Dental Hypotheses

: 2016  |  Volume : 7  |  Issue : 4  |  Page : 142--146

Evaluating Electromagnetic Interference of Communication Devices with Root ZX Mini Apex Locator

Marzieh Shafieibavani1, Pedram Iranmanesh2, Foad Iranmanesh1,  
1 Department of Endodontics, Dental School, Rafsanjan University of Medical Science, Rafsanjan, Kerman, Iran
2 Department of Endodontics, School of Dentistry, Isfahan University of Medical Science, Isfahan, Iran

Correspondence Address:
Foad Iranmanesh
Department of Endodontics, Dental School, Rafsanjan University of Medical Science, Rafsanjan, Kerman


Introduction: The correct determination of working length is a critical factor in the success of endodontic treatment. Nowadays, the electronic apex locators (EALs) is more used because of their ease of use, high accuracy, and the uncertainty of other methods. Because EALs use the electronic method, it is likely that electromagnetic waves (EMWs) affect their performance. This study aims to investigate the possibility of this interference. Materials and Methods: The visual canal length (CL) of 12 maxillary incisors (Vertucci’s type I) was measured with a K-file and magnifying glass. Root ZX mini apex locator is used to measure CL in the absence/presence of EMWs in both the second (2G) and third generations (3G) of mobile communication network at the mode of ringing and conversation at direct contact and the distances of 25 and 50 cm. Results: The mean CL at presence of EMWs in all conditions and distances (by removing the conversation with 2G at direct contact group) were not significantly difference with CL and EAL and absence of investigated EMWs group (Repeated-Measures Analysis of Variance (ANOVA), P = 0.083). The indicator of EAL were unstable on apex sign at least 5 seconds for 5 teeth (41.7% of samples) in conversation with 2G at the direct contact group. Conclusion: EMWs of 2G and 3G not causes malfunctions of the Root ZX mini apex locator except conversation with 2G at the direct contact.

How to cite this article:
Shafieibavani M, Iranmanesh P, Iranmanesh F. Evaluating Electromagnetic Interference of Communication Devices with Root ZX Mini Apex Locator.Dent Hypotheses 2016;7:142-146

How to cite this URL:
Shafieibavani M, Iranmanesh P, Iranmanesh F. Evaluating Electromagnetic Interference of Communication Devices with Root ZX Mini Apex Locator. Dent Hypotheses [serial online] 2016 [cited 2021 Aug 4 ];7:142-146
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One of the key factors in the success of endodontic treatment is determining the correct working length.[1] Several approaches have been proposed for determining the working length:[2] dentist’s Knowledge of the apical anatomy, tactile sense, apical bleeding, patient response without anesthetics, and radiographic interpretation.[3] However, it has been shown that all these methods have some limitations.[4]

Because of the limitations of these methods, efforts continue to find a way to determine the exact working length. With technology advancement, usage of electronic apex locators (EALs) has raised among practitioners owing to increased accuracy and reduced exposure to radiation.[5] In comparison with radiography, the new apex locators determine not only the location of apical foramen but also the apical constrictor.[6],[7]

Root ZX apex locator from the third generation of apex locators simultaneously measures the impedances of two different frequencies (0.8 and 4 KHz)[8] and provides apex location based on the resulting quotient. This device makes it possible to measure length with high precision.[6] According to the manufacturer, Root ZX mini apex locator and Root ZX apex locator have been built using the same technology.[9]

Despite the fact that using new EALs is the most accurate measurement method, there are always concerns about the various factors that may affect their accuracy. Thus, several studies have examined the effects of various factors on the accuracy of EALs such as different irrigants, bleeding, preflaring, and file size.[10]

On the other side, with technology improvements in the late 1980s and early 1990s, inappropriate performance of some medical devices were reported due to electromagnetic interference (EMI) of different electronic devices and cell phones. Hence the usage of wireless communication devices in hospitals and medical centers were restricted.[11]

One of the very pervasive electromagnetic wave (EMW) with controversial interactions are waves used in mobile communication networks. It should be mentioned that the second-generation of cell phone (2G) or digital uses the Global System for Mobile Communications (GSM) with two frequencies,[12] and the third generation (3G) is the new generation of mobile network technology with multimedia approach based on Code Division Multiple Access (CDMA) technology. Wide-band CDMA (WCDMA), CDMA2000, and time-division synchronous CDMA (TDSCDMA) are three standards accepted by the International Telecommunication Union.[13]

Because the apex locators are electronic devices, they can be subjected to EMI. Moreover, according to the importance of the determination of the exact length in the success of endodontic therapy, this study has been performed with the aim of evaluating EMIs of communication devices with Root ZX mini apex locator.

