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ORIGINAL ARTICLE
Year : 2015  |  Volume : 5  |  Issue : 3  |  Page : 177-181

In vitro evaluation of the accuracy of five different electronic apex locators


1 Endodontist, Department of Dentistry, Kerala Institute of Medical Sciences, Thiruvananthapuram, Kerala, India
2 Department of Conservative Dentistry and Endodontics, Nehru Smaraka Vidya Kendra Sri Venkateshwara Dental College and Hospital, Bangalore, India
3 Department of Conservative Dentistry and Endodontics, Rajarajeswari Dental College and Hospital, Bangalore, Karnataka, India
4 Department of Conservative Dentistry and Endodontics, Annoor Dental College, Moovattupuzha, Kerala, India

Date of Web Publication26-Aug-2015

Correspondence Address:
Nasil Sakkir
TC 2/453(22), Aisha Cottage, P.T Chacko Nagar, Medical College, P.O, Thiruvananthapuram - 695 011, Kerala
India
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Source of Support: Nil., Conflict of Interest: None


DOI: 10.4103/1658-5984.163622

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  Abstract 


Objective of Study: To evaluate in vitro the efficacy of five different electronic apex locators (Root ZX II, i-Root, Endo Master, Triauto ZX, and Elements apex locator) in locating the minor diameter.
Materials and Methods: Thirty freshly extracted single-rooted maxillary central incisors were used for the study. Standard access preparation was carried out and the teeth were glued to three plastic frames containing alginate. Electronic working length measurement was determined using all the five apex locators. Following this, the actual canal length was determined by introducing a size 15 K-file into the canal until the tip of the file became visible at the apical foramen under microscope. The mean values of actual length and electronic working length readings were compared using Student t-test and multiple comparison procedures.
Results: The average value for actual root canal length was 22.483 ± 1.8731 mm; and the mean electronic root canal length values for Root ZX II, i-Root, Elements, Endo Master, and Triauto ZX apex locators was 22.483 ± 1.7640 mm, 22.400 ± 1.7390 mm, 22.717 ± 1.9462 mm, 22.767 ± 1.9061 mm, and 22.417 ± 1.7523 mm, respectively. P > 0.05 for all the five tested apex locators.
Conclusion: All the five modern apex locators tested in this study can determine the working length with high precision and greater predictability.

Keywords: Electronic apex locators, minor apical foramen, working length determination


How to cite this article:
Sakkir N, Asifulla M, Chandra V, Idris M, Razvi SF, Geeta I B. In vitro evaluation of the accuracy of five different electronic apex locators. Saudi Endod J 2015;5:177-81

How to cite this URL:
Sakkir N, Asifulla M, Chandra V, Idris M, Razvi SF, Geeta I B. In vitro evaluation of the accuracy of five different electronic apex locators. Saudi Endod J [serial online] 2015 [cited 2020 Aug 8];5:177-81. Available from: http://www.saudiendodj.com/text.asp?2015/5/3/177/163622




  Introduction Top


Success of endodontic treatment depends on the diagnosis, treatment planning, access cavity preparation followed by cleaning and shaping and obturation. It is generally accepted that root canal treatment procedures should be limited to within the root canal system.[1] To attain this objective, the end point of the root canal system, the canal terminus, should be detected as precisely as possible during preparation of the root canal.[2] Theoretically, the Cemento-Dentinal Junction (CDJ) is the appropriate apical limit for root canal treatment as at this level the area of contact between the periradicular tissues and root canal filling material is likely to be minimal and the wound smallest.[1] The term "theoretically" is applied here because the CDJ is a histological landmark and in clinical situation it is impossible to identify its position. Therefore, CDJ is not an ideal landmark as the end-point for root canal preparation and filling. In clinical practice, the apical constriction is a more consistent anatomical feature that can be regarded as being the narrowest portion of the canal system and thus the preferred landmark for the apical end-point for root canal treatment.[2],[3] Although it is generally accepted that the apical constriction is on average located 0.5-1.0 mm short of the radiographic apex,[2] there are wide variations in the relationship of these landmarks. Thus, it is nearly impossible to radiographically determine the correct working length.[2],[3],[4],[5]

An electronic method for root length determination wasfirst investigated by Custer.[6] He found that the electrical conductivity of the tissues surrounding the apex of the root is greater than the conductivity inside the root canal system, coronal to the canal terminus. Subsequently, Suzuki[7] in his experimental study on iontophoresis in dog's teeth indicated that the electrical resistance between a root canal instrument inserted into a canal and an electrode applied to the oral mucous membrane registered consistent values. Based on Suzuki's finding, Sunada[8] determined that when the tip of an endodontic instrument had reached the periodontal membrane through the "apical foramen," the electrical resistance between the instrument and the oral mucous membrane was approximately equal to 6.5 KΩ.

