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Systematic Review
Electronic apex locator: A comprehensive
literature review — Part I: Different generations,
comparison with other techniques and different
usages
Hamid Mosleh, Saber Khazaei1, Hamid Razavian2, Armita Vali, Farzad Ziaei
Dental Students’ Research Center, 2Department of Endodontics, Torabinejad Dental Research Center, School of Dentistry, Isfahan University
of Medical Sciences, Isfahan, 1Department of Research, School of Dentistry, Kermanshah University of Medical Sciences, Kermanshah, Iran
A B S T R A C T
Introduction: To compare electronic apex locators (EAL) with others root canal determination techniques and evaluate other usage
of this devices. Materials and Methods: “Tooth apex,” “Dental instrument,” “Odontometry,” “Electronic medical,” and “Electronic
apex locator” were searched as primary identifiers via Medline/PubMed, Cochrane library, and Scopus data base up to 30 July
2013. Original articles that fulfilled the inclusion criteria were selected and reviewed. Results: Out of 402 relevant studies, 183
were selected based on the inclusion criteria. In this part, 108 studies are presented. Under the same conditions, no significant
differences could be seen between different EALs of one generation. The application of EALs can result in lower patient radiation
exposure, exact diagnosing of fractures, less perforation, and better retreatment. Conclusions: EALs were more accurate than other
techniques in root canal length determination.
Key words: Dental instrument, electronic apex locator, electronic medical, odontometry, tooth apex
Introduction
Ideal pulp treatment is defined as the removal of infected
pulp and cleaning, shaping, and disinfecting the root
canal system.[1] Subsequently, a three-dimensional
filling can be provided. To achieve this goal, an essential
stage is the assessment of the correct length of the root
canals.[1,2]
Working length is defined as the distance between the
coronal/incisal reference point and the area that has been
prepared and at which the filled canal should end.[1]
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DOI:
10.4103/2155-8213.136744
Commonly, the minor apical foramen or apical isthmus
is considered the end of the area for canal preparation
and filling. The minor apical foramen is the border line
between the dental pulp and periodontal area, which
is approximately 0.5-1 mm from the anatomic apex.[1,3]
Failure to determine the root canal length can result in
both over- and underestimation of the root canal length.
Overestimated working length can result in preparation
beyond the apical isthmus, which can damage the
peri-apical region.[4] Underestimated working length
and inadequate debridement can cause unsuccessful
treatment and dissatisfaction of both the patient and
dentist.[5] Due to the pivotal role of working length
determinations in root canal therapy, several methods
have been introduced as follows.
A: Tactile sensation and using the mean canal length
and the application of paper cones are examples of
experimental methods that are used by some clinicians
due to their simplicity and relative efficiency.[6] These
Corresponding Author: Dr. Hamid Razavian, Department of Endodontics, School of Dentistry, Isfahan University of Medical Sciences, Hezar Jerib
St, Isfahan-81746-73461, Iran. E-mail: [email protected]
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Mosleh, et al.: Electronic apex locator
techniques can be inaccurate in some patients, however,
due to open apex teeth and apical curvature.[6]
B: Radiography is a common method for determining
the apical isthmus, which is 0.5-1 mm shorter than
radiographic apex.[2] The radiographic method has its
advantages, such as direct observation of the root canal
system and the canal curvature and of the existence
of peri-apical lesions, [2] but radiography cannot
determine the apical isthmus, because it provides a twodimensional picture of a three-dimensional object.[2,7]
In addition, a disadvantage of radiation is that it can be
dangerous to both patients and dental staff.
C: Owing to the advantages of electronic apex locators
(EAL), such as the elimination of radiographic obstacles
and EAL’s accuracy and convenience, the application
of EAL has developed.[3,8] The principal design and
development of the early apex locators dates back
to Suzuki (1942)[9] whom investigated on dogs and
found out that the electrical resistance between the
periodontal membrane and the oral mucosa was a
constant value. This point was introduced into clinical
practice by Sunada[10] (1962) which almost measured
the electrical resistance between oral mucosa and
periodontal ligament.
Over the last decade, different versions of EAL have
been released. Table 1 shows and compares the different
versions of these devices, based on the functions of
each generation. The aim of the present study was
to investigate and compare the accuracy of EALs in
determining the working length through root canal
therapy.
Materials and Methods
English language only. Systematic reviews, case reports,
letter to editors, editorials, and congress abstracts were
excluded. The title and abstract of each article were
reviewed by three of the authors (HM, AV, and FZ), and
articles that fulfilled the inclusion criteria were selected.
Data extraction
Extraction of data from studies and assessment of
validity was independently performed by two authors
(HM and AV) and checked by a third author (FZ).
In the case of disagreement between evaluators, it
reassessed by discussion between two reviewers and a
final consensus was agreed on (HR and SKh). Figure 1
provides information on the number of papers identified
through the search strategy. Information of the authors,
their institutions, and result of primary studies were
removed before assessment of the validity. Information
on the first author, year of publication, study design,
study population and sample size, and the outcome
measurements (main results) were extracted.
