Development of Zirconium-Based Alloys with Low Elastic Modulus for Dental Implant Materials
Round 1
Reviewer 1 Report
The manuscript topic is actual and the paper has merit. It could be attractive, adequate and interesting for the journal readers. However there are some point that authors should address in order to have a final more complete paper. Authors should underline the limitation of the value of the study, and the clinical and surgical implication of the presented study should be added. At this stage the paper seems to be directed to surgeons and not researchers. Please emphasize the clinical application of the study, and its scientific rationale. References are inadequate. Introduction section is poor. Some more references about the recent discoveries about bioamterials in the field of dental implants should be added (2013-2019).
Some recent samples as follows:
Bioactive Titanium Surfaces: Interactions of Eukaryotic and Prokaryotic Cells of Nano Devices Applied to Dental Practice. Biomedicines 2019, 7, 12
Sandblasted and Acid Etched Titanium Dental Implant Surfaces Systematic Review and Confocal Microscopy Evaluation. Materials 2019, 12, 1763
Therefore a comparison between Zirconium (the material proposed in the study) and Titanium based alloy should be better performed cause the 90 % of dental implant is structured by Titanium alloy today.
Oveall a good paper
Author Response
Reply to the review’s comments:
As the reviewer's comment, the study has limitations for the clinical and surgical applications because this may be the first report of the Zr-Cu-Sn ternary alloy for the dental biomaterials application. Therefore, we just consider the mechanical properties to mimic the mechanical properties of bone substitutes for the stress shielding effect. For further research, biocompatibility tests, cytotoxicity tests, and in vitro studies should be conducted more for clinical and surgical applications. More recent and adequate references are added and revised. Also, the introduction was revised. All of the revised parts were highlighted in blue color.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this paper, the author reported zirconium-based alloys with modulus range from 15 to 30 GPa which have a potential to serve as implant alloy for bone (20-30 GPa). Characterizations have been done on XRD, OM and SEM microstructure, mechanical and corrosion measurement to confirm the alloys. Here are four points of my concern about this paper.
The development for next generation bone biomaterials is following the trend with biodegradable, biocompatible and mimicking bone mechanical property. In this paper, the author use “next generation” in title but didn’t provide any in vitro/in vivo experiments is very strange. I suggest author to rename the title with a proper description of the paper content. What is the fatigue resistance of these zirconium-based alloys? In the paper, the word “bio-materials” confuse me so much. The conclusion part (1) to (3) need to be added to results and discussion part with further discussion.Author Response
Reply to the review’s comments:
As the reviewer's comment, the title was revised to “Development of Zirconium-based alloys with low elastic modulus for dental Implants materials”. The most Zr-based alloys are developed for the application of nuclear power component. In this study, it may be the first report of the Zr-Cu-Sn ternary alloy for the dental biomaterials application. There is no report about the fatigue resistance of the Zr-Cu-Sn ternary alloy. The word “bio-materials” was revised to biomaterials in the text. For further research, the fatigue tests should be conducted more such as fatigue limit and crack propagation. Also, the conclusion part (1) to (3) was added to the results and discussion part. All of the revised parts were highlighted in yellow color.
Author Response File: Author Response.pdf
Reviewer 3 Report
The paper well reports about the characterization of a novel metal alloy for implant/prosthesis design. The new material is characterized by a low elastic modulus, aiming to avoid stress-shielding phenomena.
In detail, the paper well provides data about the micro-structural configuration of the material, mechanical properties and corrosion behavior.
With regard to the definition of mechanical properties, compression tests have been developed. This is a limitation, because of the non symmetric tension-compression response of metallic materials, with particular regard to the inelasticity region. A discussion about this limitation should be reported.
Furthermore, the authors report about the advantage of a low modulus biomaterial because of its capability to limit stress-shielding phenomena. The different elastic modulus also influences press-fit phenomena. Press-fit is usually imposed aiming to provide primary stability. As an example, the mechanical analysis of press-fit is reported by:
Natali AN, Carniel EL, Pavan PG. Investigation of viscoelastoplastic response of bone tissue in oral implants press fit process. J Biomed Mater Res B Appl Biomater. 2009 Nov;91(2):868-75. doi: 10.1002/jbm.b.31469.
The authors are encouraged to comment about the influence of the biomaterial modulus on press fit phenomena.
Author Response
Reply to the review’s comments:
As the reviewer's comment, there is a limitation of the compressive test in this study because of the non-symmetric tension-compression response of materials. In metallic materials, we usually consider the stress-strain responses in both tensile and compression tests are symmetric in the elastic regions. However, the maximum strength of the compressive test is higher than that of the tensile test. In this study, this Zr-Cu-Sn ternary alloy is designed and developed for dental biomaterials. Therefore, the compressive strength obtained by the compression test could be meaningful data more than the tensile test data in this study.
Also, as the reviewer's comment, the press-fit phenomenon occurring at implant insertion induces biomechanical effects in the bone tissues, which ensure primary implant stability. In particular, the major press fit should be obtained by increasing the difference between the diameter of the implant and the diameter of the drilled hole in terms of the development of inelastic phenomena. In this point of view, this Zr-Cu-Sn ternary alloy has the same level of elastic modulus with human bone. Therefore, we can expect that the press-fit phenomenon may be reduced. We need further studies about the determination of the optimal press-fit condition with an equally distributed pre-load on both the cortical and trabecular structure around the implant for clinical and surgical applications. The comment about the press fit was added and revised in this manuscript with highlight. All of the revised parts were highlighted in green color.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Authors made excellent job addressing all the reviewers requests
Reviewer 2 Report
I did not have any comments for authors. This review is ready to publish in this Journal.
