Influence of Implant Number on Peri-Implant and Posterior Edentulous Area Strains in Mandibular Overdentures Retained by the New Ti–Zr (Roxolid®) Mini-Implants as Single-Units: In Vitro Study
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsReview of applsci-2870199-peer-review-v1: Is It Possible to Use Less than Four New Ti-Zr Mini-Implants 24 as Single-Units to Support a Mandibular Overdenture? In Vitro 25 Study
The work submitted for evaluation is an experimental model study at a preliminary level.
A few critical remarks: The title in the form of a question does not fit a scientific journal. In my opinion it should be changed.
No authors affiliation. It should be corrected.
Abstract:
L 35-36: No explanation of abbreviations. The ranges of the obtained microstrains values should be added in the abstract.
Introduction:
L 56-57: According to the notation used, it is not clear what category an implant with a diameter of 3.25 mm belongs to. It should be improved.
L 62: What do "longitudinal studies" mean?
L 67-91: Different font size, need to be corrected (in other places too).
L 70: A little over a decade ago - the year the implant was introduced to the market must be provided.
L 71: The company details must be completed.
The introduction needs to be improved. Lack of information about the use of models in experimental research and information about the use and usefulness of the research method (SG). Some interesting information was included in the discussion, it should be used in the introduction.
Materials and Methods
L 98-105: A uniform description of the positioning of mounting holes for implants should be used (eg. "33" or "in the positions of the right and the left canines", chose the one method).
L 131: Where do these torque values come from (how were they measured?), are they consistent with the clinical/manufacturer's recommendations?
The description of the materials lacks basic strength data. Characteristics should be added, including e.g. Young's modulus, tensile, compressive and bending strength.
You should be aware of the influence of ground reaction forces (here a bone model and artificial mucosa) on the results of these tests (it should be used in the introduction.).
L 150: Is cyanoacrylate glue (super glue) a good choice for mounting strain gauges? Why wasn't a system adhesive used? Does "super glue" transfer elastic deformations well?
What was the time from sticking the strain gauges to testing?
L 189: Why were these load values chosen? Why was this loading scheme adopted? Were 50, 100 and 150 N the values of the force acting on the compression pin? These values are small considering the forces developed during occlusal occlusion. The example of classic flexural load was showed at the figure 1. The reaction of the flexural system was calculated? The forces acting on the implants were different than those provided by the authors, this should be checked.
L184-190: The description is not clear to me, it should be illustrated with an appropriate diagram corresponding to the three load positions described.
L 216-217: The figure 2 should be divided accordingly.
The drawing cannot cover until 5 pages.
Graphs do not need value precision up to 10^-2 (vertical axis), this should be changed.
Units must be completed.
No supplementary provided, none of the Tables could be rated.
L 256-257: The figure 3 should be corrected according to the previous instructions.
Discussion:
The discussion should be rewritten taking into account the above comments.
References:
Several literature items are older than 10 years and should be replaced with current ones.
Author Response
Dear reviewer,
I am grateful for the suggestions you gave us to improve our article. I hope we have met your expectations and I send comments in word file too.
Best regards,
Dario Puljic and team
The work submitted for evaluation is an experimental model study at a preliminary level.
A few critical remarks:
The title in the form of a question does not fit a scientific journal. In my opinion it should be changed.
It is a question of preference. Some Editors of scientific journals prefer titles in a form of a question with idea that it will be more intrigate for readers. We offered the new title.
No authors affiliation. It should be corrected. – Done, we added affiliations
Abstract:
L 35-36: No explanation of abbreviations.
-Done, Mini dental implant=MDI, cone beam computed tomography=CBCT
The ranges of the obtained microstrain values should be added in the abstract.
- We did not do it at first due to the word limitation in the abstract.
- We now provided values of the highest strains, which were recorded in the one- and two MDI models. We hope that Editor will allow that, as the word number has increased a little bit
Introduction:
L 56-57: According to the notation used, it is not clear what category an implant with a diameter of 3.25 mm belongs to. It should be improved.
