The Application of a 3-Dimensional Printing Technique in Refining the Orthodontic Trans-Palatal Arch

Round 1

Reviewer 1 Report

Dear Authors,

Congratulations on your work!

Your paper presents an interesting approach regarding TPA manufacturing, as a series of clinical cases.

I would add some details to each clinical case: the specific method used for creating the digital models, the time of wearing the TPA, eventually unwanted events (TPA loosening, breakage, patient discomfort).

Author Response

Thank you for your suggestions!

Although, we have introduced three methods used for creating the digital models, all the digital models in the cases were created by scanning the casts. We have added the specific method used for creating the digital model of every case in revised manuscript.

The wearing time of 3D TPA is based on clinical needs, similar to traditional TPA. However, the 3D TPA may be better than traditional TPA in terms of intruding molars. To ensure good retention, traditional TPAs are sometimes inserted close to the gingival margin or deep into the gingival sulcus. There may be resistance from the gingiva during the intruding process. To avoid the resistance from gingiva, the adhesive plate of 3D TPA is designed more than 1.5 mm from the gingival margin. Besides, the band of traditional TPA must encompass four surface, including the buccal surface, the lingual surface and two proximal surfaces. There may be frictional resistance between the band and proximal surfaces. In contrast, the adhesive plate of 3D TPA is only attached to one surface of a tooth, which may eliminate the frictional resistance. Therefore, we speculate that the 3D TPA pose higher efficiency than traditional TPA regarding intruding molars.

Usually, traditional TPA is composed of metal bands and bars. The inner surface of metal band is smooth. To ensure good retention, the band of traditional TPA must encompass four surface, including the buccal surface, the lingual surface and two proximal surfaces. In contrast, the adhesive plate of 3D TPA is only attached to one surface of a tooth. It’s hard not to doubt the adhesive strength of 3D TPA. However, the adhesive surface of 3D TPA was modified with the undercut to enhance the adhesive strength. Indeed, there was possibility of loosening of previous 3D TPAs. After a period of clinical observation, we found that occlusal interference was the main factor leading to loosening of 3D TPAs. Therefore, care had been taken to avoid occlusal interference in the present design. In the cases of this article, no loosening of 3D TPA has been observed up till now. Surely, a long-term observation of a large number of cases is necessary to verify the adhesive strength of 3D TPA.

No breakage of 3D TPA has been observed up till now. Theoretically, the 3D TPA may show better breakage resistance than traditional TPA. The 3D TPA is integrally printed, but the traditional TPA is made by welding. Sometime, loose weld of traditional TPA could be observed in clinic.

To ensure good retention, traditional TPAs are sometimes inserted close to the gingival margin or deep into the gingival sulcus, which might be harmful to gingival health (Supplementary figure 1A). In contrast, 3D TPA can be inserted at least 1.5 mm away from the gingiva, which might make it easier for clinicians to thoroughly remove excess adhesive when bonding the 3D TPA; it therefore represents a more hygienic alternative to traditional TPAs (Supplementary figure 1B). Additionally, traditional TPAs encompass four surfaces, including the buccal surface, the lingual surface, and two proximal surfaces, which can lead to gaps between teeth after debonding. As such, patients might sometimes complain of food impactions after removing their traditional TPAs. In contrast, 3D TPA only attaches to the lingual surface and not the proximal surface, which might reduce the possibility of proximal gaps and food impactions. Overall, in theory, 3D TPA has the potential to reduce periodontal complications and enhance patient comfort. However, further clinical trials should be conducted, focusing on periodontal indices such as the gingival index and sulcus bleeding index, and on patient feelings.

The aim of this article is to tentatively explore the feasibility of manufacturing TPAs with 3D technology and preliminarily discuss some brief cases in which the 3D TPAs were used. The main manufacturing process has been introduced in this article and the cases revealed the potential advantages of 3D TPAs. We are conducting some experiments to test the bonding strength, as well as clinical trials to observe the periodontal health, TPA loosening, patient satisfaction and doctor acceptance. These experiments and trails are ongoing, but not finished. In our next papers, we will report the corresponding results.

Thank you again, your suggestions are really helpful for the quality of the manuscript and constructive to our future studies.

