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 Table of Contents  
Year : 2019  |  Volume : 9  |  Issue : 1  |  Page : 32-36

New insight into the role of electronic apex locators in detecting simulated horizontal root fractures: An In vitro study

Department of Conservative Dentistry and Endodontics, Karnavati School of Dentistry, Gandhinagar, Gujarat, India

Date of Web Publication4-Jan-2019

Correspondence Address:
Mukti M Shah
No. 43, Gangeshwar Society, Opp. Best High School, Bhairavnath, Ahmedabad - 380 008, Gujarat
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/AIHB.AIHB_41_18

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Aim and Objectives: The aim of this study is to check the accuracy of two different electronic apex locators (EALs): Canal Pro and Root ZX – in locating simulated horizontal root fractures (HRFs). Materials and Methods: Forty-five recently extracted, single-rooted, human permanent teeth were selected for the study. Endodontic access cavity was prepared, and canal patency was checked using no. 10-K file. Horizontal fractures were simulated using 0.2-mm thick diamond disk in coronal, middle and/or apical third of root by operator one, until half of the canal was exposed circumferentially. Using both the apex locators, all the fractures were detected by the second operator to confirm the accuracy of EALs. The actual length of the fractures was then measured under ×2.5 magnification, and results were subjected to statistical analysis. Results: Results were analysed using the one-way analysis of variance and Tukey's post hoc test, and the differences between all the test samples were analysed. All the measurements were compared to the actual values separately. A statistically significant difference was determined at 95% confidence level (P ≤ 0.05). Conclusion: Investigated both the EAL are capable of detecting simulated HRF and that the Canal Pro showed a higher accuracy rate.

Keywords: Canal Pro, electronic apex locator, horizontal root fractures, Root ZX

How to cite this article:
Shah MM, Parekh VV, Patel NJ, Dodiya PV, Chauhan DH. New insight into the role of electronic apex locators in detecting simulated horizontal root fractures: An In vitro study. Adv Hum Biol 2019;9:32-6

How to cite this URL:
Shah MM, Parekh VV, Patel NJ, Dodiya PV, Chauhan DH. New insight into the role of electronic apex locators in detecting simulated horizontal root fractures: An In vitro study. Adv Hum Biol [serial online] 2019 [cited 2020 Aug 15];9:32-6. Available from: http://www.aihbonline.com/text.asp?2019/9/1/32/249520

  Introduction Top

Root fractures in permanent teeth are uncommon injuries and account for only 0.5%–7% of dental traumas.[1] Root fracture can be a consequence of dental trauma, which leads to a complex injury to the cementum, dentin, pulp and the periodontal tissues.[2] Incomplete root fractures whether vertical, horizontal or oblique in nature are often one of the most difficult cases to diagnose clinically and radiographically in clinical endodontic practice.[3] Management of root fractures is clinically challenging as it may involve interdisciplinary/multidisciplinary treatment approach. They are broadly classified into horizontal/transverse root fractures and vertical root fractures.

Horizontal root fractures (HRFs) present an interesting diagnostic and treatment challenge for the endodontist. These types of fractures comprise only 3% of all dental injuries[4] and are at times difficult to diagnose and treat along with having unpredictable prognosis. HRF may be located either in the apical third, middle third or the cervical third of the root, which primarily dictates the treatment planning and prognosis of the tooth.[5] Clinical diagnosis along with radiographic examinations falls short in truly detecting presence or absence of root fractures, because of the varied directions and angulations of propagated fractures.[3],[6]

Electronic apex locators (EALs) have been used in clinical practice for more than 40 years as an aid to determine the root canal working length. All modern EALs are proved to detect root perforations and lateral canals within a clinically acceptable limit.[7],[8] It has been postulated that apex locators could be used to detect the fracture position, if it communicates with the periodontal membrane.[9] While introducing the file within the canal, any fracture site that communicates with the periodontium, will be detected as a new connection between the canal and periodontium and be read as 'apex' on the digital display monitor of apex locator.[3],[10]

The objectives of this in vitro study were to evaluate the effectiveness of two different apex locators in detecting HRFs simulated at different levels and to prove the role of apex locators as an additional clinical diagnostic aid in detecting fractures and their exact location so as to help the clinician to decide the best treatment option for the particular tooth.

