Nigerian Journal of Health Sciences

: 2023  |  Volume : 23  |  Issue : 1  |  Page : 24--30

How comparable is electronic to radiographic method in working length determination during endodontic treatment?

TO Ogundare1, KO Ogundipe2, AM Akinpelu1, CT Bamise3, AO Oginni3,  
1 Department of Restorative Dentistry, Obafemi Awolowo University Teaching Hospitals' Complex, Ile – Ife, Nigeria
2 Department of Oral and Maxillofacial Surgery, Obafemi Awolowo University, Ile – Ife, Nigeria
3 Department of Restorative Dentistry, Obafemi Awolowo University, Ile – Ife, Nigeria

Correspondence Address:
Dr. T O Ogundare
Department of Restorative Dentistry, Obafemi Awolowo University Teaching Hospitals' Complex, Ile – Ife


Background: Working length (WL) determination continues to be an important stage for a successful outcome of root canal treatment. Accuracy of the WL determination methods remains a subject of debate, thus this study aimed to assess how comparable the two methods of radiographic and electronic WL determination is. Materials and Methods: A cross-sectional study done at the Conservative Unit of the Dental Hospital, OAUTHC, Ile – Ife to compare radiographic and electronic apex locator (EAL) methods of WL determination during endodontic treatment. Data analysis was done using the Statistical Package for the Social Sciences software (SPSS version 22, IBM, USA). The level of significance was set at P < 0.05. Results: The mean age of the study population was 36.22 ± 10.74 years, whereas there were 8 (44.4%) males and 10 (55.6%) females. Forty-one canals (13; 31.7% single, 5; 24.4% double and 6;43.9% triple canals) from 24 teeth in 18 participants had endodontic therapy. The adjusted radiographic mean WL was as follows: maxilla; 20.33 ± 1.44, mandible; 20.59 ± 1.97, single canal; 19.67 ± 1.60, double canal; 19.20 ± 0.79, triple canal; 20.06 ± 2.31, anterior teeth; 19.83 ± 1.84 and posterior teeth; 19.53 ± 1.75. With the EAL, the mean values were as follows: maxilla; 19.35 ± 1.35, mandible; 19.95 ± 1.76, single canal; 19.50 ± 1.83, double canal; 19.10 ± 0.57, triple canal; 20.11 ± 1.84, anterior teeth; 19.67 ± 2.12 and posterior teeth; 19.68 ± 1.51. There were no statistically significant (P > 0.05) differences between the two methods of WL determination except in the maxilla (P < 0.001) when compared by the type of canals, tooth location, and tooth arch. Conclusion: Both methods of WL determination showed a high level of accuracy when compared and can be used singly.

How to cite this article:
Ogundare T O, Ogundipe K O, Akinpelu A M, Bamise C T, Oginni A O. How comparable is electronic to radiographic method in working length determination during endodontic treatment?.Niger J Health Sci 2023;23:24-30

How to cite this URL:
Ogundare T O, Ogundipe K O, Akinpelu A M, Bamise C T, Oginni A O. How comparable is electronic to radiographic method in working length determination during endodontic treatment?. Niger J Health Sci [serial online] 2023 [cited 2023 Sep 27 ];23:24-30
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Full Text


Non-surgical root canal treatment (RCT) remains an important aspect of dental treatment options for pulpally affected teeth. Successful RCT leads to the retention of more teeth, thereby avoiding the negative functional and psychosocial problems usually associated with tooth extraction.[1]

The stages involved in successful treatment outcome following endodontic therapy include clinical and radiographic preoperative assessment, access cavity and biomechanical preparation of the root canals, three-dimensional obturation of the canals and the subsequent restoration of the tooth.[2] The aforementioned stages require accurate determination of the working length (WL), which ensures that biomechanical preparation and obturation ends at the desired level of apical constriction estimated as 0.5 mm–2 mm to the radiographic apex.[3]

The WL can be determined through several methods including: the estimated WL (EWL) from pre-operative radiograph, moisture on paperpoints, tactile method, radiographic method and electronic apex locator (EAL).[4] The accuracy of these different methods varies with attendant advantages and disadvantages. For example, while the tactile method is often inaccurate, drawbacks with the radiographic method and apex locators are radiation exposure and distorted images associated with radiographs and precision required with the apex locators use.[5],[6] To optimise the attributes of several methods of estimating WL, the European Society of Endontotology[7] recommends the use of radiographic and electronic methods either singly or as a combination.

