Download Document

Basic Research—Technology
Evaluation of Interference of Cellular Phones on Electronic
Apex Locators: An In Vitro Study
Preena Sidhu, MDS,* Swapnil Shankargouda, MDS,† Daniel DevaPrakash Dicksit, MPH,*
Haydar Majeed Mahdey, MDS,* Danish Muzaffar, MDS,* and Shelly Arora, MDS*
Abstract
Introduction: Use of mobile phone has been prohibited
in many hospitals to prevent interference with medical
devices. Electromagnetic radiation emitted from cellular
phones might interfere with electronic working length
determination. The purpose of this in vitro study was
to evaluate the effect of a smart phone (Samsung Galaxy
Note Edge) on working length determination of electronic apex locators (EALs) Propex II and Rootor.
Methods: Fifteen intact, non-carious single-rooted
teeth were decoronated at the cementoenamel junction.
Visually, working length was determined by using a
#15 K-file under stereomicroscope (20). The effect of
cellular phones on electronic working length (EWL)
was determined under 2 experimental settings: (1) in
a closed room with poor signal strength and (2) in a
polyclinic set up with good signal strength and 5 conditions: (1) electronically, without cellular phone in room;
(2) electronically, with cellular phone in physical contact
with EAL; (3) electronically, with mobile phone in physical contact with EAL and in calling mode for a period of
25 seconds; (4) electronically, mobile phone placed at a
distance of 40 cm from the EAL; and (5) electronically,
mobile phone placed at a distance of 40 cm and in calling mode for a period of 25 seconds. The EWL was
measured 3 times per tooth under each condition. Stability of the readings was scored from 1 to 3: (1) good
stability, (2) stable reading after 1 attempt, and (3) stable reading after 2 attempts. The data were compared
by using analysis of variance. Results: The EWL measurements were not influenced by the presence of
cellular phone and could be determined under all experimental conditions. Conclusions: Within the limitations
of this study, it can be concluded that mobile phones do
not interfere with the EWL determination. (J Endod
2016;42:622–625)
Key Words
Cellular phone, electromagnetic interference, electronic
apex locator, working length determination
R
oot canal therapy is an integral part of dental practice. The success of root canal
therapy depends on various factors among which correct working length estimation is a crucial step. Electronic apex locators (EALs) have been used worldwide for
working length determination. These devices can help reduce treatment time and radiation dose to the patient (1). Various factors such as correct usage, presence of
irrigants, vital or necrotic pulp, inflammatory exudate, and obturating material
(2–7) in the root canal, contribute to the accuracy of EALs. Moreover, studies
have shown that EALs provide accurate working length estimation when compared
with the radiographic method (6).
It is known that electromagnetic radiation emitted from devices such as cellular
phones, iPods, dental devices such as electronic pulp testers, electrosurgery units,
and ultrasonic scalers can interfere with the function of implanted cardiac pacemakers
in patients with implanted cardiac devices (8–10). Electrical energy from these dental
devices can travel down the lead wires and can induce ventricular or atrial fibrillation
and reprogram the cardiac device (11). Studies have reported that cellular phones can
inhibit the function of a pacemaker, and this depends on the distance between the pacemaker and the electronic device, power output of the electronic device, type of pacemaker, age of pacemaker, and model of the cellular phone (12–14). It is suggested
that the use of cellular phones should be restricted in hospitals because
electromagnetic interference (EMI) caused by cellular phones can interfere with
functions of medical devices (15). Allowing usage of cellular phones in non-patient
areas, restrictions in clinical areas, cellular phone safe wards, and use of distance
greater than 1 m from all medical equipment are some precautions taken to prevent
this interference (15, 16).
A dental office has no such limitations for the use of cellular phones in dental operatory. Cellular phones are used by the dentist, dental surgery assistants, and patients
in close proximity to dental devices. The technical support documents of EALs such as
Root ZX (J Morita Corp, Tokyo, Japan), Propex II (Dentsply Maillefer, Ballaigues,
Switzerland), and Rootor (Meta Biomed, Cheongwon-gun, Korea) state that EMI
from portable and mobile radiofrequency communications equipment such as cellular
phones can cause interference with accurate reading of the EAL and should not be used
close to any part of the EAL. There is limited evidence base that can help a dental practitioner come to a decision whether mobile phones can be used in close proximity to
EALs and whether these devices can have any effect on the electronic working length
(EWL) determination.
