Mechanical Properties of NiTi Rotary Files Fabricated through Gold-Wire, CM-Wire, T-Wire, and R-Phase Heat Treatment
Round 1
Reviewer 1 Report
Keep up the good work!
Author Response
We deeply appreciate the time and effort spent on reviewing this manuscript.
The manuscript was revised according to reviewers' comments.
Reviewer 2 Report
Reviewer's comments on manuscript applsci-2211613
Mechanical Properties of NiTi Rotary Files Made with Gold-wire, CM-wire, T-wire, and R-phase Heat Treatment
This paper reports on various measurements of NiTi rotary files for endodontic treatment. Basically the study is well structured and conducted, the text is well written and has a clear expression. Unfortunately there are a lot of minor problems that have to be solved before acceptance. I recommend major revision.
Specific comments:
Abstract
1) Line 19: Please add some numbers. It is interesting to be able to judge the bending resistance and elastic modulus already in the abstract.
2) Line 22: ‘Mechanical properties of NiTi files were affected by the heat-treatment dependent phase composition.’ This is an absolutely general and more than well-known statement for NiTi alloys. If this is the key conclusion, I do not see any new aspect in this study! But might be in the main text there is some more information! If so, this should be replaced here.
Introduction
3) Line 34: ‘The mechanical properties of NiTi instruments…’ Again, this is an absolutely general statement for ALL NiTi alloys. So please change NiTi instruments to NiTi alloys as is done further below. You might add: ‘The mechanical properties of NiTi alloys, and thus for NiTi instruments, …’
4) The paragraph line 34 – 52 on heat treatment: To my knowledge, every NiTi alloy (wire, file, others) need heat treatment after mechanical treatment. So this is a little bit misleading. Only the treatment schemes differ and are a speciality of the different products/manufacturers. But heat treatment has to be done each time after a mechanical treatment step. So I recommend that this paragraph is slightly rephrased.
5) Paragraph line 61-66: Take care! Upon treatment, the file will be inserted into the root canal, which should have around 37 °C and due to the rotation some heat will be produced, further increasing the temperature of the file. So it is irrelevant, which characteristics the file or NiTi alloy shows at room temperature. The only relevant behaviour is that at body temperature and slightly above!
OK, I now saw it is discussed further below. But it should be mentioned briefly here as well!
6) Line 73: ‘The objective of this study is…’ – the objective WAS?
Materials and Methods
7) Line 94: Please add ISO3630 to the references!
8) Line 109: ‘The stress measured…’ How could you measure the stress? I know how to measure forces, torques, displacements, angles… But how was the stress measured? Is there a strain gauge sensor anywhere in the machine and is it attached to the files? Or is it just the wrong word here?
9) Line 111: What is (gf)? Gram-force? Why do you give the buckling resistance in gf and the bending resitance in Ncm? Please be consistent and state the buckling resistance in SI units as well! Same for the results presentation of course.
10) Line 127: Which quantity describes the ultimate torsional strength? This is not stated here. I assume the maximum measured torque. Please state! In Ncm or Nmm?
11) ‘…and the elastic modulus (EM) was deter-128 mined from the slope…’ It must be absolutely clear that deriving the elastic modulus from this curve can only be an extremely rough estimate! The geometry of the file is extremely inhomogeneous and as the geometry has to be taken into consideration when calculating the moment of area, it would be interesting how the authors did this! Do you have a formula? You need the moment of inertia to derive the EM from the slope. Or you calculated something else…
Results
12) General: Please add some numerical values in the text here as well. Some people want to understand without checking every second the tables.
13) Line 161, Table 2: There are absolutely no units given for these results. What is it? Bending resistance might be given in Ncm, buckling in gf, but NCF, ARF, UTS, EM? OK, one might search and pick it out somewhere in the text. But I do not want to do this. Same holds for most of the readers, I assume! Give units of measure, in SI units of course! Then it is not good style to state a part of the parameters in full name, others in abbreviations. And: What is for example: 1.346 ± 0.168? I assume mean and standard deviation. State in the legend! Finally: If you have standard deviations starting at the first decimal place, it is completely ridiculous to state the mean with 3 decimal places. Results do not get more precise just by stating as much decimal places as possible! Round and delete decimal places. This result shows how wrong this is: 641.39 ± 91.80. An error of around 15 %! And the result is stated with 2 decimal places. Here we do not need any decimal place. Delete, delete!
