Milling Versus Printing: The Effect of Fabrication Technique on the Trueness and Fitness of Fabricated Crowns (A Comparative In Vitro Study)

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

It is very interesting the idea of comparing the two manufacturing techniques by using the same material and clinical parameters (fitness and trueness of the restorations)

The introduction is quite explanatory, but the authors must should explain in more detail how they were led to the proposed protocol. They have to clarify why and they designed their research protocol. There is only one small paragraph about it (#60-65). The parameters are measurable so they have to state the clear null hypothesis of the study.

More information about the materials that were used must be performed, maybe in a table (detailed composition, lot numbers etc)

In tables 1 and 2 it would be better if the caption was uniform and from below.

My major concern is in the method that was used, if I understood it correctly. Every crown was performed and checked on the tooth that was scanned and produced the corresponding scans. Every measurement was performed on the corresponding tooth. In descriptive statistics were included all values. But the ten teeth are different. How did they check the internal accuracy between teeth? We can compare crowns in each tooth but we can’t compare crowns between different teeth. This could happen if the internal accuracy (especially trueness) had been measured and determined. If something like this has happened, it should be reported and explained. If I didn’t understand properly, the authors have to clear how the managed this point, because it is crucial for the proper interpretation of the results. In my opinion, there should be one master model tooth and its corresponding STL file, the same for all measurements, and all parameters should be examined with this master reference specimen. Then we can compare horizontally techniques. Unless, as I mentioned above, if this check has been done.

Another point is how many times did they scan each tooth and crowns? Did they calculate the internal accuracy of this measurement? How did they decide the ±10μm value? Arbitrarily?

This point, is even more important because during the work flow of the experiment, there are some manual processes that include non-standardizable component, as the authors mention (#368, 369)  

The authors mention that «# 445, 446 Unlike the milled group, most of the 3D-printed crowns exhibited statistically significant differences for both internal and marginal adaptation» and give some explanations. Did they calculate this difference between the crowns of the same tooth, so their explanations are possible or they included all crowns from all teeth, so I think that there is an interpretation problem in this point?

In the discussion section must be stated if the null hypothesis is accepted or not.

It is very interesting from a clinical point of view the observation and reference of «the inverse relation between trueness and both internal and marginal fitness of the fabricated crowns» (#408) but needs clearer (in my opinion) data and evidence.

Author Response

Reviewer 1

 

Dear Reviewer,

We would like to thank you for your constructive and thoughtful comments regarding our manuscript titled:
“[Milling Versus Printing: The Effect of Fabrication Technique on The Trueness and Fitness of the Fabricated Crowns (A Comparative In Vitro Study)]” (Manuscript ID: [prosthesis-3789439]).

We have carefully considered all suggestions and revised the manuscript accordingly. Below, we provide a point-by-point response to each comment. All changes have been highlighted in the revised manuscript for your convenience.

 

Comment 1: The introduction is quite explanatory, but the authors must should explain in more detail how they were led to the proposed protocol. They have to clarify why and they designed their research protocol. There is only one small paragraph about it (#60-65).

Response: Thank you for this observation. In response, we have revised the last two section to be more clearly present the rationale that led to the development of our research protocol. Additional explanation has been added to justify the need for a standardized comparison across both fabrication techniques.

We accordingly revised the manuscript to emphasize this comment; this revision can be found on page 2, Paragraph 4 and 5, lines 60-71.

Modification to Manuscript: Although previous studies have compared the trueness and fitness of restorations fabricated by subtractive and additive techniques using hybrid ceramic materials [15,22–25], the findings of these studies are confounded by the use of chemically different materials in each group. Even when categorized similarly, these materials differ significantly in their filler content, polymer matrix, and degree of polymerization, all of which might had an influence on the final outcomes. Consequently, the true influence of the fabrication method remains unclear, as material-related variables could not be controlled.

Therefore, the present study, which may be the first one, aimed to provide a controlled and more direct comparison of these two manufacturing technologies and evaluate their real effect on the trueness and fitness of crowns fabricated by using the same printable material for both 3D printing of crowns and fabrication of CAM blocks for subsequent milling, ensuring that the material composition remained constant across both workflows.

 

 

Comment 2: The parameters are measurable so they have to state the clear null hypothesis of the study.

Response: We appreciate this suggestion; the null hypothesis has now been stated at the end of the Introduction section.

This revision can be found on page 2, Paragraph 6, lines 72-74.

Modification to Manuscript: The proposed null hypothesis was that there would be no statistically significant differences in the trueness, internal and marginal adaptation between the additive and subtractive manufacturing technique.

 

 

Comment 3: More information about the materials that were used must be performed, maybe in a table (detailed composition, lot numbers etc).

Response: We agree and have added a new Table (Table 1) in the Materials and Methods section containing a summary of the manufacturer-reported properties with references.