This in vitro study aimed to evaluate the reliability of EALs (Propex II and Rootor) when placed in contact and in close proximity with a smart phone (Samsung Galaxy Note Edge; Samsung Electronics, Suwon, Korea) in different experimental
conditions.
From the *Faculty of Dentistry, SEGi University, Jalan Teknologi, Kota Damansara, Selangor, Malaysia; and †KLE University VK Institute of Dental Sciences, Jawaharlal
Nehru Medical College Campus, Karnataka, India.
Address requests for reprints to Dr Preena Sidhu, Faculty of Dentistry, SEGi University, Jalan Teknologi, Kota Damansara, 47810 Petaling Jaya, Selengor, Kuala
Lumpur, Malaysia. E-mail address: [email protected]
0099-2399/$ - see front matter
Copyright ª 2016 American Association of Endodontists.
http://dx.doi.org/10.1016/j.joen.2015.12.027
622
Sidhu et al.
JOE — Volume 42, Number 4, April 2016
Basic Research—Technology
Materials and Methods
Dental Samples
Fifteen single-rooted teeth with 1 canal and mature apices were
selected for this study. Roots were examined under magnification (Leica
Microsystems, Wetzlar, Germany) with a magnification of 20, and
roots with carious lesions, fractures, resorptions, immature apices,
or any other anatomic irregularities were excluded. The teeth were
sectioned at cementoenamel junction for simplified access to root canal
and to obtain a reproducible reference point. The sectioned teeth were
stored in distilled water at 4 C for further use.
EAL
Two different EALs were used in this study:
1. The Propex II (Dentsply Maillefer, Ballaigues, Switzerland), a
multifrequency-based EAL that records the signals of 2 alternating
currents of 0.5 kHz and 8.0 kHz
2. The Rootor (Meta Biomed, Cheongwon-gun, Korea), a multiple frequency EAL that uses 2 frequencies of 0.5 kHz and 5 kHz
Cellular Phone
Samsung Galaxy Note Edge, a 4G LTE (Long-Term Evolution)
multiband android smart phone used with a network provider Maxis
Communications (Berhad, Malaysia), was used in this study.
Experimental Setting
The experiment was carried out in 2 different settings, one in a
closed room (9 9 feet) and the other in a dental polyclinic
(26 40 feet) in a university setting that has cubicles (9 9 feet),
to record whether the EWL differed between the 2 settings:
1. In a closed room with weak signal strength and where Bluetooth, WiFi, and General Packet Radio Service (GPRS) were inactivated:
No phone in the room (control group)
Phone placed in physical contact with EAL in standby mode
Phone placed in physical contact with EAL and in calling mode for
a period of 25 seconds
Phone placed at a distance of 40 cm from the EAL in standby
mode
Phone placed at a distance of 40 cm and in calling mode for a
period of 25 seconds
2. In a dental polyclinic with cubicles with good signal strength where
Bluetooth, Wi-Fi, and GPRS were activated:
Dental students and personnel carrying cellular phones with
them in standby mode in vicinity of the cubicle (control group)
Phone placed in physical contact with EAL in standby mode
Phone placed in physical contact with EAL and in calling mode for
a period of 25 seconds
Phone placed at a distance of 40 cm from the EAL in standby
mode
Phone placed at a distance of 40 cm and in calling mode for a
period of 25 seconds
the file tip was just visible at the apical foramen under the stereomicroscope (Leica Microsystems) with a magnification of 20. The silicone
stop was placed at the reference point. The distance from the base of the
silicone stop to the file tip was measured with an endodontic ruler
(Dentsply Maillefer USA, Tulsa, OK). The lengths were measured to
an accuracy of 0.25 mm. The measurements followed a random
sequence, each measurement was repeated 3 times, and the mean value
was calculated.
Determination of EWL
The EWL was established by using an experimental model
described by Hurstel et al (17). Two holes were perforated in the screw
cap of a plastic container, and the tooth along with the lip clip of the EAL
was inserted through the screw cap (Fig. 1). The plastic container was
filled with 0.9% NaCL solution, and the apical and middle thirds of the
tooth were inserted into it. The tooth was irrigated with 2.5% NaOCl, and
EWL was calculated in the experimental settings described above. The
file tip with the previously calculated length was inserted into the tooth,
and the file clip was attached. The file was pushed beyond the 0 reading
on the EAL display and withdrawn slightly until the 0 reading was displayed indicating apical patency. This reading was confirmed by the
audible signal emitted from the EAL. The file stop was adjusted, and
this length was recorded as EWL.
