Materials and Methods: Adentoform tooth of a right mandibular first molar was prepared to receive all ceramic crown restoration with deep chamfer finishing line (1mm) and axial reduction convergence angle of 6 degree, dentoform model duplicated to have Nickel-Chromiµm master die. The objective of present in vitro study was to evaluate the effect of four different CAD/CAM systems on the marginal fit of lithiµm disilicate all ceramic crowns.
(J Prosthet Dent 2014 -:-)īackground: The marginal fit is the most characteristic that closely related to the longevity or success of a restoration, which is absolutely affected by the fabrication technique. Lithium disilicate crowns fabricated by using the Cerec 3D Bluecam scanner CAD/CAM system or the heat-pressing technique exhibited a significantly smaller vertical misfit than crowns fabricated by using an E4D Laser scanner CAD/CAM system. Both types of horizontal misfit (underextended and overextended) were 49.2% for heat-pressing, 50.8% for Cerec, and 58.8% for E4D. The percentage of crowns with a vertical misfit <75 mm was 83.8% for Cerec and heat-pressing, whereas this value was 65% for E4D. The mean values of vertical misfit were 36.8 !3.9 mm for the heat-pressing group and 39.2 (.7 mm for the Cerec group, which were significantly smaller values than for the E4D group at 66.9 #1.9 mm (P¼.046). Data were statistically analyzed by 1-way ANOVA, followed by the Tukey honestly significant difference test (a¼.05). Each crown was fixed to the cast and scanned with micro-computed tomography to obtain 52 images for measuring the vertical and horizontal fit. Three fabrication techniques were used: digital impressions with Cerec 3D Bluecam scanner with titanium dioxide powder, followed by milling from IPS e.max CAD for Cerec digital impressions with E4D Laser scanner without powder, followed by milling from IPS e.max CAD for E4D and fabrication from IPS e.max Press by using the lost-wax and heat-pressing techniques. Lithium disilicate crowns were fabricated to fit an in vitro cast of a single human premolar. The purpose of the study was to evaluate with micro-computed tomography the marginal fit of lithium disilicate crowns fabricated with different chairside CAD/CAM systems (Cerec or E4D) or the heat-pressing technique. No consensus exists concerning the acceptable ranges of marginal fit for lithium disilicate crowns fabricated with either heat-pressing techniques or computer-aided design and computer-aided manufacturing (CAD/CAM) systems.
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