This revision can be found on page 5, line 159.

 

Modification to Manuscript:

 

 

 

 

Table 1. The chemical compositions, physical and mechanical properties of the three printing materials used in this study.

Properties	Varseosmile Crown plus (VS)	Ceramic crown (CC)	P-crown V2 ceramic (PC)
Ceramic content	Inorganic fillers are 30 – 50 % by mass.	More than 50% by mass.	65% nano ceramic rate.
Chemical composition	Esterification products of 4.4‘-isopropylidiphenol, ethoxylated and 2-methylprop-2enoic acid. Silanized dental glass, methyl benzoylformate, diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide.	Oligomers (20% - 60%), Monomers (20%-50%), Photoinitiators (0.1%-10%), Additives (10%-60%).   The specific chemical identity is withheld because it is trade secret information of SprintRay.	Polymer matrix and Inorganic fillers.   The specific chemical identity is withheld because it is trade secret information of Senertek.
Flexural Strength	116 – 150 MPa	150±25 MPa	410.00 MPa
Flexural Modulus	4,090 MPa	7,800 ± 500 MPa	> 9500 MPa
Hardness	≥ 90 Shore D	≥ 90 Shore D	≥ 95 Shore D
Water Solubility	< 1 µg/mm3	2.16 ± 1.30 µg/mm3	<0.09 µg/mm3
Water sorption	< 12 µg/mm3	17.35 ± 2.56 µg/mm3	<1.2 µg/mm3
Viscosity	2,500 – 6,000 mPa*s	2,500–6,000 mPa*s at 30°C	~3500 cps
LOT number	600721	SRI-0202086	SNR202300030

 

 

Comment 4: In tables 1 and 2 it would be better if the caption was uniform and from below.

Response: We appreciate the reviewer’s suggestion regarding table formatting, letters were used to show the statistical significance. Uppercase letters for comparisons among rows, while lowercase letters for comparisons among columns. Different letters denoting significant difference.

 

Comment 5: My major concern is in the method that was used, if I understood it correctly. Every crown was performed and checked on the tooth that was scanned and produced the corresponding scans. Every measurement was performed on the corresponding tooth. In descriptive statistics were included all values. But the ten teeth are different. How did they check the internal accuracy between teeth? We can compare crowns in each tooth but we can’t compare crowns between different teeth. This could happen if the internal accuracy (especially trueness) had been measured and determined. If something like this has happened, it should be reported and explained. If I didn’t understand properly, the authors have to clear how the managed this point, because it is crucial for the proper interpretation of the results. In my opinion, there should be one master model tooth and its corresponding STL file, the same for all measurements, and all parameters should be examined with this master reference specimen. Then we can compare horizontally techniques. Unless, as I mentioned above, if this check has been done.

Response: We are grateful to the reviewer for highlighting these critical considerations, which provided an opportunity to elaborate on our methodological approach.

In our study, ten different maxillary first premolars were prepared to represent a broader range of clinical scenarios. For each prepared tooth, six crowns were fabricated (three via 3D printing using the three mentioned materials, and three via milling the produced blocks manufactured from these same printable materials). All six crowns shared the same abutment and CAD design, ensuring a high level of standardization, with the fabrication technique being the only variable.

Trueness was assessed by comparing the STL scan file of the intaglio surface of each crown to its corresponding STL design file (so for example: the 6 crowns for sample number one shared the same STL design file), allowing us to evaluate how accurately each manufacturing method reproduced its intended geometry. This approach aligns with the aim of this study to evaluate trueness rather than precision; which concerned about evaluating the reproducibility of multiple crowns manufactured using the same technique. Therefore, using one master model was not appropriate.

For internal and marginal fit evaluation, each crown was seated on its corresponding abutment, then the measurements were done between the two STL file for each crown (with and without the silicone) to calculate the respective gaps.

We hope this explanation clarifies the rationale behind our methodology, and we remain available to address any further concerns.

 

Comment 6: how many times did they scan each tooth and crowns? Did they calculate the internal accuracy of this measurement? How did they decide the ±10μm value? Arbitrarily? This point, is even more important because during the work flow of the experiment, there are some manual processes that include non-standardizable component, as the authors mention (#368, 369).

Response: We thank the reviewer for these insightful questions. Each prepared tooth was scanned only for one time to design a full crown using Exocad. The produced STL file for each tooth was then exported to fabricate six crowns (three by direct 3D printing and three by milling of the printed blocks).

Each crown was scanned for two times: first one, for the crown without silicone to measure the trueness by comparing it with the corresponding CAD design, while the other scan was done for the crown with the silicone replica to compare it with the first scan for internal and marginal measurements.

Internal accuracy (trueness) was calculated by comparing the produced crown with its corresponding CAD design using Geomagic Control X.

