seminar 6 working length.pptx in detail all

WORKING LENGTH
Presented by
Dr. Khushbu Waghmare
MDS Part 2
Guided by
Dr Rashmi Nair

CONTENTS
Introduction 3)Electronic apex locators
History Conclusion
Definition References
Significance of Working length
Terminologies
Methods for determination of working length
1)Radiographic Method
2)Non radiographic method

INTRODUCTION
A successful root canal therapy – depends upon
-Thorough cleaning and shaping
-Three dimensional Obturation
Debridement
Disinfection
Obturation
Triad
of
Endodontics
• To achieve this objective the canal terminus must be detected during canal
preparation and precise control of working length during the process must be
maintained.

• The outcome of root canal with necrotic pulps and periapical lesions is influenced
significantly by the apical level of root canal filling (Sjogren et al. 1990).
• This can be achieved if the length of the tooth and the root canal is determined
with accuracy.
Ingle J. Endodontic instruments and instrumentation. Dent Clin North Am 1957;1,805-815

• Traditionally, the point of termination for endodontic instrumentation and obturation
has been determined by taking radiographs.
Ingle J. Endodontic instruments and instrumentation. Dent Clin North Am 1957;1,805-815

HISTORICAL PERSPECTIVES
Beginning of the era of Endodontics, working length was calculated at the site where
the patient experienced feeling for an instrument placed into canal.
• 1899 - Kell introduced application of X –ray to Dentistry
• 1900 - Radiographic apex used as the apical termination of instrumentation
& obturation.
• 1920 - Grove ,Hatton, Coolidge and others contradicted this position & indicated
that filling slightly short of the root tip gave the best results.
Sharma MC, Arora V. Determination of Working Length of Root Canal. Med J Armed Forces India. 2010 Jul;66(3):231-4

• 1955 – Kuttler Endodontist from Mexican city studied the most
comprehensive anatomy of the apex.
• 1957 – Ingle used the pretreatment radiograph in a mathematical
procedure for determining the working length

DEFINITION
The distance from a coronal reference point to the
point at which canal preparation and obturation
should terminate
Endodontic glossary

Significance of
1. Working length determines how far the instruments are placed in
to the canal and worked.
2. It will limit the depth to which the canal filling may be placed.
3. It will affect the degree of pain and discomfort that the patient will
feel following the appointment.

4. W.L calculated with in correct limits, it will play an important role in
determining the success of the treatment, if calculated incorrectly may
doom the treatment to failure.
• Grove (1930) stated that ‘the proper point to which root canals should
be filled is the junction of the dentin and cementum
According to R Elemam 86.02 % success rate of treatment is dependent on adequate
working length determination
Significance of

 Perforation through apical constriction
 Overfilling or over extension
 Increased incidence of post operative pain.
 Prolonged healing period.
 Lower success rate, owing to incomplete regeneration of Cementum,
Periodontal ligament and Alveolar bone.
Failure to accurately determine and maintain working length, may result in
length too long and lead to :

• Incomplete cleaning
• Underfilling
• Persistant discomfort
• Incomplete apical seal, apical leakage which supports
the existence of viable bacteria and contributes to a
peri-radicular lesion
• Lower success rate
Failure to determine and maintain working length accurately may result in
short working length and lead to:

 ANATOMIC APEX-
IT IS THE TIP OR END OF ROOT DETERMINED
MORPHOLOGICALLY.
RADIOGRAPHIC APEX-
IT IS THE TIP OR END OF ROOT DETERMINED
RADIOGRAPHICALLY.
TERMINOLOGIES
Alothmani OS, Chandler NP, Friedlander LT. The anatomy of the root apex: A review and clinical considerations in endodontics. Saudi Endodontic
Journal. 2013 Jan 1;3(1):1.

• It is an aperture at or near the apex of root through which
the blood vessels & nerves of the pulp enter and exit the
pulp cavity.
• The minor diameter widens apically to major diameter
• The space between the apical constriction & apical
foramen takes a hyperbolic/ funnel shape that resembles
a “Morning glory flower”.
Journal. 2013 Jan 1;3(1):1.
APICAL FORAMEN

• The mean distance between major & minor
diameter (apical foramen & apical constriction)
has been found to be:
• Young teeth - 0.5 mm &
• Older teeth - 0.65 mm
Kuttler Y. Microscopic investigation of root apexes. The Journal of the American Dental Association. 1955 May 1;50(5):544-52.

• It is the apical part of root canal with the
narrowest diameter short of apical foramen or
radiographic apex.
• Referred to as the “apical stop”. It generally lies
0.5mm to 1.5 mm short of the apical foramen.
Journal. 2013 Jan 1;3(1):1.
APICAL CONSTRICTION

• Junction where the pulpal tissue terminates &
the periodontal tissue begins.
• Violation of this area by root canal instruments
lead to postoperative discomfort & also delayed
healing.
• It acts as a natural apical stop and the root
canal instrumentation & obturation should be up
to this point.
Journal. 2013 Jan 1;3(1):1.

The apical constriction is the smallest diameter of blood supply and preparation to
this point results in a small wound site and optimal healing conditions.

