Clinical Comparative Study for Validation of Digital Impression Reliability with the Gypsum Check: A Simple and Fast Way to Evaluate the Trueness and Accuracy of Implant-Supported Rehabilitation

Round 1

Reviewer 1 Report

First of all, congratulations on the idea. It is important for dentists to know whether they can trust the digital impression method or not, and it is urgent to find a way to control this situation to avoid failures in the work they perform in their clinics. However, there are some points I would like to share with you that I believe can enhance this idea, which has its merits.

Firstly, in the course of your methodology, it is not clearly understood where the first digital impression is taken and where the second one is taken. This is not well defined in the methodology. From what I understand, there is a conventional impression made with type IV plaster, which is scanned (first digital impression), and then an impression is made of the patient's implants with another scanner. Is that correct? This issue is not well structured and becomes confusing and poorly delineated.

Another aspect that seems relevant to me is the lack of standardization of the method regarding the initial positioning of the implants. The variability between patients may introduce bias into the results and lead to misinterpretation. A good example of this can be seen in the middle image at the end of the article, where a non-parallel positioning of the implants is observed (with a slight inclination), which from a clinical point of view may not be relevant, but from a research perspective in the context of publishing a scientific article, may not be entirely correct. The failure of the plaster that splints the UCLA's may be due to poor distribution of the force applied to the studied structures. In the example of the middle image, what may happen is that a more facilitated positioning on one pillar causes the tightening of the following one to fracture the plaster structure, even though nothing is wrong... simply, one part has to yield and ends up yielding, even if it's not a problem.

Another reason that I think you should take into consideration in your work, but are not visualizing, is the behavior of the materials themselves. Both the UCLA and the implant itself have elastic properties that can greatly influence the results you are presenting, as well as the plaster pouring or the use of Duralay. I believe that there are many factors that can cause problems in your work, which should have been taken into account for a better interpretation of the results and for drawing conclusions.

Author Response

Authors want to thank very much the reviewer 1 for their comments. We are sure that addressing to your suggestions improve the quality of this paper. Here are the point-by-point answers to your comments.

 

Firstly, in the course of your methodology, it is not clearly understood where the first digital impression is taken and where the second one is taken. This is not well defined in the methodology. From what I understand, there is a conventional impression made with type IV plaster, which is scanned (first digital impression), and then an impression is made of the patient's implants with another scanner. Is that correct? This issue is not well structured and becomes confusing and poorly delineated.

 

Thank you for this consideration. The workflow of the study is explained in lines 111-135 and consist in one conventional impression with polyether (Impregum) and two digital impressions with intraoral scanner. The workflow of the digital impression was fully digital, with the generation of STL file directly after the digital impression. The workflow of conventional impression consisting of a development of plaster cast after polyether impression and their digitalization with 3Shape D500 laboratory scanner which allows to create STL file useful to compare with the STL files of the two digital impressions.

 

Another aspect that seems relevant to me is the lack of standardization of the method regarding the initial positioning of the implants. The variability between patients may introduce bias into the results and lead to misinterpretation. A good example of this can be seen in the middle image at the end of the article, where a non-parallel positioning of the implants is observed (with a slight inclination), which from a clinical point of view may not be relevant, but from a research perspective in the context of publishing a scientific article, may not be entirely correct. The failure of the plaster that splints the UCLA's may be due to poor distribution of the force applied to the studied structures. In the example of the middle image, what may happen is that a more facilitated positioning on one pillar causes the tightening of the following one to fracture the plaster structure, even though nothing is wrong... simply, one part has to yield and ends up yielding, even if it's not a problem.

 

Thank you to sharing these aspects with us because result from a very accurate analysis of our study. Authors included in this study the degree of mutual inclination of implants which is allowed by prosthetic components of manufacturers instructions of Neoss implants. Moreover, the illustrated cases are exclusively referred to the validation of digital impression with gypsum check. They are respectively from patients 1, 6 and 9: the last two (6 and 9) although showed fracture of both digital impressions, but no fracture of conventional impression, leading to a passive fit of future rehabilitation (which is the last purpose of prosthetic framework on implants). Implants that exceeded the maximum inclination allowed by manufacturers were not included in this study and were rehabilitated with angulated abutments. However, all these important clarifications have been added in the main text, thank you.

 

Another reason that I think you should take into consideration in your work, but are not visualizing, is the behavior of the materials themselves. Both the UCLA and the implant itself have elastic properties that can greatly influence the results you are presenting, as well as the plaster pouring or the use of Duralay. I believe that there are many factors that can cause problems in your work, which should have been taken into account for a better interpretation of the results and for drawing conclusions.

 

Thank you for this comment: it is another aspect that should be better explained. Authors preferred to use gypsum instead of duralay for their different Young modulus of elasticity. The Young modulus of the gypsum is usually between 1 and 2 GPa, while the Young modulus of the Duralay (PMMA) is between 3 and 5 GPa. This feature of these two different materials reflects undoubtedly on their elasticity and their ability to forfeit energy during their deformation. The gypsum which is less elastic than the Duralay allows less deformations, so it fractures much earlier than the Duralay when subjected to deformation. Considering these aspects, we used a method that permit less deformation leading to a more reliable check of passive fit of future framework. After these considerations, we could conclude that the elastic properties of UCLA, implant, plaster and Duralay are included in a range of tolerance which allows the passive fit, established by the outcomes of gypsum check, providing to the clinician a fast method to check the impression reliability. All these issues have been added in the main text and the authors want to thank you to suggest us with this comment to improve our work, making it completer and more understandable.

