Accuracy and Fit of Ceramic Filled 3D-Printed Resin for Permanent Crown Fabrication: An In Vitro Comparative Study

Response to Reviewer 3 Comments

1. Summary

Thank you very much for taking the time to review this manuscript. Your comments and recommendations are appreciated. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

3. Point-by-point response to Comments and Suggestions for Authors

1. **Major Proofreading:**a

Comment 1: [ **Grammar and Repetition**: The manuscript contains grammatical mistakes, repeated information, and formatting errors. For instance, lines 140-144 repeat lines 135-139. Additionally, line 115 has a formatting error. A thorough revision by a native English speaker is advised. ]

Response 1: Thank you for pointing this out.

[ formatting error and repeated information adjusted]

Text[Following preparation, the master die was digitized using a desktop scanner (3Shape 135 E3 Dental Lab scanner, 3Shape, Copenhagen, Denmark). The resulting digital model was 136 then imported into CAD software (3Shape, Copenhagen, Denmark) for crown design. 137 Subsequently, Standard Tessellation Language (STL) files were generated, then used in 138 the fabrication of the ceramic-filled hybrid permanent crown specimens (ISO 10477:2020). 139 After the preparation, the die underwent scanning utilizing a desktop scanner 140 (3Shape E3 Dental Lab scanner; 3Shape, Copenhagen, Denmark). The scanned data was 141 subsequently uploaded in CAD software (3Shape, Copenhagen, Denmark) for crown de- 142 sign. The resultant Standard Tessellation Language (STL) file was then produced for each 143 ceramic-filled hybrid permanent crown material (ISO 10477:2020).]

Adjusted text [Following preparation, the master die was digitized using a desktop scanner (3Shape E3 Dental Lab scanner, 3Shape, Copenhagen, Denmark). The resulting digital model was then imported into CAD software (3Shape, Copenhagen, Denmark) for crown design. Subsequently, Standard Tessellation Language (STL) files were generated, then used in the fabrication of the ceramic-filled hybrid permanent crown specimens (ISO 10477:2020).]

Thank you for pointing this out. I have done the necessary adjustments.

Also, the manuscript was reviewed by a native English speaker for editing and proofreading.

2. **Introduction: **

Comment 1: [- **Scientific Support for DLP**: Lines 53-55 claim DLP as cost-effective but do not cite the best dimensional accuracy or superior detail. Correct this with appropriate references.]

Response 1: Thank you for the suggestion. The mentioned publication was cited. [appropriate reference added to text]

[Tsolakis IA, Papaioannou W, Papadopoulou E, Dalampira M, Tsolakis AI. Comparison in Terms of Accuracy between DLP and LCD Printing Technology for Dental Model Printing. Dent J (Basel). 2022 Sep 28;10(10):181. doi: 10.3390/dj10100181. PMID: 36285991; PMCID: PMC9600557.]

Comment 2: [**Terminology**: Change “leverages” to “uses” on line 57.]

Response 2: [ necessary text adjustment done] from [ In contradistinction to alternative 3D printing techniques, DLP leverages a digital projector to facilitate the simultaneous photopolymerization of entire resin layers. This streamlined approach engenders superior dimensional accuracy and expedited fabrication times [9].]

To [In contradistinction to alternative 3D printing techniques, DLP uses a digital projector to facilitate the simultaneous photopolymerization of entire resin layers. This streamlined approach engenders superior dimensional accuracy and expedited fabrication times [9].]

Comment 3: [**Historical Accuracy**: Line 61 states “relatively few instances,” which is inaccurate given the 15 years of research in 3D printing materials.]

Response 3: text [there are relatively few instances in the literature that address is- 61 sues concerning the parameters that govern the features and qualities of 3D-printed re- 62 storative dental materials [10, 11].]changed to [While dentistry is widely acknowledged as a field that can greatly benefit from 3D printing technologies, the literature address issues concerning the parameters that govern the features and qualities of 3D-printed restorative dental materials [10, 11].]

Comment 4: [Line 242: Please adjust the alignment of the contents in the table.]

Response 4: [adjusted] Thank you

Comment 5: [in the introduction, authors used different terms – 3D printing/additive manufacturing and subtractive manufacturing/CAD/CAM. I’d suggest authors unify terms with similar meanings. i.e. use 3D printing and CAD/CAM only, or AM and SM only.]