  Materials and Methods Top

Two EALs were used in this study: Root ZX (J. Morita Co., Tokyo, Japan)[11] and Canal Pro (Coltene Whaledent, Switzerland).[12]

A total of 45 extracted intact, straight, single-rooted human permanent teeth with completely formed roots were used in the study. Teeth were preserved in 10% formalin for 24 h and then in 0.9N saline till further use. All the teeth were examined under stereomicroscope, and teeth with sound roots and no evidence of root resorption or fractures were confirmed.

The teeth were decoronated at cementoenamel junction using water-cooled diamond disk, so as to prepare flat uniform horizontal surfaces, and endodontic access cavity was prepared using Endo Access Bur No. 2 (Dentsply). To assure that every specimen was usable and all canals were patent, working length (up to apical constriction) was determined with an EAL using a size 10-K file (Dentsply, Tulsa, Okla) along with ethylenediaminetetraacetic acid as the chelating agent. Total 45 samples were divided into three groups (n = 15 each) depending on the level of HRF simulation. HRFs were simulated in Group A – coronal third (n = 15), Group B – middle third (n = 15) and Group C – apical third (n = 15), in all the samples using a 0.2-mm thick diamond disc, until half of the canal was exposed circumferentially, by operator no. 1. After fracture simulation, all root canals were dried with absorbent paper points. As suggested by Kaufman et al., the teeth along with the lip clip of the apex locator were embedded in an alginate model.[13] The alginate was continuously bathed with water for maintaining the conductivity of the medium. First, the fractures in all the samples were detected using the newer generation apex locater (Canal Pro) with its lip clip embedded in the alginate model. The 25-K file was gradually advanced down in the canal without excessive force until the display of apex locator indicated the word 'APEX'. Once the apex was indicated, the file stopper was placed adjacent to the flat coronal surface. The file was removed, and the distance between the rubber stopper and the file tip was measured with a digital Vernier calliper. Similarly, the readings were taken with the third-generation apex locater (Root ZX) for all the samples. All the readings were carried out by operator no. 2, who was kept blind about the fracture locations. This was done to avoid biased readings and to ensure standardisation of the technique.

After recording the lengths of the simulated fractures, using both EALs, the samples were removed from the alginate model, and the fractures were completed with water-cooled diamond disc to obtain the actual fracture length measurements. Remnants of pulp tissue from the fractured fragment were removed.[14] The real fracture lengths (RFLs) were then measured using a size 40-K file (Dentsply, Tulsa, Okla) under ×2.5 magnification, and with these RFL readings, the readings of the two EALs were compared, allowing a tolerance of 0.5 mm. Measurements were calculated and those not within these limits were considered as unacceptable.

Statistical analysis

The one-way analysis of variance and Tukey's post hoc test was used to determine the differences between all the test samples. HRFs were analysed and compared to the actual values separately. Closeness of the Canal Pro andRoot ZXmeasurements to the actual length was compared by the Chi-square test, based on their deviations from the actual lengths. A statistically significant difference was determined at 95% confidence level. All statistical procedures were carried out with SPSS version 20 (SPSS Inc., Chicago, IL, USA), and P ≤ 0.05 was considered significant.

