1. Cleaning and shaping of the root canal is essential for root canal treatment success by removing all contents from the root canal system. 2. Various techniques have been developed over time for root canal instrumentation including step-back, crown-down, and balanced force techniques. 3. Contemporary techniques such as ProTaper Next and Self-Adjusting File use engine-driven files and continuous irrigation for more efficient cleaning and shaping of the complex root canal anatomy.

1. Prepared by:
Hashim M. Hussein
M.Sc. of Conservative Dentistry

2. • Cleaning and shaping is one of the most important steps in the root
canal therapy for obtaining success in the root canal treatment.
• For the success of endodontic treatment one must remove all the
contents of the root canal completely because any communication from
root canal system to periodontal space acts as portal of exit which can
lead to formation of lesions endodontic origin.
• The two concepts, cleaning and shaping and the three
dimensional obturation are interdependent.
Obturation of root canal cannot be achieved better if
canals are not thoroughly cleaned and shaped.

3. • At the 18th century: Edward created small needles for
extirpation of pulp tissue.
• In 1852: Arthur used small files for root canal
enlargement.
• In 1885: Gates Glidden (GG) drills was introduced
• In middle of the 19th century: root canals enlarged with
broaches
• In 1915: K-file were introduced.

4. • In 1974: International Standards Organization (ISO)
specifications for endodontic instruments were published.
• In 1988: Endodontic instruments fabricated from NiTi.

5. A. Mechanical Objectives:
Five mechanical objectives by Schilder:
1. Preparation—a continuously tapering
cone to mimic natural canal shape.
2. Make preparation—in multiple planes to
form concept of “flow”.
3. Canal—narrower apically and widest
coronally.
4. Avoid transportation of apical foramen.
5. Apical opening as small as possible.

6. B. Biologic Objectives:
• All infected pulp tissue, bacteria and their by-products
should be removed from the root canal.
• Necrotic debris should not be forced periapically.
• Sufficient space for intracanal medicaments and irrigants
should be created.
• Procedure should be confined to the root canal space.

7. C. Clinical Objectives:
• The clinician should evaluate the
tooth to be treated to ensure that
the particular tooth has favorable
prognosis.
• All the overlying dentin should be
removed and there should be flared
and smooth internal walls to
provide straight line access to root
canals.
• Instruments and irrigants must go deeper into the canals to remove all
the debris and contents of root canal.

8. • After obturation, there should be complete sealing of the pulp
chamber and the access cavity so as to prevent microleakage into the
canal system.
• Tooth should be restored with permanent restoration to maintain its
form, function and esthetics.
• Patient should be recalled on regular basis to evaluate the success of
the treatment.
• Hand files are the most commonly used for endodontic instruments.
This group of instruments has been manufactured from stainless steel
instruments.
• Nickel-titanium instruments for manuel and rotary use have been
developed during the last decade. It was introduced to facilitate root
canal instrumentation.

9. 1. Reaming:
• Clockwise rotation of an instrument.
• Used with reamer.
2. Filing:
• Push-pull motion of an instrument.
• Used with file.

10. 3. Combination of Reaming and Filing:
• File is inserted with a quarter turn clockwise and
apically directed pressure (i.e. reaming) and then
is subsequently withdrawn (i.e. filing).
• This technique has also shown the occurrence of
frequent ledge formation, perforation and other
procedural errors.
• To overcome these shortcomings, this technique
was modified by Schilder. He suggested giving a
clockwise rotation of half revolution followed by
directing the instrument apically.
• Used with K-file and reamer.

11. 4. Watch Winding:
• It is back and forth oscillation of the endodontic
instrument right and left as it is advanced into the
canal.
• The angle of rotation is usually 30 to 60 degrees.
• Watch winding motion is less aggressive than quarter turn and pull
motion (Combination of reaming and filing) because in this motion, the
instrument tip is not forced into the apical area with each motion,
thereby reducing the frequency of instrumental errors.
• This technique is efficient with K-type instruments (file or reamer).

12. 5. Watch Winding and Pull Motion:
• In this, first instrument is moved apically by
rotating it right and left through an arc.
• When the instrument feels any resistance, it
is taken out of the canal by pull motion.
• This technique is primarily used with
Hedstroem files.
• When used with H-files, watch winding
motion cannot cut dentin because H- files can
cut only during pull motion.

