Electronic Apex Locator

© Ramaiah University of Applied Sciences
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Faculty of Dental Sciences
Presented by : Dr.Arbiya Anjum S
Electronic Apex Locator
“The use of electricity in the dental office has given dignity to the profession. The supplanting of the
pedal engine by the electric engine has done much toward elevating this part of the work from pure
mechanical labor. The dentist while operating the pedal engine differed but little from the performance
of a scissors grinder in the eyes of the public. The electric engine has added tone to the dental office
and dignity to the dentist.” - Custer

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Contents
• Introduction
• Significance of working length
• Anatomical considerations and terminology
• Drawbacks of radiographic method
• History
• Function
• Resistance based EAL
• Classification of EMRCLS
• Low frequency oscillation ERCLMDs
• High frequency devices (capacitance based)
• Capacitance and resistance ERCLMDs
• Voltage gradient ERCLMDs
• Two frequencies impedance difference ERCLMDs
• Two frequencies impedance ratio ERCLMDs
• Multi frequency ERCLMDs
• Adaptive apex locators
• Comparison of EALs with different working length
determination methods
• Comparison of different EALs
• Apex locator with other functions
• Accuracy of apex locators
• Root ZX more accurate
• Bingo 1020/Ray-Pex 4
• Review of literature
• Factors influencing the functioning of apex locators
• Problems associated
• Clinical acceptance
• Advantages and disadvantages
• Conclusion
• References

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Introduction
• Root canal treatment - confined within the root canal system
• Canal terminus must be detected accurately
• Precise control of working length during process must be maintained
• Several techniques have been used for determining the apical canal terminus including electronic
methods

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Faculty of Dental Sciences©M. S. Ramaiah University of Applied Sciences
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Working length: “The distance from a coronal reference point to the point at
which canal preparation and obturation should terminate”
Significance
1) To determine the instrument length in the canal
2) Limits the depth to which the canal filling maybe placed
3) Limits the postoperative pain & discomfort , violate the apical zone
4) Determination of the success of treatment

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A = Root apex
B = Apical constriction
C = Root canal
D = Cementum
E = Dentine
F = Apical foramen

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6Ingle 6th edition
Radiographic method drawbacks
•Bisecting angle technique - Canal length often varies greatly from actual working length
Long-cone paralleling technique - more accurate
2D representation of 3D object - interpreted differently between clinicians
Determining file position - decreased as the distance from the radiographic apex increased
Digital radiographic techniques do not permit the use of long-cone paralleling technique
Radiation exposure

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(a) Superimposed files over each other in buccal and palatal canals
(b) The same image taken from another angle to see the files
separately
(a) Superimposition of the zygomatic arch over the roots of maxillary
molars
(b) Superimposition of the Torus Mandibularis over the roots of
mandibular premolars

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Tactile Method
• Seidberg et al. (1975) - 60% locate apical constriction
• Stabholz et al. 1995 - Pre-flaring , increase tactile sensation by up to 75%
• Topography of the AC can vary from tooth to tooth

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• The name ‘Electronic Apex Locator’ is not appropriate
• ‘Electronic Apical Foramen Locator’ or ‘Electronic Root Canal Length Measurement
Device’ (ERCLMD) as a generic name would be more appropriate
The fundamental operating principles of electronic
root canal length measurement devices IEJ, 39, 595–609, 2006
Why use an Apex Locator?
• 90% times, radiological Apex and actual Apex do NOT match!
• Schaeffer et al. 2005 - Major foramen deviates in the lingual/buccal plane, difficult to
locate its position even with multiplane angles

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•Use of electrical
circuits to measure WL
1918-Custer
•Electrical resistance
between PDL and
OMM measurimg
device
•Constant value at 6.5
kΩ
1942-Suzuki
•2nd person to report
electrical
measurement of root
canals
1960 - Gordon
•1st measured w/l in
patients -electrical
resistance
1962 - Sunada
• High frequency
waves and a
specially coated
file , in conductive
fluids
1979-Hasedgawa
•Voltage Gradient
Method
1983-
Ushiyama
•Filtering the
difference between
two direct
potentials after a 1
kHz rectilinear wave
Mid ’80s
•Multi-channel
impedance/ ratio
based technology
late ’80s by
Kobayashi
History

