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ORIGINAL ARTICLE
Year : 2015  |  Volume : 3  |  Issue : 3  |  Page : 70-75

Comparative evaluation of working length determination by using conventional radiography, digital radiography and electronic apex locator


Department of Conservative Dentistry and Endodontics, Sudha Rustagi College of Dental Sciences and Research, Faridabad, Haryana, India

Date of Web Publication30-Oct-2015

Correspondence Address:
Dr. Meenu Garg Singla
Department of Conservative Dentistry and Endodontics, Sudha Rustagi College of Dental Sciences and Research, Kheri More, Village Bhopani, Faridabad - 121 002, Haryana
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2321-4619.168736

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  Abstract 

Objective: The aim of this study was to compare the diagnostic efficacy of an electronic apex locator (EAL), conventional radiography, and digital radiography in working length (WL) determination. Materials and Methods: This study was performed on 25 vital premolar teeth, scheduled for extraction in orthodontic patients. After administration of local anesthesia, the teeth were isolated and the pulp cavities were accessed. The WL for each tooth was measured by an EAL (Justy II; Yoshida Dentcraft, Tokyo, Japan), conventional and digital radiographies. Immediately after WL determination, the teeth were extracted and actual WL was measured with a file under magnifying loupes (X3). Ability to measure WL was detected precisely and in acceptable range that is ± 0.5 mm of actual WL. Results: The mean value of differences between three experimental methods length and the actual WL were statistically significant (P < 0.05). EAL gave the most accurate readings out of all the experimental groups, with 100% accuracy within the acceptable range where as digital radiography gave the least accurate reading. Conclusion: The electronic method (Justy II apex locator) demonstrated significant accuracy in determining the working length.

Keywords: Apex locator, conventional, digital, radiography, working length.


How to cite this article:
Mittal R, Singla MG, Sood A, Singla A. Comparative evaluation of working length determination by using conventional radiography, digital radiography and electronic apex locator. J Res Dent 2015;3:70-5

How to cite this URL:
Mittal R, Singla MG, Sood A, Singla A. Comparative evaluation of working length determination by using conventional radiography, digital radiography and electronic apex locator. J Res Dent [serial online] 2015 [cited 2019 Dec 13];3:70-5. Available from: http://www.jresdent.org/text.asp?2015/3/3/70/168736


  Introduction Top


One of the main concerns in root canal treatment is to determine how far working files should be advanced within the root canal, and at what point the preparation and obturation should be located.[1] Over-instrumentation can cause tissue destruction, persisting inflammatory responses, and foreign body reactions,[2] whereas under-preparation or insufficient cleaning of the canal will entail the risk of leaving tissue remains within the apical region; as this tissue may be diseased, treatment may fail.[1]

The literature suggests two valid positions for apical stop preparation: At the cemento-dentinal junction (CDJ),[3] or at the minor apical foramen.[4] Root fillings terminating at the apical constriction (AC) or CDJ provide optimal healing conditions with minimal contact between the filling material and the apical tissue, thus reducing tissue destruction, persisting inflammatory responses and foreign body reactions.[2] Locating the AC and CDJ clinically is challenging because of their variable positions and topography.[5]

Various techniques have been used for determining the position of the canal terminus and to measure the working length (WL) of root canals like tactile sensation, periodontal sensitivity, moisture on a paper point and radiographs.[6]

The most popular method used so far is radiographic technique. In this method, considering that the AC lies approximately 0.5-1 mm short of the anatomical apex (Kuttler 1955), WL is determined 0.5-1 mm short of radiographic apex.[6] Conventional film-based radiography has the advantage of being a simple method with certain disadvantages such as more radiation exposure and time consuming.[7] Digital radiography, an advanced imaging technology, allows image enhancement, lower radiation exposure, and is less time consuming.[8]

Although radiography is the most commonly used diagnostic aid in endodontics, it is only able to provide a 2-dimensional image.[1] Moreover, the apical foramen used as landmark in radiographs is not always located at the anatomical apex rather; it often lies on the lingual/buccal or mesial/distal aspect.[3] These factors increase the inaccuracy and discrepancy of radiographic canal length determination.

