The Effect of Surface Treatments of Presintered Zirconia on Sintered Surfaces

Round 1

Reviewer 1 Report

The article “Effectiveness of Surface Treatments to Pre-sintered Zirconia for Dental Restorations and Implants” compared the effect of zirconia surface treatment in its pre-sintered state (7 surface treatments), compared to the untreated control.

This topic is of interest since increasing bonding increase the longevity of zirconia restorations.

Some major improvements are needed before possible publication.

Lines 50-59

The authors could slightly expand the concept by explaining to the reader why zirconia restorations are increasingly used in restorative dentistry (and the different esthetic properties of different types of zirconia: more esthetics, optical and mechanical characteristics similar to natural teeth, shades, the ability to exploit the color of the substrate.

Support this sentence with some references, such for example:

Comba, A., Paolone, G., Baldi, A., Vichi, A., Goracci, C., Bertozzi, G., & Scotti, N. (2022). Effects of Substrate and Cement Shade on the Translucency and Color of CAD/CAM Lithium-Disilicate and Zirconia Ceramic Materials. Polymers, 14(9), 1778. https://doi.org/10.3390/polym14091778

Lines 54-5:

Please change “like” to “close to”

Lines 63-73:

Is the following paragraph really important to be included in the article? The reviewer to erase it or at least to reduce to a single sentence related to implant surface. But again: if we are talking about bonding to zirconia, why implant surface is mentioned? Furthermore no studies of osseointegration have been performed:

“In the field of implant dentistry, osseointegration is a biologically dynamic process that is defined as the direct attachment of bone tissue to the implant surface. Studies conducted in-vitro and in-vivo have shown that zirconia implants perform similarly to titanium implants in terms of osseointegration. Successful rapid osseointegration depends on several factors among them the surface characteristics [7]. The surface treatment to implants are essential for cell adhesion and protein adsorption [8]. The surface properties depend on the surface treatment, which affects the pace of osseointegration and biomechanical fixation, in addition to the chemical composition. Surface roughness or coating could be used to modify the surface [9]. The degree and speed of osseointegration of titanium dental implants are significantly influenced by the surface roughness[10]. It has been demonstrated that roughened implants promote initial fixation to bone and mechanical anchoring [11–13].”

The authors could also consider improving the manuscript’s title.

Statistical analysis 

Were the data distributed normally? How did the authors check the normality?

Discussion

The authors should increase the comparison with similar studies. Few articles are compared with the results of the current study.

The authors should add Tensile or Micro-Tensile to future studies since tested pre-treatments could affect bond strength.

Author Response

Reviewer 1:

Thanks for your valuable comments which improved the quality of this research. All the comments were done, and the modifications are highlighted in yellow.

Comment: Lines 50-59

The authors could slightly expand the concept by explaining to the reader why zirconia restorations are increasingly used in restorative dentistry (and the different esthetic properties of different types of zirconia: more esthetics, optical and mechanical characteristics similar to natural teeth, shades, the ability to exploit the color of the substrate.

Support this sentence with some references, such for example:

Comba, A., Paolone, G., Baldi, A., Vichi, A., Goracci, C., Bertozzi, G., & Scotti, N. (2022). Effects of Substrate and Cement Shade on the Translucency and Color of CAD/CAM Lithium-Disilicate and Zirconia Ceramic Materials. Polymers, 14(9), 1778. https://doi.org/10.3390/polym14091778

Reply: We added the increased use of zirconia in restorative dentistry with this related valued reference.

Comment: Lines 54-5: Please change “like” to “close to”

Reply: Done

Comment: Lines 63-73:

Is the following paragraph really important to be included in the article? The reviewer to erase it or at least to reduce to a single sentence related to implant surface. But again: if we are talking about bonding to zirconia, why implant surface is mentioned? Furthermore no studies of osseointegration have been performed:

“In the field of implant dentistry, osseointegration is a biologically dynamic process that is defined as the direct attachment of bone tissue to the implant surface. Studies conducted in-vitro and in-vivo have shown that zirconia implants perform similarly to titanium implants in terms of osseointegration. Successful rapid osseointegration depends on several factors among them the surface characteristics [7]. The surface treatment to implants are essential for cell adhesion and protein adsorption [8]. The surface properties depend on the surface treatment, which affects the pace of osseointegration and biomechanical fixation, in addition to the chemical composition. Surface roughness or coating could be used to modify the surface [9]. The degree and speed of osseointegration of titanium dental implants are significantly influenced by the surface roughness[10]. It has been demonstrated that roughened implants promote initial fixation to bone and mechanical anchoring [11–13].”