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Basic Physics And Current Electricity
• Current
• Resistance (R)
• Impedance
• Capacitor

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• Isolate the tooth well
• Dry the pulp chamber
• Now insert the snuggly fitting
• Attach file holder above the rubber stopper
• Choose longer files as we need some space for file holder
• Attach lip hook on the opposite side of the RCT tooth
• Now Put the Apex Locator on
• Start pushing the file in the canal
• Keep pushing , beep sound becomes continuous
• Now start withdrawing/ pulling
• Once we reach to 0.0 reading on the screen again, stop withdrawing
• Now adjust the silicone rubber stopper to the referral cusp or plane important
• Remove file holder
• Take the file out of the canal carefully without moving the rubber stopper
• Measure the length of the file
How to use?

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Type Of Current

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Resistance Type Apex Locators
Resistance value - 6.5 kilo ohms

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• Increasing electrical impedance across the walls of the root canal, greater apically than coronally
• At CDJ, level of impedance drops
• Detects sudden change and indicates it on the analogue meter
• Insulated probes are utilized
Impedance Type Apex Locators

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• Measures impedance of tooth at two different frequencies
• Coronal portion - constant
• As the file advances , the difference in the impedance value begins to differ greatly with maximum
differences at apical area
Frequency Type Apex Locators

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• Root canal meter
• Dentometer
• Endodontic meter, Endodontic meter S II
1st generation
• Sonoexplorer
• Endocater
• Apex finder
2nd generation
• Endex/ Apit
• Root ZX
• Apex finder AFA
3rd generation
• Bingo 1020/ Ray Pex 4
• Elements diagnostic unit
4th generation
• Additional mathematical processing
• Difficulty in dry canals
5th generation
• Adaptive type6th generation
Gordon MPJ, Chandler NP. Electronic apex locators. International Endodontic Journal, 37, 425–437, 2004.

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Nekoofar MH, Ghandi MM, Hayes SJ, Dummer PMH. The fundamental operating principles of electronic root canal
length measurement devices. International Endodontic Journal,2006;39:595–609.
Resistance based ERCLMDs
Low frequency oscillation ERCLMDs
High frequency devices
Capacitance and resistance ERCLMDs
Voltage gradient ERCLMDs
Two frequencies, impedance
difference ERCLMDs
Two frequency impedance ratio
ERCLMDs
Multifrequency devices

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Resistance based ERCLMDs
• The circuit between the endodontic file and the lip clip could be modelled by a Simple resistive
circuit
• Small DC current – applied
• Suchde &Talim 1977, Nekoofar et al. 2002, Pommer et al. 2002, Tinaz et al. 2002 - Not always
accurate when strong electrolytes, excessive hemorrhage, pus or pulp tissue was present
• Foster & Schwan 1989 - As soon as the file tip touches the electro conductive solution
(electrolyte), the DC voltage polarizes the tissues and varies its resistivity
Foster KR, Schwan HP. Dielectric properties of tissues and biological materials: a critical review. Crit Rev Biomed Eng. 1989;17(1):25-104.

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Low frequency oscillation ERCLMDs
• The structure of the endodontic instrument, canal and tissues have capacitive characteristics as well as
resistive characteristics
• Capacitance characteristics- variable with shape of canal
• Inoue (1972-73) - low frequency oscillation eg: SonoExplorer
• Assumption : Impedance value of gingival sulcus and OMM similar to PDL
Inoue N Dental "stethoscope" measures root canal.
Dent Surv. 1972 Jan;48(1):38-9.
.