To overcome the drawbacks of radiography, the electronic apex locator (EAL) was introduced by Custer (1918). Initially these devices had disadvantage of being influenced by the contents of the canals.[3] Over the years newer generations have been developed which can measure root canal length accurately even in highly conductive conditions, such as in the presence of blood, pus and (NaOCl).[9]

Various studies [10],[11],[12] had shown that third generation-dual frequency impedance ratio-based EALs are more accurate and out of them Root ZX has been proven to be a benchmark.[3] However, not all the third generation EALs show the similar level of accuracy.[13],[14]

As literature shows highly variable results while measuring accurate WL with these methods i.e. conventional radiography, digital radiography, and third-generation EAL, therefore the present study was planned to evaluate the accuracy of the conventional radiography, digital radiography, and a third-generation EAL (Justy II; Yoshida Dentcraft, Tokyo, Japan) individually and in comparison to each other.


  Materials and Methods Top


This ex vivo study of evaluating the accuracy of WL determination by using conventional radiography, digital radiography, and EAL was carried out in the Department of Conservative Dentistry and Endodontics, Sudha Rustagi College of Dental Sciences and Research, Faridabad, Haryana. This study was performed on 25 vital premolar teeth, scheduled for extraction in orthodontic patients. The teeth having metallic restoration, caries, root resorption, fractures, open apices, or radiographically invisible canals were excluded. Complete treatment procedure was explained to the patient and an informed consent prior to the participation in the study was obtained. A preoperative periapical radiograph with conventional radiography and digital image by a radiovisiography (RVG) (Kodak 5100; Kodak Co., Marne-La-Vallee, France) was taken for each tooth in buccolingual projection using paralleling technique. The tooth was profoundly anesthetized, followed by rubber dam isolation. Straight line access to the root canal was then established using high-speed diamond round bur and tapering fissure bur under water coolant. Then, the canal orifice was located with endodontic explorer and contents of canal were removed with barbed broach followed by irrigation with 5 mL of 1% NaOCl. After that the pulp chamber was dried gently with air and sterile cotton pellet was used to dry the tooth surface and eliminate excess irrigant, without any attempt to dry the canal.

WL for each tooth was measured by all the four methods (EAL, conventional radiography, radiovisiography (RVG), and actual WL by magnifying loupes). Buccal cusp tips of all premolars were used as reference points in all the methods.

Experimental methods

Electronic working length by EAL

First, the clip was attached to the patient's lip and a stainless steel size 15 K-file was connected to the file holder of the EAL. Then the file was advanced slowly within the canal until the visual reading showed the position of file tip at designated target, i.e., 0.5 mark ahead of APEX mark as prescribed in a user's manual. Measurement was considered suitable if instrument reading remained stable for at least 5 s. Then after establishing the EWL, the silicone stopper was adjusted to the coronal reference point and length was measured with scale in millimetres. The measuring precision was set to 0.5 mm.

Conventional radiographic working length by conventional radiography

The WL was determined on preoperative intraoral periapical radiographs (IOPA) taken by X-ray equipment operating at 8 mA and 70 Kvp (Dabi Atlante, Ribeirão Preto, SP, Brazil) using paralleling technique. A conventional E-speed X-ray film size 2 (Ektaspeed E-speed group; Kodak, Rochester, NY, USA) was placed parallel to the long axis of patients' teeth and perpendicular to the X-ray beam, maintaining a 20 cm source-object distance and 0.23 s exposure time. The distance between the source and the tooth and the tooth and the film, was standardized using X-ray positioning device(RINN XCP-ORA: Dentsply, Philadelphia street, New York, (USA).

For determining WL, Ingle's method was followed. The length of the tooth was measured on the preoperative radiograph, from the highest cusp to the root apex, and 1 mm was subtracted from this length ["safety allowance" for possible image distortion or magnification]. Then the stopper was adjusted on the instrument at this tentative WL by using endogauge and another radiograph was taken with the instrument placed in the canal with stopper at reference point. After this the difference between the end of the instrument and the end of the root was measured on the radiograph and this amount was added/subtracted to the original measured length. From this adjusted length of tooth, 1 mm was subtracted with the help of endogauge. Then the stopper was readjusted, final radiograph was taken and WL was established.

Digital radiographic working length by direct digital radiography

WL by RVG (Kodak 5100; Kodak Co.) with CCD sensor size 1 (a resolution of 14 line pairs/mm) was estimated by using Ingle's technique as used in conventional radiographic technique.

Actual working length by direct visual method

After determining the WL by the above three methods, immediately the teeth were extracted using straight elevator and required extraction forceps. Local anesthesia was not administered again as the patients were still under the effect of previously given local anesthesia. Extracted teeth were then washed with distilled water and immersed in 2.5% NaOCl for 10 min. The actual length of the tooth was determined using the same files and points of references. To measure this, endodontic file was inserted until the tip of file was just visible at the apical foramen using magnifying loupe at 3X magnification. Stopper was then adjusted to the reference point and the file was withdrawn from the canal and file length was measured on mm scale. WL was established by subtracting 1 mm from this length and recorded as actual WL (AWL).

