The Effect of Upper Arch Expansion by Clear Aligners on Nasal Airway Volume in Children: A Preliminary Study

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The study explores a timely and clinically relevant topic—how clear aligners for maxillary expansion affect nasal airway volume in children. This research fills a gap in the literature, as most studies focus on traditional methods like rapid maxillary expansion (RME).

Weaknesses:

1. Small Sample Size:
   The study's findings are based on only 11 experimental participants and 7 controls, which limits the generalizability of the results. The control group, in particular, is very small.

   Suggestion: Conduct future studies with larger sample sizes to validate and strengthen the conclusions.

2. Limited Control Group Data:

   • The control group had slightly larger initial nasal airway volumes and an older average age compared to the experimental group, which could introduce bias.
   • The gender imbalance in the control group (more males, who naturally have larger nasal airways) may also skew comparisons.

   Suggestion: Provide a more robust explanation of how these limitations may influence the results, or control for these factors in a larger follow-up study.

3. Lack of Long-Term Follow-Up:
   While the study demonstrates significant changes post-treatment, it does not address whether these changes are stable over time.

   Suggestion: Incorporate long-term follow-up assessments to determine the stability and permanence of nasal airway improvements and intermolar distance changes.

4. Correlation Analysis:
   The correlation analysis between nasal airway volume changes and intermolar distance yielded a very weak relationship (r = -0.029). While statistically valid, this finding lacks explanation or interpretation.

   Suggestion: Discuss potential reasons why nasal airway expansion may not correlate with intermolar distance and explore other contributing factors (e.g., soft tissue adaptations).

 

 

1. This preliminary study is well-executed and offers valuable insights into the potential benefits of clear aligners for maxillary expansion in children. The findings are promising, particularly regarding increases in nasal airway volume and intermolar distance. However, limitations such as the small sample size, retrospective design, and lack of long-term follow-up need to be addressed in future research. Despite these drawbacks, the study adds meaningful evidence to the field of pediatric orthodontics.

Author Response

Dear Editors and Reviewers

Thank you very much for your time to review this manuscript. We really appreciate all your comments and suggestions. They are very helpful for improving our paper as well as providing good ideas for our future research. We have considered these comments carefully and tried our best to address every one of them. The revised manuscript showing these comments highlighted in the manuscript using tracked changes. We also reviewed the references section and made some revisions to ensure that all references were relevant to the manuscript. The responses to the reviewers’ comments are shown below.

 

Responses to Reviewer #1 comments:

First of all, we greatly appreciate your valuable feedback on our manuscript.

Comments 1: Small Sample Size

The study's findings are based on only 11 experimental participants and 7 controls, which limits the generalizability of the results. The control group, in particular, is very small.

Suggestion: Conduct future studies with larger sample sizes to validate and strengthen the conclusions.

Response 1: We agree with the reviewer’s comment and that is why the title stated (A Preliminary study), and we recommended an increase in the sample size in the future to validate and strengthen the conclusions. It was mentioned in the Discussion section of the original manuscript that the control group would need to be expanded in the future (lines 343-344), we added 'the experimental group will also be expanded in the future' in lines (34-35, 345-346).

Comments 2: Limited Control Group Data

The control group had slightly larger initial nasal airway volumes and an older average age compared to the experimental group, which could introduce bias.

The gender imbalance in the control group (more males, who naturally have larger nasal airways) may also skew comparisons.

Suggestion: Provide a more robust explanation of how these limitations may influence the results, or control for these factors in a larger follow-up study.

Response 2: The authors agree with the reviewer’s comment, and we have addressed this in the limitations of the study in the revised manuscript (lines 334-344) as well as added 3 more references (Reference 27, 28, and 29) to show that older age and more males lead to larger nasal airways. For this reason, the results of this study should be interpreted with caution. Also, we added a comment to increase the sample size and try to control these factors in future study (lines 34-35, 343-344).

Comments 3: Lack of Long-Term Follow-Up

While the study demonstrates significant changes post-treatment, it does not address whether these changes are stable over time.

Suggestion: Incorporate long-term follow-up assessments to determine the stability and permanence of nasal airway improvements and intermolar distance changes.

Response 3: The authors agree with the reviewer’s comment and we added a recommendation for a long-term follow-up study in the future to investigate the changes in nasal airway volume as well as intermolar distance after treatment. This has been mentioned in the revised manuscript (lines 34-35, 346-348), thank you.