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• SonoExplorer measures these two impedances and identifies the canal terminus when the readings
approach each other Individual calibration required
• Technique involved inserting a file with a silicon plastic-sheath into the gingival crevice of the tooth to be
measured and the sound produced was named the ‘gingival crevice sound’
• Then, the conventional endodontic file was inserted into the root canal and when the sound produced by
this file became ‘identical’ with the ‘gingival crevice sound’

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High frequency devices (capacitance based)
• Endocater in 1979 by Hasegawa
• High frequency reference circuit- 400 kHz
• Insulated files used- capacitance dependent only on surface area at tip
• Insulating coating-
– Narrow canals
– Curvatures
– Abrasion of coating
– Autoclaving modifies properties
Keller et al. 1991;Himel & Schott 1993

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Capacitance and resistance ERCLMDs
• Elements diagnostic unit ,2003
• Measured capacitance and resistance separately
• The device exploits a composite signal with two frequencies to measure the resistance and capacitance of the
system and then compares the measured values with its lookup table to diagnose the position of the file
• Vera and Gutierrez, 2004
– Withdraw to 0.5mm mark
– Dry access cavity

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Voltage Gradient ERCLMDS
• Ushiyama (1983) - Measure the variation in impedance when a file was inserted into the root canal
• Using bipolar electrodes and applying a 400-Hz AC, this device monitored variations in the impedance
value
• Sharp variation in the frequency determines apical constriction
• Accurate in presence of strong electrolytes
• Bipolar electrodes- bulky
Ushiyama J. New principle and method for measuring the root canal length. J Endod. 1983 Mar;9(3):97-104.

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Two frequencies impedance difference ERCLMDs
• Yamaoka, 1984 - Impedance value at 2 different frequencies
• Measures the Difference in frequencies proportional to difference in impedances
• Should be calibrated at coronal portion to determine dielectric constant of contents
• As file approaches the canal terminus, the value of the capacitance sharply increases probably because of
change in the morphology of the apical portion of the root
• Accurate irrespective of canal contents
• Not accurate in dry conditions
– Open electric circuit

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Two frequencies impedance ratio ERCLMDs
• 2 frequency single waves with different frequencies
• Kobayashi and Suda, 1994- ratio had definite value depending on frequency used, indicates location of file
in canal
• At positions close to the canal terminus, the capacitive characteristic of the impedance starts to appear
• The influence of the capacitance on the overall impedance is proportional to the frequency of the
measurement
Kobayashi C, Suda H. New electronic canal measuring device based on the ratio method. J
Endod. 1994 Mar;20(3):111-4.

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• At high frequencies (fH) the overall impedance value will be much lower than at low frequency (fL)
• That means, at the apical constriction the ratio tends towards a small value (Kobayashi & Suda 1994),
however, this phenomenon is related to the morphology of the constriction
• Lack of a constriction because of open apices (Hu¨lsmann & Pieper 1989, Goldberg et al. 2002) or an
impenetrable canal (Rivera & Seraji 1993, Ibarrola et al. 1999) have been reported as an impediment to
determine the position of the canal terminus (Oishi et al. 2002)

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Multi frequency ERCLMDs
• Endo Analyzer 8005, AFA Apex Finder
• 5 different frequencies
• Phase and amplitude of impedance
• The principle behind this device, is similar to the impedance ratio-based ERCLMDs
• It detects the canal terminus by determining a sudden change in the dominant characteristic
(capacitive or resistive) of the impedance

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• Welk et al. (2003) compared the accuracy of an impedance ratio-based ERCLMD (Root ZX) and the
Endo Analyzer
• Found that the mean distance between the electronically located canal terminus and minor diameter
was 1.03 mm for the Endo Analyzer and 0.19 mm for the Root ZX
• The ability of the devices to locate the apical constriction was 34.4 and 90.7% of cases respectively

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Adaptive apex locators
• Continuously defines humidity of the canal and immediately adapts to dry or wet canal
• 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
Electronic Apex Locators - Journal of Dental Sciences & Oral Rehabilitation 2013;Jan-March

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Comparison of EALs with different working length
determination methods
Electronic apex locator: A comprehensive literature review — Part I: Different generations, comparison with other techniques
and different usages Hamid Mosleh, Saber Khazaei, Hamid Razavian, Armita Vali, Farzad Ziaei

