this with successively larger files
@ 1mm short from every last used file
• Mid canal and coronal part is prepared with larger number

• It has been recommended to end this step-back phase at size
#60 or
• when the instrument has reached the wider straight portion of
the root canal.
• The most coronal canal portion may then be carefully flared
with GG drills or Hedstro¨m files.
• The refining Phase is a return to the MAF,with PUSH PULL
STROKE smoothing all around the walls to perfect the taper
from the apical constriction to the cervical canal orifice,.

Advantages
1. Better tactile awareness
2. Less chances of periapical trauma
3. The development of apical stop prevents overfilling of
root canal
4. Greater condensation pressure can be exerted which
often fills lateral
canals with the sealer
Disadvantages
• Apical extrusion of the debris through the apex
• Working length likely to change as canal curvatures
are eliminated

• Torabinejad. (PASSIVE STEP BACK)
• Improves the tactile feedback from the apical region as well
as better access for irrigants.
Inert progressively larger hand files
As deep as they passively go
Gg drill or peso reamer for coronal
enlargement
Ultrasonically activated #15k file used to
blend canal irregularities
Ultrasonic or sonic activation of irrigants for
1-2min & turned over every 30seconds

ANTICURVATURE FILING
• Abou Rass, Glick, and Frank
• To prevent excessive removal of dentin from thinner root
sections in curved canals.
• The furcation side (danger zone) of cross sections of mesial
roots of mandibular molars has less dentin thickness than the
mesial side (safety zone)
• use of precurved hand files
• that were purposefully manipulated to file the canal away
from the danger zone

• The bulky or “safety zone”, is far from the
bifurcation, where the dentin is thicker and which
corresponds to the mesial wall of the mesial roots
of the lower molars and of the mesiobuccal roots
of the upper molars;
• and a thinner area, or “danger zone”, in which the
dentin is thinner and the canal is closer to the
periodontium.
• This danger zone comprises the distal wall of the
mesial roots of the lower molars and of the
mesiobuccal roots of the upper molars.

• It also incorporates coronal flaring with rotary instruments
after the use of hand instruments,
• but it is stated that such instruments should not be introduced
more than 3 mm into root canals.
• A final use of a manual instrument to blend the apical and
coronal segments
• Kessler et al. as well as Lim and Stock demonstrated that
‘‘anticurvature’’ filing in fact helped to reduce the risk of
perforation.

STEP-DOWN
• Goerig et al.,
• shaping the coronal aspect of a root canal first before apical
instrumentation commenced.
• The Primary purpose of this technique is to minimize or
eliminate the amount of necrotic debris that could be
extruded through the apical foramen during instrumentation
• The technique permits straighter access to the apical region.
• It eliminates coronal interferences,
• It removes the bulk of tissue and microorganisms before
apical shaping
• Allows deeper penetration of irrigants,
• WL is less likely to change.

• Major advantages of stepdown preparation is
 the freedom from the constraint of the apical enlarging
instruments.
first flaring the coronal two-thirds of the canal.
final apical instruments are unimpeded through most of their
length.
This increased access allows greater control and less chance
of zipping near the apical constriction
Provides a coronal escape way that reduces the piston in a
cylinder effect’’ responsible for debris extrusion from the
apex.

• preparation of coronal root canal two thirds using Hedstro¨m
files of size #15, #20, and #25 to 16 to 18 mm or where they
bind
• GG drills Nos. 2 and 3, and then potentially No. 4, are used
sequentially shorter
• Thus Flaring the coronal segment
• apical instrumentation is initiated
• consists of negotiating the remainder of the canal with a small
K-file,
• shaping an apical ‘‘seat

stepwise decrease the WL of incrementally larger files
recapitulation with a #25 K-file to WL
in the presence of NaOCl
starting with a size #50 K-file
work down the canal, until the apical constriction (or WL) is reached.
When resistance is met for further penetration, the next smallest size
is used.
To properly enlarge the apical third and to round out ovoid shape and
lateral canal orifices, a reverse order of instruments may be used
starting with a size #20 (for example) and enlarging this region to a
size #40 or #50 (for example)

BALANCED FORCE
• Roane et al 1985
• Flex-R File
• preparation is completed in a step-down approach
• The coronal and mid-thirds of a canal are flared with GG drills
–ascending order
• shaping with hand instrument is carried out in the apical areas
positioning and preloading an instrument through a clockwise
rotation and then shaping the canal with a counterclockwise
rotation.’ -Ingle

• After mechanical shaping with GG drills, Balanced Force hand
instrumentation begins
triad of movements:
PLacing
Cutting
Removing
instruments using
only rotary motions

the third movement pulls the instrument gently out of the canal
with clockwise rotation
the first two movements repeatedly, progressing more apically.
rotate counter clockwise for a half- to three-quarter turn
file may be advanced into the canal with a one-quarter
clockwise rotation.

