MARGINAL ACCURACY AND INTERNAL FIT OF MACHINE-MILLED AND CAST TITANIUM CROWNS

Statement of problem. Titanium is an alternative tooth restorative material because of a its biocompatibility and mechanical properties. However; there is little information on the marginal accuracy of a complete titanium crown with different margin configurations. Purpose. This study examined the effect of fabrication method and margin configuration on the marginal and internal fit of complete titanium crowns. Material and methods. An acrylic resin maxillary first molar was prepared with shoulder (buccal), chamfer (palatal), and knife edge (proximal) margin configurations. Forty crowns were produced and then divided into 2 groups according to the manufacturing method (casting method or CAD/CAM technique) (n=20). Each crown was luted to the original stone die with zinc phosphate cement. The margin of the crown, center point of the axial wall, and occlusal area were measured with a 3-dimensional measuring microscope. An independent t-test (internal gap) and repeated measures 2-way ANOVA (marginal gap) were used for statistical analysis (alpha=.05). Results. The mean marginal gap of the cast group was significantly smaller than that of the CAD/CAM group (P<.001). The margin configuration affected the measured marginal discrepancy (P<.001). In both groups, the mean marginal gap of the chamfer and shoulder margin was significantly smaller than that of the knife-edge margin (P<.001). Conclusions. Castings-produced titanium crowns with a better marginal fit than the CAD/CAM technique. The knife-edge margin exhibited the greatest marginal discrepancy. (J Prosthet Dent 2011;106:191-197)