Can active signals of cellphone interfere with electronic working length determination of a root canal in a dental clinic? An in vivo study.

OBJECTIVE: To evaluate the interference of active cellphones during electronic working length (EWL) determination of a root canal.
MATERIALS AND METHODS: Thirty patients requiring root canal treatment in the anterior teeth or premolars having single canal and mature apices were selected for this study. Working length determination was done using no. 15 K-file. Electronic apex locators ProPex Pixi and Root ZX mini were used for working length determination. Cellphones iPhone 6s and Xolo Q3000 were evaluated for their interference. The experiment was conducted in a closed room (9 feet × 9 feet). Working length was measured with no cellphone in the room, iPhone 6s in a calling mode, Xolo Q3000 in a calling mode, and Xolo Q3000 and iPhone 6s simultaneously in a calling mode. Stability of the readings was also determined for every condition. STATISTICAL ANALYSIS: The data were statistically analyzed using one-way ANOVA and paired t-test at 0.05 level of significance.
RESULTS: Results were not statistically significant.
CONCLUSION: Within the limitations of the present study, cellphones do not interfere with the EWL determination.

INTRODUCTION

The technical support documents of electronic apex locators (EALs) state that electromagnetic interference (EMI) could cause EALs to operate in an abnormal, random, and possibly dangerous manner.[1] In Critical Care Units (CCUs) of hospitals, some precautions are taken to prevent EMI of cellphones on medical devices.[23] A dental operatory has no such limitations for the use of cellphones. Dentists, assistants, and patients often use cellphones during the treatment. There is a limited evidence that can help a dentist to come to a decision whether cellphones can be used in proximity to EALs and whether these devices can have any effect on electronic working length (EWL) determination. Hence this study was performed with an aim to investigate the EMI of cellphones on electronic apex locators.

MATERIALS AND METHODS

Thirty patients requiring root canal treatment in the anterior teeth or premolars having single canal and mature apices were selected for the purpose of this study. The entire procedure was explained to the patient. Written informed consent was obtained from the patients. Adequate field disinfection was performed. Local anesthesia was given in case of vital teeth. Occlusal or incisal grinding was done to obtain a stable reference point. After adequate access opening and rubber dam isolation, pulp was extirpated using no. 10 K-file and using 2.5% sodium hypochlorite solution. Working length determination was done with no. 15 K-file using Endobloc (Dentsply Maillefer, United States).

Two EALs were used in the study:

ProPex Pixi (Dentsply Maillefer, Ballaigues, Switzerland)

Root ZX mini (J. Morita Mfg. Corp., Kyoto, Japan).

Two cellphones that were used to evaluate EMI:

iPhone 6s (Apple, manufactured in California)

Q3000 (Xolo, manufactured in China).

Experimental setting

The whole experiment was carried out in a closed room (9 feet × 9 feet). The distance of 2 feet was maintained between cellphone and apex locator.

Working length was measured using no. 15 K-file and Endobloc under the following conditions for each EAL:

No cellphone in the room

iPhone 6s in a calling mode at a distance of 2 feet from EAL and file holder of EAL

Xolo Q3000 in a calling mode at a distance of 2 feet from EAL and file holder of EAL

Xolo Q3000 and iPhone 6s simultaneously in a calling mode at a distance of 2 feet from EAL.

For each condition, three readings were taken and an average of the three readings was taken as a final reading. Figure 1 shows the experimental condition of Electronic working length determination by the dental operator with Root ZX mini without cellphones in the room. And Figure 2 shows experimental condition of Electronic working length determination by the dental operator with ProPex Pixi along with Xolo Q3000 in a calling mode in a room [Table 1].

Figure 1

Electronic working length determination in a room with Root ZX mini without cellphones in the room

Figure 2

Electronic working length determination in a room with ProPex Pixi along with Xolo Q3000 in a calling mode by the dental operator

Table 1

Working length measurements of ten (out of thirty) teeth with two electronic apex locators under four different conditions

Stability of the readings was also determined for every condition.[4]

To determine the stability of EWL readings, the following scores were used:

Score 1: Immediate and good signal strength with an audible and visible signal of 5 s and no problems determining the EWL

Score 2: Slight instability with minor difficulties to determine the EWL (an audible and visible signal of 5 s was obtained but only after two attempts)

Score 3: Major difficulties or impossible to determine the working length after three attempts.

Statistical analysis

First paired t-test was performed to compare the readings of two EALs without a cellphone. One-way repeated analysis of variance was performed for each apex locator to see if the cellphone model influenced the readings of EAL. Then, paired t-test was performed to assess the interference of simultaneous use of two cellphones on EAL. The confidence level was set at 95% level [Table 2].