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Effect of pulp conditions on EAL’s accuracy
• Pommer et al - EALs were more accurate in vital teeth than in necrotic ones
• Aksiue et al - Pulp condition did not affect the accuracy of EALs
• Renner et al - Accuracy of the Novapex apex locator in posterior teeth. Thirty-five vital teeth (68 canals)
and 42 necrotic teeth (76 canals) were studied
• It was demonstrated that pulp condition did not affect the accuracy of EALs
Electronic apex locator: A comprehensive literature review — Part II: Different generations, comparison with
other techniques and different usages Hamid Mosleh, Saber Khazaei, Hamid Razavian, Armita Vali, Farzad
Ziaei

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Effect of peri-apical conditions on EALs’ accuracy
• Piasecki et al - Ability of the Root ZX II to detect the apical foramen in teeth with apical
periodontitis
• Presence of defects in the pre-apical area did not affect the accuracy of the Root ZX II
Electronic apex locator: A comprehensive literature review — Part II: Different generations,
comparison with other techniques and different usages Hamid Mosleh, Saber Khazaei, Hamid
Razavian, Armita Vali, Farzad Ziaei

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• Tri Auto ZX : The Root ZX has been combined with a handpiece to measure canal length when a rotary file is used
• The handpiece uses nickel-titanium rotary instruments that rotate at 240 to 280 rpm
• Kobayashi et al. “to get the best results, it may be necessary to use some hand instrumentation” in combination with
the Tri Auto ZX, depending on the difficulty and morphology of the root canal being treated
• Tri Auto ZX - accuracy similar to the Root ZX of 95% ,
• Alves et al. - in vitro the capacity of the Tri Auto ZX to locate the AF following removal of root filling material during
root canal treatment it was accurate to 􀊶0.5 mm in more than 80% of teeth when used following removal of root filling
• Dentaport ZX comprised of two modules: the Root ZX and the Tri Auto ZX. The handpiece uses nickel-titanium rotary
instruments that rotate at 50 to 800 rpm
Combination of Apex Locator with Endodontic
Handpiece

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Combination of an apex locator and an electrical pulp tester also have been marketed- Elements
Diagnostic Unit
Other apex-locating handpieces:
1. Kobayashi et al. - New ultrasonic system SOFY ZX uses the Root ZX to electronically
monitor the location of the file tip during all instrumentation procedures, minimizes the
danger of over instrumentation
2. The Endy 7000
Efficacy of both the electronic apex locator (EAL) and auto apical reverse (AAR) functions of the
endodontic motor MM Control compared with Root ZX II
• No difference
• EAL function of MM Control presented a greater percentage of measurements >1.01 mm longer
than AL
• AAR function provided an acceptable apical limit in 83.3% of the cases for Root ZX and 77.8% of
the cases for MM Control

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Accuracy of apex locators
Determination of the Accuracy of 5 Electronic Apex Locators in the Function of Different
Employment Protocols Tiago Nepomuceno Oliveira
Regardless of the mechanism of the device, the best results were found when
electronic RCL measurement was performed at the AF

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Root ZX more accurate
• File away from apex- capacitance very high, ratio dependent on resistance, close to 1
• File near terminus- capacitance character increases, impedance proportional to frequency, ratio-
smaller value
• Dependent on presence of constriction
• Contents no influence

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Accuracy of Root ZX series electronic apex locators (EALs) for locating
the apical constriction -90.48% to 97.62%.
J Dent Sci 2009;4(2):75−80
• Root ZX reliably measured the canal lengths to within 0.31 mm,(2%
lidocaine with 1:100,000 epinephrine, 5.25% NaOCl, RC Prep, (EDTA),
3% hydrogen peroxide, and Peridex
• Jenkins JA, Walker WA 3rd, Schindler WG, Flores CM. An in vitro evaluation of the accuracy of the Root ZX in the
presence of various irrigants. J Endod 2001;27(3):209–11.

