ORIGINAL ARTICLE J Korean Dent Sci. 2020;13(2):52-58 https://doi.org/10.5856/JKDS.2020.13.2.52 pISSN 2005-4742 ∙ eISSN 2713-7651 Evaluating Accuracy according to the Evaluator and Equipment Using Electronic Apex Locators Beom-Young Yu1,2 , Keunbada Son1,2 , Kyu-Bok Lee2,3 1Department of Dental Science, Graduate School, Kyungpook National University, 2Advanced Dental Device Development Institute (A3DI), Kyungpook National University, 3Department of Prosthodontics, School of Dentistry, Kyungpook National University, Daegu, Korea Purpose: Using two types of electronic apex locators, this study aimed to investigate the differences in accuracy ac- cording to the evaluator and equipment. Materials and Methods: Artificial teeth of the lower first premolars and two mandibular acrylic models (A and B) were used in this study. In the artificial teeth, the pulp chamber was opened and the access cavity was prepared. Using calibrated digital Vernier calipers, the distance from the top of the cavity and the root apex was measured to assess the actual distance between two artificial teeth. The evaluation was conducted by 20 dentists, and each evalu- ator repeated measurements for each electronic apex locator five times. The difference between the actual distance from the top of the cavity to the root apex and the distance measured using electronic measuring equipment was compared. For statistical analysis, the Friedman test the Mann–Whitney U-test were conducted and the differences between groups were analyzed (α=0.05). Result: As for the accuracy of measurement according to the two types of electronic apex locators, the value of the measurement error was 0.4753 mm in Dentaport ZX and 0.3321 mm in E-Cube Plus. Moreover, electronic apex loca- tors Dentaport ZX and E-Cube Plus showed statistically significant differences (P<0.05). As for the difference in the accuracy of the two types of electronic apex locators according to the evaluator, the resulting values differed depend- ing on the evaluator and showed a statistically significant difference (P<0.001). Conclusion: Electronic apex locator E-Cube Plus showed higher accuracy than did Dentaport ZX. Nevertheless, both types of electronic apex locators showed 100% accuracy in finding the region within root apex ±0.5 mm zone. Fur- thermore, according to the evaluator, the two electronic apex locators showed different resulting values. Key Words: Apical foramen; Apicoectomy; Dimensional measurement accuracy; Tooth apex; Tooth root Corresponding Author: Kyu-Bok Lee, https://orcid.org/0000-0002-1838-7229 Department of Prosthodontics, School of Dentistry, Advanced Dental Device Development Institute (A3DI), Kyungpook Na- tional University, 2177, Dalgubeol-daero, Jung-gu, Daegu 41940, Korea TEL : +82-53-600-7674, FAX : +82-53-426-7661, E-mail : [email protected] Received for publication October 27, 2020; Returned after revision November 29, 2020; Accepted for publication December 1, 2020 Copyright © 2020 by Korean Academy of Dental Science cc This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 52 Journal of Korean Dental Science Beom-Young Yu, et al: Accuracy according to the Electronic Apex Locators Introduction frequencies, namely, 1 and 5 kHz. However, Endex has inconvenience in the calibration according to the Accurate root canal length measurement is neces- impedance of the solution in the root canal for each sary for successful root canal treatment1) and the root root canal. canal length measurement is one of the important Kobayashi reported that the ratio of impedance had and difficult steps2,3). Apical constriction is known to a constant value in several electrolyte solutions when limit ideal instrumentation in the root canal and the the impedance in the root canal was measured, root canal filling1,4). Apical constriction is the region simultaneously, using the two different frequen- of the dentinocemental junction and the root canal cies4,12,13). The location of the file in the root canal can filling should be performed in the apical constriction be found in the principle that the resistance increases so that perfect wound healing would occur through as the file tip becomes closer to the apical constriction minimum contact with periapical tissues and that and that it sharply decreases when contacted with tissue destruction, inflammatory response, and for- the periodontal tissue. Electronic apex locator Root eign body reaction may decrease5,6). ZX (Morita, Kyoto, Japan) having two frequencies, Several methods have been investigated for accu- namely, 0.4 and 8 kHz, which shows the location of rate root canal length measurement. Cluster argued the file in the root canal, using this principle, was for the first time that the root canal strength could developed2,14). Additionally, it was reported that elec- be measured through electrical conduction7). On the tronic apex locator Root