Surface Characteristics of Esthetic Nickel–Titanium and Beta-Titanium Orthodontic Archwires Produced by Plasma Electrolytic Oxidation (PEO)—Primary Results
, Jean-Philippe Becker 1,*,†, Ralf Smeets 1,2, Martin Gosau 2, Germain Becker 2, Bärbel Kahl-Nieke 3, Anne-Kathrin Jung 1, Max Heiland 4, Alexander Kopp 5, Mike Barbeck 1,*,† and Till Koehne 3,*,†Round 1
Reviewer 1 Report
Dear Authors,
I have read the manuscript and I have found it interesting for orthodontists. Some questions raised. Enlisted please find my comments.
Abstract. Line 24. “Cytocombability”. Please correct into “Cytocompatibility”.
Abstract. Line 28. Authors stated that “The PEO coatings were 15 to 20 μm thick and esthetically pleasing.”. Esthetical consideration is strictly subjective. Moreover, esthetic evaluation was not among the scopes of the present research. Please remove “esthetically pleasing”.
Introduction. Authors stated “The development of tooth-colored ceramic brackets has significantly improved the aesthetics and acceptance of labial fixed appliances (4)”. It is true but incomplete. Aesthetic brackets realized with other materials have been recently introduced. Authors could state that “The development of tooth-colored ceramic, polyoxymethylene, glass fiber, sapphire, brackets (Light energy transmission through six different makes of ceramic orthodontic brackets. Aldossary MS, Abu Hajia SS, Santini A. Int Orthod. 2018 Dec;16(4):638-651) has significantly improved the aesthetics and acceptance of labial fixed appliances (4)”.
Introduction. Authors stated “New esthetic materials such as fiber-reinforced plastic wires were also clinically unsuccessful due the inferior mechanical properties of these archwires as compared to those of conventional nickel-titanium (Niti) and beta-titanium (Beta-Ti) archwires (7).”. The sentence could be explained more extensively. Authors could state that “New esthetic materials such as fiber-reinforced plastic have been recently introduced in Dentistry with many purposes. These materials present high stiffness and strength per weight when compared with other structural materials along with adequate toughness (Fiber-Reinforced Composites for Dental Applications. Scribante A, Vallittu PK, Özcan M. Biomed Res Int. 2018 Nov 1;2018:4734986.). However, fiber reinforced plastic orthodontic wires have been tested but they were clinically unsuccessful due the inferior mechanical properties of these archwires as compared to those of conventional nickel-titanium (Niti) and beta-titanium (Beta-Ti) archwires (7).”
Materials and Methods. Authors stated “0.014-inch NiTi archwire is a highly flexible wire that is used for the initial alignment of irregular teeth”. Please add a reference for this statement.
Materials and Methods. Authors stated “The 0.19x0.25-inch Beta-Ti archwire is a more rigid archwire that is used for the working and final phase of orthodontic treatment”. Please add a reference for this statement.
Materials and Methods. Authors stated “For extraction analysis, all test samples were extracted for 72 hours in cell culture medium (MEM (Minimum Essential Medium), 10% fetal bovine serum, penicillin/streptomycin (100 U/mL each, all from Life Technologies, Carlsbad, USA) and 4mM L-glutamine (Sigma-Aldrich, St. Louis, USA) under cell culture conditions (37 °C, 5% CO2 and 95% humidity) with a surface to volume ratio of 3 cm2/ml.”. Please add a reference for this method.
Materials and Methods. Authors stated “The insertion and ligation of the archwire were repeated three times using the same archwire”. Why Authors decided three times? Please specify if this method has been used also in previous studies and if a sample size calculation has been performed
Materials and Methods. Authors stated “The data of the cytocompatibility extract results were statistically analyzed by an analysis of variance (ANOVA) combined with a Tukey’s multiple comparisons”. ANOVA is used only for data that follow Gaussian distribution. Please state if data distribution has been tested before choosing ANOVA and specify the name of the test (e.g.: Kolmogorov-Smirnov?).
