A computer-implemented method of creating an auxiliary 3D virtual model corresponding to an obscured portion of a finish line in a 3D virtual model of at least a portion of an intraoral cavity comprising a preparation having said finish line, the computer-implemented method comprising: providing the 3D virtual model of the at least a portion of the intraoral cavity comprising the preparation having the finish line, wherein at least a portion of the finish line is obscured by obscuring matter; identifying in said 3D virtual model a first virtual model part representing a dental site comprising said preparation and a second virtual model part representing at least soft tissues in abutting virtual contact with said first virtual model part; manipulating said 3D virtual model such as to separate said first virtual model part from said second virtual model part; manipulating said 3D virtual model in an area comprising said obscured portion of said finish line in a virtual manner such as to create an auxiliary 3D virtual model corresponding to said obscured portion of said finish line, wherein the manipulating comprises manipulating said first virtual model part such as to create said auxiliary virtual model; and providing topographical data of the finish line from the 3D virtual model and the said 3D auxiliary virtual model, wherein manipulating said first virtual model part such as to create said auxiliary virtual model corresponding to said obscured part of said finish line comprises: providing at least one cross section (C N) of said 3D virtual model along a working plane (X N) inclined to an occlusion plane, at least within said obscured finish line portion, said cross-section comprising a first cross-section profile representing said preparation and a second cross-section profile representing said obscuring matter in abutting virtual contact with said first cross-section profile at a contact region; extrapolating said first cross-section profile from said contact region to provide a third cross-section profile representing an approximation of a corresponding cross-section of said dental site obscured by said obscuring matter and identifying therein a corresponding element of said obscured finish line portion (S2 N). providing the 3D virtual model of the at least a portion of the intraoral cavity comprising the preparation having the finish line, wherein at least a portion of the finish line is obscured by obscuring matter; identifying in said 3D virtual model a first virtual model part representing a dental site comprising said preparation and a second virtual model part representing at least soft tissues in abutting virtual contact with said first virtual model part; manipulating said 3D virtual model such as to separate said first virtual model part from said second virtual model part; manipulating said 3D virtual model in an area comprising said obscured portion of said finish line in a virtual manner such as to create an auxiliary 3D virtual model corresponding to said obscured portion of said finish line, wherein the manipulating comprises manipulating said first virtual model part such as to create said auxiliary virtual model; and providing topographical data of the finish line from the 3D virtual model and the said 3D auxiliary virtual model, providing at least one cross section (C N) of said 3D virtual model along a working plane (X N) inclined to an occlusion plane, at least within said obscured finish line portion, said cross-section comprising a first cross-section profile representing said preparation and a second cross-section profile representing said obscuring matter in abutting virtual contact with said first cross-section profile at a contact region; extrapolating said first cross-section profile from said contact region to provide a third cross-section profile representing an approximation of a corresponding cross-section of said dental site obscured by said obscuring matter and identifying therein a corresponding element of said obscured finish line portion (S2 N).