Abstract: Into the mandibular or maxillary bone of a patient a plurality of osteo-integrated implants (10) are inserted. Each implant (10) has a bearing surface (12) for a mating surface (13) of a framework (F), and a threaded hole (15) perpendicular to the bearing surface (12) and capable of receiving a screw (14) for connecting the framework to the implant (10). To each implant is coupled a gauge (20) with a stem (21) screwed into the threaded hole (15) of the implant and a spherical head (22) protruding visibly beyond the edge of the patient's gum. Images of the oral cavity are obtained from different viewpoints, and from those images data regarding the position of the centres (Z) of the spherical heads and data regarding the orientation of the stems (21) are obtained.