Abstract: The surface of a dental part is scanned by a probe, to obtain a digital model of the surface in a dental CAD computer system. In the digital model, first and second boundary lines are defined, above and below a portion in which the scanned data is missing or unsatisfactory. One of the boundary lines may correspond to a margin line between prepared and unprepared portions of the patient's tooth. A transition surface is generated in the computer system, extending between the first and second boundary lines. This improves the representation of the dental part in the digital model, which may subsequently be used for manufacture of a dental restoration.