The ±10 μm value was not arbitrarily chosen, it was seted in software to control the color-coded map, it’s important to mention that the change of this number has no effect on the resulted RMS values, its only change the intensity of the color map which served only as a visual guide to enhance the interpretation of the 3D deviation. We chose ±10 μm specifically based on previously published literatures.

Regarding the paragraph (#368, 369), its clearly stated that we intentionally measured only the intaglio surface of the crowns to prevent any manual processes that include non-standardizable component.

We appreciate the reviewer’s attention to these methodological details and hope this clarification addresses the concerns. Let us know if you'd like to add or edit any information to the manuscript.

 

Comment 7: The authors mention that «# 445, 446 Unlike the milled group, most of the 3D-printed crowns exhibited statistically significant differences for both internal and marginal adaptation» and give some explanations. Did they calculate this difference between the crowns of the same tooth, so their explanations are possible or they included all crowns from all teeth, so I think that there is an interpretation problem in this point?

Response: We appreciate the reviewer’s question. Indeed, a statical comparisons were made among the printed group (print VS, CC, PC) and among the milled group (Mill VS, CC, PC) for each sample using post hoc tests, these comparisons reflect other prospective of this research by showing the effect of using different materials under a constant manufacturing technique. While this intra-technique comparison was not the main aim of this study, it provided further insight into how material type may influence crown adaptation.

These comparisons and corresponding p-values are presented by the different superscript letters in Table 2 and Table 3 in the results section of the revised manuscript. Please let us know if further clarification is required.

 

 

Comment 8: In the discussion section must be stated if the null hypothesis is accepted or not.

Response: Thank you. The Discussion section has now been updated to include null hypothesis.

This revision can be found on page 12, Paragraph 2, lines 371-373.

Modification to Manuscript: The results demonstrated a statistically significant difference between the two fabrication techniques in terms of trueness, internal gap, and marginal gap. Consequently, the null hypothesis was completely rejected.

 

 

Comment 9: It is very interesting from a clinical point of view the observation and reference of «the inverse relation between trueness and both internal and marginal fitness of the fabricated crowns» (#408) but needs clearer (in my opinion) data and evidence.

Response: We appreciate the interest in this observation. While a clear statistical correlation was not the primary aim of this study, we added an explanation in the discussion section to explain how lower trueness in printed crowns might appeared to facilitate improved seating (better fitness), likely due to reduced hydraulic resistance and enhanced cement flow space.

We acknowledge the need for further investigations to explore this correlation in greater depth.

Once again, thank you for your valuable feedback. We believe these revisions have strengthened our manuscript and clarified several key aspects.

Reviewer 2 Report

Comments and Suggestions for Authors

The study aims to provide a controlled and direct comparison of two crown manufacturing techniques, Milling and 3D printing, evaluating  trueness and fitness of the fabricated crown.

While this topic is not original and there are many articles addressing this milling and 3D printing of dental prostheses, the manuscript is unique in its approach by using the same techniques on three different materials across both techniques with a single operator and under the same conditions. This design eliminates a number of biases such as material differences, multiple operator calibration, or different fabrication conditions, etc.  The study demonstrates a sound design and approach to comparing the techniques in crown fabrication related to fit and marginal integrity.

This invitro study provides contributions to the existing body of literature through its controlled design and methodology in evaluating the three different materials using both techniques and rigorous evaluation of quality of restorations produced and fit.

The methods and materials section is comprehensive and well organized. It describes in depth each step of each procedure from material used, crown preparation, prosthesis fabrication to measures.

It would be helpful to add labeling to table 1 which indicates its focus is trueness. The table in under the appropriate section but adding the word “trueness” to the legend would make it clearer.  

The conclusions are consistent with the results presented from the different analyses and evaluation of internal fit and marginal integrity of the crowns produced and does demonstrate a significant difference in some instance based materials and technique. Comparisons across different materials and within respective groups are appropriately displayed in tables and figures that are also consistent with the results and data generated.

 

Statistical Analysis – this section could be improved by describing how the power for the study was calculated along with significance.

The references are appropriate to the topic and current.

The additional items would help further enhance the study;

1. Study limitations are not clearly delineated in the discussion section. For example was the study adequately powered, materials selected versus others not selected, tooth selection, or other potential confounders or bias that may have been introduced that my have impacted the outcomes.

Comments on the Quality of English Language

2. Addressing the following grammatical issues would improve the manuscript:

Line 61 – word “belongs” needs to be edited to the right tense

Line 410 - is an incomplete sentence

Line 422 – the sentence needs editing for better clarity

Author Response

Reviewer 2

 

Dear Reviewer,

We would like to thank you for your constructive and thoughtful comments regarding our manuscript titled:
“[Milling Versus Printing: The Effect of Fabrication Technique on The Trueness and Fitness of the Fabricated Crowns (A Comparative In Vitro Study)]” (Manuscript ID: [prosthesis-3789439]).