Comments 4: Correlation Analysis

The correlation analysis between nasal airway volume changes and intermolar distance yielded a very weak relationship (r = -0.029). While statistically valid, this finding lacks explanation or interpretation.

Suggestion: Discuss potential reasons why nasal airway expansion may not correlate with intermolar distance and explore other contributing factors (e.g., soft tissue adaptations).

Response 4: Considering the Reviewer’s suggestion, we added a discussion of this correlation in the Discussion section. (Lines 321-334)

We would like to express our special thanks for your valuable suggestions.

Reviewer 2 Report

Comments and Suggestions for Authors

Peer Review Report

Title: The Effect of Upper Arch Expansion by Clear Aligners on Nasal Airway Volume in Children: 

We appreciate the considerable effort made by the authors in conducting this study. The work is interesting and addresses an important topic. However, there are several critical issues that compromise the publication of the study in its current version. Below is the report with observations and suggestions that we hope will be useful for improving the study.

Preliminary Study

General Observations: This study explores the effect of upper arch expansion using clear aligners on nasal airway volume in pediatric patients. While the manuscript provides valuable preliminary insights, there are several methodological and conceptual issues that require clarification or additional justification.

1. Abstract:

• The inclusion of obstructive sleep apnea (OSA) in the introduction and abstract appears unnecessary as the study does not diagnose or directly evaluate OSA in the participants. If OSA is not a measured outcome, its relevance should be omitted or framed as a broader context without misleading implications.
• The abstract should explicitly state that no causal relationships are claimed due to the study design.

2. Introduction:

• The introduction draws a tenuous connection between OSA and the study outcomes without providing a clear rationale. If OSA is not part of the study’s diagnostic or treatment criteria, it should not dominate the context.
• Expansion and its relationship with OSA require further exploration. If the aim is to assess airway volume, this should be the primary focus.

3. Study Design:

• The retrospective cohort design is prone to inherent biases. The authors should address how they mitigated these biases, particularly in participant selection and data consistency.
• Sample size justification is mentioned but lacks transparency. While 7 participants were determined as the minimum for paired t-tests, the rationale behind excluding participants from the control group (initially 12, reduced to 7) should be elaborated. How were participants chosen or excluded?

4. Materials and Methods:

• Control Group Intervention: The control group reportedly underwent no intervention. This raises concerns about the observed negative correlation between nasal airway volume and intermolar distance. If no intervention was applied, why did nasal volume decrease and intermolar distance change? This requires clarification or an acknowledgment of potential measurement errors.
• CBCT Scanning Parameters: The thresholds for Hounsfield units (-1024 to -600) are mentioned but lack a rationale. How were these values determined? Were these parameters validated for consistency across all scans?
• Removal of Maxillary Sinus: The method for excluding maxillary sinus contributions to nasal airway volume could influence results. How did the authors ensure this removal did not distort the final volume measurements?
• Head Positioning: The retrospective design does not describe procedures for standardizing head positioning during CBCT scans. Variations in head tilt or alignment could introduce systematic errors. This limitation should be addressed.
• Operator Bias: It is unclear whether blinding was applied to operators performing segmentation, cleaning, or noise removal of volumes. Lack of blinding could introduce subjective bias.
• Noise Removal: The repeated cleaning of noise during segmentation could manipulate measurements. Clear and reproducible descriptions of this process should be included to assess reliability.
• Swallowing and Airway Conditions: Measures to prevent swallowing or ensure consistent airway conditions during CBCT scans should be described.

5. Statistical Analysis:

• The statistical analysis software used for paired t-tests and reliability tests is not mentioned. This information is essential for reproducibility.
• Reliability Metrics: The reported ICC values are high, but further statistical indicators such as Dahlberg’s error or SD values should be included to assess systematic errors. The study should address why the control group exhibited higher variation in volume measurements compared to the experimental group.
• Control Group Volume Decrease: The observed decrease in nasal airway volume for the control group is unexplained. Since participants are pediatric patients in a growth phase, this finding contradicts expectations. Could this result from errors in head positioning, segmentation, or noise removal?

6. Results:

• The low and negative correlation between intermolar distance and nasal airway volume is not well-explained. The authors should explore possible reasons why increases in one parameter might coincide with decreases in the other, particularly for the control group.

