Solid index versus intraoral scanners in the full-arch implant impression: in vitro trueness evaluation

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: Full arch implant impression; Intraoral scanners; Solid index; Trueness.

Fig. 1

The reference stone cast model. a The reference model with 8 implants analogs (BT Safe KR®) and b with the proprietary SBs screwed on

Fig. 2

Procedures with the SI. The reference virtual model captured with 7Series® (a) was used to design a SI (b). The SI was tried on the reference stone cast model (c) and therefore used to capture a physical impression (d) of the implant position with polyether (Impregum®). After hardening of the material, the SBs head were made free using a blade (e), the SBs were unscrewed and the SI was removed with all transfers inside. This SI was then turned and the implant analogs were carefully screwed into the SBs (f, g). Then the SI was used to pour a plaster cast (h, i). The implant SBs were not unscrewed and the SI was carefully detached, once again using a blade (j). The SI-derived cast (k) was scanned with a desktop scanner (D15®; Camcube, Montreal, Canada) (l)

Fig. 3

Trueness of the SI-derived and of IOSs-derived models in μm: colorimetric map. In this picture, the best results obtained with each IOS were reported: a CS 3700® (28 ± 24 μm); b Emerald S® (46 ± 34 μm); c SI-derived model scanned with D15® (29 ± 26 μm)