• The amount of apical pressure must be adjusted to match the file
size (i.e., very light for fine instruments to fairly heavy for large
instruments).
• Counterclockwise motion should be 120 degree or greater.
• A greater degree of rotation is preferred and will more completely
shape the canal
• clockwise rotation allows the instrument to engage dentin, and
this motion should not exceed 90.
• If excess clockwise rotation is used, the instrument tip can become
locked into place and the file may unwind.

If continued, when twisted counterclockwise, the file may fail
unexpectedly.
The process is repeated (clockwise insertion and
counterclockwise cutting) as the instrument is advanced
toward the apex in shallow steps.
 After the working depth is obtained, the instrument is freed
by one or more counterclockwise rotations made, while the
depth is held constant.
The file is then removed from the canal by a slow clockwise
rotation that loads debris into the flutes and elevates it away
from the apical foramen.284
A more or less flared final shape may be obtained by stepping
back in 0.5 or 1 mm increments.

• Optimal for kflex design
• They eliminates the transition angle of the k file
• Thus prevents canal transportations
• Files with a parabolic or round tip may be useful
The method should not be employed in the extreme apical extent of
the endodontic cavity preparation to avoid transportation of the apex.
• in vitro reports indicate that shapes created with the Balanced
Force technique are of excellent quality328
• Are comparable to those with NiTi rotary instruments.
• Less Extrusion of material compared with other techniques.

CROWN-DOWN PRESSURELESS
• John Pappin & Marshall
a provisional
working length
(WL) with a size #35
hand file
Coronal
preenlargement
Gates Glidden burs
larger burs to
smaller burs
hand files starting
with a large file

Definitive WL
determined as soon as
the progress is made
beyond the
provisional WL
Apical enlargement
enlarge the apical area
to three sizes larger
than the first file that
bound at WL
recapitualtion
(e.g., size #60)
and progressing
apically with
smaller sizes
homogenous
shape that may
be similar to the
one created with
the step-back

DOUBLE FLARE
• Fava
• exploratory action with a small file.
• Indicated for straight canals.
• crown-down portion with K-files of descending sizes.
• an apical enlargement to size #40 or similar
• recommended stepping back in 1 mm increments with
ascending files sizes
• and frequent recapitulations with the MAF
• Avoid significant WALL CONTACT DURING THE
crowndown phase

Hybrid technique
• GOENIG & BAUCHMAN
• Combination of step down and step back
• Early radicular access by GG drill no.1-6
• Hand instruments secure the patenct glide path.
• Apical region enlarged with step back technique.
1.Step down
2.Step back
3. Blending of both

De-dues
• late Quintiliano DeDeus, a reknowned endodontist from
Brazil.
• a description of the method has yet to be published.
• extremely safe and effective method
• however, painstaking
• the shapes can be narrower than in other techniques,
• but follows the path of the root canal well.

A precurved file used
in a rocking or
oscillatory manner.
moved apically
through the length of
the canal
Stop when reistance
is felt
turn slightly counter-
clockwise to retrieve
or unlock the
instrument
Turned lightly in a
clockwise direction to
capture debris
progressively use
larger and larger files
deper and deeper
repeat sequence
until desired
diameter and shape
is achieved
The method employs the use of :

UNIVERSAL PROTAPER HAND
FILE
(MODIFIED BALANCED FORCE)
• PROTAPER ROTARY :- Prof.Pierre Machtou,
DR.Clifford Ruddle, Prof.John West with the
Dentsply/Maillefer.
• HAND PROTAPER was then introduced.
• 2006 – UNIVERSAL PROTAPER

ENGINE DRIVEN INSTRUMENTS
FOR CANAL PREPARATION
• SAF SELF ADJUSTING FILE TECHNIQUE
• Hollow file
• Adapts itself to the original canal anatomy and shape.
• Compressible & Thin walled pointed cylinder design.
• It has continuous irrigation by a special irrigation apparatus.
(VATEA Irrigation device)
• Single use design.

