Chairside virtual patient protocol. Part 1: Free vs Guided face scan protocol

Objectives: The 3D facial scan technology allows to virtualize the face of the patient, that can be incorporated with other 3D dental images produced by digital scanning of the dental structures. Aim of this study is to investigate the trueness and precision of a low-cost portable face scanner, with two different scan techniques Materials and methods: Ten patients were enrolled for this study and seventeen soft tissue landmarks were selected to perform linear facial measurements, specifically Reference (Ref), Pronasion (Prn), Subnasal (Sn), Exocanthion Left (Ex-L), Exocanthion Right (Ex-R), Pogonion (Pg), Glabella (G), Alar curvature Right (Al-R), Alar curvature Left (Al-L), Zygion Left (Zn-L), Zygion Right (Zn-R), Orbital Left (Or-L), Orbital Right (Or-R), Tragus Right (T-R), Tragus Left (T-L), Chelion Right (Ch-R) and Chelion Left (Ch-L). Interlandmark distances were measured both manually and digitally. For the manual group ten measurements were made using a digital caliper. For digital group measurements were recorded on the patient face scan obtained using an Ipad Pro 3rd Gen. (Apple Store, Cupertino, CA, USA) and Bellus3D Dental Pro-App (Bellus3D, Inc. Campbell, CA, USA) using "face mode" scan with two different scanning techniques, named Free technique (FT) and Slider Technique (ST). Ten measurements were made for each technique. An open-source software (Meshlab; Meshlab) was used to record all the distances. A paired t-test was used to analyze FT and ST results. In order to further evaluate precision and scan repeatability a surface analysis was performed with both scanning techniques using a CAD software (GOM inspect, GOM) and the total differences in absolute 3D deviations were calculated as root mean square. Results: The comparison between manual and digital measurements showed a mean absolute difference of 0.95 +/- 0.25 for FT and 1.00 +/- 0.29 for the ST. Trueness analysis showed statistically significant differences for the Exocanthion L- Exocanthion R measurement with FT having better performance (P<.05). Precision analysis showed statistically significant differences for G-Pg, Ref-Zn-R and Prn-Zn-R with ST having better performance (P<.05). To achieve all the scans required without any signs of deformation, 184 scans were performed using Free technique and 124 scans using Slider technique. Surface analysis revealed a mean distance of 0.12 +/- 0.45 between Free scans and 0.13 +/- 0.46 between Slider scans in accordance with the linear measurement analysis Conclusion: The study showed that accuracy of low-cost portable scanner can be suitable for clinical use. The use of ST is suggested for a reliable clinical use due to the better precision and an effective reduction of motion artifacts and the lower compliance required to the patients during the scan.