Are Linear Cephalometric Measurements Interpreted Equally Across Birth Cohorts? Cross-Sectional Cephalometric Study

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for your submission, reviewing cephalometric measurements across different birth cohorts.

The images reviewed were those of patients who had sought orthodontic treatment. Are these people representative of the general population and if so, how do you know this? If they were undergoing orthodontic treatment, there is presumably a deformity present.

Did you exclude patients who underwent orthognathic surgery subsequent to the imaging?

How did you ascertain that there were no extrinsic factors affecting facial growth? For example, prolonged CPAP in childhood causes restriction in facial growth.

Were all images taken using the same equipment?

Were the patients in each cohort the same age when the images were taken?

Was ethnic variation taken into consideration?

 

 

Author Response

RESPONSE TO REVIEWERS

Reviewer 1

Dear Reviewer,

We consider your observations to be very valuable and believe they have strengthened our manuscript. We hope that our responses have been adequate and have addressed the questions you raised. The specific modifications corresponding to your comments are highlighted in green. Some of your observations overlapped with those of other reviewers; therefore, you may also find paragraphs highlighted in colors other than yellow. We remain attentive to your response.

Kind regards.

 

Comment 1

Are these people representative of the general population?

Response: We appreciate this relevant observation regarding external validity. The study population corresponds to a clinical orthodontic population rather than a general population sample. Records were randomly selected from the available database to reduce selection bias within treated patients. Therefore, findings are applicable to clinical orthodontic settings but not generalizable to the Mexican population. The purpose of the study was to evaluate the interpretive performance of cephalometric norms in the context where they are actually applied.

Added paragraph:  The study population represents individuals seeking orthodontic care at a single clinical center. Records were randomly selected from the available clinical database to reduce selection bias within that treated population. However, the sample is not a representative sample of the Mexican population or of Mexico City. This limits population-level generalization. At the same time, the clinical setting mirrors real-world application, which supports the practical relevance of the findings.

 

Comment 2

Did you exclude patients who underwent orthognathic surgery subsequent to the imaging?

Response: We agree that clarifying this point is important for interpreting the clinical sample. Patients with previous orthognathic surgery were excluded. However, individuals presenting surgical indications at diagnosis were retained to preserve the clinical spectrum encountered in orthodontic practice. Adjustment for sagittal skeletal classification limits case-mix bias.

Added paragraph: Patients with previous craniofacial or orthognathic surgery were excluded. Patients presenting surgical indications were retained to preserve clinical variability. Adjustment for sagittal skeletal classification limits potential bias due to case composition.

 

Comment 3

How did you ascertain that there were no extrinsic factors affecting facial growth (e.g., CPAP)?

Response: We appreciate the need to clarify potential uncontrolled exposures. Individual environmental exposures were not directly measured. However, such exposures are unlikely to cluster systematically within a birth cohort group and would introduce random variability rather than directional bias in a cross-sectional comparison.

Added paragraph: Individual exposures potentially affecting craniofacial development were not directly assessed; however, such factors are unlikely to systematically cluster within a single birth cohort group and would tend to introduce non-directional variability rather than a consistent pattern.

 

Comment 4

Were all images taken using the same equipment?

Response: Thank you for requesting this methodological clarification. Yes. All radiographs were obtained using the same cephalometric equipment.

 

Comment 5

Were patients the same age across cohorts?

 

Response: We agree that age comparability is essential in this context. Only adults (≥18 years) were included and analyses were adjusted for age group, preventing confusion between growth and cohort-associated differences.

 

Comment 6

Was ethnic variation considered?

Response: We appreciate the importance of considering potential population stratification. Ethnicity was not recorded. However, large metropolitan Mexican populations show high admixture and limited intra-urban stratification, making systematic alignment between ancestry and birth cohort groups unlikely.