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Bingo 1020/Ray-Pex 4
• Fourth generation device ,two separate frequencies 400 Hz and 8 kHz similar to current third generation
units
• Manufacturers -combination of using only one frequency at a time and basing measurements on the
root mean square values of the signals increases the measurement accuracy and the reliability of the
device (Apex Locator Bingo – ‘1020’ 1999)
• Kaufman et al. 2002 - As reliable as the Root ZX and also user friendly
• Tinaz et al. (2002) - As accurate as the Root ZX in an in vitro study and easier for a beginner to use in
preflared canals

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• Root ZX, Elements Diagnostic Unit and Apex Locator, Mini Apex Locator, and Apex DSP - The Root ZX and
the Mini Apex Locator devices increased significantly the precision to determine the real working length
after the preflaring procedure
• ProPex and Apex Pointer can be used safely in working length determination of teeth with large
periapical lesions, which have persistent intracanal exudate
Calıskan MK, Kaval ME, Tekin U. Clinical accuracy of two electronic apex locators in teeth with large periapical lesions. International Endodontic Journal
Influence of Preflaring on the Accuracy of Length Determination With Four Electronic Apex Locators E´ ricson Janolio de Camargo JOE 2009

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Calcium hydroxide dressing residues after different removal
techniques affect the accuracy of Root-ZX apex locator
• Ability of several techniques to remove calcium hydroxide (CH) from the root canal and determined the
influence of CH residues on the accuracy of the electronic apex locator
• Proved that calcium hydroxide residues did influence the accuracy adversely
Restor Dent Endod. 2015 Feb; 40(1): 44–49

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Influence of GP solvents used in endo retreatment on
the effectiveness of the Root ZX 2 apex locator
• 30 human, single-rooted permanent teeth were divided into three groups according to the solvent
used: group OPO (orange peel oil, n = 10), group XYL (xylol, n = 10) and group CHL (chloroform, n =
10)
• Tooth length was established visually under 5× magnification with the aid of an optic microscope
and then compared with the corresponding electronic measurement with a safety margin of ±0.5
mm
ENDO (Lond Engl) 2010;4(4)263–266

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Size of the apical foramen
• The size of the apical foramen also has an influence on electronic length determination
• Huang (1987) - when the size of the major foramen was less than 0.2 mm measurements were not affected,
even in the presence of conductive irrigants, but as it increased above 0.2 mm measured distances from the
foramen increased
• The Root ZX apex locator is accurate under a diameter apical size of 0.6 mm. In the case of diameters of 0.7
to 0.8 mm, we must adjust the files to the foramen to maintain accuracy, whereas above size 0.9 mm the
device is not accurate
Critical Diameter of Apical Foramen and of File Size Using the Root ZX Apex Locator: An In
Vitro Study Manuela Herrera JOE 2011

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Canal patency
• Canal patency appears to be more important, as dentine debris may disrupt the electrical
resistance between the inside of the canal and the periodontal ligament
• Rivera & Seraji 1993 - Constant recapitulation and irrigation ensures accurate electronic length
readings during instrumentation

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In root fractures
• Any connection between the root canal and the periodontal membrane will be recognised by the EAL
• Excellent diagnostic tool in these circumstances
• The Root ZX was more accurate in the detection of horizontal root fractures than the other EALs tested
• In contrast, the three EALs were unreliable in detecting the position of vertical root fractures
• Root ZX showed significantly better scores than the other EALs for the detection vertical root fractures.
Accuracy of three different electronic apex locators in detecting simulated horizontal and vertical root fractures
Aust Endod J 2006; 32: 64–69

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Electronic apex locator: A comprehensive literature review — Part I: Different generations, comparison
with other techniques and different usages Hamid Mosleh, Saber Khazaei, Hamid Razavian, Armita
Vali, Farzad Ziaei

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Resorption
• Possible destruction of apical constriction and loss of surrounding PDL
• Goldberg et al- accuracy of Root ZX 62.7% with a clinical tolerance of ± 0.5mm
• Dependent on operator’s experience
• Shabahang et al- Root ZX locate root end consistently even with resorption lacunae

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• Early detection and immediate treatment
• Kaufman et al- clinically acceptable to within 0.06 to 0.60 mm short of external outline of
root apex
• Root ZX compared to the Sono Explorer Mark II Junior and Apit III in detecting (small and
large) root Perforations
• The mean distance of the tip of the file from the external outline of the root surface was
short for all instruments and clinically acceptable (0.06–0.25 mm)