  Results Top

The length measurements obtained with both the apex locators were analysed and the accuracy was compared with RFLs observed under ×2.5 magnification. For all three groups, the mean values (mm), standard deviations and minimum and maximum values were calculated for the Canal Pro and Root ZX apex locators as well as for the actual measurements. In Groups 1, 2 and 3, statistically non-significant results were found between two apex locators. The differences between Canal Pro and actual, Root ZX and actual and Canal Pro and Root ZX were then calculated and used in the statistical analysis. Results are shown in [Table 1] and [Table 2], respectively.
Table 1: Statistical analysis using one-way analysis of variance test to compare the accuracy of both the apex locators

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Table 2: Multiple comparisons

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  Discussion Top

Root fractures have been marked as one of the most notorious injuries for a tooth, because they exhibit inadequate signs and symptoms and are often difficult to diagnose as well as to treat. Incomplete root fractures located at any direction whether vertical, horizontal or oblique are often among the most difficult cases to diagnose clinically and radiographically.[3]

The factors which affect the type and location of fracture are age of patient, amount of force and direction of blow.[14] HRFs may be located either in the apical third, middle third or the cervical third of the root, which primarily dictate the treatment protocol and eventual fate of the tooth. Although the outcome of a HRF is generally favourable (60%–80% cases), many complications such as pulpal necrosis, root resorption and canal obliteration can arise.[15]

To diagnose the root fractures, the periodical clinical and radiographic evaluation becomes necessary[3] which includes, to evaluate mobility, the displacement of the coronal segment, the presence or absence of tenderness on palpation of the soft tissues and percussion of the teeth in question.[16] Accurate radiographic diagnosis becomes difficult if the root fracture is oblique, making its interpretation on the radiograph difficult. Furthermore, a number of factors influence the radiographic accuracy such as tooth inclination, position and angulation of X-ray beam and superimposition of the anatomical structures.

The main purpose of this in vitro study was to evaluate the accuracy of two different EALs in detecting simulated HRFs. It has been suggested that EALs works on the principle of electricity rather than the biologic properties of the tissues involved.[17] From a theoretical point of view, EALs would mark the first zone having periodontal communication as the 'APEX'. Although this periodontal communication could be a fracture, a fissure, a perforation or a lateral canal.[10]

In the present study, root fractures were simulated with a diamond disc, producing incomplete fractures of approximately 0.2-mm thickness. Clinical situations may differ from this, which are probably narrower or of different shapes or may be oblique. In this study, three different locations of HRFs (coronal, middle and apical) were simulated and two different EALs were evaluated to observe whether any discrepancy existed in the detection of a root fracture. Clinically, it is more important to diagnose the exact location of a fracture rather than its mere presence as this can influence the treatment options and prognosis of the teeth.[16]

Accuracy of EALs was questionable while using them for in vitro study, because human periodontium was excluded. To overcome these drawbacks of EALs, many experimental models have been proposed. Kaufman et al. in 1997 developed alginate model, which is used in the current study. Alginate mimics well the electric impedance of human periodontium (Kaufman et al. 1997) and thus is a good medium to establish the necessary electric circuit for a correct EAL measurement.

In the current study, we compared third-generation apex locater (Root ZX)[18] and newer generation apex locater (Canal Pro)[12] for their accuracy in detecting the simulated HRFs at different levels. The Root ZX, third-generation apex locater, works on the principle of dual frequency and comparative impedance, as described by Kobayashi and Suda. The Root ZX works by simultaneous measurements of two impedances at two frequencies by ratio method.[19],[20] Canal Pro is a sixth-generation apex locator which, unlike the other apex locaters, only uses one frequency at a time that eliminates the need for filters that separates the different frequencies and helps eliminate the noise inherent in the filters and thus increases the accuracy.[12] A number of in vitro and in vivo studies have been done to check accuracy of different EALs in locating HRFs, but till date, there is not a single documented study in which Canal Pro is being used. Moreover, a very few documented studies are there in which accuracy of Root ZX is checked for detecting simulated HRFs.