TYPE A
Tapering single
constriction.
TYPE B
Tapering
constriction with the
narrowest portion
near the actual
apex.
TYPE C
Multiconstricted
TYPE D
Long parallel
constriction
DUMMER’S CLASSIFICATION (1984)
Dummer, P. M.; McGinn, J. H. & Rees, D. G. The position and topography of the apical canal constriction and apical foramen. Int. Endod. J., 17(4):192-
8, 1984.

CEMENTODENTINAL JUNCTION
• The region at which the dentin and
cementum are united; commonly used to
denote the point at which the cemental
surface terminates at or near the apex of a
tooth.
• Its position can range from 0.5 to 3.0 mm
from the anatomic apex.
American Association of Endodontists “Glossary of Endodontic Terms” 10th Edition

• Due to the deposition of cementum, the location &
diameter of the cementodentinal junction differ
considerably.
• Grove 1926 , stated pulpal tissue ends, periodontal
tissue begins at the CDJ.
• The dentino-cemental junction is the passage point
between the endodontium and periodontium, which
can be histologically, but not clinically or
radiographically identified Grove CJ. Faulty technic in investigations of the apices of pulpless teeth. J Am Dent Assoc
1926;13:746-7.

Location of the CDJ may or may not coincide with the minor diameter
Both sides of the CDJ ending at same level (53% younger group ) and (60% older group)
Ponce EH, Fernandez JAV (2003) The cemento-dentino-canal junction, the apical foramen, and the apical constriction: evaluation by optical
microscopy. Journal of Endodontics 29, 214–9.

METHODS OF DETERMINING WORKING LENGTH
Sethi, K., Shefally, S., & Raji, J. (2021). Working length determination: A review. International Journal of Health Sciences, 5(S1), 45–55.

• Introduced in 1960
• A steel pin measuring 10 mm is fixed to the labial surface of
root with utility wax ,keeping the pin parallel to long axis of tooth
& a radiograph is taken
• Then measurements were made with the help of a
BW gauge
• This method gained little success as it generally resulted in
length greater than the actual length of teeth.
BEST’S METHOD

BREGMAN’S METHOD
• 25mm flat probes are prepared and each has a steel
blade fixed with acrylic resin as a stop leaving 10mm
for placement inside root canal.
• This is placed in the tooth until the resin end touches
the incisal edge or cusp tip of the tooth.

• After placement of probe inside tooth a radiograph was
obtained.
• The working length was determined using following
formula:
Actual length of the tooth =Real instrument Length × Apparent length of tooth
Apparent Instrument Length

• Introduced in 1974. Used stainless steel probes of various calibres & length
• They were bent at one end at right angles & this bend is inserted partially into
acrylic resin in such a manner that its internal surface is in flush with the resin
surface contacting tooth surface.
• The probe is introduced in the canal such that the resin touches
the incisal or cusp tip taking care to see that the bent segment
of the probe would be parallel to mesiodistal diameter of crown
thus making it possible to visualize on radiograph
BRAMANTE’S METHOD
A
B
C

In this radiograph the reference
points are as follows –
A : internal angle of intersection of
incisal & radicular probe segment
B : apical end of probe
C : tooth apex
Tooth length calculated in 2 ways :
(I) Measure radiographic image length of probe A-B,
measuring radiographic image length of tooth
from A-C & then measuring real length of probe
A
B
C

Now following equation is applied :
CRD – real tooth length
CRS – real probe length
CAD – tooth length in radiograph
CAS – instrument length in radiograph
(II) Measure distance at apical end of probe & radiographic apex.
add or subtract to obtain correct WL. This measure is either added
or diminished to obtain the correct length of the tooth. This is somewhat similar
to that described by Ingle.
CRD = CRS x CAD/CAS

INGLE’S METHOD
This method recommended by Ingle and reviewed by Bramante and Berbert,
reported that this method is superior to other methods.
Materials and conditions required.
1. Good, undistorted, preoperative radiographs showing the total length and all roots
of the involved tooth.
2. Adequate coronal access to all canals.
3. An endodontic millimeter ruler.
4. A definite, repeatable plane of reference to an anatomic land mark on the tooth.

• Teeth with fractured cusps or cusps weakened by caries
or restoration be reduced to a flattened surface, supported
by dentin.
• Failure to do so may results in fractured cusps and weak
enamel walls between appointments thus the original
reference site is lost, and there is the probability of over
instrumentation and overfilling.

Method
i. Measure the tooth on the pre-operative
radiograph
ii. Substract at least 1 mm, which is for
possible image distortion or magnification.
iii. Set the instrument at this tentative
Working length
iv. Place the instrument in the canal
until the stop

iv. On the radiograph measure the difference between the end of the instrument
and the end of the root.
v. Add this amount to the original measured length; if the instrument has extended
beyond the apex subtract the difference.
vi. From this adjusted length of the
tooth subtract about 1 mm “Safety
factor” to conform the instrument
within the apical termination of the
root canal at the CDJ.