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Primary teeth
• Katz et al- Root ZX detect canal length similar to actual length and radiographic film
• Quick, comfortable and accurate
• Tendency to slightly under estimate root length
• For the Root ZX, there was no significant difference between those teeth with root
resorption and those without
• However, for the Tri Auto ZX, there was a significant difference in the electronic
measurements between those teeth with root resorption and those without
Tosun G, Erdemir A, Eldeniz AU, Sermet U, Sener Y. Accuracy of two electronic apex locators in
primary teeth with and without apical resorption: a laboratory study. International Endodontic Journal

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Electronic apex locator: A comprehensive literature review — Part II: Different generations, comparison with other
techniques and different usages Hamid Mosleh, Saber Khazaei, Hamid Razavian, Armita Vali, Farzad Ziaei

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Conclusion: Mobile phones do not interfere with the EWL determination
Methods:
Effect of cellular phones on electronic working length (EWL) was determined in a closed room with poor
signal strength and polyclinic set up with good signal strength
(1) without cellular phone in room
(2) with cellular phone in physical contact with EAL
(3) with mobile phone in physical contact with EAL and in calling mode for 25 secs
(4) phone placed at a distance of 40 cm from the EAL
(5) phone placed at a distance of 40 cm and in calling mode for 25 secs

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Conclusion: No difference in postoperative pain

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Conclusion:
• Root ZX mini and Mini Apex Locator have similar accuracy to the Root ZX
• Function of the three apex locators was not affected by the type of endodontic solution used
5.25% Sodium Hypochlorite, 2.625% Sodium Hypochlorite, 1.0% Sodium Hypochlorite, 0.9% NaCl, 2%
lidocaine with 1:80,000 Epinephrine, and 2% Chlorhexidine
Root ZX mini and the Mini Apex Locator, in the presence of different endodontic solutions and compare
their performance to the Root ZX electronic apex locator

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Electronic apex locator: A comprehensive literature review — Part II: Different generations, comparison with other

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• CBCT images obtained at different FOVs with voxel sizes less than 0.3 mm3 performed similarly and
better than IOPA
• Apex locator measurements were better than CBCT and periapical images, and they correlated highly
with actual length measurements
• Absence of streak and beam hardening artifacts, motion artifacts, and anatomic noise from the opposing
jaw structures

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Immature apices
• EAL readings short of WL > size 50
• Blood in canal affects reading esp in canal sizes 60 or more when measured with smaller files
• Snug fitting file recommended
Kim Y-JA, Chandler NP. Determination of working length for teeth with wide or immature apices: a review. International Endodontic Journal, 46, 483–
491, 2013)
• Immature or ‘blunderbuss’ apices tend to give short measurements electronically (Berman &
Fleischman 1984, Wu et al.1992) due to the instruments not touching the apical dentine walls
(Hu¨lsmann & Pieper 1989)

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Pacemakers
• Woolley et al. 1974 - Electromagnetic interference from dental equipment including electronic apex
locators has the potential to interfere with cardiac pacemakers
• Miller et al - tested 14 electrical dental devices in vitro for their ability to interfere with 2 different
pacemakers , electrosurgical and ultrasonic instruments interfered with pacemaker activity,
whereas the other dental devices had no effect
• The two EALs(Root ZX Endo Analyzer) and one EPT(Endo Analyzer)used in this study did not
interfere with the functioning of any of the cardiac devices tested
Safety of Electronic Apex Locators and Pulp Testers in Patients With Implanted Cardiac Pacemakers or
Cardioverter/Defibrillators Brian L. Wilson JOE
Garofalo et al. - connected EALs directly to a pacemaker in an in vitro study and found that four of five
EALs showed no effect on cardiac pacemaker function

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4 EALs tested did not interfere with the correct functioning of ICDs in vitro
More than 66.000 ICDs are implanted annually in the United States