Materials and Methods. Authors stated “Macroscopically, an aesthetically pleasing surface could be generated”. Aesthetically pleasing surface is subjective. Please change the sentence into “tooth-like surface” or somewhat else.
Materials and Methods. Authors stated “The PEO-particles were deposited along the entire surfaces and formed a layer between 15 to 20 μm in thickness”. Please add a reference for this statement
Results. Authors reported that “Cytocompatibility analyses revealed that both treated and untreated NiTi and Beta-Ti archwires are safe according EN ISO 10993-5/-12.”. Please add the reference of the ISO standard.
Results. Authors reported that “Both ceramized and untreated archwires showed no significant differences compared to the negative control.”. Please add P value.
Results. Authors reported that “all test materials and the negative control showed mostly green living and adherent cells compared to the positive control, on which fewer and red dead cells were visible”. Please add P value.
Results. Authors reported that “both ceramized pendants revealed superior compatibility comparable with the negative control”. Please add P value.
Results. Authors stated “Both archwires could be easily inserted in the slots of the ceramic brackets and the clinical handling of PEO-coated archwires was not different from that of non-coated control wires”. These are personal considerations that are not related to the results of the study and should be cropped or moved into discussion section and discussed further with proper references.
Discussion. The paragraph is very short. Authors could elongate it pointing out some more aspects related to their experiments.
Discussion. Authors tested niti and TMA wires. In fact, many orthodontists use stainless steel wires during final movements. Therefore, a sentence about the lack of testing stainless steel wires should be added.
Discussion. Authors performed the insertion and ligation of the archwire were repeated three times using the same archwire. Please discuss (as a limitation of the present report) the importance of wear that could alter the results.
Discussion. PEO coated wires seems to be a viable alternative to conventional wires. However this new technology has to be tested further before clinical use: friction and mechanical behavior of the wires should be tested in future. This should be pointed out at the end of discussion section.
References. Few references have been reported. Please add some more studies. Some references have been suggested in previous comments.
Figures. In the version that I have downloaded I cannot see Figures. Please resubmit with figures added in the main text.
Tables. No tables have been given showing the results. Please add a table with descriptive statistics (Mean, Standard deviation, Minimum, Median and Maximum for each group tested) of the results.
Author Response
Reviewer 1
Abstract. Line 24. “Cytocombability”. Please correct into “Cytocompatibility”.
Answer: Done.
Abstract. Line 28. Authors stated that “The PEO coatings were 15 to 20 μm thick and esthetically pleasing.”. Esthetical consideration is strictly subjective. Moreover, esthetic evaluation was not among the scopes of the present research. Please remove “esthetically pleasing”.
Answer: Done.
Introduction. Authors stated “The development of tooth-colored ceramic brackets has significantly improved the aesthetics and acceptance of labial fixed appliances (4)”. It is true but incomplete. Aesthetic brackets realized with other materials have been recently introduced. Authors could state that “The development of tooth-colored ceramic, polyoxymethylene, glass fiber, sapphire, brackets (Light energy transmission through six different makes of ceramic orthodontic brackets. Aldossary MS, Abu Hajia SS, Santini A. Int Orthod. 2018 Dec;16(4):638-651) has significantly improved the aesthetics and acceptance of labial fixed appliances (4)”.
Answer: We added the suggested improvements and literature.
Introduction. Authors stated “New esthetic materials such as fiber-reinforced plastic wires were also clinically unsuccessful due the inferior mechanical properties of these archwires as compared to those of conventional nickel-titanium (Niti) and beta-titanium (Beta-Ti) archwires (7).”. The sentence could be explained more extensively. Authors could state that “New esthetic materials such as fiber-reinforced plastic have been recently introduced in Dentistry with many purposes. These materials present high stiffness and strength per weight when compared with other structural materials along with adequate toughness (Fiber-Reinforced Composites for Dental Applications. Scribante A, Vallittu PK, Özcan M. Biomed Res Int. 2018 Nov 1;2018:4734986.). However, fiber reinforced plastic orthodontic wires have been tested but they were clinically unsuccessful due the inferior mechanical properties of these archwires as compared to those of conventional nickel-titanium (Niti) and beta-titanium (Beta-Ti) archwires (7).”
