Journal of Conservative Dentistry

: 2015  |  Volume : 18  |  Issue : 1  |  Page : 15--19

Interference of apex locator, pulp tester and diathermy on pacemaker function

Narayanan Sriman1, V Prabhakar1, JS Bhuvaneswaran2, N Subha1,  
1 Department of Conservative Dentistry and Endodontics, Sri Ramakrishna Dental College and Hospital, Coimbatore, India
2 Department of Cardiology, P.S. Govindasamy Naidu Institute of Medical Sciences and Research, Coimbatore, Tamil Nadu, India

Correspondence Address:
Dr. Narayanan Sriman
Department of Conservative Dentistry and Endodontics, Sri Ramakrishna Dental College and Hospital, S.N.R College Road, Coimbatore - 641 006, Tamil Nadu


Aim: The purpose of this study was to evaluate the effects of three electronic apex locators (EAL), electric pulp tester (EPT) and diathermy on pacemaker function in vitro. Materials and Methods: Three EALs: Root ZX (J. Morita Co., Tustin, CA, U.S.A.), Propex (Dentsply), Mini Apex locator (SybronEndo, Anaheim, CA, USA), EPT (Parkell pulp vitality tester Farmingdale, NY, USA) and Diathermy (Neomed 250 B) were tested for any interference with one pacemaker (A medtronic kappa KVDD901-serial number: PLE734632S). Directly connecting the pacemaker lead with the EAL/EPT/diathermy operating on a flat bench top, the telemetry wand was held directly over the pacemaker to monitor the pacing pattern for a period of 30 s. Pacemaker activity was continuously recorded on the telemetric programmer and electro gram (EGM) readings examined for pacer inhibition, noise reversion or inappropriate pacemaker pulses. Results: All the three apex locators showed no pacing interference or background noise during its function or at rest. The EGM readings of EPT showed varying levels of background noise in between pacing however, this did not affect the normal pacing pattern and the pacing interval remained constant. EGM readings of diathermy showed an increase in the pacing interval (irregular pacing pattern) followed by complete inhibition of the pacing system. Conclusion: The tested EALs do not interfere with cardiac pacemaker function. The tested EPT showed varying levels of background noise but does not interfere with cardiac pacemaker function. Use of Diathermy interfered with the normal pacing, leading to complete inhibition of the pacing system.

How to cite this article:
Sriman N, Prabhakar V, Bhuvaneswaran J S, Subha N. Interference of apex locator, pulp tester and diathermy on pacemaker function.J Conserv Dent 2015;18:15-19

How to cite this URL:
Sriman N, Prabhakar V, Bhuvaneswaran J S, Subha N. Interference of apex locator, pulp tester and diathermy on pacemaker function. J Conserv Dent [serial online] 2015 [cited 2023 Feb 5 ];18:15-19
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There are about 3 million people worldwide with cardiac pacemakers and each year about 600000 pacemakers are implanted. In India an average of 20,000 patients get pacemaker implants every year. [1] The American Association of Endodontics estimates that nearly 16 million root canal procedures are performed every year. [2] Thus, the average dental practice that provides care to adults, including elderly people, is expected to have patients who have a permanently implanted cardiac device. Traditionally electronic apex locators (EALs) and electronic pulp testers (EPTs) are not recommended for use in patients with implanted cardiac pacemakers (ICPs) [3],[4],[5] due to possibility of electrical interference in patients with ICP.

