3D-Printed Metal Surgical Guide for Endodontic Microsurgery (a Proof of Concept)

Round 1

Reviewer 1 Report

1. Line 93-94, Authors please check the unit and clarify the FOV.

2. All software has the internal error which is different from the real measurement. Using the virtual implant placement as the reference along with the software measurement will be double errors. The author should comparatively discuss and explain the reason why selecting to use the virtual implant placement and software measurement instead of the real measurement.

3. Why the author do not confirm with the real measure after using the CT scan since the samples were not destroyed? Author can add into the discussion. 

4. Authors please revise the conclusion.

Author Response

R1

1. Line 93-94, Authors please check the unit and clarify the FOV.

Thank you for the excellent review of our manuscript. We apologize for this mistake; we checked, modified, and clarified the FOV.

Revised text: “Preoperative CBCT scans of all jaws were obtained with a Orthophos XG 3D CBCT unit (Dentsply Sirona, York, Pennsylvania, USA) with an 8 cm x 8 cm field of view and a 0.16-mm voxel size. The parameters were 85 kV, 6 mA, with an exposure time of 14.2 s.”

2. All software has the internal error which is different from the real measurement. Using the virtual implant placement as the reference along with the software measurement will be double errors. The author should comparatively discuss and explain the reason why selecting to use the virtual implant placement and software measurement instead of the real measurement.

We agree to say that all software has the internal error which is different from the real measurement. We considered that this internal error would have a minimal impact. The two metallic screws fixed in each mandible helped us to assess the minimal difference between software and real measurement. Postoperative CBCT volumes were superimposed on the preoperative volumes, and the distances between the actual drill paths and the target points were measured. We also agree that some imprecision may be associated with this methodology. Previous studies have used both preoperative and postoperative CBCT scan datasets for measuring the angular deviation:

• Fan Y, Glickman GN, Umorin M, et al (2019) A Novel Prefabricated Grid for Guided Endodontic Microsurgery. J Endod 45:606–610. https://doi.org/10.1016/j.joen.2019.01.015
• Connert T, Zehnder MS, Weiger R, et al (2017) Microguided Endodontics: Accuracy of a Miniaturized Technique for Apically Extended Access Cavity Preparation in Anterior Teeth. J Endod 43:787–790. https://doi.org/10.1016/j.joen.2016.12.016
• Ackerman S, Aguilera FC, Buie JM, et al (2019) Accuracy of 3-dimensional – printed endodontic surgical guide: A human cadaver study. J Endod 45:615–618
• Zehnder MS, Connert T, Weiger R, Krastl G (2015) Guided endodontics : accuracy of a novel method for guided access cavity preparation and root canal location. 1–7. https://doi.org/10.1111/iej.12544

3. Why the author do not confirm with the real measure after using the CT scan since the samples were not destroyed? Author can add into the discussion. 

Thank you for this kind suggestion. Indeed, to confirm the real measure, we also used implant drill placed in the drill path and took optical scans of the results. The measurements were not conclusive since the scan bodies were not stable. We added sentences in the discussion related to the point raised.

Revised text: “Previous studies have used preoperative and postoperative CBCT scan datasets to measure angular deviation [14,26]. However, a limitation exists in this protocol since all software has the internal error which is different from the real measurement. CBCT scan datasets may differ due to different orientation of objects. In our study, a specific guide was created to correctly position the jaws. A “scan body” of the implant placed in the drilled path could have been used to allow for the addition of scan datasets. However, this method requires the body scans to be stable in the drilled path.”

Authors please revise the conclusion.

As kindly suggested, we revised the conclusion.

Revised text: “To the best of our knowledge, this study is the first to consider the use of 3D-printed surgical metal guides in perspective of EMS applications. Before translation to human therapeutic, further studies should be conducted to determine the predictability and to compare with traditional resin guides. This proof-of-concept study demonstrate the fea-sibility in an ex vivo model and suggest the potential for such guides during EMS procedures.”

Reviewer 2 Report

The scientific paper "3D-printed metal surgical guide for endodontic microsurgery (a proof of concept)” proposes a study in order to evaluate the accuracy of new 3D printed surgical metal guides (SMGs) with open-frame structure in ex vivo condition. Accuracy was assessed by comparing virtually planned implants with the bone drilled implants in terms of apical and angular deviations.

I can make the following considerations as the Authors may improve their work by following these suggestions:

Remove the “The introduction” in the first sentence of the Introduction.

Join the last two paragraphs in the Introduction section.

In the section 2. Materials and Methods there should be a workflow diagram explaining the whole procedure from start to finish. I believe it would improve the manuscripts clarity and it would be easier for future readers and audience to follow it more easily.

Parameters used for preoperative CBCT scanning should be placed in a table for better visibility (Sub-section 2.2. Experimental procedure)

Figures and text under figures should be formatted according to the Journals Guide for Authors. This is in reference to labeling of descriptions under figures ((a), (b), (c),..), it should be placed before the description, not after it. Please correct this for all Figures.

What was the reason for manual step-by-step segmentation of all postoperative CBCT images?

