Accuracy of Chairside Fabricated Endocrowns Using Two Milling Machines and Two Glass Ceramic Materials (in-vitro study)

Accuracy of Chairside Fabricated Endocrowns Using Two Milling Machines and Two Glass Ceramic Materials (in-vitro study) | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Accuracy of Chairside Fabricated Endocrowns Using Two Milling Machines and Two Glass Ceramic Materials (in-vitro study) Aya Mohsen, Doaa Taha, Amr Saleh El-Etreby This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6378763/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 18 You are reading this latest preprint version Abstract Background : The accuracy of chairside-manufactured restorations plays a vital role in ensuring the long-term success of endocrown restorations. Factors, such as the type of ceramic material and the milling technique, need to be thoroughly examined to understand their impact on fabrication accuracy in dental offices. Materials and Methods : A typodont model of a maxillary right first molar was prepared for an endocrown restoration, digitally scanned, and designed using CEREC CAD software. A total of 40 endocrowns were fabricated based on the reference design from two materials. Group (E) utilized IPS Emax CAD (N=20), and group (T) used Tessera CEREC blocks (N=20); 10 of each group were milled using MCXL (EX), and the other 10 were milled using primemill (EP), and the same for Tessera (TX) and (TP). All fabricated endocrowns were scanned, and test data were collected in standard tessellation language (STL) format. These datasets, along with the reference design, were compared using reverse engineering software to evaluate the 3D trueness and precision of the fabricated restorations. Data were analyzed using two-way ANOVA. The significance level was set at p<0.05 within all tests. Statistical analysis was performed with R statistical analysis software version 4.4.1 for Windows. [1] Results : Root mean square (RMS) values were used to evaluate the 3D trueness and precision between tests. No significant differences in trueness were found between Tessera and Emax samples milled with Primemill (p=0.488) or MCXL (p=0.437). Similarly, no notable differences were observed between Emax (p=0.593) or Tessera (p=0.537) samples milled by either machine. For precision, Emax and Tessera samples milled with MCXL showed no significant difference (p=0.827). However, Tessera samples milled with Primemill had higher precision (23.46±2.03 µm) than Emax (32.81±4.35 µm) (p<0.001). Primemill also produced more precise Emax (p<0.001) and Tessera (p<0.001) samples compared to MCXL. Conclusion : The two milling systems offer comparable accuracy for restoration fabrication, ensuring clinical reliability for chairside use. However, the Primemill machine showed superior precision in fabricating Endocrown restorations compared to the MCXL, suggesting that advancements in milling technology, like improved calibration and milling algorithms, enhance consistency and precision. [1] R Core Team (2024). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL https://www.R-project.org/. Endocrown Accuracy CEREC Tessera IPS emax cad chairside milling machine Primemill MCXL milling machine CAD/CAM Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Background Attaining an accurate restoration with well-defined internal fit, marginal adaption, and proximal contact is vital for minimizing the need for significant intraoral adjustment critical for their long-term clinical success since poorly fitting restorations may cause marginal gaps, decreased retention, biofilm accumulation, and the formation of secondary caries (1-5). Additionally, the accuracy of various fabrication methods is crucial for creating restorations that precisely match their planned design (6, 7). Advancements in digital manufacturing technologies have greatly influenced the dental field, enabling the production of dental restorations with well-defined occlusal and proximal contacts, margins, and intaglio fit (3, 7, 8). Computer-Aided Design and Computer-Aided Manufacturing (CAD/CAM) is now a widely accepted method for fabricating dental restorations, particularly for all-ceramic restorations; it overcomes the inaccuracies associated with traditional techniques, resulting in restorations with enhanced accuracy (9, 10). Subtractive techniques utilize milling machines with software-controlled burs to mechanically shape blocks or disks into the desired geometry, ensuring a more consistent process and enhancing the accuracy of final restorations. Moreover, This approach facilitates on-demand chairside fabrication, decreasing patient visits and expediting the delivery of dental restorations (11, 12). Ceramics have emerged as the preferred restorative material due to their esthetic properties, inert nature, and compatibility with biological tissues. The growing interest in glass ceramics within the dental field is due to their advantageous physical and mechanical properties. This includes excellent aesthetics, translucency, low thermal conductivity, biocompatibility, sufficient strength, durability, and chemical stability (13). IPS E-max CAD is recognized as the gold standard, having been introduced in 2006 as a lithium disilicate glass-ceramic tailored for the CAD/CAM workflow (14). This resulted in the introduction of other versions becoming available in the market, including Chairside Economical Restoration of Aesthetic Ceramic as CEREC Tessera (15). 3D comparative analysis is a well-established method in engineering and is also utilized to evaluate the accuracy of digital impressions and virtual models in dentistry (16-19). This method detects 3D variations between virtual models by aligning two digital datasets using a best-fit algorithm. The reliability of these measurements is assessed based on trueness and precision (20). Trueness refers to the degree of deviation of the measured data from the reference object or reference data, whereas precision reflects the consistency and reproducibility of the measurements (21). Accordingly, this study aimed to assess the accuracy of chairside-fabricated endocrowns using two milling machines (MCXL and Primemill milling machines) and two glass ceramic materials (E-max CAD and Tessera CEREC blocks). The null hypothesis proposed that the trueness and precision of the fabricated endocrowns would remain unaffected by the milling machine or the type of glass ceramic material used. Materials And Methods The sample size was calculated by using R statistical analysis software version 4.4.2. (Figure 1) Illustrates a schematic presentation of the study methodology. A typodont model of a maxillary right first molar (Nissin Dental Product) was used for the preparation of an endocrown restoration. The preparation followed the standard guidelines for endocrown design, incorporating a 1.5 mm circumferential butt joint margin occlusally and a central retention area corresponding to the pulp chamber with a depth of 4 mm (22) was employed. For the fabrication of endocrown patterns, the typodont model was digitally scanned using an intraoral scanner (CEREC Omnicam; Dentsply Sirona) (Figure 2). The restoration was then designed with CEREC CAD software (CEREC Omnicam; Dentsply Sirona) and exported in standard tessellation language (STL) format to serve as both the reference design and the basis for fabricating the endocrown restorations. The design was used for the fabrication of endocrowns (N=40) from two materials. Group (E) utilized IPS Emax CAD (N=20), and group (T) used Tessera CEREC blocks (N=20); 10 of each group were milled using MCXL (EX), and the other 10 were milled using primemill (EP), and the same for Tessera (TX) and (TP). The STL file of the endocrown design was imported into the CAM software for processing by a 4-axis chairside milling unit (MCXL and Primemill) for subtractive manufacturing of endocrowns (Figure 3). All the fabricated specimens were checked on the corresponding preoperative cast for evaluation of sample seating; no modifications were made to the internal surfaces of the endocrowns. An intraoral scanner (CEREC Omnicam; Dentsply Sirona) was used to capture digital scans of all fabricated endocrowns, producing an STL file as test data for each endocrown pattern. The scans included both the external and intaglio surfaces, including the margins, axial, and occlusal areas. The intraoral scanner was calibrated before scanning each group. The 3D trueness (intergroup comparison) was evaluated by importing the STL files of the test data and reference design into reverse engineering software (Geomagic Control X 2020; 3D Systems, Inc.). The root mean square (RMS) values were calculated using the "best fit alignment" and "3D analysis" tools. The deviations between the fabricated endocrowns and the reference design were analyzed across multiple points in 3D space (x-, y-, and z-axes). A color map was created to visualize these deviations, ranging from a maximum of 0.5 mm to a minimum of -0.5 mm, without applying any specific tolerance settings. The green color denoted a precise match between surfaces, red indicated that the test model surface was shifted positively relative to the reference model, and blue represented a negative shift of the test model surface in relation to the control model (figure 