Latest Developments and Insights of Orthopedic Implants in Biomaterials Using Additive Manufacturing Technologies
Round 1
Reviewer 1 Report
1. although it is a review paper, we did not found any further study and points for AMed orthopedic implants. For example, the authors should stated a case study fully point out the AM process, materials, biocompatibility, corrosion and mechanical properties with challenges.
2. in line 52, the biodegradable effect is only for Mg alloy not for Ti, Co-Cr-Mo.
3. All the AM process only for common introduction. It is difficult to understand the relationship with orthopedic implants
4. the authors did not show the mechanical properties, young's modulus, corrosion study in this article.
Author Response
Please check the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Dear Authors,
Please find below my comments/observations regarding your manuscript:
1. p. 2: “Metals and alloys such as, titanium, titanium alloys, cobalt chromium alloys and stainless steel are the main materials used as implants. These are also biodegradable materials”. Here, it must be done a correction, because Ti-alloys, Co-Cr and stainless steel are not biodegradable alloys, they are only biocompatible alloys which is something else. Biodegradable are, for example, Mg-base alloys. Please revise the sentence.
2. P.2: “Several review papers related to biomaterials were published in recent years such as references [38–43], among others“. Please provide a short description of what exactly the references report [38-43]. It is not enough just to remember them, you must also say what they refer to.
3. P.2: “for example Attar et al [44] used metals which are accepted by the living tissues“. What are these metals exactly? Please elaborate.
Moreover, the next sentence comes which again refers to metals in general, without specifying particularly what it is about:
“They reported that metals does not affect negatively to the human body and will have good mechanical properties, high strength-to-weight ratio and have excellent corrosion resistance”
It is known that not all metals are biocompatible with the tissues of the human body. So, we cannot consider them all together. Metals such as Ni, Al, V and others are already proven to be harmful to the human body.
Therefore, considering obs. No. 1-3, please revise this part of the text – introduction – with more attention to the detail of what is exposed.
The exposition must include concrete data and not generalities, as many examples of metallic materials as possible, and not just "metals" in general.
In addition, it is true that the bibliographic references in large numbers reflect an up-to-date coverage of the specialized literature, but not when they are listed together in a block, without specifying concrete data from each.
4. The use of English language should be corrected in all the manuscript.
5. The chapters 2.1, 2.2 and 2.3 are almost identical to those from chapter 1. Only the references are changed. For example: “These required metal parts are manufactured by traditional processing technologies includes casting, machining, powder metallurgy all of these processes need more time, energy and have high metal consuming rate. Mostly the metals are used for joint replacements, dental roots, and orthopedic fixations and for Stents.” This paragraph is used identically two times, at p.2 and p.3 again.
Anyway, the exposition / description of the types of materials used (metals, ceramics, polymers) is very superficial, with well-known and very general data. This part of the text needs to be revised also.
6. P.4: “From the above literatures, it was observed that the most accepted and widely used biomaterials are metallic biomaterials “. Unfortunately, it is a wrong conclusion. First of all, the three types of materials mentioned in the text (metallic, ceramic and polymeric) are treated independently, without making comparisons between them, without comparing the advantages / disadvantages of each one. So, the conclusion mentioned at the end does not result from the text. Then, as meaning, this is erroneous because, on the contrary, the conclusion would be that all 3 types of materials could be used depending on the type of implant, the location in the human body, the size, the design and, also, depending on the mechanical demands to which it is subjected. Therefore, please revise this part of the text as well.
7. It is not said who did the statistics regarding the data from figure 6. Reference…?
8. Table 1 brings together types of AM-methods that are also used for other medical activities, not only for obtaining bone implants – the initially declared objective of the work. For example: “surgical planning, medical education”. What's the point? Table 1 needs to be revised.
9. P.10: “From the above literatures upon the authors’ perspective, DED is the most efficiently used AM technique for making implants. Among them Electron beam DED technique is most accepted “.
Corroborating with observation no. 6, here also the conclusion is forced, and does not emerge from the text. Why wouldn't the other methods be suitable for obtaining metal implants? The text does not say anything about this. In addition, the AM methods are treated independently from 3.1 to 3.7 (7 methods) from which it does not appear that the electron beam is a DED method. The text needs to be revised.
10. Chapter 4 also needs to be revised. First, additions must be made with much more concrete data for each exposed material, and not generalities already known to specialists in the field. Then, the numerous content errors must be corrected. For example:
- “SS is an alloy mainly made of nickel, chromium and molybdenum”. SS is mainly made from iron; nickel, chromium and molybdenum are the main alloying elements. In addition, SS represent a large class of steels; here it ‘s recommended to specify what type of SS is suitable for bone implants: austenitic, ferritic etc.
