A “digital impression” is provided in lieu of a physical “dental” impression. A 3D digitizer is used to capture the digital impression, e.g., by scanning in a patient's oral cavity. A digital impression “data set” is formed using a computer-implemented method. The method begins by generating a three dimensional (3D) restoration model. Then, a bounding volume of the restoration model is computed. The bounding volume is defined as at least a minimum 3D volume that contains the 3D model. Thereafter, a lower solid 3D model, and an upper solid 3D model are created; these lower and upper models have a predetermined relationship with one another. In particular, when superimposed upon one another within the bounding volume, the lower and upper 3D models define a cavity into which the restoration model is adapted to fit. The restoration model, the lower solid 3D model and the upper solid 3D model are then aggregated into the data set to form the digital impression. Typically, the digital impression is generated at a first location, i.e., a dental office, and then transmitted to a second location, a dental laboratory, remote from the first location. Such transmission is conveniently done over a network, such as a TCP / IP network (e.g., the Internet). A dental item is then manufactured at the second location. Thus, for example, the lower solid 3D model may be used to build a coping, or the restoration model itself used to build a restoration. In the latter case, information in the data set may be used to check a fit of the restoration.