13. • There should be a straight line access to the canal
orifices. Creation of a straight line access by
removing overhang dentine influences the forces
exerted by a file in apical third of the canal.
• Files are always worked within a canal filled with
irrigant. Therefore copious irrigation is done in
between the instrumentation, i.e. canal must
always be prepared in wet environment.

14. • Preparation of canal should be completed
while retaining its original form and the
shape.
• Exploration of the orifice is always done with smaller file
to gauge the canal size and the configuration.
• Canal enlargement should be done by using instruments in
the sequential order without skipping sizes.
• After each insertion and removal of the file, its flutes
should be cleaned and inspected.
• Smaller number instruments should be used extravagantly.

15. • Recapitulation is regularly done to loosen debris by
returning to working length. The canal walls should
not be enlarged during recapitulation.
• Overpreparation and too aggressive over enlargement
of the curved canals should be avoided.
• Establish the apical patency before starting the
biomechanical preparation of tooth. Apical patency of
the canal established and checked, by passing a
smaller number file (No. 10) across the apex.

16. • Basically, there are two approaches used for biomechanical
preparation:
A. Starting at the apex with fine instruments and working up to
the orifice with progressively larger instruments (Conventional,
Step back, Modified step back, Passive step back).
B. Starting at the orifice with larger instrument and working up to
apex with larger instruments (Step down, Crown down, Hybrid,
Double flared technique, Modified double flare, Balanced
force).
• Various other techniques have been
modified out of these two basic techniques.

17. Conventional (Standardized technique):
• It was one of the 1st technique to be used. It was
introduced by ingle.
• It uses the same WL for all instruments introduced
into a canal.
 Techniques:
• Determine WL and select initial apical file.
• Do circumferential filing to increase the apical
constriction 2 to 3 files sizes greater than initial
apical file.

18. Step back technique:
• It also known as Telescopic (Serial) canal
preparation technique. It includes keeping
the apical preparation small with a gradual
taper coronally.
• Clem was first to describe a stepped preparation of the curved canal
in which the apical portion was prepared using small, relatively
flexible instruments. The coronal portion was shaped with larger
instruments to obtain an adequate flare without undue enlargement
at the apical portion.
• Subsequently, Schilder suggested a “serial preparation” that included
enlarging to a file size #30 or #35 up to working length and then
serially reducing WL for the following instruments.

19. • To overcome instrument transportation in the apical third of root canal,
Mullaney in 1960 divided the step-back preparation into two phases:
A. Phase I: Apical preparation starting at the apical
constriction.
• Establish WL, then insert the first file into the canal with
watch winding motion.
• Remove the file and irrigate the canal.
• Lubricate the instrument for use in apical area.
• Place the next larger size files to the WL in similar
manner and again irrigate the canal.
• Repeat the process until a #30 K-file reaches the WL
(MAF) as minimum.
• Recapitulation between the files by placing a small file or
previous smaller number file to the WL. This breaks up
apical debris which are washed away with the irrigant.

20. B. Phase II: Preparation of the remainder of the root
canal, gradually stepping back while increasing in size.
• Place next file in the series to a length 1 mm short
of WL.
• Insert the file into the canal with watch winding
motion, remove it after circumferential filing,
irrigate and recapitulate by # 10 file.
• Repeat the same procedure with successively larger
files at length 1mm lessor from the previous length
of previous file.
• Similarly mid canal area and coronal part of the
canal is prepared and shaped with larger number
files.
• Finally refining of the root canal is done by master
apical file with push-pull strokes to achieve a
smooth taper form of the root canal.

22. Crown down Pressureless technique:
• Marshall and Pappin advocated this technique which involves
early coronal flaring with Gates-Glidden burs, followed by
the incremental removal of dentin from a coronal to apical
direction.
• Gates-Glidden drills can be used after scouting
the canal orifices with number 10 or 15 files.
The crown down approach begins with larger
Gates-Glidden first. After using this, subsequent,
smaller diameter Gates-Glidden are worked into
the canal with additional mm to complete
coronal flaring.