We have carefully considered all suggestions and revised the manuscript accordingly. Below, we provide a point-by-point response to each comment. All changes have been highlighted in the revised manuscript for your convenience. Additionally, the manuscript has been language-edited using the MDPI Author Services to enhance clarity and fluency.

 

 

Comment 1: It would be helpful to add labeling to table 1 which indicates its focus is trueness. The table in under the appropriate section but adding the word “trueness” to the legend would make it clearer.

Response: We appreciate this helpful suggestion. We have revised the legend of Table to clearly indicate that it reports trueness results.

This revision can be found on page 10, line 311.

Modification to Manuscript: Descriptive statistics (mean ± SD) of trueness in (µm) and comparison of significance among the different groups by Kruskal-Wallis test and Dunn's test.

 

 

Comment 2: Statistical Analysis – this section could be improved by describing how the power for the study was calculated along with significance.

Response: We thank the reviewer for this important observation. A new sentence has been added to the Statistical Analysis section to clarify the power analysis.

This revision can be found on page 10, Paragraph 1, lines 283-285.

Modification to Manuscript: A prior power analysis was performed using G Power software (version 3.1.9.7) to determine the sample size, assuming a medium effect size (f = 0.4), a significance level of α = 0.05, and a desired power of 80%.

 

Comment 3: Study limitations are not clearly delineated in the discussion section. For example was the study adequately powered, materials selected versus others not selected, tooth selection, or other potential confounders or bias that may have been introduced that may have impacted the outcomes.

Response: We thank the reviewer for this valuable comment. Regarding material selection, the three materials included in this study were chosen based on their market availability and clinical relevance. The number was intentionally maximized to three materials in order to enhance the generalizability of the study findings.

As for tooth selection, a clarifying sentence was written in the Materials and Methods section: “Ten intact, non-carious, unrestored human maxillary first premolars extracted for orthodontic treatment purposes and gathered from patients aged 18 to 25 years were used in this study. Teeth of comparable shape and size were chosen by measuring mesiodistal and buccolingual dimensions with a digital caliper.”

In the same context, we fully agree with the reviewer on the importance of transparently stating study limitations. Accordingly, we have added a new paragraph in the Discussion section outlining the potential limitations.

This revision can be found on page 14, Paragraph 7, lines 461-469.

Modification to Manuscript: Despite that every attempt was followed to provide high level of standardization during all procedural steps (e.g., same abutment, same milling and printing devices, same design parameters), this study still presents several limitations. The findings of this study may not fully represent intraoral conditions, such as moisture and functional loading. Secondly, the analysis focused on the intaglio surface only, while the outer surface and occlusal anatomy were not evaluated, which may be important for a more comprehensive evaluation. Finally, only one milling unit and one 3D printer were used, although this approach ensured a high level of standardization, it may limit the gener-alizability of the results across other systems and brands.

Comment 4: Addressing the following grammatical issues would improve the manuscript:

1. Line 61 – word “belongs” needs to be edited to the right tense
2. Line 410 - is an incomplete sentence
3. Line 422 – the sentence needs editing for better clarity

Response: We appreciate the reviewer’s careful attention to language and grammar. All the sentences have been corrected.

1. The word “belongs” deleted and replaced following the recommendation of (MDPI Author Services language editing).

This revision can be found on page 2, Paragraph 4, line 61.

 

Modification to Manuscript:

2. This technique serves as a simulation of the clinical cementation procedure, utilizing an extra-light silicone material applied to the respective tooth, which accurately replicates the final cement layer.

This revision can be found on page 13, Paragraph 8, lines 419-421.

 

3. Therefore, when a crown restoration with high trueness of the intaglio surface, the milled crowns in this study, is seated onto its corresponding abutment, excess cement may accumulate on the occlusal surface due to insufficient escape space at the cervical area. This can hinder complete seating of the crown and subsequently increase both marginal and internal discrepancies.

This revision can be found on page 14, Paragraph 1, lines 431-435.

 

 

Comment 5 on English Language

Response: The highlighted language issues have been addressed, and the manuscript has undergone additional editing through (MDPI Author Services language editing) to enhance fluency and clarity.

We hope that the revisions meet your expectations, and we are grateful for the opportunity to improve our work. Please do not hesitate to contact us about any further clarification, Regards.

Reviewer 3 Report

Comments and Suggestions for Authors

The paper is devoted for investigations of the Effect of Fabrication Technique on The Trueness and Fitness of the Fabricated Crowns (A Comparative In Vitro Study). The topic is generally interesting, however the paper contain unexplained places (below) and need major revisions.

Page 3, line 74, please explain what impact of patient age can be on your performed investigations.

