In Vivo Optical Coherence Tomography for Diagnostic Characterization of Enamel Defects in Molar Incisor Hypomineralization: A Case-Control Study

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The scientific paper makes a mixed impression. On the one hand, the authors have done a good job of collecting and analyzing a significant sample of structural images (B-scans) of optical coherence tomography. The importance of the study and the methodology used (comparative studying 50 healthy and 50 diseased children's teeth in vivo) are worthy of respect. On the other hand, this is not exactly photonics in its style of presentation. Moreover, the authors' assumptions about the physical causes of changes in the optical signal for some regions of interest are not entirely correct.

In general, the reviewer (as a specialist in the field of biomedical engineering and biophotonics) liked the study, since it shows the importance and necessity of developing the subject area. It is advisable to remove obvious inaccuracies and to supplement the paper with valuable materials on the most important nuances of the optical coherence tomography systems clinical usage. These nuances should ideally be related to scanning sectors, focusing, stabilization, positioning accuracy, etc. The above mentioned features may not be obvious at all to specialists in the field of optical coherence tomography, but are understandable to medical workers and are needed in real clinical practice. Therefore, they are especially interesting.

Key inaccuracies:

I) The authors report that «These techniques exploit light–tissue interactions to identify mineral loss or changes in tissue density, providing non-invasive alternatives to conventional methods. However, their diagnostic performance can be affected by staining, restorations, and operator variability» in relation to a whole range of optical medical imaging methods, including «near-infrared imaging (NIR)». However, optical coherence tomography is a variant of near-infrared imaging. The central wavelength of 1305 nm indicated by the authors in paragraph 2.3 refers to the second therapeutic window of transparency of biological tissues (NIR II: 1000–1350 nm) to be more precise.

II) The authors report that «By leveraging optical contrast mechanisms intrinsic to photonic imaging, this study seeks to enhance diagnostic precision and support preventive decision-making in the management of MIH-affected children», most likely referring to the strong difference in optical properties between enamel and dentin (roughly speaking, the penetration depth of radiation with a central wavelength of 1305 nm in enamel is about 12 times higher than in dentin all other things being equal). However, this term is used to denote immersion clearing agents and other exogenous substances to improve individual quality characteristics of the resulting images in the context of photonics. The authors of the paper apparently did not use exogenous contrast agents.

III) The authors of the research consider the swept-source modification of systems for optical coherence tomography in a very one-sided way. In reality, such systems are characterized by a combination of a fairly high data acquisition rate and a fairly high scanning depth. In addition, an increase in the raw data acquisition rate reduces the number of motion artifacts. However, the resolution of the resulting images is lower than that in spectral domain optical coherence tomography, and tissue contrast is also lower. Dermatology is most often the beneficiary of swept-source based systems compromise (by the way the device that the authors used was developed mainly for dermatological needs).

IV) The authors of the paper repeatedly report uniform attenuation of the optical signal in the anatomical structures of a healthy tooth. However, optical coherence tomography is characterized by such a large dynamic range (over 40 Decibels) that structural images are displayed on a logarithmic scale. Signal degradation in depth is immanent for optical coherence tomography from the point of view of the physics of strongly scattering media.

V) The authors link the growth of mechanical properties and reflectivity, which is not entirely correct. For example, implanted objects are often studied using optical coherence tomography. A material of coronary stent is much harder (by the value of Young's modulus, by the value of the shear modulus and many other biomechanical characteristics) than a blood vessel wall, but almost always appears as a set of dark stripes on a circular intravascular optical coherence tomography B-scan. Useful information about the optical structure of an object under study using optical coherence tomography is provided not only by back-reflected photons, but also by back-scattered and even low-scattered ones (with trajectories in several interaction acts and here absorption is important). It is also customary to mention its anisotropy in relation to scattering.

To summarize the above, the scientific article is recommended for publication after significant revision.

Author Response

Response to Reviewer 1

We sincerely thank Reviewer 1 for the constructive and insightful comments that have greatly helped us improve the manuscript. Below are our point-by-point responses to each comment, with the corresponding revisions highlighted in the revised manuscript.