Answer: We added the suggested improvements and literature.
Materials and Methods. Authors stated “0.014-inch NiTi archwire is a highly flexible wire that is used for the initial alignment of irregular teeth”. Please add a reference for this statement.
Answer: Done.
Materials and Methods. Authors stated “The 0.19x0.25-inch Beta-Ti archwire is a more rigid archwire that is used for the working and final phase of orthodontic treatment”. Please add a reference for this statement.
Answer: Done.
Materials and Methods. Authors stated “For extraction analysis, all test samples were extracted for 72 hours in cell culture medium (MEM (Minimum Essential Medium), 10% fetal bovine serum, penicillin/streptomycin (100 U/mL each, all from Life Technologies, Carlsbad, USA) and 4mM L-glutamine (Sigma-Aldrich, St. Louis, USA) under cell culture conditions (37 °C, 5% CO2 and 95% humidity) with a surface to volume ratio of 3 cm2/ml.”. Please add a reference for this method.
Answer: We cited two references from our previous research at the beginning of the paragraph. If necessary, we could cite both references after each sentence but are afraid that the clarity could be impaired.
Materials and Methods. Authors stated “The insertion and ligation of the archwire were repeated three times using the same archwire”. Why Authors decided three times? Please specify if this method has been used also in previous studies and if a sample size calculation has been performed
Answer: This part of study was performed from a practical point. We repeated the insertion three times because we think that materials should be reliable by this number in orthodontics. We tried to improve the sentence by writing that we decided to repeat the insertion three times because from our practical point of view. We cannot provide any appropriate literature.
Materials and Methods. Authors stated “The data of the cytocompatibility extract results were statistically analyzed by an analysis of variance (ANOVA) combined with a Tukey’s multiple comparisons”. ANOVA is used only for data that follow Gaussian distribution. Please state if data distribution has been tested before choosing ANOVA and specify the name of the test (e.g.: Kolmogorov-Smirnov?).
Answer: Done.
Materials and Methods. Authors stated “Macroscopically, an aesthetically pleasing surface could be generated”. Aesthetically pleasing surface is subjective. Please change the sentence into “tooth-like surface” or somewhat else.
Answer: We improved this sentence.
Materials and Methods. Authors stated “The PEO-particles were deposited along the entire surfaces and formed a layer between 15 to 20 μm in thickness”. Please add a reference for this statement
Answer: We analyzed all our SEM pictures and measured the approximate thickness of the ceramic. We revised this sentence and wrote “20 to 30 µm in thickness”
Results. Authors reported that “Cytocompatibility analyses revealed that both treated and untreated NiTi and Beta-Ti archwires are safe according EN ISO 10993-5/-12.”. Please add the reference of the ISO standard.
Answer: Done.
Results. Authors reported that “Both ceramized and untreated archwires showed no significant differences compared to the negative control.”. Please add P value.
Answer: There are many p-values since of the multiple comparisons. We ask not to show these values in detail to keep overall clarity.
Results. Authors reported that “all test materials and the negative control showed mostly green living and adherent cells compared to the positive control, on which fewer and red dead cells were visible”. Please add P value.
Results. Authors reported that “both ceramized pendants revealed superior compatibility comparable with the negative control”. Please add P value.
Answer: We revised the sentences. We cannot add a p-value because the direct evaluation compares all test samples from a qualitative point of view.
Results. Authors stated “Both archwires could be easily inserted in the slots of the ceramic brackets and the clinical handling of PEO-coated archwires was not different from that of non-coated control wires”. These are personal considerations that are not related to the results of the study and should be cropped or moved into discussion section and discussed further with proper references.
Answer: We revised this part and further discussed the practical considerations in the discussion section.
Discussion. The paragraph is very short. Authors could elongate it pointing out some more aspects related to their experiments.
Answer: We revised the discussion and tried to insert some interesting points.
Discussion. Authors tested niti and TMA wires. In fact, many orthodontists use stainless steel wires during final movements. Therefore, a sentence about the lack of testing stainless steel wires should be added.
