Electronic apex locator: A comprehensive
literature review — Part I: Different generations,
comparison with other techniques and different
usages
Hamid Mosleh, Saber Khazaei
1, Hamid Razavian
2, 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
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]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]S
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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
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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
two-dimensional picture of a three-two-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
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
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
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
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
Table 1: Different generations of electrical apex locator devices and their operation base[86]Generation Operation base Device samples
First 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)
Second 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) Third Using two different frequencies at the same
time in order to measure the difference or ratio between two currents
Endex/Apit (Osada Electrica Co. Tokyo, Japan) Root ZX (J.Morita, Tokyo, Japan)
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).
Fourth Using two or more non-simultaneous continuous frequencies in order to measure the difference or ratio between two currents
Bingo1020/Raypex4 (Foroum Engineering Technologies Rishon Lezion, Israel) Raypex4 (VDW, Munich, Germany)
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) Fifth Measures the capacitance and resistance
of the circuit separately Propex II (Dentsply Maillerfer, Ballaiques, Switzerland)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)
Table 2: Comparison of different electronic apex locators (EALs) in working length determination
Authors Type of
study Publication year Sample (n) Types of studied ELA Aim of study Main study result Type of generation
Comin Chiaramonti
et al.[31] Ex vivo 2012 40 teeth Bingo 1020Propex Comparing operation of different apex
locator devices
No significant
difference Fourth Baginska et al.[32] Ex vivo 2012 40 teeth Raypex 5, Apex
D.S.P and Locapex Five Comparing operation of different apex locator devices No significant difference Fifth Somma et al.[89] In vivo 2012 30 teeth Dentaport ZX,
Raypex 5, ProPex II Comparing operation of different apex locator devices No significant
difference Third andFourth Paludo et al.[48] In vivo 2012 100 root
Canals Apex and iPex Comparing the accuracy of EALs in length measurement
There weren’t
significant
differences and both devices were accurate
Fourth
Jung et al.[15] In vitro 2011 104 teeth Root ZX,
I-Root Comparing operation of different apex locator devices
No significant
difference Third Stober et al. [90] In vivo 2011 40 root
canals Raypex 5Mini Apex Locator Comparing operation of different apex locator devices
No significant
difference Fourth Stober et al.[87] In vivo 2011 40 root
canals Root ZX and iPex Comparing operation of different apex locator devices
No significant
difference Third andFourth Miletic et al.[91] In vivo 2011 48 root
canals Dentaport ZX, RomiApex A-15 and Raypex 5
Comparing operation of different apex locator devices
No significant
difference Third andFourth Silveira et al. [88] In vivo 2011 23 teeth Root ZX,
Novapex Comparing operation of different apex locator devices
No significant
difference Third andFourth deVasconcelos
et al. [28] Ex vivo 2010 38 teeth Root ZX, RomiApex D-30, and Ipex Comparing operation of different apex
locator devices
Root ZX was more
accurate Third andFourth Guise et al.[17] In vitro 2010 40 teeth Root ZX II,
Elements AL, Precision AL
Comparing operation of different apex locator devices
Root ZX II was more accurate Fourth D’Assuncao et al. [33] Ex vivo 2010 31 teeth Root ZX-II, Novapex,
Mini AL Comparing operation of different apex locator devices
Root ZX II was more accurate Fourth Pascon et al. [92] In vivo 2009 831 root
canals DentaPort ZX, Raypex 5 Comparing operation of different apex locator devices
No significant
difference Third andFourth Higa et al.[13] In vitro 2009 12 teeth Justylll, Dentaport,
E-Magic Finder Comparing operation of different apex locator devices
Justylll was more
accurate Third andFourth Siu et al. [93] In vivo 2009 29 teeth Root ZX II, Apex