General Comment

“The scientific paper makes a mixed impression. On the one hand, the authors have done a good job of collecting and analyzing a significant sample of structural images (B-scans) of optical coherence tomography. The importance of the study and the methodology used (comparative studying 50 healthy and 50 diseased children's teeth in vivo) are worthy of respect. On the other hand, this is not exactly photonics in its style of presentation. Moreover, the authors' assumptions about the physical causes of changes in the optical signal for some regions of interest are not entirely correct. In general, the reviewer (as a specialist in the field of biomedical engineering and biophotonics) liked the study since it shows the importance and necessity of developing the subject area. It is advisable to remove obvious inaccuracies and to supplement the paper with valuable materials on the most important nuances of the optical coherence tomography systems clinical usage. These nuances should ideally be related to scanning sectors, focusing, stabilization, positioning accuracy, etc. The above-mentioned features may not be obvious at all to specialists in the field of optical coherence tomography, but are understandable to medical workers and are needed in real clinical practice. Therefore, they are especially interesting.”

Response

We sincerely thank the reviewer for the overall positive assessment of our study and for the valuable suggestions on how to improve its technical rigor and clarity. In response, we have carefully reviewed and corrected all potentially inaccurate statements regarding the physical origins of OCT signals, as detailed in our responses to specific comments (I–V). We have clarified that OCT contrast is governed by complex light–tissue interactions rather than mechanical properties per se. We also revised the manuscript to provide a more balanced and technically accurate description of the swept-source OCT system used. These additions, as recommended by the reviewer, are now explicitly described to enhance the clinical and practical relevance of the paper while aligning it more closely with the expectations of the photonics field.

Comment I

“The authors report that «These techniques exploit light– tissue interactions to identify mineral loss or changes in tissue density, providing non-invasive alternatives to conventional methods. However, their diagnostic performance can be affected by staining, restorations, and operator variability» in relation to a whole range of optical medical imaging methods, including «near-infrared imaging (NIR)». However, optical coherence tomography is a variant of near-infrared imaging. The central wavelength of 1305 nm indicated by the authors in paragraph 2.3 refers to the second therapeutic window of transparency of biological tissues (NIR II: 1000–1350 nm) to be more precise.”

Response I

We thank the reviewer for this valuable clarification. Indeed, OCT is a specific modality within the near-infrared (NIR) imaging spectrum, as it employs low-coherence light in the NIR range for cross-sectional imaging. We have revised the Introduction to explicitly acknowledge that OCT is a subset of NIR-based imaging techniques. Furthermore, we have specified in Section 2.3 that the 1305 nm wavelength used in our study falls within the NIR-II therapeutic window (1000–1350 nm), which enhances tissue transparency and penetration depth.

Comment II

“The authors report that «By leveraging optical contrast mechanisms intrinsic to photonic imaging, this study seeks to enhance diagnostic precision and support preventive decision-making in the management of MIH-affected children», most likely referring to the strong difference in optical properties between enamel and dentin (roughly speaking, the penetration depth of radiation with a central wavelength of 1305 nm in enamel is about 12 times higher than in dentin all other things being equal). However, this term is used to denote immersion clearing agents and other exogenous substances to improve individual quality characteristics of the resulting images in the context of photonics. The authors of the paper apparently did not use exogenous contrast agent.”

Response II

We appreciate the reviewer’s observation. As you pointed out, in our manuscript, the term “optical contrast mechanisms” refers to the intrinsic optical differences between enamel and dentin—such as the greater light penetration and lower scattering in enamel compared to dentin—which generate the grayscale contrast observed in OCT images. No exogenous contrast agents were used in this study. To avoid any misunderstanding, we have revised the sentence accordingly.

Comment III

“The authors of the research consider the swept-source modification of systems for optical coherence tomography in a very one-sided way. In reality, such systems are characterized by a combination of a fairly high data acquisition rate and a fairly high scanning depth. In addition, an increase in the raw data acquisition rate reduces the number of motion artifacts. However, the resolution of the resulting images is lower than that in spectral domain optical coherence tomography, and tissue contrast is also lower. Dermatology is most often the beneficiary of swept-source based systems compromise (by the way the device that the authors used was developed mainly for dermatological needs).”

Response III

We thank the reviewer for this constructive comment. We agree that swept-source OCT (SS-OCT) systems represent a trade-off: they offer greater imaging depth and faster acquisition rates—reducing motion artifacts—while generally providing lower axial resolution and tissue contrast compared to spectral-domain OCT (SD-OCT). We have revised the Introduction to present this balanced perspective. Furthermore, in Section 2.3 (Methods) we have clarified that, although the VivoSight® system was originally developed for dermatological imaging, its acquisition speed and imaging depth make it suitable for in vivo dental applications. Finally, in the Discussion (Limitations), we have added a note highlighting this adaptation as a limitation of the study.