- We added > and < (Narrow dental implants (NDIs) are divided into three categories depending on their diameter: category 3 (>3.3 mm to 3.5 mm wide), category 2 (>2.5 mm to <3.3 mm), and category 1 (≤2.5 mm wide), respectively [12])
L 62: What do "longitudinal studies" mean? We changed longitudinal into prospective clinical studies (in many prospective clinical studies)
L 67-91: Different font size, need to be corrected (in other places too). Done
L 70: A little over a decade ago - the year the implant was introduced to the market must be provided. Done (In 2009, the Ti85Zr15 (Roxolid®) alloy was introduced by the company Straumann Group.) - although it was first presented at the EAO conference in 2008, it was released in 2009. That was the reason why we did not present the exact year.
- and in 2019 Roxolid MDI new system was released, corrected
L 71: The company details must be completed.
Done
The introduction needs to be improved. Lack of information about the use of models in experimental research and information about the use and usefulness of the research method (SG). Some interesting information was included in the discussion, it should be used in the introduction.
We added into the Introduction section the following sentences: In vitro studies are required before safe clinical utilization of any new material, clinical technique or a procedure modification [27–29]. Due to different stiffness of an implant material and the bone, the highest stress is distributed at the implant-bone interface. Peri‑implant strains below 3000 microstrains represent the criteria for a long term survival of any implant supporting a denture [27]. A model mimicking “in vivo” situation and measuring periimplant strains is beneficial to provide insights about real clinical situation.
Materials and Methods
L 98-105: A uniform description of the positioning of mounting holes for implants should be used (eg. "33" or "in the positions of the right and the left canines", chose the one method). Done
L 131: Where do these torque values come from (how were they measured?), are they consistent with the clinical/manufacturer's recommendations?
By a torque wrench during insertion, yes >35N can be immediately loaded, explained
The description of the materials lacks basic strength data. Characteristics should be added, including e.g. Young's modulus, tensile, compressive and bending strength.
We added the data in discussion because data vary slightly between different studies.
You should be aware of the influence of ground reaction forces (here a bone model and artificial mucosa) on the results of these tests (it should be used in the introduction.). Do you mean the pillow effect of mucosa (force reduction, dumping effect)?
L 150: Is cyanoacrylate glue (super glue) a good choice for mounting strain gauges? Why wasn't a system adhesive used? Does "super glue" transfer elastic deformations well? – This glue was provided by the strain-gauge manufacturer and was also used in all other SG similar studies. added
The question of elastic deformation transfer is a good question, but it is beyond our expertise. Some experimental results indicate that strain gauges which used same adhesive gave consistent deformation values. Different glues may give different results Also,.the adhesive thickness should be the lowest and uniformly applied. A linear relationship between adhesive thickness and strain error was found. Up to 51 % strain loss obtained through the numerical models for the adhesive interlayer pointed out that adhesive type must be taken into account in experimental studies since.
We added the reference: Freitas, C., Leite, T.M., Lopes, H. et al. Influence of adhesive on optical fiber-based strain measurements on printed circuit boards. J Mater Sci: Mater Electron 34, 699 (2023). https://doi.org/10.1007/s10854-023-10017-5
We discussed that issue in the Discussion section, and in the MM section we wrote that the glue is recommended and provided by the manufacturer.
What was the time from sticking the strain gauges to testing? – All measurements were obtained earliest the next day after glueing
L 189: Why were these load values chosen? Why was this loading scheme adopted? Were 50, 100 and 150 N the values of the force acting on the compression pin? Chosen loads represent average chewing forces in implant overdenture subjects. The desired forces loaded overdentures (retained by mini-implants). When the desired force was reached, it was kept for 2 seconds. Fig 2 is added as a diagram.
These values are small considering the forces developed during occlusal occlusion.
The forces used are average forces in subjects with implant overdentures. Conventional denture average forces are lower, i.e. 30-40 N, while subjects with natural teeth or bridges have higher average forces. Added in MM and Discussion
The example of classic flexural load was showed at the figure 1. The reaction of the flexural system was calculated? The forces acting on the implants were different than those provided by the authors, this should be checked.
– we did not write that that forces were acting on implants?
We do not know, and we did not measure the extent of forces acting on implants. We mimicked the situation like circumstances in “real mouth”.