NRG XFR, Mini Apex Locator Comparing operation of different apex locator devices No significant difference Third
Pascon et al.[25] Ex vivo 2009 60 teeth Dentaport ZX,
Raypex 5 Elements Diagnostic Unit and A L
Comparing operation of different apex locator devices
Elements
Diagnostic Unit and A L was not accurate than others
Third and Fourth
Ebrahim et al.[16] In vitro 2007 32 teeth Dentaport ZX,
ProPex, Foramatron D10, Apex NRG, Apit 7 Comparing operation of different apex locator devices Dentaport ZX, ProPex, Foramatron D10 were more accurate
Third and Fourth
D’Assuncao et al.[18] Invitro 2007 40 teeth Mini AL, Root ZX II Comparing operation
of different apex locator devices
No significant
difference Fourth Bernardes et al.[12] Invitro 2007 40 teeth Root ZX, Elements
Diagnostic Unit and A L, RomiAPEX D-30 Comparing operation of different apex locator devices No significant
difference Third andFourth
Table 2: (Continued)
Authors Type of
study Publication year Sample (n) Types of studied ELA Aim of study Main study result Type of generation
Wrbas et al.[94] In vivo 2007 20 teeth Root ZX
Raypex5 Comparing operation of different apex locator devices
No significant
difference Third Stavrianos et al.[24] In vivo 2007 80 root
canals Dentaport ZX,RayPex 4 Comparing operation of different apex locator devices
No significant
difference Third andFourth
Venturi et al.[26] Ex vivo 2007 60 root
canals Root ZX, Apex Finder Comparing operation of different apex locator devices
Root ZX was more accurate Third Topuz et al.[19] In vitro 2007 47 teeth TCM Endo V
Root ZX evaluating the accuracy of the apex-locating function of the TCM Endo V and to compare the results to these of the 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
Third and Fourth
Ebrahim et al.[27] Ex vivo 2006 36 teeth Root ZX, Foramatron
D10, Apex NRG and Apit 7 Comparing operation of different apex locator devices Root ZX and Foramatron D10 were more Third and Fourth Plotino et al.[30] Ex vivo 2006 40 teeth Root ZX, Elements
Diagnostic Unit and A L,
ProPex
Comparing operation of different apex locator devices
ProPex was not
accurate than others Third andFourth
D’Assunco et al. [20] In vitro 2006 40 teeth Novapex
Root-ZX to compare the accuracy of the Root-ZX and
Novapex electronic apex locators (EALs) in locating the apical foramen
Root-ZX and Novapex are useful and accurate devices for the apical foramen location
Third and Fourth
Hor et al.[29] Ex vivo 2005 193 teeth Justy II
Raypex4 Comparing operation of different apex locator devices
Raypex4 was more
accurate Third andFourth Haffner et al.[95] In vivo 2005 40 teeth Root ZX
Endy Justy II EndoxLysis Comparing operation of different apex locator devices No significant difference Third
ElAyouti et al.[14] Ex vivo 2005 182 root
canals Raypex 4, Apex pointer, Root ZX Comparing operation of different apex locator devices
Root ZX was more
accurate Third andFourth Venturi et al.[96] Invivo 2005 64 teeth Apex Finder,
Root ZX Comparing operation of different apex locator devices
No significant
difference Third Lucena-Martin
et al.[11] In vitro 2004 20 teeth Justy II,Root ZX,
NeosonoUltima EZ Comparing operation of different apex locator devices No significant difference Third Hoer et al.[46] In vivo 2004 75 teeth Justy II, Endy 5000 Comparing operation
of different apex locator devices
No significant
difference Third Welk et al. [34] In vivo 2003 32 teeth Root ZX
Endo Analyzer Model 8005
Comparing operation of different apex locator devices
Root ZX was more accurate Third
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 The accuracy and operator dependency of four electronic
canal length measuring devices
were compared under
a set of specified
conditions
Apex Finder AFA Model 7005 was the most
accurate
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].
Use of EAL in root perforations, fractures, and
apical foramen widening
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
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 canal retreatment
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].
Table 2: (Continued)
Authors Type of
study Publication year Sample (n) Types of studied ELA Aim of study Main study result Type of generation
Weiger et al. [22] In vitro 1999 41 teeth Root ZX
Apit Two apex locators were compared regarding their ability to accurately locate the apical constriction in the presence of various
canal fluids at different
meter readings.