Sentence “…guaranteeing precise and repeatable overlaying.” (line 140) – replace “precise” with “accurate” as it is not the same in the context of the performed operation.

Formula for Euclidean distance should be placed according to the Formatting of Mathematical Components in Journals Guide for Authors.

A better illustration of the measured apical and angular deviations should be performed. Figure 3b does not depict it clearly.

For measurement procedure why were all measurements repeated only three times?

I believe that a Figure showing the alignment of the drill path and initial plan in 3Shape Implant Studio software should be added, to better clarify this step.

2D analysis performed in this manuscript is in order. But, what about geometrical 3D analysis (ie. CAD Inspection)? I believe 3D analysis could provide both dimensional and visual insight (color deviations) about displacement that occurs between preoperative 3D plan and postoperative CBCT  3D model. This is also very important from the quality management aspect as it ensures proper procedures to be carried out in the same way each time.

For better clarity avoid splitting of Table 1 onto two pages. Same goes for headline of References section.

Author Response

R2

The scientific paper "3D-printed metal surgical guide for endodontic microsurgery (a proof of concept)” proposes a study in order to evaluate the accuracy of new 3D printed surgical metal guides (SMGs) with open-frame structure in ex vivo condition. Accuracy was assessed by comparing virtually planned implants with the bone drilled implants in terms of apical and angular deviations. I can make the following considerations as the Authors may improve their work by following these suggestions:

 Remove the “The introduction” in the first sentence of the Introduction.

Thank you for the excellent review of our manuscript. We apologize for this mistake, we removed “The introduction” in the first sentence of the introduction.

Join the last two paragraphs in the Introduction section.

As kindly suggested, we joined the last two paragraphs in the introduction section.

In the section 2. Materials and Methods there should be a workflow diagram explaining the whole procedure from start to finish. I believe it would improve the manuscripts clarity and it would be easier for future readers and audience to follow it more easily.

Thank you for this suggestion that would help future readers to follow the procedure. We included a workflow diagram.

Parameters used for preoperative CBCT scanning should be placed in a table for better visibility (Sub-section 2.2. Experimental procedure).

We clarified the sentences related to preoperative CBCT scanning.

Revised text: “Preoperative CBCT scans of all jaws were obtained with a Orthophos XG 3D CBCT unit (Dentsply Sirona, York, Pennsylvania, USA) with an 8 cm x 8 cm field of view and a 0.16-mm voxel size. The parameters were 85 kV, 6 mA, with an exposure time of 14.2 s.”

Figures and text under figures should be formatted according to the Journals Guide for Authors. This is in reference to labeling of descriptions under figures ((a), (b), (c),..), it should be placed before the description, not after it. Please correct this for all Figures. 

As kindly suggested, we placed the labeling of descriptions before the description for all figures.

What was the reason for manual step-by-step segmentation of all postoperative CBCT images?

We apologize for the mistake; segmentation was automatically done.

Revised text: “the drill path was automatically segmented via a slice-by-slice method and transformed into a three-dimensional virtual model”

Sentence “…guaranteeing precise and repeatable overlaying.” (line 140) – replace “precise” with “accurate” as it is not the same in the context of the performed operation.

Thank you for this suggestion, we edited the text.

Formula for Euclidean distance should be placed according to the Formatting of Mathematical Components in Journals Guide for Authors.

As mentioned in the Journals Guide for Authors, we used the Microsoft Equation Editor Equations is editable by the editorial office and not appear in a picture format.

A better illustration of the measured apical and angular deviations should be performed. Figure 3b does not depict it clearly.

As kindly suggested, we added an illustration showing calculation of deviation and edited the caption of the figure.

For measurement procedure why were all measurements repeated only three times?

All measurements were repeated three times by a blinded endodontist and a general practitioner familiar with the software who were not involved in the planning or surgeries times. This number was based on a preliminary pilot study where we considered that it would not be necessary to increase the number of repeated measurements as this did not influence the results. We added this precision to the text and also added sentences to the discussion.

Revised text: “The distance measurements were manually calculated by two blinded observers (endodontist and a general practitioner familiar with the software). Although this methodology was based on a preliminary study, this may have led to small errors on the calculations. The use of computer software to automatically calculate the deviation between planned and performed drill path by registering preoperative and postoperative CBCT scans may be relevant for future studies.”

I believe that a Figure showing the alignment of the drill path and initial plan in 3Shape Implant Studio software should be added, to better clarify this step.

As kindly suggested, we included a figure showing the alignment of the drill path and initial plan in figure 4d.

2D analysis performed in this manuscript is in order. But, what about geometrical 3D analysis (ie. CAD Inspection)? I believe 3D analysis could provide both dimensional and visual insight (color deviations) about displacement that occurs between preoperative 3D plan and postoperative CBCT  3D model. This is also very important from the quality management aspect as it ensures proper procedures to be carried out in the same way each time.

We totally agree to say that 3D analysis could provide both dimensional and visual insight.

For better clarity avoid splitting of Table 1 onto two pages. Same goes for headline of References section.

