Applicability and accuracy of an intraoral scanner for scanning multiple implants in edentulous mandibles:A pilot study

Statement of problem. In the past 5 years, the use of intraoral digitizers has increased. However, data are lacking on the accuracy of scanning implant restorative platforms for prosthodontics with intraoral digitizers.Purpose. The purpose of this clinical pilot study was to assess the applicability and accuracy of intraoral scans by using abutments designed for scanning (scan abutments) in edentulous mandibles.Material and methods. Twenty-five participants with complete mandibular overdentures retained by 2 implants and frameworks were included in this study. Scan abutments were placed on the implants intraorally and scanned with the iTero intraoral scanner. Also, scan abutments were placed on the implant analogs of the definitive casts and scanned with an extraoral laboratory scanner (Lava Scan ST scanner). Two 3-dimensional computer-aided design models of the scan abutments with predetermined center lines were subsequently imported and registered, together with each of the scanned equivalents. The distance between the centers of the top of the scan abutments and the angulations between the scan abutments was assessed. These values were compared with the measurements made on the 3-dimensional scans ofthe definitive casts, which were the participants' original definitive casts used for fabrication of soldered bars. The threshold for distance error was established to be 100 mu m.Results. Four of the 25 intraoral scans were not suitable for research because the intraoral scanner was not able to stitch the separate scans together. Five of the 21 suitable scans demonstrated an interimplant distance error >100 Rm. Three of the 25 intraoral scans showed interimplant angulation errors >0.4 degrees. Only 1 scan showed both an acceptable interimplant distance (Conclusions. Based on the intraoral scans obtained in this study, distance and angulation errors were too large to fabricate well-fitting frameworks on implants in edentulous mandibles. The main reason for the unreliable scans seemed to be the lack of anatomic landmarks for scanning.