EAL operates on the principle of impedance and is said to be associated with improved rate of success following endodontic treatment.[8],[9],[10] It comprises the monitor, file and lip clips connected to form a circuit. Its use entails placing the lip clip by the commissure of the mouth to complete the circuit. The file held in place with the file clip is gradually introduced into the canal and the measurement is indicated at the beeping sound with colour indication signifying WL at the apical constriction.

Although previous reports have concluded that there is no difference in the accuracy between radiographic and electronic methods,[11],[12] the issue of supplementing the radiographic method with the electronic method remains a concern. Thus, the use of a single and reliable method for estimating WL is desirable.

Although the radiographic method is the more commonly method for estimating WL, earlier studies[3],[8] have shown the problems associated with its use. These include radiographic distortion arising from magnification, radiation exposure from multiple radiographs especially during pregnancy, increased waiting time, inconvenience of putting files in the mouth for a period of time before taking radiographs and possibility of the files shifting from the reference point.

We, therefore, aimed to carry out this study to compare the VDW.GOLD RECIPROC apex locator with the radiographic method in the determination of WL during endodontic treatment.

 Materials and Methods

The study was carried out as a cross-sectional study at the Conservative Unit of the Dental Hospital, OAUTHC, Ile – Ife. Patients recruited were previously examined and scheduled for the non-surgical root canal therapy on one or more teeth. The patients were aged 18 years and above and gave consent to participate in the study.

All the prospective subjects were given a detailed explanation of the procedure to be performed which included: The endodontic procedure, radiographs and use of the apex locator.

The exclusion criteria were as follows: pregnant patients, patients with pacemakers, those with acute infections, swelling, teeth with calcified canals and open apices and the third molars.

A purposive sample size in which all the patients available during the study period were included. Data were collected using a standard data collection form designed for this study. Information gathered included: Socio-demographics, EWL, adjusted radiographic WL (ARWL) and EAL WL of each individual tooth treated. The Federation Dentaire Internationale (FDI) notation was used and the mean WL was calculated in each method based on tooth arch, type of canal and tooth arch.

Estimated working length

The pre-operative radiograph taken using the long cone parallel technique was used for the EWL. It was calculated by measuring the distance in millimetres from the highest point on the incisal or occlusal level of the tooth to the radiographic apex.

Endodontic procedure

The endodontic procedures were performed by the six residents rotating through the Conservative Dentistry Unit at the time of study. Rubber dam was placed and access cavity prepared under local anaesthesia (2% xylocaine 1:80,000 adrenaline) as necessary. The pulp chamber was unroofed and debrided with normal saline. The location of the canals was confirmed with the researcher as well as the introduction of the files at the EWL.

Working length determination using radiographic method

Following the access cavity preparation and opening of the pulp chamber, the first file that binds at the apical portion using the EWL is placed in the canal and radiograph taken by the radiographer. This is subsequently taken as the radiographic WL or adjusted as necessary to become the ARWL.

Working length determination using apex locator

This was performed by the researcher who is acquainted with the study protocol and has been previously calibrated into using the apex locator. The apex locator used was the VDW.GOLD RECIPROC with an integrated apex locator (Bayerwaldstr, Munich Germany) [Figure 1]. The instrument is known to have a low error index because of its apical auto stop characteristic on getting to the apex. The instrument was introduced to the patient and procedure explained appropriately. The tooth to be measured was isolated with rubber dam, the canal irrigated with normal saline and dried with paper points (Gabadent, Japan) while the access cavity was dried with cotton rolls. The lip clip is placed at the opposite lip commissure of the tooth to be treated to complete the circuit. Following calibration of the instrument into apex locator mode, a C Pilot or K file is inserted into the canal and gradually advanced towards the apical direction with the aid of the file clip. The WL is taken at the third green LED light on the apex locator monitor. This signifies the WL at the apical constriction and recorded in millimetres.{Figure 1}


Data analysis

Analysis was done using Statistical Package for the Social Sciences (SPSS Version 22, IBM, Chicago, Illinois, USA). Analysis of discreet variables expressed in frequencies and percentages. Associations between categorical variables were tested using Chi-square. The mean scores between the EWL, ARWL and apex locator were compared using the one-way ANOVA, whereas the mean scores between the ARWL and apex locator were compared using a paired t-test. The level of significance was set at P < 0.05.



