Comparative Evaluation of the Marginal Adaptation of Cast Ni-Cr Copings, Direct Metal Laser Sintering Co-Cr Copings, and Computer-aided Design and Computer-aided Manufacturing Zr Copings: An In-vitro Study.

Background and purpose Marginal adaptation is critical for the long-term longevity and clinical success of dental restorations. Improper marginal adaptation may lead to oral fluids, resulting in microleakage and cement dissolution. The present in vitro study aimed to evaluate the marginal adaptation of nickel-chrome (Ni-Cr) copings, cobalt-chrome (Co-Cr) coping, and zirconium (Zr) copings, produced with different manufacturing procedures. Material and methods A total of 45 copings were fabricated on a standardized metal die by using a two-stage putty impression and poured with die stone. They were divided into three groups of 15 each: A, B, and C. For group A, Ni-Cr copings were fabricated by conventional casting procedures; for group B, Co-Cr copings by direct metal laser sintering (DMLS); and for group C, zirconium copings by computer-aided design and computer-aided manufacturing (CAD/CAM) systems. Four areas around the tooth surface, namely, the mid-mesial, buccal, distal, and lingual surfaces, were digitally analyzed for marginal adaptation under the scanning electron microscope. Results The mean marginal gap for group A on the mid mesial, buccal, distal, and lingual surfaces was 79.67, 83.27, 90.67, and 89.13 µm, respectively. The mean marginal gap for group B on the mid-mesial, buccal, distal, and lingual surfaces was 38.13, 46.20, 45.73, and 42.20 µm, respectively. The mean marginal gap for group C on the mid mesial, buccal, distal, and lingual surfaces was 36.73, 31.73, 29.00, and 30.53 µm, respectively. Conclusion The marginal adaptation of CAD/CAM Zr copings is more accurate when compared to the DMLS Co-Cr and Cast Ni-Cr copings on a standard master die.