23. • Frequent irrigation and recapitulation with a
smaller file (usually No. 10 file) to prevent canal
blockage.

24. • After establishing coronal and mid root enlargement,
establish the WL with small instruments.
• Introduce larger files to coronal part of the canal and
prepare it. Subsequently introduce progressively smaller
number files deeper into the canal in sequential order and
prepare the apical part of the canal.
• Final apical preparation is prepared and finished along with
frequent irrigation of the canal system.

25. Balanced force technique:
• This technique was developed by Roane and Sabala in
1985. It involves the use of instrument with non-
cutting tip (ex: Flex-R).
• For this technique, use of triangular cross-sectioned
instruments. The decreased mass of the instrument
and deeper cutting flutes improves the flexibility of
instrument and decrease the restoring force of the
instrument when placed in curved canals.
• The coronal and mid-thirds of a canal are flared with
GG drills, and then shaping the apical area with hand
instrument.

26. • After that, balanced force hand instrumentation
begins with the typical triad of movements: placing,
cutting and removing instruments using only rotary
motions.
• First file which binds short of WL is inserted into the
canal and rotated clockwise a quarter of a turn. This
movement causes flutes to engage a small amount of
dentin.
• Now file is rotated three quarter turn
counterclockwise with apical pressure which actually
provides the cutting action by shearing off small
amount of dentin engaged during clockwise rotation.

27. • Then a final clockwise rotation is given to the
instrument which loads the flutes of file with loosened
debris and the file is withdrawn.
• The process is repeated as the instrument is advanced
toward the apex in shallow steps. After the working
depth is obtained, the file is freed by one or more
counterclockwise rotations made, while the depth is
held constant.

28. Universal ProTaper Hand technique
(modified balanced force):
• The ProTaper rotary system developed in 2001 by a group of
endodontists: professor Pierre Machtou, France); Dr. Clifford Ruddle,
United States); and Professor John West, United States) in cooperation
with Dentsply/Maillefer. Later, Hand ProTaper was introduced in
market; and in 2006 Universal ProTaper was introduced.
• ProTaper files have a convex triangular cross section and is variably
tapered across its cutting length. The progressively tapered design
improves flexibility, cutting efficiency and the safety of these files.
• The Universal ProTaper system
consists of three shaping (SX, S1,
S2) corresponding to sizes (19/.04,
17/.02, 20/.04) subsequently and
five finishing files (F1, F2, F3, F4,
F5) corresponding to sizes (20/.07,
25/.08, 30/.09, 40/.06, 50/.05)
subsequently.

29. • Technique:
 Hand ProTaper instruments were used according to the
manufacturer’s instructions using rotational movement in hour
sense exerting sufficient pressure at apical level.
 HPT file was engaged dentin lightly by rotating the handle CW
until the file just snug, then disengaged the file by rotating the
handle CCW (1/4 turn) so the dentin was cutted, then rotating
the handle CW (3/4) while simultaneously withdrawal of the file
(Loading).
 Handle motion was repeated until desired length was achieved.

32. Self-Adjusting File technique:
Engine-Driven Instruments
for Canal Preparation:
• The self-adjusting file (SAF) which a new concept in
cleaning and shaping, was developed in 2010 to
overcome the inherent remaining problems of the nickel-
titanium instruments.
• SAF (Re-Dent-Nova, Israel) which hollow file designed is a
novel system among the nickel-titanium files operating in
a different manner. It adapts itself to the canal’s original
anatomy and shape.
• It is a hollow file designed as a compressible, thin- walled
pointed cylinder either 1.5 or 2.0mm in diameter that
composed of a thin derivate of nickel-titanium latice with
high torsional and fatigue resistance.

33. • The hollow design SAF file allows for continuous irrigation
throughout the procedure. The irrigation is performed
continuously during the operation use a special irrigation
apparatus (VATEA Irrigation Device, ReDent-Nova).

34. • During the operating procedure, the
SAF is inserted into the root canal while
vibrating and is pushed in until it
reaches the measured WL. The SAF file
is operated in two cycles of 2 minutes.
• It is performed with in-and-out manual
motion and with continuous irrigation
VATEA Irrigation Device, in this way
allowing continuous fresh irrigant to be
present in the canal during the
procedure.
• The SAF is removed from the canal for
inspection after each cycle. Each SAF
file is designed and recommended for
single use.