4). Precision (intragroup comparison) was calculated by RMS divisions within each group. Each scan was used as a reference, and the other nine scans within the same group were aligned to it, resulting in a total of 45 reports per group. Numerical data are expressed as mean and standard deviation values and were assessed for normality using the Shapiro-Wilk test. Translucency The data were evaluated through a two-way analysis of variance (ANOVA). Simple effects were compared using the pooled error term from the main ANOVA model. P-values were modified for multiple comparisons using the False Discovery Rate (FDR) method, with a significance threshold of p<0.05 applied to all tests. Statistical analysis was performed with R statistical analysis software. Results For the 3D trueness assessment, average RMS values were calculated to represent the 3D trueness (µm). The RMS values, indicating the deviations between the scans of the fabricated endocrowns and the reference design, are provided in (Table 1). No statistically significant difference in trueness was observed between Tessera samples and Emax samples fabricated using Primemill (p=0.488) or using MCXL (p=0.437). Furthermore, no statistically significant difference in trueness was found between Emax samples milled using MCXL (43.36±5.17) (µm) and those milled using Primemill (44.88±4.28) (µm) (p=0.593). Also, no statistically significant difference between Tessera samples milled using MCXL (41.14±2.01) (µm) and those milled using Primemill (42.90±5.34) (µm) (p=0.537) (Figure 5). Table (1) Mean RMS values of 3D trueness (µm) for different materials and milling machines. Milling machine Trueness (RMS) (µm) (Mean±SD) p-value MCXL Primemill Emax 43.36±5.17 44.88±4.28 0.593ns Tessera 41.14±2.01 42.90±5.34 0.537ns p-value 0.437ns 0.488ns ns (not significant) RMS (root mean square) SD (standard division) Translucency data were analyzed using two-way ANOVA. Statistical analysis was performed with R statistical analysis software. For precision measurements, the average RMS values reflected the deviations between the scans of the fabricated endocrowns per each group, as shown in (Table 2). No statistically significant difference within Emax samples (40.85±5.18) (µm) and Tessera samples (41.25±4.03) (µm) milled using MCXL (p=0.827). However, Tessera samples had significantly higher precision (23.46±2.03) (µm) than Emax (32.81±4.35) (µm) (p<0.001) when milled using Primemill. Additionally, Emax samples milled with Primemill had higher precision (32.81±4.35) (µm) than those milled with MCXL (40.85±5.18) (µm) (p<0.001). Also, Tessera samples milled with Primemill had higher precision (23.46±2.03) (µm) than those milled with MCXL (41.25±4.03) (µm) (p<0.001) (Figure 6). Table (2) Mean RMS values of 3D precision (µm) for different materials and milling machines. Milling machine Precision (RMS) (µm) (Mean±SD) p-value MCXL Primemill Emax 40.85±5.18 32.81±4.35 <0.001* Tessera 41.25±4.03 23.46±2.03 <0.001* p-value 0.827ns <0.001* * Significant ns (not significant) RMS (root mean square) SD (standard division) Translucency data were analyzed using two-way ANOVA. Statistical analysis was performed with R statistical analysis software. Discussion The incorporation of digital technologies into restorative dentistry has made CAD/CAM systems indispensable for producing high-quality dental restorations. These systems provide various applications that improve clinical efficiency and accuracy (7, 8).The fabrication accuracy of endocrowns is significantly affected by the type of ceramic material used, such as IPS Emax CAD, which is widely preferred in clinical practice for its outstanding esthetic qualities and mechanical strength. Alternatively, Tessera CEREC blocks provide a new potential to the ceramic market (14, 23). Additionally, the choice of milling machine is essential in achieving high trueness and precision in the restoration and should be assessed and considered. This study analyzed the accuracy of chairside-manufactured endocrowns using two milling machines and two types of ceramic materials. The primary focus was to determine the impact of these variables on the restoration's 3D dimensional accuracy, which directly influences clinical performance. The results of trueness evaluation revealed no statistically significant difference in the 3D trueness of restorations between samples milled using MCXL and Primemill (P > 0.05). The lack of significant differences in trueness between the milling machines and materials owes to advancements in modern chairside CAD/CAM systems. Regardless of the specific machine or material, CAD/CAM systems offer a high degree of accuracy in replicating digital designs for dental restorations. In addition, the software improvement of the milling machine and milling technology has minimized discrepancies and enhanced accuracy, provided that all other variables are standardized, such as the condition of the milling bur and cooling system, leading to uniformity in the trueness of restorations produced by different systems (24, 25). Moreover, material type may have a minimal impact on trueness under similar milling conditions, especially within the same category of ceramic material (26) as type of material is not the sole factor influencing the accuracy of CAD-CAM-milled crowns (27). On the contrary, a different study opposed our findings, stating that both the type of ceramic material and the milling machine had a significant impact on the trueness of the milled restorations. Their results may be attributed to the material's properties, calibration of the intraoral scanner and milling machine, software design parameters, margin placement on the virtual model, and the operator's experience, which are some of the factors that can influence the accuracy of fabricated restorations (28). The present data provided no significant difference in 3D trueness between samples milled using IPS E-max CAD and Tessera CEREC blocks (P>0.05). This data is in agreement with the findings of Canals et al., who stated that advanced lithium disilicate ceramics exhibit similar or slightly improved accuracy compared to traditional lithium disilicate ceramics, with no statistically significant difference (29). On the other side, a different study implicated that IPS Emax CAD crowns exhibited superior accuracy compared to Tessera CEREC crowns. This outcome may be linked to a longer period of grinding process, and the higher density of the material attributed to the difficulty in grinding, which affects the accuracy (30) . Considering the results of the 3D evaluation of the precision of the milling machines, the findings indicate that the precision varied significantly between the two milling machines (P<0.001), as the Primemill outperformed the MCXL regardless of ceramic materials. The modern milling units equipped with advanced calibration systems achieve higher precision in dental restorations. Where the improvement in technological advancements, such as refined milling strategies and better control over the milling burs movement, helps in minimizing variability during the manufacturing process (31). However, MCXL, an older model, may lack some of these refined capabilities, resulting in less consistent precision outcomes (25). The optimized milling algorithms and enhanced control of the milling bur’s movement reduced fabrication process discrepancies, resulting in a significantly higher 3D precision. Moreover, a report was done on the precision between different milling machine that showed that the accuracy of the restoration was influenced by the operator's expertise and software optimization, regardless of the milling machine's built-in capabilities. This misalignment between our results and the mentioned study could stem from variations in operator experience and the specific calibration and maintenance of the milling units, factors that were not controlled in this research (32). This study demonstrated a significant difference in precision based on the type of glass ceramic material used. While both materials performed well, Tessera showed better precision than IPS E-max CAD (P<0.001). Within the Primemill group, Tessera exhibited better precision than IPS Emax CAD (P<0.001). These findings indicate that the type of ceramic material may influence the consistency of milling outcomes, even when using a high-precision milling machine. The superior precision of Tessera could be attributed to its unique material properties. For instance, the microstructure and optimized milling parameters allow precise CAD/CAM-fabricated restorations (33, 34). The lack of significant differences between Tessera and IPS Emax CAD in the MCXL group in our study (P>0.05) pointed out that the limitations of the milling machine itself may overshadow the material-specific advantages (35, 36). This was consistent with the findings of Alghazzawi et al. Whose research reported that older milling machines may lack the capability to exploit the full potential of advanced ceramic materials. Besides, their study concluded that while material properties play a crucial role, the milling machine's performance is often the primary factor in achieving high precision (35). Accordingly, even with superior material properties, the precision outcomes may not show significant differences if the machine's