Response 5: [I have unified the terms and eliminated AM and SM.]

Comment 6: [**Description of Accuracy**: Lines 88-91 should refer to the appropriate ISO standard for accuracy. The term is introduced in line 116 without prior explanation.]

Response 6: [in the introduction section the terms were introduced and explained prior to being mentioned in the materials and methods section should iso standard explanation added]

Comment 7: [**Term Usage**: Replace “fidelity” with “accuracy” on line 92.]

Response 7: text [A preponderance of contem- 91 porary dental research endeavors to illuminate the dimensional fidelity, as characterized 92 by both trueness and accuracy, of restorations fabricated via milling techniques in com- 93 parison to alternative restorative modalities [17].]

Adjusted text [A preponderance of contemporary dental research endeavors to illuminate the dimensional accuracy, as characterized by both trueness and accuracy, of restorations fabricated via milling techniques in comparison to alternative restorative modalities [17].]

Comment 8: [**Scientific Evidence**: Lines 103-106 should acknowledge the abundance of scientific evidence.]

Response 8: text [A critical appraisal of the existing literature reveals a dearth of investigations meticulously evaluating the marginal adaptation, and dimensional fidelity (encompassing both 104 accuracy and trueness), of full-contour, additively manufactured, ceramic-filled resin-polymer crowns. This knowledge necessitates further rigorous research endeavors to definitively ascertain whether these 3D-printed restorations can achieve a level of precision and accuracy comparable with their milled counterparts ]

[rewritten and clarified.] as [A critical appraisal of the existing literature reveals that some investigations evaluated the marginal adaptation, and dimensional accuracy (encompassing both trueness and precision), of full-contour, additively manufactured, ceramic-filled resin-polymer crowns. This knowledge necessitates further rigorous research endeavors to definitively ascertain whether these 3D-printed restorations can achieve a level of precision and accuracy comparable with their milled counterparts [10, 11, 21-24].]

Comment 9: Language Clarity**: Avoid qualitative terms like “meticulously” and “constellation.” Use direct, clear, and concise language.]

Response 9: [replaced and clarified.]

Comment 10: [**Material Selection**: Explain why Enamic was chosen as the milled group over materials like lithium disilicate or zirconia.]

Response 10: [Thank you for your valuable comment. Enamic is a composite resin polymer matrix and integrated ceramic filler particles make up composite-based CAD/CAM materials similar to the tested groups]

Text changes: The expanding integration of polymer-based computer-aided de-sign/computer-aided manufacturing (CAD/CAM) systems in restorative dentistry ne-cessitates a meticulous assessment of the material properties governing the perfor-mance of permanent crown resins. Commercially available materials designed for composite restorations typically consist of a resin-matrix reinforced with dispersed ceramic filler particles. The precise composition and weight ratio of these components exhibit variation across distinct CAD/CAM materials and are believed to be a primary determinant of their resultant material properties. The lack of knowledge concerning their long-term clinical behavior underscores the critical need for a comprehensive evaluation to elucidate their inherent advantages and potential limitations that may influence their efficacy in vivo.

Comment 11: [**Null Hypothesis**: Clearly state the null hypothesis.]

Response 11: [rewritten and clarified.]

Text [Therefore, the present investigation was meticulously designed to assess the trueness, precision, and marginal adaptation of 3D-printed crowns fabricated from two distinct ceramic-filled hybrid permanent crown resin materials, in direct comparison to milled ceramic-filled material. We hypothesized that there would be no statistically significant discrepancies in trueness, precision, and fit between the evaluated 3D-printed and milled crown samples.]

Adjusted text [Therefore, the present investigation was designed to assess the trueness, precision, and marginal adaptation of 3D-printed crowns fabricated from two distinct ceramic-filled hybrid permanent crown resin materials, in direct comparison to milled ceramic-filled material. The null hypothesis states that there would be no statistically significant discrepancies in trueness, precision, and fit between the evaluated 3D-printed and milled crown samples.]

3. **Materials and Methods:**

Comment 1: [**Definitions**: Clearly state how accuracy, trueness, and precision were assessed.]

Response 1: [clarified]

Line 76 to 79

Text [Trueness, a concept distinct from precision, characterizes the systematic error associated with a measurement. It quantifies the deviation or disparity between the measured values and the actual or intended value. Conversely, precision reflects the level of agreement or reproducibility among replicated measurements] and the assessment procedure is explained in the materials and methods.