14) Figure 2: The Y axis titles are missing! Please give reasonable titles on the Y axis. And do not give the units in (). According to ISO, units have to be given as follows: Bending Resistance in Ncm. Correct for all subfigures!
15) Figure 2F: OK, I see! This is NOT an elastic modulus that has been derived here. It is special some kind of stiffness modulus that does not have anything to do with Young’s modulus. Please correct in the whole text!
16) Line 201: ‘The ProfaTaper 201 Gold same…’ What does the same mean? I think ‘as well’.
Discussion
17) Line 303 and following: ‘In addition, according to the heating curve of the DSC plot of ProfaTaper Gold (Figure 6C), ProfaTaper Gold exists a mixed state of austenite, martensite, and R-phase at 22 ℃.’ This sentence is somewhat weird. Especially the ‘ProfaTaper Gold exists a mixed state’ seems to be grammatically incorrect. Do you mean ‘exists in a mixed state’?
Rest of the discussion seems to be fine. So, please extract some relevant statement for the last sentence in the abstract.
Conclusion
Most of what is presented here is just repetition of results and discussion. I miss a clinically relevant statement here!
Author Response
We deeply appreciate the time and effort spent on reviewing this manuscript.
Authors' response to reviewer's comments are attached.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
The presented paper is devoted to the mechanical properties of the different NiTi files. The authors conducted tests to assess bending, buckling, cyclic fatigue, and torsional fracture resistance. Different commercially available files were used for the study. This work can be accepted for publication after major revision with the corrections and improvements. Reviewer has the following commentaries:
11/ In the introduction section, heat treatments were mentioned multiple times for different rotary NiTi files. However, the authors did not develop a discussion on the exact regimes that result in particular phase composition or material properties. A broad discussion of heat treatment modes should be added.
22/ In the research dedicated to different technologies of NiTi files manufacturing despite the classical grinding or twisting, while additive manufacturing approach can be implemented [ex. 10.1007/s11837-020-04013-x; 10.3390/ma15196556]. It is recommended to reflect this in the introduction section.
33/ In the experimental section, the authors mentioned that commercially available NiTi files were used for the research. However, in the next passage, the authors point out that “All NiTi files were prepared using heat treatment “. Without a precise explanation of heat treatment and chemical composition, this cannot be applicable to a scientific journal as far as the material is not described extensively.
44/ According to the description of the cyclic fatigue test, no force sensor was used. How did the authors differentiate the moment of fracture in the steel channel?
It should be noted that a drop in the force required for introducing a file to the channel could happen before any visible fracture. Thus, the time at which such a drop of force occurs allows to precisely calculate the number of cycles. If the authors did not use any force sensor the results of fatigue tests cannot be reliable.
55/ Fig. 6 has only 2 plots, 5 DSC curves are missing. In Fig. 6 the parts connected with preheating from room temperature (begging of a cycle) should be excluded from the DSC curves as it may be confusing for a broad audience.
66/ The main disadvantage of the paper is the absence of an explanation dedicated to the reasons for different mechanical properties from the material science point. Only statistical analysis, SEM, and DSC analysis were presented.
77/ The conclusion about the fracture mode in lines 171-172 should be more detailed.
88/ The sentence “It is suggested that the large number of K3XF threads used may contribute to this reduction in buckling resistance” is unclear (lines 255-256).
99/ The conclusions of the study involve only comparative analysis between commercially available NiTi files and have no scientific significance.
Overall English level is low. Many typos and grammar errors are present. Some sentences are completely meaningless (lines 285-286: “ProTaper Gold had the highest UTS value, whereas ARF had the lowest (Figure 2D,E)”.
Author Response
We deeply appreciate the time and effort spent on reviewing this manuscript.
Authors' response to reviewer's comments are attached.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors have done an excellent job, congratulations! The only thing I have to criticise is that nickel titanium has been deleted. To my opinion, every abbreviation, even if it is one for a chemical element, has to be introduced. But this might be solved during copy editing, especially if it was a comment from the editor or a reviewer.
Author Response
'NiTi', an abbreviation for nickel-titanium was added in the revised manuscript.
Thank you again for guiding us to revise the manuscript properly.
Reviewer 3 Report
Unfortunately, I did not receive direct answers to my comments. The authors are convinced of their innocence and do not want to take into account other points of view. I do not see scientific novelty in the work done and therefore is recommended to reject.
Author Response
Once again, we revised manuscript according to editor's comment.
And we deeply appreciate the time and effort spent on reviewing this manuscript.