WEINE’S MODIFICATION
MODIFICATION IN LENGTH SUBTRACTION :
1) No resorption – subtract 1mm
2) Periapical bone loss – subtract 1.5mm
3) Periapical bone loss + root apex resorption – subtract 2mm

• The original diagnostic radiograph is used to estimate the working length of
the tooth. Diagnostic file (usually no. 10-20 K file) that fits into the root canal is
inserted till it reaches the estimated working length.
GROSSMAN’S METHOD

• W.L should be arbitrarily established 0.5 mm to 1mm shorter than the
measured canal length because :
Actual length of the tooth is 1-2mm less than the radiographic image
Apical foramen is approximately 0.3-0.5mm short of actual root tip
If the K-file is 1 mm longer or shorter of the radiographic foramen one should
add or subtract the necessary length to obtain the root canal length, but if the
differences are greater than 1 mm, one should make necessary adjustments
on the file and take another radiograph.

Actual length of instrument x Radiographic length of root
Actual length of tooth =
Radiographic length of instrument

KUTTLER’S METHOD
• According to Kuttler the narrowest diameter is definitely not at the site of exit of
the canal from the tooth(major diameter). Kuttler preferred to terminate canal
preparation at minor diameter.
• According to Kuttler ,the narrowest diameter of the canal usually occurs within
the dentin, just prior to the initial layer of cementum.

Locate the major foramen on preoperative radiographs
Estimate the length of roots, on the preoperative radiographs
Estimate the width of the canal on the radiographs
If narrow-size 10/15; Average -20/25; Wide-30/35
Use this file, set the stop and place the file into the canal and take radiographs.
Technique:-

If file is too long or short by more than 1mm from minor diameter, make the
interpolation adjust the file and retake the radiograph
If file appears too long or short from the minor diameter by less than 1mm, make
the interpolation and calculate working length
If file reaches the major diameter exactly subtract 0.5mm from that length in
young patients and 0.67 in older patients

Disadvantages:
• Requires radiograph of highest quality
• Time consuming
• Complicated
Advantages:
• Minimal errors
• Has shown many successful cases

• Everett & Fixott in 1963
• Consists of lines 1mm apart running lengthwise &
crosswise.
• Every 5th millimeter is accentuated by a heavier line to
make reading easier.
X-RAY GRID SYSYTEM

• Enameled copper wires are placed in a Plexiglas & fixed
to a regular periapical film.
• The grid is taped to a film to lie in-between the tooth &
film during exposure so patterns become incoperated
in the finished film.

ADVANTAGES :
•Simple method
•No need for calculations
DISADVANTAGES :
•Cannot be used if radiograph is bent during
exposure

• Diagnostic film is taken using paralleling technique & length is measured.
From this 3mm is subtracted to obtain estimated working length
• Then radiograph is taken
• Corrected working length is determined by measuring the discrepancy between
the tip of the file and the radiographic apex
• File is then adjusted 1-2mm short of the radiographic apex.
WALTON AND TORABINEJAD METHOD

• Xeroradiography is a highly accurate electrostatic imaging technique.
• It records images produced by x-radiation but differs from conventional
radiography in that it does not require wet chemicals or dark room for
processing.
XERORADIOGRAPHY

• In endodontics, Xero-radiographs permit better visualization of pulp
chamber morphology, root canal configuration and root outline.
• This is especially evident in maxillary molars and pre molars, in which
zygomatic arch and maxillary sinus super-impositions will hinder accurate
visualization of dental structures.
• The lamina-dura is also clearly observed.

• In this digital image is formed which is represented by spatially distributed
set of discrete pixels.
• This system consists of a programmed computerized receiver that
processes signals from an intra-oral sensor that is stimulated by x-rays.
DIRECT DIGITAL RADIOGRAPHY

RVG :
Invented by Dr.
Frances Mouyens
in 1984

ADVANTAGES :
•Low radiation dose
•Darkroom is not required as instant image is viewed
•Quality of the image is consistent
•Image distortion from bent films is eliminated
DISADVANTAGES :
•Expensive
•Large disk space required to store images
•Bulky sensor with cable attachment can make placement in mouth difficult
•Soft tissue imaging is not very accurate

ADVANTAGES :
• Can see anatomy of tooth
• Can see curvature in roots
• Can see relationship b/w adjacent teeth & anatomic structures
ADVANTAGES AND DISADVANTAGES OF RADIOGRAPHIC
METHOD –

DISADVANTAGES :
• Varies with different observers
• Superimposition of anatomic structures
• 2D view of a 3D object
• Radiation exposure
• Cannot interpret if apical foramen has buccal or lingual exit
• Limited accuracy & Time consuming

• The accuracy of radiographic methods of length determination depend on the
radiographic technique that has been used (Katz et al. 1991).
• Dense bone and anatomical structures can make the visualization of root
canal files impossible by obscuring the apex.
Katz A, Tamse A, Kaufman AY. Tooth length determination: a review. Oral Surg Oral Med Oral Pathol 1991;72:238-242.
Custer C. Exact methods for locating the apical foramen. J Nat Dent Assoc 1918;5:815-819.

TACTILE SENSE
• Experienced clinician develops a keen tactile sense and can gain considerable
information from passing an instrument through the canal.
• Careful study of the apical anatomy discloses two facts that make tactile
identification possible.
i. The unresorbed canal commonly constricts just before exiting the root .
ii. Curved canal frequently changes course in the last 2-3 mm.