Reply: We reduced this part, leaving a small sentence taking about zirconia implant.

Comment: The authors could also consider improving the manuscript’s title.

Reply: The title was modified. 

Comment: Statistical analysis 

Were the data distributed normally? How did the authors check the normality?

Reply: This sentence was added: The Shapiro-Wilk test revealed that the data had a normal distribution.

Comment: Discussion

The authors should increase the comparison with similar studies. Few articles are compared with the results of the current study.

Reply: Done, related previous articles are added.

Comment: The authors should add Tensile or Micro-Tensile to future studies since tested pre-treatments could affect bond strength.

Reply: We added this sentence at the end of discussion: It is also recommended to add bond strength tests to future studies to investigate the effect of these pre-treatments on their bonding to different substructures.

Reviewer 2 Report

The inert nature of zirconia has led to thousands of publications from 2010 up today. Good conceptualization, however the quality of presentation decreases the value of the results.

Introduction: Line 70 Surface roughness or coating could be used to modify the surface : Should be rephrased " surface roughness is not a method modifying a hard surface it is the arithmetic result of a treatment and has too many parameters. In this sould be added other treatments as laser treatment described by Delgado-Ruiz as early as 2011 https://doi.org/10.1002/jbm.b.31743.

line 96:"Unfortunately, surface treatments of sintered zirconia could decrease its mechanical properties, be complicated, or be ineffective". It should be rephrased not understandable. Plus airborne particle abrasion results in sintered zirconia surface are effective or ineffctive in roughness depending on material (alumina,glass), size and how aggressive is the technique(pressure,time,distance)  DOI: 10.4012/dmj.2018-358

The results of sandblasting in t>m transformation are contradictory and should be interpreted with caution. 

line 99: It should be addded that fully sintered zirconia is difficult to cut and modify and causes extremely severe wear in cutting tools. This is the main reason for which most manufacturers and systems prefer handling of zirconia  in green-stage

lines 104-110: are unnecessary since zirconia phases are almost common knowledge in most readers. Should be condensed or rephrased.

lines 116-"Although pre-sintered zirconia's surface treatment may be less difficult due to its po- 117 rous, softer structure, it is not frequently studied"

I disagree since many studies have been conducted modifying zirconia in green stage especially for adhesive potential 

Materials and methods: Classification of Table 1 should have specific names as groups for each treatment .This will help the reader to understand SEM images

Discussion: The results of biaxial test especially the decrease of sttt7 group should be better analyzed. A possible LTD could be a main reason for this result. 

It is a basic drawback that surface roughness was not measured.

Conclusions: Should be more precise for each treatment 

Minor editing is required. 

Author Response

Reviewer 2:

Thanks for your valuable comments which improved the quality of this research. All the comments were done, and the modifications are highlighted in yellow.

Comment: Introduction: Line 70 Surface roughness or coating could be used to modify the surface : Should be rephrased " surface roughness is not a method modifying a hard surface it is the arithmetic result of a treatment and has too many parameters. In this sould be added other treatments as laser treatment described by Delgado-Ruiz as early as 2011 https://doi.org/10.1002/jbm.b.31743.

Reply: Done. Thanks for your valued comments.

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Comment: line 96:"Unfortunately, surface treatments of sintered zirconia could decrease its mechanical properties, be complicated, or be ineffective". It should be rephrased not understandable. Plus airborne particle abrasion results in sintered zirconia surface are effective or ineffctive in roughness depending on material (alumina,glass), size and how aggressive is the technique(pressure,time,distance)  DOI: 10.4012/dmj.2018-358

The results of sandblasting in t>m transformation are contradictory and should be interpreted with caution. 

Reply: Done. Thanks for the accurate comment.

