الفهرس | Only 14 pages are availabe for public view |
Abstract Aim: The current study aimed to investigate and evaluate the impact of two different milling protocols on the marginal accuracy and fracture resistance of crowns fabricated from glass-ceramic (CEREC Tessera) material. Methodology: A maxillary first molar of a typodont model was prepared according to the conventional full-contour all-ceramic crown preparation with a heavy chamfer finish line following the manufacturer’s recommendation. The crowns (n = 18) were divided into two groups (n = 9) based on their production with milling machines. group A: (Sirona CEREC MC XL 4-axis milling machine); group B: (CEREC InLab MCX5 5-axis milling machine). The marginal accuracy was assessed using a stereomicroscope at 30×magnification. The 18 crowns were bonded to their corresponding epoxy resin dies which were duplicated from the prepared typodont tooth using rubber base duplicating material to obtain 18 epoxy resin dies. The fracture resistance of both groups was evaluated using a universal testing machine. One Way ANOVA test was used to compare the marginal accuracy of different surfaces in both groups, the independent t-test was used to compare fracture resistance results between both groups. Statistical analysis of the results and comparison between the two groups were performed using an independent t-test (significance: P ≤ 0.05). Results: Regarding the marginal accuracy results, there was a significant difference between both groups overall, as group A (140.46 μm ± 16.07) was significantly higher than group B (109.68 μm ± 16.91). The fracture resistance values for the CEREC Tessera crowns in both groups were (1458.92 N ± 207.92) for the 4-axis milling group and (1783.22 N ±428.05) for the 5-axis milling group, which revealed insignificant differences between the 4-axis and the 5-axis groups, with P = 0.06. Conclusions: Within the limitations of this in vitro study, both milling protocols showed fracture resistance and marginal accuracy within the clinically acceptable range. The number of CAD/CAM axes showed an influence the marginal accuracy of CEREC Tessera glass-ceramic crowns. The number of milling axes in both different milling protocols didn’t significantly impact the fracture resistance of CEREC Tessera glass-ceramic material. The CEREC Tessera is a promising material as far as aesthetics in concerned and is capable of maintaining high intrinsic strength. Keywords: Marginal accuracy, Fracture resistance, CAD/CAM system, Glass ceramics, CEREC Tessera. |