In the presence of NaOCl, Root ZX provides the most accurate
EWL measurements Third
Lauper et al.[97] Ex vivo 1996 130 root
canals Apit and Odontometer Evaluated the accuracy of EAL in length measurement
Apit was more
Accurate First and Third Arora et al. [47] In vivo 1995 61 root
canals ENDEX and RCM Mark II Comparison the accuracy of EALs in canal length
measurement in present of different contents(vital pulp, necrotic pulp, pus/ exudates, sodium hypochlorite, and water)
ENDEX was higher accuracy than the RCM Mark II
Third
Pallares and Faus [98]Ex vivo 1994 116 root
canals Odontometer and Endo Cater Compared the accuracy of EAL in length measurement
Endo Cater was higher accuracy than the Odontometer
First and Second Nahmias et al. [23] In vitro 1987 60 single
root teeth Sono-Explorer,C. L. Meter and Neosono-D
Compared the accuracy of EAL in length measurement
All EALs were
Table 3: Comparison of electronic apex locators (EALs) and different other techniques in working length determination
Authors Type of
study Publication year Sample (n) Types of studied ELA Aim of study Main study result
Orosco et al.[60] In vivo 2012 25 teeth Root ZX Comparison of EAL and radiography
in determination of working length Conventional and EAL were comparable and better than digital Kishor[99] In vitro 2012 35 teeth Foramatron D10 Comparison of EAL and radiography,
radiovisography in determination of working length
EAL are more accurate
Chougule et al.[58] In vivo 2012 13 primary teeth Dentaport ZX Comparison of EAL and radiography
in determination of working length EAL are more accurate Zand et al.[100] In vivo/
Ex vivo 2011 75 teeth Root ZX Comparison of EAL and radiography in determination of working length No significant difference Jarad et al.[36] In vivo 2011 46 teeth Raypex 5 Comparison of EAL and radiography
in determination of working length No significant difference Parekh and
Taluja[101] Ex vivo 2011 20 patients Root ZX Comparison of EAL and radiography in determination of working length Radiography and EAL can be used together Janner et al.[63] In vivo 2011 3 patients Root ZX Compared CBCT method to EAL Two methods were
comparable Neena et al.[54] In vivo 2011 30 teeth — Comparison of EAL and
radiography in determination of working length
No significant difference
Singh et al.[57] In vivo 2011 20 teeth Propex II Comparison of EAL and radiography
in determination of working length EALs are more accurate Real et al.[51] In vitro 2011 37 root canals Root ZX
Just II Elements Diagnostic
Comparison of EAL and radiography
in determination of working length EALs are more accurate
Patino-Marin
et al.[45] In vivo 2011 61 root canals of primary teeth Root ZX and ProPex Comparison of EAL and radiography in determination of working length EALs are more accurate
Kqiku et al.[7] Ex vivo 2011 30 teeth Root ZX Comparison of EAL and radiography
in determination of working length No significant difference Vieyra et al.[38] In vivo/In
vitro 2011 245 teeth (693 root canals) Root ZX, Elements-Diagnostic, Precision AL and Raypex 5
Comparison of EAL and other methods in determination of working length
EALs are more accurate
Mancini et al.[44] Ex vivo 2011 120 teeth Endex, Propexll
and Root ZX Comparison of EAL and other methods in determination of working length
EALs are more accurate
Cianconi et al.[37] Ex vivo 2010 101 teeth Endex
ProPex II Root ZX
Comparison of EAL and radiography
in determination of working length EALs are more accurate Sharma and
Arora[102] In vivoEx vivo/ 2010 100 teeth Root ZX Comparison of EAL and radiography in determination of working length EALs are more accurate
Vieyra et al.[46] In vivo 2010 160 teeth Root ZX and
Elements-Diagnostic
Comparison of EAL and radiography
in determination of working length EALs are more accurate Javidi et al.[40] In vitro 2009 30 teeth Root ZX Comparison of EAL and radiography
in determination of working length Radiography and EAL can be used together Kim et al.[43] In vivo 2008 25 teeth Root ZX Evaluating EAL with or without
radiography in determination of working length
No significant difference
Krajczar et al.[39] In vitro 2008 70 teeth ProPex Comparison of EAL and radiography