The development of modern electronic apex locators (EAL) has helped make non-radiographic measurement of root canal length more accurate and reliable.[9] To use these devices, a coronal glide path is established, then a hand file is introduced into the root and stopped at the level dictated by the device. This distance, called working length, is carefully measured by means of a rubber stop placed on the file and transferred to a sequence of instruments to be used for preparation. More recently, devices have been introduced that integrate an electronic apex locator with an endodontic handpiece for canal preparation. These apex locator-controlled handpieces eliminate the need to maintain working length with multiple files by stopping the rotation of the nickel-titanium (NiTi) files as the point estimated to be the end of the root canal is reached. These devices can be used either as regular apex locators (with subsequent manual hand files) or for operating rotary NiTi files using the motor-controlled mode.[10] In the current study, an in vitro model was used to test the efficacy of five different apex locators-Root ZX II (J. Morita Corp., Tokyo, Japan), i-Root (S-Denti, Seoul, Korea), Elements Apex locator (Sybron Endo, Glendora, CA, USA), Endo Master (EMS, Nyon, Switzerland), and Triauto ZX Apex locator (J. Morita Corp., Tokyo, Japan) in locating the minor diameter.


  Materials and Methods Top


An in vitro study was undertaken in the Department of Conservative Dentistry and Endodontics, to evaluate the efficacy of different generation electronic apex locators.

Preparation of samples

Thirty freshly extracted single rooted maxillary central incisors were collected from the outpatient clinic of Department of Oral and Maxillofacial Surgery. The teeth were soaked in 3% NaOCl for 24 hours to dissolve any tissue on the root surface, and then stored in sterile 0.9% saline until used. Soft tissue and calculus were removed from the root surfaces with an ultrasonic scaler (EMS Piezon® Master 400, CH-1260 Nyon, Switzerland). Standard access preparation was carried out using a high-speed diamond round or fissure point (Mani, Tochigi, Japan) under water coolant.

Working model for electronic working length determination

Three plastic rectangular boxes, 15 × 3 × 4 cm in dimension were used for preparing this model. Ten teeth among the selected samples were glued to a plastic frame using modeling wax. Alginate was poured into the box, and the frame with the teeth was embedded into the alginate. In order to complete the electrical circuit of the apex locator, the labial clip was fixed to the edge of the plastic box and immersed in alginate. All the measurements were made within two hours of the model being prepared.

Electronic working length measurement

Five apex locators were used for this study-Root ZX II, i-Root, Elements Apex locator, Endo Master, and Triauto ZX Apex locator. Each tooth among the thirty samples was subjected to electronic working length measurement using all the five apex locators. Care was taken to see that all the circuits, batteries, and the operating modes of all five apex locators are fully functional, by connecting the file holder to the lip clip of the apex locator. Atfirst, canals were irrigated with 5.25% Sodium Hypochlorite using 26 gauge beveled needle in a 2 ml syringe (Unolok, Hindustan Syringes and Medical Devices Ltd, India). The pulp chamber was then gently dried with an air syringe and cotton pellets were used to dry the tooth surface and eliminate excess irrigating solution. A 15 K-file (Mani, Tochigi, Japan) with the file clip of the apex locator to be used, was attached to the file and inserted inside the canal until the apex locator showed the "apex" reading. The file was slightly pulled out until the apex locator showed the "0.5 mm" reading. The silicone stop was adjusted, the file was removed and the distance between the base of silicone stop and file tip was measured using a vernier caliper (Con Air Equipments Pvt. Ltd, India). Measurements were considered as valid if they were stable for at least 5 seconds. The recorded values were tabulated.

Measurement of actual working length

The actual canal length was determined by introducing a size 15 K-file into the canal until the tip of the file became visible at the apical foramen under microscope (Seiler, St. Louis, Missouri, USA). The silicon stop was then carefully adjusted to the reference level and the distance between the base of the silicon stop and the file tip was measured using a vernier caliper. The actual working length was established by subtracting 0.5 mm from this measured length. The actual length readings were compared to electronic working length readings.

Statistical analysis

The Excel and SPSS (SPSS Inc, Chicago version 10.5) software packages were used for data entry and analysis. The mean values were compared using Student t-test and multiple comparison procedures. Statistical readings were considered significant when P < 0.05.


  Results Top


The individual values of actual working length and canal length obtained using five different apex locators showed that most of the electronic measurements were within ± 0.5 mm of the actual length.

The mean values of actual working length and working length obtained using different apex locators are summarized in [Table 1]. [Table 2] shows the results from Student t-test and the P value. It shows comparison of the values obtained using the apex locators and the actual canal length. P > 0.05 for all the five tested apex locators. Hence, there was no statistically significant difference between the working lengths obtained using the five different apex locators and the actual working length.
Table 1: Mean values of actual working length and electronic working length (in mm)

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Table 2: Comparison of electronic measurements with actual canal length