• Both structures apply pressure to the file.
• A narrowing canal presses more tightly against the instrument, whereas a
curvature deflects the instrument from a straight path.
• Both consume energy and sensitize instrument with which the experienced
clinician can accurately determine passage through the foramen.

ADVANTAGES :
• Time saving
• No radiation
exposure
DISADVANTAGES :
• In case of narrow canals one may feel increased
resistance as file approaches apical 2-3mm. With
immature apex, instrument can go periapically.
• In case of anatomical variations in apical constriction,
sclerosis, resorption, tooth type and age this method
becomes unreliable.
Seidberg et al. (1975) found that, even among experienced clinicians, only
60% could locate the apical constriction by using tactile sense.
Seidberg BH, Alibrandi BV, Fine H, Logue B. Clinical investigation of measuring working lengths of root canals with an electronic device
and with digital-tactile sense. J Am Dent Assoc. 1975 Feb;90(2):379-87

.
PAPER POINT MEASUREMENT METHOD
• The paper point may be used to detect bleeding or apical moisture.
• A bloody or moist tip suggests an over extended preparation.
• The point of wetness often given an approximate location to the actual canal
end point.

This method, however, may give unreliable data :
1. If the pulp not completely removed
2. If the tooth is pulpless but a periapical lesion rich in blood supply is present.
3. If paper point is left in canal for a long time.

• The development of the (ERCLMD) has helped to assess working length in more
accurate, precise and predictable way.(Fouad & Reid 2000)
• The basic assumption with all Electronic root canal length measuring devices
(ERCLMD) is that human tissues have certain characteristics that can be
modeled by a combination of electrical components.
Fouad AF, Reid LC (2000) Effect of using electronic apex locators on selected endodontic treatment parameters. Journal of Endodontics 26,
364–7.

NEED FOR ELECTRONIC APEX LOCATORS!!!!
• According to Kuttler ,the apical foramen is not always located at the anatomical
apex of the tooth.
• The foramen of the main root canal may be located to one side of the
anatomical apex, at the distances up to 3 mm in 50–98% of roots.
Kuttler Y. Microscopic investigation of root apexes. J Am Dent Assoc 1955;50:544-552.

• The most popular method that has been use till date is radiographs.
• However, although it is generally accepted that the minor apical foramen
and apical constriction is on average located 0.5–1.0 mm short of the
radiographic apex (Katz et al. 1991) studies suggest that..
Katz A, Tamse A, Kaufman AY (1991) Tooth length determination: a review. Oral Surgery, Oral Medicine, and Oral Pathology 72, 238–42.

• The major apical foramen is not always
located at the radiographic apex
• If the major foramen deviates in the
lingual/buccal plane it is difficult to locate
its position using radiographs alone, even
with multi-plane angles (Schaeffer et al.
2005).
a) Major apical foramen (apical
opening)with protruding instruments (b) root
apex.

Typical circuit for electronic
determination of working length
Sunada I. New method for measuring the length of the root canal. J Dent Res 1962;41:375-387
Mode of action:
All EALs function by using the human body to complete an
electrical circuit.
One side of the apex locator’s circuitry is connected to the
oral mucosa through a lip clip and the other side to a file.
The file is placed into the root canal and advanced
apically until it’s tip touches periodontal tissue at the apex,
thus the electrical circuit is completed
The electrical resistance of the EAL and the resistance
between the file and oral mucosa are now equal, which
results in the device indicating that the apex has been
reached.

An apex locator typically has four parts
-The lip clip
-The file clip
-The instrument itself
-A cord connecting the other three parts
A display screen indicating the advancement of the file towards the apex.
Parts of an Apex locator

 .
of electronic apex locators
1918 -An electronic method for root length determination
was first investigated by Levitt Ellsworth Custer.
• Noted that there was difference in conductivity values in the root canal and
periodontium & could be detected more easily if the canal was dry or filled
with a nonconductive liquid such as alcohol.

• 1960- Gordon was the second to report the use of a clinical device for
electrical measurement of root canal.
• 1942 -The idea was revisited by Suzuki who studied the flow of direct
current . He registered consistent values in electrical resistance
between an instrument in a root canal and an electrode on the oral
mucous membrane and speculated that this would measure the canal
length.

• Sunada reported that a specific value of the resistance would determine the
position of the root canal terminus. He determined that when the tip of an
endodontic instrument had reached the periodontal membrane through the ‘apical
foramen’, the electrical resistance between the instrument and the oral mucous
membrane was approximately equal to 6.5 ohm.
• 1962- Sunada took these principles and constructed a simple device that
used direct current to measure the canal length.

• He claimed that if the reamer perforated the canal wall or floor of the
pulp chamber and reached the periodontal membrane, the electrical
resistance between the mucous membrane and the perforated
periodontal membrane was almost equal to the resistance shown at
the apex.