inherent limitations are a determining factor (36). A study done by Rezaie et al. contradicted our results and showed no significant differences in precision between ceramic materials when using advanced milling systems. Rezaie et al. data could be returned to the differences in the milling parameters, such as bur wear or cooling protocols, which could influence the material removal process and, subsequently, the precision of the restorations (37). Their data was also supported by Kirsch et al. (2017), who found that newer milling machines do not necessarily produce more precise restorations than older models (38). Moreover, a study by Roperto et al. (2016) revealed no significant differences in marginal gaps between restorations milled with two different chairside milling machines, indicating that improvements in milling technology do not necessarily enhance restoration accuracy (39). The ongoing in-vitro study revealed no significant differences in trueness across various milling machines and materials. Additionally, within the Primemill group, Tessera exhibited better precision than IPS Emax CAD, while no notable difference was observed among the materials within the MCXL group. This study examined only two ceramic materials to fabricate endocrown restorations. The findings could differ when using other types of ceramic materials, which would require different milling protocols and milling machines. It is recommended to investigate and explore other parameters that could affect the accuracy of chairside-manufactured endocrowns. Conclusion Taking into account the limitation of this in vitro study, the following conclusions can be inferred: Both milling machines can achieve a comparable level of accuracy in fabrication of restoration, supporting their clinical reliability for chairside fabrication. Endocrown restoration fabricated using Primemill machine demonstrated superior precision compared to those fabricated using MCXL, regardless of the material used. This suggests that advancements in milling technology, such as improved calibration and enhanced milling algorithms in newer machines like Primemill, contribute to greater consistency in restoration fabrication. While both older and newer milling machines can provide high trueness, newer systems like Primemill offer improved precision, which may reduce the risk of restorative failures and enhance clinical outcomes. The choice of material, such as Tessera with Primemill, can further optimize precision and consistency. The selection of ceramic material properties, in combination with the milling machine, can affect precision, highlighting the importance of selecting the appropriate machine-material combination for optimal results. Abbreviations CAD/CAM Computer aided design and computer aided manufacturing STL Standard tessellation language RMS Root mean square FDR False Discovery Rate P P-value µm Micrometer ANOVA analysis of variance Declarations Ethics approval and consent to participate Not applicable Consent for publication Not applicable Availability of data and materials The data and resources utilized in this study can be obtained from the corresponding author upon reasonable request. Competing interests The authors confirm that they have no competing interests. Funding The authors state that no organization provided funding for this research. Author’s contributions AMI conducted the methodology and authored the manuscript. DTS and ASE supervised the study and reviewed the manuscript. All authors reviewed and approved the final form of the manuscript. Acknowledgements Not applicable. Author’s information Department of Fixed Prosthodontics, Faculty of Dentistry, Badr University in Cairo, Cairo, Egypt. Aya Mohsen Ibrahim Department of Fixed Prosthodontics, Faculty of Dentistry, Ain Shams University, Organization of African Unity, Cairo, Egypt. Amr Saleh El-Etreby Department of Fixed Prosthodontics, Faculty of Dentistry, New Giza University, Ain Shams University, Cairo, Egypt Doaa Taha Sayed Taha References Jang Y, Sim J-Y, Park J-K, Kim W-C, Kim H-Y, Kim J-H. Evaluation of the marginal and internal fit of a single crown fabricated based on a three-dimensional printed model. The journal of advanced prosthodontics. 2018;10(5):367-73. https://pubmed.ncbi.nlm.nih.gov/30370028/ Carbajal Mejía JB, Yatani H, Wakabayashi K, Nakamura T. Marginal and internal fit of CAD/CAM crowns fabricated over reverse tapered preparations. Journal of Prosthodontics. 2019;28(2):e477-e84. https://pubmed.ncbi.nlm.nih.gov/29194841/ Giannetti L, Apponi R, Mordini L, Presti S, Breschi L, Mintrone F. The occlusal precision of milled versus printed provisional crowns. Journal of Dentistry. 2022;117:103924. https://pubmed.ncbi.nlm.nih.gov/34910962/ Felton D, Kanoy B, Bayne Sa, Wirthman G. Effect of in vivo crown margin discrepancies on periodontal health. The Journal of prosthetic dentistry. 1991;65(3):357-64. https://pubmed.ncbi.nlm.nih.gov/2056454/ Sjögren G. Marginal and internal fit of four different types of ceramic inlays after luting An in vitro study. Acta Odontologica Scandinavica. 1995;53(1):24-8. https://pubmed.ncbi.nlm.nih.gov/7740927/ Bassiouny D, Petersmann S, Zohdy M, Morsi T, Taha D. Trueness and intaglio fit of custom-made polyetheretherketone post-and-cores fabricated using different techniques. The Journal of Prosthetic Dentistry. 2024. https://doi.org/10.1016/j.prosdent.2024.06.026 Taha D, Allam S, Morsi T. Accuracy of computer-aided design trial restorations fabricated with different digital workflows. The Journal of Prosthetic Dentistry. 2024;132(3):578-85. https://pubmed.ncbi.nlm.nih.gov/37925250/ Onlay LDP. Marginal and internal gap of handmade, milled and 3D printed additive manufactured patterns for pressed lithium disilicate onlay restorations. European Journal of Prosthodontics and Restorative Dentistry. 2018;26:31-8. https://pubmed.ncbi.nlm.nih.gov/29461746/ Hamza TA, Sherif RM. In vitro evaluation of marginal discrepancy of monolithic zirconia restorations fabricated with different CAD-CAM systems. The Journal of prosthetic dentistry. 2017;117(6):762-6. https://pubmed.ncbi.nlm.nih.gov/27836145/ Reddy AN, Ramesh D. Studies on Impact Strength of Concrete with Nano-Materials at Elevated Temperatures. Int J Sci Res &Devlp. 2015;3(9):40-4. https://www.researchgate.net/publication/339130560_Studies_on_Impact_Strength_of_Concrete_with_Nano-Materials_at_Elevated_Temperatures Davidowitz G, Kotick PG. The use of CAD/CAM in dentistry. Dental Clinics of North America. 2011;55(3):559-ix. https://pubmed.ncbi.nlm.nih.gov/21726690/ Miyazaki T, Hotta Y, Kunii J, Kuriyama S, Tamaki Y. A review of dental CAD/CAM: current status and future perspectives from 20 years of experience. Dental materials journal. 2009;28(1):44-56. https://pubmed.ncbi.nlm.nih.gov/19280967/ Ritzberger C, Apel E, Höland W, Peschke A, Rheinberger VM. Properties and clinical application of three types of dental glass-ceramics and ceramics for CAD-CAM technologies. Materials. 2010;3(6):3700-13. https://doi.org/10.3390/ma3063700 Zarone F, Ferrari M, Mangano FG, Leone R, Sorrentino R. “Digitally oriented materials”: focus on lithium disilicate ceramics. International journal of dentistry. 2016;2016(1):9840594. https://pubmed.ncbi.nlm.nih.gov/27635140/ ZULKIFFLI S, TAKE YO, YAHYA NA, KUTTY MG. Evaluation and Comparison of Mechanical Properties of Lithium Disilicate-Based. Sains Malaysiana. 2024;53(1):217-29. https://www.ukm.my/jsm/pdf_files/SM-PDF-53-1-2024/17.pdf Ender A, Mehl A. In-vitro evaluation of the accuracy of conventional and digital methods of obtaining full-arch dental impressions. Quintessence international. 2015;46(1). https://pubmed.ncbi.nlm.nih.gov/25019118/ Güth J-F, Edelhoff D, Schweiger J, Keul C. A new method for the evaluation of the accuracy of full-arch digital impressions in vitro. Clinical oral investigations. 2016;20:1487-94. https://doi.org/ 10.1007/s00784-015-1626-x Park J-M. Comparative analysis on reproducibility among 5 intraoral scanners: sectional analysis according to restoration type and preparation outline form. The Journal of Advanced Prosthodontics. 2016;8(5):354-62. https://doi.org/ 10.4047/jap.2016.8.5.354 Zimmermann M, Ender A, Mehl A. Local accuracy of actual intraoral scanning systems for single-tooth preparations in vitro. The Journal of the American Dental Association. 2020;151(2):127-35. https://doi.org/ 10.1016/j.adaj.2019.10.022 Bosch G, Ender A, Mehl A. A 3-dimensional accuracy analysis of chairside CAD/CAM milling processes. The Journal of prosthetic dentistry. 2014;112(6):1425-31. https://www.sciencedirect.com/science/article/abs/pii/S002239131400256X Al Hamad KQ, Al‐Rashdan RB, Al‐Rashdan BA, Baba NZ. Effect of milling protocols on trueness and precision of ceramic crowns. Journal of Prosthodontics. 2021;30(2):171-6. https://doi.org/ 10.1111/jopr.13245 Hayes A, Duvall N, Wajdowicz M, Roberts H. Effect of endocrown pulp chamber extension depth on molar fracture resistance. Operative dentistry. 2017;42(3):327-34. https://doi.org/ 10.2341/16-097-L Dartora NR, Moris ICM, Poole SF, Bacchi A, Sousa-Neto MD, Silva-Sousa YT, Gomes EA. Mechanical behavior of endocrowns fabricated with different CAD-CAM ceramic systems. The Journal of Prosthetic Dentistry. 2021;125(1):117-25. https://doi.org/ 10.1016/j.prosdent.2019.11.008 Jivanescu A, Codruta I, Rotar R. Chairside CAD/CAM Restorations. 