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 Table of Contents  
Year : 2018  |  Volume : 30  |  Issue : 2  |  Page : 130-134

Accuracy of two different apex locators for working length determination during root canal retreatment of mandibular molars using two different retreatment files: An in vitro study

Department of Conservative Dentistry and Endodontics, Bhojia Dental College and Hospital, Baddi, Himachal Pradesh, India

Date of Web Publication5-Dec-2018

Correspondence Address:
Dr. Ajay Chhabra
Department of Conservative Dentistry and Endodontics, Bhojia Dental College and Hospital, Baddi, District Solan, Nalagarh - 173 205, Himachal Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/endo.endo_88_17

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Aim: The aim of this study was to evaluate the accuracy of two different apex locators for working length determination during root canal retreatment of mandibular molars in an in vitro study.
Method: Sixty extracted mandibular first molars with separate mesial canals and apical foraminae and one distal canal were selected. The mesiobuccal and distal canals were investigated; the length with the file tip at the major diameter was defined as the tooth length (TL). The canals were prepared with ProTaper files to 1 mm short of this and filled with gutta-percha and AH Plus sealer. One week later, the root fillings were removed using ProTaper and M2 retreatment files. Tooth length was remeasured and recorded as the retreatment tooth length (RTL). Then electronic measurements were taken at the major (electronic apex locator (EAL) major) and minor (EAL minor) foraminae with Root ZX and Apex ID apex locator as suggested by the instrument display. These lengths were compared with RTL and measurements 0.5 and 1 mm short of this distance.
Results: For both canals, no significant difference was found between RTL and EAL major, and 0.5 mm short of RTL and EAL minor with Root ZX apex locator and protaper retreatment files. There were significant differences found between Apex ID apex locator with M2 retreatment files readings.
Conclusion: Root ZX apex locator was more accurate as compared to Apex ID apex locator in determining the working length in teeth after removing the root canal obturating material.

Keywords: Apex ID apex locator, Mtwo retreatment files, Protaper retreatment files, Retreatment, Root zx zpex Locator, Working Length

How to cite this article:
Chhabra A, Bhatia R, Garg N, Sharma S, Dogra A, Jhamb A. Accuracy of two different apex locators for working length determination during root canal retreatment of mandibular molars using two different retreatment files: An in vitro study. Endodontology 2018;30:130-4

How to cite this URL:
Chhabra A, Bhatia R, Garg N, Sharma S, Dogra A, Jhamb A. Accuracy of two different apex locators for working length determination during root canal retreatment of mandibular molars using two different retreatment files: An in vitro study. Endodontology [serial online] 2018 [cited 2022 Aug 14];30:130-4. Available from: https://www.endodontologyonweb.org/text.asp?2018/30/2/130/246938

  Introduction Top

Working length plays an important role during endodontic treatment. It helps in complete removal of the debris from the canal and is considered to be the most critical juncture of successful therapy.[1] Canal preparation is ideally done and filled to the minor foramen which is considered to be the narrowest point of the canal. At this point, there is a minimum blood supply and has innate repair potential.[2] There are various methods for determination of working length out of which radiographic is generally accepted. This method has a disadvantage that it cannot determine the apical constriction, but with the introduction of the electronic apex locators, this problem can be solved as it works on the electronic principle and can determine the treatment and retreatment working length up to the minor foramen.[3] This study aims to evaluate the accuracy of Root ZX and Apex ID apex locators for retreatment working length determination in the molar root canals.

