Analysis of the influence of the facial scanning method on the transfer accuracy of a maxillary digital scan to a 3D face scan for a virtual facebow technique: an in vitro study

Abstract

Statement of problem. With the emergence of virtual articulators, virtual facebow techniques have been developed for mounting maxillary digital scans to virtual articulators. Different scanning methods can be used to obtain 3D face scans, but the influence that these methods have on the accuracy with which a maxillary digital scan is transferred to a 3D face scan is unknown. Purpose. The purpose of this in vitro study was to analyze the influence of the facial scanning method on the accuracy with which a maxillary digital scan is transferred to a 3D face scan in a virtual facebow technique. Material and methods. According to a virtual facebow technique, a maxillary digital scan was transferred to a standard virtual patient—who had the maxillary digital scan in its real location—guided by an intraoral transfer element by using different 3D face scans with the intraoral transfer element in place (reference 3D face scans) obtained with 2 different scanning methods: 10 obtained with an accurate scanning method based on structured white light technology and 10 obtained with a less accurate scanning method based on structure-from-motion technology. For each situation, deviation between the maxillary digital scan at the location obtained via the virtual facebow technique and at its real location was obtained in terms of distance by using a novel methodology. From these distances, the accuracy was assessed in terms of trueness and precision, according to the International Organization for Standardization (ISO) 5725-1. The Student t test with Welch correction was used to determine if the accuracy with which the maxillary digital scan was transferred to the standard virtual patient was influenced by the facial scanning method used to obtain the reference 3D face scans (α=.05).

Results Significant differences (P<.05) were found among the trueness values obtained when using the different facial scanning methods, with a very large effect size. A trueness of 0.138 mm and a precision of 0.022 mm were obtained by using the structured white light scanning method, and a trueness of 0.416 mm and a precision of 0.095 mm were acquired when using the structure-from-motion scanning method. Conclusions. The accuracy with which a maxillary digital scan is located with respect to a 3D face scan in a virtual facebow technique is strongly influenced by the facial scanning method used.