This actual WL was compared with the working length obtained using the apex locator, conventional radiograph and RVG for individual tooth. The value was termed negative (-) or positive (+) depending upon whether the WL was shorter or longer than the AWL.

Statistical analysis

Data was analyzed statistically by Paired t-test to compare the actual WL with lengths measured by radiographs and EAL. For intergroup comparisons analysis of variance (ANOVA) and Tukey's post-hoc test were used. The range of ± 0.5 mm from actual canal length (minor foramen), which is considered to be useful guide for clinical acceptability, was also used to test accuracy in this study. Thus, ability to measure WL was detected precisely and in acceptable range that is ± 0.5 mm of actual WL. The level for accepting statistical significance was set at P < 0.05.


  Results Top


The mean WL and standard deviation of all the four methods were calculated [Figure 1]. The mean of differences between three experimental WL and the AWL were statistically significant (P < 0.05) [Figure 2]. Justy II gave the most accurate results, with a mean difference of -0.2000 [P = 0.003] from AWLm followed by conventional radiography with a mean difference of.2200 [P = 0.002] and digital radiography with a mean difference of. 3000 (P = 0.000). On intergroup comparison, there was no statistically significant difference between the groups in the determination of WL with P value 0.358 (P > 0.05). Results showed the accuracy of Justy II, conventional and digital radiographic methods for determining WL precisely was 60%, 52%, and 48%, respectively. However, accuracy of Justy II, conventional and digital radiographic methods for determining WL in range of ± 0.5 mm of actual WL (AWL) was 100%, 96%, and 92%, respectively.
Figure 1: Mean working length and standard deviation of all four methods

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Figure 2: Mean difference of values of each experimental method and direct visual method (AWL)

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  Discussion Top


Establishing an accurate WL is a basic, but critical, step in root canal debridement and preparation resulting in complete cleaning of the canal and avoiding damage to periapical tissues from over instrumentation leading to successful root canal treatment.[1] Various techniques have been used for determining the position of the canal terminus and to measure the WL of root canals with variable results.

In this study results showed that the mean difference between radiographic methods (conventional and digital) and AWL was statistically significant with mean difference of 0.2200 and 0.3000 respectively. The accuracy of digital and conventional radiographic methods for determining WL precisely was 48% to 52% and within ± 0.5 mm of AC was 92-96%, respectively. The majority of measured WLs which were not accurate appeared longer than the AWL. A possible explanation may be that the apical foramen is often located laterally rather than apicocentral. An apical foramen that is located short of radiographic apex on the facial or lingual aspect of the root makes it generally difficult to identify the position of apical foramen on the radiograph. Moreover in this study premolars, meant for orthodontic extractions, were used where apical foramen is not apicocentral in 87% of mandibular premolars and 98% of maxillary premolars, leading to overestimation.[15] The findings of present study are in agreement with the findings of Dummer et al. (1984) and Ricucci and Langeland et al. (1998) who suggested that the location and form of the AC are variable and not detected precisely by radiographs.[2],[4] Also, ElAyouti et al. (2001) estimated the frequency of overestimation of WL by radiographs and showed that the frequency of radiographic WL measurements being too long was 51% in premolars and 22% in molars. It was also suggested that even the WL ending 0 to 2 mm short of radiographic apex does not guarantee that instrumentation beyond the AC will be avoided.[16]

In contrast, Olson et al. (1991) showed that the accuracy of radiographic length determination was 78-86% in locating the apical foramen.[17] Different results can be attributed to the fact that this study was an in vitro study and the tooth position in relation to the film and the central beam can be kept constant in an in vitro study model which cannot be possible to that extent in the present study as radiographic measurements were taken in vivo. Moreover in this study, direct visual method for measuring the actual WL which is used in the present study was not used. Instead of this, for locating whether the instrument tip is at apical foramen or not, another radiograph under a stereomicroscope (X6 magnification) was taken.

In the present study, for EAL, readings were taken according to manufacturer's instructions i.e. 0.5 mark ahead of APEX mark. Although some of the authors have suggested that taking the instrument slightly long and then retracting it may increase the accuracy of readings, but in clinical use pushing the file in teeth with necrotic pulps beyond the apical foramen may lead to a transportation of bacteria and toxins into the apical tissue,[14] so this method was not taken in consideration.