• An intraclass correlation coefficient (ICC) test was conducted, yielding high values. However, the measurements showed a standard deviation ranging from 733.0 to 1308.7 mm³, corresponding to a coefficient of variation of 9% for T1 and 7.86% for T2 in the control group, and 7.0% for T1 and 7.68% for T2 in the experimental group. This discrepancy suggests a systematic error in the measurements between the control and experimental groups. It is recommended that, in addition to reporting the ICC, the Dahlberg error statistic and its standard deviation (SD) be included to better evaluate the reliability of the data.

  This systematic error, combined with the noise-cleaning process performed twice without a clear description of the methodology, raises concerns about the accuracy of the results. Furthermore, as a retrospective study, the lack of a clear protocol for head positioning during radiographic imaging could have influenced the measurement of the posterior boundary of the nasal volume, as illustrated in the figures. This may help explain the average volume decrease of -648.3 mm³ and the negative correlation of -0.768, which is difficult to justify in growing patients. It is worth noting that the exclusion criteria ruled out inflammatory factors that could have influenced the nasal volume decrease.

  A fundamental issue is that, as the authors themselves acknowledge, some studies report an increase in nasal airway volume following expansion procedures that alter the mid-palatal suture, consequently increasing molar width. However, molar modifications theoretically should not result in a generalized increase in nasal volume without orthopedic or surgical expansion. Molar expansion is expected to primarily affect the transverse shape of the arch rather than the nasal volume.

  Without a clear explanation for the negative volume changes in the control group, the proper methodology for head positioning during imaging, the definition of the posterior boundary of the airway volume, and the noise-cleaning process, as well as ensuring that a blinded operator performs the segmentation and noise removal, the authors cannot robustly discuss their findings or compare them to studies involving orthopedic maxillary expansions.

7. Discussion:

• The discussion compares findings with other studies using orthopedic maxillary expansion but fails to address the inherent differences between clear aligners and traditional expansion methods. Clear aligners primarily alter dental arch form rather than affecting skeletal structures, which should theoretically limit their impact on nasal airway volume.
• The negative correlation in the control group should be discussed in detail. Without intervention, a decrease in nasal airway volume contradicts natural growth trends and raises questions about methodological accuracy.

8. Methodological Limitations: The study's retrospective nature and reliance on repeated noise cleaning introduce concerns about systematic error. Additionally:

• Lack of standardized head positioning could influence posterior airway boundary measurements.
• Noise cleaning performed multiple times by potentially unblinded operators compromises objectivity.
• The negative volume changes in the control group require further exploration or acknowledgment as a limitation.

9. Recommendations for Improvement:

• Provide a detailed justification for the inclusion of OSA in the context of this study.
• Clarify the rationale for Hounsfield unit thresholds and describe efforts to standardize CBCT head positioning.
• Include additional reliability metrics (e.g., Dahlberg error) and address systematic errors in the control group.
• Discuss the impact of clear aligner expansion on airway volume separately from orthopedic or surgical maxillary expansion methods.
• Reassess noise-cleaning methods to ensure objectivity and reproducibility.

Conclusion:

The study provides important preliminary data on the effects of upper arch expansion using clear aligners on nasal airway volume and intermolar distance in pediatric patients. However, the methodology exhibits several areas of opportunity that require significant refinement. The observed inconsistencies, such as the unexplained decrease in nasal airway volume in the control group, lack of standardized head positioning during CBCT scans, and potential systematic errors introduced during repeated noise cleaning and segmentation processes, weaken the reliability of the findings. Furthermore, the theoretical framework linking dental expansion via clear aligners to nasal airway volume changes requires more robust justification and differentiation from studies involving orthopedic or surgical maxillary expansion.

Given these substantial methodological concerns, the study cannot be considered for publication in its current form. Clarification and detailed adjustments to address the identified biases and limitations are essential to ensure the validity and reliability of the conclusions.

Author Response

Dear Editors and Reviewers

Thank you very much for your time to review this manuscript. We really appreciate all your comments and suggestions. They are very helpful for improving our paper as well as providing good ideas for our future research. We have considered these comments carefully and tried our best to address every one of them. The revised manuscript showing these comments highlighted in the manuscript using tracked changes. We also reviewed the references section and made some revisions to ensure that all references were relevant to the manuscript. The responses to the reviewers’ comments are shown below.

Responses to Reviewer #2 comments:

First of all, we greatly appreciate your valuable feedback on our manuscript.