• 1970-Inoue made significant contribution to the
evolution of apex locators in North America with his
reports on the Sono Explorer.
• 1980-A third generation EALs was developed by
Kobayashi;
Simple d.c. ohmmeter
for measuring the length
of the root canal using
direct electric current

Resistance ( R)
• Opposition to direct current
Capacitor
• A structure of two conductive materials
with an insulator between them forms an
electric device- capacitor

Impedance : A circuit that has both capacitors and resistors
Total amount of opposition to an alternating current – impedance(Z)

In patients with cardiac pacemakers
Electromagnetic interference from dental
equipment including electronic apex locators
has the potential to interfere with cardiac
pacemakers (Woolley et al. 1974).
Contraindications

It was concluded that using an electronic apex
locator as an aid to endodontic therapy could
potentially reduce the number of diagnostic
radiographs required for working length
determination. Using a combination of an
electronic apex locator and radiographs to
determine working length is more accurate than
using radiographs alone.

• 1st
Generation Electronic Apex Locator ( resistance)- sunada
• 2
nd
Generation Electronic Apex Locator (impedance )
• 3
rd
Generation Electronic Apex Locator (frequency
dependant)- Kobayashi and Suda in 1994
• 4
th
Generation Electronic Apex Locator - multifrequency
CLASSIFICATION
M. P. J. Gordon & N. P. Chandle, IEJ, 37, 425–437, 2004

• First-generation EAL devices, also known as resistance apex locators.
• Which measure opposition to the flow of direct current or resistance.
• When the tip of the file reached the apex in the canal, the resistance value is
6.5 k Ω
• The disadvantage of 1GEAL devices is the pain
was often felt due to high
electric currents & Today, most of 1GEAL
devices are off the market.
First Generation Electronic Apex Locators

• The Root Canal Meter (Onuki medical Co. Japan)
was developed in 1969. It used the resistance method
and alternating current of 150 Hz .
Nekoofar et al, “The Fundamental Operating Principles of Electronic Root Canal Length Measuring Devices.” International Endodontic Journal
(2006) 39, 595-609
• It was not as popular as it gave inaccurate readings in wet canals,
obstructed canals, in carious/ defective Restorations & in case of perforations

Second Generation:
Impedance Based Apex Locators
• Second-generation EALs, also known as impedance apex locator, measure
opposition to the flow of alternating current or impedance.
• In 1972, Inoue developed Sono-Explorer (Hayashi Dental Supply, Tokyo,
Japan) one of the earliest of the 2GEALs.
• The major disadvantage of 2GEALs is that the root canal has to be reasonably
free of electro conductive materials to obtain accurate readings.
• No lip clip required as only one electrode is in contact with patient.

ADVANTAGES:
• Can Operate in fluid environment
• No patient sensitivity
• Operated with RC Prep
• Detect bifurcated canals
• Can Detect perforation

LIMITATIONS:
• Difficult to operate.
• Uses thick-coated probe as electrode,
so cannot be used in thin canals.
• Requires calibration every time.
materials to obtain accurate readings.
Nekoofar et al, “The Fundamental Operating Principles of Electronic Root Canal Length Measuring Devices.” International Endodontic
Journal (2006) 39, 595-609

Different types
1 . Sono Explorer I
-It is one of the earliest of the second generation apex locators
-Later a number of improvements were available in the sono explorer.
2. The Apex Finder
-It has a visual digital LED indicator and is self calibrating.
-Compared to radiographic working length estimations, placed the accuracy at
67 percent.
3. Endo Analyzer
It is a combined apex locator and pulp tester

4. Digipex
-It has a visual LED digital indicator and an audible indicator.
-It requires calibration.
5. Digipex I
-It is a combination of the apex locator and the pulp vitality tester.
6. Exact-A-Pex
-It has a LED bar graph display and an audio indicator.
-An in vivo study reported an accuracy of 55% (0.5mm from apex)

THIRD GENERATION APEX LOCATORS
• (frequency dependent)- Kobayashi and Suda 1994
• Basic circuit same as 2nd generation
• Two/more alternating currents of different frequencies applied
• Unit uses lip clip and is calibrated by the insertion of file into the coronal portion
of the canal

• At this point- the impedance difference between the two frequencies is
almost constant
• As the file advances apically the difference in impedance value begins to
differ and maximum at apical constriction
• Two types are as follows:

• MECHANISM: These devices calculate difference between the two
impedances obtained on applying current of two different frequencies. At
coronal portion, impedance difference is constant and at apical portion, it
begins to increase and it is highest at apical constriction.
• DEVICES: Apit / Endex (1 KHz and 5 KHz) and Justy II (500Hz and 2000Hz).
USING DIFFERENCE METHOD

ADVANTAGES:
• Operates in wet environment, even in pus and blood.
• Analogue, audible and digital indicators.
• Operates in presence of RC prep.
LIMITATIONS:
• Cannot work in dry environment.
• Requires calibration every time.

• MECHANISM: This device continuously compares the ratio of the canal
impedance to two frequencies applied to ensure accuracy under all canal
conditions.
• This ratio is expressed in terms of the position of the electrode inside the
canal.
• The microprocessor of the device calculates the quotient so that the position of
the file tip and meter reading are directly related.
• This ensures monitoring of the length of root canal.
USING RATIO METHOD

• DEVICE: Root Z X (400 Hz and 8 KHz).
The change in electrical capacitance at the apical constriction is the basis
for the operation of the Root ZX and its reported accuracy.

Different types are
1.Apex Finder AFA(all fluids allowed)
• It is a third generation apex locator.
• It functions best with an electrolyte present.
• It uses multiple frequencies and comparative impedance principles in its
electronic circuitry.
• It is operated to be accurate regardless of irrigants or fluids in the canals
being measured.