A total of 18 consenting patients with 24 teeth requiring RCT were seen. The age range was between 21 years and 57 years. The mean age was 36.22 ± 10.74 years. There were 8 (44.4%) males and 10 (55.6%) females giving a male-to-female ratio of 0.8:1.3 [Table 1].{Table 1}

[Table 2] shows the tooth type, tooth arch and number of canals. From the 24 teeth treated, there were 13 maxillary teeth and 11 mandibular teeth. In all, 10 (5; 50% maxillary and 5; 50% mandibular) anterior teeth and 14 (8; 57.1% maxillary and 6; 42.9% mandibular) posterior teeth were seen.{Table 2}

[Table 2] and [Table 3] shows that a total of 41 canals (13 single canals, 5 double canals and 6 triple canals) in 24 teeth were seen. The 10 anterior teeth in both arches had a single root and single canal. The anterior teeth were 5 maxillary teeth (1 central incisor, 3 lateral incisors and 1 canine) and 5 mandibular teeth (2 central incisors and 3 canines). Furthermore, there were single canals in the premolars; 2 on the upper second premolar and 1 in the lower first premolar. As regards the posterior teeth with 2 canals; there were 5 maxillary premolars (3 first premolars and 2 s premolars). Three canals were found in 6 teeth (1 in the upper first molar, 4 in the lower first molar and 1 in the lower second molar).{Table 3}

[Table 2] reveals the WL of individual tooth treated using the EWL, ARWL and EAL in the maxilla. The mean scores of the WLs were 20.36 ± 1.63 mm, 20.33 ± 1.44 mm and 19.35 ± 1.35 mm using EWL, ARWL and EAL, respectively.

In the mandible, it was 20.59 ± 1.97 mm, 20.59 ± 1.97 mm and 19.95 ± 1.76 mm, respectively [Table 3]. When the mean scores were compared across the three categories, it was found to be statistically significant (P = 0.001) in the maxilla [Table 2], whereas in the mandible [Table 3], it was not statistically significant (P = 0.310).

[Table 4] shows the comparison between the mean scores of ARWL and EAL in the maxilla and mandible. The mean differences between the ARWL and EAL in the maxilla and mandible were 0.98 mm and 0.64 mm, respectively. It was observed that there was a statistically significant difference (P < 0.001) between the two methods in the maxilla while in the mandible, it was not significant (P = 0.180).{Table 4}

[Table 5] shows the comparison between the mean scores of EWL, ARWL and EAL in the different canals. It was observed that there was a significant difference across the three methods in the single canals (P = 0.010) while there were no significant differences in the double canals (P = 0.100) and triple canals (P = 0.230).{Table 5}

[Table 6] shows the comparison between the mean scores of ARWL and EAL in the different canals. The mean differences between the ARWL and EAL in the canal types were 0.17 mm, 0.10 mm and − 0.05 mm, respectively. It was observed that there was no significant difference between the two methods in the single canals (P = 0.417), double canals (P = 0.591) and triple canals (P = 0.889).{Table 6}

[Table 7] shows the comparison between the mean scores of EWL, ARWL and EAL in the anterior and posterior teeth. The mean scores in the anterior teeth were 19.94 ± 1.88 mm, 19.83 ± 1.84 mm and 19.67 ± 2.12 mm, respectively (P = 0.119) while in the posterior teeth, the mean scores were 20.55 ± 1.58 mm, 19.53 ± 1.75 mm and 19.68 ± 1.51 mm (P = 0.006).{Table 7}

