title: Photogrammetric method to measure the discrepancy between clinical and software-designed positions of implants.
abstract: BACKGROUND
  The position of dental implants placed with software-guided systems should be highly accurate in order to ensure safety and a passive fit of the immediate prosthesis.
  
  
  OBJECTIVE
  The purpose of this study was to measure the discrepancy between the clinical and software-planned position of dental implants by applying a photogrammetric method.
  
  
  METHODS
  Two casts were obtained, 1 from the surgical template and 1 from the actual position of the implants on the alveolar ridge of a patient. Photogrammetry was then applied to precisely locate the position of each implant on the casts. Because this mathematical technique required the identification of image points and of the relative spatial coordinates, 4 marks were drilled on the implant screw. The position of the implants was then identified as the geometric center of the 4 marks, while the orientation of the implant axis was represented by a vector normal to the plane fitting the points. A series of 16 convergent images all around the object was made using a high-resolution digital camera. A mathematical method called "rototranslation" was used to superimpose the cast images for the comparison.
  
  
  RESULTS
  The tests performed on the casts resulted in an average precision level of 4 μm for the locations and less than 1 degree for the axis of the implants. A series of empirical and numerical tests were performed to assess the performance of the procedure and of the measurement protocol.
  
  
  CONCLUSIONS
  The photogrammetric method is reproducible and can be used to measure the discrepancy between the software-planned and the real position of dental implants. Considering that the average precision level required for an implant-based prosthesis is approximately 50 μm, the error associated with this method can be considered as negligible.
authors.affiliation: Doctoral student, Section of Periodontology, Implantology, and Gnathology, Centre of Dentistry, University of Parma, Parma, Italy. Electronic address: federivara@gmail.com.
authors.forename: Federico
authors.initials: F
authors.lastname: Rivara
authors.affiliation: Assistant Professor, Section of Periodontology, Implantology, and Gnathology, Centre of Dentistry, University of Parma, Parma, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Lumetti
authors.affiliation: Doctoral student, Periodontology Unit and Department of Clinical Research, UCL Eastman Dental Institute, London, UK.
authors.forename: Elena
authors.initials: E
authors.lastname: Calciolari
authors.affiliation: Doctoral student, Section of Periodontology, Implantology, and Gnathology, Centre of Dentistry, University of Parma, Parma, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Toffoli
authors.affiliation: Professor, Department of Civil Engineering, University of Parma, Parma, Italy.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Forlani
authors.affiliation: Assistant Professor, Section of Periodontology, Implantology, and Gnathology, Centre of Dentistry, University of Parma, Parma, Italy.
authors.forename: Edoardo
authors.initials: E
authors.lastname: Manfredi
mesh_terms: D017076:Computer-Aided Design; D003735:Dental Casting Technique; D059605:Dental Implant-Abutment Design / Q000379:methods; D003758:Dental Implantation, Endosseous / Q000379:methods*; D015921:Dental Implants; D003761:Dental Impression Technique; D017267:Dental Prosthesis Design / Q000379:methods; D006801:Humans; D010780:Photogrammetry / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000379:methods*
chemical_list: D015921:Dental Implants