Added paragraph: Ethnic background was not recorded. Large metropolitan populations in Mexico are highly admixed and unlikely to align systematically with birth cohort groups. Unmeasured ethnic variation would therefore increase dispersion rather than produce consistent directional differences.

 

Comment 7

Summarise limitations of cited literature

Response: We agree that positioning our study relative to previous literature is necessary. We clarified that previous studies addressed growth patterns, historical untreated samples, or population genetics rather than clinical interpretive validity.

 

Added paragraph: Developmental studies mainly describe maturation differences [11], historical growth collections use untreated non-clinical samples [15], and genomic studies describe population structure rather than diagnostic interpretation [16].

 

Comment 8

Specify “birth cohort context”

Response: Thank you for highlighting the need for conceptual clarity. We provided a definition and its relevance for cephalometric interpretation.

Added paragraph: The term birth cohort context refers to shared early-life environmental and population conditions influencing measurement distributions rather than individual morphology.

Reviewer 2 Report

Comments and Suggestions for Authors

1. regarding citing 11,15,16 - summarise their key limitations to make your results more concret
2. "birth cohort context"-  please briefly specify wat it encompasses
3. 361  to 365 line - use shorter sentences 

 

Comments on the Quality of English Language

use shorter sentences 

 

 

Author Response

Reviewer 2

Dear Reviewer,

We greatly appreciate your comments and believe they have improved the quality of our manuscript. We hope our replies satisfactorily address the points you raised. The revisions related specifically to your suggestions are highlighted in green. As some of your remarks overlapped with those from other reviewers, you may also notice passages marked in colors other than green. We look forward to your feedback.

Kind regards.

 

Comment 1

Clarify refs 11,15,16

Response: We appreciate this request for clearer contextualization. We clarified the limitations of previous literature directly in the Discussion section. Rather than relying on specific citations alone, the manuscript now explains conceptually that prior studies often evaluate developmental change or population differences without separating generational context or adjusting for clinical modifiers. This allows the reader to understand how the present study differs in interpretive scope.

 

Added paragraph:Many studies do not clearly separate generational context from individual developmental processes. Previous investigations comparing craniofacial dimensions across populations or generations have not consistently accounted for relevant clinical modifiers, which limits the interpretive equivalence of reference values across patient groups.

 

Comment 2

Define birth cohort context

Response:We agree that defining this concept improves interpretability. We provided a definition and its relevance for cephalometric interpretation.

Added paragraph:The term birth cohort context refers to shared early-life environmental and population conditions influencing measurement distributions rather than individual morphology.

 

Comment 3

Shorter sentences

We found your observation very valuable and have revised and rewritten both the Introduction and Discussion sections accordingly. The modifications were aimed at improving clarity, logical flow, coherence, and overall readability, while reducing redundancy and overly long paragraphs. We hope this revised version is clearer and more satisfactory.

Reviewer 3 Report

Comments and Suggestions for Authors

The article "Are Linear Cephalometric Measurements Interpreted Equally Across Birth Cohorts? Cross-Sectional Cephalometric Study" evaluates wheather linear cephalometric measurements are different in their central values across three birth cohorts: < 1980, 1980-1989, 1990-1999.

The article is well structured in 5 sections: Introduction, Materials and Methods, Results, Discussion and Conclusions and presents a descriptive statistics regarding 11 linear cephalometric measurements in different cohort groups. The Introduction and Materials and Methods section are appropriately written, but for Results and Discussion there are several comments:

• In the Results section is mentioned a Tabel 1 " Distributions of age, group, sex, birth cohort and sagittal skeletal classification", but I couldn't find it.
• Since Table 3  is very large, I would suggest a more detailed interpretation of the results; also related to skeletal class , considering that in the study are linear measurements of the mandibular length, corpus length, maxillary length
• In Figure 2 and Figure 3 there are some discrepancies related to birth cohort groups. For example, in Figure 3 there are 2 birth cohort groups 1980-1999 and 2000-2009 that were not mentioned in the Materials and Methods

Author Response

Reviewer 3

Dear Reviewer,

 

We greatly appreciate your comments and believe they have improved the quality of our manuscript. We hope our replies satisfactorily address the points you raised. The revisions related specifically to your suggestions are highlighted in pink. As some of your remarks overlapped with those from other reviewers, you may also notice passages marked in colors other than pink. We look forward to your feedback.

