Electronic apex locator: A comprehensive literature review Part I: Different generations, comparison with other techniques and different usages

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1 Systematic Review 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, 2 Department of Endodontics, Torabinejad Dental Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, 1 Department of Research, School of Dentistry, Kermanshah University of Medical Sciences, Kermanshah, Iran ABSTRACT 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 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 s 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 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. [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] Quick Response Code: Access this article online Website: DOI: / 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 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 , Iran. razavian@dnt.mui.ac.ir 84 Dental Hypotheses Jul-Sep 2014 / Vol 5 Issue 3

2 techniques can be in 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 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 s between various devices [12,13,16,19] [Table 2]. All of the ex vivo studies showed significant s 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 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 Figure 1: Flow chart of selected articles Jul-Sep 2014 / Vol 5 Issue 3 Dental Hypotheses 85

3 Table 1: Different generations of electrical apex 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) Fifth Using two different frequencies at the same time in order to measure the or ratio between two currents Using two or more non-simultaneous continuous frequencies in order to measure the or ratio between two currents Measures the capacitance and resistance of the circuit separately 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). 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) 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) Raypex 5 (VDW, Munich, Germany) in vivo studies, Welk et al. [34] and Arora et al. [47] found a significant 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 s, [7,35,36,43,53,54] three studies concluded that radiography method was more, [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 [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 86 Dental Hypotheses Jul-Sep 2014 / Vol 5 Issue 3

4 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 Comin Chiaramonti Ex vivo teeth Bingo 1020 et al. [31] Propex Baginska et al. [32] Ex vivo teeth Raypex 5, Apex D.S.P and Locapex Five Somma et al. [89] In vivo teeth Dentaport ZX, Raypex 5, ProPex II Paludo et al. [48] In vivo root Apex and ipex Canals Jung et al. [15] In vitro teeth Root ZX, I-Root Stober et al. [90] In vivo root Stober et al. [87] In vivo root Miletic et al.[91] In vivo root Raypex 5 Mini Apex Locator Root ZX and ipex Silveira et al. [88] In vivo teeth Root ZX, Novapex devasconcelos Ex vivo teeth Root ZX, RomiApex et al. [28] D-30, and Ipex Guise et al. [17] In vitro teeth Root ZX II, Elements AL, Precision AL Aim of study Main study result Type of generation Comparing the accuracy of EALs in Dentaport ZX, RomiApex A-15 and Raypex 5 D Assuncao et al. [33] Ex vivo teeth Root ZX-II, Novapex, Mini AL Pascon et al. [92] In vivo root DentaPort ZX, Raypex 5 Higa et al. [13] In vitro teeth Justylll, Dentaport, E-Magic Finder Siu et al. [93] In vivo teeth Root ZX II, Apex NRG XFR, Mini Apex Locator Pascon et al. [25] Ex vivo teeth Dentaport ZX, Raypex 5 Elements Diagnostic Unit and A L Ebrahim et al. [16] In vitro teeth Dentaport ZX, ProPex, Foramatron D10, Apex NRG, Apit 7 D Assuncao et al. [18] Invitro teeth Mini AL, Root ZX II Bernardes et al. [12] Invitro teeth Root ZX, Elements Diagnostic Unit and A L, RomiAPEX D-30 There weren t significant s and both devices were Root ZX was more Root ZX II was more Root ZX II was more Justylll was more Fifth Elements Diagnostic Unit and A L was not than others Dentaport ZX, ProPex, Foramatron D10 were more (Continued ) Jul-Sep 2014 / Vol 5 Issue 3 Dental Hypotheses 87

5 Table 2: (Continued) Authors Type of study Publication year Sample (n) Types of studied ELA Wrbas et al. [94] In vivo teeth Root ZX Raypex5 Stavrianos et al. [24] In vivo root Venturi et al. [26] Ex vivo root Dentaport ZX,RayPex 4 Root ZX, Apex Finder Topuz et al. [19] In vitro teeth TCM Endo V Root ZX Ebrahim et al. [27] Ex vivo teeth Root ZX, Foramatron D10, Apex NRG and Apit 7 Plotino et al. [30] Ex vivo teeth Root ZX, Elements Diagnostic Unit and A L, ProPex D Assunco et al. [20] In vitro teeth Novapex Root-ZX Hor et al. [29] Ex vivo teeth Justy II Raypex4 Haffner et al. [95] In vivo teeth Root ZX Endy Justy II EndoxLysis ElAyouti et al. [14] Ex vivo root Raypex 4, Apex pointer, Root ZX Venturi et al. [96] Invivo teeth Apex Finder, Root ZX Aim of study Main study result Type of generation evaluating the accuracy of the apex-locating function of the TCM Endo V and to compare the results to these of the Root ZX to compare the accuracy of the Root- ZX and Novapex electronic apex locators (EALs) in locating the apical foramen Lucena-Martin et al. [11] In vitro teeth Justy II, Root ZX, NeosonoUltima EZ Hoer et al. [46] In vivo teeth Justy II, Endy 5000 Welk et al. [34] In vivo teeth Root ZX Endo Analyzer Model 8005 De Moor et al. [21] In vitro single canal teeth Apex Finder AFA Model 7005, Apex-Finder, Neosono Ultima EZ and Apit 2 Comparing operation of different apex locator devices The accuracy and operator dependency of four electronic canal length measuring devices were compared under a set of specified conditions Root ZX was more 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 than others 88 Dental Hypotheses Jul-Sep 2014 / Vol 5 Issue 3 Root-ZX and Novapex are useful and devices for the apical foramen location Raypex4 was more Root ZX was more Root ZX was more Apex Finder AFA Model 7005 was the most (Continued )