Over the years studies have been done to determine the potential of various devices that can interfere with implanted cardiac pacemakers, such as cellular phones [6] , iPods [7] to instruments used in the dental office such as EALs, EPT, amalgamator, composite curing light, ultrasonic scalers, dental hand piece, electric toothbrush, electro surgery units, etc. Some devices such as ultrasonic scalers and cleaners, electrosurgical instruments, dental induction-casting machines, electric pulp testers, and microwave ovens have earlier been proved to cause interference with ICP function. [8]

There have been dramatic improvements in pacemaker technology over the last few decades. Pacemakers manufactured before 1975 used discrete electronic components encapsulated in a clear epoxy case, this casing was not effective in shielding the cardiac pacemaker from electromagnetic interference. [9] The principle by which the primitive apex locator functioned used electrical resistance (direct current) to measure the canal length. [10] An artificial electrical stimulus may be interpreted as noise and temporarily cause reversion of an ICP to an asynchronous pacing mode, or the signal may inappropriately reprogram the cardiac device. [11] Conducted electrical energy, such as that produced from electrocautery, may travel down the lead wires to the heart and induce ventricular or atrial fibrillation [11] and hence EALs and EPTs were not recommended in patients with ICPs.

Currently, manufacturers of EPTs and EALs warn against using these devices in patients with ICPs. [3],[4] Such warnings are based on speculation of potential risk of electromagnetic interference (EMI) rather than on scientific evidence. The available literature evaluating interference between EAL/EPTs and ICPs is limited, and conclusions are difficult to draw. The purpose of this study was to assess the effects of electronic apex locators and electric pulp tester on pacemaker function in vitro.

 Materials and Methods

This study evaluated the potential for interference of electronic pulp tester, electronic apex locators and diathermy with pacemaker function. Dental devices were tested for pacemaker interference, including the Root ZX (J. Morita Co., Tustin, CA, U.S.A.), Propex (Dentsply), Mini Apex locator (SybronEndo, Anaheim, CA, USA), Parkell pulp vitality tester (Farmingdale, NY, USA), Diathermy (Neomed 250 B). A medtronic kappa KVDD901 (serial number: PLE734632S) pacemaker was set to 50 pulses/min and evaluated at maximum sensitivity (bipolar: VVI mode, 0.1 mV) on a flat bench top. Pace monitoring was carried out with a Medtronic carelink/vitataron programmer.

Stimulation protocol

The study design consisted of directly connecting the pacemaker lead, EAL/EPT with the pacemaker programmer [Figure 1]. With the telemetry wand in place, the surface and intracardiac electrocardiogram were continuously printed during testing, which consisted of ten phases each lasting 30 s. Phase 1 (rest 1) was recorded at rest, to serve as a baseline of normal device function. Phase 2, was recorded during stimulation with the Root ZX, and followed by Phase 3 without stimulation (rest 2). Phase 4 was during stimulation with the Propex, followed by Phase 5 without stimulation (rest 3). Phase 6 was during stimulation with the Sybron endo mini apex locator, followed by Phase 7 without stimulation (rest 4). Phase 8 was during stimulation with Parkel electric pulp tester at level 4, Phase 9 was during stimulation with Parkel electric pulp tester at level 10 followed by, Phase 10 without stimulation (rest 5). Phase 11 during stimulation with Diathermy (Neomed 250 B), followed by Phase 12 without stimulation (rest 6). Pacemaker activity was continuously recorded by Telemetric programmer and printouts taken during each phase were examined for Pacer inhibition, noise reversion or inappropriate pacemaker pulses [Figure 2].{Figure 1}{Figure 2}


[Table 1] shows oscilloscope readings obtained from telemetric programmer when various dental devices were connected to pacemaker in VVI mode. The pacemaker exhibited a normal pacing pattern during 30 seconds before each trial (phase I) which was considered as baseline reading. The telemetric recordings of the pacemakers with all of the dental devices were recorded and evaluated. Readings of the telemetric programmer are shown in [Figure 3].{Figure 3}{Table 1}

Heuristic evaluation

Heuristic evaluation, a usability inspection method commonly used for software usability evaluation, modified and extended for medical devices was used based on the severity rating scale given below. The observations of the severity rating scale of various evaluator's are presented in [Table 2].{Table 2}

Severity rating scale

The heuristics are used to check the interface of the device design. If a heuristic is violated, it is given a severity rating based on the following scales [12] :