2024. https://doi.org/ 10.5772/intechopen.114090 Pilecco RO, Machry RV, Baldi A, Tribst JPM, Sarkis-Onofre R, Valandro LF, et al. Influence of CAD-CAM milling strategies on the outcome of indirect restorations: A scoping review. The Journal of Prosthetic Dentistry. 2024. https://doi.org/ 10.1016/j.prosdent.2024.02.021 Demirel M, Donmez MB. Fabrication trueness and internal fit of different lithium disilicate ceramics according to post-milling firing and material type. Journal of dentistry. 2024;144:104987. https://doi.org/10.1016/j.jdent.2024.104987 Fayed AK, Azer AS, AboElhassan RG. Fit accuracy and fracture resistance evaluation of advanced lithium disilicate crowns (in-vitro study). BMC Oral Health. 2025;25(1):58. https://bmcoralhealth.biomedcentral.com/articles/10.1186/s12903-024-05325-z Kunkela J, Ingr T, Komarek A. Evaluation of marginal gap of teeth restored with crowns using six different CAD/CAM materials milled with two different milling units. International Journal of Computerized Dentistry. 2021;24(2):195-205. PMID: 34085504 Perez Canals M. Marginal Fit of CAD/CAM Crowns Milled From Two Different Ceramic Materials: Lithium Disilicate and Advanced Lithium Disilicate: University of Pittsburgh; 2023. http://d-scholarship.pitt.edu/id/eprint/44951 Yamamoto K, Murata Y, Nagaoka K, Akiyama S, Hokii Y, Fusejima F. Comparison of dimensional accuracy of lithium disilicate CAD/CAM ceramics. Journal of Osseointegration. 2022;14(4):205-8. https://doi.org/10.23805/JO.2022.14.04.2 Al-Hassiny A. Fundamentals of Computer-Aided Design (CAD) in Dental Healthcare: From Basics to Beyond. 3D Printing in Oral Health Science: Applications and Future Directions: Springer; 2022. p. 93-119. https://www.researchgate.net/publication/363873876_Fundamentals_of_Computer-Aided_Design_CAD_in_Dental_Healthcare_From_Basics_to_Beyond Beuer F, Aggstaller H, Edelhoff D, Gernet W, Sorensen J. Marginal and internal fits of fixed dental prostheses zirconia retainers. Dental Materials. 2009;25(1):94-102. https://www.sciencedirect.com/science/article/abs/pii/S0109564108001450 Nassar HS, Abo El-Mal EO. In Vitro Evaluation of The Marginal Adaptation of Monolithic Ceramic Crowns Fabricated with Different Margin Designs Using Novel CAD/CAM Material After Thermomechanical Aging. Egyptian Dental Journal. 2024;70(1):575-85. https://journals.ekb.eg/article_334133.html Rekow E, Silva N, Coelho P, Zhang Y, Guess P, Thompson V. Performance of dental ceramics: challenges for improvements. Journal of dental research. 2011;90(8):937-52. https://journals.sagepub.com/doi/abs/10.1177/0022034510391795 Alghazzawi TF. Advancements in CAD/CAM technology: Options for practical implementation. Journal of prosthodontic research. 2016;60(2):72-84. https://www.sciencedirect.com/science/article/abs/pii/S1883195816000098 Schmidt J, Marques MR, Botti S, Marques MA. Recent advances and applications of machine learning in solid-state materials science. npj computational materials. 2019;5(1):83. https://www.nature.com/articles/s41524-019-0221-0 Rezaie F, Farshbaf M, Dahri M, Masjedi M, Maleki R, Amini F, et al. 3D printing of dental prostheses: Current and emerging applications. Journal of composites science. 2023;7(2):80. https://www.mdpi.com/2504-477X/7/2/80 Kirsch C, Ender A, Attin T, Mehl A. Trueness of four different milling procedures used in dental CAD/CAM systems. Clinical oral investigations. 2017;21:551-8. https://link.springer.com/article/10.1007/s00784-016-1916-y Roperto R, Assaf H, Soares-Porto T, Lang L, Teich S. Are different generations of CAD/CAM milling machines capable to produce restorations with similar quality? Journal of clinical and experimental dentistry. 2016;8(4):e423. https://pmc.ncbi.nlm.nih.gov/articles/PMC5045690/ Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6378763","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":467211474,"identity":"839174c3-bad6-4727-bd71-1b0a7db8db5d","order_by":0,"name":"Aya Mohsen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAklEQVRIiWNgGAWjYBACNiBm5mE4AKKOQYQOENDCD1I7B6yMLY04LZINQC1/wMp4zIjTYnAj+QFzTsUde37pnm+PeWoY5PhuJDA+/IJXS5oBc86ZZ4kz55zdbsxzjMFY8kYCs7EMXi0JBsy5bYcTDG7kbpPmbWBI3HAjgU1aAo8W+xvpH5h52w7b29/IeQbSUg/Uwv4bnxaDGzkGIC2MGyRy2EBagNYlsDF+wKflzJuCwzxnDifOuJFmbjjnmIThzDMPm6Xx6GAwOJ6+8TFPxWF7/hnJzx68qbGR5zuefPDjD3x6BBJQIgLkCcYGYHrAA/gPYBFkxGvLKBgFo2AUjDQAAHdzVFPUAVZfAAAAAElFTkSuQmCC","orcid":"","institution":"Badr University in Cairo","correspondingAuthor":true,"prefix":"","firstName":"Aya","middleName":"","lastName":"Mohsen","suffix":""},{"id":467211475,"identity":"5fea08bf-7b62-4438-9c00-7e70716e7d1a","order_by":1,"name":"Doaa Taha","email":"","orcid":"","institution":"Ain Shams University","correspondingAuthor":false,"prefix":"","firstName":"Doaa","middleName":"","lastName":"Taha","suffix":""},{"id":467211476,"identity":"dd1730d8-8cad-4a48-aefa-151d0466adda","order_by":2,"name":"Amr Saleh El-Etreby","email":"","orcid":"","institution":"Ain Shams University","correspondingAuthor":false,"prefix":"","firstName":"Amr","middleName":"Saleh","lastName":"El-Etreby","suffix":""}],"badges":[],"createdAt":"2025-04-04 21:08:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6378763/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6378763/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":84243279,"identity":"d1a71c74-2bd2-4177-9cb8-cef97411e461","added_by":"auto","created_at":"2025-06-09 16:13:06","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":78631,"visible":true,"origin":"","legend":"\u003cp\u003eStudy methodology\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6378763/v1/0f727f6f003a2f9857270905.png"},{"id":84243372,"identity":"f2ebd68e-2c04-47c3-b2b7-fd1eff735ebb","added_by":"auto","created_at":"2025-06-09 16:13:12","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":230377,"visible":true,"origin":"","legend":"\u003cp\u003eA) Preparation of upper first right molar B) Scanning of the sample.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6378763/v1/564f405a4781900e4303ebcc.png"},{"id":84243371,"identity":"9514d333-7e0b-4ad9-97ee-31e7392ffd6c","added_by":"auto","created_at":"2025-06-09 16:13:12","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":148780,"visible":true,"origin":"","legend":"\u003cp\u003eMilled Endocrown pattern A) Occlusal surface, B) Inner surface, C) Proximal surface\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6378763/v1/6686c7235b7b2a1fca6636fa.png"},{"id":84243460,"identity":"84fed1ae-d70c-4f51-a698-6164f5fe8f44","added_by":"auto","created_at":"2025-06-09 16:13:17","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":117917,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic presentation showing steps of 3D comparison of fabricated endocrown restoration.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6378763/v1/06231d40c24c437e3e1323b1.png"},{"id":84243418,"identity":"fbaccfec-ca07-47c3-a5d6-6bee5a1f1f3a","added_by":"auto","created_at":"2025-06-09 16:13:13","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":14434,"visible":true,"origin":"","legend":"\u003cp\u003eBar chart showing average trueness (RMS) (µm) for different materials and milling machines (A)\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6378763/v1/edcdd44e1458b82ceb773514.png"},{"id":84243490,"identity":"998017f6-2f8d-4e84-a716-17ff315e96f9","added_by":"auto","created_at":"2025-06-09 16:13:18","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":14147,"visible":true,"origin":"","legend":"\u003cp\u003eBar chart showing average precision (RMS) (µm) for different materials and milling machines (A)\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6378763/v1/a43eb13d84caa37bc74c3d45.png"},{"id":84243523,"identity":"89e92e67-997e-4275-ab86-8ab7a9b85a17","added_by":"auto","created_at":"2025-06-09 16:13:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1255329,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6378763/v1/cbfeeee9-7fe9-4783-b14a-67312139e9da.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Accuracy of Chairside Fabricated Endocrowns Using Two Milling Machines and Two Glass Ceramic Materials (in-vitro study)","fulltext":[{"header":"Background","content":"\u003cp\u003eAttaining an accurate restoration with well-defined internal fit, marginal adaption, and proximal contact is vital for minimizing the need for significant intraoral adjustment critical for their long-term clinical success since poorly fitting restorations may cause marginal gaps, decreased retention, biofilm accumulation, and the formation of secondary caries (1-5). Additionally, the accuracy of various fabrication methods is crucial for creating restorations that precisely match their planned design (6, 7).\u003c/p\u003e\n\u003cp\u003eAdvancements in digital manufacturing technologies have greatly influenced the dental field, enabling the production of dental restorations with well-defined occlusal and proximal contacts, margins, and intaglio fit (3, 7, 8). Computer-Aided Design and Computer-Aided Manufacturing (CAD/CAM) is now a widely accepted method for fabricating dental restorations, particularly for all-ceramic restorations; it overcomes the inaccuracies associated with traditional techniques, resulting in restorations with enhanced accuracy (9, 10).