Design-Dependent Electrophysiological Effects of Electrolysis Electrodes Used for Endodontic Disinfection

At a Glance

Metadata	Details
Publication Date	2024-02-09
Journal	Applied Sciences
Authors	Reinhard Bauer, Johannes Ringel, Maximilian Koch, Matthias W. Laschke, Andreas Burkovski
Institutions	Friedrich-Alexander-Universität Erlangen-Nürnberg, Saarland University
Analysis	Full AI Review Included

Executive Summary

This study evaluated the design-dependent electrophysiological safety of Boron-Doped Diamond (BDD) electrodes intended for DC-driven electrochemical disinfection in endodontics, comparing them against a high-frequency AC electrotome reference.

Core Finding: The physical design and shielding of BDD electrodes are critical determinants of interference with vital functions (Electrocardiogram, ECG; Electrocorticogram, ECoG).
Optimal Design (Type i): The BDD electrode design where the anode (BDD-coated Nb wire) was positioned inside the steel cannula cathode showed no detectable electrophysiological effects (median score: 5/18), confirming its safety profile.
Unsafe Design (Type ii): The BDD electrode design where the anode was positioned outside the cathode caused significant disturbances (median score: 16.5/18), including generalized ECoG disorders and short-term epilepsy-like discharges.
Reference Comparison: The AC electrotome (HF surgery unit) induced the most pronounced effects (median score: 18/18), primarily due to strong electromagnetic interference (EMI) overwhelming the recording amplifiers.
Safety Implication: Since the AC electrotome is a legally approved medical device despite causing greater measurable disturbance (due to EMI), the BDD electrode (Type i) design, which caused no detectable effects, is considered a safe procedure for electrochemical disinfection.

Technical Specifications

Parameter	Value	Unit	Context
BDD Electrode Voltage	9	V	Direct Current (DC) applied for electrolysis.
BDD Anode Wire Diameter	50	µm	Niobium (Nb) wire core.
BDD Coating Thickness	1	µm	Boron-doped diamond layer on Nb wire.
BDD Cathode (Type i)	0.3 x 25	mm	Endodontic steel cannula (transcodent).
BDD Cathode (Type ii)	28	G	Endodontic steel needle (VMK Endoneedle).
Stimulation Duration	<20	s	Application time for all electrode types.
ECoG Filter Range	0.5-45	Hz	Bandpass filter applied to electrocorticographic signals.
Data Acquisition Rate	1000	Hz	Sampling frequency for ECoG and ECG signals.
Patient Auxiliary Current Limit (EN 60601)	0.5	mA	Regulatory safety limit for medical devices.
Internal Human Body Resistance (Reference)	~1	kΩ	Approximate total internal resistance to current flow.
Electrophysiological Score (Type i, Safe)	5 (5; 5)	N/A	Median (Q1; Q3) score: Harmless range (5-8).
Electrophysiological Score (Type iii, Electrotome)	18 (18; 18)	N/A	Median (Q1; Q3) score: Strong effects range (14-18).

Key Methodologies

Animal Preparation and Anesthesia: Female Sprague-Dawley rats were anesthetized (isoflurane induction, ketamine/xylazine i.p., carprofen s.c. analgesia) and fixed in a stereotactic frame.
Electrophysiological Instrumentation: ECG (Lead I) recorded via stainless steel needle electrodes. ECoG recorded via four screw electrodes inserted for bilateral unipolar leads from the primary somatosensory cortex (reference: nasal bone).
Electrode Insulation: ECoG electrodes were fixed and insulated using glass ionomer dental cement (Ketac Cem).
Stimulation Site Preparation: Maxillary and mandibular first molars were trepanned to expose the dental pulp until bleeding occurred.
Stimulator Application (Randomized): Four stimulator types were applied randomly into the opened cavities for <20 s while continuously rinsing with physiological saline solution:
- (i) BDD Electrode—Inside (Type i): Anode (BDD-coated Nb wire) inside the cannula cathode.
- (ii) BDD Electrode—Outside (Type ii): Anode outside the cannula cathode.
- (iii) Electrotome (Type iii): Monopolar electrode set at maximum intensity (High-frequency AC).
- (iv) Electric Shortcut Electrode (Type iv): Two Type iii coagulation electrodes electrically interconnected (DC short-circuit reference).
BDD Activity Verification: Electrolysis activity for BDD electrodes (i) and (ii) was confirmed by visual verification of intracavitary gas bubble production.
Data Acquisition and Analysis: ECoG and ECG signals were amplified, filtered (0.5-45 Hz ECoG), and stored at 1000 Hz. Instantaneous Heart Rate (HR) was derived from the reciprocal RR interval time series.
Semi-Quantitative Scoring: Electrophysiological events were classified using a significance score (1-18) based on the involvement (ECoG, ECG, HR), extent of disruption, and duration of the effect.

Commercial Applications

Endodontic Disinfection: Primary application for BDD electrodes, targeting bacterial load reduction in root canals and peri-implant infections using localized electrochemical radical production.
Medical Device Safety Engineering: Providing critical design data for developing DC-driven medical instruments, ensuring minimal electromagnetic interference (EMI) and compliance with patient auxiliary current limits (e.g., EN 60601-1).
Localized Tissue Ablation/Coagulation: Utilizing high-frequency AC electrotomes (Type iii reference) in oral and general surgery, where the high frequency prevents serious cardiac functional consequences (like fatal arrhythmias).
BDD Electrode Manufacturing and Design: Optimization of electrode geometry (e.g., Type i, shielded anode inside cathode) for clinical use to prevent current spread and ensure high safety margins in sensitive biological environments.
Minimally Invasive Medical Tools: Development of electrochemical tools for precise, localized treatment where bipolar configuration and shielding are mandatory to avoid systemic current flow through the heart or brain.

View Original Abstract

Electrochemical disinfection in dentistry using boron-doped diamond (BDD) electrodes bears the potential risk of disturbing vital functions. Applying different arrays of BDD electrodes and an electrotome as reference, it was the goal of this animal study to compare their effects on an electrocorticogram (ECoG) and electrocardiogram (ECG). Following the trepanation of teeth in rats, the electrodes and electrotome were applied in a randomized manner while recording ECoG and ECG. The recordings were classified according to an electrophysiological significance score based on involvement, extent of disruption and duration. The scores obtained were compared by means of ANOVA followed by Dunn’s multiple comparisons test (α = 0.05). Voltage type and electrode design had a significant influence on the detectable electrophysiological effects. The results seen with BDD electrodes ranged from no detectable electrophysiological effects to a pronounced effect. The application of the electrotome induced the most pronounced effects. Given that electrotomes are safe medical devices, despite evoking greater disturbance compared to BDD electrodes, regardless of their design, electrochemical disinfection may be considered a safe procedure.

Tech Support

Original Source

DOI: https://doi.org/10.3390/app14041445

References

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