35. ProTaper next rotary technique:
• The file has been introduced (by
DENTSPLY Maillefer) in 2013, which
has three significant design features:
1. Progressive percentage taper on a
single file, rectangular cross section
2. M-Wire technology,
3. Fifth generation of continuous
improvement, the offset design
(that the center of mass or center
of rotation, or both, are offset).
• When in rotation, files that have an
offset design produce a mechanical
wave of motion that travels along the
active length of the file.

36. • There are five ProTaper Next (PTN)
files in different lengths available for
shaping canals: X1, X2, X3, X4 and X5
corresponding to sizes 17/.04,
25/.06, 30/.07, 40/.06, and 50/.06
• For radicular access, the original ProTaper system offers the auxiliary
shaping file SX, which is used in a brushing motion on the outstroke to
pre-flare the orifice, eliminate triangles of dentin.
• The glide path may be further enlarged with either a #15 hand file or
dedicated mechanical glide path files, such as PathFiles (DENTSPLY).
• The PTN files are used with an outward brushing motion. This method
creates lateral space and enables this file to progress a few millimeters
inward. A brushing action serves to improve contact between the file
and dentine, especially in canals that exhibit irregular cross-sections.

37. • Insertion of PTN X1 file through the canal.
• Irrigate and flush out gross debris, recapitulate with a #10 file.
• In one or more passes, progression with the X1 file should be continued
until the working length is reached.
• The PTN X2 file then used to begin to advance inward. Before
encountering resistance, it has to be brushed against the dentinal walls,
which will enable the X2 file to advance inward passively and
progressively.
• Progression with the X2 file is continued until the working length is
reached. It may take one or more passes, depending on the length,
width, and curvature of the canal.
• Once the PTN X2 file has reached the working length, it is removed.
The shape may be confirmed as finished when the apical flutes of this
file are visibly loaded with dentine.

38. • residual debris and move the debris into solution, then re-irrigate to
liberate this debris.
• If the #30 hand file is snug at length, the shape is finished.
• The PTN X4 and X5 files are primarily used to prepare and finish larger-
diameter canals.
• When the apical foramen is determined to be larger than a 50.06 X5
file, other recognized shaping methods may be utilized to finish these
larger canals.
• PTN files are used at 300rpm and a torque of 2–5.2Ncm.

39. HyFlex EDM file rotary technique:
• A new rotary instrument files with controlled
memory was introduced by Coltene in 2016.
• HyFlex EDM files are produced using an
innovative manufacturing process called
Electrical Discharge Machining (This innovative
manufacturing process uses spark erosion to
harden the surface of the NiTi file). The EDM
process results in a file that is extremely
flexible and fracture resistant. In fact, HyFlex
EDM files are up to 700% more resistant to
cyclic fatigue compared to traditional NiTi
files.
• The file has controlled memory properties, that follow the anatomy of
the canal, which can significantly reduce the risk of ledging,
transportation and perforation.
• Provided as a modular system of sterile instruments, HyFlex EDM
includes, Orifice Opener, Glidepath, OneFile, and Finishing files.

40. • Regeneration by Thermal Treatment: The
built-in shape memory of HyFlex EDM files
prevents stress during canal preparation
by changing their spiral shape.
• A normal autoclaving process is enough to
return the files to their original shape and
fatigue resistance. Should the file fail to
regain its shape after heat treatment, risk
of fracture is increased, and the file
should not be used after visual
inspection.

42. • The general recommendations for the instrumentation
process are:
 Sterilize files prior to use.
 Instruments need to be inspected before and after
use.
 The number of times the instruments can be
reused is dependent on treatment and procedure.
 Operate the handpiece at 500 rpm. Recommended
torque setting is up to 2.5 N.cm.