Results
Out of 402 articles, 183 studies were reviewed and 108
studies were selected for this part. The studies were
categorized as follows.
Comparison of different EALs
In this part of the present study, 38 articles, consisting of
14 in vitro,[11-24] 9 ex vivo,[25-33] and 15 in vivo studies [34-48]
were reviewed. Of the in vitro studies, four articles
did not report significant differences between various
devices[12,13,16,19] [Table 2]. All of the ex vivo studies
showed significant differences between different
devices, except for the study by Comin Chiaramonti
et al.[31] and Baginska et al.[32][Table 2]. Among the
Search strategy
Electronic searches were performed using “tooth apex,”
“dental instrument,” “odontometry,” “electronic medical,”
and “electronic apex locator” as keywords. Moreover,
cross-references were screened to identify further study
that probably missed through the search strategy.
Electronic databases
Electronic searches were performed in Medline/PubMed,
Cochrane library, and Scopus data base up to 30 July
2013. Four hundred and two articles were found.
Inclusion criteria
The inclusion criteria were articles, clinical trials in
humans and cohort and case-control studies in the
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Figure 1: Flow chart of selected articles
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Mosleh, et al.: Electronic apex locator
Table 1: Different generations of electrical apex locator devices and their operation base[86]
Generation Operation base
First
Second
Third
Fourth
Fifth
Device samples
Measurement of electrical resistance
Root canal meter (Onuki medical Co.tokyo, Japan)
Endodontic meter(Onuki medical Co.tokyo, Japan)
Dentometer (Dahlin ectromedicine, Copenhagen, Denmark)
Endo Radar (Electronica liarre, Imola, Italy)
Measurements of electrical impedance
Sono-Explorer (Hayashi Dental Supply, Tokyo, Japan)
Endo Cater (Yamaura Seisokushu, Tokyo, Japan)
Digipex (Mada Equipment Co.Carlstadt, NJ, USA)
Exact-A-Pex (Ellman International Hewlett, NY, USA)
Formatron IV (Parkell Dental, Farmingdale, NY, USA)
Endodontic Meter S II (Onuki Medical Co., Tokyo, Japan)
Sono-Explorer Mark II (Hayashi Dental Supply, Tokyo, Japan).
Sono-Explorer Mark II Junior (Hayashi Dental Supply, Tokyo, Japan)
Using two different frequencies at the same
Endex/Apit (Osada Electrica Co. Tokyo, Japan)
time in order to measure the difference or ratio Root ZX (J.Morita, Tokyo, Japan)
between two currents
Neosono Ultima EZ (Satelec Inc, Mount Lourel, Nj, USA)
TCM Endo V (Nouvag Ag, Goldach, Switzerland)
Apex Pointer (MicroMega, Besanc¸on, France)
Dat Apex (Dentsply Maillerfer, Ballaiques, Switzerland)
Just or Justy II (Yoshida Co.Yokyo, Japan)
Mark V Plus (Moyco/Union Broach, Bethpage, NY, USA)
Apex pointer Endy 5000 (Loser, Leverkusen, Germany)
Mini Apex Locator (Sybron Endo, Anaheim, CA, USA)
Dentaport ZX (J. Morita MFG Corp., Osaka, Japan)
Endo Analyzer Model 8005 (Analytic/Endo, Orange, CA, USA)
Apex Finder AFA (Analytic Technologies, Redmond, WA)
Mark V Plus (Moyco/Union Broach, Bethpage, New York, USA)
Endox (Co. Lysis, Milan, Italy).
Endy (Loser, Leverkusen, Germany)
Apex Finder (Endo Analyzer 8001; Analytic
Technology, Redmond, WA, USA)
Foramatron D10 (Parkell Electronic Division,
Farmingdale, New York, USA).
Using two or more non-simultaneous
Bingo1020/Raypex4 (Foroum Engineering Technologies Rishon Lezion, Israel)
continuous frequencies in order to measure
Raypex4 (VDW, Munich, Germany)
the difference or ratio between two currents
Element Dianostic Unit & Apex Locator (Sybron Endo, Anaheim, CA, USA)
Neosono MC (Amadent Medical and Dental, Co.,
Cherry Hill, New Jersey, USA).
Propex (Dentsply Maillerfer, Ballaiques, Switzerland)
Novapex (Foroum Engineering Technologies Rishon Lezion, Israel)
Apex NRG XFR (Medic NRG Ltd, Tel Aviv, Israel)
Apex DSP (Septodont, Saint-Maur des Fosse´s, Cedex, France)
AFA Apex Finder, Model 7005 (Ana-lytic Endodontics, Orange, CA)
iPex (NSK Ltd, Tokyo, Japan)
Romi Apex D-30 (Romidan LTD, Kiryat-ono, Israel)
Measures the capacitance and resistance
Propex II (Dentsply Maillerfer, Ballaiques, Switzerland)
of the circuit separately
Top of Form
Bottom of Form
Apex Locator Joypex 5 (Henan, CBD Neihuan Road, Zhengzhou, China)
I-ROOT (E-Magic Finder)(S-Denti SEoul, South Korea)
Raypex 5 (VDW, Munich, Germany)
in vivo studies, Welk et al.[34] and Arora et al.[47] found
a significant difference between EALs [Table 2].
