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84 Dental Hypotheses Jul-Sep 2014 / Vol 5 | Issue 3

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 ZiaeiDental 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]

SyStEmatic rEviEw

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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Mosleh, et al.: Electronic apex locator

85Dental HypothesesJul-Sep 2014 / Vol 5 | Issue 3

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-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 databasesElectronic 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 EALsIn 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

Figure 1: Flow chart of selected articles





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 methodsThirty-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; AnalyticTechnology, 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 FormBottom of FormApex Locator Joypex 5 (Henan, CBD Neihuan Road, Zhengzhou, China) I-ROOT (E-Magic Finder)(S-Denti SEoul, South Korea)Raypex 5 (VDW, Munich, Germany)





Table 2: Comparison of different electronic apex locators (EALs) in working length determinationAuthors Type of

studyPublication 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



Fifth

Somma et al.[89] In vivo 2012 30 teeth Dentaport ZX, Raypex 5,ProPex II



Third andFourth

Paludo et al.[48] In vivo 2012 100 rootCanals

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



Third

Stober et al. [90] In vivo 2011 40 root canals

Raypex 5Mini Apex Locator



Fourth

Stober et al.[87] In vivo 2011 40 root canals

Root ZX and iPex Comparing operation of different apex locator devices


Third andFourth

Miletic et al.[91] In vivo 2011 48 root canals

Dentaport ZX, RomiApex A-15 and Raypex 5



Third andFourth

Silveira et al. [88] In vivo 2011 23 teeth Root ZX,Novapex



Third andFourth

deVasconcelos et al. [28]

Ex vivo 2010 38 teeth Root ZX, RomiApex D-30, and Ipex


Root ZX was more accurate

Third andFourth

Guise et al.[17] In vitro 2010 40 teeth Root ZX II, Elements AL, Precision AL


Root ZX II was more accurate

Fourth

D’Assuncao et al. [33] Ex vivo 2010 31 teeth Root ZX-II, Novapex, Mini AL


Root ZX II was more accurate

Fourth

Pascon et al. [92] In vivo 2009 831 root canals

DentaPort ZX, Raypex 5



Third andFourth

Higa et al.[13] In vitro 2009 12 teeth Justylll, Dentaport,E-Magic Finder


Justylll was more accurate

Third andFourth

Siu et al. [93] In vivo 2009 29 teeth Root ZX II, Apex NRGXFR, Mini Apex Locator



Third

Pascon et al.[25] Ex vivo 2009 60 teeth Dentaport ZX, Raypex 5 ElementsDiagnostic Unit and A L


ElementsDiagnostic Unit and A L was not accurate than others

Third andFourth

Ebrahim et al.[16] In vitro 2007 32 teeth Dentaport ZX, ProPex,Foramatron D10, Apex NRG,Apit 7


Dentaport ZX, ProPex,Foramatron D10 were more accurate

Third andFourth

D’Assuncao et al.[18] Invitro 2007 40 teeth Mini AL, Root ZX II Comparing operation of different apex locator devices


Fourth

Bernardes et al.[12] Invitro 2007 40 teeth Root ZX, Elements Diagnostic Unit and A L, RomiAPEX D-30



Third andFourth

(Continued )





Table 2: (Continued)Authors Type of




Wrbas et al.[94] In vivo 2007 20 teeth Root ZXRaypex5



Third

Stavrianos et al.[24] In vivo 2007 80 root canals

Dentaport ZX,RayPex 4



Third andFourth

Venturi et al.[26] Ex vivo 2007 60 root canals

Root ZX, Apex Finder



Third

Topuz et al.[19] In vitro 2007 47 teeth TCM Endo VRoot ZX

evaluating the accuracy of theapex-locating function of the TCM Endo V and to compare the results to these ofthe Root ZX

TCM Endo V proved to be as reliable as Root ZX but the use of thedevice to determine the working length was not easy as Root ZX

Third andFourth

Ebrahim et al.[27] Ex vivo 2006 36 teeth Root ZX, Foramatron D10, Apex NRG and Apit 7


Root ZX and Foramatron D10 were more

Third andFourth

Plotino et al.[30] Ex vivo 2006 40 teeth Root ZX, Elements Diagnostic Unit and A L,ProPex


ProPex was not accurate than others

Third andFourth

D’Assunco et al. [20] In vitro 2006 40 teeth NovapexRoot-ZX

to compare the accuracy of the Root-ZX andNovapex electronic apex locators (EALs) in locating the apical foramen

Root-ZX and Novapex areuseful and accurate devices for the apical foramen location