Page 4, lines 116-118, please explain why namely such design parameters were selected for investigations.

Page 8, line 252, please explain why static load namely of 5 kg was applied.

Page 9, lines 281-286 corresponding references should be added.

Results presented in Fig. 11 should be more discussed.

Conclusions should be rewritten in more informative way.

Author Response

Reviewer 3

Dear Reviewer,

We would like to thank you for your constructive and thoughtful comments regarding our manuscript titled:
“[Milling Versus Printing: The Effect of Fabrication Technique on The Trueness and Fitness of the Fabricated Crowns (A Comparative In Vitro Study)]” (Manuscript ID: [prosthesis-3789439]).

We have carefully considered all suggestions and revised the manuscript accordingly. Below, we provide a point-by-point response to each comment. All changes have been highlighted in the revised manuscript for your convenience.

 

Comment 1: Page 3, line 74, please explain what impact of patient age can be on your performed investigations.

Response: We thank the reviewer for this question. For ease of collection, teeth were collected from patients undergoing orthodontic treatment with age range 18-25 years.  Moreover, this age group mostly presents with fully erupted teeth, intact enamel, and minimal age-related structural changes such as surface wear. This ensure consistency in tooth morphology, which is critical for standardizing preparation and evaluating restoration accuracy.

 

 

Comment 2: Page 4, lines 116-118, please explain why namely such design parameters were selected for investigations.

Response: We thank the reviewer for this important question. The selected design parameters were based on previously published literatures for the clinical standards of CAD/CAM crown design.

A cement space of 100 μm starting 1 mm above the finish line is widely accepted as optimal for facilitating crown seating without compromising marginal integrity. The zero-cement space at the marginal border was selected to maintain a precise marginal seal, as recommended in studies that discussed minimizing microleakage and marginal exposure.

The anticipated milling diameter of 1.2 mm was chosen based on the bur size of the used milling unit (In-Lab MC XL, Sirona, Germany), ensuring compatibility between the software design and the actual milling process. This setting helps avoid over-milling or undersized features that could affect the final fit of the restoration.

 

 

Comment 3: Page 8, line 252, please explain why static load namely of 5 kg was applied.

Response: We thank the reviewer for this question. A 5 kg static load (approximately 49 N) was applied during crown seating to simulate the average biting forces generated by the jaw or finger pressure during clinical cementation. This value is commonly used in replica technique protocols in the literature and has been shown to provide consistent and clinically relevant results without distorting the impression material or over-seating the restoration. Applying a controlled load ensures standardization across all samples and minimizes operator variability.

We added this clarification behind the use of a 5 kg load on page 8 and 9, lines 254-257.

Modification to Manuscript: which was then gently seated on its corresponding abutment under a static load of 5 kg using a modified dental surveyor to simulate the average biting forces generated by the jaw or finger pressure during clinical cementation. This step ensures standardization across all samples and minimizes operator variability.

 

 

Comment 4: Page 9, lines 281-286 corresponding references should be added.

Response: We thank the reviewer for this helpful remark. Relevant references supporting the use of the applied statistical tests (e.g., Shapiro–Wilk, Levene’s, Kruskal–Wallis, Dunn’s test, ANOVA, and Tukey’s HSD) will be included in the revised manuscript. 

 

 

Comment 5: Results presented in Fig. 11 should be more discussed.

Response: We would like to clarify that the comparisons related to trueness measurements between the fabrication techniques are addressed in the discussion section (lines 384-408), while the comparisons among different materials within the same manufacturing technique are discussed in lines 409-414. We believe these aspects have been appropriately covered; however, if the reviewer identifies any specific points that require further elaboration, we would be pleased to revise and expand the relevant sections accordingly.

 

 

Comment 6: Conclusions should be rewritten in more informative way.

Response: We sincerely thank the reviewer for this suggestion. In response, we have revised the conclusion section to present the key findings in a more informative and structured manner.

This revision can be found on page 15, Paragraph 2, lines 485-502.

Modification to Manuscript:

- Regardless of the fabrication technique or material used, the mean values of trueness, internal gap, and marginal gap of all groups were all below the clinically acceptable limits. This finding supports the suitability of both additive and subtractive techniques for the fabrication of definitive dental restorations using hybrid ceramic materials.

- The fabrication technique had a significant influence on the accuracy of the restorations in comparison to the type of material used.

- Subtractive technique produced crowns with significantly higher trueness than the crowns produced by additive technique across most materials.

- Additive technique produced crowns with significantly better internal and marginal fitness compared to the crowns produced by subtractive technique.

- The novel approach of using custom-milled blocks derived from printable resins followed in this study enabled a standardized comparison between both fabrication techniques. By using the same material in both workflows, the study successfully eliminated material-related variables.

- These findings may offer new insights for clinical applications of custom-milled blocks by expanding the versatility of printable materials.