Comment 2: [**Sample Size Justification**: Provide detailed information on mean, dispersion measures, effect size, and power analysis used to determine the sample size of 39 crowns (13 per group).]

Response 2: [relied on previous research sample size. A sample size of 39 molar crowns (13 per group) was determined based on previous research [16, 21, 22, 24].

Comment 3: [**Manufacturing Processes**: Consistently detail the scanner type and layer thickness for all materials to ensure reproducibility.]

Response 3: [added.]

Text [the master die was digitized using a desktop scanner (3Shape 135 E3 Dental Lab scanner, 3Shape, Copenhagen, Denmark).and after the preparation, the die underwent scanning utilizing a desktop scanner 140 (3Shape E3 Dental Lab scanner; 3Shape, Copenhagen, Denmark).]and

[Layer thickness and light curing duration are mentioned in table 1]

Comment 4: [ **Typo Correction**: Correct the typo on line 115.]

Response 4: text [16, 21, 22, 24]. line 115

 This in vitro study evaluated the accuracy (trueness and precision), internal fit, and 116 marginal adaptation of 3D-printed ceramic-filled hybrid crown specimens. ]

New text [This in vitro study evaluated the accuracy (trueness and precision), internal fit, and marginal adaptation of 3D-printed ceramic-filled hybrid crown specimens. Specimens were fabricated following ISO 10477:2020 standards (Dentistry — Polymer-based crown and veneering materials) and manufacturer recommendations [1].]

Comment 5: [**Curing Processes**: Include the duration of curing processes for each case in Table1.

Response 5: [clarified in table 1]

Comment 6: [**Repeated Information**: Correct lines 140-144 to avoid repetition of lines 135-139.]

Response 6: [already addressed]

Text [Adjusted text [Following preparation, the master die was digitized using a desktop scanner (3Shape E3 Dental Lab scanner, 3Shape, Copenhagen, Denmark). The resulting digital model was then imported into CAD software (3Shape, Copenhagen, Denmark) for crown design. Subsequently, Standard Tessellation Language (STL) files were generated, then used in the fabrication of the ceramic-filled hybrid permanent crown specimens (ISO 10477:2020).]

Comment 7: [**Resin Agitator**: Justify the use of the resin agitator for only 2 minutes with appropriate references.]

Response 7:

Based on the manufacturer's recommendation of VarseoSmile Crown plus and CROWNTEC they do not need to be mixed “Before starting each printing process, VarseoSmile Crown plus does not need to be mixed, even after long periods, up to a month, of non-use” the mixing time was for 5 minutes based on the recommendation of the 3D printer manufacturer.

https://www.bego.com.tr/laravel-filemanager/files/5/%C3%9Cr%C3%BCn%20PDF/VarseoSmile%20Crown%20plus%20%E2%80%93%20Instructions%20for%20Use.pdf

https://www.saremco.ch/wp-content/uploads/2022/03/D600248_GA_saremco-print-CROWNTEC_EN_USA_edited-02-2022_DRUCK_frei.pdf

Mixing, Stirring, and Curing Chart for NextDent 5100 3D system printer

https://support.3dsystems.com/s/article/nextdent-5100-mixing-stirring-and-curing-chart?language=en_US

new text [the resin underwent a homogenization process via agitation within a designated resin agitator (NextDent 5100 LC-3D Mixer) for a duration of five minutes according to manufacturer instructions.]

Comments 8: [**Drying Samples**: Clarify the intent on line 155 to “the samples were dried with compressed air.”]

Response 8: [line 143, 144 ]

Text [Finally, the samples were dried using compressed air to ensure consistent results.]

Comment 9: [**Reference Scan**: Explain why another “reference scan” was done despite having the digitized model.]

Response 9: [Thank you for the comment. the same reference scan utilized, text adjusted to clarify it]

Text change:

[Following preparation, the master die was digitized as a “reference scan” using a desktop scanner (3Shape E3 Dental Lab scanner, 3Shape, Copenhagen, Denmark).]

[The evaluation process commenced with utilizing the “reference scan” of the master die as a reference for comparison.]

Comment 10: **Methodology Choice**: Justify the chosen technique in Figure 1 over other digital methods (DOI:10.1201/9781003217152-73).]

Response 10: [ used 3D superimposition technique]

Both methods assessment techniques are valid and this study compared different techniques and showed no statistically significant differences.