A total of 945 measurements were recorded and tabulated, and results were compared for statistical significance.
To determine the stability of EWL reading, the following scores
were used:
1. Immediate and clear audible signal emitted from EAL for a period of
5 seconds
2. Audible signal emitted from EAL for a period of 5 seconds but after 1
attempt
3. Audible signal emitted from EAL for a period of 5 seconds but after 2
attempts
Background noise (sign of interference) between the devices was
also noted.
Statistical Analysis
Data were analyzed by using two-way repeated-measures analysis of variance followed by Bonferroni multiple post hoc procedure.
The statistical significance was set at 5% level of significance
(P < .05).
All the experiments were performed in the same place to ensure
accurate replication of the results.
Length Determination under Microscope
After access opening and verification of canal patency, #10 K-file
(Mani Inc, Tokyo, Japan) was used to prepare the glide path. Pulp tissue
was removed from the canal by using #10 K-file and 2.6% NaOCl. A #15
file (Mani Inc) fitted with a rubber stop was inserted into the canal until
JOE — Volume 42, Number 4, April 2016
Figure 1. Experimental model connected to the electronic apex locator with
cellular phone placed in physical contact with the electronic apex locator.
Cellular Phones and Apex Locators
623
Basic Research—Technology
TABLE 1. Mean Values of Working Length for Each Condition
15.3 1.1
Cell phone in different conditions
No phone
Mobile phone in standby
Mobile phone ringing
Mobile phone at a distance of 40 cm
Mobile phone ringing at distance of 40 cm
Cell phone in different conditions
No phone
Mobile phone in standby
Mobile phone ringing
Mobile phone at a distance of 40 cm
Mobile phone ringing at distance of 40 cm
Working length under microscope
Working length measured by using
Propex II apex locator
Working length measured by using
Rootor apex locator
Closed room
14.9 0.95
14.9 0.98
14.9 1.07
14.9 1.07
14.9 1.07
Closed room
14.8 1.01
14.8 1.03
14.8 1.03
14.8 1.03
14.8 1.03
Polyclinic
14.9 0.95
14.9 0.98
14.9 1.07
14.9 1.07
14.9 1.07
Polyclinic
14.8 1.01
14.7 1.03
14.7 1.03
14.7 1.03
14.7 1.03
EMI between cellular phones and medical devices generally occurs only when the cellular phones are in proximity to the medical devices (18). The results of this study show that there is no correlation
between cellular phone use and EWL determination. Under all the
experimental conditions the EAL showed good reliability and stability.
This study concluded that presence of cellular phone in close proximity
or at a distance from the EAL does not influence the readings of EALs.
Thus, cellular phones can be used in a dental operatory during root canal therapy without the risk of EMI between cellular phone and EAL.
In vitro studies have used alginate, agar agar, gelatin, and saline to
simulate the root surrounding tissues in EWL determination (19, 20).
Therefore, saline was used as electroconductive material in this study.
Teeth were horizontally sectioned at the cementoenamel junction for
obtaining reproducible reference points and were mounted in a
plastic container filled with 0.9% NaCl until the root was soaked in
the solution. Irrigants are used in endodontics for their antimicrobial,
tissue dissolving, and lubrication properties. Studies have shown that
NaOCl can be safely used with EALs in working length determination
(21). Hence, 2.5% NaOCl was used as a canal irrigant in this study. Previous studies have reported that Propex II and Rootor can accurately
locate the major foramen (20, 22), which is similar to the findings in
our study.
Different experimental settings were used in this study. In experimental setting 1, Wi-Fi, GPRS, and Bluetooth networks were inactivated to prevent any electronic interference. The experiment was
carried out in a closed room to prevent interference from other
cellular phones. Furthermore, a room with poor signal strength was
selected to induce the mobile phone to transmit at maximum power,
thus increasing the risk of EMI because cellular phones control output
power depending on the availability of the nearest cell base station
(23). Experiment 2 was conducted in a polyclinic with good signal
strength where Wi-Fi, GPRS, and Bluetooth networks were activated,
and the dental personnel carried cellular phones, mimicking a dental
operatory in a realistic scenario.