43. WavoOne Gold technique:
• While the majority of commercially available NiTi systems
are mechanically driven in continuous rotation,
reciprocation—defined as any repetitive up and down or
forward and reverse movement—has been used to drive
endodontic instruments since 1958. Early attempts at
reciprocation utilized alternating, but equal, forward and
reverse angles of either 90 degrees or, more recently,
smaller angles of 30 degrees.
• In 2008, the concept of the “single-file technique” was
adopted by DENTSPLY International as a project in
collaboration with eight international clinicians to produce a
more optimal, dedicated, safe, unique reciprocating single
file and to identify the most suitable unequal bidirectional
angles with a motor system to generate this movement. The
outcome was the launch of RECIPROC (VDW) in 2010 and
WaveOne (Dentsply Maillefer) in 2011.

44. • WaveOne GOLD, a new generation of reciprocating files
offering simplicity, safety and single use in shaping canals.
• WaveOne GOLD instruments are manufactured in 2016
utilising a new DENTSPLY proprietary thermal process,
producing a super-elastic NiTi file. The gold process is a post-
manufacturing procedure in which the ground NiTi files are
heat-treated and slowly cooled (gold wire technology).

45. • The cross-section of
WaveOne GOLD is a
parallelogram where only
one cutting edge is in
contact with the canal wall.

47. Management of curved Canals:
• Estimate and calculate angle of curvature,
imagine a straight line from orifice towards
canal curvature and another line from apex
towards apical portion of the curve.
• The internal angle formed by interaction of
these lines is the angle of curvature.

48. • File can cut dentine evenly only if it engages
dentine around its entire circumference. Once it
becomes loose in a curved canal, it will tend to
straighten up and will contact only at certain points
along its length.
• Factor affecting success of negotiation of a curved canal:
 Degree of curvature.
 Flexibility of instrument.
 Size of root canal.
 Width of root canal.
 Skill of operator.
• This can lead to occurrence of procedural errors.
To avoid occurrence of such errors there should be
even contact of file to the canal dentine.

49. • Decrease in the Filing Force can be done by:
A. Pre-curving the file.
B. Use of smaller number files.
C. Use of intermediate sizes of files:
 It has been seen that increment of 0.05 mm
between the instruments is too large to reach
the correct WL in curved canals. To solve this
problem, by cutting off a portion of the file tip
a new instrument size is created which has
the size intermediate to two consecutive
instruments.
 There is increase of 0.02 mm of diameter per
millimeter of the length, cutting 1 mm of the
tip of the instrument creates a new
instrument size, for example, cutting 1 mm of
a number 15 file makes it number 17 file.
D. Use of flexible files.

50. • Decrease in length of actively cutting file can be
done by:
A. Anti-curvature filing:
 Concept of it was given by Lim and Stock.
Anti-curvature filing was introduced to
prevent excessive removal of dentin from
thinner part of curved canals, for example,
in mesial root of mandibular molar and
mesiobuccal root of maxillary molar.
 The walls of opposite side from curve are
instrumented more than the inner walls
resulting in a decrease of the overall degree
of canal curvature.
 Initial coronal flaring is done using rotary
files. But for middle and apical third
precurved hand instruments are used so as
to avoid strip perforation.
B. Changing the canal preparation techniques (using Crown down
technique).

51. Management of calcified Canals:
• Calcifications in the root canal system are
commonly met problem in root canal treatment.
• Various etiological factors seem to be associated
with calcifications are caries, truams and aging.
• Success in negotiating small or calcified canals is
predicted on a proper access opening and
identification of the canal orifice.
• The distance from the occlusal surface to the pulp
chamber is measured from the preoperative
radiograph.
• The most significant instrument for orifice location
is the DG–16 explorer. If an orifice is present, firm
pressure will force the instrument slightly into the
orifice, and it will “stick”.

52. • At this suspected point a fine
instrument number 8 or 10 K-
file, is placed into the orifice,
and an effort is made to
negotiate the canal.
• An alternative choice is to use
instruments with reduced flutes,
such as a canal pathfinder which
can penetrate even highly
calcified canals.
• Although most of the attempts to locate canal orifices with
calcifications are successful still there is a probability for perforation.
• The most common sign of accidental perforation is bleeding, but
bleeding may also indicate that the pulp in the calcified canal is vital.
• If there is any doubt as to whether the orifice has actually been found,
place a small instrument in the opening and take a radiograph.