The utilized technique for fit analysis uses silicon material that simulates the cement layer.

Comment 11: [**Scan Comparisons**: Correct the term “fit scan” to “measured scan” or “compared scan” on line 186, and clarify the comparisons made.]

Response 11: adjusted and clarified the text [These alignments facilitated the 185 precise co-registration of the "fit scan" and the "reference scan" for a comprehensive com- 186 parison of their surface geometries.]

new text [" These alignments facilitated the precise co-registration of the "measured data scan" and the "reference scan" for a comprehensive comparison of their surface geometries.

Comment 12: [ **Regions of Interest**: Explain how regions of interest were selected and how consistency was maintained.]

Response 12: clarified further

Adjusted text:  line 178 to 180 [Subsequently, evaluation of the four predefined anatomical regions of interest (ROI) – occlusal, axial, (between occluso-axial line angles and medial borders of marginal area), marginal, (extending 1.0 mm medially from the finish line), and overall.]

Comment 13: [**Units Clarification**: Correct “units” to “millimeters” on line 190.]

Response 13: corrected

Adjusted text [ line 182 to 183 This function employed a color map ranging from positive 0.12 to negative 0.12 mm to visually represent minute dimensional discrepancies between the two scans.]

Comments 14: [ **Cement Spacing**: Justify the decision to not use tolerance values for cement spacing on line 193.]

Response 14: [typing error.]

Adjusted text: line 182 to 185 [This function employed a color map ranging from positive 0.12 to negative 0.12 mm to visually represent minute dimensional discrepancies between the two scans. Finally, an automated report was generated, quantifying the cement gap as the positive average value, which served as the crown's overall fit value]

Comments 15: [**Terminology**: Explain the use of the word “cameo” on line 197.]

Response 15:text [Thank you for the comment]

Adjusted text [Then, the putty was inverted into the intaglio surface to support the crown as the outer surface was scanned]

Comment 16: [**Repeated Information**: Address the repetition in lines 203-210.]

Response 16: [removed and text adjusted]

Text [The "measured data" scans obtained from each individual crown within a group were subjected to a superimposition process, facilitating a visual comparison of their surface geometries. This comparison served to identify potential discrepancies in dimensional fidelity between the crowns. To quantify these discrepancies and assess inter-specimen variability, the Root Mean Square (RMS) value was calculated. A higher RMS value signifies a greater magnitude of dimensional deviations between the compared "measured data" scans, thereby indicating a lower level of overall precision across the crown samples within the group.]

Adjusted text [The "measured data" obtained from each individual crown within a group underwent a superimposition process to enable visual comparison of their surface geometries. This comparison aimed to detect potential differences in dimensional accuracy among the crowns. Each crown scan underwent an “initial alignment” and then "best fit alignment" with the first crown. Discrepancies were quantified to assess inter-specimen variability in regions of interest (ROI) such as occlusal, axial, marginal, and intaglio surfaces. Subsequently, overall values were computed. Then (RMS) value was generated. A higher RMS value indicates greater dimensional deviations between the compared "measured data" scans, suggesting lower overall precision across the crown samples within the group.]

Comment 17: [**Statistical Analysis**: Provide detailed descriptions of the statistical tests used, including normality tests and post-hoc tests.]

Response 17: [adjusted.

text [Statistical analysis was performed using SPSS software (IBM Corp., New York, NY, 211 USA) to assess mean variations between test groups for trueness, precision, internal fit, 212 and marginal adaptation. One-way analysis of variance (ANOVA) was conducted to iden- 213 tify statistically significant differences (p ≤ 0.05) in these parameters between groups. Post- 214 hoc analysis using appropriate correction methods would be employed if significant in- 215 teractions were detected.]

Adjusted text [performed using SPSS software (IBM Corp., New York, NY, USA) to assess mean differences between test groups for trueness, precision, internal fit, and marginal adaptation. The data is normally distributed. One-way analysis of variance (ANOVA) was conducted to identify statistically significant differences (p ≤ 0.05) in these parameters between groups. After that, Post-hoc Tukey’s multiple comparison test analysis using appropriate correction methods would be employed if significance of the mean difference between the groups were detected.]

4. **Results:**

 Comment 1: [**Terminology**: Replace “variances” with “differences” on line 253.]

Resposne1: [done]

Text [Conversely, no statistically significant variances were detected in the axial and intaglio regions (Fig. 4).]