Third andFourth

Hor et al.[29] Ex vivo 2005 193 teeth Justy IIRaypex4


Raypex4 was more accurate

Third andFourth

Haffner et al.[95] In vivo 2005 40 teeth Root ZXEndyJusty IIEndoxLysis



Third

ElAyouti et al.[14] Ex vivo 2005 182 root canals

Raypex 4, Apex pointer, Root ZX



Third andFourth

Venturi et al.[96] Invivo 2005 64 teeth Apex Finder,Root ZX



Third

Lucena-Martin et al.[11]

In vitro 2004 20 teeth Justy II,Root ZX,NeosonoUltima EZ



Third

Hoer et al.[46] In vivo 2004 75 teeth Justy II, Endy 5000 Comparing operation of different apex locator devices


Third

Welk et al. [34] In vivo 2003 32 teeth Root ZXEndo Analyzer Model 8005



Third

De Moor et al. [21] In vitro 1999 15 single canal teeth

Apex Finder AFA Model 7005, Apex-Finder, NeosonoUltima EZ and Apit 2

The accuracy and operator dependency of four electroniccanal length measuring deviceswere compared under a set of specified conditions

Apex Finder AFA Model 7005 was the mostaccurate

Third

(Continued )





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 retreatmentSix 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].





Weiger et al. [22] In vitro 1999 41 teeth Root ZXApit

Two apex locators were compared regarding their ability to accurately locate theapical constriction in the presence of various canal fluids at different meterreadings.

In the presence of NaOCl, Root ZX provides the most accurateEWL 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 moreAccurate

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, sodiumhypochlorite, 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 accurate

Second and Third





Table 3: Comparison of electronic apex locators (EALs) and different other techniques in working length determinationAuthors Type of



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


Zand et al.[100] In vivo/ Ex vivo

2011 75 teeth Root ZX Comparison of EAL and radiography in determination of working length


Jarad et al.[36] In vivo 2011 46 teeth Raypex 5 Comparison of EAL and radiography in determination of working length


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


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 ZXJust IIElements Diagnostic

Comparison of EAL and radiography in determination of working length


Patino-Marin et al.[45]

In vivo 2011 61 root canals of primary teeth

Root ZX and ProPex



Kqiku et al.[7] Ex vivo 2011 30 teeth Root ZX Comparison of EAL and radiography in determination of working length


Vieyra et al.[38] In vivo/In vitro

2011 245 teeth (693 root canals)

Root ZX, Elements-Diagnostic, Precision ALand Raypex 5

Comparison of EAL and other methods in determination of working length


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


Cianconi et al.[37] Ex vivo 2010 101 teeth EndexProPex IIRoot ZX



Sharma and Arora[102]

In vivo/ Ex vivo

2010 100 teeth Root ZX Comparison of EAL and radiography in determination of working length


Vieyra et al.[46] In vivo 2010 160 teeth Root ZX and Elements-Diagnostic



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 withoutradiography in determination of working length


Krajczar et al.[39] In vitro 2008 70 teeth ProPex Comparison of EAL and radiography in determination of working length


Hassanien et al.[50] In vivo 2008 20 patients Root ZX Comparison of EAL and radiography in determination of working


Shanmugaraj et al.[6]

In vivo/In vitro

2007 30 teeth Foramatron-IV Comparison of EAL and other methods in determination of working length


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


(Continued )









ElAyouti et al.[41] In vitro 2002 30 teeth Root ZX Comparison of EAL and radiography in determination of working length


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


Saad et al.[103] In vivo 2000 14 teeth Root ZX Effect of apex locator combiningRoot 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 185root 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


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-Exploreraided 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


Wu et al.[109] In vivo 1992 20 single root teeth

Sono-Explorer type Y-III

Evaluated the accuracy of EAL in length measurement


Ricard et al.[110] In vivo 1991 37 teeth RCM Mark II Evaluated the accuracy of EAL in length measurement


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 matureand 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 pacemakersWilson 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




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


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


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 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

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 wasfrequently enlarged

Goldberg et al.[67] In vitro 2008 20 teeth ProPexNovApexRoot ZXElementsAL

Evaluation apex locatordevice operation in diagnosis root fractures

All devices are reliable

Topuz et al.[66] In vitro 2008 40 teeth TCM Endo Vand 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


Device works accurately in teeth with horizontal root fractures

al Kadi et al.[116] In vitro 2006 100 teeeth Propex and Raypex-4


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

Devicecan determine apical constriction

Pratten and Mc Donald [117]

In vitro 1996 — Apit Evaluation apex locators ability in detremination apical constriction

Devicecan determine apical constriction

(Continued )





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





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 designedapex-locating handpiece

The Tri Auto ZX detected and measured endodontic rootperforations 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

Was accurate





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.



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