  Materials and Methods Top

The present study was conducted in the Department of Conservative Dentistry and Endodontics at Bhojia Dental College and Hospital. The study sample constituted of 60 extracted mandibular first molars. Teeth with three canals, morphologically normal and no evidence of fracture or resorption were included in the study while teeth with carious roots, external or internal root resorption, open apex roots were excluded from the study. With the use of ultrasonic scaler, external debris were removed. Expeditious bur (Mani, Tochigi, Japan) was used for access preparation and Endo Z bur (Dentsply Tulsa Dental Specialties; Tulsa, Oklahoma) for refinement was used. Decoronation was done at the cementoenamel junction following access preparation, as it provides a stable horizontal reference point for measurement of working length. Size #15 K-file (Mani, Tochigi, Japan) was used for pulp debridement. Irrigation protocol was followed using 3% sodium hypochlorite (Dentpro, India). ×2.5 loupes were used for calculating the length of mesiobuccal and distal root with 15# k file which was advanced until it appeared at the apical foramen. Silicon stop was accustomed at the reference point, and the length between stop and tip was calculated using Vernier Caliper to the nearest 0.5 mm. After repeating measurements for three times by two individuals, their mean value was calculated. This length achieved is called as tooth length (TL) and after deducting 1 mm, the length established is the working length. Protaper files were used for biomechanical preparation. For working in the middle third of the root, shaping files S1 and S2 were used followed by finishing file F1 keeping in mind the manufactures guidelines. Ethylenediaminetetraacetic acid paste was used to smear the files before introducing them into the canal. 2 ml of 3% NaOCl was flushed into the canal during preparation. Paper points were used for drying the canals and were then obturated with F1 gutta-percha points which were coated with AH Plus sealer using single cone technique. The cavity was closed with cavity and teeth were stored in 100% moisture for 7 days. Two different rotary files were used for retreatment after 7 days and accordingly samples were divided into two groups as follows.

Group I

With the help of Protaper retreatment files, the obturating material was removed from the canal. Removal from coronal third was done with D1 file while D2 file was used for removal from the middle and D3 to the working length.

Group II

Mtwo retreatment files were used for removal of obturating material. Two files 15/0.5 and Mtwo retreatment file 25/0.5 were used up to the working length. 3% NaOCl was used for irrigation after removal of material from the canals. With 15 K-file mesiobuccal and distal root was re-measured with silicon stop adjusted to the reference point and distance from stop to the file tip was measured with Vernier Caliper to the closest to 0.5 mm. Two individuals repeatedly measured each tooth thrice and calculated its mean. Working length after removing the material was obtained by deducting 1 mm from the TL. With the help of radiographs amount of gutta-percha remained in the canal was calculated. Next, to the setting alginate, roots were embedded with their apical third submerged into the alginate and the lip clip of the apex locator was placed into the setting alginate so that the circuit of apex locator can be completed. These groups were further divided into subgroups.

Sub Group I

Root ZX apex locator was used for the measurement of working length.

Sub Group II

Apex ID apex locator was used for measuring the working length.

Working length determination using root ZX and apex id apex locator

For Root ZX apex locator, 15 # K file was used for the measurement of working length till the lowermost part of the green bar on the apex locator screen. For Apex ID apex locator measurements were taken when the display on the screen showed “0.” The length between the stopper and the file tip was measured and these readings for each tooth were repeated three times by two operators and the values were recorded. Complete procedure was performed within 2 h. These values were compared with the retreatment TL.

  Results Top

Data were calculated in the tabulated form and was subjected to statistical analysis [Table 1]. ANOVA test was used to evaluate the values which revealed the mean difference values of SBIA, SBIIA, SBIB, SBIIB to be 0.93, 0.33, 0.03, 0.10 and the standard deviation for SBIA, SBIIA, SBIB, SBIIB be ± 0.21, ±0.40, ±0.12, and ± 0.02, respectively. These results were then evaluated with post hoc test which showed no significant difference in Apex ID with Mtwo retreatment files, but a significant difference was seen in the Root ZX apex locator and Protaper retreatment files. Difference of Apex ID with Mtwo retreatment files was −0.3000 with the value of P = 0.015 and that for Root ZX with Protaper retreatment files was −0.0100 with the value of P = 0.015 [Table 2].
Table 1: Mean difference and standard deviation of working length determination between sub groups

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Table 2: Mean difference between retreatment working length in sub groups

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[Graph 1] shows mean difference between working length calculated with Vernier Caliper and apex locator.

[Graph 2] shows mean difference between working length calculated by Vernier calculated with Vernier Caliper and apex locator after retreatment of the tooth.

