A Spectrophotometry Evaluation of Clear Aligners Transparency: Comparison of 3D-Printers and Thermoforming Disks in Different Combinations

Round 1

Reviewer 1 Report

this manuscript can be improve in term of:

1. intro - line 62- may need to rephase the sentences as souns not in scintific writing.

2. SEM- should write full: material and method

line 135,137- noted spelling errors

3.result- p value should be presented with the number/value for the Table 1.

4. discussion; line 135-137. require rephasing of the sentence to appropirate as a sciencetific article.

5. references- new references should be included because some references found too outdated in 1987. a recent references require 

Author Response

Thank you for all comments.

• intro - line 62- may need to rephrase the sentences as sound not in scientific writing.

We have rephrased it : Thanks to the evolution of digital technology, new methods of 3d printing have been developed

• SEM- should write full: material and method

We have written it.

• line 135,137- noted spelling errors

We have corrected them thank you.

• result- p value should be presented with the number/value for the Table 1.

We have modified it, thank you.

• discussion; line 135-137. require rephrasing of the sentence to appropriate as a scientific article.

We have rephrased it thank you.

• references- new references should be included because some references found too outdated in 1987. a recent references require 

We have modified them

Reviewer 2 Report

- First of all, congratulations to the authors for their efforts in carrying out this research. However, the following points should be answered:

- In the text, there are several layout and editing errors that should be corrected.

- In the introduction in line 96 it talks about an article published in 2015, however at the end of the sentence the reference does not appear in line 102. In the following article that cites 2020 at the end of the text it cites two articles 18 and 19, published in 2015 and 2022, correct the error and revise throughout the text.

- In the introduction you should refer to the ranges that are perceptible by human eye. If the importance of the study is to assess the transparency of an aligner to have greater aesthetics in orthodontic treatment, it is important to know at which nm ranges it can be perceptible by the human being and which are not. 

- In the statistical analysis section it speaks of p 0.05, however in Table 1, it refers to p 0.01. Check it.

- In the results in line 199 to 202, it says that the Zendura material does not have statistically significant differences with p 0.05. What do you think was the reason, you think the material has a number of variables that are independent of the type of 3d printer.

- In the discussion, the sentence 287 and 288 is repeated in material and methods, look for meaning or introduce explanatory text of it, if not omit it.

- In lines 289 and 292 talk about studies but do not cite which ones.

- During the 14 days that the aligners were degraded, at no time were they removed for cleaning. In real conditions, patients usually clean the aligners with different methods. This may condition the interpretation of the results. Depending on the protocol used, a lower transparency from t0 to t1 is a normal result because the aligner has undergone a degradation process. Is it really perceptible by human beings the translucency change ranges exposed in the present study?

In my opinion, the above point should be discussed in depth in the discussion section since the degree of translucency of the aligner may depend on the patient's tooth shade that transmits the reflected light to the aligner under in vivo conditions.

Author Response

Thank you for the comments.

• In the text, there are several layout and editing errors that should be corrected.

Thank you, we have corrected them.

• In the introduction in line 96 it talks about an article published in 2015, however at the end of the sentence the reference does not appear in line 102. In the following article that cites 2020 at the end of the text it cites two articles 18 and 19, published in 2015 and 2022, correct the error and revise throughout the text.

Thank you, we have revised the sentence.

• In the introduction you should refer to the ranges that are perceptible by human eye. If the importance of the study is to assess the transparency of an aligner to have greater aesthetics in orthodontic treatment, it is important to know at which nm ranges it can be perceptible by the human being and which are not. 

We thank the reviewer for this important suggestion, however it is not possible to correlate the level of transparency of a material in univocal manner or standardized way with the subjective human optical perception. Electromagnetic radiation in the range of visible light has wavelengths from 400 to 700 nm, but the human eye evaluates the intensity corresponding to the various wavelength to different extents. In fact, the higher wavelengths (near 700 nm) are poorly absorbed by the visual pigments; the lower wavelengths (near 400 nm) can be absorbed by the visual pigments of the eye, but do not reach the retina because they are absorbed by the cornea and lens. The peak of the highest human spectral sensitivity measured is at about 560 nm, the yellow-green color region. We have measured by a spectophotometer the transparency of the materials, for each wavelength in the 400-700 nm range, with the transmittance quantity, (as %T) the fraction of incident light that passes through the material and we have considered the %T variation before and after in vitro ageing. Instead the perception in vivo of different degrees of transparence is subjective to the human eye for each individual.

• In the statistical analysis section it speaks of p 0.05, however in Table 1, it refers to p 0.01. Check it.

We have corrected it. Thank you.

• In the results in line 199 to 202, it says that the Zendura material does not have statistically significant differences with p 0.05. What do you think was the reason, you think the material has a number of variables that are independent of the type of 3d printer.

Yes, it means that the material itself has good color stability over time.

• In the discussion, the sentence 287 and 288 is repeated in material and methods, look for meaning or introduce explanatory text of it, if not omit it.

I have omitted it because it was a repetition. Thank you

• In lines 289 and 292 talk about studies but do not cite which ones.

Citation number 18 and 19.

• During the 14 days that the aligners were degraded, at no time were they removed for cleaning. In real conditions, patients usually clean the aligners with different methods. This may condition the interpretation of the results. Depending on the protocol used, a lower transparency from t0 to t1 is a normal result because the aligner has undergone a degradation process. Is it really perceptible by human beings the translucency change ranges exposed in the present study?

In our study, in vitro aging was considered. Transmittance (T%) is an objective value, which is why it was considered. Other studies may in the future be based on the subjective perception of aging, but our purpose was to evaluate the change in properties based on a variable that was as objective as possible. However, the choice of conducting an in vitro study is correlated to the need of standardizing the aging process in artificial saliva, ensuring that the transparency level wouldn’t be affected by individual habits, but only by the intrinsic optical properties of the aligner.

In my opinion, the above point should be discussed in depth in the discussion section since the degree of translucency of the aligner may depend on the patient's tooth shade that transmits the reflected light to the aligner under in vivo conditions.