Because the distance between 2 electronic devices can influence
EMI (16, 24), different distances between the cellular phone and the
EAL were tested in this study. The recommended safety distance
between a cellular phone and medical device for a Global System for
Mobile Communication (GSM) 900 MHz cellular phone is 70 cm, for
a GSM 1800 MHz cellular phone the safety distance is 5 cm (16),
whereas for GPRS cellular phones, a safety distance of 1 m is recommended between the cellular phones and medical devices (25). Samsung
Galaxy Note Edge can be considered a GSM 900 MHz multiband phone
and can transmit network frequencies of 900 MHz and 1800 MHz. Also
for the present study, GPRS was activated with the existing GSM network.
Because the ideal distance between a dental operator and a patient is
similar to that of reading a book (26), a distance of 40 cm between
the apex locators and the cellular phone was used in this study.
Because the wave emission is intense during the calling mode of
the cellular phone (17), the calling mode was used to maximize the
chances of detecting EMI. The interference between cardiac pacemakers and cellular phones is not time-dependent. A stimulus either
does or does not interfere with the pacemaker (27). Therefore, a stimulus of 25 seconds (phone in calling mode) was deemed satisfactory for
the purpose of this study.
According to Gomez et al (28), EALs can interfere with the activity
of pacemakers if the EAL is placed close to the tip of the pacemaker
TABLE 2. Two-way Repeated Analysis of Variance (tests of within-subjects
effects) for Propex II EAL
TABLE 3. Two-way Repeated Analysis of Variance (tests of within-subjects
effects) for Rootor EAL
Type III
Partial
sum of
Mean
F
P
eta
squares df square value value squared
Type III
Partial
sum of
Mean
F
P
eta
squares df square value value squared
Results
Three readings were taken for each tooth, and averages of the
readings were tabulated and compared for mean and standard deviation
under the different conditions. It was found that in a closed room
among the different apex locators, there is no significant change in measurement of readings when compared with mobile phone in different
conditions (P > .05). However, there is a minimal change in measurement when the tests were performed in a polyclinic setting with Rootor
EAL. There is no significant change in Propex II EAL in both closed room
and polyclinic (P > .05) (Table 1). No statistically significant differences were recorded between the different groups (Tables 2 and 3)
Under all the experimental conditions, the EAL readings were stable (none scored 2 and 3 on the 945 EWL measurements), and no background noise was detected between the 2 electronic devices.
Discussion
Source
Groups
Time
Groups * Time
0.00
0.01
0.00
1
5
5
0.00
0.00
0.00
*Comparison of the interactions of groups and time points.
624
Sidhu et al.
—
—
1.0000 .4240
—
—
—
0.0670
—
Source
Groups
Time
Groups * Time
0.00
0.01
0.00
1
5
5
0.00
0.00
0.00
—
—
1.0000 .4240
—
—
—
0.0670
—
*Comparison of the interactions of groups and time points.
JOE — Volume 42, Number 4, April 2016
Basic Research—Technology
electrode. This may also explain the absence of EMI between cellular
phones and EALs (17). Also, the findings of this study do not support
the claim in the user manuals of EALs that EMI from portable and mobile
radiofrequency communications equipment such as cellular phones
can cause interference with accurate reading of the apex locator.
Conclusion
The present study revealed that EWL determination by apex locators is not influenced by the presence of cellular phones. Cellular
phones can be used in the dental operatory without the fear of causing
EMI in EWL determination during root canal therapy. Further in vitro
and in vivo studies with different parameters may be beneficial to
confirm the results of the present study.
Acknowledgments
The authors deny any conflicts of interest related to this study.
References
1. Kim E, Lee SJ. Electronic apex locator. Dent Clin North Am 2004;48:35–54.
2. Kim E, Marmo M, Lee CY, et al. An in vivo comparison of working length determination by only root-ZX apex locator versus combining root-ZX apex locator with radiographs using a new impression technique. Oral Surg Oral Med Oral Pathol Oral
Radiol Endod 2008;105:e79–83.
3. Gordon MP, Chandler NP. Electronic apex locators. Int Endod J 2004;37:425–37.
4. Khursheed I, Bansal R, Bansal T, et al. A comparative evaluation of working length
with digital radiography and third generation apex locator (ProPex) in the presence
of various intra canal irrigants: an in vivo/ex vivo study. Dent Res J (Isfahan) 2014;
11:56–60.
