Prepared by: Hashim M. Hussein

M.Sc. of Conservative Dentistry

• 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.

• 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.

• In 1974: International Standards Organization (ISO)

specifications for endodontic instruments were published.

• In 1988: Endodontic instruments fabricated from NiTi.

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.

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.

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.

• 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.

1. Reaming:• Clockwise rotation of an instrument.

• Used with reamer.

2. Filing:

• Push-pull motion of an instrument.

• Used with file.

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.

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).

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.

• 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.

• 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.

• 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.

• 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.

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.

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.

• 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.

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.

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.

• Frequent irrigation and recapitulation with a

smaller file (usually No. 10 file) to prevent canal

blockage.

• 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.

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.

• 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.

• 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.

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.

• 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.

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.

• 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).

• 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.

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.

• 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.

• 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.

• 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.

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.

• 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.

• 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.

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.

• 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).

• The cross-section of

WaveOne GOLD is a

parallelogram where only

one cutting edge is in

contact with the canal wall.

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.

• 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.

• 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.

• 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).

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”.

• 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.

• 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.

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.

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.

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.

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.

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.

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.