Marginal adaptation of zirconia CAD-CAM copings with two cervical finish lines

Marginal adaptation is important for the long-term success of restorations. The finish line design can influence the marginal integrity. This study aimed to evaluate the effect of radial shoulder and deep chamfer finish line designs on the marginal adaptation of zirconia copings fabricated by the CAD-CAM system. 

In this experimental study, a standard chrome-cobalt die (height: 7mm, diameter: 5mm) was designed by software. The data were sent to a 3D printer device, and the resin pattern of the standard die was fabricated. After casting the resin pattern, a standard chrome-cobalt die was obtained with a 1-mm radial shoulder finish line and a 0.8-mm deep chamfer finish line. The walls were 12° converge (6° each) towards the occlusal surface. The standard die was replicated 9 times with a polyvinyl siloxane elastomeric material and poured with type IV dental stone. Zirconia copings were fabricated, and the vertical gap at 8 points was measured by a stereo microscope. Data were analyzed by the t-test, and statistical significance was set at α=0.05.

The vertical gap values were 102.91 µm for deep chamfer and 82.42 µm for radial shoulder finish lines. There was no significant difference between the two preparation designs in terms of the mean vertical gap (P=0.098).

The results of this study showed clinically acceptable marginal adaptation values for both deep chamfer and radial shoulder preparation designs without a statistically significant difference.