Azabal et al. (2004) found EAL Justy II to be more accurate in determining simulated HRFs than vertical root fractures.[10] Ebrahim et al. (2006) evaluated in vitro the accuracy of three different apex locaters in detecting simulated horizontal and vertical root fractures; they found that the EALs tested were accurate in the detection of HRFs.[20] Ozgur Topuz et al. (2008) compared the accuracy of two apex-locating handpieces in detecting simulated HRFs and found that Tri Auto ZX was more successful than TCM Endo V in detecting the simulated horizontal fractures[3] Fernando Goldberg et al. (2008) evaluated the ability of four EALs to determine the location of simulated horizontal oblique root fractures, and the results found that Root ZX showed unacceptable measurements as compared to Propex and NovApex.[21] Beri and Matariya compared three EALs for detecting the location of simulated oblique fractures, and the results of this study showed that at 0.5-mm tolerance value, Root ZX showed 86.6% accuracy.[15] Xi et al. evaluated the accuracy of Root ZX in detecting simulated HRFs. They concluded that Root ZX lacks diagnostic value for HRFs without soft-tissue ingrowth but provides preferable veracity for HRFs with soft tissue in growth.[22] Thaore et al. (2016) conducted a study to check the effectiveness of two apex locators in detecting simulated HRFs. The results of this study found that both the EALs, detected fracture location with approximately 50% accuracy at 0.5-mm tolerance level, but at 1.0-mm tolerance level, Root ZX showed 90% accuracy and Propex II showed 70% accuracy.[5]

The results of our study conclude that both the Canal Pro and Root ZX are able to detect the fracture locations. These results are in agreement with those of Azbal et al.,[10] Ozgur Topez et al.[3] and Fernando Goldberg et al.,[21] who evaluated that the EALs were able to detect simulated HRFs. Although Shabahang et al.[23] and Fernando Goldberg et al.[24] suggested that 1.0-mm tolerance be considered as clinically acceptable, in current study, measurements attained with the 0.5-mm tolerance value are considered highly accurate. Errors may arise in the direct determination of the fracture length or there might be the difficulty in the visual control of the relation between the rubber stopper/reference point, rubber stopper/digital Vernier calliper scale and file tip/digital Vernier calliper scale. Sometimes, it is also challenging to visualise the exact point where the tip of the file reached the cervical border of the foramen, even with magnification.[25] As shown in [Figure 1], results of this study show that at 0.5-mm tolerance level, Canal Pro showed 93.3% accuracy in coronal, 66.7% accuracy in middle and 86.7% in apical third and Root ZX showed 80.0% accuracy in coronal, 46.7% in middle and 66.7% in apical third groups. Both the EALs are able to detect simulated HRFs with accuracy, but Canal Pro showed a higher accuracy rate in detection of simulated HRFs.
Figure 1: Percentage accuracy of both the electronic apex locators for fracture detection in coronal, middle and apical groups with 0.5-mm tolerance value.

Click here to view

  Conclusion Top

Within the limitations of this study, it can be concluded that the investigated both EALs are capable of detecting HRFs at all the levels. They also determine the working length of the coronal root segment in a high percentage of teeth with simulated HRFs at a ± 0.5-mm tolerance. Nevertheless, further research needs to be conducted to confirm the role of EALs in cases with root fractures. Understanding and overcoming the minor discrepancies between EAL readings and the RFL may make EALs an important diagnostic tool in accurately detecting the location of HRFs.

The results of the present study and some previous studies also indicate that, even in fully controlled in vitro study conditions, there is some inconsistency in EAL measurements.[24],[26],[27] It should be emphasised that the results obtained in this in vitro study cannot be directly simulated to the clinical situation but can provide an objective examination of a number of variables that are not practical to test clinically.


I acknowledge the faculty of the department, involved in this study for their guidance and support.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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Topuz O, Uzun O, Tinaz AC, Bodrumlu E, Görgül G. Accuracy of two apex-locating handpieces in detecting simulated vertical and horizontal root fractures. J Endod 2008;34:310-3.  Back to cited text no. 3
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Goldberg F, Frajlich S, Kuttler S, Manzur E, Briseño-Marroquín B. The evaluation of four electronic apex locators in teeth with simulated horizontal oblique root fractures. J Endod 2008;34:1497-9.  Back to cited text no. 6
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  [Figure 1]

  [Table 1], [Table 2]


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