purpose: The purpose of this study was to evaluate the effect of pattern construction technique on the marginal accuracy, internal fitness and fracture resistance of E-max crowns. materials and methods: Thirty caries-free human maxillary first premolars were selected, cleaned by scaling, and stored in 0.9% standardized saline solution at room temperature. Using an industrial lathe machine, the teeth were prepared to receive all ceramic crowns with standardized dimensions of 6 degrees angle of convergence. The preparation had 5mm occluso-cervical height, 6mm cervical diameter and 1 mm deep chamfer finish line. The prepared teeth were divided into three groups (n=10) according to the pattern fabrication techniques used: Group1: Conventional wax patterns. Group2: CAD/CAM wax patterns. Group3: 3D Printing of resin patterns. All patterns were invested to construct E-max crowns. The ceramic crowns were seated on their corresponding prepared teeth and the vertical marginal gap was measured with a binocular microscope (90X). Then internal gap of each ceramic crown was measured using the silicone replica technique. After cementation, each ceramic crown was statically, compressively and axially loaded until fracture at a cross head speed of 1 mm/min using a steel rod placed centrally at the occlusal surface of the crowns to evaluate the fracture resistance of the crowns. results: Group 1 showed the largest marginal gap mean (85.74±2.58μm) followed by group 2; (74.06±3.27µm) and then group3 (69.35± 3.44µm). These differences were statistically significant among the groups. The results of internal gap distances in group 1 (112±7.66µm) followed by group 2 (100±5.76µm) and then group3 (82± 7.2µm), the differences between the groups were statistically significant. The mean fracture resistance values of groups 1, 2 and 3 were 850.67±25.30N, 1080.01±47.06N and 1412.18±28.92N respectively. Post hoc test revealed that the differences between groups 1 and 2 as well as between groups 2 and 3 were statistically insignificant; however, the difference between groups 1 and 3 was statistically significant. Spearman's rank correlation coefficient showed value of-0.781. The negative sign indicates that the fracture resistance of the samples decreased as the internal gaps increased conclusions: The 3D printed pattern resulted in an E-max crown with better marginal adaptation and internal fitness. The fracture resistance of E-max crown was improved as its internal adaptation was enhanced.
Purpose:The current study aimed to evaluate the marginal accuracy and microleakage of machinable laminate veneers. Materials and Methods: Twentyfour human maxillary central incisor teeth were collected and prepared (butt-joint preparation) to receive laminate veneers. They were divided into three groups (n=8) according to material of construction: Group I: IPS-Emax CAD, Group II: Vita Suprinity, Group III: Celtra-Duo. The veneers were milled from the blocks in a CEREC 3 Machine. All veneers were cemented with resin cement. All samples had been subjected to 1500 thermal cycles which are equivalent to one year and half of clinical use. Marginal gap (pre and post cementation) and microleakage were detected for all samples. Data were tabulated and statistically analyzed. Results: Regarding vertical marginal gap, E max CAD showed the highest mean value followed by Celtra Duo, while the lowest mean value was found in Vita Suprinity. The mean values before cementation were higher than after cementation. Regarding microleakage, the highest mean value was found in E max followed by Celtra Duo, while the lowest mean value was found in Vita Suprinity. Leakage at cervical margins showed higher mean values than incisal one. Conclusion: Under the test conditions, the following was concluded: Zirconia reinforced Lithium silicate restorations, particularly the partially crystalline form, introduced better marginal accuracy and microleakage than Lithium disilicate restorations. There is a direct correlation between marginal accuracy and microleakage.
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