\u003c/p\u003e\n\u003cp\u003eSubtractive techniques utilize milling machines with software-controlled burs to mechanically shape blocks or disks into the desired geometry, ensuring a more consistent process and enhancing the accuracy of final restorations. Moreover, This approach facilitates on-demand chairside fabrication, decreasing patient visits and expediting the delivery of dental restorations (11, 12).\u003c/p\u003e\n\u003cp\u003eCeramics have emerged as the preferred restorative material due to their esthetic properties, inert nature, and compatibility with biological tissues. The growing interest in glass ceramics within the dental field is due to their advantageous physical and mechanical properties. This includes excellent aesthetics, translucency, low thermal conductivity, biocompatibility, sufficient strength, durability, and chemical stability (13). IPS E-max CAD is recognized as the gold standard, having been introduced in 2006 as a lithium disilicate glass-ceramic tailored for the CAD/CAM workflow (14). This resulted in the introduction of other versions becoming available in the market, including Chairside Economical Restoration of Aesthetic Ceramic as CEREC Tessera (15).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e3D comparative analysis is a well-established method in engineering and is also utilized to evaluate the accuracy of digital impressions and virtual models in dentistry (16-19). This method detects 3D variations between virtual models by aligning two digital datasets using a best-fit algorithm. The reliability of these measurements is assessed based on trueness and precision (20). Trueness refers to the degree of deviation of the measured data from the reference object or reference data, whereas precision reflects the consistency and reproducibility of the measurements (21).\u003c/p\u003e\n\u003cp\u003eAccordingly, this study aimed to assess the accuracy of chairside-fabricated endocrowns using two milling machines (MCXL and Primemill milling machines) and two glass ceramic materials (E-max CAD and Tessera CEREC blocks).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe null hypothesis proposed that the trueness and precision of the fabricated endocrowns would remain unaffected by the milling machine or the type of glass ceramic material used. \u0026nbsp;\u003c/p\u003e"},{"header":"Materials And Methods","content":"\u003cp\u003eThe sample size was calculated by using R statistical analysis software version 4.4.2. \u0026nbsp;(Figure 1) Illustrates a schematic presentation of the study methodology. A typodont model of a maxillary right first molar (Nissin Dental Product) was used for the preparation of an endocrown restoration. The preparation followed the standard guidelines for endocrown design, incorporating a 1.5 mm circumferential \u0026nbsp; butt joint margin occlusally and a central retention area corresponding to the pulp chamber with a depth of 4 mm (22) was employed.\u003c/p\u003e\n\u003cp\u003eFor the fabrication of endocrown patterns, the typodont model was digitally scanned using an intraoral scanner (CEREC Omnicam; Dentsply Sirona) (Figure 2). The restoration was then designed with CEREC CAD software (CEREC Omnicam; Dentsply Sirona) and exported in standard tessellation language (STL) format to serve as both the reference design and the basis for fabricating the endocrown restorations. The design was used for the fabrication of endocrowns (N=40) from two materials. Group (E) utilized IPS Emax CAD (N=20), and group (T) used Tessera CEREC blocks (N=20); 10 of each group were milled using MCXL (EX), and the other 10 were milled using primemill (EP), and the same for Tessera (TX) and (TP).\u003c/p\u003e\n\u003cp\u003eThe STL file of the endocrown design was imported into the CAM software for processing by a 4-axis chairside milling unit (MCXL and Primemill) for subtractive manufacturing of endocrowns (Figure 3). All the fabricated specimens were checked on the corresponding preoperative cast for evaluation of sample seating; no modifications were made to the internal surfaces of the endocrowns.\u003c/p\u003e\n\u003cp\u003eAn intraoral scanner (CEREC Omnicam; Dentsply Sirona) was used to capture digital scans of all fabricated endocrowns, producing an STL file as test data for each endocrown pattern. The scans included both the external and intaglio surfaces, including the margins, axial, and occlusal areas. The intraoral scanner was calibrated before scanning each group.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe 3D trueness (intergroup comparison) was evaluated by importing the STL files of the test data and reference design into reverse engineering software (Geomagic Control X 2020; 3D Systems, Inc.). The root mean square (RMS) values were calculated using the \u0026quot;best fit alignment\u0026quot; and \u0026quot;3D analysis\u0026quot; tools. The deviations between the fabricated endocrowns and the reference design were analyzed across multiple points in 3D space (x-, y-, and z-axes). A color map was created to visualize these deviations, ranging from a maximum of 0.5 mm to a minimum of -0.5 mm, without applying any specific tolerance settings. The green color denoted a precise match between surfaces, red indicated that the test model surface was shifted positively relative to the reference model, and blue represented a negative shift of the test model surface in relation to the control model (figure 4).\u003c/p\u003e\n\u003cp\u003ePrecision (intragroup comparison) was calculated by RMS divisions within each group. Each scan was used as a reference, and the other nine scans within the same group were aligned to it, resulting in a total of 45 reports per group.\u003c/p\u003e\n\u003cp\u003eNumerical data are expressed as mean and standard deviation values and were assessed for normality using the Shapiro-Wilk test. Translucency The data were evaluated through a two-way analysis of variance (ANOVA). Simple effects were compared using the pooled error term from the main ANOVA model. P-values were modified for multiple comparisons using the False Discovery Rate (FDR) method, with a significance threshold of p\u0026lt;0.05 applied to all tests. Statistical analysis was performed with R statistical analysis software.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eFor the 3D trueness assessment, average RMS values were calculated to represent the 3D trueness (\u0026micro;m). The RMS values, indicating the deviations between the scans of the fabricated endocrowns and the reference design, are provided in (Table 1). No statistically significant difference in trueness was observed between Tessera samples and Emax samples fabricated using Primemill (p=0.488) or using MCXL (p=0.437). Furthermore, no statistically significant difference in trueness was found between Emax samples milled using MCXL (43.36\u0026plusmn;5.17) (\u0026micro;m) and those milled using Primemill (44.88\u0026plusmn;4.28) (\u0026micro;m) (p=0.593). Also, no statistically significant difference between Tessera samples milled using MCXL (41.14\u0026plusmn;2.01) (\u0026micro;m) and those milled using Primemill (42.90\u0026plusmn;5.34) (\u0026micro;m) (p=0.537) (Figure 5).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable (1) Mean RMS values of 3D trueness (\u0026micro;m) for different materials and milling machines.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 21px;\"\u003e\n \u003cp\u003eMilling machine\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 61px;\"\u003e\n \u003cp\u003eTrueness (RMS) (\u0026micro;m) (Mean\u0026plusmn;SD)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 17px;\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003eMCXL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003ePrimemill\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 21px;\"\u003e\n \u003cp\u003eEmax\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e43.36\u0026plusmn;5.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e44.88\u0026plusmn;4.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17px;\"\u003e\n \u003cp\u003e0.593ns\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 21px;\"\u003e\n \u003cp\u003eTessera\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e41.14\u0026plusmn;2.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e42.90\u0026plusmn;5.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17px;\"\u003e\n \u003cp\u003e0.537ns\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 21px;\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e0.437ns\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e0.488ns\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003ens (not significant)\u003c/p\u003e\n\u003cp\u003eRMS (root mean square)\u003c/p\u003e\n\u003cp\u003eSD (standard division)\u003c/p\u003e\n\u003cp\u003eTranslucency data were analyzed using two-way ANOVA.\u003c/p\u003e\n\u003cp\u003eStatistical analysis was performed with R statistical analysis software.