Properties of Zirconia, Lithium Disilicate Glass Ceramics, and VITA ENAMIC^® Hybrid Ceramic Dental Materials Following Ultra-Short Femtosecond (30 fs) Laser Irradiation

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The aim of this study is to evaluate the effect of laser on 3 different dental ceramic materials using SEM and EDS techniques. No methodological errors were found in this article. Weak areas in the manuscript should be highlighted further. The subject of this study is a current issue and may attract the attention of the reader. However, the following minor corrections need to be made:

 

Abstract: Although this section is well written in terms of its general structure, the conclusion section should be more detailed in relation to the results.

Introduction: Well written.

Materials and methods: Was an ISO standard followed during the preparation of the samples under the heading "Preparation of ceramic samples"? If so, please specify. How were the dimensions of the samples calibrated? Please specify clearly.

Results: The increase in the amount of carbon in zirconium samples with the use of laser is an interesting data. However, it is stated in the following sections that the use of laser does not change the tetragonal structure of zirconium. More attention can be drawn to this data.

Discussion: Provide information about the limitations of the study.

References: References 4, 5, 11, 20, 21, 23, 32 and 39 are too old. Please replace with new ones if possible.

Comments on the Quality of English Language

There are no major errors in language in this text.

Author Response

Recommendations from the Reviewer #1 (Comments 1 – 4; noted as R#1.1 – R#1.4)

R#1.1: Was an ISO standard followed during the preparation of the samples under the heading "Preparation of ceramic samples"? If so, please specify. How were the dimensions of the samples calibrated? Please specify clearly.

Response: The following statement has been added to page 5 in the revised R1 version of the MS “The samples were milled into flat oval plates with dimensions of 5 × 10 × 3 mm³, in accordance with and exceeding the requirements of ISO 6872:2015 (Dentistry) ‘Ceramic Materials’, which specifies the preparation and surface finish for dental ceramics such as zirconia and LD glass ceramic materials. In addition, the accuracy of CAD/CAM digitized milling and finishing of test samples complied to the ISO 12836:2015 (Dentistry) ‘Digitizing Devices for CAD/CAM Systems for Indirect Dental Restorations’ standard ” as required.

 

R#1.2: The increase in the amount of carbon in zirconium samples with the use of laser is an interesting data. However, it is stated in the following sections that the use of laser does not change the tetragonal structure of zirconium. More attention can be drawn to this data.

Response: Indeed, the increase in the amount of carbon in zirconia samples when using femtosecond (fs) laser radiation is likely due to the incorporation of carbon from the ambient environment or from laser-induced plasma onto the surface of the zirconia. However, the use of fs-laser radiation is not expected  to change the tetragonal structure of zirconia for several reasons. Firstly, the 30 fs-laser light is of an ultra-short pulse duration, which results in a very limited interaction time between the laser and the irradiated material. This fs-pulse duration means that the energy is confined to a very small irradiation volume and does not have enough time to cause significant heat diffusion into the surrounding material. As a result, there is minimal thermal effect that could induce a phase transformation from the tetragonal to monoclinic phase. Secondly, the 30-fs laser irradiation process is truly an athermal process, meaning it does not generate significant heat that could disrupt the intrinsic tetragonal crystalline structure of zirconia. Also, 30 fs-laser irrigation is of high energy density and triggers non-linear effects in the irradiated solids, such as multi-photon ionization, where the material absorbs multiple photons simultaneously. This leads to a solid retaining its intrinsic structure post fs-laser irradiation exposure. These and additional statements have been collated and supported by appropriate references in Section 4 Discussion in the revised version of the MS and presented on pages 16 - 18 as requested.

 

 

R#1.3: Provide information about the limitations of the study.

Response: Additional paragraph has been added into the Section 4 Discussions on page 19 and into the Section 5 Conclusions on page 20, addressing the limitations of the study as requested.

 

R#1.4: References 4, 5, 11, 20, 21, 23, 32 and 39 are too old. Please replace with new ones if possible.

Response: References 4 (2020), 5 (2004), 11 (2022), 20 (2023), 21 (2022), 23 (2022), 32 (2015), and 39 (2020) include publications from year 2004 (Ref 5) to year 2023 (Ref 20). Reference 5 has been removed as requested. However, Reference 32 is integral to the topical discussion presented in the text, and its removal would detract from the quality of the argument on page 4. The other references in question are up-to-date and include both contemporary and seminal works by emerging and established leaders in the field. The authors believe that removing or updating these references would compromise the overall quality of the MS. We are confident that the references supporting the revised R1 version of the MS are both adequate and sufficient.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The study about new dental ceramics is very important and has potential in clinics, but there are the following concerns that need to be addressed before publication:
1. Abstract: It is suggested to the authors to remove the headings like background, materials and methods, results, and conclusion from the abstract. Also, add one introductory line at the beginning of the abstract to present the importance of your study. 
2. Many references are so old, so authors should cite some recent literature.
3. Authors should add the percentage purity of materials.
4. The authors have provided only SEM images; it is recommended to add elemental mapping, FTIR, and XRD data.
5. The authors should add the results of the results of the biocompatibility and toxicity tests.
6. Conclusions should be rewritten in view of outcomes and future perspectives.

Author Response

Recommendations from the Reviewer #2 (Comments 1 – 6; noted as R#2.1 – R#2.6)
R#2.1: Abstract: It is suggested to the authors to remove the headings like background, materials and methods, results, and conclusion from the abstract. Also, add one introductory line at the beginning of the abstract to present the importance of your study.
Response: The Abstract has been completely revised and re-written as recommended.

R#2.2: Many references are so old, so authors should cite some recent literature. Response: Refer to the response rendered to R#1.4 earlier. Present references are integral to the topical discussion presented in the text, and their removal would detract from the quality of the arguments presented in the main body of the work. The references selected and used in the work are up- to-date and include both contemporary and seminal works by emerging and established leaders in the field. The authors believe that removing or updating these references would compromise the overall quality of the MS. We are confident that the references supporting the revised R1 version of the MS are both adequate and sufficient.

R#2.3: Authors should add the percentage purity of materials.
Response: The wt.% purity and chemical composition for materials studied has been added into Section 2.1 Sample Preparation on page 5 as requested. Additionally, three references (Ref 36 – 38) to technical release reports from the manufacturer have been added into the References section.

R#2.4: The authors have provided only SEM images; it is recommended to add elemental mapping, FTIR, and XRD data.
Response: This work represents the first pilot study to report changes in the chemical composition and morphology of zirconia, LD glass ceramics, and VITA En hybrid composite dental materials following ultra-short femtosecond (30 fs) laser irradiation. The findings are supported by comprehensive EDS and SEM analyses. While the inclusion of FTIR and XRD measurements would add additional information, these additional analytical measurements were outside the scope of the work which focussed on the influence of laser parameters.

R#2.5: The authors should add the results of the results of the biocompatibility and toxicity tests. Response: As previously addressed in response to R#2.4, these tests fall outside the original scope of the research, and would be major separate pieces of work in their own right.

R#2.6: Conclusions should be rewritten in view of outcomes and future perspectives.
Response: The Section 5 Conclusions has been fully re-written to address the outcomes of the study, its limitations and future perspectives, as requested.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Authors have revised the manuscript carefully so it can be accepted for publication.