Comments 1: Abstract

The inclusion of obstructive sleep apnea (OSA) in the introduction and abstract appears unnecessary as the study does not diagnose or directly evaluate OSA in the participants. If OSA is not a measured outcome, its relevance should be omitted or framed as a broader context without misleading implications.

The abstract should explicitly state that no causal relationships are claimed due to the study design.

Response 1: The authors agree with the reviewer’s comment. We revised the abstract and introduction to reflect these comments. In the abstract, we stated that due to the study design, no causal relationship can be drawn between maxillary expansion using clear aligners on obstructive sleep apnea (lines 35-37). We also mentioned this in the discussion section (lines 349-351). In the introduction section, we placed OSA in a broader context. OSA was only listed as one of the possible effects when discussing the impact of maxillofacial abnormalities on children (lines 41-90). Thank you.

Comments 2: Introduction

The introduction draws a tenuous connection between OSA and the study outcomes without providing a clear rationale. If OSA is not part of the study’s diagnostic or treatment criteria, it should not dominate the context.

Expansion and its relationship with OSA require further exploration. If the aim is to assess airway volume, this should be the primary focus.

Response 2: Thanks for the reviewer's suggestion. We have revised the abstract and Introduction sections accordingly (lines 35-37, 41-90).

Comments 3: Study Design

The retrospective cohort design is prone to inherent biases. The authors should address how they mitigated these biases, particularly in participant selection and data consistency.

Sample size justification is mentioned but lacks transparency. While 7 participants were determined as the minimum for paired t-tests, the rationale behind excluding participants from the control group (initially 12, reduced to 7) should be elaborated. How were participants chosen or excluded?

Response 3: We thank the reviewer for the valuable comment. Clarification of this issue has been added in the revised manuscript (Lines 101-105). In addition, we highlighted in the manuscript that reliability analyses (intra-reliability and inter-reliability) have been conducted and the results showed consistency both between and within researchers. (Lines 219-226, 233-235, 263-268, 280-284) I’m not sure if this is the consistency that you're referring to, if it's not please let me know.

We are very sorry for the misunderstanding caused by our incorrect expression. We have changed “similar” to “same” in line 125 of the revised manuscript. The inclusion criteria for the control group were the same as those for the experimental group (lines 124-126).

Comments 4: Materials and Methods

Control Group Intervention: The control group reportedly underwent no intervention. This raises concerns about the observed negative correlation between nasal airway volume and intermolar distance. If no intervention was applied, why did nasal volume decrease and intermolar distance change? This requires clarification or an acknowledgment of potential measurement errors.

CBCT Scanning Parameters: The thresholds for Hounsfield units (-1024 to -600) are mentioned but lack a rationale. How were these values determined? Were these parameters validated for consistency across all scans?

Removal of Maxillary Sinus: The method for excluding maxillary sinus contributions to nasal airway volume could influence results. How did the authors ensure this removal did not distort the final volume measurements?

Head Positioning: The retrospective design does not describe procedures for standardizing head positioning during CBCT scans. Variations in head tilt or alignment could introduce systematic errors. This limitation should be addressed.

Operator Bias: It is unclear whether blinding was applied to operators performing segmentation, cleaning, or noise removal of volumes. Lack of blinding could introduce subjective bias.

Noise Removal: The repeated cleaning of noise during segmentation could manipulate measurements. Clear and reproducible descriptions of this process should be included to assess reliability.

Swallowing and Airway Conditions: Measures to prevent swallowing or ensure consistent airway conditions during CBCT scans should be described.

 

Response 4:

Control Group Intervention: We thank the reviewer for the valuable comment. As discussed above and in the revised version of the manuscript (lines 321-334), nasal airway volume can be changed due to hormonal changes or other factors. Also, their reduced nasal airway volume may be due to further deterioration of their condition caused by a lack of timely treatment after their initial clinic visit (added in lines 317-320). There was nearly no change in the distance between the molars in the control group, it just became 0.3mm longer, which is very small compared to the 2.4mm in the treatment group. Changes in intermolar distance in the control group could be attributed to normal growth changes.

CBCT Scanning Parameters: The choice of this range was based on experience from our previous study. Yes, we verified that this range was consistent across all scans. We mentioned in the methods section of the manuscript that after creating the mask using this range, we checked each scan slice by slice to complete the segmentation (added ‘slice by slice’ in line 145).

