Solid index versus intraoral scanners in the full-arch implant impression: in vitro trueness evaluation
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BMC Research Notes Open Access
RESEARCH NOTE
Solid index versus intraoral scanners in the full‑arch implant impression: in vitro trueness evaluation Francesco Guido Mangano1*, Matteo Bonacina2, Federico Mandelli3 and Fabio Marchiori4
Abstract Objectives: To assess the trueness of a solid index (SI) in the full-arch (FA) implant impression, and to compare it with that of two intraoral scanners (IOSs). A type-IV gypsum model of a completely edentulous patient with 8 implant scanbodies (SBs) was scanned with a desktop scanner (7Series®) to obtain a reference virtual model (RVM), and with two IOSs (CS 3700® and Emerald S®). Five scans were taken with each IOS. Based on the RVM, an SI (custom tray consisting of hollow cylinders connected by a bar) was fabricated and used to capture a physical impression of the model; from this, a second gypsum model was derived and scanned with a desktop scanner (D15®). The SI-derived and the IOSs-derived models were superimposed onto the RVM, to evaluate trueness. Results: The overall mean trueness was 29 μm (± 26) for the SI-derived model, versus 42.4 μm (± 14.7) for CS 3700® and 52.2 μm (± 4.6) for Emerald S®. Despite its limitations (in vitro design, a limited number of models evaluated, RVM captured with a desktop scanner) this study supports the use of SI for FA implant impressions. Further studies are needed to confirm this evidence. Keywords: Solid index, Intraoral scanners, Full arch implant impression, Trueness Introduction Several studies [1–3] and systematic reviews [4, 5] have reported that intraoral scanners (IOS) are not sufficiently accurate to capture impressions in completely edentulous patients, which can be used for the fabrication of fullarch (FA) implant-supported restorations via a fully digital workflow. This inaccuracy seems to depend intrinsically on the IOS, and on the mechanism by which it ‘attaches’ to each other the individual images or frames captured during the scan [6]. The error grows with the stitching of the images and with the progression of the scan [6]. Additional factors that can determine inaccuracy depend on the operator (scanning strategy) [7], patient (number, *Correspondence: [email protected] 1 Department of Prevention and Communal Dentistry, Sechenov First State Medical University, Moscow, Russia Full list of author information is available at the end of the article
position, inclination and depth of the implants) [8], environmental conditions (light) and transfer of the implant position, the so-called scanbody (SB) [9, 10]. The design and materials with which SBs are made, together with manufacturing tolerances, have been documented to cause errors [9, 10]. The congruence between SBs mesh and implant library files can also play a role in determining errors in implant position within the prosthetic computer-aided design (CAD) software [11]. Schmidt et al. [12] used a customised solid index (SI), three-dimensionally (3D) designed and fabricated to capture with little material a high-quality physical impression that recor
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