• Insert into the canal while vibrating
• Pushed till the measured WL
• Operate in two cycles of 2minutes each.
• In and out manual motion
• Continuous fresh irrigation
• File removed and infected after each cycle.

PROTAPER NEXT ROTARY
TECHNIQUE
• M wire technology
• Progressive taper on a single file
• Cross section- rectangular.
• Offset design (i.e. the center of mass/centre of
rotation, or both are offset)
• This produce a mechanical wave of motion
• That travels along the active file length.
• 300rpm 2*5.2Ncm torque.

• SX file-
preflare the orifice
Eliminate dentine triangles
Use in Brushing motion
 creates lateral space
 improves contact between the file and
dentine.
• Glide path (#15 file or path files)
• Insert X1 file
Irrigate
Recapitulate

• Progress till the WL
• Use X2
• Brush against dentinal wall till WL
• Re-irrigate
• If #30 file snug at length, the shape is finished.
• Use X4 & X5 to prepare and finish larger canals

Hand protapers
Light clockwise rotation
Engage dentin until snug
Counter clockwise (1/4 turn )
Disengages the file + cuts dentin
Rotate clockwise (3/4)
Simultaneously withdraw file
Repeat until desired lenth

BLENDING
• the clinician’s final attempt to blend or marry the various
aspects of the enlargement procedure to create the ideal
shape of an endodontic cavity preparation.
• usually files used in a rasping and push-pull motion
• instruments are precurved
• applied to the outer wall of each arch to insure a smooth
transition from one plane of the endodontic cavity space to
the next.
• The finished preparation should then provide
Unimpeded exit and entry of instruments and materials,
with effortless access of the apex.

Signature
• This defines the artistic result that the clinician renders on
completion of the endodontic cavity preparation.
• It bears the attributes of a fine sculpture or carving and is
unique,
• i.e., each clinician will incorporate small nuances to the
preparation that are solely attributable to his artistic ability
and workmanship.
• Talented clinicians can often identify their work, or so called
signature, merely by glancing at a radiograph shown to them
at random

Advantages of stepback technique
1. Better tactile awareness
2. Less chances of periapical trauma
3. The development of apical stop prevents overfilling of
root canal
4. Greater condensation pressure can be exerted which
often fills lateral
canals with the sealer
Disadvantages
• Apical extrusion of the debris through the apex
• Working length likely to change as canal curvatures
are eliminated

MANAGEMENT OF CURVED
CANALS
 the curves of the apical third must be respected,
 the curves of the middle third are blunted and smoothed ,
 the curves of the coronal third must be eliminated
• before commencing normal cleaning and shaping.

CURVES OF THE APICAL
THIRD
• Straightening these curves would mean displacing the apical
foramen from its original position
• Always start with small, precurved instruments, such as a # 08 or
10 K-type file
• Precurvature should reflect the degree of apical curvature
• Start only after confirming the file is at the radiographic apex.
• Bath in sodium hypochlorite
• Make small excursions of fractions of a millimeter.
• Always recurve reintroduce a smaller file- maintain apical
patency and curvature
• No Reamers – as it will cause HOURGLASS shape

• If one creates a ledge,
 -start over again with the first small file with very short
accentuated apicall precurvature ( #08 #10)
 -Insert in the canal with precurvature aligning the apical
curvature.
 -use step back,watch winding or balance force to eliminate
the ledge.

• An easier and faster way to get the same result -hand GT
Files.
• Overbend to 180 degree by an endobender
• The GT File is rotated counter-clockwise (the direction of
the flute twists) until it snugs tightly
• With apical pressure turn it 360 degree clockwise
• Initially file progressively tightens till about 180 degree-
• Then it releases and easily turns
• Now rotate counterclockwise again into the canal
• Again reverse it clockwise to 360 degree with pressure
• Do 3 cycles before removing the file.

CURVES OF THE MIDDLE
THIRD
• Partially straighten this
• upper and lower second premolars-common –first curve
mesialy and second distally
• Double curve the files
• Curves Facing the same direction as the canal
• Withdraw –irrigate-recurve-reintroduce-reorient the file
periodically.

