The permanence of prosthetic treatment with the use of fixed prosthetic restorations depends, inter alia, on two important variables: the accuracy of manufacture of the prosthetic substructure and the marginal adaptation of the restoration. Co-Cr alloys are the basic material for making fixed complex prosthetic restorations. Modern laboratories, working on the basis of the CAD / CAM system, offer the construction of the framework for prosthetic crowns, including the Direct Metal Laser Sintering (DMLS) technology. Another possibility of producing fixed restorations is subtractive machining, i.e. metal milling. Regardless of the chosen method of producing a prosthetic work, the precision of execution is the factor determining longterm clinical success. With the development of new techniques and the CAD/CAM software used, it is possible to automate individual stages, and thus eliminate some errors of the human factor. The analysed literature describes several protocols on the basis of which marginal adaptation of prosthetic restorations on a Cr-Co alloy substructure is tested. However, the most frequently used technique was the replica method due to its speed, usefulness, and in many cases there is no need to destroy the tested samples. The marginal tightness of 120 µm is considered a clinically acceptable value. In the overwhelming majority of the described studies, the tests performed using both manufacturing techniques (DMLS and CNCM) achieved an acceptable and even much better (<or equal to 70 µm) marginal fit and demonstrated the superiority of new manufacturing techniques over conventional ones.