 Material and Methods

In this in-vitro study, 12 single-canal (Vertucci’s type I) maxillary central incisors, which were extracted due to periodontal disease or severe decay, were collected. The exclusion criteria were previous endodontic treatment, calcification, open apex, internal or external resorption, root fracture, and any severe root canal curvatures.[14],[15],[16]

External root surface debris and contaminants were removed using the scaler (Dentafix, Camberley, United Kingdom). After removal of all caries and restorations, access cavity preparation was done using diamond fissure bur (DIA, Resia, Italy). In order to obtain a stable and repeatable incisal reference, crown of each tooth was cut by a diamond disc (Stoddard, Hertfordshire, United Kingdom) from 5 mm above the cementoenamel junction.[15] A #10 k-file (Dentsply, New York, United States) was used to confirm patency.[17] Then, the canal was irrigated with 1% sodium hypochlorite solution (Golrang, Tehran, Iran).[14],[16]

A code was assigned to each tooth before visual canal length measurement to blind the investigator. To measure the actual visual length,[14],[16],[17] A #15 k-file was inserted into the root canal until the file tip became visible at the apical foramen. The file was then slowly pulled back so that its tip was placed at the apical foramen. This situation was checked by observing with moving an explorer (Dentafix, Camberley, United Kingdom) on the root tip. The rubber stop was carefully adjusted to the reference point and stabilized with cyanoacrylate resin (Razi, Tehran, Iran). Then the distance between the rubber stop and the file tip was measured by a caliper (Mitutoyo, Tokyo, Japan) with 0.02 mm accuracy.

For electronic canal length measurement, roots were embedded in an alginate (Lascod, Fiorentino, Italy) model[14],[15],[16],[17] so that the first 3 mm of the cervical third was out of alginate.[15] All measurements were performed within a 2-hour interval.[17]

Before using Root ZX mini apex locator (J. MORITA Mfg. Corp, Kyoto, Japan), root canals were irrigated with 0.9% normal saline solution (Daroopakhs, Tehran, Iran).[18] Excess irrigating solution was removed with a small cotton ball from access cavity such that only the canal was left wet. A #15 k-file was inserted[19] into the root canal. Then the lip electrode was immersed in the embedding media and the other electrode was connected to the file. The file was slowly inserted into the apical direction until the OVER sign appeared on the device’s display and then gently retracted to the “ZERO” or “APEX” signal.[16] Measurements were identified if the device stayed stable for at least 5 seconds.[15] Afterward, the rubber stop was carefully adjusted to the reference point and stabilized with cyanoacrylate resin (Razi, Tehran, Iran) and distance between the stop and file tip was measured by caliper with 0.02 mm accuracy.

The communication device used in this experiment was Galaxy Note II GT-N7100 (Samsung, Bac Ninh, Vietnam), using two different setting. The devise was set on the network “GSM only” for 2G and “WCDMA only” for 3G. Among the possible places to perform the test using the “OpenSignal” application version 2.2.2 (OpenSignal, London, United Kingdom), a place with the weakest received communication signal was selected.

Cell phone on active mode (ON) were placed at direct contact 25 and 50 cm from the EAL, and the canal length with EAL was measured (at the condition mentioned above) for the following conditions.

During the phone ringing (in 2G and 3G); measurements in all cases was started after the phone began ringing and completed before the ringing ended. During the conversation with the same phone far from test location (in 2G and 3G); measurements in all cases was started after and completed before the call ended.

Other mobile communication features such as Bluetooth, Wi-Fi, Mobile data, and Global Positioning System (GPS) were disabled throughout the duration of the experiments.

At the time of the instability of apex locator indicator on the apex sign, at least 1 minute was determined to achieve the stability of device indicator. The measurement process was repeated once again in these cases.

Data were analyzed by the Statistical Package for the Social Sciences (SPSS) version 21 (IBM Corp. Released 2012. IBM SPSS Statistics for Windows, Version 21.0. Armonk, NY: IBM Corp.) and the following tests were used: Paired t-test, Repeated-Measures Analysis of Variance (ANOVA) and Fisher’s exact test. The significant level was set to 0.05.


