Photogrammetry technique for the 3D digital impression of multiple dental implants

In the computer-aided design and manufacturing (CAD/CAM) dentistry, intra-oral scanners (IOS) are usually used to capture the teeth/implants position and adjacent soft tissues for fabrication of prostheses. However, scanning errors are associated with IOS for full arch impressions and teeth/implants with divergent alignments. While small degree of errors may be absorbed by the periodontal ligament of abutment teeth and the cement layer under the cement-retained prostheses, passive seating is particularly difficult to achieve for implant supported screw-retained prostheses in which implants are ankylosed and little leeway allowed for screw system. In this clinical report, five patients requested prosthodontic treatment for her compromised functional and aesthetic situation. Photogrammetry system and a conventional irreversible hydrocolloid impression were used to capture the three-dimensional implant position and the associated soft tissue topography, respectively. The two digital files were subsequently superimposed using a best-fit alignment function to generate the definitive digital model with information on teeth, soft tissues, and implants. An immediately digital set up was designed and a poly (methyl methacrylate) wax try-in was milled to check the esthetics parameters, the occlusal relations and to evaluate its passive fit. After this, the framework was manufactured using a milled-sintered cobalt-chromium and then coated with ceramic. A CAD/CAM implant supported screw-retained prosthesis with a good fit and esthetic was manufactured. The described technique suggests certain advantages over conventional techniques, however further studies and long-term clinical data are needed to evaluate the accuracy of photogrammetry in comparison with the other available techniques.