\u003c/p\u003e\n\u003cp\u003eFor precision measurements, the average RMS values reflected the deviations between the scans of the fabricated endocrowns per each group, as shown in (Table 2). \u0026nbsp;No statistically significant difference within Emax samples (40.85\u0026plusmn;5.18) (\u0026micro;m) and Tessera samples (41.25\u0026plusmn;4.03) (\u0026micro;m) milled using MCXL (p=0.827). However, Tessera samples had significantly higher precision (23.46\u0026plusmn;2.03) (\u0026micro;m) than Emax (32.81\u0026plusmn;4.35) (\u0026micro;m) (p\u0026lt;0.001) when milled using Primemill. Additionally, Emax samples milled with Primemill had higher precision (32.81\u0026plusmn;4.35) (\u0026micro;m) than those milled with MCXL (40.85\u0026plusmn;5.18) (\u0026micro;m) (p\u0026lt;0.001). Also, Tessera samples milled with Primemill had higher precision (23.46\u0026plusmn;2.03) (\u0026micro;m) than those milled with MCXL (41.25\u0026plusmn;4.03) (\u0026micro;m) (p\u0026lt;0.001) (Figure 6).\u003c/p\u003e\n\u003cp\u003eTable (2) Mean RMS values of 3D precision (\u0026micro;m) for different materials and milling machines.\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 21px;\"\u003e\n \u003cp\u003eMilling machine\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 61px;\"\u003e\n \u003cp\u003ePrecision (RMS) (\u0026micro;m) (Mean\u0026plusmn;SD)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 17px;\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003eMCXL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003ePrimemill\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 21px;\"\u003e\n \u003cp\u003eEmax\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e40.85\u0026plusmn;5.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e32.81\u0026plusmn;4.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17px;\"\u003e\n \u003cp\u003e\u0026lt;0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 21px;\"\u003e\n \u003cp\u003eTessera\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e41.25\u0026plusmn;4.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e23.46\u0026plusmn;2.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17px;\"\u003e\n \u003cp\u003e\u0026lt;0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 21px;\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e0.827ns\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 30px;\"\u003e\n \u003cp\u003e\u0026lt;0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e* Significant\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;ns (not significant)\u003c/p\u003e\n\u003cp\u003eRMS (root mean square)\u003c/p\u003e\n\u003cp\u003eSD (standard division)\u003c/p\u003e\n\u003cp\u003eTranslucency data were analyzed using two-way ANOVA.\u003c/p\u003e\n\u003cp\u003eStatistical analysis was performed with R statistical analysis software.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe incorporation of digital technologies into restorative dentistry has made CAD/CAM systems indispensable for producing high-quality dental restorations. These systems provide various applications that improve clinical efficiency and accuracy (7, 8).The fabrication accuracy of endocrowns is significantly affected by the type of ceramic material used, such as IPS Emax CAD, which is widely preferred in clinical practice for its outstanding esthetic qualities and mechanical strength. Alternatively, Tessera CEREC blocks provide a new potential to the ceramic market (14, 23). Additionally, the choice of milling machine is essential in achieving high trueness and precision in the restoration and should be assessed and considered.\u003c/p\u003e\n\u003cp\u003eThis study analyzed the accuracy of chairside-manufactured endocrowns using two milling machines and two types of ceramic materials. The primary focus was to determine the impact of these variables on the restoration\u0026apos;s 3D dimensional accuracy, which directly influences clinical performance.\u003c/p\u003e\n\u003cp\u003eThe results of trueness evaluation revealed no statistically significant difference in the 3D trueness of restorations between samples milled using MCXL and Primemill (P \u0026gt; 0.05).\u003c/p\u003e\n\u003cp\u003eThe lack of significant differences in trueness between the milling machines and materials owes to advancements in modern chairside CAD/CAM systems. Regardless of the specific machine or material, CAD/CAM systems offer a high degree of accuracy in replicating digital designs for dental restorations. In addition, the software improvement of the milling machine and milling technology has minimized discrepancies and enhanced accuracy, provided that all other variables are standardized, such as the condition of the milling bur and cooling system, leading to uniformity in the trueness of restorations produced by different systems (24, 25). Moreover, material type may have a minimal impact on trueness under similar milling conditions, especially within the same category of ceramic material (26)\u003csup\u003e\u0026nbsp;\u003c/sup\u003e as type of material \u0026nbsp;is not the sole factor influencing the accuracy of CAD-CAM-milled crowns (27).\u003c/p\u003e\n\u003cp\u003eOn the contrary, a different study opposed our findings, stating that both the type of ceramic material and the milling machine had a significant impact on the trueness of the milled restorations. Their results may be attributed to the material\u0026apos;s properties, calibration of the intraoral scanner and milling machine, software design parameters, margin placement on the virtual model, and the operator\u0026apos;s experience, which are some of the factors that can influence the accuracy of fabricated restorations (28).\u003c/p\u003e\n\u003cp\u003eThe present data provided no significant difference in 3D trueness between samples milled using IPS E-max CAD and Tessera CEREC blocks (P\u0026gt;0.05). This data is in agreement with the findings of Canals et al., who stated that advanced lithium disilicate ceramics exhibit similar or slightly improved accuracy compared to traditional lithium disilicate ceramics, with no statistically significant difference (29). On the other side, a different study implicated that IPS Emax CAD crowns exhibited superior accuracy compared to Tessera CEREC crowns. This outcome may be linked to a longer period of grinding process, and the higher density of the material attributed to the difficulty in grinding, which affects the accuracy (30)\u003csup\u003e\u0026nbsp;\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eConsidering the results of the 3D evaluation of the precision of the milling machines, the findings indicate that the precision varied significantly between the two milling machines (P\u0026lt;0.001), as the Primemill outperformed the MCXL regardless of ceramic materials. The modern milling units equipped with advanced calibration systems achieve higher precision in dental restorations. Where the improvement in technological advancements, such as refined milling strategies and better control over the milling burs movement, helps in minimizing variability during the manufacturing process (31). \u0026nbsp;However, MCXL, an older model, may lack some of these refined capabilities, resulting in less consistent precision outcomes (25).\u003c/p\u003e\n\u003cp\u003eThe optimized milling algorithms and enhanced control of the milling bur\u0026rsquo;s movement reduced fabrication process discrepancies, resulting in a significantly higher 3D precision. Moreover, a report was done on the precision between different milling machine that showed that the accuracy of the restoration was influenced by the operator\u0026apos;s expertise and software optimization, regardless of the milling machine\u0026apos;s built-in capabilities. This misalignment between our results and the mentioned study could stem from variations in operator experience and the specific calibration and maintenance of the milling units, factors that were not controlled in this research (32).\u003c/p\u003e\n\u003cp\u003eThis study demonstrated a significant difference in precision based on the type of glass ceramic material used. While both materials performed well, Tessera showed better precision than IPS E-max CAD (P\u0026lt;0.001). Within the Primemill group, Tessera exhibited better precision than IPS Emax CAD (P\u0026lt;0.001). These findings indicate that the type of ceramic material may influence the consistency of milling outcomes, even when using a high-precision milling machine. The superior precision of Tessera could be attributed to its unique material properties. For instance, the microstructure and optimized milling parameters allow precise CAD/CAM-fabricated restorations (33, 34).\u003c/p\u003e\n\u003cp\u003eThe lack of significant differences between Tessera and IPS Emax CAD in the MCXL group in our study (P\u0026gt;0.05) pointed out that the limitations of the milling machine itself may overshadow the material-specific advantages\u003csup\u003e\u0026nbsp;\u003c/sup\u003e(35, 36).\u003c/p\u003e\n\u003cp\u003eThis was consistent with the findings of Alghazzawi et al. Whose research reported that older milling machines may lack the capability to exploit the full potential of advanced ceramic materials. Besides, their study \u0026nbsp;concluded that while material properties play a crucial role, the milling machine\u0026apos;s performance is often the primary factor in achieving high precision (35). Accordingly, even with superior material properties, the precision outcomes may not show significant differences if the machine\u0026apos;s inherent limitations are a determining factor (36).