6 Table 2: (Continued) Authors Type of study Publication year Sample (n) Weiger et al. [22] In vitro teeth Root ZX Apit Lauper et al. [97] Ex vivo root Arora et al. [47] In vivo root Pallares and Faus [98] Ex vivo root Nahmias et al. [23] In vitro single root teeth Types of studied ELA Apit and Odontometer ENDEX and RCM Mark II Odontometer and Endo Cater Sono-Explorer, C. L. Meter and Neosono-D Aim of study Main study result Type of generation Two apex locators were compared regarding their ability to ly locate the apical constriction in the presence of various canal fluids at different meter readings. Evaluated the accuracy of EAL in length measurement Comparison the accuracy of EALs in canal length measurement in present of different contents(vital pulp, necrotic pulp, pus/ exudates, sodium hypochlorite, and water) Compared the accuracy of EAL in Compared the accuracy of EAL in In the presence of NaOCl, Root ZX provides the most EWL measurements Apit was more Accurate ENDEX was higher accuracy than the RCM Mark II First and Endo Cater was First and higher accuracy than Second the Odontometer All EALs were Second and same accuracy and significantly were more than tactile method. In the study by Subramaniam et al. [62], there were no significant s 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 in horizontal fracture diagnosis [64,65] although Topez et al. [66] reported that EALs were 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 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 that were prepared with rotary instruments was not sufficiently 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 ). 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 [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 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 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 s 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]. Jul-Sep 2014 / Vol 5 Issue 3 Dental Hypotheses 89

7 Table 3: Comparison of electronic apex locators (EALs) and different other techniques in working length determination Authors Type of study Publication Sample (n) year Types of studied ELA Aim of study Orosco et al. [60] In vivo teeth Root ZX Comparison of EAL and radiography Main study result Conventional and EAL were comparable and better than digital of Kishor [99] In vitro teeth Foramatron D10 Comparison of EAL and radiography, EAL are more radiovisography in determination of working length Chougule et al. [58] In vivo primary teeth Dentaport ZX Comparison of EAL and radiography EAL are more Zand et al. [100] In vivo/ teeth Root ZX Comparison of EAL and radiography Ex vivo Jarad et al. [36] In vivo teeth Raypex 5 Comparison of EAL and radiography Parekh and Ex vivo patients Root ZX Comparison of EAL and radiography Radiography and EAL Taluja[101] can be used together Janner et al. [63] In vivo patients Root ZX Compared CBCT method to EAL Two methods were comparable Neena et al. [54] In vivo teeth Comparison of EAL and radiography in determination of working length Singh et al. [57] In vivo teeth Propex II Comparison of EAL and radiography EALs are more Real et al. [51] In vitro root Root ZX Comparison of EAL and radiography EALs are more Just II Elements Diagnostic Patino-Marin In vivo root Root ZX and Comparison of EAL and radiography EALs are more et al. [45] primary teeth ProPex Kqiku et al. [7] Ex vivo teeth Root ZX Comparison of EAL and radiography Vieyra et al. [38] In vivo/in vitro teeth (693 root ) Root ZX, Elements- Diagnostic, Precision AL and Raypex 5 Mancini et al. [44] Ex vivo teeth Endex, Propexll and Root ZX Cianconi et al. [37] Ex vivo teeth Endex ProPex II Root ZX Sharma and In vivo/ Arora [102] Ex vivo Vieyra et al. [46] In vivo teeth Root ZX and Elements- Diagnostic Comparison of EAL and other methods in determination of working length Comparison of EAL and other methods in determination of working length Comparison of EAL and radiography EALs are more EALs are more EALs are more teeth Root ZX Comparison of EAL and radiography EALs are more Comparison of EAL and radiography EALs are more Javidi et al. [40] In vitro teeth Root ZX Comparison of EAL and radiography Radiography and EAL can be used together Kim et al. [43] In vivo teeth Root ZX Evaluating EAL with or without radiography in determination of working length Krajczar et al. [39] In vitro teeth ProPex Comparison of EAL and radiography EAL are more Hassanien et al. [50] In vivo patients Root ZX Comparison of EAL and radiography EAL are more in determination of working Shanmugaraj et al. [6] In vivo/in vitro teeth Foramatron-IV Comparison of EAL and other methods in determination of working length Smadi et al. [51] In vivo root Tri Auto ZX Comparison of EAL and radiography Subramaniam In vitro teeth Formatron D10 Comparison of EAL and other et al. [62] methods in determination of working length EAL are more Use of EAL could reduce need for additional radiography (Continued ) 90 Dental Hypotheses Jul-Sep 2014 / Vol 5 Issue 3