 

Kind regards.

 

Comment 1: In the Results section is mentioned a Tabel 1 " Distributions of age, group, sex, birth cohort and sagittal skeletal classification", but I couldn't find it.

 

Response: We appreciate this observation and apologize for the oversight. The table was previously placed in the supplementary materials; however, it has now been relocated to the Results section in accordance with the text, and no supplementary information remains.

 

Comment 2 : Since Table 3  is very large, I would suggest a more detailed interpretation of the results; also related to skeletal class , considering that in the study are linear measurements of the mandibular length, corpus length, maxillary length

Response: We appreciate this clinically important suggestion. Analyses were adjusted for sagittal skeletal classification and differences persisted, indicating variation within skeletal patterns rather than case-mix change. In addition, other reviewers and the editor recommended improving clarity and readability. Therefore, we expanded the explanation slightly while avoiding excessive detail to prevent confusion regarding the main objective of the study. We hope this clarification adequately addresses your concern.

Added paragraph: A secondary aspect emerges when considering skeletal classification. Key linear measurements, including maxillary length (Co–A), mandibular length (Co–Gn), and corpus length (Go–Gn), showed lower central values in more recent birth cohort groups relative to the reference cohort. Because these contrasts persisted after controlling for skeletal class, they do not reflect changes in diagnostic composition but differences within each skeletal pattern. Clinically, patients sharing the same sagittal classification may therefore present different absolute linear dimensions depending on birth cohort group, so values appearing short or long relative to historical norms may still correspond to typical measurements in contemporary patients

Comment 3:  In Figure 2 and Figure 3 there are some discrepancies related to birth cohort groups. For example, in Figure 3 there are 2 birth cohort groups 1980-1999 and 2000-2009 that were not mentioned in the Materials and Methods.

 Response: We agree with the reviewer and apologize for the confusion. In the figure only two groups were displayed because one of the birth cohort groups was used as the reference category in the regression analysis. For this reason, the graph was presented in that format. We have now added a brief explanation in both the figure legend and the main text to clarify this point. We appreciate this observation, which helped us improve the clarity of the manuscript.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for submitting your response and revised manuscript which I have read.

It seems that you have grouped males and females together in each cohort. I would expect there to be intrinsic differences between a male facial skeleton and a female facial skeleton, particularly in the linear measurements. Did you look at each gender separately at all and is there a difference?

Author Response

Comment 1: It seems that you have grouped males and females together in each cohort. I would expect there to be intrinsic differences between a male facial skeleton and a female facial skeleton, particularly in the linear measurements. Did you look at each gender separately at all and is there a difference? 

Response 1: We appreciate this insightful observation. Sex was included as a covariate in all multivariable models presented in Table 3. As expected, male patients showed higher adjusted median values for most linear craniofacial measurements. Importantly, the cohort-associated contrasts remained after adjustment for sex, indicating that the observed differences across birth cohorts were not explained by sex composition.

To clarify and emphasize this point, we added a sentence in the Results section describing the effect of sex and noting that future studies could further explore these patterns through sex-stratified analyses.

The added paragraph is highlighted in green in the Discussion section.

"An additional pattern observed across the multivariable models concerns the effect of sex. Male patients consistently presented higher adjusted median values for most linear craniofacial measurements compared with females. Importantly, the cohort-associated contrasts persisted after adjustment for sex, indicating that the observed differences across birth cohorts were not explained by sex composition. Future research may further explore whether these cohort-associated patterns vary when analyses are stratified by sex."