0. Not a usability problem at all;

1. Cosmetic problem only. Need not be fixed unless extra time is available;

2. Minor usability problem. Fixing this should be given low priority;

3. Major usability problem. Important to fix. Should be given high priority;

4. Usability catastrophe. Imperative to fix this before product can be released.


Safe dental treatment requires elimination of electrical interferences that could affect the cardiac health of patient with implanted cardiac pacemakers. However, guidelines for use of electrical dental equipment around pacemakers have not been updated for more than 20 years. [13] The aim of this study was to assess the effects of electronic apex locators and electric pulp tester on pacemaker function in vitro.

Medtronic pacemakers have been shown to be more reliable than other models. [13],[14] The setting of the medtronic pacemaker in the VVI pacing mode provided the greatest sensitivity setting of any pacemaker products currently available. Cardiac pacemaker interference is not a time-dependent phenomenon. A given stimulus either does or does not inhibit normal pacing. Therefore, a testing interval of 25-30 seconds was deemed satisfactory for the purposes of this study.

The results obtained (Phases 2, 3, 4, 5, 6, 7) by evaluating three apex locators (Root Zx, Propex, Sybron Endo Mini) showed that they do not cause any interference with the pacemaker function. These findings support the case report published by Beach et al.,[15] showing the use of an electronic apex locator in a pacemaker patient without clinical incident. In 1991, ZappaU [16] studied EPT use in 26 patients with ICPs. His report found no interference from EPT use on pacemaker rate or electrocardiogram morphology. EALs were not included in their study. Currently no other in vitro/in vivo data is available on interactions of EALs with ICPs.

Findings with electric pulp tester (Phases 8, 9, 10) showed varying degree of background noise, however normal pacing was not affected, and no change in pacing interval was noted. Pacing interval remained constant and there was no interference produced and it can be suggested that this device is probably safe to use in the dental office during the treatment of pacemaker patients. It may however, be wise to use battery-operated EPT in preference to mains devices.

The fact that electric pulp tester does not cause interference is in contrast to the findings of Woolley et al.,[17] who found that electric pulp testers interfered with implanted pacemakers in dogs. This study is commonly cited as a rationale for not using EPTs in patients with ICPs. In 1974 ICPs were relatively immature in the evolution of pacemaker sophistication. Further, the type of interference that was reported would not be problematic to patients, since functional pacing continued.

Interference with pacemaker activity during operation of the electrosurgical unit occurred in this study (Phase 11). It was noted as an increase in pacing interval initially, followed by complete inhibition of the pacing system. Diathermy, although not absolutely contraindicated, generates high-intensity conducted interference which has been shown to be capable of interfering with pacing systems; it is unlikely that dental treatment using the diathermy justified the risks involved. The probability of the diathermy causing interference has been shown by Simon et al.,[18] and Sowton et al. [9] If sufficient energy is coupled into the pacing system from diathermy apparatus the myocardium may be burnt or ventricular fibrillation initiated. The pacing system itself may also be damaged. Radiated interference from a diathermy has been shown to be insignificant at a distance of 30 cm from the cutting point. [19] Interference by electrosurgical units has been consistently reported [9],[11],[20] suggesting that these units produce deleterious effects on pacemaker function.

Electronic apex locator, electric pulp tester, diathermy was tested despite manufacturer's warning to the contrary. There are no strict guidelines covering the use of electrical devices on pacemaker patients. Most electrical equipment can be used safely. Following factors in favor of its use are EALs is confined to the head region, roughly 10-12 inches from the heart, and does not cross the chest. The titanium or stainless steel case of the pacemaker will serve as an EMI shield, reducing the effects of EMI on the device. [21] These factors may depend on the specific pacemaker placed and if the patient is totally pacemaker dependent. The dentist should also make sure that all electronic equipment used during the procedure is properly grounded and not placed in close proximity to the pacemaker leads.