in determination of working length EAL are more accurate Hassanien et al.[50]In vivo 2008 20 patients Root ZX Comparison of EAL and radiography
in determination of working EAL are more accurate Shanmugaraj
et al.[6] In vivovitro /In 2007 30 teeth Foramatron-IV Comparison of EAL and other methods in determination of working
length
EAL are more accurate
Smadi et al.[51] In vivo 2006 151 root canals Tri Auto ZX Comparison of EAL and radiography
in determination of working length Use of EAL could reduce need for additional radiography
Subramaniam
et al.[62] In vitro 2005 20 teeth Formatron D10 Comparison of EAL and other methods in determination of working
length
No significant difference
Table 3: (Continued)
Authors Type of
study Publication year Sample (n) Types of studied ELA Aim of study Main study result
ElAyouti et al.[41] In vitro 2002 30 teeth Root ZX Comparison of EAL and radiography
in determination of working length EAL are more accurate Brunton et al.[42] In vitro 2002 50 teeth - Effect of apex locator on reduction
X-ray exposure Use of EAL reduced patients X-ray exposure Martinez-Lozano
et al.[35] In vitro 2001 70 teeth Apit EM-S3 Comparison of EAL and radiography in determination of
working length
No significant difference
Saad et al.[103] In vivo 2000 14 teeth Root ZX Effect of apex locator combining
Root ZX and a digital imaging system (RadioVisioGraphy]on reduction X-ray exposure
This technique was useful
Ounsi et al.[61] In vitro 1998 37 teeth Endex Comparison of EAL and
radiography, tactile sense method in determination of working length
Tactile sense method was inaccurate, but other two methods were same accurate
Himel et al.[55] In vivo 1993 96 root canals Formatron IV Comparing the accuracy of EALs
and radiography method in length measurement
EALs weren’t accurate
Hembrough
et al.[49] In vivo 1993 26 maxillary molar teeth Sono-Explorer Mark III Compared the accuracy of EAL and radiography method in length
measurement
EAL is useful only combined with
radiography and couldn’t replace it
Frank et al.[56] In vivo 1993 185
root canal Endex Compared EAL with radiography method in length measurement EAL was comparable with radiography method Trope et al.[59] In vivo 1985 127 root canals Sono-Explorer
Mark III Comparison of EAL and radiography in determination of working length EAL wasn’t accuracy same as radiography Murakami et al.[104]In vivo 2002 66 infected
canals Sono-Explorer To retrospectively assess the success of endodontic treatment that had been guided by audiometric (electronic) measurement.
Use of the Sono-Explorer aided successful treatment of infected root canals
Stavrianos
et al.[105] In vivo 2007 85 teeth Raypex 5 Evaluated the accuracy of EAL in length measurement EAL was accurate
Ounsi et al.[106] In vitro 1999 39single root
teeth Root ZX Evaluated the accuracy of EAL in length measurement Root ZX couldn’t detect apical constriction and should only use to detecting major foramen Vajrabhaya
et al.[107] In vivo 1997 20Single root teeth Root ZX Evaluated the accuracy of EAL in length measurement In clinical acceptable range its accurate
Shabahang
et al.[108]
In vivo 1996 26 root canals Root ZX Evaluated the accuracy of EAL in
length measurement In clinical acceptable range its accurate Wu et al.[109] In vivo 1992 20 single root
teeth Sono-Explorer type Y-III Evaluated the accuracy of EAL in length measurement In clinical acceptable range its accurate Ricard et al.[110] In vivo 1991 37 teeth RCM Mark II Evaluated the accuracy of EAL in
length measurement In clinical acceptable range its accurate McDonald et al.[111]In vivo 1990 47 teeth Endocater Evaluated the accuracy of EAL in
detecting apical constriction It was accurate Berman et al.[112] In vivo 1984 24 mature
and 5 immature root canals
Neosono-D Evaluated the accuracy of EAL in
length measurement EAL only in mature canal was accurate Busch et al.[113] In vitro 1976 77 teeth (46 vital
and 26 necrotic) Sono-Explorer Evaluated the accuracy of EAL in length measurement EAL was accurate in both groups
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.