New text [Conversely, no statistically significant differences were detected in the axial and intaglio regions]

Comment 2: [**Graphical Representation**: Include graphical examples, such as boxplots, to present the data more clearly.]

Response 2: [Thank you for the valuable comment. The added samples in the figures are representative samples of the mean of the results of the study]

5. **Discussion:**

Comment 1: [**Scientific Clarity**: Rewrite line 274 to meet the required scientific level.]

Response1: [done]

Text [Suppose a prosthetic crown fails to achieve proper closure. In that case, the marginal gap between the dental structure and the restoration may result in cement dissolution[18, 28] ]

New text [If a prosthetic crown fails to achieve adequate closure, the marginal gap between the dental structure and the restoration could lead to dissolution of the cement used for fixation. [18, 28], microleakage, and the risk of pulp inflammation [14].]

Comment 2: [**Terminology**: Replace “notable variances” with “differences” on line 278.]

Response 2: [done]

Text [Our investigation found no statistically notable variances in the internal fit and marginal adaptation of printed crowns created using (VSCP) compared to those made with (C). Similarly, no significant disparities were observed when comparing printed crowns (VSCP, C) to milled crowns manufactured from (E).]

New text [Our investigation found no statistically significant differences in the internal fit and marginal adaptation of printed crowns created using (VSCP) compared to those made with (C). Similarly, no significant differences were observed when comparing printed crowns (VSCP, C) to milled crowns manufactured from (E).]

Comment 3: [**Term Usage**: Replace “closure with a gap” with “marginal fit” on line 285.]

Response 3:[ done.]

Text [several studies have indicated that an ideal 284 outcome would involve achieving closure with a gap of under 25 μm [15, 16, 24].]

New text [Several studies have indicated that an ideal outcome would involve achieving marginal fit of under 25 μm [15, 16, 24].]

Comment 4: [**Clinical Acceptability**: Specify which clinical misfit standards were used on line 287.]

Response 4: [added]

Text [Our investigation found no statistically notable variances in the internal fit and mar- 278 ginal adaptation of printed crowns created using (VSCP) compared to those made with 279 (C). Similarly, no significant disparities were observed when comparing printed crowns 280 (VSCP, C) to milled crowns manufactured from (E). ]

New text [Our investigation found no statistically significant differences in the internal fit and marginal adaptation of printed crowns created using (VSCP) compared to those made with (C). Similarly, no significant differences were observed when comparing printed crowns (VSCP, C) to milled crowns manufactured from (E) noting that the the 3D-superimposition digital method.]

Comment 5:[**Relevance of Findings**: Ensure the pertinence of findings is discussed. Confirm that there is only one supporting article in the literature.

Response 5: [Thank you for the valuable comment.

Comment 6: [**Terminology**: Replace “printer chamber” with “printer bed” on line 369.]

Response 6: [done]

Text:[ the spatial arrangement of the crowns within the printing chamber, the post-processing methodolo gies implemented, and the design and placement optimization of support structures. [8, 9, 11, 28-32].]

New text [), the printer's operating wavelength, the overall restoration thickness and die-spacer thickness, the spatial arrangement of the crowns within the printing bed, the post-processing methodologies implemented, and the design and placement optimization of support structures. [8, 9, 11, 28-32]. 

Comment 7: [**Shrinkage Consideration**: Address whether shrinkage over time was considered on line 374.]

Response 7: [revised and re written]

New text [Furthermore, achieving high precision in photopolymerizable 3D printing is inherently limited by the maximum projection size, restricting the fabrication of large objects. Additionally, volume shrinkage during the curing process technique and shrinkage over time remains a well-documented drawback associated with this resin-based additive manufacturing [21].]

Comment 8: [**Limitations**: Expand the limitations section to address potential biases and suggest future study mitigations.]

Response 8: [added]

New text [Among the limitations of this study is that it uses only one method to assess the fit and tests the samples in static conditions for fit without subjecting them to cyclic loading or thermal conditions. There are no potential biases in this research. Recommendations for future studies include changing the orientation of printing and the post-processing curing time, testing the samples under cyclic loading or thermos cycling, and comparing the results.]

Comment 9: [**Supplementary Materials**: Include detailed statistical outputs and additional data (e.g., raw measurements, fit scans) for transparency and reproducibility.]

Response 9: [ will be sent]