• It has a liquid crystal display(LCD) panel that indicates the distance of the
instrument tip from the apical foramen in o.1 mm increments.
• It has an audio chime indicator.
• The display has a bar graph "Canal condition indicator" that reflects
canal wetness or dryness and allows the user to improve canal conditions
for electronic working length determination.

2. Neosono Ultima Ez apex locator
• It is the third generation device that supersedes the second generation sono
explorer line.
• Two alternating current frequencies are used with a microchip that sorts out
two of the many frequencies to give an accurate reading in either wet or dry
canals.
• The ultima Ez is mounted with a root canal graphic showing file position as
well as an audible signal.
• It works best in the presence of sodium hypochlorite.

3. Endo analyzer 8005
-It combines apex location and pulp tester in one unit.
-The Endo Analyzer 8005 features two self-calibrating apex location
programs that utilize five frequencies with graphical display of the apical
foramen in 0.1 mm increments as well as an audible chime when the
foramen is reached.
4. Root Zx
-The Root Zx is mainly based on detecting the change in the electrical
capacitance that occurs near the apical constriction.

Aim : To evaluate the accuracy of the Root
ZX and Elements-Diagnostic electronic
apex locators when compared with
radiographs for locating the canal terminus
or minor foramen.
Results: The Root ZX located the
minor foramen correctly 68% of the
time in anterior and premolar teeth,
and 58% of the time in molar teeth.
The Elements-Diagnostic located the
minor foramen correctly 58% of the time
in anterior and premolar teeth and 49%
of the time in molar teeth.
Conclusion: Measuring the location of
the minor foramen using the two apex
locators was more accurate than
radiographs and would reduce the risk
of instrumenting and filling beyond the
apical foramen.

ADVANTAGES:
• It does not require calibration.
• Operates in wet environment, even in pus and blood.
• Uses K file type electrode.
• Analogue, audible and digital indicators.
LIMITATONS:
• Expensive.

• These are Ratio Type apex locators which determine the impedance at five
frequencies and have built in electronic pulp tester.
• These devices not process the impedance information as a mathematical
algorithm, but instead take the resistance and capacitance measurement and
compare them with a database to determine the distance to the apex of the root
canal.
• DEVICES: Apex Finder A.F.A (Syborn Endo),
Raypex.
Fourth GENERATION: MULTIPLE FREQUENCIES
BASED

ADVANTAGES:
• All same as those of third generation but with higher sensitivity.
LIMITATIONS:
• It is not extensively studied.
• Due to high sensitivity, even slight movement of electrode
results in change in the reading.

• Major disadvantage of the fourth generation devices is that they need
to perform in relatively dry or in partially dried canals.

FIFTH GENERATION
• Developed in 2003.
• It measures the capacitance and resistance of the circuit separately. L
• Slight difficulty in dry canals

• It uses a composite waveform of two signals, 0.5 and 4 kHz, compared with the
Root ZX at 8 and 0.4 kHz.
• The manufacturer claims that this allows less sampling error per measurement
and more consistent readings.
• They have best accuracy in any root canal condition (dry, wet, bleeding, saline,
EDTA, NaOCl).

• The Neosono-Copilot is an advanced electronic apex locator combined
with a pulp tester, capable of accurately measuring pulp space lengths even
in the presence of conductive fluids.
• It provides digital, graphical, and audible feedback, helping assess tooth
vitality and anesthesia effectiveness.
• Examples: Apex Locator C-root-1 (V), Root Pi Apex Locator.

Features: Multi-frequency technology ensures precise length
determination under wet and dry conditions. It offers two work modes (apex
locator and pulp tester), 0.1mm accuracy, a large LCD screen, and
progressive sound signals.
Advantages: Functions reliably in wet, dry, or fluid-filled canals, performs
well despite blood and exudates, and does not interfere with cardiac
pacemakers. However, it is less accurate in dry canals.

SIXTH GENERATION
• Adaptive Apex Locator overcomes as the disadvantages of the popular
apex locators 4th generation of low accuracy on working in wet canals, as
well the disadvantages of devices V th generation difficulty on working in dry
canals
• Adaptive Apex Locator continuously defines humidity of the canal and
immediately adapts to dry or wet canal.
• This way it is possible to be used in dry and in additional wetted canals as
well, canals with blood or exudates, canals with still not extirpated pulp.

• The Sixth Generation Apex Locator is a compact device, roughly the size of a
dentist’s palm.
• It features a multimedia display split into two sectors, providing real-time
graphical and audio feedback.
• Clinicians can choose between traditional beeping signals or speech messages.

• During canal penetration, the device detects contact with dentine, signaling
measurement initiation.
• Before reaching the apical zone (Sector II), a sound alert confirms the tip’s
position.
• The display and audio feedback indicate zones, with messages like “two”
for Sector II and “one” for Sector I before physiological narrowing.

• A “apex” message means the tip is between the
physiological narrowing and anatomical foramen,
while “over” signifies passage beyond the foramen.
• Examples include Root RZ-600, MAL-III, and Apex
Locator BSC-AL12.

