Frank S Andriessen1, David R Rijkens2, Wicher J van der Meer3, Daniel W Wismeijer4. 1. Postgraduate student, Section of Oral Implantology, Academic Centre for Dentistry Amsterdam, Amsterdam, The Netherlands. Electronic address: f.andriessen@acta.nl. 2. Postgraduate student, Section of Oral Implantology, Academic Centre for Dentistry Amsterdam, Amsterdam, The Netherlands. 3. Assistant Professor, Department of Orthodontics, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands. 4. Professor and Chair, Department of Oral Function and Restorative Dentistry; and Head, Section of Oral Implantology and Prosthodontics, Academic Centre for Dentistry Amsterdam, Amsterdam, The Netherlands.
Abstract
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 of the 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 μm. 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 μm. Three of the 25 intraoral scans showed interimplant angulation errors >0.4 degrees. Only 1 scan showed both an acceptable interimplant distance (<100 μm) and an acceptable angulation error (<0.4 degrees). 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.
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 of the 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 μm. 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 μm. Three of the 25 intraoral scans showed interimplant angulation errors >0.4 degrees. Only 1 scan showed both an acceptable interimplant distance (<100 μm) and an acceptable angulation error (<0.4 degrees). 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.