Comparison of EALs with different working length
determination methods
Thirty-one studies evaluated different methods of
working length determination. Among these studies,
eleven compared different EALs and conventional and
digital radiography as three different methods of working
length determination.[7,35-46,49-59] Among the studies that
compared EALs to radiographic method, six studies
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did not report any significant differences, [7,35,36,43,53,54]
three studies concluded that radiography method was
more accurate,[49,55,59] and the remainder reported greater
accuracy with the EAL [Table 3]. Three studies that
compared digital radiography to EAL showed that EAL
was more accurate[37,54,60] [Table 3]. Shanmugaraj et al.[6]
compared three methods of measuring root canal length
(apex locator, radiography, tactile sense) and reported
that EAL was the most reliable method, but Ounsi
et al.[61] showed that EAL and radiography method have
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Mosleh, et al.: Electronic apex locator
Table 2: Comparison of different electronic apex locators (EALs) in working length determination
Authors
Type of Publication Sample (n) Types of studied
study
year
ELA
Comin Chiaramonti
et al.[31]
Ex vivo
2012
40 teeth
Baginska et al.[32]
Ex vivo
2012
40 teeth
Somma et al.[89]
In vivo
2012
30 teeth
Paludo et al.[48]
In vivo
2012
100 root
Canals
Jung et al.[15]
In vitro
2011
104 teeth
Stober et al. [90]
In vivo
2011
40 root
canals
Stober et al.[87]
In vivo
2011
40 root
canals
Miletic et al.[91]
In vivo
2011
48 root
canals
Silveira et al. [88]
In vivo
2011
23 teeth
deVasconcelos
et al. [28]
Ex vivo
2010
38 teeth
Guise et al.[17]
In vitro
2010
40 teeth
D’Assuncao et al. [33] Ex vivo
2010
31 teeth
Pascon et al. [92]
In vivo
2009
831 root
canals
Higa et al.[13]
In vitro
2009
12 teeth
Siu et al. [93]
In vivo
2009
29 teeth
Pascon et al.[25]
Ex vivo
2009
60 teeth
Ebrahim et al.[16]
In vitro
2007
32 teeth
D’Assuncao et al.[18] Invitro
2007
40 teeth
Bernardes et al.[12]
2007
40 teeth
Invitro
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Aim of study
Bingo 1020
Propex
Comparing operation
of different apex
locator devices
Raypex 5, Apex
Comparing operation
D.S.P and Locapex of different apex
Five
locator devices
Dentaport ZX,
Comparing operation
Raypex 5,
of different apex
ProPex II
locator devices
Apex and iPex
Comparing the
accuracy of EALs in
length measurement
Root ZX,
I-Root
Comparing operation
of different apex
locator devices
Raypex 5
Comparing operation
Mini Apex Locator
of different apex
locator devices
Root ZX and iPex
Comparing operation
of different apex
locator devices
Dentaport ZX,
Comparing operation
RomiApex A-15 and of different apex
Raypex 5
locator devices
Root ZX,
Comparing operation
Novapex
of different apex
locator devices
Root ZX, RomiApex Comparing operation
D-30, and Ipex
of different apex
locator devices
Comparing operation
Root ZX II,
of different apex
Elements AL,
locator devices
Precision AL
Root ZX-II, Novapex, Comparing operation
Mini AL
of different apex
locator devices
DentaPort ZX,
Comparing operation
Raypex 5
of different apex
locator devices
Justylll, Dentaport, Comparing operation
E-Magic Finder
of different apex
locator devices
Root ZX II, Apex
Comparing operation
NRG
of different apex
XFR, Mini Apex
locator devices
Locator
Dentaport ZX,
Comparing operation
Raypex 5 Elements of different apex
Diagnostic Unit and locator devices
AL
Dentaport ZX,
Comparing operation
ProPex,
of different apex
Foramatron D10,
locator devices
Apex NRG,
Apit 7
Mini AL, Root ZX II Comparing operation
of different apex
locator devices
Root ZX, Elements Comparing operation
Diagnostic Unit and of different apex
A L, RomiAPEX
locator devices
D-30
Main study result
Type of
generation
No significant
difference
Fourth
No significant
difference
Fifth
No significant
difference
Third and
Fourth
There weren’t
significant
differences and
both devices were
accurate
No significant
difference
Fourth
No significant
difference
Fourth
No significant
difference
Third and
Fourth
No significant
difference
Third and
Fourth
No significant
difference
Third and
Fourth
Root ZX was more
accurate
Third and
Fourth
Third
Root ZX II was more Fourth
accurate
Root ZX II was more Fourth
accurate