Removal of Maxillary Sinus: We first used the software Mimics for segmentation, which has been widely validated in numerous previous studies and is capable of accurately excluding regions of no interest. Furthermore, to minimize researcher bias, complex areas were thoroughly discussed among all researchers and resolved through consensus. As mentioned earlier, we also conducted intra-reliability and inter-reliability (repeatability) tests to verify measurement consistency and to confirm that excluding the maxillary sinus did not introduce any changes or inconsistencies in the final nasal airway volume measurements among researchers. Additionally, in the discussion section of the manuscript, we mentioned that the removal of the sinus was intended to ensure that the measurements were not affected by this complex region and to standardize the study methods (lines 304-309). And, two more references were added (line 307).

Head Positioning: We agree with the reviewer, however in this office standardized head positioning is confirmed as there is only one person who acquires the CBCT at the office and all positioning is standardized in the office provided the CBCTs. We addressed this in the revised manuscript (lines 132-135).

Operator Bias: The blinding was also applied to the segmentation, measurement, and analysis of the models (We added the explanation in lines 101-105). Regarding the spikes removal of the models in Geomagic, we used standardization to avoid researcher subjective bias (the smoothness level was set to 70 in the software, added in lines 160-161). This value is based on experience and provides a good smoothing of the model while producing negligible changes to the volume of the model.

Noise Removal: As mentioned above, the normalization value used for noise removal has been added in lines 160-161. We first remove the spikes of the model (a description of smoothness level was added), then we cut the imperfect alignment at the anterior and posterior boundary parts (This step is just to make sure that on the basis of the defined front and back boundary points (Fig. 1-d), the T1 model and the T2 model are not out of the range of that defined front and back boundary.). We were thinking of adding pictures to further explain, but the Geomagic software we were using has been retired. But we originally described this in detail in words (lines 159-169).

Swallowing and Airway Conditions: According to the reviewer's suggestion, I added a description in lines 132–135 about the measures we implemented to ensure the accuracy and consistency of the airway during the scan.

Comments 5: Statistical Analysis

The statistical analysis software used for paired t-tests and reliability tests is not mentioned. This information is essential for reproducibility.

Reliability Metrics: The reported ICC values are high, but further statistical indicators such as Dahlberg’s error or SD values should be included to assess systematic errors. The study should address why the control group exhibited higher variation in volume measurements compared to the experimental group.

Control Group Volume Decrease: The observed decrease in nasal airway volume for the control group is unexplained. Since participants are pediatric patients in a growth phase, this finding contradicts expectations. Could this result from errors in head positioning, segmentation, or noise removal?

Response 5: We are very sorry that we neglected to include the statistical analysis software used in the study. I have added it in lines 210-211.

About reliability metrics, we added the Dahlberg error in the revised manuscript (lines 225-226, 265-267, 281-282). The Dahlberg error was calculated to be 68.7 mm³, which is minimal (0.79%) compared to the actual volume of the model (8731.1 mm³). Therefore, the modelling, segmentation, and measurement methods, as well as the results obtained, are reliable. Regarding the greater variation in nasal airway volume mentioned for the control group: the age, height, weight, etc. of the children all have an effect on nasal airway volume. The greater variability in the control group may be due to a more decentralized distribution of nasal airway volumes among the children in the control group.

About Control Group Volume Decrease, we explained in the first section (Control Group Intervention) of Response 4. This has been clarified in the revised manuscript (lines 317-332).

Comments 6: Results

The low and negative correlation between intermolar distance and nasal airway volume is not well-explained. The authors should explore possible reasons why increases in one parameter might coincide with decreases in the other, particularly for the control group.

Response: We thank the reviewer, and these have been explained above and addressed in the revised manuscript. (lines 317-334)

An intraclass correlation coefficient (ICC) test was conducted, yielding high values. However, the measurements showed a standard deviation ranging from 733.0 to 1308.7 mm³, corresponding to a coefficient of variation of 9% for T1 and 7.86% for T2 in the control group, and 7.0% for T1 and 7.68% for T2 in the experimental group. This discrepancy suggests a systematic error in the measurements between the control and experimental groups. It is recommended that, in addition to reporting the ICC, the Dahlberg error statistic and its standard deviation (SD) be included to better evaluate the reliability of the data.

