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

Round 1

Reviewer 1 Report

The authors used a combination of in vitro cell culture experiments and 48 animal trial to compare BDD electrode application and currently applied rinsing media 49 with respect to cell viability and host tissue damage. Despite the effort towards the study, the animal study contains a major flaw that compromises publication. Root canal chemomechanical preparation procedures were performed at working length. However, dog teeth do not contain a main apical foramen to connect with the periapical tissues, only an apical delta. If canal is mantained this way, anything used will heal easily, which favors any product outcomes. The procedure would be to overinstrument and create a cemental canal and a main foramen. Therefore, the results in this study may be due to the methodology and comparisons are questionable. I suggest that authors repeat the methodology taking this into account. Also, please consider to follow the PRIASE  guidelines which can be found at https://pride-endodonticguidelines.org/priase

Authors showed to have good acquaintance with the methodology, so if they improve this step, results may be worthy. 

Author Response

The authors used a combination of in vitro cell culture experiments and 48 animal trial to compare BDD electrode application and currently applied rinsing media 49 with respect to cell viability and host tissue damage. Despite the effort towards the study, the animal study contains a major flaw that compromises publication. Root canal chemomechanical preparation procedures were performed at working length. However, dog teeth do not contain a main apical foramen to connect with the periapical tissues, only an apical delta. If canal is mantained this way, anything used will heal easily, which favors any product outcomes. The procedure would be to overinstrument and create a cemental canal and a main foramen. Therefore, the results in this study may be due to the methodology and comparisons are questionable. I suggest that authors repeat the methodology taking this into account.

RE: We do understand and appreciate the point raised by the reviewer and would like to answer as follows. Overinstrumentation is critical and has been shown to result in lower success rates as compared to “proper” instrumentation up to working length, when postoperative pain is considered. The topic itself is ambiguously discussed in the literature and hence if we had followed your advice, one might argue that the results presented would not be clinically realistic (even if the idea of provoking a worst case scenario for an animal trial was understood). Based on that, we had decided to follow common clinical practice. Contrary to your assumption (and as can be seen in the radiographs) the teeth developed periapical lesions indicating that no complete healing had occurred regardless of the preparation technique used. Based on that, we argued that our novel methodology would not cause greater harm as compared to conventional methods. We have added these aspects to the discussion section and kindly ask for your understanding that a dog animal trial cannot simply be repeated.

The respective section in the discussion reads: In this context it may also be argued that mechanical instrumentation only until reaching working length instead of creating apical patency had led to favorable results. Based on a report indicating that maintaining apical patency did not affect endodontic treatment outcomes in teeth with necrotic pulp and apical periodontitis, it was decided not to over-instrument [Arslan 2019]

 

Also, please consider to follow the PRIASE  guidelines which can be found at https://pride-endodonticguidelines.org/priase - Authors showed to have good acquaintance with the methodology, so if they improve this step, results may be worthy. 

RE: Thank you very much for pointing us to both, checklist and flowchart which we have now included

Reviewer 2 Report

Koch et al had a good and important study on Electrochemical disinfection of root canals that bears no risk of damaging periapical tissues. The subject is very important for the ultimate goal of endodontic treatment which is the healing of periapical radiolucency resulting from previous inflammation.

The manuscript needs some main modifications:

The abstract does not include the main sections. It should be rewritten. Besides, the importance of the study and the aims should be clear in the abstract section. 

The introduction does not provide sufficient background and does not include all relevant references. It is so short. The used references are not enough and some recent references are needed. Besides, the importance of the study and the aims should be clear in the introduction section. 

The research design is appropriate. But, the methods need some more details and also references.

Which posthoc test was used for the comparison?

The quality of the figures is low in some cases.

 The conclusions do not supported by the results. 

 

 

 

 

 

Minor editing of English language required

Author Response

Koch et al had a good and important study on Electrochemical disinfection of root canals that bears no risk of damaging periapical tissues. The subject is very important for the ultimate goal of endodontic treatment which is the healing of periapical radiolucency resulting from previous inflammation.

RE: Thanks much for the kind words

The manuscript needs some main modifications: The abstract does not include the main sections. It should be rewritten. Besides, the importance of the study and the aims should be clear in the abstract section.

RE: We have rewritten and re-structured the Abstract following your advice (without subheadings in the paper as per guidelines)

Background

Boron-doped diamond (BDD) electrodes have been advocated as a potential treatment alterna-tive to established methods for root canal disinfection. As healing of periapical tissue is im-portant in this context, the associated risk of host tissue damage was to be evaluated.

Methods

Following in vitro cell culture experiments (HeLa cells), root canal treatment was performed in an animal trial comparing BDD electrode application and currently used rinsing media with re-spect to cell viability and host tissue damage. Statistical analyses comparing the size of radiolu-cency were based on one-way analysis of means and Games-Howell tests (α=0.05).

Results

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 = 0.9974; horizontal p = 0.695) and histologically (vertical p = 0.998; horizontal p = 0.748).

Conclusion

While showing greater disinfection efficiency, the application of BDD electrodes for electro-chemical disinfection of root canals does not have a greater risk of host tissue damage compared to conventional treatment

The introduction does not provide sufficient background and does not include all relevant references. It is so short. The used references are not enough and some recent references are needed. Besides, the importance of the study and the aims should be clear in the introduction section.

RE: We have further elaborated the Introduction and added new references as recommended by reviewers #1 and #3. If there were specific references the reviewer considers being relevant to our work, we are kindly asking to point us to these. Regarding this and the following comment, we would like to point out that the main text of this COMMUNICATION contains >3300 words without references

The research design is appropriate. But, the methods need some more details and also references.