\u003c/p\u003e\n\u003cp\u003eA study done by Rezaie et al. contradicted our results and showed no significant differences in precision between ceramic materials when using advanced milling systems. Rezaie et al. data could be returned to the differences in the milling parameters, such as bur wear or cooling protocols, which could influence the material removal process and, subsequently, the precision of the restorations (37).\u003csup\u003e\u0026nbsp;\u003c/sup\u003eTheir data was also supported by Kirsch et al. (2017), who found that newer milling machines do not necessarily produce more precise restorations than older models (38). Moreover, a study by Roperto et al. \u0026nbsp;(2016) revealed no significant differences in marginal gaps between restorations milled with two different chairside milling machines, indicating that improvements in milling technology do not necessarily enhance restoration accuracy (39).\u003c/p\u003e\n\u003cp\u003eThe ongoing in-vitro study revealed no significant differences in trueness across various milling machines and materials. Additionally, within the Primemill group, Tessera exhibited better precision than IPS Emax CAD, while no notable difference was observed among the materials within the MCXL group.\u003c/p\u003e\n\u003cp\u003eThis study examined only two ceramic materials to fabricate endocrown restorations. The findings could differ when using other types of ceramic materials, which would require different milling protocols and milling machines. It is recommended to investigate and explore other parameters that could affect the accuracy of chairside-manufactured endocrowns.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eTaking into account the limitation of this in vitro study, the following conclusions can be inferred:\u003c/p\u003e\n\u003col\u003e\n \u003cli\u003eBoth milling machines can achieve a comparable level of accuracy in fabrication of restoration, supporting their clinical reliability for chairside fabrication.\u003c/li\u003e\n \u003cli\u003eEndocrown restoration fabricated using Primemill machine demonstrated superior precision compared to those fabricated using MCXL, regardless of the material used. This suggests that advancements in milling technology, such as improved calibration and enhanced milling algorithms in newer machines like Primemill, contribute to greater consistency in restoration fabrication.\u003c/li\u003e\n \u003cli\u003eWhile both older and newer milling machines can provide high trueness, newer systems like Primemill offer improved precision, which may reduce the risk of restorative failures and enhance clinical outcomes. The choice of material, such as Tessera with Primemill, can further optimize precision and consistency.\u003c/li\u003e\n \u003cli\u003eThe selection of ceramic material properties, in combination with the milling machine, can affect precision, highlighting the importance of selecting the appropriate machine-material combination for optimal results.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eCAD/CAM \u0026nbsp; \u0026nbsp; \u0026nbsp; Computer aided design and computer aided manufacturing\u003c/p\u003e\n\u003cp\u003eSTL \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Standard tessellation language\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eRMS \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Root mean square\u003c/p\u003e\n\u003cp\u003eFDR \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; False Discovery Rate\u003c/p\u003e\n\u003cp\u003eP \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;P-value\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026micro;m \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Micrometer\u003c/p\u003e\n\u003cp\u003eANOVA \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;analysis of variance\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data and resources utilized in this study can be obtained from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors confirm that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors state that no organization provided funding for this research.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor\u0026rsquo;s contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAMI conducted the methodology and authored the manuscript. DTS and ASE supervised the study and reviewed the manuscript. All authors reviewed and approved the final form of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor\u0026rsquo;s information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDepartment of Fixed Prosthodontics, Faculty of Dentistry, Badr University in Cairo, Cairo, Egypt.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAya Mohsen Ibrahim\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDepartment of Fixed Prosthodontics, Faculty of Dentistry, Ain Shams University, Organization of African Unity, Cairo, Egypt.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAmr Saleh El-Etreby\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDepartment of Fixed Prosthodontics, Faculty of Dentistry, New Giza University, Ain Shams University, Cairo, Egypt\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDoaa Taha Sayed Taha\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eJang Y, Sim J-Y, Park J-K, Kim W-C, Kim H-Y, Kim J-H. Evaluation of the marginal and internal fit of a single crown fabricated based on a three-dimensional printed model. The journal of advanced prosthodontics. 2018;10(5):367-73. https://pubmed.ncbi.nlm.nih.gov/30370028/\u003c/li\u003e\n\u003cli\u003eCarbajal Mej\u0026iacute;a JB, Yatani H, Wakabayashi K, Nakamura T. Marginal and internal fit of CAD/CAM crowns fabricated over reverse tapered preparations. Journal of Prosthodontics. 2019;28(2):e477-e84. https://pubmed.ncbi.nlm.nih.gov/29194841/\u003c/li\u003e\n\u003cli\u003eGiannetti L, Apponi R, Mordini L, Presti S, Breschi L, Mintrone F. The occlusal precision of milled versus printed provisional crowns. Journal of Dentistry. 2022;117:103924. https://pubmed.ncbi.nlm.nih.gov/34910962/\u003c/li\u003e\n\u003cli\u003eFelton D, Kanoy B, Bayne Sa, Wirthman G. Effect of in vivo crown margin discrepancies on periodontal health. The Journal of prosthetic dentistry. 1991;65(3):357-64. \u003cu\u003ehttps://pubmed.ncbi.nlm.nih.gov/2056454/\u003c/u\u003e\u003c/li\u003e\n\u003cli\u003eSj\u0026ouml;gren G. Marginal and internal fit of four different types of ceramic inlays after luting An in vitro study. Acta Odontologica Scandinavica. 1995;53(1):24-8. https://pubmed.ncbi.nlm.nih.gov/7740927/\u003c/li\u003e\n\u003cli\u003eBassiouny D, Petersmann S, Zohdy M, Morsi T, Taha D. Trueness and intaglio fit of custom-made polyetheretherketone post-and-cores fabricated using different techniques. The Journal of Prosthetic Dentistry. 2024. https://doi.org/10.1016/j.prosdent.2024.06.026\u003c/li\u003e\n\u003cli\u003eTaha D, Allam S, Morsi T. Accuracy of computer-aided design trial restorations fabricated with different digital workflows. The Journal of Prosthetic Dentistry. 2024;132(3):578-85. https://pubmed.ncbi.nlm.nih.gov/37925250/\u003c/li\u003e\n\u003cli\u003eOnlay LDP. Marginal and internal gap of handmade, milled and 3D printed additive manufactured patterns for pressed lithium disilicate onlay restorations. European Journal of Prosthodontics and Restorative Dentistry. 2018;26:31-8. https://pubmed.ncbi.nlm.nih.gov/29461746/\u003c/li\u003e\n\u003cli\u003eHamza TA, Sherif RM. In vitro evaluation of marginal discrepancy of monolithic zirconia restorations fabricated with different CAD-CAM systems. The Journal of prosthetic dentistry. 2017;117(6):762-6. https://pubmed.ncbi.nlm.nih.gov/27836145/\u003c/li\u003e\n\u003cli\u003eReddy AN, Ramesh D. Studies on Impact Strength of Concrete with Nano-Materials at Elevated Temperatures. Int J Sci Res \u0026amp;Devlp. 2015;3(9):40-4. https://www.researchgate.net/publication/339130560_Studies_on_Impact_Strength_of_Concrete_with_Nano-Materials_at_Elevated_Temperatures\u003c/li\u003e\n\u003cli\u003eDavidowitz G, Kotick PG. The use of CAD/CAM in dentistry. Dental Clinics of North America. 2011;55(3):559-ix. https://pubmed.ncbi.nlm.nih.gov/21726690/\u003c/li\u003e\n\u003cli\u003eMiyazaki T, Hotta Y, Kunii J, Kuriyama S, Tamaki Y. A review of dental CAD/CAM: current status and future perspectives from 20 years of experience. Dental materials journal. 2009;28(1):44-56. https://pubmed.ncbi.nlm.nih.gov/19280967/\u003c/li\u003e\n\u003cli\u003eRitzberger C, Apel E, H\u0026ouml;land W, Peschke A, Rheinberger VM. Properties and clinical application of three types of dental glass-ceramics and ceramics for CAD-CAM technologies. Materials. 2010;3(6):3700-13.\u003cu\u003e https://doi.org/10.3390/ma3063700\u003c/u\u003e\u003c/li\u003e\n\u003cli\u003eZarone F, Ferrari M, Mangano FG, Leone R, Sorrentino R. \u0026ldquo;Digitally oriented materials\u0026rdquo;: focus on lithium disilicate ceramics. International journal of dentistry. 2016;2016(1):9840594. https://pubmed.ncbi.nlm.nih.gov/27635140/\u003c/li\u003e\n\u003cli\u003eZULKIFFLI S, TAKE YO, YAHYA NA, KUTTY MG. Evaluation and Comparison of Mechanical Properties of Lithium Disilicate-Based. Sains Malaysiana. 2024;53(1):217-29. https://www.ukm.my/jsm/pdf_files/SM-PDF-53-1-2024/17.pdf\u003c/li\u003e\n\u003cli\u003eEnder A, Mehl A. In-vitro evaluation of the accuracy of conventional and digital methods of obtaining full-arch dental impressions. Quintessence international. 