TRI AUTO Z X2:
• This device is developed by J.Morita manufacturing
corporation, U.S.A.
• It contains cordless endodontic hand piece with built in Root
Z X apex locator.
• Auto start –stop mechanism: the hand piece automatically
starts rotating when instrument enters the root canal and stops
when it is removed.
APEX LOCATORS IN ENDODONTIC HAND
PIECES:

Auto torque reverse mechanism: The hand piece automatically stops and
reverses the rotation when the torque threshold (30 gm/cm) is exceeded. This
is to prevent breakage of instrument.
Auto apical reverse mechanism: The hand piece automatically stops and
reverses rotation when instrument tip reaches the apical constriction that has
been preset by the clinician

•Sofy ZX:
• This device is developed by J.Morita manufacturing corporation, U.S.A.
• It contains ultrasonic root canal preparation system with built in Root Z X apex
locator.
• During preparation of the root canal, the ultra
sonic vibrations can be stopped at any desired
position on the meter display, thus minimizing
the risk of over instrumentation.
Kobayashi C, Suda H (1994) New electronic canal measuring device based on the ratio method. Journal of Endodontics 20, 111–4.

• Tactile method was assessed using digital radiography and compared with electronic
method using apex locator
• Apex locator was found to be more reliable and accurate when compared with the
actual length.
Diwanji A, Rathore A, Arora R, Dhar V, Madhusudan A, Doshi J. Working Length Determination of Root Canal of Young Permanent Tooth:
An In vitro Study. Ann Med Health Sci Res. 2014 Jul;4(4):554-8.

Akshaya R, Anjaneyulu K, Anjali AK. Recent Advances in Apex Locators-A Review. Indian Journal of Forensic Medicine & Toxicology. 2020 Oct 1;14(4).
GENERATIONS EXAMPLES OPERATIVE BASE
First Generation Root Canal Meter
Endodontic Meter
Dentometer
Endo Radar
Measurements of
electrical
resistance
Second Generation Sono Explorer
Endocater
Digipex
Formatron Iv
Endodontic Meter S II
Measurements of
electrical
impedance
Third Generation Endex Or Apit
Root Zx
Dentaport Zx
Endod
Mini Apex Locators
Endy
Apex Finder
Using 2 different
frequencies at the
same time in order
to measure
difference or ratio
between 2 currents

Fourth Generation Bingo 1020
Raypex 4
Propex Apex Locators
Novapex
Ipex,apex Dsp
Using 2 or more
non-
simultaneous
continuous
frequencies in
order to measure
the difference or
ratio between 2
currents.
Fifth Generation Propex II
Apex Locator Joypex 5
I—root
Raypex 5
Measures the
capacitance and
resistance of the
circuit separately.

Comparison of apex locators and technique of working length
determination based on the previous studies
STUDY TYPE OF EALS
STUDIED
AIM OF THAT
STUDY
RESULTS
Saatchi Met
al.,2016
25
Raypex 5 apex
locators
Comparison of
Raypex 5 with
radiography in
determination of
working length.
No significant
difference seen
Weiger R et al.,
1999
Propex II Apex
locators
Comparison of
Propex II and
radiography in
working length
determination.
Propex Il is more
accurate than the
radiography.

STUDY TYPE OF EALS
STUDIED
AIM OF THAT
STUDY
RESULTS
Tinaz AC et
al.,2002
Propex Comparison of
propex and
radiography in the
working length
determination.
propex is more
accurate than
the radiography.
Cianconi Let
al.,2010
Root ZX and
Propex apex
locators
comparison of
EALs and
radiography in
working length
determination.
It is found that Root
ZX and propex is
more accurate
than radiography.
Stober EL et
al.,201120
Root ZX Comparison of
Root ZX and
radiography in
working length
determination.
No significant
difference seen

• Comparison of working length determination with radiographs and four
electronic apex locators by J.P. Vieyra et al.in 2011 concluded that Measuring
the location of the apical constriction using the four apex locators (Root ZX,
Elements, Precision AL, Raypex 5) was more accurate than radiographs
and would reduce the risk of instrumenting and filling beyond the apical
foramen.
BETTER METHOD ????

• Accuracy of working length determination using 3 electronic apex locators
and direct digital radiography by Real et al. in 2011 concluded that Root
ZX and Elements Diagnostic are more accurate in determining working
length when compared with Just Il and Schick direct digital
radiography.

Uzun O, Topuz O, Tinaz C, Nekoofar MH, Dummer PM. Accuracy of two root canal length measurement devices integrated into
rotary endodontic motors when removing gutta-percha from root-filled teeth. Int Endod J. 2008 Sep;41(9):725-32.
A study was done to evaluate the accuracy of the integrated electronic root canal
length measurement devices within TCM Endo V and Tri Auto ZX motors whilst
removing gutta-percha and sealer from filled root canals.
Conclusion: Tri Auto ZX was more accurate in a greater proportion of cases

PROBLEMS ASSOCIATED WITH THE
USE OF APEX LOCATORS
• The majority of present generation apex
locators are not affected by irrigants
within the root canal and the Root ZX
has been found to be more accurate in
the presence of sodium hypochlorite.