• The nickel titanium instruments, remain centered within the
root canal removing dentin on 360°
• they don’t straighten the curvatures but they maintain them

CURVES OF THE CORONAL
THIRD
• mesial roots of lower molars
• Mesiobuccal roots of upper molars
• Before working,
 -straighten these curves
 - perform an early enlargement of the coronal middle thirds
This helps in,
- Better direct access
- Eliminates the restrictive dentine-so more tactile sense
- Reduces bifurcation stripping and other mishaps
- Better irrigant penetration

Guidelines for
negotiating calcified
canals

• Copious irrigation with 2.5 to 5.25% NaOCl.
• Dissolve organic debris
• Lubricates the canal
• Suspends the chips and pieces in solution
• Always advance the instrument slowly.
• Always clean the instruments on withdrawal and inspect
before reinserting.
• When a fine instrument reach the approximate canal length
take a radiograph. Do not remove the instrument.
• Use chelating agents
• Flare the orifice and coronal enlargement improves tactility
• Do access opening without anesthesia.
• Ask patient to indicate if he feels sharp sensation .

• Insert small number file
• if file is inserted only a mm or two into pulp, the reaction
is sharp
• If it is in PDL, reaction will be less sharp.
• Do not remove large amount of dentin to find the canal.
• Tooth strength and pulp floor landmarks will be
compromised.

MANAGEMENT OF C-
SHAPED CANALS

• Common In mandibular second molar + maxillary first molar
(usualy when roots are fused)
• Maxillary molar- MB +palatal canals
• Mandibular second molar- MB + distal canal
• Do continuous circumferential filing along the periphery of C
with hypo irrigation.
• Do not over prepare
• Because Only little dentin in inter radicular surface.

TEN RULES TO FOLLOW
1) Do not begin endodontic therapy unless a recent and up-to-
date preoperative radiograph is available.
2) The instruments must always be precurved and equipped with
a directional rubber stop.
3) Do not begin to work to the foramen, without first having
radiographically ascertained the position of the instrument in the
canal.
4) The endodontic instrument does not work for itself, but
prepares the canal for the following instrument.
5) All endodontic instruments work on withdrawal, arriving
where the canal will accept them: “Take what the canal will give
you!”

6) In multirooted teeth, one always performs the cleaning and
shaping of one canal at a time, always starting from the easiest.
7) Each root canal deserves a series of new instruments.
8) The instruments’ working length must always be checked
electronically first and then radiographically: never take an X-ray
without consulting a reliable electronic apex locator.
9) It is advisable not to trust one’s tactile sense.
10) Never progress to the next step unless the preceding step has
been completed.

The following ten principles apply to the successful
use of currently available NiTi rotary files:
1. Poor access preparation will lead to procedural errors.
While generally important in root canal preparation, it
is crucial for the use of NiTi rotaries.
2. Files should never be forced, as
• NiTi instruments require a passive technique.
• If resistance is encountered, stop immediately and
before continuing, increase the coronal taper and
• verify the ‘‘glide path’’ using small stainless steel hand
files.
3. Canals representing difficult anatomy should be detected,
analyzed, and carefully instrumented following specific rules.

4. Files should not be overused.
• Once only is the safest number
• but the actual stress level depends upon the case.
• Hence files may be used for more than one canal, but may
have to be replaced when shaping a particularly difficult
canal.
5. Instrument breakage occurs more often during the initial stages
of the learning curve.
The clinician changing from stainless steel to NiTi should
take continuing education courses with experienced
clinicians and educators, followed by in vitro practice on
plastic blocks and extracted teeth.

6. NiTi rotaries should not be used to bypass ledges.
Confirmation of a glide path with a straight K-file is
required prior to the use of any NiTi rotary.
7. Cutting with the entire length of the file blade should be
avoided.
This total or frictional fit of the file in the canal will cause
the instrument to lock.
8. Sudden changes in the direction of an instrument caused by the
operator (i.e., stopping and starting while inside the canal) must be
avoided.
A smooth gentle reaming or rotary motion is most efficient.