Reviewer 2 Report

Dear Colleagues,

Thank you for sharing your work regarding the 3D printing and clinical usages of TPA. However, the article language must be conducted via a native english speaker because of extensive critical errors. Several cases presentation is considered a negative point because you neither explain in details how TPA was constructed nor the clinical outcome and comparison between conventional and digital TPA. You only presented and illustrated that it is possible to do it. However, the authors didn't implement the quality required to ensure that such methodology is a major advantage. Finally, an active language (ex: we) must be avoided. Therfore, I strongly recommend impressive reconsideration of the main aims ( how to design TPA using CAD/CAM technology? or the precision of CAD/CAM produced TPA in comparsion to conventional TPA? or Clinical effectivness of CAD/CAM produced TPA? ). I also guess that TPA was not printed but was laser melted using SLM. It would also preferred to recieve the raw data. 

Best regards 

Author Response

Thank you for your careful comments on our manuscript.

The writing of our manuscript has been edited by Multidisciplinary Digital Publishing Institute (DMPI). The editing certificate is provided as a supplementary file (see supplementary file 1).

More details of designing and manufacturing 3D TPAs have been added in materials and methods. The corrections were marked in red in revised manuscript.

The 3D TPA may be better than traditional TPA in terms of intruding molars.

To ensure good retention, traditional TPAs are sometimes inserted close to the gingival margin or deep into the gingival sulcus. There may be resistance from the gingiva during the intruding process. To avoid the resistance from gingiva, the adhesive plate of 3D TPA is designed more than 1.5 mm from the gingival margin. Besides, the band of traditional TPA must encompass four surface, including the buccal surface, the lingual surface and two proximal surfaces. There may be frictional resistance between the band and proximal surfaces. In contrast, the adhesive plate of 3D TPA is only attached to one surface of a tooth, which may eliminate the frictional resistance. Therefore, we speculate that the 3D TPA pose higher efficiency than traditional TPA regarding intruding molars. Although reliable clinical trials have not been finished, some clinical effects of 3D TPAs have been observed. In case 4, the TPA has been changed during the process of molar intrusion. Because the effect of molar intruding was so good, an impression of the bar could be observed on the gingival (Supplementary figure 2B). We removed the original TPA (supplementary figure 2A) and made a new one (Supplementary figure 2C) that was further away from gingival.

3D printing is a Computer-aided manufacture (CAM) technique; it is a method that uses 3D Computer-aided design (CAD) datasets to produce 3D physical objects by the addition of material layers. As a kind of 3D printing, selective laser melting (SLM) is usually used to print metal objects. To make the methods of the manuscript more specific, we have added this information in revised manuscript.

The aim of this article is to tentatively explore the feasibility of manufacturing TPAs with 3D technology and preliminarily discuss some brief cases in which the 3D TPAs were used. The main manufacturing process has been introduced in this article and the cases revealed the potential advantages of 3D TPAs. We are conducting some experiments to test the bonding strength, as well as clinical trials to observe the periodontal health, TPA loosening, patient satisfaction and doctor acceptance. These experiments and trails are ongoing, but not finished. In our next papers, we will report the corresponding results. According to your suggestion, we will further focus on the comparisons between 3D TPAs and traditional TPAs regarding the precision and clinical effectiveness.

Thank you again, your suggestions are really helpful for the quality of the manuscript and constructive to our future studies.

Reviewer 3 Report

The topic of this paper is timely and relevant, and of great interest to the clinician.  I enjoyed reading the paper and it was easy to follow.  Numerous sometimes nonsensical compositional errors generally do not deflect from the main thread but heavy editing will be necessary.  The title is misleading - this is not a pilot study but simply a case series report.  There is no hypothesis to test here.  The abstract is too simplified and typifies the main problems with the article which is a lack of detail in both the technical aspects of the metal printing and the clinical problems and limitations of the printed TPA. 

The main issues are as follows:

1.       What type of scanners were used?  Were STL files generated directly?  Describe in more detail the “dedicated high performance workstations.”   The claim is made that this system is feasible but it is not if the workstations and metal printers need maintenance, calibration, personnel, etc.

2.       Describe the digital workflow in more detail – each step from intraoral scan to storing the image to uploading into the 3D environment to design phase, etc etc  - more details and please, product names and manufacturers.

3.       Was each TPA custom designed from scratch or was it designed once then modified or was a generic TPA downloaded from the metaverse?

4.       Need better explanation of design of the bondable metal surface and recommended bonding agent.  A couple of figures showing what is written under “Computer -aided design and 3D printing” would be immensely useful.