5. Akisue E, Gavini G, de Figueiredo JA. Influence of pulp vitality on length determination by using the Elements Diagnostic Unit and Apex Locator. Oral Surg Oral Med
Oral Pathol Oral Radiol Endod 2007;104:e129–32.
6. Singh SV, Nikhil V, Singh AV, et al. An in vivo comparative evaluation to determine
the accuracy of working length between radiographic and electronic apex locators.
Indian J Dent Res 2012;23:359–62.
7. Ebrahim AK, Wadachi R, Suda H. In vitro evaluation of the accuracy of five different
electronic apex locators for determining the working length of endodontically retreated teeth. Aust Endod J 2007;33:7–12.
8. Hayes DL, Wang PJ, Reynolds DW, et al. Interference with cardiac pacemakers by
cellular telephones. N Engl J Med 1997;336:1473–9.
9. Patel MB, Thaker JP, Punnam S, et al. Pacemaker interference with an iPod. Heart
Rhythm 2007;4:781–4.
JOE — Volume 42, Number 4, April 2016
10. Miller CS, Leonelli FM, Latham E. Selective interference with pacemaker activity by
electrical dental devices. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;
85:33–6.
11. Madigan JD, Choudhri AF, Chen J, et al. Surgical management of the patient with an
implanted cardiac device: implications of electromagnetic interference. Ann Surg
1999;230:639–47.
12. Tandogan I, Temizhan A, Yetkin E, et al. The effects of mobile phones on pacemaker
function. Int J Cardiol 2005;103:51–8.
13. Trigano JA. Interferences and cardiac pacemakers-defibrillators: results of
in vivo experiments and radio frequencies. Arch Mal Coeur Vaiss 2003;
96(Spec No 3):42–5.
14. Baranchuk A, Kang J, Shaw C, et al. Electromagnetic interference of communication
devices on ECG machines. Clin Cardiol 2009;32:588–92.
15. Lawrentschuk N, Bolton DM. Mobile phone interference with medical equipment
and its clinical relevance: a systematic review. Med J Aust 2004;181:145–9.
16. Hietanen M, Sibakov V. Electromagnetic interference from GSM and TETRA phones
with life-support medical devices. Ann Ist Super Sanita 2007;43:204–7.
17. Hurstel J, Guivarc’h M, Pommel L, et al. Do cell phones affect establishing electronic
working length? J Endod 2015;41:943–6.
18. Klein AA, Djaiani GN. Mobile phones in the hospitals: past, present and future.
Anaesthesia 2003;58:353–7.
19. Barthelemy J, Gregor L, Krejci I, et al. Accuracy of electronic apex locatercontrolled handpieces. Oral Surg Oral Med Oral Pathol Oral Radiol Endod
2009;107:437–41.
20. Altunbas D, Kustarci A, Arslan D, et al. Comparison of various current electronic
apex locators to determine the working length using the clearing technique. Niger
J Clin Pract 2015;18:359–63.
21. Duran-Sindreu F, Gomes S, St€ober E, et al. In vivo evaluation of the iPex and Root ZX
electronic apex locators using various irrigants. Int Endod J 2013;46:769–74.
22. Chakravarthy Pishipati KV. An in vitro comparison of propex ii apex locator to standard radiographic method. Iran Endod J 2013;8:114–7.
23. Van Lieshout EJ, van der Veer SN, Hensbroek R, et al. Interference by newgeneration mobile phones on critical care medical equipment. Crit Care 2007;
11:R98.
24. Garofalo RR, Ede EN, Dorn SO, et al. Effect of electronic apex locators on cardiac
pacemaker function. J Endod 2002;28:831–3.
25. Wallin MK, Marve T, Hakansson PK. Modern wireless telecommunication technologies and their electromagnetic compatibility with life-supporting equipment.
Anesth Analg 2005;101:1393–400.
26. Theodore MR, Herald OH, Edward JS. Sturdevant’s Art and Science of Operative
Dentistry, 4th ed. St Louis, MO: Mosby Inc; 2002.
27. Sriman N, Prabhakar V, Bhuvaneswaran JS, et al. Interference of apex locator, pulp
tester and diathermy on pacemaker function. J Conserv Dent 2015;18:15–9.
28. Gomez G, Duran-Sindreu F, Jara Clemente F, et al. The effects of six electronic apex locators on pacemaker function: an in vitro study. Int Endod
J 2013;46:399–405.
Cellular Phones and Apex Locators
625