No significant
difference
Third and
Fourth
Justylll was more
accurate
Third and
Fourth
No significant
difference
Third
Elements
Diagnostic Unit and
A L was not accurate
than others
Dentaport ZX,
ProPex,
Foramatron D10
were more accurate
Third and
Fourth
No significant
difference
Fourth
No significant
difference
Third and
Fourth
Third and
Fourth
(Continued )
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Mosleh, et al.: Electronic apex locator
Table 2: (Continued)
Authors
Type of Publication Sample (n) Types of studied
study
year
ELA
Aim of study
Main study result
Type of
generation
Wrbas et al.[94]
In vivo
2007
20 teeth
Root ZX
Raypex5
No significant
difference
Third
Stavrianos et al.[24]
In vivo
2007
80 root
canals
Dentaport
ZX,RayPex 4
No significant
difference
Third and
Fourth
Venturi et al.[26]
Ex vivo
2007
60 root
canals
Root ZX, Apex
Finder
Root ZX was more
accurate
Third
Topuz et al.[19]
In vitro
2007
47 teeth
TCM Endo V
Root ZX
Comparing operation
of different apex
locator devices
Comparing operation
of different apex
locator devices
Comparing operation
of different apex
locator devices
evaluating the
accuracy of the
apex-locating function
of the TCM Endo V
and to compare the
results to these of
the Root ZX
Third and
Fourth
Ebrahim et al.[27]
Ex vivo
2006
36 teeth
Plotino et al.[30]
Ex vivo
2006
40 teeth
D’Assunco et al. [20]
In vitro
2006
40 teeth
Root ZX, Foramatron
D10, Apex NRG and
Apit 7
Root ZX, Elements
Diagnostic Unit and
A L,
ProPex
Novapex
Root-ZX
TCM Endo V proved
to be as reliable as
Root ZX but the use
of the
device to determine
the working length
was not easy as
Root ZX
Root ZX and
Foramatron D10
were more
ProPex was not
accurate than others
Hor et al.[29]
Ex vivo
2005
193 teeth
Justy II
Raypex4
Haffner et al.[95]
In vivo
2005
40 teeth
ElAyouti et al.[14]
Ex vivo
2005
182 root
canals
Root ZX
Endy
Justy II
EndoxLysis
Raypex 4, Apex
pointer, Root ZX
Venturi et al.[96]
Invivo
2005
64 teeth
Apex Finder,
Root ZX
Lucena-Martin
et al.[11]
In vitro
2004
20 teeth
Hoer et al.[46]
In vivo
2004
75 teeth
Justy II,
Root ZX,
NeosonoUltima EZ
Justy II, Endy 5000
Welk et al. [34]
In vivo
2003
32 teeth
Root ZX
Endo Analyzer
Model 8005
De Moor et al. [21]
In vitro
1999
15 single
canal teeth
Apex Finder
AFA Model 7005,
Apex-Finder,
Neosono
Ultima EZ and
Apit 2
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Comparing operation
of different apex
locator devices
Comparing operation
of different apex
locator devices
to compare the
accuracy of the RootZX and
Novapex electronic
apex locators (EALs)
in locating the apical
foramen
Comparing operation
of different apex
locator devices
Comparing operation
of different apex
locator devices
Third and
Fourth
Third and
Fourth
Root-ZX and
Third and
Novapex are
Fourth
useful and accurate
devices for the apical
foramen location
Raypex4 was more
accurate
Third and
Fourth
No significant
difference
Third
Comparing operation Root ZX was more
of different apex
accurate
locator devices
Comparing operation No significant
of different apex
difference
locator devices
Comparing operation No significant
of different apex
difference
locator devices
Comparing operation No significant
of different apex
difference
locator devices
Comparing
Root ZX was more
operation of
accurate
different apex locator
devices
The accuracy
Apex Finder AFA
and operator
Model 7005 was the
dependency of four
most
electronic
accurate
canal length measuring
devices
were compared under
a set of specified
conditions
Third and
Fourth
Third
Third
Third
Third
Third
(Continued )
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Table 2: (Continued)
Authors
Weiger et al. [22]
Type of Publication Sample (n) Types of studied
study
year
ELA
In vitro 1999
41 teeth
Root ZX
Apit
Lauper et al.[97]
Ex vivo
1996
130 root
canals
Apit and
Odontometer
Arora et al. [47]
In vivo
1995
61 root
canals
ENDEX and RCM
Mark II
Pallares and Faus [98] Ex vivo
1994
116 root
canals
Odontometer and
Endo Cater
Nahmias et al. [23]
1987
60 single
root teeth
Sono-Explorer,
C. L. Meter and
Neosono-D
In vitro
Aim of study
Main study result
Two apex locators
In the presence of
were compared
NaOCl, Root ZX
regarding their ability to provides the most
accurately locate the accurate
apical constriction in
EWL measurements
the presence of various
canal fluids at different
meter
readings.
