Marginal accuracy and internal fit of machine-milled and cast titanium crowns

Abstract

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 (α=.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.