Chairside virtual patient protocol. Part 2: Management of multiple face scans and alignment predictability

Face scans are currently used in dentistry to obtain a virtual patient. Find stable and repeatable references for their matching is a fundamental step. Aim of this study is to evaluate matching reliability of multiple face scans using frontal adhesives references. Null hypothesis was that no significant discrepancy could be detected between the references position analyzed both with surface analysis and linear analysis.

Nine patients were enrolled for this study and nine soft tissue adhesives landmarks (APLI Paper S.A.U, 4 mm Ø) placed, equally distributed, on the forehead and glabella. Patients were digitally scanned with a portable scanner (iPad Pro 3rd Gen. Apple Store, Cupertino, CA, USA) using the software Bellus3D (Inc. Campbell, CA, USA) in maximum intercuspation, with a full smile and with a scan reference device. After the scan procedure, a high-definition polygon file format (.ply) was exported, and linear measurements were collected with MeshLab (MeshLab; MeshLab). In order to further evaluate reference accuracy, a surface analysis was performed using a CAD software (GOM inspect, GOM). 3D deviations were calculated as root mean square. Statistical analysis was performed used two repeated-measures ANOVAs.

Results showed non-significant differences both for linear measurements (p=.22) and surface analysis (p=.58). Frontal references showed to be clinical reliable landmarks for use during face scans alignment, even with different facial expressions.

The proposed technique seems to be suitable for the clinical use when superimposition of several face scans is required.

This study showed the clinical reliability of face scans matching method using adhesives references. These references are cheap and easy to use, allowing for a rapid registration of the patient anatomy.