5.        What is meant by polishing – traditional as done by a human or is this something else?

6.       NO DESCRIPTION OF 3D METAL PRINTING PROCESS!  Is this done in house (not likely)?  Cost? Composition of the metal?  Type of metal printing?  Toxicity of the metal if any?  Properties – compare with trad stainless steel.

7.       The cases are good.  Everyone will really like the heart shaped TPA – nice!  Probably don’t really need clinical photos but ok if they don’t take up too much room.  What bonding agent was used?  Authors must comment on failure rate, ease of removing the appliance, and corrosion if any.  Some clinicians would comment on the circle design – more commonly a “coffin spring” loop is used that allows some adjustments to be made, especially in the transverse dimension.  Is the printed TPA too brittle to adjust?

8.       It is not clear at what step in the fabrication flow were the acrylic buttons added – were they 3d printed or manually added?

9.       In case 4 was the TPA designed with a precise amount of intrusion of the molars in mind? In case 5 the “thorns” do not appear in Figure 6C.  Were they soldered on later by a lab tech?  Can we assume then that he sintered metal can be soldered? In Figure 8 the arm is part of the TPA – is it the same for Case 6 extension arm?  Same question again – can the printed arms be adjusted with traditional ortho instruments.

10.   The Discussion is a good summary.   The claim that bond strength is better in the metal printed TPA is not substantiated.   There are problems with intraoral scanning if there is too much saliva in the embrasures.  Digital workflow as stated in the discussion takes a lot of time and resources before it starts to show ROI.   The main advantage in today’s world is the huge advantage digital workflow has in infection control.

Summary -  should also comment that in most contemporary practices digital workflow without plaster is commonplace and an additional option for clinicians is a hand made appliance fabricated off a printed model from an uploaded scan.  The metal printed TPA replaces the craftsman with a technician who must process the direct printed device. 

The article is publishable but as stated above a significant amount of exact information must be added before approval.

Comments for author File: Comments.pdf

Author Response

Response:

Thank you for your suggestions.

The title was modified as “The application of 3-dimentional printing technique in refining orthodontic trans-palatal arch”. The abstract was revised with more details regarding technical aspects and limitations of the printed TPA.

The main issues are as follows:

1. What type of scanners were used?  Were STL files generated directly? Describe in more detail the “dedicated high performance workstations.” The claim is made that this system is feasible but it is not if the workstations and metal printers need maintenance, calibration, personnel, etc.

Response: The model and PVS impression scanner used in the mechanic center was SHINING 3D scanner (SHINING 3D, China), the scan data was automatically converted to STL format by the scanner. The type of oral scanner used in clinic depends on the dental department. There are many kinds of oral scanners on the market form different companies, such as 3shape, Sirona, 3M and so on. Some oral scanners can’t covert the scan data to STL format automatically. For example, only a specialized software from 3shape company can convert the scan data from 3shape scanner to STL format. Dedicated high performance workstations (Supplementary figure 3) equipped with image processing software (3-matic STL software (version 10.2; Materialise, Leuven, Belgium)) and Concept Laser M lab (Concept Laser, Germany) were used for appliance designing and manufacturing.

2. Describe the digital workflow in more detail – each step from intraoral scan to storing the image to uploading into the 3D environment to design phase, etc etc  - more details and please, product names and manufacturers.

Response: Thank you for your suggestion. We have added more detail of the design in revised manuscript.

3. Was each TPA custom designed from scratch or was it designed once then modified or was a generic TPA downloaded from the metaverse?

Response: Every appliance was individually designed from scratch. Thank you for your suggestion. We are considering establishing some digital templates, so as to improve the designing efficiency.

4. Need better explanation of design of the bondable metal surface and recommended bonding agent.  A couple of figures showing what is written under “Computer -aided design and 3D printing” would be immensely useful.

Response: To be honest, the data of the adhesive surface is an orthodontic bracket data provided by Jing Mei dental center (Chongqing, China). A clear picture of adhesive surface is shown as supplementary figure 4. The recommended bonding agent is reinforced glass ionomer (GC Fuji Ortho LC, GC corporation, Japan).

5. What is meant by polishing – traditional as done by a human or is this something else?

Response: To make the surface smoother, a polishing is necessary. The polishing is traditional as done by human.

6. NO DESCRIPTION OF 3D METAL PRINTING PROCESS!  Is this done in house (not likely)?  Cost? Composition of the metal?  Type of metal printing?  Toxicity of the metal if any?  Properties – compare with trad stainless steel.