Response: We thank the reviewer. As mentioned above, we added the Dahlberg error in the revised manuscript (lines 225-226, 265-267, 281-282). Since the Dahlberg error is primarily used to measure the error between two measurements by a single researcher, rather than the error between measurements by multiple researchers, we calculated the Dahlberg error in the intra-reliability test (With the exception of the principal researcher, the other researchers did not perform repeated segmentations and measurements for a single model. Therefore, Dahlberg error was calculated for the principal investigator only.). The Dahlberg error was calculated to be 68.7 mm³, which is minimal (0.79%) compared to the actual volume of the model (8731.1 mm³). Combining the previously obtained results of intra-reliability and inter-reliability tests, it can be concluded that the modelling, segmentation, and measurement methods, as well as the results obtained, are reliable. In addition, in this study, we believe that SD only reflects the differences in the size of nasal airway volume among the individuals in the sample. Factors such as gender, weight, and height of children in the growing period can affect the size of nasal volume.

This systematic error, combined with the noise-cleaning process performed twice without a clear description of the methodology, raises concerns about the accuracy of the results. Furthermore, as a retrospective study, the lack of a clear protocol for head positioning during radiographic imaging could have influenced the measurement of the posterior boundary of the nasal volume, as illustrated in the figures. This may help explain the average volume decrease of -648.3 mm³ and the negative correlation of -0.768, which is difficult to justify in growing patients. It is worth noting that the exclusion criteria ruled out inflammatory factors that could have influenced the nasal volume decrease.

Response: We thank the reviewer, all of these have been responded above and addressed in the revised manuscript. (lines 225-226, 265-267, 281-282, 159-169, 132-135, 317-334)

A fundamental issue is that, as the authors themselves acknowledge, some studies report an increase in nasal airway volume following expansion procedures that alter the mid-palatal suture, consequently increasing molar width. However, molar modifications theoretically should not result in a generalized increase in nasal volume without orthopedic or surgical expansion. Molar expansion is expected to primarily affect the transverse shape of the arch rather than the nasal volume.

Response: We agree with the reviewer and this has been clarified in the revised manuscript thanks (lines 332-334).

Without a clear explanation for the negative volume changes in the control group, the proper methodology for head positioning during imaging, the definition of the posterior boundary of the airway volume, and the noise-cleaning process, as well as ensuring that a blinded operator performs the segmentation and noise removal, the authors cannot robustly discuss their findings or compare them to studies involving orthopedic maxillary expansions.

Response: We thank the reviewer, and all these issues have been responded above and addressed in the revised manuscript. (lines 317-334, 132-135, 159-169, 101-105)

Comments 7: Discussion

The discussion compares findings with other studies using orthopedic maxillary expansion but fails to address the inherent differences between clear aligners and traditional expansion methods. Clear aligners primarily alter dental arch form rather than affecting skeletal structures, which should theoretically limit their impact on nasal airway volume.

The negative correlation in the control group should be discussed in detail. Without intervention, a decrease in nasal airway volume contradicts natural growth trends and raises questions about methodological accuracy.

Response 7: As responded above, we discussed negative correlation and volume decrease in the revised manuscript (lines 317-334), thank you.

Comments 8 Methodological Limitations: The study's retrospective nature and reliance on repeated noise cleaning introduce concerns about systematic error. Additionally:

Lack of standardized head positioning could influence posterior airway boundary measurements.

Noise cleaning performed multiple times by potentially unblinded operators compromises objectivity.

The negative volume changes in the control group require further exploration or acknowledgment as a limitation.

Response 8: We thank the reviewer, these issues have been responded above and addressed in the revised manuscript. (lines 225-226, 265-267, 281-282, 159-169, 132-135, 101-105, 317-334)

Comments 9: Recommendations for Improvement

Provide a detailed justification for the inclusion of OSA in the context of this study.

Clarify the rationale for Hounsfield unit thresholds and describe efforts to standardize CBCT head positioning.

Include additional reliability metrics (e.g., Dahlberg error) and address systematic errors in the control group.

Discuss the impact of clear aligner expansion on airway volume separately from orthopedic or surgical maxillary expansion methods.

Reassess noise-cleaning methods to ensure objectivity and reproducibility.