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  Discussion Top


There are various methods for determining working length: Radiography, apex locators, Radio VisioGraphy, Xeroradiography, audiometric, tactile, patient's response, and paper points.[11] The radiographic method is the most common method of measuring working length in root canal therapy. Considering that the apical foramen frequently does not coincide with the radiographic apex, positioning of the file at the radiographic apex will often lead to under or over instrumentation.[12] In recent years, electrical devices have been developed for determining the length of the tooth without resorting to radiography. This is one of the breakthroughs that brought electronic science into the traditionally empirical endodontic practice. Here, the working length is determined by comparing the electrical resistance of the periodontal ligament with that of the gingiva surrounding the tooth, both of which should be similar.[13]

The Root ZX apex locator used in this study uses dual frequencies (0.4 and 8 kHz) and comparative impedance principles, was described by Kobayashi and Suda in 1994.[14] The change in electrical capacitance at the apical constriction is the basis for the operation of the Root ZX and its reported accuracy. Since its introduction the Root ZX has received considerable attention in the literature. Root ZX II (J. Morita Co., Tokyo, Japan) is the latest version of the Root ZX, one of the most evaluated EAL, that is often used as the 'gold standard' to which other EALs are compared.[15] The Root ZX has been exhaustively tested for accuracy in many clinical conditions, with many studies reporting 95-100% accuracy.[16],[17] i-Root (S-Denti, Seoul, Korea) is a fifth generation EAL which uses multiple frequencies to enable accurate detection of the apical constriction. I-Root was developed and upgraded based on the technology of e-Magic finder (EMF - 100 Series) apex locator. I-Root's unique patient management system (PMS) helps to measure the working length on the computer monitor, recording it in the database and printing the same if necessary.

Combination of electronic apex locators and electric handpieces is also becoming common and is able to achieve excellent results with the same accuracy as the stand-alone units.[18] By stopping the rotation of the NiTi files as the point estimated to be the end of the root canal is reached, these apex-locator-controlled handpieces eliminate the need to maintain working length with multiple files and the need for a reference point on the tooth. These devices can be used either as regular apex locators (with subsequent manual hand files) or for operating rotary NiTi files using the motor-controlled mode. The Triauto ZX (J. Morita Corp., Tokyo, Japan) is a rechargeable cordless handpiece designed for rotary canal preparation. It offers three automatic functions that significantly increase the accuracy and safety of root canal treatment-Auto start/stop, Auto torque reverse, and Auto apical reverse. Endo Master (EMS, Nyon, Switzerland) is a fifth generation apex locator combined with an endomotor for canal preparation. It has 3 different modes (Auto, Run, Apex over) for adaptation to various clinical situations.

Several studies were previously executed investigating accuracy of different apex locators. In vivo studies in which teeth to be extracted were used to compare electronic length to different target points such as apical foramen, apical constriction or radiographic apex.[19] In vitro studies used electro conductive materials like alginate, gelatin, agar or saline to simulate the clinical situations.[20] Here, an in vitro study was designed to allow easy determination of the actual tooth length. The media used in mounting models need to have similar electrical resistance to periodontal tissue to allow for accurate data collection.[20] Alginate has been described as the ideal embedding medium because its relatively firm consistency prevents intrusion of material into the apical foramen and resists force exerted by mechanical movement of the file, allowing the operator to accurately determine working length.[20] The main disadvantage was in its limited working time because the alginate tended to desiccate unless kept in a moist environment.[21] In the present study, all measurements were made within 2 hours of the model being prepared in order to ensure the alginate was kept sufficiently humid. The alginate model used in this study was accurate, easy to assemble, and cost-effective.[22]

In this study reading was performed when the bar of the device indicated 0.5 mm short of the apical foramen, considering a mean distance of 0.5 mm from the apical foramen to the apical constriction.[4] This indication of devices is in accordance with various other studies.[19],[21],[23],[24],[25] Some authors have suggested that taking the instruments slightly long when using EALs and then retracting them may increase the accuracy of readings of EALs.[26] Thus, to confirm the measurement, the file was advanced upto the apex reading and then retracted to obtain the consistent "0.5 mm" reading.

The results of the present study revealed that no statistically significant differences were found amongst the five apex locators and the actual working length of the teeth evaluated. The large majority of EAL measurements were within the ± 0.5 mm of the actual length for all the five electronic apex locators. The average values of all groups indicated that; all the apex locators tested in this study can accurately determine the root canal length with the Root ZX II, Triauto ZX and i-Root apex locator readings being the closest to the actual root canal length.


  Conclusion Top


All the five modern apex locators tested in this study, including apex locators incorporated with endomotor and pulp tester gave comparable results in comparison to actual working length. These newly advanced apex locators can determine the working length with high precision and greater predictability.


  Acknowledgement Top


The authors would like to express their gratitude to Dr. Lakshmi Prasad and Mr. Jignesh for the material support and help rendered during the study.



 
  References Top

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Steffen H, Splieth CH, Behr K. Comparison of measurements obtained with hand files or the Canal Leader attached to electronic apex locators: An in vitro study. Int Endod J 1999;32:103-7.  Back to cited text no. 18
    
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    Tables

  [Table 1], [Table 2]



 

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Abstract
Introduction
Materials and Me...
Results
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Conclusion
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