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
Table 4: Other usage of electronic apex locators (EALs)
Authors Type of
study Publication year Sample (n) Types of studied ELA Aim of study Main study result
Aggarwal et al.[80] In vitro 2010 60 teeth Root ZX and
ProPex Application of apex locator devices in root canal retreatment
Both devices had high accuracy in retreatment Stavrianos et al.[114] In vitro 2008 40 teeth Dentaport ZX,
RayPex 5, Endo Master and Bingo-1020
Application of apex locator devices in root canal retreatment
All device were reliable, but Dentaport ZX and Endo Master were more accurate
Alves et al.[78] Ex vivo 2005 62 teeth Tri Auto ZX Application of apex locator
devices in root canal retreatment
In most cases EAL was accurate in retreatment Goldberg et al.[115] In vitro 2005 20 teeth ProPex, NovApex,
and Root ZX Application of apex locator devices in root canal retreatment
Third devices had high accuracy in retreatment Uzun et al.[79] Ex vivo 2008 40 teeth TCM Endo V and
Tri Auto ZX Evaluation the accuracy of apex locator device along
with rotary files in root canal
length measurement in retreatment
Devices should be used with caution
Uzun et al.[81] In vitro 2007 40 root
resected teethTCM Endo V and Tri Auto ZX Evaluation the accuracy of apex locator device along with
rotary files in root canal length
measurement in retreatment
These devices are not appropriate for retreating. Fadel et al.[74] In vivo 2012 30 single root
premolar Root ZX II Use of apex locator in controlled canal widening Not appropriate Jakobson et al.[73] In vivo 2008 24 teeth Root ZX II Evaluation of apex locator
ability control apical fromen
widening with rotary files
EAL with rotary instruments was not accurate to controlling apical extension Felippe et al.[72] Ex vivo 2008 67 single root
teeth Root ZX II Use of apex locator in controlled canal widening Not appropriate Campbell et al.[75] In vitro 1998 60 teeth Tri Auto ZX to examine the apical
extent of rotary canal instrumentation and the ability to maintain apical constriction with the Tri Auto ZX at different automated settings
Instrumentation with the automatic apical reverse feature set at 1 consistently approximated the apical constriction; however, the constriction was frequently enlarged Goldberg et al.[67] In vitro 2008 20 teeth ProPex
NovApex Root ZX Elements AL
Evaluation apex locatordevice operation in diagnosis root fractures
All devices are reliable
Topuz et al.[66] In vitro 2008 40 teeth TCM Endo V
and Tri Auto ZX Evaluation apex locator device operation in diagnosis root fractures
Both devices identified
different root fracture in an acceptable range Ebrahim et al.[65] In vitro 2006 90 teeth Root ZX,
Foramatron D10, Apex NRG
Evaluation apex locatordevice operation in diagnosis root fractures
Device works accurately in teeth with horizontal root fractures
al Kadi et al.[116] In vitro 2006 100 teeeth Propex and
Raypex-4 Evaluation apex locatordevice operation in diagnosis root fractures
Device works accurately in teeth with horizontal and vertical root fractures Azabal et al.[64] In vitro 2004 64 teeth Justy II Evaluation apex locatordevice
operation in diagnosis root fractures
Device works accurately in teeth with horizontal root fractures
Hoer et al.[76] In vitro/
In vivo 2004 93 root canals Justy II, Endy 5000 Evaluation apex locators ability in determination apical constriction
Devices cannot determine apical constriction Oishi et al.[77] In vitro 2002 771 teeth ROOT ZX Evaluation apex locators
ability in detremination apical constriction
Device
can determine apical constriction
Pratten and Mc
Donald [117] In vitro 1996 — Apit Evaluation apex locators ability in detremination apical
constriction
Device
can determine apical constriction
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]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
Table 4: (Continued)Authors Type of
study Publication year Sample (n) Types of studied ELA Aim of study Main study result
Keller et al.[118] In vivo 1991 99 canals Endocater Evaluated the ability of EAL in
detecting apical constriction and cemento dentinal junction
Device was not accurate
Zmener et al.[71] In vitro 1999 40 teeth Tri Auto ZX Detection and measurement
of endodontic root perforations using a newly designed
apex-locating handpiece
The Tri Auto ZX detected and measured endodontic root perforations within a range of clinically acceptable variations Kaufman et al.[70] In vitro 1997 30 teeth with
perforation in middle third
Root ZX , Sono Explorer Mark II Junior and Apit III
Evaluated the ability of EALs
in locatin perforation Regardless of the perforation size all EALs were accurate
Fuss et al.[68] In vitro 1996 32 teeth with
perforation in midle third
Sono Explorer Mark 2 Junior and Apit 2
Evaluated the ability of EALs
in locatin perforation Both device were accurate Hulsmann et al.[69] In vivo 1989 21 teeth Exact-A-Pex Evaluated the ability of EAL in
control apical bridge formation in the treatment of teeth with incomplete root formation
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.