Comment IV

“The authors of the paper repeatedly report uniform attenuation of the optical signal in the anatomical structures of a healthy tooth. However, optical coherence tomography is characterized by such a large dynamic range (over 40 Decibels) that structural images are displayed on a logarithmic scale. Signal degradation in depth is immanent for optical coherence tomography from the point of view of the physics of strongly scattering media.”

Response IV

We thank the reviewer for this technical clarification. We are aware that OCT images inherently exhibit depth-related signal attenuation, which leads to reduced intensity in the deepest layers of the image due to scattering in strongly diffusive media. However, our reference to “uniform attenuation” was not meant to describe this physical phenomenon. Rather, we intended to highlight that, within the enamel and dentin regions visible in the OCT scan (i.e., the superficial and clinically relevant layers), the signal profile appears homogeneous and free of localized scattering anomalies, which is indicative of structurally sound dental tissues. To avoid any confusion, we have revised the text to clarify this point.

Comment V

“The authors link the growth of mechanical properties and reflectivity, which is not entirely correct. For example, implanted objects are often studied using optical coherence tomography. A material of coronary stent is much harder (by the value of Young's modulus, by the value of the shear modulus and many other biomechanical characteristics) than a blood vessel wall, but almost always appears as a set of dark stripes on a circular intravascular optical coherence tomography B-scan. Useful information about the optical structure of an object under study using optical coherence tomography is provided not only by back- reflected photons, but also by back-scattered and even low-scattered ones (with trajectories in several interaction acts and here absorption is important). It is also customary to mention its anisotropy in relation to scattering.”

Response V

We thank the reviewer for this important clarification. We agree that OCT reflectivity is not directly determined by mechanical properties such as hardness or Young’s modulus, but rather by optical interactions, including back-reflection, back-scattering, low-scattering photon trajectories, absorption, and scattering anisotropy. Our statement was intended to emphasize that hypomineralized enamel exhibits both reduced mechanical strength and increased OCT backscattering due to the same underlying microstructural alterations—such as prism disorganization, porosity, and changes in mineral content—rather than suggesting a direct causal link between mechanical properties and OCT signal. We have revised the text to clarify that OCT contrast arises from complex light–tissue interactions, where anisotropy of scattering also plays a role.

Reviewer 2 Report

Comments and Suggestions for Authors

Buttacavoli et al. used in vivo optical coherence tomography to study Molar Incisor Hypomineralization by identifying structural characteristics between healthy and affected teeth.

1. Power analysis is missing with 50 samples in each group. It's important for diagnostic accuracy studies.
2. Potential selection bias: All participants were recruited from a single center. Also, the authors have excluded severe MIH, it would be better to categorize into mild and severe groups.
3. The qualitative OCT analysis relies on the interpretation done by the examiner, but not a objective quantitative methods
4. Radiographic analysis is missing.
5. Background information, such as dietary/family history/fluoride, should be included.
6. Overstatement about the potential of the OCT technique, we need direct comparative statistics between the conventional one (such as radiography) and OCT 

Author Response

Response to Reviewer 2

We sincerely thank Reviewer 2 for the constructive comments and suggestions that helped us improve the manuscript. We address each point below, with corresponding revisions highlighted in the updated version of the manuscript.

Comment 1

“Power analysis is missing with 50 samples in each group. It's important for diagnostic accuracy studies.”

Response 1

We thank the reviewer for this observation. This study was intentionally designed as the first in vivo, qualitative OCT characterization of MIH enamel, focusing on structural imaging rather than statistical measures of diagnostic accuracy. Therefore, a formal power analysis—typically required for hypothesis-driven diagnostic studies—was not applicable to the exploratory and pilot objectives of our work. The inclusion of 50 teeth per group ensured a robust qualitative comparison and sufficient variability to describe OCT patterns in vivo. We have clarified throughout the manuscript that this study is exploratory and descriptive in nature, while also noting that future large-scale investigations will require formal statistical frameworks and power analyses to validate and expand these preliminary findings.

Comment 2

“Potential selection bias: All participants were recruited from a single center. Also, the authors have excluded severe MIH, it would be better to categorize into mild and severe groups.”

