Trueness and Precision of Economical Smartphone-Based Virtual Facebow Records

Purpose To investigate the trueness and precision of virtual facebow records using a smartphone as a three-dimensional (3D) face scanner. Material and Methods Twenty repeated virtual facebow records were performed on two subjects using a smartphone as a 3D face scanner. For each subject, a virtual facebow was attached to his/her maxillary arch, and face scans were performed using a smartphone with a 3D scan application. The subject's maxillary arch intraoral scan was aligned to the face scan by the virtual facebow fork. This procedure was repeated 10 times for each subject. To investigate if the maxillary scan is located at the right position to the face, these virtual facebow records were superimposed to a cone-beam computed tomography (CBCT) head scan from the same subject by matching the face scan to the 3D face reconstruction from CBCT images. The location of maxillary arch in virtual facebow records was compared with its position in CBCT. The "trueness" of the proposed procedure is defined as the deviation between maxilla arch position in virtual facebow records and the CBCT images. The "precision" is defined as the deviation between each virtual facebow record. The linear deviation at left central incisor (#9), left first molar (#14), and right first molar (#3), as well as angular deviation of occlusal plane were analyzed with descriptive statistics. Differences between two objects were also explored with Mann Whitney U test. Results The 20 virtual facebow records using the smartphone 3D scanner deviated from the CBCT measurements (trueness) by 1.14 +/- 0.40 mm at #9, 1.20 +/- 0.50 mm at #14, 1.12 +/- 0.51 mm at the #3, and 1.48 +/- 0.56 degrees in the occlusal plane. The VFTs deviated from each other by 1.06 +/- 0.50 mm at #9, 1.09 +/- 0.49 mm at #14, 1.11 +/- 0.58 mm at #3, and 0.81 +/- 0.58 degrees in the occlusal plane. When all sites combined, the trueness was 1.14 +/- 0.40 mm, and the precision was 1.08 +/- 0.52 mm. Out of eight measurements, three measurements were significantly different between subjects. Nevertheless, the mean difference was small. Conclusions Virtual facebow records made using smartphone-based face scan can capture the maxilla position with high trueness and precision. The deviation can be anticipated as around 1 mm in linear distance and 1 degrees in angulation.