Impact of Radial Lands on the Reduction of Torque/Force Generation of a Heat-Treated Nickel-Titanium Rotary Instrument
Maria Goreti Fernandes
Round 1
Reviewer 1 Report
This is a study on some effects of radial lands in a two-instrument sequence (25/04, then 25/06) after manual glide path preparation in endodontic training blocks.
This is a sound study, and the authors obviously know what they are doing. The text is also short and concise. I have merely a few minor suggestions.
Line 31 (Introduction): that sentence is confusing. Please change it to: However, intracanal fracture of these instruments is a problem that has not yet been fully resolved.
Line 73 (Introduction): The problem of comparing apples and oranges when testing different file systems because of the multiple parameters that differ between these has been highlighted and addressed before (Deari et al. PMID: 32358847, DOI: 10.1111/iej.13319).
Line 141 (Materials and Methods): What is the rationale for using an EDTA-containing lubricant in a plastic block? Even in real teeth, it does not help much. It is always better to keep a water-based liquid in the canal system.
Author Response
Response to Reviewer 1 Comments
- Line 31 (Introduction): that sentence is confusing. Please change it to: However, intracanal fracture of these instruments is a problem that has not yet been fully resolved.
→Thank you for pointing this out. We have modified the sentence accordingly.
- Line 73 (Introduction): The problem of comparing apples and oranges when testing different file systems because of the multiple parameters that differ between these has been highlighted and addressed before (Deari et al. PMID: 32358847, DOI: 10.1111/iej.13319).
→Thank you for pointing this out. We have added one sentence in the 5th paragraph in Introduction. Three refareces have been added.
Our changes
" Thus, some studies have compared instruments with the same geometry but different heat-treatment [22, 24, 25]." (page 2, lines 75–76).
- Line 141 (Materials and Methods): What is the rationale for using an EDTA-containing lubricant in a plastic block? Even in real teeth, it does not help much. It is always better to keep a water-based liquid in the canal system.
- →Thank you for your valuable comment. In the clinical condition, RC-Prep is recomennded to use as chelating agent and was used in previous studies (Hülsmann M et al. PMID: 14641438, DOI: 10.1046/j.1365-2591, Ha, J.H et al. PMID:23429968, DOI:5395/rde.37.215). This study used RC-Prep as a lubricant and for simulating clinical condition.
Reviewer 2 Report
The work focuses on rotating instruments, which is a drawback at the moment because such instruments can produce significant forces on root dentin during instrumentation and induce microcracks and vertical fractures. The authors investigated the impact of radial lands on torque/force generation and canal-shaping ability, using an experimental non-landed instrument (non-landed JZ) for comparison. However, the study has some limitations and points that need to be clarified.
Introduction: The authors mentioned that the study was designed to determine the effect of the one-sided radial-landed design of JZ on the torque/force generation and canal-shaping ability, under a condition where the impact of other influencing factors is minimized. Therefore, my question is how the authors mitigate the effect of other variables. Which factors are you referring to? Please provide additional information on that.
Material and methods: Resin root canal models were used to test the JZ and non-landed JZ. However, there are limitations with the use of simulated canals in resin blocks because their physical properties are different from those of extracted teeth. What are the advantages and disadvantages of using these types of models? For instance, how does fluid dynamics (canal irrigation) affect torque/force generation? The study's limitations should be thoroughly documented and described, as they may jeopardize the obtained results;
A figure of experimental setup should be added;
What is the load cell's characteristic? capacity for force? Accuracy? And what about strain gauges? Please provide additional information on that.
What argument did the authors use to select operational parameters such as 50mm/min velocity and 500rpm? Kindly justify your selections.
Results: clearly identify and describe the lowercase letters in figures 2, 3, and 4.
The authors mentioned that no deformation or fracture occurred during the experiment. Have you checked for microcracks? How can you be certain that microcrack was not begun or propagated?
Please revise all manuscript. Make sure the lettering and sizing are consistent throughout the document.
Author Response
Response to Reviewer 2 Comments
- Introduction: The authors mentioned that the study was designed to determine the effect of the one-sided radial-landed design of JZ on the torque/force generation and canal-shaping ability, under a condition where the impact of other influencing factors is minimized. Therefore, my question is how the authors mitigate the effect of other variables. Which factors are you referring to? Please provide additional information on that.