Evaluated the accuracy Apit was more
of EAL in length
Accurate
measurement
Comparison the
ENDEX was higher
accuracy of EALs
accuracy than the
in canal length
RCM Mark II
measurement in present
of different contents(vital
pulp, necrotic pulp, pus/
exudates, sodium
hypochlorite, and water)
Compared the
Endo Cater was
accuracy of EAL in
higher accuracy than
length measurement
the Odontometer
Compared the
All EALs were
accuracy of EAL in
accurate
length measurement
Type of
generation
Third
First and Third
Third
First and
Second
Second and
Third
same accuracy and significantly were more accurate
than tactile method. In the study by Subramaniam
et al.[62], there were no significant differences among
conventional radiography, digital radiography, and
tactile sense in primary teeth. Janner et al.[63] compared
cone beam computed tomography to EAL in root canal
length determination and concluded that both two
methods were comparable [Table 3].
determining the canal length of 79 teeth (93 canals).
They showed that these devices can specify the sites of
the minor and major apical foramen, but they cannot
determine apical constriction with sufficient accuracy.
Also, Oishi et al.[77] investigated the accuracy of EALs in
determining apical constriction, and they were accurate
[Table 4].
Use of EAL in root perforations, fractures, and
apical foramen widening
Six articles were published on this topic.[78-81] Two of
them evaluated the accuracy of EALs before and after
canal filling and showed that, in most cases, EALs
were accurate in root canal retreatment.[78,80] In the
study by Aggarwal et al.[80], the accuracy of Root ZX
and Protaper devices was evaluated in the retreatment
of filled canals with: 1) gutta-percha+ zinc oxide
ogenol sealer; 2) gutta-percha+ AH plus sealer; and 3)
Resilon+ Epiphany sealer. Both devices showed high
accuracy in the first and second treatments, and no
significant differences were reported in the presence
of different filling materials. Uzun et al.[79] studied the
precision of two apex locators (tri auto ZX TCM, locating
handpieces endo apex) in root canal retreatment with
root-end-cured teeth evaluated. They demonstrated
that both devices could be used for determining apical
area, but for root canal retreatment, accuracy of 0.0 mm
is required, which these devices could not accomplish
[Table 4].
Ten studies reported other uses of EALs, such as
identification of root perforation sites and the location
of horizontal and vertical fractures. EALs were only
accurate in horizontal fracture diagnosis[64,65] although
Topez et al.[66] reported that EALs were accurate in both
vertical and horizontal root fractures. Furthermore,
Goldberg et al.[67] studied the consistency of EALs in
teeth with simulated horizontal root fractures, and
they showed that EALs were accurate and consistent.
Several studies showed that EALs were able to detect
perforation sites [Table 4].[68-71] There were five studies
that evaluated EALs’ ability to control apical foramen
widening with rotary files, and they both concluded
that use of EALs in root canals that were prepared with
rotary instruments was not sufficiently accurate to
control apical extensions.[72-75] Hoer et al.[76] evaluated
the ability of the Justy II and Endy 5000 devices in
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Table 3: Comparison of electronic apex locators (EALs) and different other techniques in working length
determination
Authors
Orosco et al.[60]
Type of
study
In vivo
Publication Sample (n)
year
2012
25 teeth
Kishor[99]
In vitro
2012
Chougule et al.[58] In vivo
2012
Zand et al.[100]
In vivo/
Ex vivo
In vivo
2011
Parekh and
Taluja[101]
Janner et al.[63]
Ex vivo
2011
In vivo
2011
Neena et al.[54]
In vivo
2011
Singh et al.[57]
In vivo
2011
Real et al.[51]
In vitro
2011
Patino-Marin
et al.[45]
Kqiku et al.[7]
In vivo
2011
Ex vivo
2011
Vieyra et al.[38]
In vivo/In
vitro
2011
Mancini et al.[44]
Ex vivo
2011
Cianconi et al.[37]
Ex vivo
2010
Sharma and
Arora[102]
Vieyra et al.[46]
In vivo/
Ex vivo
In vivo
2010
Javidi et al.[40]
In vitro
2009
Kim et al.[43]
In vivo
2008
Krajczar et al.[39]
In vitro
2008
Hassanien et al.[50] In vivo
2008
Jarad et al.[36]
2011
2010
Shanmugaraj
et al.[6]
In vivo/In
vitro
2007
Smadi et al.[51]
In vivo
2006
Subramaniam
et al.[62]
In vitro
2005
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Types of
studied ELA
Root ZX
Aim of study
Main study result
Comparison of EAL and radiography Conventional and EAL
in determination of working length
were comparable and
better than digital
35 teeth
Foramatron D10 Comparison of EAL and radiography, EAL are more accurate
radiovisography in determination of
working length
13 primary teeth Dentaport ZX
Comparison of EAL and radiography EAL are more accurate
in determination of working length
75 teeth
Root ZX
Comparison of EAL and radiography No significant difference
in determination of working length