Answer: To our knowledge and experiments, stainless steel can not be treated by means of PEO. We added a sentence that stainless steel could not be investigated and more research should be done to make PEO on steel applicable.
Discussion. Authors performed the insertion and ligation of the archwire were repeated three times using the same archwire. Please discuss (as a limitation of the present report) the importance of wear that could alter the results.
Answer: Thank you for this comment. We revised this part of the discussion and added two sentences regarding wear and corrosion particles.
Discussion. PEO coated wires seems to be a viable alternative to conventional wires. However this new technology has to be tested further before clinical use: friction and mechanical behavior of the wires should be tested in future. This should be pointed out at the end of discussion section.
Answer: We already stated that biomechanical properties should be further investigated and revised this sentence by adding friction and wear resistance in brackets.
References. Few references have been reported. Please add some more studies. Some references have been suggested in previous comments.
Answer: We added some more references and extended the discussion.
Figures. In the version that I have downloaded I cannot see Figures. Please resubmit with figures added in the main text.
Answer: We received a message of Ms. Bo beforehand and propounded a revised version with figures. We now submit a revised version with all reviewer comments and figures inside the text version.
Tables. No tables have been given showing the results. Please add a table with descriptive statistics (Mean, Standard deviation, Minimum, Median and Maximum for each group tested) of the results.
Answer: We now submit a version with figures. Figure 2 shows the significant differences between the groups. In our opinion, a table with all differences may be confusing to the reader. However, if wanted, we can provide a table with all the necessary information.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This is an interesting study about new oxidation process to orthodontic archwires
Some criticisms are present:
1)The citotoxicity assay should be explained better, beginning to the principal in vitro tests evaluation to assess it.In this context these two literature works should be added and discussed in the text
Pagano S, Chieruzzi M, Balloni S, Lombardo G, Torre L, Bodo M, Cianetti S, Marinucci L Biological, thermal and mechanical characterization of modified glass ionomer cements: the role of nanohydroxyapatite, ciprofloxacin and zinc l-carnosine. Mater Sci Eng C Mater Biol Apple 2019 Jan 1;94:76-85
Balloni S, Locci P, Lumare A, Marinucci L Cytotoxicity of three commercial mouthiness on extracellular matrix metabolism and human gingival cell behavior Toxicology in vitro, Vol 34, pag 88-96, 2016
2)Auhtors shlud explain time choice of cytotoxicity test and why not more long time (24, 48, 72 h.etc.)
3)Some technical test should be added about traditional ceramic arch wires with the same culture medium
Author Response
1)The citotoxicity assay should be explained better, beginning to the principal in vitro tests evaluation to assess it. In this context these two literature works should be added and discussed in the text
Pagano S, Chieruzzi M, Balloni S, Lombardo G, Torre L, Bodo M, Cianetti S, Marinucci L Biological, thermal and mechanical characterization of modified glass ionomer cements: the role of nanohydroxyapatite, ciprofloxacin and zinc l-carnosine. Mater Sci Eng C Mater Biol Apple 2019 Jan 1;94:76-85
Balloni S, Locci P, Lumare A, Marinucci L Cytotoxicity of three commercial mouthiness on extracellular matrix metabolism and human gingival cell behavior Toxicology in vitro, Vol 34, pag 88-96, 2016
Answer: We revised this part, added the references and give more details for the general understanding of the principle. We refer to a detailed description in other publications.
2)Auhtors shlud explain time choice of cytotoxicity test and why not more long time (24, 48, 72 h.etc.)
Answer: Done.
3)Some technical test should be added about traditional ceramic arch wires with the same culture medium
Answer: We compared the untreated test samples with the ceramized test samples (Figures 2, 3). To our knowledge, ceramic arches are not available in orthodontics.
Author Response File: Author Response.pdf
Reviewer 3 Report
Dear Authors
Please check the English and edit a few latest papers related to the experiment.
Author Response
Reviewer 3:
Please check the English and edit a few latest papers related to the experiment.
Answer: We thank the reviewer for this comment and checked the manuscript accordingly.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Manuscript has been revised.
Good job!