2015;46(1). https://pubmed.ncbi.nlm.nih.gov/25019118/\u003c/li\u003e\n\u003cli\u003eG\u0026uuml;th J-F, Edelhoff D, Schweiger J, Keul C. A new method for the evaluation of the accuracy of full-arch digital impressions in vitro. Clinical oral investigations. 2016;20:1487-94. https://doi.org/ 10.1007/s00784-015-1626-x\u003c/li\u003e\n\u003cli\u003ePark J-M. Comparative analysis on reproducibility among 5 intraoral scanners: sectional analysis according to restoration type and preparation outline form. The Journal of Advanced Prosthodontics. 2016;8(5):354-62. https://doi.org/ 10.4047/jap.2016.8.5.354\u003c/li\u003e\n\u003cli\u003eZimmermann M, Ender A, Mehl A. Local accuracy of actual intraoral scanning systems for single-tooth preparations in vitro. The Journal of the American Dental Association. 2020;151(2):127-35. https://doi.org/ 10.1016/j.adaj.2019.10.022\u003c/li\u003e\n\u003cli\u003eBosch G, Ender A, Mehl A. A 3-dimensional accuracy analysis of chairside CAD/CAM milling processes. The Journal of prosthetic dentistry. 2014;112(6):1425-31. \u003cu\u003e \u003c/u\u003ehttps://www.sciencedirect.com/science/article/abs/pii/S002239131400256X\u003c/li\u003e\n\u003cli\u003eAl Hamad KQ, Al‐Rashdan RB, Al‐Rashdan BA, Baba NZ. Effect of milling protocols on trueness and precision of ceramic crowns. Journal of Prosthodontics. 2021;30(2):171-6. https://doi.org/ 10.1111/jopr.13245\u003c/li\u003e\n\u003cli\u003eHayes A, Duvall N, Wajdowicz M, Roberts H. Effect of endocrown pulp chamber extension depth on molar fracture resistance. Operative dentistry. 2017;42(3):327-34. https://doi.org/ 10.2341/16-097-L\u003c/li\u003e\n\u003cli\u003eDartora NR, Moris ICM, Poole SF, Bacchi A, Sousa-Neto MD, Silva-Sousa YT, Gomes EA. Mechanical behavior of endocrowns fabricated with different CAD-CAM ceramic systems. The Journal of Prosthetic Dentistry. 2021;125(1):117-25. https://doi.org/ 10.1016/j.prosdent.2019.11.008\u003c/li\u003e\n\u003cli\u003eJivanescu A, Codruta I, Rotar R. Chairside CAD/CAM Restorations. 2024. https://doi.org/ 10.5772/intechopen.114090\u003c/li\u003e\n\u003cli\u003ePilecco RO, Machry RV, Baldi A, Tribst JPM, Sarkis-Onofre R, Valandro LF, et al. Influence of CAD-CAM milling strategies on the outcome of indirect restorations: A scoping review. The Journal of Prosthetic Dentistry. 2024. https://doi.org/ 10.1016/j.prosdent.2024.02.021\u003c/li\u003e\n\u003cli\u003eDemirel M, Donmez MB. Fabrication trueness and internal fit of different lithium disilicate ceramics according to post-milling firing and material type. Journal of dentistry. 2024;144:104987.\u003cu\u003e https://doi.org/10.1016/j.jdent.2024.104987\u003c/u\u003e\u003c/li\u003e\n\u003cli\u003eFayed AK, Azer AS, AboElhassan RG. Fit accuracy and fracture resistance evaluation of advanced lithium disilicate crowns (in-vitro study). BMC Oral Health. 2025;25(1):58. https://bmcoralhealth.biomedcentral.com/articles/10.1186/s12903-024-05325-z\u003c/li\u003e\n\u003cli\u003eKunkela J, Ingr T, Komarek A. Evaluation of marginal gap of teeth restored with crowns using six different CAD/CAM materials milled with two different milling units. International Journal of Computerized Dentistry. 2021;24(2):195-205. PMID: 34085504\u003c/li\u003e\n\u003cli\u003ePerez Canals M. Marginal Fit of CAD/CAM Crowns Milled From Two Different Ceramic Materials: Lithium Disilicate and Advanced Lithium Disilicate: University of Pittsburgh; 2023. http://d-scholarship.pitt.edu/id/eprint/44951\u003c/li\u003e\n\u003cli\u003eYamamoto K, Murata Y, Nagaoka K, Akiyama S, Hokii Y, Fusejima F. Comparison of dimensional accuracy of lithium disilicate CAD/CAM ceramics. Journal of Osseointegration. 2022;14(4):205-8. https://doi.org/10.23805/JO.2022.14.04.2\u003c/li\u003e\n\u003cli\u003eAl-Hassiny A. Fundamentals of Computer-Aided Design (CAD) in Dental Healthcare: From Basics to Beyond. 3D Printing in Oral Health Science: Applications and Future Directions: Springer; 2022. p. 93-119. https://www.researchgate.net/publication/363873876_Fundamentals_of_Computer-Aided_Design_CAD_in_Dental_Healthcare_From_Basics_to_Beyond\u003c/li\u003e\n\u003cli\u003eBeuer F, Aggstaller H, Edelhoff D, Gernet W, Sorensen J. Marginal and internal fits of fixed dental prostheses zirconia retainers. Dental Materials. 2009;25(1):94-102. https://www.sciencedirect.com/science/article/abs/pii/S0109564108001450\u003c/li\u003e\n\u003cli\u003eNassar HS, Abo El-Mal EO. In Vitro Evaluation of The Marginal Adaptation of Monolithic Ceramic Crowns Fabricated with Different Margin Designs Using Novel CAD/CAM Material After Thermomechanical Aging. Egyptian Dental Journal. 2024;70(1):575-85. https://journals.ekb.eg/article_334133.html\u003c/li\u003e\n\u003cli\u003eRekow E, Silva N, Coelho P, Zhang Y, Guess P, Thompson V. Performance of dental ceramics: challenges for improvements. Journal of dental research. 2011;90(8):937-52. https://journals.sagepub.com/doi/abs/10.1177/0022034510391795\u003c/li\u003e\n\u003cli\u003eAlghazzawi TF. Advancements in CAD/CAM technology: Options for practical implementation. Journal of prosthodontic research. 2016;60(2):72-84. https://www.sciencedirect.com/science/article/abs/pii/S1883195816000098\u003c/li\u003e\n\u003cli\u003eSchmidt J, Marques MR, Botti S, Marques MA. Recent advances and applications of machine learning in solid-state materials science. npj computational materials. 2019;5(1):83. https://www.nature.com/articles/s41524-019-0221-0\u003c/li\u003e\n\u003cli\u003eRezaie F, Farshbaf M, Dahri M, Masjedi M, Maleki R, Amini F, et al. 3D printing of dental prostheses: Current and emerging applications. Journal of composites science. 2023;7(2):80. https://www.mdpi.com/2504-477X/7/2/80\u003c/li\u003e\n\u003cli\u003eKirsch C, Ender A, Attin T, Mehl A. Trueness of four different milling procedures used in dental CAD/CAM systems. Clinical oral investigations. 2017;21:551-8. https://link.springer.com/article/10.1007/s00784-016-1916-y\u003c/li\u003e\n\u003cli\u003eRoperto R, Assaf H, Soares-Porto T, Lang L, Teich S. Are different generations of CAD/CAM milling machines capable to produce restorations with similar quality? Journal of clinical and experimental dentistry. 2016;8(4):e423. https://pmc.ncbi.nlm.nih.gov/articles/PMC5045690/\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Endocrown, Accuracy, CEREC Tessera, IPS emax cad, chairside milling machine, Primemill, MCXL milling machine, CAD/CAM","lastPublishedDoi":"10.21203/rs.3.rs-6378763/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6378763/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e: The accuracy of chairside-manufactured restorations plays a vital role in ensuring the long-term success of endocrown restorations. Factors, such as the type of ceramic material and the milling technique, need to be thoroughly examined to understand their impact on fabrication accuracy in dental offices.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMaterials and Methods\u003c/strong\u003e: \u0026nbsp;A typodont model of a maxillary right first molar was prepared for an endocrown restoration, digitally scanned, and designed using CEREC CAD software. A total of 40 endocrowns were fabricated based on the reference design from two materials. Group (E) utilized IPS Emax CAD (N=20), and group (T) used Tessera CEREC blocks (N=20); 10 of each group were milled using MCXL (EX), and the other 10 were milled using primemill (EP), and the same for Tessera (TX) and (TP). All fabricated endocrowns were scanned, and test data were collected in standard tessellation language (STL) format. These datasets, along with the reference design, were compared using reverse engineering software to evaluate the 3D trueness and precision of the fabricated restorations. Data were analyzed using two-way ANOVA. The significance level was set at p\u0026lt;0.05 within all tests. Statistical analysis was performed with R statistical analysis software version 4.4.1 for Windows.\u003csup\u003e[1]\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e: Root mean square (RMS) values were used to evaluate the 3D trueness and precision between tests. No significant differences in trueness were found between Tessera and Emax samples milled with Primemill (p=0.488) or MCXL (p=0.437). Similarly, no notable differences were observed between Emax (p=0.593) or Tessera (p=0.537) samples milled by either machine.\u003c/p\u003e\n\u003cp\u003eFor precision, Emax and Tessera samples milled with MCXL showed no significant difference (p=0.827). However, Tessera samples milled with Primemill had higher precision (23.46±2.03 µm) than Emax (32.81±4.35 µm) (p\u0026lt;0.001). Primemill also produced more precise Emax (p\u0026lt;0.001) and Tessera (p\u0026lt;0.001) samples compared to MCXL.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e: The two milling systems offer comparable accuracy for restoration fabrication, ensuring clinical reliability for chairside use. However, the Primemill machine showed superior precision in fabricating Endocrown restorations compared to the MCXL, suggesting that advancements in milling technology, like improved calibration and milling algorithms, enhance consistency and precision.\u003c/p\u003e\n\u003cp\u003e[1] R Core Team (2024). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. 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