 

 

We hope that the revisions meet your expectations, and we are grateful for the opportunity to improve our work. Please do not hesitate to contact us about any further clarification, Regards.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors tried hard to improve their manuscript and responded to all of my comments in details. This is very appreciated.

In most of their responds the authors gave quite acceptable responds and made changes.

But I have, still, some questions about the methodology.

«Teeth of comparable shape and size were chosen by measuring mesiodistal 84 and buccolingual dimensions with a digital caliper». Comparable doesn’t mean same for the level of digital accuracy measurement methods that are used in the study. As I mention below, if the values from all teeth are calculated together it is a possible bias.

In their response the authors mention that « Regarding the paragraph (#368, 369), its clearly stated that we intentionally measured only the intaglio surface of the crowns to prevent any manual processes that include non-standardizable component»

But there are several manual processes during the workflow. Below I quote some points of it.

«teeth preparation was performed by the same operator» Standard procedures were performed for preparing the teeth, but the teeth were different for the level of the proposed accuracy.

«The prepared teeth were scanned by using Primescan Connect IOS», I suppose manually by hand

 «Once the light body material had set completely, the crown was carefully detached from the abutment tooth, with the silicone replica remaining in the internal surface»

«controlled manual brushing» «The restorations were manually arranged on the build platform» « was shaken well for 2 mins» 

«the support structures for each crown were removed with the help of using flush cutters to clip them off»

«The printed blocks were glued to a universal metal holder»

How was performed the replica scan with the Primescan Intraoral Scanner. How did they perform a standard scanning procedure for all intaglio surfaces?

«Although this step was  performed by the same practitioner, still manual rework always includes a subjective,  non-standardizable component»

I can’t understand why by measuring the intaglio surface, the influence of the manual processes is eliminated.

So I still believe that it is needed to determine the internal accuracy of the method

Another point, important to me is how the authors measured the mean values.

The authors responded that « For each prepared tooth, six crowns were fabricated (three via 3D printing using the three mentioned materials, and three via milling the produced blocks manufactured from these same printable materials). All six crowns shared the same abutment and CAD design, ensuring a high level of standardization, with the fabrication technique being the only variable». But in calculating the mean values (Fig 11 and 12) what values did they introduce? From all teeth (10?). What is the «n»? If all values from all teeth have introduced then there is a possible bias (the teeth are not the same) if there is no evaluation of the internal accuracy of the measuring methodology.

I am trying to measure the «n».

 In the printing platforms produced twenty (10 crowns and ten blocks) for each tooth. 3 types of materials, so in total 60 pieces for each tooth? In total for all teeth 600 pieces?   For every tooth six crowns were used. 10X6=60. Honestly, I can't understand which number is the «n» in the calculations. Did the authors made more specimens? How did they choose the six for the experiment.

 

To summarize I still believe that complex methodology of the study has unclear to me points. I don’t support that it is wrong. In my knowledge the first step is to determine the accuracy (trueness and precision) of the research method and measure its abilities and limits with standardized models and then compare techniques, materials and other parameters.  

 

In the conclusion section the authors mention that «The fabrication technique had a significant influence on the accuracy of the restorations in comparison to the type of material used». In their response mention that «This approach aligns with the aim of this study to evaluate trueness rather than precision». So, I think that it is more accurate to conclude that the «fit, the trueness…. » than «accuracy»  has influenced by the fabrication technique. As they properly mention in the introduction section «The accuracy is typically evaluated by both trueness and precision».

 

Author Response

Reviewer 1 (Round 2)

 

Dear Reviewer,

Thank you again for your comments regarding our manuscript titled:
“[Milling Versus Printing: The Effect of Fabrication Technique on The Trueness and Fitness of the Fabricated Crowns (A Comparative In Vitro Study)]” (Manuscript ID: [prosthesis-3789439]).

We sincerely appreciate your insightful comments and the opportunity for this constructive discussion. Your observations have been very valuable and we are pleased to provide detailed, point-by-point responses to address each of them. All corresponding modifications have been incorporated into the last revised manuscript and highlighted using the (Track Changes) function in Microsoft Word, in accordance with the journal’s suggestion.

 

Comment 1: «Teeth of comparable shape and size were chosen by measuring mesiodistal 84 and buccolingual dimensions with a digital caliper». Comparable doesn’t mean same for the level of digital accuracy measurement methods that are used in the study. As I mention below, if the values from all teeth are calculated together it is a possible bias.