53. • Once the orifice has been located, a No. 8 K-file is
penetrated into the canal to negotiate the calcified canal.
• A No. 10 K-file is too large, and a No. 6 K-file is too weak
to apply any firm apical pressure. Also the use of nickel
titanium files is not recommended for this purpose
because of lack of strength in the long axis of the file.
• Before the file is inserted into the canal, a small curve is
placed in its apical 1mm.
• Forceful probing of the canal with fine instruments and
chelating agents results in formation of a false canal and
continued instrumentation in a false canal results in
perforation.

55. Guidelines for Negotiating Calcified Canals:
 Copious irrigation all times with 2.5 to 5.25 percent
NaOCl enhances dissolution of organic debris, lubricates
the canal, and keeps dentin chips and pieces of calcified
material in solution.
 Always advance instruments slowly in calcified canals.
 Always clean the instrument on withdrawal and inspect
before reinserting it into the canal.
 When a fine instrument reaches the approximate canal
length, do not remove it; rather obtain a radiograph to
ascertain the position of the file.
 Use chelating agents to assist canal penetration to full
WL.
 Flaring of the canal orifice and enlargement of coronal
third of canal space improves tactile perception.

56.  Well angulated periapical radiographs should be taken. They
not only indicate the position of canals but also give
important information about the relative position of canal
orifice in calcified cases.
 Not anesthetizing the patient while performing access
opening can be useful in some cases. Patient should be told to
indicate when he/she feels a sharp sensation during access
with a bur.
 It is easy to tell the difference between PDL and pulp with a
small file. If file is inserted only a mm or two into the pulp,
the reaction will be sharp. If it is in PDL, reaction is often less
sharp.
 Avoid removing large amount of dentin in the hope of finding
a canal orifice. By doing this all the pulp floor landmarks are
lost also the strength and dentinal thickness of tooth gets
compromised.

57. Management of C-shaped Canals:
 Though the prevalence of C-shaped canals is low, but those requiring
endodontic treatments present a diagnostic and treatment difficulties
to the clinician.
 Some C-shaped canals are difficult to interpret on radiographs and
often are not identified until an endodontic access is made.
 These are commonly seen in mandibular second molars and maxillary
first molars especially when roots of these teeth appear very close or
fused.
 In maxillary molars, the C-shaped canal includes MB and palatal canals
or the DB and palatal canals. In the mandibular second molar, the C-
shaped canal includes MB and distal canals.

58.  Major problems come across during bio-mechanical preparation of C-
shaped canals are difficulty in removing pulp tissue and necrotic
debris, excessive hemorrhage, and persistent discomfort during
instrumentation.
 Because of large volumetric capacity of the C-shaped canal system,
along with transverse anastomoses and irregularities, continuous
circumferential filing along the periphery of the C with copious
amounts of 5.25 percent NaOCl is necessary for maximum tissue
removal and for control of bleeding.
 Over preparation of C-shaped canals should be avoided, because of
presence of only little dentin between the external root surface and
the canal system in these teeth.

59. Management of S-shaped Canals:
 S-shaped or bayonet shaped canals
pose great problems while endodontic
therapy, since they involve at least
two curves, with the apical curve
having maximum deviations in
anatomy.
 These double curved canals are
usually identified radiographically
with multi-angled radiographs, or
when the initial apical file is removed
from the canal and it simulates
multiple curves.
 S-shaped canals are commonly found
in maxillary lateral incisors, maxillary
canines, maxillary premolars, and
mandibular molars.

60.  Access preparation is flared to allow for a more direct entry.
 During initial canal penetration, it is essential that there be an
unrestricted approach to the first curve.
 Once the entire canal is negotiated, passive shaping of coronal curve
is done first, to facilitate the cleaning and shaping of the apical curve.
 To prevent stripping in the coronal curve, anticurvature or reverse
filing is recommended, with primary pressure being placed away from
curve of coronal curvature.
 Gradual use of small files with short amplitude strokes is essential to
manage these canals effectively.
 Constant recapitulation with small files and copious irrigation is
necessary to prevent blockage and ledging in the apical curve.
 Over curving the apical 3 mm of the file aids in maintaining the
curvature in the apical portion of the canal as the coronal curve
becomes almost straight during the later stages of cleaning and
shaping.