[Table 8] shows the comparison between the mean scores of ARWL and apex locator in the anterior and posterior teeth. The mean scores in the anterior teeth were 19.83 ± 1.84 mm (adjusted radiographic length) while it was 19.67 ± 2.12 mm with the apex locator (mean difference = 0.16 mm) and this was found to be insignificant (P = 0.545). In the posterior teeth, mean scores were 19.53 ± 1.75 mm (adjusted radiographic length) while it was 19.68 ± 1.51 mm with the apex locator (mean difference = −0.15 mm) and this was found to be insignificant (P = 0.470).{Table 8}


Affordability and ease of access to RCT, most especially in our resource-limited environment with low health insurance coverage can be quite challenging.[13] Therefore, accurate WL determination which prevents post-operative pain should be of enormous priority when this procedure is performed.[14],[15],[16] We compared the use of EAL (VDW.GOLD RECIPROC) with adjusted radiographic method in WL determination during endodontic treatment.

ANOVA was initially used to compare the mean scores of the EWL, ARWL and EAL while the paired t-test was subsequently used to compare the mean scores between the two methods of ARWL and EAL.

From this study, it was observed that the mean differences between the two techniques (ARWL and apex locator) were low. Furthermore, there were no statistically significant differences between the two methods except in the maxilla. The problem of gravity when files are placed in the maxillary teeth may be responsible for this with the possibility of files moving from the reference point.[12]

Previous studies[17],[18],[19] have also reported that apex locators are not superior but with the advantage of no radiation when conventional radiographic method and apex locator are compared in WL determination.

The reason for no difference when the WL between the tooth arches, tooth location and across types of canals when compared may be related to the specificity of these tools and the operator's experience. Once a canal has been located with a straight line access, it shows that with adequate mastering of the use of either the apex locator or radiograph, a desired result is achieved. As a result of this, the apex locator and the radiographic WL can be described as giving the desired WL. Although it appears the apex locator is easier to use and may give better patient acceptance, it is imperative to state that posterior teeth with multiple canals may pose a higher challenge when determining WL. The apex locator might have the challenge of accessibility to these areas and could also take more time as compared to the anterior teeth with single canals.

Furthermore, the competence of the residents that performed the root canal therapy procedures might be related to the WL determination. It is a procedure that they are expected to perform a certain number of times, thus it is expected that they would have been used to the regular method of radiographic WL determination over time, therefore translating to accurate determination of WL.

Because of the low mean error of the apex locator, it is a good tool of determining WL as long as guidelines for its use are adhered to. This includes: proper explanation to the patient, well connected instrument, isolation with rubber dam and drying of the canals before inserting the file. As compared to radiographs, which can come with blurred images thus necessitating a repeat of the radiograph.

With the advent of COVID-19, the apex locator maybe a better option for WL determination. This could be the case in that, it is used directly chairside intraoperatively as compared to the radiographic WL that entails sharing of the radiographic machine among several patients in a day coupled with the prolonged waiting time. Moreover, it has been speculated that the global market for apex locators is expected to change following the COVID-19 pandemic.[20] This trend should be carefully monitored to keep up with the changes that may come with the sale of the instruments and possibility of the manufacturers producing new types.

Not requesting for payments for the use of apex locator for WL determination as compared to radiographs may also be of an added advantage to patients. Avoidance of radiographic films procurement would make it cheaper and when the cost of procuring and maintenance of the radiographic machine and apex locators are compared, the apex locator ultimately seems to be economical. In our resource-limited environment with patients having to do out-of-pocket payment, this might be a better option.

With the additional function of this instrument, coupled with the fact that the clinical setting in which this study was carried out comprises dental students, house officers and residents it is of enormous benefit for clinical teaching.

Both radiographic and apex locator appear similar in the determination of WL during endodontic treatment. Comparing with the gold standard (ex vivo method) would have helped to determine the accuracy of either method; however, this could not be done for ethical reasons. This is a limitation to the study, however, both methods are said to be accurate, with the apex locator requiring meticulous attention but offering the advantage of no radiation and avoidance of multiple exposures to radiographs as a result of distortion.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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