A computer-based prosthodontic method is provided, for enabling a dental practitioner to define a finish line (74) of a dental prosthesis of at least one tooth to be fitted over a tooth preparation. The method comprises the following steps: providing a three-dimensional (3D) digital data (310) relating to the patient’s dentition, the 3D data includes data representative of the surface topology of the preparation and its surroundings; generating first finish line data (302) representative of at least a portion of the finish line and superimposing an image of the finish line on an image of the dentition; obtaining second finish line data determined on the basis of input (330) received from a dental practitioner; and using the second finish line data to update the first finish line data (340) and superimposing the updated data on the dentition image.