Effect of Heating CAD/CAM-Fabricated Ceramic Crowns on Marginal Fit Accuracy

Abstract

Purpose: This study aimed to measure the marginal discrepancy at the buccal, mesial, and distal sides along the marginal edge of all-ceramic crowns fabricated using the DENTAL Cadim CAD/CAM system and to examine the effect of a post-milling heat treatment for staining on the marginal fit of the all-ceramic crowns.
Methods: An 18-8 stainless steel abutment tooth with a height of 5 mm and an occlusal convergence angle of 8° was used as a mold. A cylindrical pattern model was fabricated using a brush stacking method with an autopolymerizing resin. Three-dimensional geometric measurement of the pattern model was performed using a spherical ruby scanning probe. Subsequently, five all-ceramic crowns were milled from Cadim block CE by using the DENTAL Cadim CAD/CAM system. Surface roughness (R_a and R_max) of the occlusal surface and vertical distances between the marginal edge and the mold before and after the post-milling heat treatment were measured using a profilometer and an X-Y coordinate reading microscope, respectively.
Results: The Ra and Rmax significantly decreased after the heat treatment. The vertical distance at the mesial and distal sides of the crowns was approximately 10 μm before and after the heat treatment. This distance at the buccal side was significantly greater (17.1 μm) than that at the mesial and distal sides before heating, and it significantly increased to 22.0 μm after heating.
Conclusion: The all-ceramic crowns milled from Cadim block CE by using the DENTAL Cadim CAD/CAM system showed a clinically acceptable marginal fit. We also observed that the fitting accuracy differed significantly among the three sides of the crown. The change in the marginal fit after the post-milling heat treatment was of a clinically acceptable value.