There is a need to corroborate the findings of the in vitro study by in vivo testing before EALs and EPTs can be recommended for clinical use in patients with cardiac pacemakers.


From the results of the present in-vitro study, it may be concluded,

The tested EPL Root ZX (J Morita Corp., Japan), Propex (Dentsply Maillefer, Ballaigues, Switzerland), Sybron Endo mini (SybronEndo, Anaheim, CA, USA) do not interfere with cardiac pacemaker function.The tested EPT, Parkell pulp vitality tester (Farmingdale, NY, USA) does not interfere with cardiac pacemaker function.The use of Diathermy (Neomed 250 B) interfered with the normal pacing, leading to complete inhibition of the pacing system.


1Mond HG, Proclemer A. The 11th World survey of cardiac pacing and implantable cardioverter-defibrillators: Calendar year 2009: A World Society of Arrhythmias project. Pacing Clin Electrophysiol 2011;34:1013-27.
2Am Association of Endodontics 2004. Webpage: [Aug 2011].
3Analytic Endo Analyzer Model 8005; SybronEndo, Orange, CA, U.S.A; Operation manual.
4J Morita Corp; Root ZX. Operation manual; 2001.
5Glendora; CA: Sybron Endo; 2006. Mini apexlocator [sales manual] p. 1-3.
6Hayes DL, Wang PJ, Reynolds DW, Estes M 3rd, Griffith JL, Steffens RA, et al. Interference with cardiac pacemakers by cellular telephones. N Engl J Med 1997;336:1473-9.
7Patel MB, Thaker JP, Punnam S, Jongnarangsin K. Pacemaker interference with an iPod. Heart Rhythm 2007;4:781-4.
8Miller 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.
9Sowton E, Gray K, Preston T. Electrical interference in noncompetitive pacemakers. Br Heart J 1970;32:626-32.
10Sunada I. New method for measuring the length of the root canal. J Dent Res 1962;41:375-87.
11Madigan JD, Choudhri AF, Chen J, Spotnitz HM, Oz MC, Edwards N. Surgical management of the patient with an implanted cardiac device: Implications of electromagnetic interference. Ann Surg 1999;230:639-47.
12Zhang J, Johnson TR, Patel VL, Paige DL, Kubose T. Using usability heuristics to evaluate patient safety of medical devices. J Biomed Inform 2003;36:23-30.
13Kaye GC, Butrous GS, Allen A, Meldrum SJ, Male JC, Carom AJ. The effect of 50 Hz external electrical interference on implanted cardiac pacemakers. Pacing Clin Electrophysiol 1988;11:999-1008.
14Dodinot B, Godenir JP, Costa AB. Electronic article surveil- lance: A possible danger for pacemaker patients. Pacing Clin Electrophysiol 1993;16:46-53.
15Beach CW, Bramwell JD, Hutter JW. Use of an electronic apex locator on a cardiac pacemaker patient. J Endod 1996;22:182-4.
16Zappa U, Studer M, Merkle A, Graf H, Simona C. Effect of electrically powered dental devices on cardiac parameter function in humans. Parodontol 1991;2:299-308.
17Woolley LH, Woodworth J, Dobbs JL. A preliminary evaluation of the effects of electrical pulp testers on dogs with artificial pacemakers. J Am Dent Assoc 1974;89:1099-101.
18Simon AB, Linde B, Bonnette GH, Schlentz RJ. The individual with a pacemaker in the dental environment. J Am Dent Assoc 1975;91:1224-9.
19Luker J. The pacemaker patient in the dental surgery. J Dent 1982;10:326-32.
20Wood MA, Ellenbogen KA. Cardiac pacemakers from the patient's perspective. J Am Heart Assoc 2002;105:2136-8.
21Rahn R, Zegelman M, Brief I, Kreuzer J, Frenkel G. Susceptibility of frequency adapted cardiac pacemakers to dental treatment. Dtsch Zahnarztl Z 1989;44:244-7.