(In-Vitro Comparison between Closed Versus Open CAD/CAM Systems) Comparison between Closed and Open CAD/CAM Systems by Evaluating the Marginal Fit of Zirconia-Reinforced Lithium Silicate Ceramic Crowns

Abstract

Background: This study compared the marginal gap (MG) and absolute marginal discrepancy (AMD) of computer-aided design and computer-aided manufacturing (CAD–CAM) used in open systems (OSs) and closed systems (CSs) for producing monolithic zirconia-reinforced lithium silicate (ZLS) ceramic crowns. Methods: 60 ZLS ceramic crowns were cemented to abutment acrylic teeth; thirty crowns were designed and milled by an OS, and thirty by a CS. All crowns were sectioned for evaluating the marginal gap by scanning electronic microscopy (SEM). To compare the marginal gap between CS and OS techniques, data were analyzed using the independent-samples Mann–Whitney U Test (α = 0.05). Results: AMD was found to be significantly better for the closed system (p < 0.05). Mean AMD values for the CS were 148 µm, and for the OS it was 196 µm. MG was found to be significantly better for the OS (p < 0.05). Mean MG values for the CS were 55 µm, and for the OS they were 38 µm. Conclusions: The marginal gap in relation to AMD was significantly better for CS. However, the marginal gap in relation to MG was significantly better for OS. Both techniques showed clinically acceptable MG values (<120 µm).

Evaluation of Marginal/Internal Fit and Fracture Load of Monolithic Zirconia and Zirconia Lithium Silicate (ZLS) CAD/CAM Crown Systems

“…As for the ZLS crowns, the mean AMD values (128.1 ± 49.1µm) found in this study closely matched the results (148 ± 11 µm and 132.1 ± 39.4 µm) obtained in recent papers [ 31 , 67 ]. However, the current AMD values were also markedly lower than the discrepancies (235.5 ± 35.7 µm) reported in another paper [ 28 ].…”

“…The mean AMD values were noticeably higher than the marginal gap values in this study for both crown systems. The differences were consistent with the findings of several other studies that also investigated these two aspects of marginal fit [ 28 , 31 , 60 , 67 ]. The variability in the AMD values between Zi and ZLS could be related to the inherent differences in the milling process—dry milling for Zi versus wet milling for ZLS, and the use of specific types of grinding burs for each material type.…”

“…The reasons for the differences could possibly be attributed to the type of abutment used for evaluation (natural tooth abutment replica in the present study versus implant abutment in the other study), crown fabrication technique employed, and software used. The mean marginal gaps in the present study (39.5 ± 7.4 µm) showed similarities with the numbers reported in a recent study, of 38.4 ± 4 µm [ 67 ], but they were also in disagreement with some others, e.g., 77.9 ± 36.7 µm [ 68 ] and 85 ± 40 µm [ 30 ]. The disparities in the mean marginal gap between the present and earlier papers and the relative small marginal gaps seen in this report might be ascribed to the CAD/ CAM system/5-axis milling machine used, milling bur condition, crystallization parameters set, laboratory technician skill and experience, fit evaluation method used, abutment preparation design/margin configuration, and the effect of no cementation.…”

Marginal accuracy of Cad/Cam occlusal veneers fabricated from glass and hybrid ceramics with two preparation designs: An in vitro study

“…Cerec software closed system was used for designing and milling the occlusal veneers to avoid any discrepancies that may show up by open system. According to (Ben-Izhack et al, 2021) there were significant differences in favour of zirconia-reinforced lithium silicate crowns produced by closed systems compared to open systems when the absolute marginal discrepancy parameter was evaluated [14] . Lithium disilicate glass ceramic material (Rosetta SM blocks) and hybrid ceramic material (VITA ENAMIC® Blocks) were the materials chosen to conduct this study.…”

Fabrication of non-replaceable superstructures on conventional and digital impression intraosseous implants

“…There are different systems with open, semiopen, or closed architecture depending on the type of file that is created during scanning. The first two provide a greater degree of freedom to the clinician and connection to different dental laboratories when exporting the data, as they are saved in an STL format (29,30,31).…”