An Experimental Strategy for Capturing the Margins of Prepared Single Teeth with an Intraoral Scanner: A Prospective Clinical Study on 30 Patients

Purpose : To present an experimental strategy for successfully capturing the margins of prepared single teeth with an intraoral scanner (IOS). Methods : The protocol was as follows: (1) an intraoral impression was captured with an IOS, without taking care of the visibility of the margins; (2) a partial analog impression was taken by means of a 3D-printed custom tray filled with polyvinylsiloxane light, after the removal of a retraction cord; (3) the hollow portion of the analog impression, with the preparation margins clearly visible, was scanned extraorally with the same IOS; (4) the scan of the analog impression was imported into computer-assisted-design (CAD) software, where its normals were inverted; (5) the scan with inverted normals was registered on the first intraoral scan, and replaced it; (6) the technician designed the final restoration, which was fabricated and delivered for application. The study outcomes were: (1) the marginal adaptation of the final crown; (2) the quality of interproximal contacts; and (3) the quality of occlusal contacts. Results : Thirty patients (18 males, 12 females; mean age 51.3 ± 11.6 years) were selected for this study. All these patients were restored with a monolithic translucent zirconia crown, fabricated following the aforementioned protocol. The clinical precision and the marginal adaptation of the crowns were optimal, interproximal contact points were perfect, and the only necessary adaptations were occlusal, with some minor precontacts that had to be polished. Conclusions: The present protocol seems to be compatible with the fabrication of clinically precise zirconia crowns. Further studies are needed to confirm these results.