• Intact vital tissue, inflammatory exudates and blood can conduct electric
current and cause inaccurate readings so their presence should be
minimized before accepting apex reading. (Trope et al. 1985).
• Biological phenomena such as inflammation can still have an effect on
accuracy (Kovacevic & Tamarut 1998).
• Other conductors that can cause short-circuiting are metallic restorations,
caries, saliva and instruments in a second canal.

• Canal shape, Lack of patency, the accumulation of dentine debris and
calcifications can affect accurate working length determination with
electronic apex locators (Aurelio et al. 1983, Morita 1994).
• It has been suggested that preflaring of root canals as used in modern crown-
down preparation techniques would increase the accuracy of readings.
• This was found to be true for tactile sensation (Stabholz et al. 1995) and
accuracy with the Root ZX (Ibarrola et al. 1999).

Working Length for Open Apex
• Radiography is the main method of selecting working lengths during the
treatment of teeth with open apices.
• Numerous researchers recommend Ingle's (1957) method or from tactile sense
• Baggett et al. (1996) evaluated a tactile technique using paper points. The
technique involved using a size 30 paper point placed in the canal and advanced
until resistance was felt.
Kim YJ, Chandler NP. Determination of working length for teeth with wide or immature apices: a review. International endodontic journal. 2013
Jun;46(6):483-91.

• ElAyouti et al. (2009) proposed a tactile method involving the use of a size
25 K-file bent at the tip, with its orientation marked with a silicone ring.
• This method may be restricted to relatively straight canal curvatures (<10
degrees).
Jun;46(6):483-91.

• Rosenberg (2003) supplement initial EAL readings in relatively straight canals
(≤10 degrees).
• The technique :given that the canal is dry, an initial paper point is placed
0.5 mm short of the EAL indicated length.
Jun;46(6):483-91.

• If the point comes out dry, it is advanced apically in the canal in small
increments (0.25 mm) under magnification until some fluid is picked up.
• Another paper point is used just short of this point. The working length is
then the maximum length that a point can be placed into the canal and
remains dry.

CONCLUSION
• The CDJ or minor diameter is a practical and anatomic termination point for the
preparation and obturation of the root canal – and this cannot be determined
radiographically
• Modern apex locators can determine this position with accuracies greater than
90%
• No individual method is truly satisfactory in determining endodontic working
length

• Therefore, combination of methods should be used to assess the accurate
working length determination
• Knowledge of apical anatomy, prudent use of radiographs and correct use of
electronic apex locator will assist practitioners to achieve predictable results
CONCLUSION

• Ingle JI, Bakland LK, Baumgartner JC, editors. Ingle’s Endodontics. 6th ed. Shelton, CT: B.C. Decker; 2008.
• B Suresh Chandra, V Gopikrishna, Louis Irwin Grossman. Grossman’s endodontic practice. 11th
ed. Gurgaon: Wolters
Kluwer (India; 2014.)
• Berman LH, Hargreaves KM. Cohen’s pathways of the pulp. 12th ed. Philadelphia, PA: Elsevier - Health Sciences
Division; 2020.
• Ingle J. Endodontic instruments and instrumentation. Dent Clin North Am 1957;1,805-815
• Sharma MC, Arora V. Determination of Working Length of Root Canal. Med J Armed Forces India. 2010 Jul;66(3):231-4
• Alothmani OS, Chandler NP, Friedlander LT. The anatomy of the root apex: A review and clinical considerations in
endodontics. Saudi Endodontic Journal. 2013 Jan 1;3(1):1.
• Kuttler Y. Microscopic investigation of root apexes. The Journal of the American Dental Association. 1955 May
1;50(5):544-52.
• Dummer, P. M.; McGinn, J. H. & Rees, D. G. The position and topography of the apical canal constriction and apical
foramen. Int. Endod. J., 17(4):192-8, 1984.
• American Association of Endodontists “Glossary of Endodontic Terms” 10th Edition
• Grove CJ. Faulty technic in investigations of the apices of pulpless teeth. J Am Dent Assoc 1926;13:746-7.
REFERENCES

• Ponce EH, Fernandez JAV (2003) The cemento-dentino-canal junction, the apical foramen, and the apical constriction:
evaluation by optical microscopy. Journal of Endodontics 29, 214–9.
• Sethi, K., Shefally, S., & Raji, J. (2021). Working length determination: A review. International Journal of Health Sciences,
5(S1), 45–55.
• Custer C. Exact methods for locating the apical foramen. J Nat Dent Assoc 1918;5:815-819.
• Katz A, Tamse A, Kaufman AY. Tooth length determination: a review. Oral Surg Oral Med Oral Pathol 1991;72:238-242.
• Seidberg BH, Alibrandi BV, Fine H, Logue B. Clinical investigation of measuring working lengths of root canals with an
electronic device and with digital-tactile sense. J Am Dent Assoc. 1975 Feb;90(2):379-87
• Fouad AF, Reid LC (2000) Effect of using electronic apex locators on selected endodontic treatment parameters. Journal
of Endodontics 26, 364–7.
• Sunada I. New method for measuring the length of the root canal. J Dent Res 1962;41:375-387
• Nekoofar et al, “The Fundamental Operating Principles of Electronic Root Canal Length Measuring Devices.” International
Endodontic Journal (2006) 39, 595-609
REFERENCES

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