- “Ti and its alloys…are one of the few materials that do not contain calcium phosphate.” It is wrong? It is good? an explanation should be added here
- “the defects of Ti such as low elastic modulus” (the same thing is repeated three rows below in the text). For biomaterials used as bone implants, a low elastic modulus is benefic because it reduces the well-known “stress shielding” effect. Therefore, a low elastic modulus is not a defect.
- “Aluminum which has high oxidation rate”. Aluminum oxidizes only until a passivated layer is created; therefore, it is considered to be a metal with high corrosion resistance.
In this chapter 4, apart from SS, "metals" are always mentioned and very little "alloys" which are otherwise the most frequently used; no particular composition is indicated, only generalities.
11. Chapter 5.1 represent only generalities, nothing new or more specific.
12. the organization of the work must be improved because the ideas are repeated from one chapter to another, giving the impression of being chaotic and disorganized. For example, data on the use of Ti and its alloys can be found in chapter 2.1, 4.3 and 5.2. And, anyway, these data are mostly repeated. The same for AM procedures. I think that a more careful systematization should be considered.
13. the discussion part is confused with the final conclusions, therefore they could be united in a single part
Author Response
Please check the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
A large amount of information was analyzed in the manuscript, all main aspects of the topic were discussed. It seems to be interesting and helpful for readers, especially Table 3. However, some information, discussion and conclusions are missed from my point of view.
I suggest to revise the manuscript according following comments:
- Line 237: Statement that PBF approach does not need any structural support is not correct. In many cases support structures are needed to overcome shape distortions of the fabricated sample.
- Description of various AM approaches does not contain information about their accuracy and resolution which may be determining factor to choose the proper technique for implants fabrication.
- “TYPES OF METAL IMPLANTS” omitted the description of nitinol as one of the common 3D-printed material for medical application.
- Line 695: First conclusion should be expanded describing different AM techniques. Suggestions about which technique is best suited for specific applications and materials should be given.
Thus, I would recommend to reconsider the manuscript after major revision.
Author Response
Please check the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
The review is devoted to the analysis of the latest developments in the field of manufacturing orthopedic implants using additive manufacturing. The review considered 296 studies on this topic for the period from 1998 to 2022. The review is well structured and consists of 6 sections. The conclusions reflect the essence of the review and the results of the analysis. As wishes for the future, authors can be recommended to use vector graphics editors when creating drawings. The quality of the drawings in this review is not very high. This is especially true for Figures 1-5. The review will undoubtedly be useful to a large number of researchers, since this topic is very popular, and the review is carried out at a high scientific level.
Author Response
Thank you for your valuable comments. We’ll consider each of your suggestions with high importance and will include in our future works.
Round 2
Reviewer 1 Report
1. More literatures have reported the basic introduction of the processs. We would like to propose that the authors might think about the case report for each AM process and point out the state of art and challenges
2. Porous strcuture is vey importatnt for orthpedic implants which can moderfy the Young's modulus and mechanical properties. If the authors can report different porous strcture and materials for mechanical properties. It will attract the readers.
Author Response
Thank you for your comments
- The nature of the review is to identify the latest developments of orthopedic implants made using AM technologies. We focused on type of AM applications and materials used for making medical implants. A Case study was mentioned in 5.2 (Titanium alloys in medical implants) but this was to compare different metals and to highlight the property of Ti alloys.
- Property of Porous tantalum is mentioned in Table 2. Moreover Porous Ti alloys are considered in making implants used in the case study mentioned in section 5.2. Furthermore, effect of porosity is briefly noted in 5.4 and 5.5. More reference added.
Reviewer 2 Report
Since it is a review type manuscript, I would recommend the introduction of a table of contents at the beginning which, in my opinion, would help a lot to increase the attractiveness of the article and make it easier to read.
Author Response
Thank you for your comment. Table of contents added as appendix A.
Reviewer 3 Report
I am satisfied with given answers and corrections, but the point about accuracy of different AM methods needs improvement. And I still disagree with justification of the first conclution since "the ability to control the grain structure" is true also for LPBF technique. Moreover, LPBF is characterized as method with the highest accuracy in metal 3D-printing.
Author Response
Thank you for the findings. The statements are modified. More reference added.
Authors came into a conclusion after evaluating the overall characteristics. Mentioned in Ref [91,92], 3.1 that DED has lower accuracy than PBF. But DED is faster and less expensive as compared to PBF when creating mid-size metal part. For the part that is deposited while doing DED requires significantly less material removal to achieve a finished part compared to a machined part.
Round 3
Reviewer 1 Report
In my suggestion, we prefer to stress the content of the AM process introduction and strong link to the case study for medical.
Author Response
Thank you for your comments
A newly added case study related to Producing hip implants of titanium alloys by additive manufacturing is briefly mentioned in 5.1 above table 4.
Reviewer 3 Report
Thank you for careful attention to my comments, I am satisfied with given answers and corrections made, thus will recommend to accept the manuscript in present form.
Author Response
Thank you for your findings. Your suggestions were really helpful.
