Preclinical Testing of Boron-Doped Diamond Electrodes for Root Canal Disinfection—A Series of Preliminary Studies

At a Glance

Metadata	Details
Publication Date	2022-04-07
Journal	Microorganisms
Authors	Maximilian Koch, Victor Palarie, Lisa Koch, Andreas Burkovski, Manuel Zulla
Institutions	Friedrich-Alexander-Universität Erlangen-Nürnberg, Nicolae Testemițanu State University of Medicine and Pharmacy
Citations	6
Analysis	Full AI Review Included

Executive Summary

This study investigates the efficacy and defines the operational parameters for electrochemical root canal disinfection using Boron-Doped Diamond (BDD) electrodes, leveraging the in situ generation of Reactive Oxygen Species (ROS) from saline electrolysis.

Core Value Proposition: BDD electrodes enable predictable disinfection of complex root canal systems by generating potent disinfective agents directly within the canal, overcoming the limitations of conventional irrigation (e.g., poor access to dentin tubules).
Electrode Design: Prototype electrodes utilized BDD coatings deposited via Hot-Filament Chemical Vapor Deposition (HFCVD) onto Niobium (Nb) wires (50 µm and 200 µm diameter).
Performance Achievement (In Vitro): Electrochemical disinfection showed superior efficacy compared to saline rinsing and comparable or better results than chlorhexidine (CHX). Application for 1.0 min reduced Enterococcus faecalis survival to less than 5%.
Multispecies Biofilm Efficacy: Complete elimination of multispecies biofilm was achieved in several in vitro replicates using optimized BDD parameters (e.g., 6.5 V/10.0 mA).
Clinical Parameters Defined: Successful disinfection in a canine model was achieved using operational ranges of 5.5 to 7.0 V and 9 to 38 mA, applied for 2.5 to 6.0 min with 5 to 8 mL of 0.9% NaCl saline.
Anatomical Requirement: The system requires a minimum apical diameter of 300 µm (ISO size #30) for electrode insertion, allowing ROS delivery close to the critical apical region early in the treatment process.

Technical Specifications

Parameter	Value	Unit	Context
Anode Material	Boron-Doped Diamond (BDD) on Niobium (Nb)	-	Active Electrode Surface
Cathode Material	Wired Cannula	-	Saline Delivery/Counter Electrode
Nb Wire Diameter (Prototype 2)	50	µm	Substrate for BDD coating
Nb Wire Thickness (Prototype 1)	200	µm	Substrate for BDD coating
HFCVD Filament Material	Tungsten	-	Deposition Source
HFCVD Filament Dimensions	220, Ø 100	mm, µm	Filament Geometry
Carburization Time/Current	18, 65	h, A/mount	Pre-treatment for stable deposition
Operating Voltage (Clinical Range)	5.5 to 7.0	V	Electrochemical Disinfection
Operating Current (Clinical Range)	9 to 38	mA	Electrochemical Disinfection
Application Time (Clinical Range)	2.5 to 6.0	min	Disinfection Protocol
Irrigant Solution	Saline (0.9% NaCl)	-	Electrolyte Source for ROS Generation
Required Apical Diameter	300 (ISO #30)	µm	Minimum canal size for electrode insertion
E. faecalis Survival (1.0 min BDD)	less than 5	%	In vitro Monospecies Biofilm Reduction

Key Methodologies

The BDD electrodes were fabricated and tested using the following sequence of steps and parameters:

Niobium Substrate Preparation: Niobium wires (50 µm or 200 µm) were pre-treated by sandblasting at 5 bar using silicon carbide (SiC) particles (17-74 µm). Wires were subsequently cleaned in an ultrasonic bath (2 min, 45 kHz).
Diamond Seeding: Nanodiamond dispersions were applied at a ratio of 1:1000 or 1:10,000 in ethanol to seed the Nb surface.
HFCVD Carburization: Tungsten filaments (Ø 100 µm) were pre-heated for carburization (18 h, 65 A/mount) to ensure stable conditions prior to diamond deposition.
BDD Deposition: Diamond coating with boron doping was performed using Hot-Filament Chemical Vapor Deposition (HFCVD) in a gas atmosphere containing methane, hydrogen, and trimethyl borate.
In Vitro Biofilm Model: Extracted human teeth were instrumented (up to ISO #50) and inoculated with Enterococcus faecalis (monospecies) or a multispecies bacterial suspension derived from clinical samples. Biofilms were incubated for 24 hours (monospecies) or 5-7 days (multispecies) at 37 °C.
Electrochemical Treatment (In Vitro): Prototype 1 electrodes were applied using 2 mL/min saline irrigation, 20 mA current, and 6-7 V, with application times ranging from 0.5 to 7.5 min.
In Vivo Testing (Canine Model): Prototype 2 electrodes were applied following conventional chemo-mechanical preparation. Parameters used were 5.5-7.0 V, 9-38 mA, applied for 2.5-6.0 min, using 5-8 mL of saline irrigation.

Commercial Applications

The technology developed in this research, based on high-performance Boron-Doped Diamond electrodes and electrochemical oxidation, is relevant to several high-value commercial sectors:

Endodontics and Dentistry: Direct application for root canal disinfection, particularly in complex or narrow canal anatomies where conventional chemical irrigation is ineffective.
Medical Device Sterilization: Use of BDD-generated ROS for localized, high-efficiency sterilization of surgical tools or implants, especially those with complex microstructures.
Water and Wastewater Treatment: BDD electrodes are widely used for Advanced Oxidation Processes (AOPs) to degrade persistent organic pollutants (POPs) and disinfect water supplies due to their high overpotential for oxygen evolution.
Peri-implantitis Treatment: Previous studies by the authors have demonstrated the efficacy of BDD electrodes for biofilm removal and disinfection on dental implant surfaces.
Electrochemical Sensing: BDD’s wide potential window and chemical inertness make it an ideal material for high-sensitivity electrochemical sensors and detectors.

View Original Abstract

While numerous approaches have meanwhile been described, sufficient disinfection of root canals is still challenging, mostly due to limited access and the porous structure of dentin. Instead of using different rinsing solutions and activated irrigation, the electrolysis of saline using boron-doped diamond (BDD) electrodes thereby producing reactive oxygen species may be an alternative approach. In a first step, experiments using extracted human teeth incubated with multispecies bacterial biofilm were conducted. The charge quantities required for electrochemical disinfection of root canals were determined, which were subsequently applied in an animal trial using an intraoral canine model. It could be shown that also under realistic clinical conditions, predictable disinfection of root canals could be achieved using BDD electrodes. The parameters required are in the range of 5.5 to 7.0 V and 9 to 38 mA, applied for 2.5 to 6.0 min with approximately 5 to 8 mL of saline. The direct generation of disinfective agents inside the root canal seems to be advantageous especially in situations with compromised access and limited canal sizes. The biologic effect with respect to the host reaction on BDD-mediated disinfection is yet to be examined.

Tech Support

Original Source

DOI: https://doi.org/10.3390/microorganisms10040782

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