ZX had very high reliability basis of this, Suzuki8) found that the electric resis- compared with other electronic apex locators in the tance between the root canal and the oral mucosa previous studies15,16). was constant. Furthermore, using the principle that Recently, electronic apex locator E-Cube Plus there is a direct current resistance of 6.0 kΩ between (Saeshin, Daegu, Korea) has been developed in Ko- the root apex and the oral mucosa, Sunada devel- rea. E-Cube Plus is a frequency-dependent electronic oped the first electronic apex locator4,9). However, apex locator, using two frequencies, namely, 0.5 and the developed electronic apex locator used the di- 5 kHz. Until recently, several previous studies that rect current; hence, the polarity of the electrode ap- compare the accuracy using several electronic apex peared as a problem. Inoue10) developed the second- locators have been reported14,17,18). However, there generation electronic apex locator, using alternating has been no study that evaluated the accuracy of the current. This is a method of measuring the difference newly developed electronic apex locator. Therefore, in impedance in the root canal, using one frequency. this study aimed to investigate the differences in ac- Nonetheless, the second-generation electronic apex curacy according to the equipment and evaluator us- locator has a demerit that the measurement becomes ing Morita’s Dentaport ZX, which is widely used in inaccurate if there are electrolytes, excessive fluid, clinical practice and has high reliability and domestic leakage, excessive bleeding, etc2,6). product of electronic apex locator E-Cube Plus. The To overcome this, a 3G electronic apex locator was null hypothesis of this study is that there would be developed. The 3G electronic apex locator used the no difference in accuracy according to the equipment principle that there is the biggest difference in the between the two types of electronic apex locators. impedance between two frequencies in the apical Moreover, there is no difference in accuracy accord- constriction6). With this principle, Yamashita11) devel- ing to the evaluator. oped Endex that measured the root canal strength, using the difference in the impedance between two J Korean Dent Sci 2020;13(2):52-58 53 Beom-Young Yu, et al: Accuracy according to the Electronic Apex Locators Fig. 1. (A, B) Artificial teeth. Length measurement with digi- ABtal Vernier calipers (Mitutoyo Corp., Kawasaki, Japan). ABFig. 2. Typodont model with artificial teeth (A) and (B). Materials and Methods Corp., Kawasaki, Japan). The measured distance of artificial teeth A was 17.73 mm, whereas that of ar- This study used the artificial teeth of the lower first tificial teeth B was 18.22 mm (Fig. 1). The measured premolars (B22X Series; Nissin Dental, Kyoto, Japan) distances were designated as the actual distances in and mandibular acrylic models (CON1002 Series; this study. For the measurement using the electronic Nissin Dental). With the artificial teeth, the pulp cav- apex locator after the completion of the measure- ity was opened using a high-speed handpiece and ment, electrolyte solution (Conductive paste, Nissin the access cavity was prepared. To minimize the Dental) was put into the model, and the teeth were error that might occur in the root canal length mea- fixed to the model (Fig. 2). surement, the one-third region of the occlusal surface This study used Dentaport ZX using two frequen- was removed vertically to the longitudinal axis of cies, 0.4 and 8 kHz, and frequency-dependent elec- teeth. #15 K-file (Micro-Mega, Besançon, France) was tronic apex locator E-Cube Plus using 0.5 and 5 kHz, put into the root canal to check the apical foramen recently developed (Fig. 3). opening, and for the measurement accuracy, all the Measurements were conducted by 20 dentists. pulp in the root canal was removed. Moreover, to They were asked to measure the relevant model for prevent the evaluator’s prediction, two artificial teeth each electronic apex locator, and one evaluator mea- with different lengths (A and B) were used. sured the model with each electronic apex locator Before the fixation of the artificial teeth to the model five times. Finding the mean value of the repeated after removal, the actual distance between the teeth measurements obtained five times, it was designated was measured. To secure the reliability of the mea- as the root canal length by the one particular evalu- surement, the distance between the top of the cavity ator. Electronic apex locator Dentaport ZX measured and the root apex of the two teeth was measured the artificial teeth A, and electronic apex locator E- using calibrated digital Vernier calipers (Mitutoyo Cube Plus measured the artificial teeth B. The evalu- 54 J Korean Dent Sci 2020;13(2):52-58 Beom-Young Yu, et al: Accuracy according to the Electronic Apex Locators Fig.