The (occlusal) force which loaded the denture is distributed to both implants and mucosa, depending on the retention system and the attachment used. We measured only periimplant strains elicited by forces transferred from dentures to implants eliciting strains in bone at the implant-bone interface. Loading presented in Fig 2 now.
Figure 1b also shows removable overdenture attached to mini-implants loaded in a downward direction. Places where SGs were bonded and the wires were not covered by a denture or artificial mucosa in order not to deform them. Strains on the bone as close as possible to the implant-bone interface were measured.
L184-190: The description is not clear to me, it should be illustrated with an appropriate diagram corresponding to the three load positions described.
Done, the new figure (NOW FIG. 2) is included (see below).
Fig.xy Schematic drawing of loads applied to mandibular overdenture retained by one, two, three or four Ti-Zr mini-implants; a. bilateral posterior loading; b. unilateral posterior loading; c. anterior loading
L 216-217: The figure 2 should be divided accordingly.
Now it is Fig 3. When it goes to print, it will not occupy so many pages, it can be reduced in print, I’d leave that to the Editor
Graphs do not need value precision up to 10^-2 (vertical axis), this should be changed. – Usually, all values are presented with 2 decimal places. I agree that microstrains are small values, if you insist, we can change that.
Units must be completed.
No supplementary provided, none of the Tables could be rated. – We sent 7 Supplementary tables
L 256-257: The figure 3 should be corrected according to the previous instructions.
Usually, all values are presented with 2 decimal places. I agree that microstrains are small values, if you insist, we can change that.
Discussion:
The discussion should be rewritten taking into account the above comments.
References:
Several literature items are older than 10 years and should be replaced with current ones. – done for most of the old references
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsBiomechanical Analysis of Ti-Zr Mini-Implants for Mandibular Overdenture Retention: In Vitro Study
This in vitro study investigates the biomechanical performance of Ti-Zr mini-implants (MDIs) in retaining mandibular overdentures (ODs) under different loading conditions. The research explores the influence of the number of inserted MDIs and loading forces on periimplant microstrains and strains in the posterior edentulous area.
Abstract:
Page 1 lines 35, 41, 44 and 46: the use of abbreviations in the abstract is not recommended, especially if they have not been defined (MDIs = Micro Dental Implants).
Introduction:
Page 1 line 58: This classification needs the citation from where it was taken. I assume the author is referring to the following classification
"Jung RE, et al. ITI Group 1 consensus report: the influence of implant length and design and medications on clinical and patient-reported outcomes. Clin Oral Implants Res. 2018 Oct;29 Suppl 16:69-77. doi: 10.1111/clr.13342. PMID: 30328189.”
Material and mehtos:
Authors must define specifically to which type of bone their model is equivalent (type I, II, III or IV).
Page 4, lines 196-197: The authors stated that: "The highest registered microstrains in each of the 15 repeated measurements were entered into the database." Why did they not use all the measurements obtained?
Page 198 line 200-201: Although it probably does not change the results, and that both tests are performed simultaneously in the SPSS program in the exploratory Tukey analysis. The Kolmogorov-Smirnov test is the standard goodness of fit test but Shapiro-Wilk test is more suitable when the sample size is relatively small (n < 50) or when there are outliers as the Kolmogorov-Smirnov is sensitive to outliers. Authors should perform the normality test appropriate for their sample size.
As a suggestion not to be answered: I would have liked to have a control group with standard implants (at least 2) to have a reference of the stress supported by the models.
Results:
Page9, line 229-230, page 10 lines 234-235 and 240-241: The authors state that "Unilateral forces elicited the highest microstrains in the right-side MDIs, followed by the left-side MDI". In the discussion they should explain why this effect occurs. Could it be due to an asymmetry in the models? See comments in discussion.
Discusion:
Page 13, line 325: the use of abbreviations “FEA” must be defined before first use (finite element analysis)
Page 14 line 336: Although it is specified in the discussion, the equivalent bone type should appear in the material and method.
Author Response
Dear reviewer,
I am grateful for the suggestions you gave us to improve our article. I hope we have met your expectations and I send comments in word file too .
Best regards,
Dario Puljic and team
This in vitro study investigates the biomechanical performance of Ti-Zr mini-implants (MDIs) in retaining mandibular overdentures (ODs) under different loading conditions. The research explores the influence of the number of inserted MDIs and loading forces on periimplant microstrains and strains in the posterior edentulous area.