46 teeth
Raypex 5
Comparison of EAL and radiography No significant difference
in determination of working length
20 patients
Root ZX
Comparison of EAL and radiography Radiography and EAL
in determination of working length
can be used together
3 patients
Root ZX
Compared CBCT method to EAL
Two methods were
comparable
30 teeth
—
Comparison of EAL and
No significant difference
radiography in determination of
working length
20 teeth
Propex II
Comparison of EAL and radiography EALs are more accurate
in determination of working length
37 root canals Root ZX
Comparison of EAL and radiography EALs are more accurate
Just II
in determination of working length
Elements
Diagnostic
61 root canals of Root ZX and
Comparison of EAL and radiography EALs are more accurate
primary teeth
ProPex
in determination of working length
30 teeth
Root ZX
Comparison of EAL and radiography No significant difference
in determination of working length
245 teeth (693 Root ZX,
Comparison of EAL and other
EALs are more accurate
root canals)
Elementsmethods in determination of working
Diagnostic,
length
Precision AL
and Raypex 5
120 teeth
Endex, Propexll Comparison of EAL and other
EALs are more accurate
and Root ZX
methods in determination of working
length
101 teeth
Endex
Comparison of EAL and radiography EALs are more accurate
ProPex II
in determination of working length
Root ZX
100 teeth
Root ZX
Comparison of EAL and radiography EALs are more accurate
in determination of working length
160 teeth
Root ZX and
Comparison of EAL and radiography EALs are more accurate
Elementsin determination of working length
Diagnostic
30 teeth
Root ZX
Comparison of EAL and radiography Radiography and EAL
in determination of working length
can be used together
25 teeth
Root ZX
Evaluating EAL with or without
No significant difference
radiography in determination of
working length
70 teeth
ProPex
Comparison of EAL and radiography EAL are more accurate
in determination of working length
20 patients
Root ZX
Comparison of EAL and radiography EAL are more accurate
in determination of working
30 teeth
Foramatron-IV
Comparison of EAL and other
EAL are more accurate
methods in determination of working
length
151 root canals Tri Auto ZX
Comparison of EAL and radiography Use of EAL could reduce
in determination of working length
need for additional
radiography
20 teeth
Formatron D10 Comparison of EAL and other
No significant difference
methods in determination of working
length
(Continued )
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Mosleh, et al.: Electronic apex locator
Table 3: (Continued)
Authors
Type of
study
Publication Sample (n)
year
Types of
studied ELA
Aim of study
Main study result
ElAyouti et al.[41]
In vitro
2002
30 teeth
Root ZX
EAL are more accurate
Brunton et al.[42]
In vitro
2002
50 teeth
-
Martinez-Lozano
et al.[35]
In vitro
2001
70 teeth
Apit EM-S3
Saad et al.[103]
In vivo
2000
14 teeth
Root ZX
Ounsi et al.[61]
In vitro
1998
37 teeth
Endex
Comparison of EAL and radiography
in determination of working length
Effect of apex locator on reduction
X-ray exposure
Comparison of EAL and
radiography in determination of
working length
Effect of apex locator combining
Root ZX and a digital imaging
system (RadioVisioGraphy]on
reduction X-ray exposure
Comparison of EAL and
radiography, tactile sense method in
determination of working length
Himel et al.[55]
In vivo
1993
96 root canals
Formatron IV
Hembrough
et al.[49]
In vivo
1993
26 maxillary
molar teeth
Sono-Explorer
Mark III
Frank et al.[56]
In vivo
1993
185
root canal
Endex
Trope et al.[59]
In vivo
1985
Murakami et al.[104] In vivo
2002
127 root canals Sono-Explorer
Mark III
66 infected
Sono-Explorer
canals
Comparison of EAL and radiography
in determination of working length
To retrospectively assess the
success of endodontic treatment
that had been guided by audiometric
(electronic) measurement.
Stavrianos
et al.[105]
Ounsi et al.[106]
In vivo
2007
85 teeth
Raypex 5
In vitro
1999
39single root
teeth
Root ZX
Evaluated the accuracy of EAL in
length measurement
Evaluated the accuracy of EAL in
length measurement
Vajrabhaya
et al.[107]
Shabahang
et al.[108]
Wu et al.[109]
In vivo
1997
In vivo
1996
20
Root ZX
Single root teeth
26 root canals Root ZX
In vivo
1992
Ricard et al.[110]
In vivo
Compared EAL with radiography
method in length measurement
1991
20 single root
teeth
37 teeth
Sono-Explorer
type Y-III
RCM Mark II
McDonald et al.[111] In vivo
1990
47 teeth
Endocater
Berman et al.[112]
In vivo
1984
Busch et al.[113]
In vitro
1976
24 mature
Neosono-D
and 5 immature
root canals
77 teeth (46 vital Sono-Explorer
and 26 necrotic)
Use of EAL in patients with pacemakers
Wilson et al.[82] investigated the operation of the Endo
Analyzer Model 8005 in patients with pacemakers and
cardioverter/defibrillator devices. They demonstrated
that there was no interference between the apex locator
and pacemaker function.