Response: Design instructions were sent to Concept Laser M lab (Concept Laser, Germany) for fabrication. With 3D printing, the machine read in data from a CAD drawing and lay down successive layers of metal material, and in this way built up the model from a series of cross sections. These layers, which corresponded to the virtual cross section from the CAD model joined together, created the final shape. The composition of the metal is Titanium alloy powder (Dentaurum, Germany). The type of metal printing is selective laser melting (SLM). The printed TPA is more rigid and less elastic than traditional TPA.

7. The cases are good.  Everyone will really like the heart shaped TPA – nice!  Probably don’t really need clinical photos but ok if they don’t take up too much room.  What bonding agent was used?  Authors must comment on failure rate, ease of removing the appliance, and corrosion if any.  Some clinicians would comment on the circle design – more commonly a “coffin spring” loop is used that allows some adjustments to be made, especially in the transverse dimension.  Is the printed TPA too brittle to adjust?

Response:

The printed TPA were bonded by reinforced glass ionomer (GC Fuji Ortho LC, GC corporation, Japan). We have added this information in revised manuscript.

The aim of this article is to tentatively explore the feasibility of manufacturing TPAs with 3D technology and preliminarily discuss some brief cases in which the 3D TPAs were used. The main manufacturing process has been introduced in this article and the cases revealed the potential advantages of 3D TPAs. We are conducting some experiments to test the bonding strength, as well as clinical trials to observe the periodontal health, TPA loosening, patient satisfaction and doctor acceptance. These experiments and trails are ongoing, but not finished. In our next papers, we will report the corresponding results. According to your suggestion, we will further focus on the failure rate and corrosion.

Your consideration about adhesion and debonding is very professional and comprehensive. In fact, the appliance could be removed normally with traditional orthodontic instrument. In order to improve clinical efficiency and reduce possible periodontal destruction by debonding force, we have tried some special designs, such as adhesive plate with a raised margin (Supplementary figure 5). Simultaneously, some mechanic experiments on debonding of the appliance are underway. We hope to design an adhesive plate that would realize firmly adhesion, be easy debonding and ensure periodontal health.

To be honest, the printed TPA could not bear some adjustment. However, the purpose of the appliance was taken into full consideration at the beginning of the design. In this case, the TPA was used for transverse maintaining of dental arch, anchorage control and vertical depression, rather than adjustment of dental arch. If an arch expansion is needed, an expansion screw with printed adhesive plates (China patent No. ZL 2017 2 0583675.2) could be applied as shown in supplementary figure 6. Altogether, the appliance is designed in advance according to the clinical needs, but not used for possible adjustment.

8. It is not clear at what step in the fabrication flow were the acrylic buttons added – were they 3d printed or manually added?

Response: The acrylic buttons was manually added but not printed. We have added this step in revised manuscript.

9. In case 4 was the TPA designed with a precise amount of intrusion of the molars in mind? In case 5 the “thorns” do not appear in Figure 6C.  Were they soldered on later by a lab tech?  Can we assume then that he sintered metal can be soldered? In Figure 8 the arm is part of the TPA – is it the same for Case 6 extension arm?  Same question again – can the printed arms be adjusted with traditional ortho instruments.

Response:

In case 4, both first and second molars need to be intruded to correct the open bite. The TPA was mainly used for transverse maintaining of dental arch, so that the molars would not incline buccally during the process of intrusion by mini-implants. Besides, the circle of the TPA is usually 8-10 mm from the roof of the palate, so that the tongue could exert pressing action, which contributed to the intrusion of molars. It’s not an isolated case, we are tracing other similar cases. Here, we’d like to share another case in which the TPA was used to assist correcting open bite (Supplementary figure 7). Altogether, the TPA was used as a maintaining appliance, but not an active one. The amount of intrusion of the molars depended on the improvement of the open bite, but was not predesigned precisely.

 The thorns in case 5 were soldered and the lateral arms of TPA in case 6 and case 7 were printed. Soldered thorns could bear some adjustment, while the printed lateral arms couldn’t bear any adjustment. In fact, the affiliated apparatus of 3D TPA could be printed or soldered according to the clinical needs. In case 5, the clinician wanted to adjust the thorns to restricted the tongue of the patient exactly. So, the thorns were soldered. In case 6 and case 7, the change of the traction direction was not necessary, so the lateral arms and TPA were printed integrally. If the traction direction needs adjustment, the lateral arms could also be soldered.