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Influence of Preflaring on the Accuracy of
Length Determination With Four Electronic
Apex Locators
De Camargo (2009) - root ZX and the mini
Apex locator devices increased significantly the precision
To determine the real working length after the preflaring
Procedure

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Problems associated
• Unstable electronic signal with rapid
wandering signs
– Metallic restorations or cervical leak
– Removing metallic restoration
– Blowing air into wet chamber
• Sharp drop of signal at apical foramen
– Very dry canals-no electric contact
– Drops abruptly when it reaches apical
foramen
– Apex- circuit breaks out
Kim E, Lee S. Electronic apex locator. Dent Clin N Am 48 (2004) 35–54
• Apex sign from beginning
– Severely bleeding or exudating canals
– Too much electrolyte in canal
– Irrigate gently with NaOCl, saline until
drainage stops
• Premature reading, open apex
– Sharp drop in impedance due to thin
dentinal walls

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Clinical acceptance
• Cost of the instruments and exposure to the technology are also factors

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Conclusion
No individual technique is truly satisfactory in determining
endodontic working length
The CDJ is a practical and anatomic termination point for
the preparation and obturation of the root canal and this
cannot be determined radiographically
Modern electronic apex locators can determine this position
with accuracies of greater than 90% but still have some
limitations
Knowledge of apical anatomy, prudent use of radiographs
and the correct use of an electronic apex locator will assist
practitioners to achieve predictable results or as Lester
Ellsworth Custer would say... strict attention to business
is fundamental to success!

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• Ingle’s endodontics 6th edition
• The fundamental operating principles of electronic root canal length measurement devices IEJ, 39, 595–609, 2006
• The New Era of Foramenal Location Kenneth S. Serota, Jorge Vera, Frederick Barnett, Yosef Nahmias, oral health August
2004
• Gordon MPJ, Chandler NP. Electronic apex locators. International Endodontic Journal, 37, 425–437, 2004
• Nekoofar MH, Ghandi MM, Hayes SJ, Dummer PMH. The fundamental operating principles of electronic root canal
length measurement devices. International Endodontic Journal,2006;39:595–609
• Foster KR, Schwan HP. Dielectric properties of tissues and biological materials: a critical review. Crit Rev Biomed
Eng. 1989;17(1):25-104
• Inoue N Dental "stethoscope" measures root canal. Dent Surv. 1972 Jan;48(1):38-9
• Ushiyama J. New principle and method for measuring the root canal length. J Endod. 1983 Mar;9(3):97-104.
• Kobayashi C, Suda H. New electronic canal measuring device based on the ratio method. J Endod. 1994 Mar;20(3):111-4
• Electronic Apex Locators - Journal of Dental Sciences & Oral Rehabilitation 2013;Jan-March
• Electronic apex locator: A comprehensive literature review — Part I: Different generations, comparison with other
References

67
• Calıskan MK, Kaval ME, Tekin U. Clinical accuracy of two electronic apex locators in teeth with large periapical lesions.
International Endodontic Journal
• Electronic apex locator: A comprehensive literature review — Part II: Different generations, comparison with other
• Erdemir A, Eldeniz AU, Ari H, Belli S, Esener T. The influence of irrigating solutions on the accuracy of the electronic apex
locator facility in the Tri Auto ZX handpiece. International Endodontic Journal
• Calcium hydroxide dressing residues after different removal techniques affect the accuracy of Root-ZX apex locator Restor
Dent Endod. 2015 Feb; 40(1): 44–49
• Influence of GP solvents used in endo retreatment on the effectiveness of the root zx 2 apex locator ENDO (Lond Engl)
2010;4(4)263–266
• Critical Diameter of Apical Foramen and of File Size Using the Root ZX Apex Locator: An In Vitro Study Manuela Herrera JOE
2011
• Accuracy of three different electronic apex locators in detecting simulated horizontal and vertical root fractures
Aust Endod J 2006; 32: 64–69
• Reliability of different electronic apex locators to detect root perforations in vitro A. Y. KAUFMAN, Z . F U S S, S . KEILA & S.
WAXENBERG
• Kim E, Lee S. Electronic apex locator. Dent Clin N Am 48 (2004) 35–54

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