9. Inspection of instruments, particularly used instruments,
by staff and doctor is essential.
• It should be remembered that NiTi has an excellent
memory.
• The file should be straight.
• If any bend is present, the instrument is fatigued and
should be replaced.
10. WL should be well established and controlled.
If a file breaks without the clinician taking notice, a
very sharp tipped instrument, upon the next insertion,
will create procedural errors.

PROCEDURAL
ERRORS
Those unfortunate occurrence that happen
during treatment, some owing to
inattention to detail, others totally
unpredictable.
-INGLE

• The formation of preparation errors is believed to be due to
the interaction of canal curvature, file design, and file
handling.
• The tendency of a file to straighten itself cannot be
completely overcome by precurving and leads to uneven
distribution of forces and hence material removal.

• ap
Apical zip/
elliptification
Ledge Apical zip
with
perforation
Ledge with
perforation

Blocked canals Instrument separation.

Zip
• The term ‘‘zip’’ was coined by Weine
• Transportation of the apical portion of the canal
• Due to overinstrumentation using inflexible files
• Elliptical in shape

Elbow
• Associated with Zipping.
• At the narrow region of the canal
• At the point of maximum curvature.
• Irregular widening occuring coronally along the inner
aspect and apically along outer aspect of the curves root.

Blocked canal
• Due to lack of recapitulation
• Insufficient irrigation.
• To do
• Hypo irrigation
• Precurve the file and explore for a ditch or access
• Due mini circumferential filing at the access without
withdrawing the file.

Instrument separation
• Abuse of a single instrument
• Instrumenting in dry canal
• Excess pressure
• Manufacturing defects

Ledge
• Causes
• Forcing the instrument apicaly.
• Attempting in calcified canals.
• Excessive enlargement of curved canals.
• Debris accumulation at the apex.
• Curved roots- buccaly or lingually.

Perforation
• Creating a ledge in the canal wall initially and
perforating through the side of the root at the
point of obstructions/ root curvature.
• Causes
• Using too large or too long instrument
• Over instrumentation

Zip with perforation
• Cutting action of instruments in the apical region,
when extended beyond the canal space, may create
an apical zip with perforation.
• It is linked to hand and rotary instruments with
sharp tips.

LASER-ASSISTED CANAL
PREPARATION
• WEICHMANN & JOHNSON
• Lasers emitting in the
• ultraviolet,
• visible (i.e., argon laser, wavelengths of 488 and 514 nm),
• Near infrared (i.e., neodymium: yttrium–aluminum-garnet laser,
1.064 m)
are weakly absorbed by dental hard tissues, such as enamel and
dentin.
• Nd:YAG laser energy, interacts well with dark tissues and is
transmitted by water.
• Excimer lasers (193, 248, and 308 nm) and erbium lasers (~3.0 m)
are strongly absorbed by dental hard tissues

• Mechanism
• Melting the dentin surface
• Vapourization of debris and pulpal tissue remnants.
• Indication
• Straight and slightly curved canals
• Wide root canals
• Contraindication
• Generates heat that may injure periapical tissue
• Cannot asses curved canals
• Is expensive

• USE IN ENDODONTIC
• (1) hard tissue,
• (2)root canal surface
• (3) the periapex
• Laser light travels straight.
• Thus special diodes are developed for curved canals as well.
Enlargement and cleaning of straight canals with an Er:YAG
laser was found to be effective and in fact faster than with
step-back preparation with K-files.

• An erbium:YAG laser was more effective in debris
removal producing a cleaner surface with a greater
number of open tubules when compared with a
Nd:YAG laser
Dentin treated
with erbium:YAG laser
Dentin surface treated with
Nd:YAG laser

Limitations
• Access into severely curved roots and the
• cost of the equipment are limitations.
• operator and patient safety are of concern ;
safety glasses specific for each wavelength,
warning signs, and
 high-volume evacuation close to the treated area.
Safety precautions include

ULTRASONIC
INSTRUMENTATION
• RICHMAN 1957
• Barbed broach connected to ultrasonic system
• HOWARD MARTIN & WALTER CUNNINGHAM 1976
• CAVITRON (dentsply)
• ENDOSONIC :- the endododntic treatment by sonic
supersonic or sunsonic system. (MARTIN & WALTER )

• Files oscillate at a frequency of 20,000-
25,000vibrations/second.
• Is Based on sound as an energy source (20-25khz)
• Two sources of energy –
• Magnetostrictive
• Piezoelectric
• MAGNETOSTRICTIVE UNIT
• Electromagnetic energy is converted into mechanical
energy.
• it generates more heat
• So it needs a water coolant.
• Expensive
• More clumpsy and less powerful

• PIEZOELECTRIC energy
• Is induced by subjecting quartz crystals or Rochelle salts
to physical force or pressure.
• Generate less heat
• Doesn’t thus require a coolant
• Transfers more energy to th efile
• More powerful thus
• Used for
• .locating calcified canals
• Retrieve broken instrument
• Root end preparation.