10. The Discussion is a good summary.   The claim that bond strength is better in the metal printed TPA is not substantiated.  There are problems with intraoral scanning if there is too much saliva in the embrasures.  Digital workflow as stated in the discussion takes a lot of time and resources before it starts to show ROI.   The main advantage in today’s world is the huge advantage digital workflow has in infection control.

Response:

Usually, traditional TPA is composed of metal bands and bars. The inner surface of metal band is smooth. To ensure good retention, the band of traditional TPA must encompass four surface, including the buccal surface, the lingual surface and two proximal surfaces. In contrast, the adhesive plate of 3D TPA is only attached to one surface of a tooth. It’s hard not to doubt the adhesive strength of 3D TPA. However, the adhesive surface of 3D TPA was modified with the undercut to enhance the adhesive strength. Indeed, there was possibility of loosening of previous 3D TPAs. After a period of clinical observation, we found that occlusal interference was the main factor leading to loosening of 3D TPAs. Therefore, care had been taken to avoid occlusal interference in the present design. In the cases of this article, no loosening of 3D TPA has been observed up till now. Surely, a long-term observation of a large number of cases is necessary to verify the adhesive strength of 3D TPA. Indeed, the statement in original manuscript is arbitrary because of no substantiation of corresponding experiments. We have revised the manuscript in the abstract, discussion and conclusion to make the statement moderate.

Digital models can be created by different methods depending on the conditions of clinics and the preferences of doctors or patients. If there is too much saliva to scan intraorally, casts or PVS impressions could be scanned to create digital models.

Reviewer 4 Report

This is a case series and not a clinical study, not even a pilot one. The authors just report a few cases where they placed TPAs and they do not test any relevant outcome. Furthermore, there are serious problems with reporting. Please find some examples below:

1. The manuscript needs careful editing by a native English language speaker. For example, see Introduction: “However, there are still some traditional orthodontic appliances without digitalized,…”.

2. Introduction, 2^nd Par.: “The use of TPAs has become a routine part of the treatment protocol in both the permanent and late mixed dentitions, with a frequency of use well above 90%[15].” The authors imply that in 90% of orthodontically treated cases a TPA is used. This is by no means the case and it is not supported by the cited reference. Please soften this statement.

3. “…the aim of this pilot study was to develop a prototype of 3D TPAs, and thus improve the manufacturing and effects of TPAs, as well as patient satisfaction and health.” The part of the sentence starting from the effects and on is not relevant and was not tested in the present study. Please remove it and avoid similar overstatements throughout the manuscript.

4. Discussion: “Since the 3D TPA has advantages over traditional TPA in bonding strength, patients’ health and comforts, work flow and design flexibility, we recommend the use of 3D TPA instead of traditional TPA.” These and many other arbitrary statements are reported throughout the manuscript, but are only opinions of the authors not based on any data.

5. A major disadvantage of this 3D printed TPA is that it is not adjustable throughout the treatment as the traditional one. This is not mentioned in the manuscript and there is a clear bias throughout the manuscript favouring the 3D printed TPA. The authors should try to adopt an objective view and report all discussed appliances accordingly.

Author Response

Thank you for your insightful comments concerning our manuscript. We have revised our manuscript from the title to the conclusion according to your suggestions.

The aim of this article is to tentatively explore the feasibility of manufacturing TPAs with 3D technology and preliminarily discuss some brief cases in which the 3D TPAs were used. The main manufacturing process has been introduced in this article and the cases revealed the potential advantages of 3D TPAs. We are conducting some experiments to test the bonding strength, as well as clinical trials to observe the periodontal health, TPA loosening, patient satisfaction and doctor acceptance. These experiments and trails are ongoing, but not finished. In our next papers, we will report the corresponding results.  

Comment 1. The manuscript needs careful editing by a native English language speaker. For example, see Introduction: “However, there are still some traditional orthodontic appliances without digitalized,…”.

Response: The writing of our manuscript has been edited by Multidisciplinary Digital Publishing Institute (DMPI). The editing certificate is provided as a supplementary file (see supplementary file 1).