Response 9: We thank the reviewer, OSA was only listed as one of the possible effects when discussing the impact of maxillofacial abnormalities on children in the introduction section as mentioned above. The introduction section was changed as mentioned above (lines 41-90). We have also made corresponding emphasis in the abstract and the discussion sections. (lines 35-37, 349-351)

As mentioned above, the choice of this range was based on experience from our previous study. The range can very well contain our region of interest and on this basis we can mitigate the time required for segmentation. And, this range was consistent across all scans. We mentioned in the methods section of the manuscript that after creating the mask using this range, we checked each scan slice by slice to complete the segmentation (added ‘slice by slice’ in line 1425). Regarding the standardization of head positioning, all participants' heads were in the same position and angle when the CBCT scans were performed (lines 132-135).

The Dahlberg error was added as mentioned above (lines 225-226, 265-267, 281-282).

We mentioned in the revised manuscript that maxillary dentoalveolar expansion using clear aligners is not expected to perform skeletal expansion (lines 332-334). And we also explained the negative correlation (lines 321-334).

We responded to this above based on objectivity and reproducibility, thanks.

Comments 10: Conclusion

The study provides important preliminary data on the effects of upper arch expansion using clear aligners on nasal airway volume and intermolar distance in pediatric patients. However, the methodology exhibits several areas of opportunity that require significant refinement. The observed inconsistencies, such as the unexplained decrease in nasal airway volume in the control group, lack of standardized head positioning during CBCT scans, and potential systematic errors introduced during repeated noise cleaning and segmentation processes, weaken the reliability of the findings. Furthermore, the theoretical framework linking dental expansion via clear aligners to nasal airway volume changes requires more robust justification and differentiation from studies involving orthopedic or surgical maxillary expansion.

Given these substantial methodological concerns, the study cannot be considered for publication in its current form. Clarification and detailed adjustments to address the identified biases and limitations are essential to ensure the validity and reliability of the conclusions.

Response 10: The conclusion has been revised accordingly. Thank you. We sincerely appreciate your valuable suggestions and the time you devoted to reviewing our research.

 

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

This study assessed the correlations between the maxillary expansion using clear aligners and the intermolar distance.

Main question addressed by the research: maxillary expansion using clear aligners can increase maxillary intermolar width and increase nasal airway volume in children with constricted maxilla?

The topic is original and relevant in the field. The subject has a limited study in the field; thus, this study covers the missing data gaps. It clearly shows that an aligner can induce maxillary intermolar increase. It combines both FEA images and in vivo data.

Introduction - provided sufficient data for the reader to understand the subject

Materials/method – sufficient data to understand the methodology, with both statistical and measurements data

Results – supports the methodology and aims, are properly presented

Discussion – properly discussed. However, in order to enhance the manuscript, I suggest that the correlation section be expanded.

Conclusions -properly supported and consistent with the arguments as well as with the research aims.

References- are proper and appropriate

I recommend acceptance after minor revisions related to the discussion section.

Author Response

Dear Editors and Reviewers

Thank you very much for your time to review this manuscript. We really appreciate all your comments and suggestions. They are very helpful for improving our paper as well as providing good ideas for our future research. We have considered these comments carefully and tried our best to address every one of them. The revised manuscript showing these comments highlighted in the manuscript using tracked changes. We also reviewed the references section and made some revisions to ensure that all references were relevant to the manuscript. The responses to the reviewers’ comments are shown below.

Responses to Reviewer #3 comments:

First of all, we greatly appreciate your valuable feedback on our manuscript.

This study assessed the correlations between the maxillary expansion using clear aligners and the intermolar distance.

Main question addressed by the research: maxillary expansion using clear aligners can increase maxillary intermolar width and increase nasal airway volume in children with constricted maxilla?

Response: Yes.

The topic is original and relevant in the field. The subject has a limited study in the field; thus, this study covers the missing data gaps. It clearly shows that an aligner can induce maxillary intermolar increase. It combines both FEA images and in vivo data.

Introduction - provided sufficient data for the reader to understand the subject

Materials/method – sufficient data to understand the methodology, with both statistical and measurements data

Results – supports the methodology and aims, are properly presented

Discussion – properly discussed. However, in order to enhance the manuscript, I suggest that the correlation section be expanded.

Response: We strongly agree that a deep discussion of the obtained correlation results would enhance the article. A discussion of the correlation was added to the manuscript in lines 321-334.

Conclusions -properly supported and consistent with the arguments as well as with the research aims.

References- are proper and appropriate

I recommend acceptance after minor revisions related to the discussion section.

Once again, thank you for the time you spent reviewing the manuscript and for your valuable suggestions.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have replied to all my comments