• Handpiece holds the k-file
• When activated it produces a movement of the shaft between
0.001” &0.004 “ @ 25-30khz frequency.
• Cutting action occur in oscillation
• Ultrasonic waves of irrigant are created.
• The heat generated increases the chemical effectiveness of
the irrigants.
• Two physical process occurs on activation:
• CAVITATION
• ACOUSTIC STREAMING

• CAVITATION:
• It is the growth and collapse of bubbles
(implosion) with resulting increase in
mechanical cleansing activity of the
solution.
• The negative pressure within the exposed
cells leads to its breakage by implosion.
• The irrigant/ coolant washes out the
broken cells.

• ACOUSTIC STREAMING
• Small but intense EDDY current or fluid movement around
the oscillating instrument.
• Improves the cleaning of the irrigant.
• Eddying occurs closer to the tip than in the coronal end of
the file, with an apicaly directed flow at the tip.

• Advantages
• Less rime consuming
• Cleaner canals by synergestic effect
• Heat enhance the NaOCl action.
• Disadvantages
• Increased chance of canal transportation.

Sonic instruments
• Sonic endodontic handpiece attach to the regular handpiece
• Air pressure is varied with an adjustable ring on the
handpiece
• Tap water irrigant is delivered through the handpiece.
• Files oscillate in larger elliptical motion at the tip.
• Inside the canal, the oscillation changes to a longitudinal
motion-up and down.- enhances efficiency.

• File have Spiral blades protruding along their length
and have non cutting tip.

• Advantages
• Better shaping than ultrasonics
• Less apical extrusion of debris due to constant irrigation.
• Produce cleaner canals.
• Disadvantages
• Rough prepared walls
• Transportation chances

NONINSTRUMENTATION
TECHNIQUE (N I T)
• Lussi et al
• minimally invasive approach for removing canal
contents and accomplishing disinfection that did not
involve the use of a file
• system consists of
a pump,
a hose,
a special valve, and
a connector that needs to be cemented into the access
cavity

• oscillations of the irrigation solution (1% to 3% NaOCl) at a
reduced pressure –- do the cleaning action.
• Cavitation likely loosens the debris.
• NaOCl dissolves viable and necrotic tissue components.
• They are then removed by suction from the low pressure.
• this system is different from other recently proposed active
irrigation systems since the latter techniques still rely on
mechanical shaping prior to the use of irrigation while a
canal undergoing NIT is not enlarged

• It has resulted in good cleaning ability in vitro.
• However, clinical moisture control and filling
root canal system, while possible, is not
straightforward.
• Not yet commercially available!!
The pump is connected to a tubing
system and via a three-way valve to a
cannula. This cannula is sealed into the
access cavity with impression material
to provide an air-tight system

• Cleaning and shaping are important, interdependent steps in
root canal treatment.
• Canal preparation is optimized when mechanical aims are
fulfilled and enlargement is acceptable; such aims include
avoiding both significant preparation errors and weakening
of the radicular structure.
• Endodontic failure and the concomitant frustration with
inadequate endodontic delivery systems have prompted
considerable expansion of endodontic concepts up to the
present time.
CONCLUSION

Taken together and performed to a high standard,with the
combination of anatomic biologic and pathophysiologic
knowledge and with the skills of the clinician,the procedures
lay the foundation for biologic success in both
straightforward and more complicated clinical cases.

Refernces
• ARNALDO CASTELLUCCI MD, DDS, ENDODONTICS
• Cohen’s Pathwaysof the PUL P -T E N T H Edition
• Ingle’s ENDODONTICS-6
• Grossman’s Endodontics

cleaning and shaping of root canal therapy

cleaning and shaping of root canal therapy

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