RE: We have further clarified that the basic design follows the protocol reported by Sabeti et al. 2006.

Which posthoc test was used for the comparison?

RE: We have clarified in the materials and methods section that one-way analysis of means was performed prior to pairwise comparisons using Games-Howell tests

The quality of the figures is low in some cases.

RE: We are aware that especially Fig.1 is of low quality (both radiograph and histology are limited in quality due to their small size) but after checking all photos made during the intervention, this is the best photo. If this reviewer considers the figure as being problematic, we would delete it. The graphs included in the paper were made using Excel and could be adapted if not interfering with journal style. Please also see comment made by reviewer #3.

The conclusions do not supported by the results.

RE: We have reworded the conclusions and are even more cautiously now: Based on the results obtained and taking into account that current treatment proto-cols also cause host tissue damage to a certain extent, it may be concluded that the appli-cation of BDD electrodes for electrochemical disinfection of root canals does not bear a greater risk of tissue damage. Clinical studies are inevitable before this method can be recommended.

Reviewer 3 Report

Dear Authors, 

you made a great work! However, some improvements are suggested before acceptance. 

Comments for author File: Comments.docx

Minor Style improvements. 

Author Response

The paper is a communication on the Electrochemical disinfection of root canals that bears no risk of damaging periapical tissues. The Authors made a great work in terms of methodology and the paper sounds scientific and well written.

RE: Thanks much for your kind words

However some improvements are mandatory before acceptance.

The abstract is well written, complete and summary in its various aspects, in the abstract I believe that the description of the manuscript in question could be increased, the background is clear, underline better what the AIM is. The keywords are complete and appropriate.

RE: We have further elaborated on the abstract as also advised by reviewer #2 and we have explicitly stated the aim as follows: As healing of periapical tissue is important in this context, the associated risk of host tissue damage was to be evaluated

 

In the introduction:

• “The ultimate goal of endodontic treatment is healing of periapical radiolucency resulting from previous inflammation [1].” I don't think it's the only goal, and perhaps not even the most important, although representative of a state of health. I think the success criteria of endodontics in this case should be better explained.

RE: We have added the publication by Bergenholtz(2016) defining successful treatment by the absence of apical periodontitis and clinical symptoms after a period of observation

• “Prior to clinical application, the potential risk of host tissue damage by applying electrochemical disinfection has to be estimated.” obviously, I imagine that the channels still need to be found and instrumented to a diameter that allows entry of the electrode, and therefore, although we reduce the risks of tissue damage by acids, and perhaps improve the disinfection of the site, nonetheless we maintain the problems of rotating instrumentation of the canals, with risks of intracanal separation of the instrument, perforations, etc..., as underlined by:

" Zanza A, Seracchiani M, Reda R, Miccoli G, Testarelli L, Di Nardo D. Metallurgical Tests in Endodontics: A Narrative Review. Bioengineering (Basel). 2022 Jan 12;9(1):30. doi: 10.3390/bioengineering9010030."

" Seracchiani M, Reda R, Zanza A, D'Angelo M, Russo P, Luca T. Mechanical Performance and Metallurgical Characteristics of 5 Different Single-file Reciprocating Instruments: A Comparative In Vitro and Laboratory Study. J Endod. 2022 Aug;48(8):1073-1080. doi: 10.1016/j.joen.2022.05.009."

RE: The reviewer is perfectly right; the application of the electrodes requires previous root canal preparation which bears all the risks mentioned. We have added the papers mentioned to the list of references quoting them in the Introduction.

 

Materials and methods are clear and well explained. Different aspects are analyzed with a dedicated statistical test. The authors did a great job in the explication of all the variables identified and included in the study.
In the materials and methods section, the fact of having chosen this methodology of analysis on animals (6 weeks later), is it possible to add references on previous works with this methodology?

RE: The reason for sacrificing the animals six weeks after endodontic treatment was that we wanted to see early stages of inflammation/healing which might no longer be present after e.g. 12 weeks (in the same animals we performed tooth extractions in the mandible and the ridges were completely healed after 12 weeks!). Comparable studies (Sabeti et al. 2006) have used 6 months healing periods but with the hope (aim) of showing, that radiolucency had disappeared. We have added this aspect to the discussion section: Previous work in the same animal model [3] aimed at evaluating resolving periapical ra-diolucency allowed for periapical healing of approximately 6 months. This was not done here as it was anticipated that potential damage due to the use of BDD electrodes might no longer be detectable.

Results are easy to understand and comprehensive. All the studied characteristics were reported in tables which are clear and concise. The images inserted are of excellent quality, the tables easy to understand. Good job.

RE: Thanks much for your kind words

Discussion: this section is complete and evaluates the outcome of different papers present in literature. The overall is comprehensive, concise and complete in its various aspects.

RE: Thanks much for your kind words


Conclusions are concise and clear.

RE: Thanks much for your kind words


Bibliography should be formatted respecting the journal’s requirements and no improper citations are evidenced.

RE: We double checked the bibliography after adding several new references


Figures and labels are clear and easy to comprehend.

RE: Thanks much for your kind words


English is clear and easy to understand.

RE: Thanks much for your kind words

 

Reviewer 4 Report

The clinical relevance, originality, and limitations of the study should be highlighted. 

What is the practical use of the study? 

 

Author Response

The clinical relevance, originality, and limitations of the study should be highlighted.

RE: We have further elaborated on these aspects - please see updated intorduction and discussion

What is the practical use of the study? 

RE: As now stated in the Introduction, this study was required before entering clinical application

Round 2

Reviewer 3 Report

Dear Authors,

Great work!

Author Response

Thanks much