Comment 2. Introduction, 2^nd Par.: “The use of TPAs has become a routine part of the treatment protocol in both the permanent and late mixed dentitions, with a frequency of use well above 90%[15].” The authors imply that in 90% of orthodontically treated cases a TPA is used. This is by no means the case and it is not supported by the cited reference. Please soften this statement.

Response: Thank you for your careful inspection on our manuscript. This reference is from an article titled “Comparison of the Effect of Transpalatal Arch on Periodontal Stress and Displacement of Molars When Subjected to Orthodontic Forces. A Finite Element Analysis”. We traced its references again and found some misleadings. We have revised this statement and changed the reference. At the same time, we inspected all references in our manuscript to ensure no mistakes.

3. “…the aim of this pilot study was to develop a prototype of 3D TPAs, and thus improve the manufacturing and effects of TPAs, as well as patient satisfaction and health.” The part of the sentence starting from the effects and on is not relevant and was not tested in the present study. Please remove it and avoid similar overstatements throughout the manuscript.

Response:

Thank you for your suggestions. We have removed this sentence and rewritten the aim of this article.

4. Discussion: “Since the 3D TPA has advantages over traditional TPA in bonding strength, patients’ health and comforts, work flow and design flexibility, we recommend the use of 3D TPA instead of traditional TPA.” These and many other arbitrary statements are reported throughout the manuscript, but are only opinions of the authors not based on any data.

Response:

Thank you for your suggestion.

We have revised the statements throughout the manuscript. The new statements would be more moderate.

5. A major disadvantage of this 3D printed TPA is that it is not adjustable throughout the treatment as the traditional one. This is not mentioned in the manuscript and there is a clear bias throughout the manuscript favouring the 3D printed TPA. The authors should try to adopt an objective view and report all discussed appliances accordingly.

Response: Thank you for your suggestion. To be honest, the printed TPA could not bear some adjustment. However, the purpose of the appliance was taken into full consideration at the beginning of the design. In this case, the TPA was used for transverse maintaining of dental arch, anchorage control and vertical depression, rather than adjustment of dental arch. If an arch expansion is needed, an expansion screw with printed adhesive plates (China patent No. ZL 2017 2 0583675.2) could be applied as shown in supplementary figure 6. Altogether, the appliance is designed in advance according to the clinical needs, but not used for possible adjustment. However, we admit that our statements are a little arbitrary and biased. We have revised them throughout the manuscript as you suggested. Thank you again, your careful inspection is really helpful to improve the quality of our manuscript.

Round 2

Reviewer 2 Report

Dear authors,

Thank you for the corrections and changes. The article is well presented in its current form. As a reference, a future detailed case study on the impact of CAD/CAM technology in orthodontics could be very valuable instead of briefly explaining several cases. Thank you.   

Best regards

Author Response

Thank you for your suggestions. In future reports, we will  present detailed cases and well-designed clinical studies.

Reviewer 4 Report

The study has been considerably improved after the revision. Please revise the text as suggested below to further improve your reporting:

1. Abstract, Last two sentences: “The results showed that the 3D TPA was very concise and might be more cleansable. The 3D TPA could be designed as diverse types based on clinical needs. The application of 3D TPA could be promoted if possible. Surely, further extensive experiments and clinical trials are necessary to verify the advantages of 3D TPA.”

Please revise as: The presented clinical cases demonstrated that the 3D TPA was a simple, convenient appliance for the patient and the doctor, and thus, might be more cleansable. The 3D TPA could be designed in different types based on the clinical needs of each case. The application of 3D TPA could be expanded, but clinical trials are necessary to verify the advantages reported here.

2. Conclusions: “The use of 3D technology has the potential to make the design and manufacturing of TPAs more simple, faster, and more accurate. The 3D TPA might have the benefits of enhanced adhesive strength, improved periodontal health, and a more pleasant experience for the patient. Therefore, the application of 3D TPA could be promoted if possible. Surely, it is recommended that the clinicians thoroughly consider the cost and the benefits of this method. Further extensive experiments and clinical trials are necessary to verify the advantages of 3D TPA.”

Please revise as: The use of 3D technology has the potential to make the design and manufacturing of TPAs simpler, faster, and more accurate. The 3D TPA might have the benefits of enhanced adhesive strength, improved periodontal health, and be more convenient for the patient. Therefore, the application of 3D TPA could be expanded, despite the increased associated costs, but clinical trials are necessary to verify the advantages reported here.

Author Response

Thank you for your suggestions. We have revised the abstract and conclusion as you suggested.