Response: We agree with the reviewer’s observation that “comparable” does not mean “same” and we appreciate the opportunity to clarify this point further:

Our study was conducted on natural teeth to simulate the clinical situation as closely as possible, natural teeth have a wide range of variations in size and shape from patient to another, although teeth dimensions had no direct relation on the final results of our study because each crown was compared only to its respective abutment (e.g., the crowns fabricated for tooth no. 2 were evaluated against the design for tooth no. 2 only, and not against any other abutment), we minimized this variability by measuring mesiodistal, buccolingual, and occlusogingival dimensions with a digital caliper to exclude specimens that were excessively large or small, thereby ensuring a degree of uniformity.

We would like to emphasize that the level of digital accuracy measurement methods was consistent across all samples, ensuring the absence of bias (please check comment 5). To address the reviewer’s concern and prevent any potential misunderstanding, we have added a clarifying sentence in section (2.1. Tooth Selection and Preparation) stating that the shape and size of the teeth done only for ensuring some degree of uniformity.

This revision can be found on page 3, Paragraph 1, lines 80-81.

 

Modification to Manuscript: Teeth of comparable shape and size were chosen by measuring mesiodistal and buccolingual dimensions with a digital caliper, to exclude specimens that were excessively large or small, thereby ensuring a degree of uniformity.

 

 

 

Comment 2: In their response the authors mention that « Regarding the paragraph (#368, 369), its clearly stated that we intentionally measured only the intaglio surface of the crowns to prevent any manual processes that include non-standardizable component»

But there are several manual processes during the workflow. Below I quote some points of it.

«teeth preparation was performed by the same operator» Standard procedures were performed for preparing the teeth, but the teeth were different for the level of the proposed accuracy.

«The prepared teeth were scanned by using Primescan Connect IOS», I suppose manually by hand

 «Once the light body material had set completely, the crown was carefully detached from the abutment tooth, with the silicone replica remaining in the internal surface»

«controlled manual brushing» «The restorations were manually arranged on the build platform» « was shaken well for 2 mins»

«the support structures for each crown were removed with the help of using flush cutters to clip them off»

«The printed blocks were glued to a universal metal holder»

«Although this step was performed by the same practitioner, still manual rework always includes a subjective, non-standardizable component»

I can’t understand why by measuring the intaglio surface, the influence of the manual processes is eliminated.

Response: We thank the reviewer for these observations.

How does measuring the intaglio surface eliminate the influence of manual processes?? Printed crowns have support structures that designed and located on their outer surface, milled crowns have sprue attachment located also on the outer surface. The removal of these supports or sprue requires manual finishing procedures that cannot be standardized among the crowns of the same abutment (over-trimming or under-trimming during this process can inevitably alter the outer geometry of the restoration) which might affect the final result, for this reason, we chose to measure only the intaglio surface trueness and eliminating the variability introduced by manual finishing of the outer surface. The tests of this research (trueness, internal, marginal adaptation) and the correlation between them are directly related to the intaglio surface measurements.

Therefore, this rationale, which forms a fundamental aspect of our study design, has been addressed and mentioned in the Trueness discussion section.

 

Regarding the other manual processes during the workflow, we made every possible effort to standardize each step in the Materials and Methods section in order to limit variables and isolate the net effect of the fabrication technique.

• Teeth preparation: A modified dental surveyor was employed to minimize variability during tooth preparation.
• Scanning: Each prepared sample was embedded in an acrylic resin base for stabilization, and the practitioner followed the Palatal–Occlusal–Buccal (POB) scanning strategy in strict accordance with the manufacturer’s instructions.
• Block fixation: The gluing of printed blocks to the universal metal holder was guided by sharp reference landmarks located into the printed blocks that exactly compatible with the shape of the metal holder, ensuring precise and repeatable positioning.

 

The remaining manual steps (which were different in their effect on the final results) were performed manually by the same practitioner using a consistent protocol. We acknowledge that complete elimination of manual intervention is not possible and cannot be fully standardized, which can be considered as further limitation of this study.

We will add modifications to the Discussion, to clearly address how does measuring only the intaglio surface minimized the influence of manual processes.

This revision can be found on page 13, Paragraph 3, lines 389-390.

Modification to Manuscript: Only the inner surface of the crowns was involved in the measurement to eliminate the distortion effect of the outer surface that may ensue via the manual removal of the supports and sprue, even when the removal performed by the same practitioner, still manual rework always includes a subjective, non-standardizable component.

 

 

 

Comment 3: How was performed the replica scan with the Primescan Intraoral Scanner. How did they perform a standard scanning procedure for all intaglio surfaces?

 

Response: We acknowledge the reviewer’s comment and appreciate the opportunity to clarify.

Each crown was stabilized on a base of base plate wax with its intaglio surface facing upward. The practitioner then performed the scanning using the Primescan intraoral scanner. This scanner boasts an automatic shake detection system, which allows images to be acquired only if the camera is absolutely still with innovative Smart Pixel Sensor that is a property found only in this scanner. Furthermore, the "Dynamic Depth Scan" presented by this scanner resulting in perfect sharpness. This scanner has a large scanning window (15 x 15 mm), which is larger than that of the other IOSs and can easily capture the intaglio surface of the crowns, decreasing the stitching of image files which enhance the accuracy. These properties facilitated a straightforward, reproducible scanning procedure across all crowns.