Jul-Sep 2014 / Vol 5 | Issue 3
Comparing the accuracy of EALs
and radiography method in length
measurement
Compared the accuracy of EAL
and radiography method in length
measurement
Evaluated the accuracy of EAL in
length measurement
Evaluated the accuracy of EAL in
length measurement
Evaluated the accuracy of EAL in
length measurement
Evaluated the accuracy of EAL in
length measurement
Evaluated the accuracy of EAL in
detecting apical constriction
Evaluated the accuracy of EAL in
length measurement
Evaluated the accuracy of EAL in
length measurement
Use of EAL reduced
patients X-ray exposure
No significant difference
This technique was
useful
Tactile sense method
was inaccurate, but other
two methods were same
accurate
EALs weren’t accurate
EAL is useful only
combined with
radiography and couldn’t
replace it
EAL was comparable
with radiography method
EAL wasn’t accuracy
same as radiography
Use of the SonoExplorer
aided successful
treatment of infected root
canals
EAL was accurate
Root ZX couldn’t detect
apical constriction and
should only use to
detecting major foramen
In clinical acceptable
range its accurate
In clinical acceptable
range its accurate
In clinical acceptable
range its accurate
In clinical acceptable
range its accurate
It was accurate
EAL only in mature canal
was accurate
EAL was accurate in
both groups
Discussion
Different generations of EALs, with improved functions
and greater clinical applications, have entered the market
over these past few decades. Our results indicate that
there are no significant differences between different
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Table 4: Other usage of electronic apex locators (EALs)
Authors
Aggarwal et al.[80]
Type of
study
In vitro
Publication Sample (n)
year
2010
60 teeth
Types of studied
ELA
Root ZX and
ProPex
Stavrianos et al.[114]
In vitro
2008
40 teeth
Alves et al.[78]
Ex vivo
2005
62 teeth
Dentaport ZX,
RayPex 5, Endo
Master and
Bingo-1020
Tri Auto ZX
Goldberg et al.[115]
In vitro
2005
Uzun et al.[79]
Ex vivo
2008
Uzun et al.[81]
In vitro
2007
Fadel et al.[74]
In vivo
2012
Jakobson et al.[73]
In vivo
2008
Felippe et al.[72]
Ex vivo
2008
Campbell et al.[75]
In vitro
1998
Goldberg et al.[67]
In vitro
2008
Topuz et al.[66]
In vitro
2008
Ebrahim et al.[65]
In vitro
2006
al Kadi et al.[116]
In vitro
2006
Azabal et al.[64]
In vitro
2004
Hoer et al.[76]
In vitro/
In vivo
2004
Oishi et al.[77]
In vitro
2002
Pratten and Mc
Donald [117]
In vitro
1996
Aim of study
Main study result
Application of apex locator
devices in root canal
retreatment
Application of apex locator
devices in root canal
retreatment
Both devices had high
accuracy in retreatment
All device were reliable,
but Dentaport ZX and
Endo Master were more
accurate
In most cases EAL was
accurate in retreatment
Application of apex locator
devices in root canal
retreatment
20 teeth
ProPex, NovApex, Application of apex locator
Third devices had high
and Root ZX
devices in root canal
accuracy in retreatment
retreatment
40 teeth
TCM Endo V and
Devices should be used
Evaluation the accuracy of
Tri Auto ZX
with caution
apex locator device along
with rotary files in root canal
length measurement in
retreatment
40 root
TCM Endo V and
Evaluation the accuracy of
These devices are
resected teeth Tri Auto ZX
apex locator device along with not appropriate for
rotary files in root canal length retreating.