8 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 teeth Root ZX Comparison of EAL and radiography EAL are more Brunton et al. [42] In vitro teeth - Effect of apex locator on reduction X-ray exposure Use of EAL reduced patients X-ray exposure Martinez-Lozano In vitro teeth Apit EM-S3 Comparison of EAL and et al. [35] radiography in determination of working length Saad et al. [103] In vivo 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 teeth Endex Comparison of EAL and radiography, tactile sense method in determination of working length Himel et al. [55] In vivo root Formatron IV Comparing the accuracy of EALs and radiography method in length measurement Hembrough In vivo maxillary et al. [49] molar teeth Frank et al. [56] In vivo root canal Sono-Explorer Mark III Endex Trope et al. [59] In vivo root Sono-Explorer Mark III Murakami et al. [104] In vivo infected Sono-Explorer Compared the accuracy of EAL and radiography method in length measurement Compared EAL with radiography method in Tactile sense method was in, but other two methods were same EALs weren t EAL is useful only combined with radiography and couldn t replace it EAL was comparable with radiography method Comparison of EAL and radiography EAL wasn t accuracy same as radiography To retrospectively assess the Use of the Sonosuccess of endodontic treatment Explorer that had been guided by audiometric aided successful (electronic) measurement. treatment of infected root EAL was Stavrianos et al. [105] In vivo teeth Raypex 5 Evaluated the accuracy of EAL in Ounsi et al. [106] In vitro single root Root ZX Evaluated the accuracy of EAL in teeth In vivo Vajrabhaya Root ZX Evaluated the accuracy of EAL in et al. [107] Single root teeth Shabahang In vivo root Root ZX Evaluated the accuracy of EAL in et al. [108] Wu et al. [109] In vivo single root Sono-Explorer Evaluated the accuracy of EAL in teeth type Y-III Ricard et al. [110] In vivo teeth RCM Mark II Evaluated the accuracy of EAL in McDonald et al. [111] In vivo teeth Endocater Evaluated the accuracy of EAL in detecting apical constriction Berman et al. [112] In vivo mature Neosono-D Evaluated the accuracy of EAL in and 5 immature root Busch et al. [113] In vitro teeth (46 vital and 26 necrotic) Sono-Explorer Evaluated the accuracy of EAL in Root ZX couldn t detect apical constriction and should only use to detecting major foramen In clinical acceptable range its In clinical acceptable range its In clinical acceptable range its In clinical acceptable range its It was EAL only in mature canal was EAL was 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 s between different Jul-Sep 2014 / Vol 5 Issue 3 Dental Hypotheses 91

