## 1 Introduction  
Electrochemical disinfection using boron-doped diamond electrodes has been shown to effectively reduce bacterial loads in both endodontic and peri-implant infections, while local host tissue reactions seem not to differ from conventional treatment protocols [1, 2]. In contrast to being locally effective while not causing harm, the potential risks of electric currents interfering with body functions have not been investigated yet. Depotphoresis for endodontic treatment [3], transporting OH-ions and Cu compounds through apical canals of teeth [4, 5] and thereby removing and inactivating organic material [6], seems to be well comparable from an electrical perspective, but reports on the general risks are not available. The effects of electrical currents on the human body are governed by the exposure time, the intensity and frequency of the current and the path of the current in the body [7]. Ranked according to severity, these effects may range from no effect to pain sensation, muscle clamping, reversible respiratory problems and arrhythmia, to ventricular fibrillation, respiratory arrest and cardiac arrest (Figure 1). Thermal effects such as burns only occur at high current strengths, which normally already have dangerous effects on the human body. Consequently, the norm for the electrical safety of medical devices (VDE Norm EN 60601-1,VDE 0100-751) dictates much lower current limits compared to the consumer or industrial safety norm VDE 0100-710, 720 and 410. The patient auxiliary current, which is necessary for the function of a device, is specified in EN 60601 at a maximum of 0.5 mA [8]. An alternating current (AC) mainly acts by nerve irritation with frequencies > 200 Hz no longer causing muscle cramps due to their longer reaction time; the current is mainly determined by the capacity of the body (approx. 150 pF; EN 60601-1, VDE 0100-751 [9]). In addition, increasing frequencies lead to the skin effect, i.e., the current is concentrated on the surface of a conductor but does not use the entire conductor. Unipolar electrotomes (High-frequency (HF) surgery) apply a high-frequency current, which is conducted away from the patient via a counter-electrode. These high currents act by heating or vaporizing  
Figure 1: Nomograms showing the influence of a current on the human body. The nomograms are divided into 4 sections, AC-1 to AC-4 and DC-1 to DC-4, describing body reactions as a result of the current and exposure time. Section 1: usually indiscernible; Section 2: clearly perceptible up to muscle cramping; Section 3: muscle cramping, respiratory problems; and Section 4: arrhythmia, ventricular fibrillation, respiratory arrest, cardiac arrest. (**a**) Effects of an alternating current (AC). (**b**) Effects of a direct current (DC). tissue and fluids, but would cause ventricular fibrillation when passing through the heart (VDE0100-410, Section 415), which can be avoided by the adequate positioning of the counter-electrode. Furthermore, AC devices may interfere with monitoring instruments as a consequence of the electromagnetic field evoked. A direct current (DC), on the contrary, impairs nerve conduction, particularly in the case of small currents [7; 10]. In addition, a DC always uses the entire body as a conductor and the current divides itself according to the resistance present in a specific region, with nerves and blood vessels having a low resistance, while bone, skin and fat tissue have high resistance [11]. The total internal resistance of the human body is approximately 1 kOhm [7]. As a rule, when the heart is in the path of the current, the current is considered more dangerous (VDE0100-410). In order to maximize patient safety, a bipolar configuration avoiding a direct current path via the patient is preferred. In such a situation, only a small equalizing current can flow via the patient until the body capacity has adapted to the potential of the electrode.