We hope this response has clarified the concern regarding the reduced possibility of sex-related bias and also opens the opportunity to further consider the reviewer’s valid question about the need to explore whether sex-stratified differences may exist.

 

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors 

I appreciate your comments and your changes from the previous version

But there are some things that need improvement:

• You said that the < 1980 birth cohort group is the control group. This should be mentioned in the Material and Methods section
• Figure 3 still doesn't match with the study groups ;there are other groups mentioned in the graphic representation
• Be sure that you place the Figure number below the figure
• please check the paragraph between 286-296 rows . It is not clear if you refer to Figure 1 or Figure 2...
• Establish a single way of writing : Fig. or Figure
• I suggest to use "gender" instead of "sex"
• There is something in the article that I downloaded : 
• https://chatgpt.com/g/g-p- 85
  68221b2e0210819187b6ed328387426b-redaccion-de-articulos-proceso/project

Author Response

Dear Reviewer,

We sincerely thank you for your careful reading of the manuscript and for your precise observations. Your comments were very helpful because they allowed us to identify several issues that were generating confusion in the presentation of the results. These issues have now been fully corrected in the revised manuscript. The modifications made in response to your comments are highlighted in yellow in the text, except for those elements that were removed.

Question 1
You said that the <1980 birth cohort group is the control group. This should be mentioned in the Material and Methods section.

Response 1
Thank you for this helpful suggestion. We agree that this information should be stated more clearly in the Materials and Methods section. We have now explicitly indicated in the subsection describing the birth cohort groups that the <1980 cohort served as the reference category in the multivariable regression models.

 

Question 2
Figure 3 still doesn't match with the study groups; there are other groups mentioned in the graphic representation.

Response 2
Thank you for pointing out this inconsistency. We have corrected Figures 2 and 3 so that the graphical groups correspond exactly to the cohort groups used in the analysis (<1980, 1980–1989, and 1990–1999). In Figure 2, the <1980 cohort is not displayed because it serves as the reference (control) group in the regression models, and the figure illustrates the contrasts relative to that reference category. We apologize for the confusion and hope that these corrections resolve the issue.

 

Question 3
Be sure that you place the Figure number below the figure.

Response 3
Thank you for this observation. We have verified the placement of all figures and ensured that the figure numbers and captions appear below each figure according to the journal’s formatting guidelines.

 

Question 4
Please check the paragraph between rows 286–296. It is not clear whether you refer to Figure 1 or Figure 2.

Response 4
We appreciate this careful observation. The paragraph has been revised to ensure that the figure reference is consistent and clearly refers to Figure 2 throughout the text.

 

Question 5
Establish a single way of writing: Fig. or Figure.

Response 5
Thank you for this suggestion. We have standardized the manuscript to consistently use “Figure” throughout the text.

 

Question 6
I suggest using “gender” instead of “sex”.

Response 6
We appreciate this suggestion. In the present study, the variable corresponds to the biological classification of participants as male or female obtained from clinical records. For this reason, we retained the term “sex”, which is commonly recommended in biomedical research when referring to biological attributes rather than social or identity-related constructs.

 

Question 7
There is something in the article that I downloaded: (link)

Response 7
Thank you for identifying this issue. The link corresponded to an unintended editing artifact and has been removed from the revised manuscript. The reference was related to the use Acknowledgmentsof ChatGPT for language verification during the manuscript preparation process, as declared in the  section. We apologize for this oversight and appreciate the reviewer bringing it to our attention.

 

We would like to thank you again for your valuable observations, which hlped us improve the clarity and presentation of the manuscript. If any of the corrections have not fully addressed your concerns, we remain attentive to your further comments so that we may continue improving the article.

 

Kind regards.

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors,

I appreciate that you respected the recommendations given in the previous reviews and your paper fulfills now, in my opinion, the requirements for a research article. The Materials and Methods section and the Results section have been corrected, the figures are now well presented and described