9 Table 4: Other usage of electronic apex locators (EALs) Authors Type of study Publication year Sample (n) Types of studied ELA Aggarwal et al. [80] In vitro teeth Root ZX and ProPex Stavrianos et al. [114] In vitro teeth Dentaport ZX, RayPex 5, Endo Master and Bingo-1020 Aim of study Application of apex locator devices in root canal retreatment Application of apex locator devices in root canal retreatment Alves et al. [78] Ex vivo teeth Tri Auto ZX Application of apex locator devices in root canal retreatment Goldberg et al. [115] In vitro teeth ProPex, NovApex, and Root ZX Uzun et al. [79] Ex vivo teeth TCM Endo V and Tri Auto ZX Uzun et al. [81] In vitro root TCM Endo V and resected teeth Tri Auto ZX Application of apex locator devices in root canal retreatment Evaluation the accuracy of apex locator device along with rotary files in root canal in retreatment Evaluation the accuracy of Fadel et al. [74] In vivo single root Root ZX II premolar Jakobson et al. [73] In vivo teeth Root ZX II Evaluation of apex locator ability control apical fromen widening with rotary files Main study result Both devices had high accuracy in retreatment All device were reliable, but Dentaport ZX and Endo Master were more In most cases EAL was in retreatment devices had high accuracy in retreatment Devices should be used with caution These devices are apex locator device along with not appropriate for rotary files in root canal length retreating. measurement in retreatment Use of apex locator in Not appropriate controlled canal widening EAL with rotary instruments was not to controlling apical extension Felippe et al. [72] Ex vivo single root Root ZX II Use of apex locator in Not appropriate teeth controlled canal widening Campbell et al. [75] In vitro teeth Tri Auto ZX to examine the apical extent of rotary canal Instrumentation with the automatic apical instrumentation and the ability reverse feature set to maintain apical constriction at 1 consistently with the Tri Auto ZX at different automated settings approximated the apical constriction; however, the constriction was frequently enlarged Goldberg et al. [67] In vitro teeth ProPex NovApex Root ZX Elements AL Topuz et al. [66] In vitro teeth TCM Endo V and Tri Auto ZX Ebrahim et al. [65] In vitro teeth Root ZX, Foramatron D10, Apex NRG al Kadi et al. [116] In vitro teeeth Propex and Raypex-4 Evaluation apex locatordevice operation in diagnosis root fractures All devices are reliable Evaluation apex locator Both devices identified device operation in diagnosis different root fracture in root fractures an acceptable range Evaluation apex locatordevice Device works ly operation in diagnosis root in teeth with horizontal fractures root fractures Evaluation apex locatordevice operation in diagnosis root fractures Device works ly in teeth with horizontal and vertical root fractures Azabal et al. [64] In vitro teeth Justy II Evaluation apex locatordevice Device works ly operation in diagnosis root fractures in teeth with horizontal root fractures Hoer et al. [76] In vitro/ In vivo root Justy II, Endy 5000 Evaluation apex locators ability in determination apical constriction Oishi et al. [77] In vitro teeth ROOT ZX Evaluation apex locators ability in detremination apical constriction Pratten and Mc In vitro 1996 Apit Evaluation apex locators Donald [117] ability in detremination apical constriction Devices cannot determine apical constriction Device can determine apical constriction Device can determine apical constriction (Continued ) 92 Dental Hypotheses Jul-Sep 2014 / Vol 5 Issue 3

10 Table 4: (Continued) Authors Type of study Publication year Sample (n) Types of studied ELA Aim of study Keller et al. [118] In vivo Endocater Evaluated the ability of EAL in detecting apical constriction and cemento dentinal junction Zmener et al. [71] In vitro teeth Tri Auto ZX Detection and measurement of endodontic root perforations using a newly designed apex-locating handpiece Kaufman et al. [70] In vitro teeth with perforation in middle third Fuss et al. [68] In vitro teeth with perforation in midle third Root ZX, Sono Explorer Mark II Junior and Apit III Sono Explorer Mark 2 Junior and Apit 2 Evaluated the ability of EALs in locatin perforation Evaluated the ability of EALs in locatin perforation Main study result Device was not The Tri Auto ZX detected and measured endodontic root perforations within a range of clinically acceptable variations Regardless of the perforation size all EALs were Both device were Hulsmann et al. [69] In vivo teeth Exact-A-Pex Evaluated the ability of EAL in Was control apical bridge formation in the treatment of teeth with incomplete root formation 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. [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 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 than those of the fourth generation. [20,27,28] Although most of the previous studies reported that EALs were more, compared to radiography, some of the studies noted no significant s between the two methods due to small sample sizes. However, a recent randomized, controlled clinical trial study showed no significant s 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 Jul-Sep 2014 / Vol 5 Issue 3 Dental Hypotheses 93

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14 114. Stavrianos CH, Vladimirov ST, Vasiliadis L, Stavrianou I, Panayotov I, Pamporakis P. In vitro evaluation of the precision of four different electronic apex locators in determining the working length of teeth after removing root canal obturation materials. Res J Med Sci 2008;2: Goldberg F, Marroquín BB, Frajlich S, Dreyer C. In vitro evaluation of the ability of three apex locators to determine the working length during retreatment. J Endod 2005; 31: al Kadi H, Sykes LM, Vally Z. Accuracy of the Raypex-4 and Propex apex locators in detecting horizontal and vertical root fractures: An in vitro study. SADJ 2006;61: Pratten DH, McDonald NJ. Comparison of radiographic and electronic working lengths. J Endod 1996;22: Keller ME, Brown CE Jr, Newton CW. A clinical evaluation of the Endocater an electronic apex locator. J Endod 1991;17: 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: Source of Support: Nil. Conflict of Interest: None declared. Jul-Sep 2014 / Vol 5 Issue 3 Dental Hypotheses 97