As kindly suggested, we modified Table 1 to fit in one page and for headline of References section.

Reviewer 3 Report

Dear Authors, 

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

Comments for author File: Comments.pdf

Author Response

R3

The paper is a communication on the 3D-printed metal surgical guide for endodontic microsurgery. The Authors made a great work in terms of methodology and the paper sounds scientific and well written. However, some improvements are mandatory before acceptance. Too many double spaces were found during the revision: please fix it.

Thank you for the excellent review of our manuscript and the nice comments. We apologize for the double spaces. We carefully edited the manuscript.

The abstract is well written, complete and summary in its various aspects. The keywords are complete and appropriate.

The introduction is comprehensive and gives a good overview of the problem addressed in the manuscript.

In the introduction

“When performing EMS, management of vital anatomic structures and the adjacent root apex is crucial (including the inferior alveolar nerve, sinus, nasal cavity, greater palatine artery, and mental foramen).” as far as this topic is concerned, absolutely correct in this section of the mansuscript, I underline how important a correct study of the dental anatomy is, as a further limiting factor and difficulty of this type of intervention. In particular, the possibility of finding complex apical conformations 3mm from the apex, which could represent a difficulty in a complete 3D filling, represents a problem, in addition to the proximity to noble structures, as underlined by: “Reda R, Zanza A, Bhandi S, Biase A, Testarelli L, Miccoli G. Surgical-anatomicalevaluation of mandibular premolars by CBCT among the Italian population. Dent Med Probl. 2022 Apr-Jun;59(2):209-216. doi:10.17219/dmp/143546.”

We totally agree with the comment related to the dental anatomy. We added the recent reference to the introduction section.

The materials and methods are detailed and well described, in the light of this, why did the authors choose a "communication" and not an original research for this “ex-vivo” manuscript as the form of the manuscript?

As kindly suggested, we modified the type of article to “original research”

In the discussion:

How do the authors believe to manage the subsequent root canal filling with diameters of this type of sleeves for endodontic surgery?

For the obturation step, the SMG would not be necessary, and we would traditionally root canal filling with hydraulic silicate calcium cements under magnification (microscope).

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.

Conclusions are concise and clear.

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

Figures and labels are clear and easy to comprehend.

English is clear and easy to understand.

Thank you

Reviewer 4 Report

Great work! 

I suggest some additional information that I believe can enrich the manuscript, as well as some further small notes.

Comments for author File: Comments.pdf

Author Response

R4

The manuscript is a “Communication” on the 3D-printed metal surgical guide for endodontic microsurgery. Please check the too many double spaces found during the revision: please fix it.

Thank you for the excellent review of our manuscript and the nice comments. We apologize for the double spaces. We carefully edited the manuscript.

The abstract is complete. Please check if all the keywords are mesh terms. The introduction is discursive and very well written.

As kindly suggested, we checked and edited the keywords.

In the introduction:

• “In particular, the lower molars have been reported to have a lower success rate than other teeth due to their visual and instrumental access difficulties [1].” moreover, the important question represented by the presence of endodontic lesions of dimensions and shapes that sometimes make a micro-surgical procedure very complex, with undercuts or cavities that are difficult to cleanse or treatable with mechanical debriment, must always be considered, especially with the difficulty of accessing the posterior sectors, as underlined by: “Hajihassani N, Ramezani M, Tofangchiha M, Bayereh F, Ranjbaran M, Zanza A, Reda R, Testarelli L. Pattern of Endodontic Lesions of Maxillary and Mandibular Posterior Teeth: A Cone-Beam Computed Tomography Study. J Imaging. 2022 Oct 20;8(10):290. doi: 10.3390/jimaging8100290.”

We totally agree with the comment related to the dental anatomy. We added the recent reference to the introduction section.

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. Why does the Authors choose “Communication” for this manuscript?

As kindly suggested, we modified the type of article to “original research”

Results are easy to understand and comprehensive. All the studied characteristics were reported in tables which are clear and concise.

In the discussion:

In the discussion:

The overall is comprehensive and well written.

The possibility of using this full digital technique is very interesting, but often, for the lingual tissues in the lower arch, it could be useful to take a mucocompressive impression to facilitate the detailed reading of the tissues, necessary for the creation of an adequate surgical guide.

Thank you for this comment

Conclusions are concise and clear.

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

Figures and labels are ok.
English is clear and easy to understand.

Thank you

Reviewer 5 Report

The study is a good effort that will lead a way to future studies with large sample size.

Author Response

R5

The study is a good effort that will lead a way to future studies with large sample size.

Thank you for the nice comment

Round 2

Reviewer 2 Report

The Authors did acknowledge most of my remarks for their manuscript, and improved it substantially.

One small correction should be performed, but do not require additional revision on my part:

Formula for Euclidean distance should be numbered with (1) (line 152) according to the Formatting of Mathematical Components in Journals Guide for Authors.

=√?2+?2+?2                                                                        (1)

Reviewer 4 Report

Dear Authors, 

Congratulations! I think the manuscript is now suitable for acceptance! Great Work!