Abstract:
Page 1 lines 35, 41, 44 and 46: the use of abbreviations in the abstract is not recommended, especially if they have not been defined (MDIs = Micro Dental Implants). corrected
Introduction:
Page 1 line 58: This classification needs the citation from where it was taken. I assume the author is referring to the following classification done, corrected
"Jung RE, et al. ITI Group 1 consensus report: the influence of implant length and design and medications on clinical and patient-reported outcomes. Clin Oral Implants Res. 2018 Oct;29 Suppl 16:69-77. doi: 10.1111/clr.13342. PMID: 30328189.”
Material and mehtos:
Authors must define specifically to which type of bone their model is equivalent (type I, II, III or IV). Done in MM 2.1
Page 4, lines 196-197: The authors stated that: "The highest registered microstrains in each of the 15 repeated measurements were entered into the database." Why did they not use all the measurements obtained? Because only highest strains can cause adverse bone reaction (> 3000 microstrains). We loaded dentures with average values of chewing forces in implant overdenture subjects, but we decided to pick-up highest strains during each repeated loading as forces of 1500 or 2000 > can have adverse effects when frequently repeated in cycles- . – added in discussion
Page 198 line 200-201: Although it probably does not change the results, and that both tests are performed simultaneously in the SPSS program in the exploratory Tukey analysis. The Kolmogorov-Smirnov test is the standard goodness of fit test but Shapiro-Wilk test is more suitable when the sample size is relatively small (n < 50) or when there are outliers as the Kolmogorov-Smirnov is sensitive to outliers. Authors should perform the normality test appropriate for their sample size. – We did it also with the Shapiro-Wilks W, which showed similar results.
As a suggestion not to be answered: I would have liked to have a control group with standard implants (at least 2) to have a reference of the stress supported by the models.
Such control group would not be appropriate, as there would not be a sufficient amount of peri-implant bone in same models for insertion of standard diameter implants, as we constructed the model by choosing a patient with a reduced bucco-lingual alveolar ridge width, appropriate only for insertion of small diameter implants (2.4 mm wide).
Results:
Page9, line 229-230, page 10 lines 234-235 and 240-241: The authors state that "Unilateral forces elicited the highest microstrains in the right-side MDIs, followed by the left-side MDI". In the discussion they should explain why this effect occurs. Could it be due to an asymmetry in the models? See comments in discussion. Done, explained by stronger retention of the attachments of the new Ti-Zr system, transferring more loads to implants (giving a denture more support) than the resilient O ring attachment system in Ti-6Al-4V mini-implants.
Discusion:
Page 13, line 325: the use of abbreviations “FEA” must be defined before first use (finite element analysis) done
Page 14 line 336: Although it is specified in the discussion, the equivalent bone type should appear in the material and method. done
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe present study is conducted with precision and offers intriguing perspectives in the field of implantology. The obtained results indicate that an increase in the number of Mini Dental Implants (MDIs) reduces the amount of microstrains around the implants, particularly in the posterior edentulous area. The findings highlight that microstrains are more pronounced with unilateral loads and under a force of 150 N in the two-MDI model.
Of particular interest is the observation that anterior loads with 50 and 100 N in the one-MDI model generate higher microstrains compared to posterior loads. Additionally, unilaterally applied loads induce higher strains than bilateral loads, especially on implants on the loaded side. In the posterior edentulous areas, the highest microstrains are recorded in the one- and two-MDI models.
Although none of the recorded microstrains seem to interfere with bone reparative mechanisms, caution and further investigation are recommended, especially in the one- and two-MDI models. Considering the significant results obtained, the publication of this study would be highly beneficial in contributing to knowledge and future developments in the field of implantology.
Comments on the Quality of English LanguageThe content of the English text is suitable for the journal and its readers.
Author Response
Dear reviewer,
Thank you for taking the time to review our article. I hope we met your expectations.
Best regards,
Dario Puljic and team
Reviewer 4 Report
Comments and Suggestions for Authors1. The present study may be regarded as a significant contribution to clinical practice, as mini-implants are getting more and more popular.
