Electrochemical Disinfection of Root Canals Bears No Risk of Damaging Periapical Tissues in a Dog Model

At a Glance

Metadata	Details
Publication Date	2023-07-15
Journal	Applied Sciences
Authors	Maximilian Koch, Elena Demmer, Victor Palarie, Andreas Burkovski, Matthias Karl
Institutions	Friedrich-Alexander-Universität Erlangen-Nürnberg, Nicolae Testemițanu State University of Medicine and Pharmacy
Analysis	Full AI Review Included

Executive Summary

This study evaluates the risk of host tissue damage associated with Boron-Doped Diamond (BDD) electrochemical disinfection (ECD) as a novel alternative for root canal treatment, comparing it against established chemical protocols.

Core Value Proposition: BDD electrodes enable the generation of potent, transient hydroxyl (OH) radicals for root canal disinfection, offering superior efficacy (per previous studies) without increasing the risk of periapical host tissue damage.
In Vitro Safety: Direct BDD application resulted in significantly higher HeLa cell viability compared to standard chemical irrigants (H₂O₂, NaOCl, CHX) at clinical concentrations, demonstrating a transient cytotoxic effect.
In Vivo Model: A dog model was used to compare conventional chemo-mechanical treatment (CHX rinsing) versus conventional treatment followed by BDD ECD.
Host Tissue Damage Assessment: Periapical radiolucency was measured radiographically and histologically six weeks post-treatment to assess host response.
Key Safety Finding: No statistically significant difference was found in the size of periapical radiolucency between teeth treated conventionally and sealed versus teeth treated with BDD electrodes and sealed (Vertical p = 0.940; Horizontal p = 0.862).
Conclusion: The application of BDD electrodes for root canal disinfection does not bear a greater risk of host tissue damage than conventional chemical treatment protocols, supporting its potential for future clinical adoption.

Technical Specifications

Parameter	Value	Unit	Context
BDD Electrode Active Surface (Direct)	3 x 4	mm	In vitro cell culture (HeLa cells)
BDD Electrode Active Surface (Indirect)	6 x 8	mm	In vitro PBS pretreatment
Potentiostatic Range (In Vitro)	6 to 9	V	Direct application, resulting in 2 to 35 mA
Amperostatic Current (In Vitro)	50	mA	Direct and indirect application
In Vitro Treatment Time (Amperostatic)	5	min	Comparison against chemical irrigants
In Vivo BDD Application Time Range	145 to 360	s	Root canal disinfection (Dog Model)
In Vivo BDD Charge Density Range	62.3 to 277	As cm^-2	Total charge applied per active surface area
Conventional Irrigant Concentration (NaOCl)	3% and 0.3%	w/v	In vitro cell viability comparison
Conventional Irrigant Concentration (H₂O₂)	3% and 0.3%	w/v	In vitro cell viability comparison
Conventional Irrigant Concentration (CHX)	0.2% and 0.02%	w/v	In vitro cell viability comparison
Histologic Radiolucency (BDD vs. Conventional Sealed)	p = 0.940 (Vertical), p = 0.862 (Horizontal)	N/A	No significant difference in host tissue damage
Statistical Significance Level (alpha)	0.05	N/A	Kruskal-Wallis and Nemenyi’s All-Pairs tests
Observation Period (In Vivo)	6	weeks	Post-second intervention (treatment)

Key Methodologies

The study combined in vitro cell culture experiments with a controlled in vivo dog model to assess cytotoxicity and host response.

1. In Vitro Cytotoxicity Assessment (HeLa Cells)

Electrode Application Modes: Structured ceramic BDD electrodes were tested using two primary modes:
- Potentiostatic Direct: 6 V to 9 V increments applied for 2.5 min directly to cells overlaid with 0.5 mL PBS.
- Amperostatic Direct/Indirect: 50 mA applied for 5 min. Indirect application used PBS buffer pretreated by the electrode, simulating transient radical action.
Control Groups: Cells were treated with standard endodontic irrigants (3% NaOCl, 0.3% NaOCl, 3% H₂O₂, 0.3% H₂O₂, 0.2% CHX, 0.02% CHX) for 5 min.
Viability Assay: Alamar Blue assay was used to measure cell viability based on mitochondrial respiratory chain activity.

2. In Vivo Animal Model and Treatment

Model: Four Jack Russel Terriers (dogs) were used. Maxillary incisors were trepanated to induce infection.
Conventional Treatment: Chemo-mechanical debridement using Hedstroem files and 0.2% chlorhexidine (CHX) solution rinsing.
BDD Treatment: Conventional chemo-mechanical treatment followed by BDD electrode application (Amperostatic mode, 50 mA, 145-360 s).
Restoration: Access cavities were either sealed with composite resin (“sealed”) or left unrestored (“open”). No root canal obturation was performed.

3. Post-Treatment Analysis

Observation Period: Six weeks post-treatment.
Radiographic Analysis: Occlusal radiographs were taken to measure the vertical and horizontal dimensions of periapical radiolucency relative to the root width.
Histologic Analysis: Block sections were harvested, fixed, dehydrated, and embedded in polymethylmethacrylate (Technovit 9100). 70 µm labio-lingual sections were obtained using cutting and grinding techniques and stained with toluidine blue O.
Statistical Analysis: Kruskal-Wallis tests and Nemenyi’s All-Pairs tests (alpha = 0.05) were used to compare radiolucency size across treatment groups.

Commercial Applications

The successful demonstration of safety for BDD electrochemical disinfection opens pathways for commercialization in specialized medical and material science fields.

Advanced Endodontic Devices:
- Development of BDD electrode systems for integration into root canal treatment protocols, potentially replacing or supplementing highly cytotoxic chemical irrigants (e.g., NaOCl).
- The transient nature of the generated OH radicals minimizes systemic risk and localized tissue damage, a critical factor for clinical acceptance.
Peri-Implantitis Treatment:
- Application of BDD technology for the electrochemical disinfection of complex, roughened dental implant surfaces affected by peri-implantitis, where biofilm removal is challenging.
Electrochemical Disinfection Systems (General):
- Leveraging the high efficiency and chemical inertness of BDD electrodes for localized, high-power disinfection in confined biological or fluidic systems.
Structured Electrode Manufacturing:
- Commercialization of the described structured ceramic BDD electrodes, optimized for high current density and robust performance in aqueous electrochemical environments.

View Original Abstract

Boron-doped diamond (BDD) electrodes have been advocated as a potential treatment alternative to the established methods for root canal disinfection. As healing of periapical tissue is important in this context, the associated risk of host tissue damage was to be evaluated. Following in vitro cell culture experiments (HeLa cells), root canal treatment was performed in an animal trial comparing BDD electrode application and the currently used rinsing media with respect to cell viability and host tissue damage. Statistical analyses comparing the size of radiolucency were based on Kruskal-Wallis and Nemenyi’s All Pairs tests (α = 0.05). The direct application of BDD electrodes had a time-dependent effect on cell viability comparable to H2O2, NaOCl, and CHX application. In contrast to the chemical treatment, the effect of BDD electrodes was transient. Conventionally treated teeth and teeth additionally treated with BDD electrodes did not significantly differ from each other with respect to the size of the periapical radiolucency as observed radiographically (vertical p = 0.998 and horizontal p = 0.878) and histologically (vertical p = 0.940 and horizontal p = 0.862). While showing greater disinfection efficiency, the application of BDD electrodes for the electrochemical disinfection of root canals does not have a greater risk of host tissue damage compared to the conventional treatment.

Tech Support

Original Source

DOI: https://doi.org/10.3390/app13148228

References

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