Effect of Different Downward Loads and Rotational Speeds on the Removal of Gutta-Percha and Root Canal Sealer Using a Nickel-Titanium Rotary Gutta-Percha Removal System: An Ex Vivo Study

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

Thank You for a pleasure to read Your article.

I have several comments to improve Your article.

Sincerely, Reviewer

 

Title

Please, add the study type for better understanding.

 

Abstract

Please, add probabilities for results.

Please, add information about micro-CT in this section.

 

Keywords: please, check them with MeSH.

 

Materials and methods

Subsection 2.1. Please, explain why You did not use correction for sample size possible drop-out.

Subsection 2.2.

Please, write the base of simulation in reisin blocks as it is far from real tooth canal. Also,  there is need to add information about rate of straight canals in Dental practice for better understanding of Your work actuality (for example, in the introduction or discussion).

Please, write in the legend for figure 1 the investigation methods and technique with details.

Subsection 2.4 Please, write the difference with Your previous articles (Ref.16,17).

Subsection 2.6. Lines 153-154- please, write the details of specimens randomization.

Subsection 2.7. Please, write what exactly two-way tests You used.

 

Results

Please, write accurate numbers for probabilities besides p<0.05. Also, please, make better the figures 3-5. The system of significance is not clear, please, make it easier for understanding.

 

Discussion

It is strange to compare the results of Your study with Your other works. Please, use scientific literature for similar topic even there is now the same article.

Please, make the subsection Study limitations visible with title.

 

Conclusion

Please, enlarge this section according to results of Your study.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript is well-organized and demonstrates a solid methodological framework. However, I recommend some minor revisions aimed at improving the clarity, scientific rigor, and overall quality of the manuscript.

Materials and methods

Please clarify whether the effect size estimated from the sample is small, medium, or large.

Results

The comment referring to a previous reviewer’s suggestion (Lines 209–211) appears to have been inadvertently left in the manuscript and should be removed.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Effect of different downward loads and rotational speeds on the removal of gutta-percha and root canal sealer using a nickel-titanium rotary gutta-percha removal system

 

General comments

1. The manuscript is generally well written and addresses a clinically relevant and persistent challenge in endodontics, the effective removal of gutta-percha and sealer during nonsurgical retreatment while minimizing damage to the canal walls.
2. The introduction is appropriate and supported by recent references. However, it would benefit from a stronger emphasis on the specific knowledge gap addressed by the present experimental design, particularly regarding the combined influence of downward load and rotational speed on removal efficiency and torque generation.
3. The methodological design and experimental techniques appear appropriate. Nevertheless, several methodological, analytical, and interpretative aspects require clarification to improve reproducibility, and clinical relevance.

 

Major comments

1. Sample size calculation and effect size justification. The manuscript refers to the targeted effect size but does not provide the sample size calculation formula, nor does it clearly justify the selection of this specific effect size, particularly given the presence of six experimental groups.

Please include the sample size calculation formula, the statistical parameters used, and an appropriate reference.

The selected effect size appears arbitrary. Were other effect sizes reported in similar studies considered? Several previous investigations on NiTi retreatment instruments have reported small-to-moderate effect sizes depending on the outcome variable (e.g., torque, force, removal efficiency), which may influence the adequacy of the chosen sample size.

2. Storage conditions and sealer setting time

In the methods section, the following sentence requires justification. Please provide a reference supporting the selection of a 4-week storage period. Although extended storage times have been used in previous studies to simulate complete sealer maturation, the rationale for this duration should be explicitly stated.

“The specimens were stored at 37°C in a 100% humidified incubator for 4 weeks to allow complete sealer setting.”

 

3. Selection of rotational speeds and downward loads

The criteria used to select the tested rotational speeds (400 and 800 rpm) and downward loads (2, 3, and 4 N) are not sufficiently explained. Were these parameters based on manufacturer recommendations, previous experimental studies, or preliminary testing?

4. Statistical analysis

Were the assumptions of normality and homogeneity of variances verified for all outcome variables, considering the relatively small sample size per group?

The rationale for using Bonferroni correction should be justified. While Bonferroni is conservative, alternative post hoc tests (e.g., Tukey) are commonly used in factorial designs when normality assumptions are satisfied.

5. Presentation of results

In the graphical presentation of results, the use of “different uppercase letters” to indicate statistical differences is not intuitive for readers without strong statistical training. Given the complexity of the experimental design, a clearer visualization strategy is recommended (Consider using explicit symbols, brackets, or annotations indicating which specific group comparisons are statistically significant).

6. Discussion

Several statements, particularly in the second paragraph, are presented without adequate referencing and should be supported by relevant literature.

The discussion should move beyond a descriptive restatement of the results and instead:

Compare the findings with previous studies on NiTi retreatment instruments, torque generation, and operational parameters.

Explain the observed effects of load and rotational speed from a biomechanical and clinical perspective.

The authors should explicitly acknowledge the limitations of the study.

The clinical implications of the findings should be discussed. How might clinicians translate these results into safer or more effective retreatment strategies?

The originality of the study should be clearly highlighted, emphasizing how it advances current understanding beyond existing literature.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

Thank You for Your manuscript improvement.

Sincerely, Reviewer

Reviewer 3 Report

Comments and Suggestions for Authors

No additional comments