2. Statistics are very well presented.
3. Maybe authors should describe little more the limitations in the discussion.
Author Response
Dear reviewer,
Thank you for taking the time to review our article. I hope we met your expectations. We have taken your suggestion and written the limitations of our study in the discussion.
Best regards,
Dario Puljic and team
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThere are still some errors, the text should be read carefully.
In my opinion, none of the diagrams in Fig. 2 correspond to the photo in Fig. 1B.
I still think that the accuracy of the values in the charts should be reduced and appropriate units should be added.
I still believe that drawings should be appropriately divided according to specific analysis criteria.
I still don't have access to any Supplementary tables
It is still not explained why such values of loading forces were used.
Author Response
Dear reviewer,
First of all, I want to thank you for taking the time to review our article. I hope we were able to adopt the suggestions you gave us to improve our article.
There are still some errors, the text should be read carefully. We tried to correct them. We are not native English language speakers, but I hope we managed to improve the manuscript.
In my opinion, none of the diagrams in Fig. 2 correspond to the photo in Fig. 1B. We changed again diagrams (Fig.2) and Fig. 1B. We now changed the photo (1B) of the 2-MDI model supporting the OD which was loaded through forces applied on the metal plate, we hope it is better now. However, only vestibular SGs can be seen in Fig.1B and wires from the edentulous area, as well as wires from the oral SGs (they cannot be seen because the overdenture is attached). We hope it is clearer now. In Fig 2 we re-draw the diagram and included the model with 4 MDIs. (vestibular SGs and edentulous area SGs were drawn, oral SGs cannot be seen as they are positioned on the oral periimplant bone behind implants). Loadings of a metal plate which lies on the artificial teeth of mandibular overdentures is drawn.
I still think that the accuracy of the values in the charts should be reduced and appropriate units should be added. Now we omitted decimal places and we wrote that the units are microstrains
I still believe that drawings should be appropriately divided according to specific analysis criteria. Done, we now included separate Figuress for each : one, two, three or four MDI OD.
I still don't have access to any Supplementary tables – We always also uploaded the Supplementary Tables. The manuscript with supplementary figures and tables is uploaded as a zipped file. I believe everything should be in the same document. The editor may need to be contacted to ensure visibility of any additional files.
- About loading forces – they were selected because they represent mean chewing forces for subjects with implant supported overdentures. Complete denture subjects have average forces 30-50 N, Implant OD subjects from 50 to 200 N, and subjects with natural teeth have higher forces - (we explained in the discussion): The extent of loading forces [43] applied in this study represent average chewing forces in subjects with implant supported ODs [44]. Chewing forces are lower in conventional complete denture subjects and vary from 30 to 50 N [44], but are much higher in subjects with their own teeth or fixed partial dentures [42].
Round 3
Reviewer 1 Report
Comments and Suggestions for AuthorsI appreciate your work in improving the manuscript. Below are some notes:
Line 131: "All models of the mandible were equivalent to the type II bone density" What does this mean?
Line 182: The description of Fig. 1A should be unified, it should be 1a.
Editing of figure headings and captions (Fig 3) is required.
Fig. 3a-Fif.3d - should be renumbered consecutively.
Lines 285-286, 297, and 379: ? Remove unnecessary lines.
Author Response
Dear reviewer,
I would like to thank you for the pointed out omissions, and I hope that we will find a common solution so that our article is satisfactory.
Line 131: "All models of the mandible were equivalent to the type II bone density" What does this mean? The material from which the mandible models are made is similar in its mechanical characteristics to D2 density bone.
Line 182: The description of Fig. 1A should be unified, it should be 1a. Done
Editing of figure headings and captions (Fig 3) is required. Fig. 3a-Fif.3d - should be renumbered consecutively. Figure 3 has its own headings and they talk about peri-implant microstrains, and about the number of implants and their locations. Also, Figure 3 is divided into Figures 3 a,b,c,d for easier visibility, and again to follow a logical sequence. We did it in the same way with Figure 4. Did you mean that Figures 3 a, b, c, d become separate Figures 4, 5, 6, etc.?
Lines 285-286, 297, and 379: ? Remove unnecessary lines. Done.
Best regards,
Dario Puljic and team