Response 2

We thank the reviewer for this important observation. All participants were recruited from a single center to ensure standardized diagnostic procedures, uniform clinical settings, and consistent OCT imaging conditions, which is a common approach for exploratory pilot studies. Severe MIH lesions were intentionally excluded because post-eruptive breakdown and extensive surface irregularities often produce scattering artifacts that compromise the reliability of OCT-based structural interpretation. Focusing on mild MIH lesions is, in fact, a strength of this study, as these early-stage defects are the most challenging to detect with conventional diagnostic tools and best highlight the sensitivity of OCT in visualizing subtle enamel alterations. We have clarified this rationale in the Methods and Limitations sections.

Comment 3

 “The qualitative OCT analysis relies on the interpretation done by the examiner, but not a objective quantitative methods”

Response 3

We thank the reviewer for this comment. Our study was designed to provide a qualitative structural characterization of MIH using OCT, focusing on the identification of reproducible morphological patterns rather than quantitative metrics. We acknowledge that the qualitative interpretation of OCT scans, while informative, may be operator-dependent. We have clarified this limitation in the Discussion, highlighting the need for future research to incorporate quantitative OCT parameters (such as attenuation coefficients or depth-resolved reflectivity profiles) and automated image analysis to improve objectivity and reproducibility. Furthermore, future phases of our research will aim to assess diagnostic performance and accuracy metrics based on these qualitative OCT features, once validated against larger datasets.

Comment 4

“Radiographic analysis is missing”

Response 4

We thank the reviewer for this observation. Radiographic imaging was intentionally excluded because our study aimed to evaluate a radiation-free, non-invasive diagnostic tool particularly suited for pediatric patients. Conventional radiographs, as confirmed by Al-Azri et al. (2016, J. Biomed. Opt.), have limited sensitivity for detecting early or subsurface enamel alterations due to their 2D projection, low resolution, and surface superimposition, and they cannot accurately determine the depth or microstructural changes of MIH lesions. Even when combined with a thorough clinical inspection, intraoral radiographs and bitewings provide only a single two-dimensional view of an enamel defect that is inherently three-dimensional, which limits the evaluation of its true extension and structural complexity. Shimada et al. (2010, J. Biomed. Opt.) also highlighted the reduced diagnostic performance of bitewing radiographs compared to OCT. In contrast, OCT provides high-resolution cross-sectional imaging (5–10 μm) and can reveal subsurface structural features that radiographs cannot. Balhaddad et al. (2021, Dent. Mater.) and Espigares et al. (2020, Sci. Rep.) further confirmed that OCT achieves superior sensitivity and specificity compared to radiography for early enamel changes. Therefore, including radiographs would not have added diagnostic value for the early-stage lesions investigated here and would have required unnecessary ionizing exposure in children. We have clarified this rationale in the Discussion and noted that future studies may benefit from direct OCT vs radiographic comparisons to evaluate complementary roles, particularly in severe or ambiguous MIH cases.

Comment 5

“Background information, such as dietary/family history/fluoride, should be included.”

Response 5

We sincerely thank the reviewer for pointing out this important aspect. We agree that background factors such as dietary habits, family history, and fluoride exposure are clinically relevant for MIH. While our study was not designed to investigate etiological factors, we acknowledge that the exclusion of children with systemic fluoride supplementation or clinical signs of fluorosis was part of our clinical selection process, although this was not clearly stated in the original manuscript. We have now explicitly added this exclusion criterion in the Methods section to clarify the study design.

Comment 6

“Overstatement about the potential of the OCT technique, we need direct comparative statistics between the conventional one (such as radiography) and OCT”

 

Response 6

We thank the reviewer for this comment. Our discussion emphasizes the qualitative advantages of OCT—high-resolution, cross-sectional, and radiation-free imaging—supported by both our findings and existing literature, without making claims about diagnostic superiority over radiography or other modalities. Direct comparative statistics with conventional methods were not within the scope of this exploratory study, which aimed to characterize the structural patterns of MIH using OCT. We hope that, having clarified these aspects, the reviewer agrees that our statements regarding OCT’s potential are consistent with the evidence presented and appropriately contextualized within current scientific knowledge.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors took the reviewer's comments very seriously. All inaccuracies pointed out by the reviewer were corrected, the current version of the scientific paper is balanced from the physical, technical and medical points of view. It is perfectly suitable for the scientific journal «Photonics» and is recommended for publication in the nearest issue.

The reviewer wishes the authors success in their further research and new high-ranking scientific publications.

Reviewer 2 Report

Comments and Suggestions for Authors

N/A