→Thank you for your valuable comment. We have added additional informations in the 5th paragraph in Introduction.
Our changes
" Taking these concerns into account, we designed this study to determine the effect of the one-sided radial-landed design of JZ on the torque/force generation and canal-shaping ability, under a condition where the impact of other influencing factors, such as heat-treatment, taper, pitch length and instrumentation protocol, is minimized. To achieve this, we employed an experimental NiTi rotary instrument (termed non-landed JZ; Figure 1B), which is a non-landed counterpart of JZ with identical metallurgy and almost the same geometrical features." (page 2, lines 81–82).
- Material and methods: Resin root canal models were used to test the JZ and non-landed JZ. However, there are limitations with the use of simulated canals in resin blocks because their physical properties are different from those of extracted teeth. What are the advantages and disadvantages of using these types of models? For instance, how does fluid dynamics (canal irrigation) affect torque/force generation? The study's limitations should be thoroughly documented and described, as they may jeopardize the obtained results;
→Thank you for your valuable comment. We have added more explanation for simulated canals in resin blocks in the 2nd paragraph in Discussion.
Our changes
" Simulated resin canals were employed in the present study to standardize the analysis by excluding morphological differences inherent in natural root canals [27]. In particular, simulated resin canals are more suitable for providing standardized evaluation with direct visual comparison of the centering ratio compared with natural root canals [18, 28]. Thus, many studies have used resin canals as a valid alternative to natural root canals to investigate torque/force generation [29, 30] and canal transportation [31, 32] during root canal instrumentation. However, the use of simulated resin canals has limitations because their physical properties such as hardness that differs from those of real teeth [33]. Resin canals are softer and have a smoother surface texture than dentin and may require less force to cut [34]; nevertheless, instrumentation in resin canals may generate larger stress than in human root dentin because rotary instruments may become entangled in shavings and heat-softened resin [35]. In this regard, future studies using extracted teeth may provide more clinically relevant implications." (page 7, lines 289–300).
- A figure of experimental setup should be added;
→Thank you for your valuable comment. We have added Figure 2 showing our experimental setup.
- What is the load cell's characteristic? capacity for force? Accuracy? And what about strain gauges? Please provide additional information on that.
→Thank you for your valuable comment. We have added more information on the load cell and strain gauges in the 4th paragraph in Material and Methods.
Our changes
" Briefly, the device con sisted of a test stand with a moving stage (MX2-500N; IMADA, Aichi, Japan), and the torque/force measuring unit, consisted of a load cell (LUX-B-ID; Kyowa, Tokyo, Japan; rated capacity, ± 50 N; nonlinearity, within ± 0.15% of rated output) and strain gauges (KFG-2-120-D31-11; Kyowa; foil type; strain limits at room temperature, approximately 5%), was connected to the model to measure the apical/coronal vertical loads and clockwise torque, respectively. A liner correlation has been confirmed between the distortion values measured by the strain gauges and torque values [12]" (page 3, lines 132–139).
- What argument did the authors use to select operational parameters such as 50mm/min velocity and 500rpm? Kindly justify your selections.
→Thank you for your valuable comment. An up-and-down speed of 50 mm/min was chosen based on a previous study [Maki, K et al. PMID: 30558799, DOI: 10.1016/j.joen], which has been mentioned in the first paragraph in Discussion. The rotation speed was set at 500 rpm according to the manufacturers’ recommendation, as stated in the third paragraph in the section 2.3.
Our changes
" An up-and-down speed of 50 mm/min was set based on a previous study [10]." (page 7, lines 284–285).
- Results: clearly identify and describe the lowercase letters in figures 2, 3, and 4.
→Thank you for your valuable comment. We have modified the Figures.
- The authors mentioned that no deformation or fracture occurred during the experiment. Have you checked for microcracks? How can you be certain that microcrack was not begun or propagated?
→ Thank you for your valuable comment. We examined all instruments used for instrumentation with a surgical operating microscope. This information has been added in the 6th paragraph in Material and methods.
Our changes
" All instruments used for instrumentation were examined with a surgical operating microscope (OPMI pico, Carl Zeiss, Gottingen, Germany) at ×21.3 magnification for any possible defect or distortion (plastic deformation)." (page 4, lines 155–158).
Round 2
Reviewer 2 Report
The manuscript has been improved sufficiently to justify publishing in Applied Sciences.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