CLs of 12 maxillary single canal central incisors were compared at different conditions. The mean and standard deviation (SD) of visual canal length to the apex was measured 18.52 ± 1.11 mm and the mean and SD of electrical measurement method in the absence of investigated EMWs was 18.51 ± 1.10 mm. (paired t-test, P = 0.894).

The mean CL with EAL in the presence of EMWs at different conditions/distances is investigated. The conversation with 2G at direct contact group show the higher CL whereas the conversation with 2G at 25 cm group show the lower CL (18.46 ± 1.24 and 18.19 ± 1.70, respectively). The mean CL with EAL in the absence and presence of EMWs in all condition and distance were evaluated. Mauchly’s Test of Sphericity showed that the assumption of sphericity had been violated (P < 0.05), and therefore, a Greenhouse-Geisser correction was used. There was no significant effect of EMWs on EAL (P = 0.083) [Table 1].{Table 1}

The indicator of EAL were untable on apex sign at least 5 seconds for 5 teeth (41.7% of samples) in conversation with 2G at the direct contact group; however, in the absence of investigated EMWs group, EAL was stable in all samples (100%). (Fisher’s exact test, P = 0.037).


Ease and determining the length with the EALs, as well as the higher accuracy rather than the conventional radiographic method,[5] has led to the popularity of using these devices among practitioners. Increased use of EALs raise concerns regarding the impact of various factors on their accuracy. Second and third generations of cell phones are currently most commonly used communication frequencies in Iran. These waves are also the most common form of electromagnetic radiation in the environment, including dental offices. The growing use of communication networks caused concerns regarding interference with other electronic devices. Such interactions have been proved by some previous investigations.[12] In the present study, the interaction of these waves with EALs were evaluated. The EMI likelihood increases while the mobile phone is ringing,[23] and the wave emission is also intense during the calling mode.[24] Inspired by other studies[12],[20] the distances of zero (direct contact), 25, and 50 cm were selected.

The indicator of EAL were unstable on apex sign for 41.7% of sample in conversation with 2G at direct contact group; however, in the absence of investigated EMWs group, EAL was stable in all samples. It showed that talking with 2G in direct contact with Root ZX mini apex locator may interfere with the operation of the device. This result is consistent with the finding that the EMWs radiation is very high in the conversation condition, particularly for the 2G connection compared to 3G.[24]

The only available study on the EMI with apex locators is proposed by Hurstel et al.[24] They did not observe any difference in electrical CL with and without of 2G and 3G EMWs. Similary, the results of present study showed no significant difference in the canal length with and without presence of investigated EMWs, except in the case of conversation with 2G at direct contact 2G at direct contact. This may suggest that cell phones do not have significant interferences with apex locators. However, the deferences between the Hurstel et al.[24] study and the present study should be considered.

The accuracy of EALs could affected by foramen diameter.[25] The maxillary central incisors were used in present study whereas Hurstel et al.[24] used premolar teeth. Premolar teeth have the most and the largest accessory foramens as well as the most complicated apical morphologic makeup. It would be a possible reason for the failure of root canal therapy in premolar teeth.[26]

Guerreiro-Tanomaru’s[27] study in 2011 showed that alginate is a better test environment in comparison with saline. Meanwhile, Lipski et al.[28] did not observe any difference between the measured electrical CL in the mouth and alginate test environment. In addition to periodontium simulation, a gel-like consistency, simplicity, ease of use,[29] easy access, and cost-effectiveness are the other reasons that the alginate was chosen as the embedding media for the present study. In contrast, Hurstel et al.[24] used saline.

Hurstel et al.[24] used Apple iPhone 5 for 3G and LG KP100 for 2G in their study. Conversely, in order to eliminate the influence of cell phone models, one model of phone (Samsung Galaxy Note II GT-N7100) in two different network modes of GSM only (2G) and WCDMA only (3G) was used in present study.

In present study, OpenSignal Software was used to obtain a place with minimal received signal. Hereby, the cell phone interferences at the maximum output power or close to it. Hurstel et al.[24] conducted their experiments in a place with a weak received, while the method of determining signal strength was unknown in their study. For future studies, using other generation of mobile networks and other EALs are recommended.


EMWs of 2G and 3G not causes malfunctions of the Root ZX mini apex locator except conversation with 2G at the direct contact.

Financial support and sponsorship

The work was the undergraduate thesis and was financially supported by vice Chancellery of Research and Technology of Rafsanjan University of Medical Science, Rafsanjan, Kerman, Iran (Grant #468).

Conflicts of interest

There are no conflicts of interest.


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