In the present study, results showed that the mean difference between electronic method and AWL was statistically significant, with a mean difference of 0.2000 being the closest to AWL. The accuracy of electronic methods for determining WL precisely was 68% and within ± 0.5 mm of minor apical foramen was 100%. The majority of readings which were not accurate appeared shorter than the AWL. A possible explanation for the shorter WLs may be that the third generation EAL used in this study is based on measuring the AC and according to Dummer (1984) anatomy of AC can vary morphologically.

The findings of present study are in agreement with the findings of Hoer and Attin (2004) and Ounsi and Naaman (1999).[9],[18] Hoer and Attin (2004) showed that by the use of impedance ratio electronic devices (Justy II and Endy 5000), accurate determination of the AC was only successful in 51-64.3% of canals, although the probability of determining the area between minor and major foramen was between 81% and 82.4% of cases.[18] Ounsi and Naaman (1999) checked the reliability of impedance ratio-based electronic devices and showed that the accuracy of an electronic device in measuring AC precisely was only 50%, whereas accuracy was 84.72% when measured within a range of 0.5 mm.[9] So, these authors suggested that EALs were not capable of detecting the AC precisely whereas in case of clinically acceptable limit, i.e., ±0.5 mm of minor apical foramen, apex locator gave accurate readings.

In contrast Hor et al. (2005) evaluated the accuracy of two EALs (Justy II and Raypex 4) showed that for Justy II, readings which were not accurate appeared longer than AWL.[19] The difference in results could be due to the fact that the EAL readings were taken when the visual reading showed the position of file tip at APEX mark while in the present study reading were taken when visual reading showed the position of file tip at 0.5 ahead of APEX mark (designated target).

In contrast to present study, Martin et al. (2004) evaluated the accuracy of three EALs (Justy II, Neosono Ultima EZ, and Root ZX) and showed 80-90% accuracy.[20] The reason of high accuracy could be that in their study EAL measurements were taken in an in vitro condition instead of an in vivo condition taken in present study.

Intergroup comparison of each experimental method was done by ANOVA and Tukey's post-hoc test. On comparison of conventional and digital radiographic method, the statistical analysis revealed that there is no significant difference between conventional radiography and digital radiography. These findings are in agreement with the studies conducted by Shearer et al.,[21] Ong and Ford,[22] and Manoel Bitro et al.[23] On comparison between electronic method and radiographic methods, the statistical analysis revealed that there is no significant difference between electronic method and radiographic methods. These findings are in agreement with studies done by Lozano et al.,[1] Smadi et al.,[24] Shahi et al.,[25] and Kgiku et al.[26]

In contrast, Vieyra et al.,[27] Shanmugarag et al.,[10] and Ehsan et al.[11] compared radiographs and EALs (third generation) and showed that EALs were more accurate in measuring WL as compared to radiographs, with significant difference. Ramesh et al.[12] and Foaud [28] concluded from their study that although EALs can determine AC with accuracies of more than 90%, but cannot replace radiograph altogether and can just supplement the information obtained from radiographs.

The results of present study revealed that although there was a significant difference between experimental method and actual WL but EAL showed the most accurate reading when compared to actual WL. Similar results were found in other studies which stated that the correct use of EAL may help to reduce the risk of instrumentation beyond the apical foramen and also reduce the repeated radiation exposure by radiographs.[27],[29] But the EALs used alone without the radiographic method cannot give any information about the curvature and direction of the root canal. Thus, it can be stated that one should use the combination of radiographic and electronic method for determining the WL. The knowledge of apical anatomy or curvature by prudent use of radiographs and the correct use of EAL will assist practitioners to achieve predictable results.

 
  References Top

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Hor D, Krusy S, Attin T. Ex vivo comparison of two electronic apex locators with different scales and frequencies. Int Endod J 2005;38:855-9.  Back to cited text no. 19
    
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Lucena-Martín C, Robles-Gijón V, Ferrer-Luque CM, de Mondelo JM.In vitro evaluation of the accuracy of three electronic apex locators. J Endod 2004;30:231-3.  Back to cited text no. 20
    
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Shahi S, Rahimi S, Milani AS, Jafarabadi M, Djoorabbaf Naghsh GR. Comparison between the accuracy of NovApex apex locator and radiographs in determining radiographic apex. Iran Endod J 2011;6:65-8.  Back to cited text no. 25
    
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Vieyra JP, Acosta J, Mondaca JM. Comparison of working length determination with radiographs and two electronic apex locators. Int Endod J 2010;43:16-20.  Back to cited text no. 27
    
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Fouad AF. The use of electronic apex locators in endodontic therapy. Int Endod J 1993;26:13-4.  Back to cited text no. 28
    
29.
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    Figures

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