  Discussion Top

Apex locator is based on the principle that certain features of human tissue can be designed using electrical components. Therefore, it is possible to detect the canal terminus, by measuring the electrical properties of the model.[4] In number of studies performed on apex locator, teeth with single straight canals were used. We selected canals from mandibular molars so that more exacting model can be generated. Another reason was that mesiobuccal root of mandibular molar is more constricted, irregularly formed and is a complicated structure as compared to the teeth with the single canal. Reason for selecting the distal canal was to create standardization. 3% sodium hypochlorite was used to immerse teeth to remove soft- or hard-tissue tags present on the root surface. Crowns were removed to generate a horizontal reference point.[5],[6],[7] Weiger et al. also focused on the preparation of a reference point and to consider the use of stable silicon stop.[8]

Access opening was done after preparing reference surface and working length was measured with the help of Vernier Caliper. The preparation of the root canal was done to the F1 Protaper universal file size.

Peters et al. have shown that Protaper file does not have U-shaped design and due to the presence of variable taper on its working end, it minimizes the number of instrument per set, also claims that there is a reduction in the torsional load that decreases the frictional surface resulting in the decrease in the effectiveness of cutting of the instrument.[9] By using single cone technique root canals were filled with F1 gutta-percha. AH plus sealer was used to smear the canal and gutta-percha cone before sealing it into the canal. The advantage of using single cone technique is that the master cone best matches the geometry of nickel–titanium rotary files. Sealing canal with single cone and sealer helps in formation of a single mass that does not result in failure as seen in multiple cone technique.[10],[11],[12],[13] Because of presence of less shrinkage during setting and long-term stability, resin-based sealer (AH Plus) was preferred. To generate conditions similar to the oral cavity and to establish total setting of the sealer, teeth were immersed in 100% moisture postobturation for 1 week.[14],[15],[16],[17],[18]

Wilcox and Juhlin in their study showed that the detection and removal of obturating material which gets deposited on the walls of root canal is difficult if solvent is used.[19] It may also hamper the antimicrobial properties of irrigants, and increase operating time, therefore using two file systems, i.e., Protaper and Mtwo retreatment files were used for removing obturating material from the canals.[20] Protaper retreatment files constitute three files that have an active tip which aid in initial entrance into the obturating material during its removal. According to the manufactures's recommendations D1 and D2 should be used for preparation of coronal and middle third while D3 was used up to the working length. Mtwo retreatment file system constituting two instruments of size 15 and 25 with 0.5% taper and two blades of S-shape crossection with an active tip claims easy entrance into the obturating material. The findings of this study are in accordance with the study done by Marfisi et al. showed that because of presence of S-shaped crossection and a shorter pitch length it becomes easy to penetrate into the root canal material. Mtwo retreatment files have inferior properties as compared to Protaper retreatment files because of presence of two cutting edges which aggressively cuts the dentin.[21],[22]

In the present study, Root ZX showed better results as compared to Apex ID, possibly because the residual root filling material occluding the dentinal tubules predisposes to a reduction in electrical conductivity and an increase in impedance, a factor potentially enhancing the electrical detection of the Apical File. Working length determined by the Root ZX before obturating the root canals and after removing the root fillings was not significantly different.[23]

When the result of Protaper and Mtwo retreatment system were combined with that of the Root ZX and Apex ID apex locator, Root ZX with Protaper retreatment files proved to have better results as compared to Apex ID with Mtwo retreatment files with significant values, as it does not aggressively cut the dentin during retreatment thus does not alter the apical constriction as compared to the Mtwo retreatment files which cuts the dentin aggressively during the removal of the gutta-percha during retreatment of the tooth thus alters the position of the apical constriction. Chirila et al. in their study also showed that Root ZX (third generation) apex locator is more accurate than Apex ID (fourth generation) apex locator. The accuracy of Root ZX was found to be 98.28% while that of Apex ID apex locator was 86.66% ±0.5 mm from the actual length.[24],[25]