We will add a clarifying sentence to the Materials and Methods section to clearly address this important point.

This revision can be found on page 7, Paragraph 4, lines 210-211.

 

Modification to Manuscript: Trueness assessment was started by stabilization of each crown on a base of baseplate wax with its intaglio surface facing upward, then the intaglio surface was scanned using an intraoral scanner (Primescan Connect).

 

Comment 4: Another point, important to me is how the authors measured the mean values.
in calculating the mean values (Fig 11 and 12) what values did they introduce? From all teeth (10?).

Response: We appreciate the opportunity to clarify this point.

For each subgroup, the mean value was calculated by the summation of the measurements obtained from all ten crowns of this subgroup for the ten prepared teeth and dividing the total by ten. This procedure was applied to all six subgroups (Mill VS, Mill CC, Mill PC, Print VS, Print CC, Print PC).

Yes, the values represent all 10 prepared teeth in each subgroup, as they all share the manufacturing technique and the material type.

Here is an example of the mean of trueness for the Mill VS group that presented in Fig 11:

 

No. of the prepared tooth	RMS values for Mill VS crowns
1	28.5
2	22.6
3	24.7
4	33.2
5	34.2
6	34.9
7	30
8	29.1
9	32.1
10	30.6
Mean = 29.99

 

 

 

 

 

 

Comment 5: What is the «n»?.

I am trying to measure the «n».

In the printing platforms produced twenty (10 crowns and ten blocks) for each tooth. 3 types of materials, so in total 60 pieces for each tooth? In total for all teeth 600 pieces?   For every tooth six crowns were used. 10X6=60. Honestly, I can't understand which number is the «n» in the calculations. Did the authors made more specimens? How did they choose the six for the experiment.

Response: We thank the reviewer for highlighting this point of potential confusion. The sample size for each subgroup was 10.

It is important to note that the printing platform produced twenty items (10 crowns and 10 blocks) not for each tooth, but for all ten prepared teeth combined (one crown for each)( Please see the diagram at the end of this document)

After completion the design step of the ten prepared teeth, all STL files for the 10 prepared teeth were imported onto the printing platform with the STL file of the block that was duplicated into ten times. Only single print for each material was done to produce 10 crowns and 10 blocks (one crown and one block for each of the ten prepared teeth). A total of three print for the three materials produced 30 printed crown and 30 printed blocks.

After the milling of the printed blocks, 60 crowns were obtained in total.  All the 60 crowns then divided into six subgroups (Mill VS, Mill CC, Mill PC, Print VS, Print CC, Print PC), with each subgroup containing ten crowns (n = 10).

We have revised the manuscript to more clearly explain the total number of crowns produced, and the number of the sample size (n) to prevent any further misunderstanding.

This revision can be found on page 7, Paragraph 3, lines 200-203.

Modification to Manuscript: The resulted 30 milled crowns were stored in individually labeled containers. Together with the printed crowns, this resulted in a total of 60 crowns, which were divided into six subgroups (Mill VS, Mill CC, Mill PC, Print VS, Print CC, Print PC), with each subgroup containing ten crowns (n = 10).

 

 

Comment 6: In the conclusion section the authors mention that «The fabrication technique had a significant influence on the accuracy of the restorations in comparison to the type of material used». In their response mention that «This approach aligns with the aim of this study to evaluate trueness rather than precision». So, I think that it is more accurate to conclude that the «fit, the trueness…. » than «accuracy» has influenced by the fabrication technique. As they properly mention in the introduction section «The accuracy is typically evaluated by both trueness and precision».

Response: We thank the reviewer for this valuable observation. We agree that it is more precise to refer specifically to “trueness” rather than the broader term “accuracy”. Accordingly, we will revise the conclusion to replace “accuracy” with “trueness” to ensure consistency with the study’s aim.

This revision can be found on page 15, Paragraph 5, line 505.

Modification to Manuscript: The fabrication technique had a significant influence on the trueness of the restorations in comparison to the type of material used.

 

 

 

 

 

 

 

 

Frankly, we are not entirely certain that we have interpreted all aspects of the question correctly; however, we have made every effort to provide the most appropriate answers, and we hope that our responses adequately address the reviewer’s concerns. Additionally, we have included a simple diagram below to illustrate the general outline of the Methodology of our study, which we believe will be helpful.

We remain ready to provide further clarification if required.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Authors make proper corrections according to reviewer remarks and I suggest publish the paper as it is.

Author Response

We sincerely thank the reviewer for the positive feedback and recommendation for publication.