measurement in retreatment
30 single root Root ZX II
Use of apex locator in
Not appropriate
premolar
controlled canal widening
24 teeth
Root ZX II
Evaluation of apex locator
EAL with rotary
ability control apical fromen
instruments was not
widening with rotary files
accurate to controlling
apical extension
67 single root Root ZX II
Use of apex locator in
Not appropriate
teeth
controlled canal widening
60 teeth
Tri Auto ZX
to examine the apical
Instrumentation with
extent of rotary canal
the automatic apical
instrumentation and the ability reverse feature set
to maintain apical constriction at 1 consistently
with the Tri Auto ZX at
approximated the apical
different automated settings constriction; however,
the constriction was
frequently enlarged
20 teeth
ProPex
Evaluation apex locatordevice All devices are reliable
NovApex
operation in diagnosis root
Root ZX
fractures
Elements
AL
40 teeth
TCM Endo V
Evaluation apex locator
Both devices identified
and Tri Auto ZX
device operation in diagnosis different root fracture in
root fractures
an acceptable range
90 teeth
Root ZX,
Evaluation apex locatordevice Device works accurately
Foramatron D10,
operation in diagnosis root
in teeth with horizontal
Apex NRG
fractures
root fractures
100 teeeth
Evaluation apex locatordevice Device works accurately
Propex and
operation in diagnosis root
in teeth with horizontal
Raypex-4
fractures
and vertical root
fractures
Justy II
Evaluation apex locatordevice Device works accurately
64 teeth
operation in diagnosis root
in teeth with horizontal
fractures
root fractures
93 root canals Justy II, Endy 5000 Evaluation apex locators
Devices cannot
ability in determination apical determine apical
constriction
constriction
ROOT ZX
Evaluation apex locators
Device
771 teeth
ability in detremination apical can determine apical
constriction
constriction
—
Apit
Evaluation apex locators
Device
ability in detremination apical can determine apical
constriction
constriction
(Continued )
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Mosleh, et al.: Electronic apex locator
Table 4: (Continued)
Authors
Publication Sample (n)
year
1991
99 canals
Types of studied
ELA
Endocater
Aim of study
Main study result
Keller et al.[118]
Type of
study
In vivo
Device was not accurate
Zmener et al.[71]
In vitro
1999
40 teeth
Tri Auto ZX
Evaluated the ability of EAL in
detecting apical constriction
and cemento dentinal junction
Detection and measurement
of endodontic root
perforations using a newly
designed
apex-locating handpiece
Kaufman et al.[70]
In vitro
1997
Fuss et al.[68]
In vitro
1996
Hulsmann et al.[69]
In vivo
1989
30 teeth with
perforation in
middle third
32 teeth with
perforation in
midle third
21 teeth
Root ZX , Sono
Explorer Mark II
Junior and Apit III
Sono Explorer
Mark 2 Junior
and Apit 2
Exact-A-Pex
The Tri Auto ZX
detected and measured
endodontic root
perforations within
a range of clinically
acceptable variations
Evaluated the ability of EALs Regardless of the
in locatin perforation
perforation size all EALs
were accurate
Evaluated the ability of EALs Both device were
in locatin perforation
accurate
EALs of the same generation. The first generation
apex locator was supplied by single frequency of
direct current in order to measurement of electrical
resistance. Pain and discomfort were often felt with
using this type of apex locator.[83] The second generation
apex locator known as impedance apex locators was
measured opposition to the flow of alternating current
or impedance.[84] The disadvantage of this generation
is that electro-conductive materials in canal affect
on its accuracy.[83] The third generation apex locator
(frequency dependent apex locators) was supplied
by two frequencies to measure the impedance in the
canal. The disadvantage of this generation sensitivity
to canal fluid and the machine needs a fully charged
battery.[85] The fourth generation apex locator measures
the impedance characteristics using more than two
frequencies.[3] The disadvantage includes needing to
perform in relatively dry or in partially dried canals.[84]
The fifth generation apex locator was developed in 2003
which measure the capacitance and resistance of the
circuit separately.[86]
Many studies compared the ability of various generations
of EALs in determining root canal length. Most of these
studies showed that EALs were accurate for canal length
measurement, within a clinically acceptable range of
± 0.5. Some studies indicated that the most recent
generation of these devices had enhanced accuracy,
better patient acceptance and greater ease of use for
dentists.[31,87,88] but other studies mentioned that some
EALs of the third generation were more accurate than
those of the fourth generation.[20,27,28]
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Evaluated the ability of EAL in Was accurate
control apical bridge formation
in the treatment of teeth with
incomplete root formation
Although most of the previous studies reported that
EALs were more accurate, compared to radiography,
some of the studies noted no significant differences
between the two methods due to small sample sizes.
However, a recent randomized, controlled clinical
trial study showed no significant differences between
these two methods.[2] To consider the advantages of
conventional radiography, such as the ability to observe
the root canal system and the canal curvature directly
and to determine the existence of peri-apical lesions, the
decision of which method to use should be different in
each case. It should be noted that EALs could decrease
the patient’s radiation exposure.[42,51]
There is controversy in the diagnosis of the horizontal
and vertical root fractures by EALs. Some studies
have reported that EALs have the capacity to diagnose
horizontal and lateral root fractures,[66,67] and others
studies have indicated that horizontal fractures and
perforation sites can be better diagnosed by EALs than
vertical fractures.[64,65] Few studies have investigated
the ability of apex locators to detect root fractures
and perforations. Due to limited information on this
subject, a general conclusion could not be achieved.
More studies are required on this subject.
The present review has some limitations. First, only
relevant articles were searched in Medline/PubMed,
Cochrane library, and Scopus, which might have
restricted the results. Second, our keywords were limited
to “Tooth apex,” “Dental instrument,” “Odontometry,”
“Electronic medical,” and “Electronic apex locator” to
focus on EALs. More prospective, randomized clinical
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Mosleh, et al.: Electronic apex locator
trials are needed to determine various conditions that
affect EALs’ accuracy.
Conclusion
The results of the present study showed that EAL
is an appropriate technique for root canal length
measurements.
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Cite this article as: Mosleh H, Khazaei S, Razavian H, Vali A, Ziaei F.
Electronic apex locator: A comprehensive literature review - Part I: Different
generations, comparison with other techniques and different usages. Dent
Hypotheses 2014;5:84-97.
Source of Support: Nil. Conflict of Interest: None declared.
Dental Hypotheses
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