  Conclusion Top

The apex locators can be successfully used to determine the working length in endodontic retreatment. Under the conditions of our in vitro study Protaper retreatment files left significantly lesser gutta-percha and root canal sealer as compared to Mtwo retreatment files, and hence proved to be more efficient than Mtwo retreatment files. Under the parameters of this study Root ZX apex locator was more accurate as compared to Apex ID apex locator in determining the working length in teeth after removing the root canal obturating material.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Nasil S, Asifulla M, Chandra V, Idris M, Razvi FS, Geeta IB.In vitro evaluation of the accuracy of five different electronic apex locators. Saudi Endod J 2015;5:177-81.  Back to cited text no. 1
Cimilli H, Aydemir S, Arican B, Mumcu G, Chandler N, Kartal N, et al. Accuracy of the Dentaport ZX apex locator for working length determination when retreating molar root canals. Aust Endod J 2014;40:2-5.  Back to cited text no. 2
Gordon MP, Chandler NP. Electronic apex locators. Int Endod J 2004;37:425-37.  Back to cited text no. 3
Shanmugaraj M, Nivedha R, Mathan R, Balagopal S. Evaluation of working length determination methods: An in vivo/ex vivo study. Indian J Dent Res 2007;18:60-2.  Back to cited text no. 4
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Tilakchand M, Malu KN, Kidiyoorc KH. Evaluation of accuracy of two electronic apex locators Viz Propex-II and elements apex locator: An in-vitro study. IJDA 2010;2:327-31.  Back to cited text no. 6
Santhosh L, Raiththa P, Aswathanarayana S, Panchajanya S, Reddy JT, Susheela SR, et al. Influence of root canal curvature on the accuracy of an electronic apex locator: An in vitro study. J Conserv Dent 2014;17:583-6.  Back to cited text no. 7
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Pereira AC, Nishiyama CK, Pinto LC. Single cone obturation technique: A literature review. RSBO 2012;9:442-7.  Back to cited text no. 10
Sadr S, Golmoradizadeh A, Raoof M, Tabanfar MJ. Microleakage of single-cone gutta-percha obturation technique in combination with different types of sealers. Iran Endod J 2015;10:199-203.  Back to cited text no. 11
Katalinić I, Baraba A, Glavicić S, Segović S, Anić I, Miletić I, et al. Comparison of vertical forces during root canal filling with three different obturation techniques. Coll Antropol 2013;37:895-9.  Back to cited text no. 12
Pitout E, Oberholzer TG. Leakage of teeth root-filled with guttaFlow and a single GP cone compared to lateral condensation and warm vertical condensation. SADJ 2009;64:104, 106-8.  Back to cited text no. 13
Nunes VH, Silva RG, Alfredo E, Sousa-Neto MD, Silva-Sousa YT. Adhesion of epiphany and AH plus sealers to human root dentin treated with different solutions. Braz Dent J 2008;19:46-50.  Back to cited text no. 14
Ozok AR, van der Sluis LW, Wu MK, Wesselink PR. Sealing ability of a new polydimethylsiloxane-based root canal filling material. J Endod 2008;34:204-7.  Back to cited text no. 15
Fisher MA, Berzins DW, Bahcall JK. An in vitro comparison of bond strength of various obturation materials to root canal dentin using a push-out test design. J Endod 2007;33:856-8.  Back to cited text no. 16
Ungor M, Onay EO, Orucoglu H. Push-out bond strengths: The epiphany-Resilon endodontic obturation system compared with different pairings of Epiphany, Resilon, AH plus and gutta-percha. Int Endod J 2006;39:643-7.  Back to cited text no. 17
Gesi A, Raffaelli O, Goracci C, Pashley DH, Tay FR, Ferrari M, et al. Interfacial strength of resilon and gutta-percha to intraradicular dentin. J Endod 2005;31:809-13.  Back to cited text no. 18
Wilcox LR, Juhlin JJ. Endodontic retreatment of thermafil versus laterally condensed gutta-percha. J Endod 1994;20:115-7.  Back to cited text no. 19
Erdemir A, Eldeniz AU, Belli S, Pashley DH. Effect of solvents on bonding to root canal dentin. J Endod 2004;30:589-92.  Back to cited text no. 20
Marfisi K, Mercade M, Plotino G, Duran-Sindreu F, Bueno R, Roig M, et al. Efficacy of three different rotary files to remove gutta-percha and resilon from root canals. Int Endod J 2010;43:1022-8.  Back to cited text no. 21
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  [Table 1], [Table 2]


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