The aim of this clinical report is to describe the use of the photogrammetric system and intraoral scanning as a reliable technique to record the 3-dimensional implant positions of a full-arch maxillary implant–supported fixed rehabilitation in which the implants were unfavorably positioned. The stereo camera of the photogrammetric system was used to capture the 3-dimensional panoramic position of the implants. The information on soft tissues was obtained with an intraoral scanner. Then, the 2 digital files (standard tessellation language [STL] files) were subsequently superimposed using a best-fit alignment function to generate the definitive digital model with information on teeth, soft tissues, and implants.
Introduction
Correct positioning of dental implants is an important factor to ensure their predictability.1,2 It facilitates the impression process (which can promote a passive fit) and contributes to minimizing the risks of structure fracture, screw loosening, and esthetic and functional complications.3,4
The passive fitting of screw-retained implant-supported prostheses has an important role in maintaining a successful osseointegration and avoiding mechanical complications.5 Establishing an accurate clinical protocol from the impressions to the framework manufacturing is crucial for the prosthesis and the implants to adapt correctly to each other.
Impressions can be made by conventional or digital methods. Several factors influence the accuracy of conventional impressions, including the malalignment of abutment tooth implants.6–9 Computer-aided design and computer-aided manufacturing (CAD/CAM) have become popular.10,11 However, the accuracy of intraoral scanners (IOS) is questionable when they are used for capturing multiple implants distributed along the whole arch.12,13
An alternative to IOS for multiple implant-supported restorations is the photogrammetric system. It collects 3-dimensional (3D) coordinate measurements through photographic images using an extraoral receiver, to record the geometric properties of objects and their spatial position.14,15 This is an accurate technique used in many fields, and it was introduced in dentistry by Lie and Jemt16 in 1994 to study the distortion of implant frameworks.
The aim of this clinical report is to describe the use of the photogrammetric system as an accurate technique to record 3D implant positions of a full-arch maxillary fixed implant-supported rehabilitation.
Clinical Report
A 47-year-old systemically healthy woman visited the University Dental Clinic and requested restorative treatment for her compromised functional, esthetic, and phonetic situation (Figure 1a).
Clinical examination, intraoral photography, radiographic examination, diagnostic cast, and occlusal assessment were performed.
The intraoral examination revealed an existing maxillary metal-resin fixed prosthesis supported by 6 implants (Biomet 3i, Palm Beach Gardens, Fla) that was unfavorably positioned in the anterior maxilla. Generalized mucositis was also observed underneath the prosthesis (Figure 1b). The jaw relationship of the existing maxillary prosthesis was satisfactory and was transferred to the new prosthesis.
A new fixture-level metal-ceramic implant-supported fixed prosthesis was prescribed. After occlusal assessment of the available vertical dimensions, abutments were not inserted.
There were no contraindications to preprosthetic surgery. Before starting the treatment, the patient was informed about the procedure and signed the consent form provided by the university's ethics committee.
Two implants (Nobel Biocare AB, Göteborg, Sweden) were inserted at the posterior region to avoid distal extension in relation to the mandibular arch (Figure 2).
The implants' positions were recorded using a photogrammetry technique (PIC Camera, PiC dental technology, Madrid, Spain). The flag-shaped photogrammetry abutments were screwed into the implants, and photos were taken with the stereo camera (Figure 3a). Based on these flags, the software (Pic Cam Soft v1.1, PiC dental) generated the 3D position of the implants and their angulation in an STL file. In the STL file, position vectors showed the position of the implants in relation to each other. The flag-shaped abutments were then replaced with healing abutments, and a second maxillary digital impression was made (TRIOS Pod scanner, 3Shape, Copenhagen, Denmark) to record the patient's peri-implant soft-tissue profiles in an STL file (Figure 3b). A working maxillary model was generated in dental CAD software (Exocad, Exocad GmbH, Darmstadt, Germany) by aligning and merging the 2 STL files using a best-fit alignment (alignment that matches a set of measured points, as closely as possible to their nominal location or theoretical counterpart) of the implants' positions (Figure 3c).
The mandibular arch, the contour of the existing prosthesis, and its jaw relationship were also recorded by the IOS (Figure 3d). The working maxillary model, the existing prosthesis, and the antagonist mandibular arch were mounted together based on the existing jaw relationship.
A denture try-in was designed and milled from a polymethylmethacrylate resin to evaluate the esthetic parameters, teeth positions, and vertical dimension (Figure 4).
The metal framework was designed with Exocad in STL format and milled and sintered using a cobalt-chromium (Co-Cr) powdered base metal alloy (Figure 5). An angulated screw was inserted in position No. 9 due to the unfavorable angulation of the implants.
The passive fit and occlusion of the framework were checked in the patient's mouth using the Sheffield test, the screw resistance test, the visual fit probe test, and intraoral radiographs.
After all the parameters were confirmed, the technician finished the work with a veneered feldspathic ceramic. First, unglazed ceramic was used to evaluate intraorally the color and the occlusion relations of the prosthesis. Since these were confirmed to be appropriate, the prosthesis was completed. The prosthesis was screwed with the manufacturer's recommended torque (30 Ncm; Figure 6a). The screw access channels in positions 8, 7, 6, and 10 were visible in the buccal area, and pink composite plugs were made and inserted to hide them (Figure 6b and c). These plugs were bonded to the channel with a combination of self-adhesive resin cement (RelyXTM Unicem 2 Automix, 3M, Maplewood, Minn) with a portion of polytetrafluorethylene. Oral hygiene instructions and postoperative instructions on how to care for the new prosthesis were given to the patient.
The patient was followed up at 1 week; 1, 3, and 6 months; and 1 year after the insertion of the definitive prosthesis (Figure 7). No esthetic, biological, or mechanical complications were reported or revealed. Patient satisfaction was obtained in all appointments.
Discussion
In implant treatment, the fabrication of precise frameworks is indispensable for success,17–19 and this requires making reliable impressions and working models.
The photogrammetry system allows clinicians to obtain the exact position of dental implants and to fabricate accurate implant suprastructures.20–23 This technique provides a panoramic view of implants in an arch and therefore is accurate. The presence of blood and saliva does not affect the measurement precision of the PIC camera.20,21 However, photogrammetry does not register the soft tissues, and a second STL file is required to provide this information.20–23
In the reported case, a CAD/CAM framework with a good passive fit was successfully created. At the 1-year follow-up, no mechanical or biological complications were observed. Despite a relatively short follow-up period, this case suggests that the proposed technique facilitates the fabrication of implant-supported fixed prostheses with a passive fit and minimizes posttreatment complications.
The photogrammetry technique is performed quickly, and it seems to be more comfortable for patients than other conventional methods. Further studies are necessary to ensure rigorous scientific support and to determine the advantages of these new technologies.
Abbreviations
Note
The authors declare no conflicts of interest.