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Comment: line 99: It should be addded that fully sintered zirconia is difficult to cut and modify and causes extremely severe wear in cutting tools. This is the main reason for which most manufacturers and systems prefer handling of zirconia in green-stage

Reply: Thanks, we added this sentence at the suggested place.

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Comment: lines 104-110: are unnecessary since zirconia phases are almost common knowledge in most readers. Should be condensed or rephrased.

Reply: Done, this part is summarized and rephrased.

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Comment: lines 116-"Although pre-sintered zirconia's surface treatment may be less difficult due to its porous, softer structure, it is not frequently studied"

I disagree since many studies have been conducted modifying zirconia in green stage especially for adhesive potential

Reply: Done, the sentence is modified.

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Comment: Materials and methods: Classification of Table 1 should have specific names as groups for each treatment.This will help the reader to understand SEM images

Reply: A column is added in table I. Nice idea. Many thanks.

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Comment: Discussion: The results of biaxial test especially the decrease of sttt7 group should be better analyzed. A possible LTD could be a main reason for this result. 

Reply: Done

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Comment: It is a basic drawback that surface roughness was not measured.

Reply: This limitation was written with recommendation to measure it in a following research.

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Comment: Conclusions: Should be more precise for each treatment 

Reply: Done------------------ (The end of comments.. Thanks).

Round 2

Reviewer 1 Report

Dear authors,

the manuscript has improved, though the reviewer still need to 

Support this sentence with some references, such for example:

Comba, A., Paolone, G., Baldi, A., Vichi, A., Goracci, C., Bertozzi, G., & Scotti, N. (2022). Effects of Substrate and Cement Shade on the Translucency and Color of CAD/CAM Lithium-Disilicate and Zirconia Ceramic Materials. Polymers, 14(9), 1778. https://doi.org/10.3390/polym14091778

Reply: We added the increased use of zirconia in restorative dentistry with this related valued reference.

 The reviewer can't see this reference added as the authors reported. Are the authors sure to have uploaded the correct manuscript? Why the authors wrote to have added a reference and then it was not?

Comment: The authors could also consider improving the manuscript’s title.

Reply: The title was modified. 

How was the title modified?

Comment: Discussion

The authors should increase the comparison with similar studies. Few articles are compared with the results of the current study.

Reply: Done, related previous articles are added.

Can you outline which articles were added? I can't see any change in the bibliography.. Which and how many articles were added?

Author Response

Comment: The reviewer can't see this reference added as the authors reported. Are the authors sure to have uploaded the correct manuscript? Why the authors wrote to have added a reference and then it was not?

Reply: The citation was added (Reference no.4)

Comment: The authors could also consider improving the manuscript’s title.

Reply: The title was modified to "Effect of Surface Treatments of Pre-sintered Zirconia on Sintered Surface". 

Comment: The authors should increase the comparison with similar studies. Few articles are compared with the results of the current study. Can you outline which articles were added? I can't see any change in the bibliography. Which and how many articles were added?

Reply: Done, related previous articles are added marked in yellow color (References no. 20, 21, 22, 23, and 33).

Reviewer 2 Report

Much improved manuscript!

Some minor comments 

line 80-83 Surface treatment methods in zirconia material are classified in two major categories: additive techniques such as plasma spray,coatings etc and destructive techniques as sandblasting,laser treatment,acid etching etc check  doi: 10.1016/j.prosdent.2015.09.008.

Conclusions also should be more accurate and more precise without predictions.

Minor mistakes please check carefully

Author Response

Comment:  line 80-83 Surface treatment methods in zirconia material are classified in two major categories: additive techniques such as plasma spray,coatings etc and destructive techniques as sandblasting,laser treatment,acid etching etc check  doi: 10.1016/j.prosdent.2015.09.008.

Reply: Done, in line 90-94 (Reference no. 9). Moreover, all the recommended citations were added (References no. 8, and 10)

Comment: Conclusions also should be more accurate and more precise without predictions.

Reply: Modified.

Round 3

Reviewer 1 Report

The authors have amended all the requests

Reviewer 2 Report

Manuscript was succesufully modified

Well done! 

English language is  fine