Table 2

Results of one Way ANOVA For Root ZX mini and Propex Pixi Apex locators

RESULTS

At 95% confidence interval, the results of one-way ANOVA as well as paired t-tests were nonsignificant. This means that there was no statistically significant difference in the readings of working length of two EALs (with no cellphones in the room) with a single cellphone in a calling mode or simultaneously two cellphones in a calling mode.

Regarding the stability of readings, it was always possible to determine the working length regardless of experimental conditions (none scored 3).

Crackling background noises were detected in the cellphones by a dentist and dental surgery assistant during simultaneous use of the cellphones signifying the EMI of two cellphones on each other.

DISCUSSION

Root canal therapy is an integral part of dental practice. Moreover, the success of root canal treatment depends on various factors among which correct working length estimation plays a crucial role. EAL which is a useful adjunct in endodontics to determine the working length helps in reducing treatment time and radiation dose to the patient.[5] It has been reported that the reliability of EAL is better than digital radiography or cone beam computed tomography.[6] Several in vitro and in vivo studies have documented that the accuracy of EALs depends on their correct usage, presence or absence of irrigants, presence of vital or necrotic pulp, presence of inflammatory exudate, and obturating material in the root canal.[78910] Here, another factor termed as EMI which can affect EWL determination is checked for its interference. EMI or radiofrequency interference is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electromagnetic conduction, or electrostatic coupling. It is reported that electromagnetic radiation emitted from devices such as cellphones, iPods, and dental devices such as electric pulp testers, electrosurgery units, and ultrasonic scalers can interfere with the function of cardiac pacemakers, implanted in the patients.[111213] Electrical energy from these dental devices can travel down the lead wires and can induce ventricular or atrial fibrillation and reprogram the cardiac pacemaker.[14] Studies have reported that cellphones can interfere with the function of pacemaker and this depends on the distance between the pacemaker and electronic device, power output of the electronic device, type of pacemaker, age of pacemaker, and the model of cellphone.[151617] In CCUs of hospitals, there are some precautions taken to prevent interferences such as allowing usage of cellphones in nonpatient areas, restrictions in clinical areas, cellphone safe wards, and use of distance >1 m from all medical equipment.[23] Dentists, dental surgery assistants, and patients often use cellphones in proximity to dental devices. The technical support documents of EALs state that cellphone, transceivers, remote controls, and all other devices which transmit electromagnetic waves should be turned off while using EAL.[1] There is a limited evidence that can help a dentist to come to a decision whether cellphones can be used in proximity to EALs and whether these devices can have any effect on EWL determination. Two in vitro studies have been performed to evaluate EMI of cellphones on EWL determination.

This study concluded that the use of cellphone at a distance of 2 feet from the EAL does not influence the readings of EALs. Furthermore, simultaneous use of two cellphones does not influence EWL determinations. Thus, cellphones can be used in a dental operatory during root canal therapy without the risk of EMI between cellphone and EAL. These results are in accordance with two in vitro studies to evaluate interference of cellphones on EWL determination by Hurstel et al.[4] and Sidhu et al.[18]

Single canal teeth were selected as samples to prevent any interference of anatomical variations of multiple canals in working length estimation. Earlier studies have shown that there was no significant difference regarding EWL measurements between multifrequency ProPex II and dual frequency Root ZX. This was confirmed by performing paired t-test in our study. Hence, Root ZX mini, a third-generation EAL a dual frequency device of 0.4 and 8 kHz, and ProPex Pixi which records signals at 2 ACs 0.5 and 8 kHz (calculates mean square root of impedance in two frequencies) represent the generations of EALs which are most commonly used were selected for the study. iPhone 6s, a recent smartphone (works at a frequency of 2100 MHz), which has a more frequency of bands than most other cellphones, and Xolo Q3000 which represents the group of cellphones working at a frequency of 900–1800 MHz were used to evaluate interference. As the distance between two electronic devices can influence EMI,[192021] 2 feet distance was kept in this study to simulate the exact clinical scenario of a dentist/dental hygienist talking on a cellphone. As the wave emission is intense during calling mode of a cellphone,[4] calling mode was used in the study to maximize the chances of detecting EMI. The interference between cardiac pacemakers and cellphones is not time dependent. A stimulus either does or does not interfere with the pacemaker.[21] Hence, a stimulus of 25 s deemed satisfactory for the purpose of the study. Within the limitations of the present study, active signals of single cellphone or two cellphones simultaneously neither affect the accuracy of readings nor the stability of readings, which is in agreement with the previously performed in vitro studies. In 0.5% cases, crackling sounds were heard in cellphones by the dentist and dental surgery assistant during simultaneous calling mode of two cellphones signifying EMI between two cellphones.

CONCLUSION

Thus, it can be concluded that cellphones can be used safely in a dental operatory without the fear of interference of EMI on EWL. Further, in vitro and in vivo studies with different parameters may be beneficial to confirm the results of the present study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.