Reviewer 2 Report

The manuscript submitted by Giuseppe Barile et al reported on the “Clinical comparative study for validation of digital impression 2 reliability with the Gypsum Check: a simple and fast way to 3 evaluate the Trueness and Accuracy of implant-supported rehabilitation.” In this work, the authors purposed a new evaluation of 20 digital impression Accuracy and Trueness with a simple check. Trueness, Precision, and Accuracy were considered or measured to analyze this new method. The paper looks good and detailed experiments were listed. I think minor modification is needed before publication.   

In graph 1, there is no description of X/Y axis. Please add that information. 

In section 6. It is super helpful to give clinical cases, but is it possible to discuss them or show the data in results/discussion section? Put them after the conclusion looks delayed. 

Overall, I believe the manuscript and the topic are in an interesting area. I suggest minor revision before publication.

Author Response

The manuscript submitted by Giuseppe Barile et al reported on the “Clinical comparative study for validation of digital impression 2 reliability with the Gypsum Check: a simple and fast way to 3 evaluate the Trueness and Accuracy of implant-supported rehabilitation.” In this work, the authors purposed a new evaluation of 20 digital impression Accuracy and Trueness with a simple check. Trueness, Precision, and Accuracy were considered or measured to analyze this new method. The paper looks good and detailed experiments were listed. I think minor modification is needed before publication.  

In graph 1, there is no description of X/Y axis. Please add that information.

In section 6. It is super helpful to give clinical cases, but is it possible to discuss them or show the data in results/discussion section? Put them after the conclusion looks delayed.

Overall, I believe the manuscript and the topic are in an interesting area. I suggest minor revision before publication.

 

Thank you very much for your gentle words about our paper.

Graph n.1 has been provided with axes titles, as your suggestion and clinical cases were moved in material and methods section.

Thank you again for suggesting us these corrections and we express our pleasure because our work was to your liking.

Reviewer 3 Report

The study seems interesting, however the authors should address the following points to improve the quality of the manuscript:

- The abstract should state the current gap in literature. Also, check the word limit since the abstract seems long. 

- The objectives of the study is not clear. Please clarify the objectives of the study and add the research hypotheses in the introduction section.

- Line 110 and others: Please use the specialty terms published in the latest edition of GPT for clarity. (https://www.academyofprosthodontics.org/lib_ap_articles_download/GPT9.pdf)

- Please cite the available literature related to accuracy measurement methodologies (trueness, precision and error measurements).

- Please provide citation for the 100 microns cutoff limit.

- Tables and figures are well-presented.

- Please split the discussion section into multiple paragraphs. Make sure that study limitations and recommendations for future research are added clearly. 

- Conclusions can be listed as bullet points.

- Clinical cases should be added to the materials and methods sections to maintain the proper flow of the manuscript. 

Author Response

Thank you very much for the appreciating words you expressed about our work and thank you for the constructive suggesting you made to improve the quality of this paper.

Here are point-by-point answers to your comments.

 

- The abstract should state the current gap in literature. Also, check the word limit since the abstract seems long.

 

You’re were right, abstract was too long and now has been corrected having less than 200 words, thank you.

 

- The objectives of the study is not clear. Please clarify the objectives of the study and add the research hypotheses in the introduction section.

 

The objectives of this study were corrected and split in two different points to improve the readability. Research hypothesis was added. Thank you.

 

- Line 110 and others: Please use the specialty terms published in the latest edition of GPT for clarity. (https://www.academyofprosthodontics.org/lib_ap_articles_download/GPT9.pdf)

 

Thank you for this suggestion. Considering the latest edition of GPT of Academy of Prosthodontics following terms were substituted: Individual tray in “custom tray”, healing abutment in “healing screw”, impression transfer in “impression transfer coping”, model in “cast”.

 

- Please cite the available literature related to accuracy measurement methodologies (trueness, precision and error measurements).

 

The trueness, precision and error measurement are well defined by ISO rules, cited in the relative paragraph. To resume the available literature which is very abundant of studies we cited a systematic review of JPD which address this topic. Thank you.

 

- Please provide citation for the 100 microns cutoff limit.

 

Citation was provided in line 230, thank you.

 

- Tables and figures are well-presented.

 

- Please split the discussion section into multiple paragraphs. Make sure that study limitations and recommendations for future research are added clearly.

 

The discussion was split in different sections resulting in an improved impact on readability, thank you for such suggestion.

 

- Conclusions can be listed as bullet points.

 

Conclusion was listed as bullet points, thank you.

 

- Clinical cases should be added to the materials and methods sections to maintain the proper flow of the manuscript.

 

Clinical cases were moved to material and methods section, as you rightly suggested.

 

Authors want to thank the reviewer very much because his suggestion has greatly improved this manuscript.

Round 2

Reviewer 1 Report

Thank you for the clarifications and changes made to the manuscript.