Description of the WALA edge measured in STL and DICOM files

Abstract

The objective of this study was to describe the WALA edge, using STL and DICOM files, contrasting the results with the values given by the authors Will Andrews and Larry Andrews and thus which diagnostic method is the closest to reality. This descriptive observational study included 36 participants, ranging in age from 23 to 33 years, university students, who underwent CBCT computed tomography studies (DICOM files) and intraoral scans to obtain STL models. Two Meshmixer software were used for the STL and 3D Slicer for the CBCT. In both diagnostic methods, for the measurement of the WALA edge, the following was determined: the point of the facial axis (FA), located in the most prominent part of the vestibular coronal center in premolars and in the center of the mesiovestibular sulcus in first molars; the WALA point, located perpendicular to the occlusal plane at the mucogingival junction. The data of the measurements obtained were saved in the Microsoft office Excel 2019 program. The average of the measurements obtained was analyzed using SPSS software for Meshmixer values as well as in 3D Slicer. The results are presented in tables. Statistically significant discrepancies were found for the values obtained from the STL files compared to the CBCT DICOM files especially because the latter only evaluate hard tissues for WALA edge measurements. The values obtained largely resemble the values described by Will Andrews, however, these differ significantly in relation to the unit of analysis of DICOM files the same that lack scientific support to be taken into account as a diagnostic measurement of the WALA edge. Some of the differences in values obtained for WALA edge measurements between different study populations may be due to the fact that several studies use the manual or conventional method and others the digital method and even the same scanner or software used in the digital measurement of models may cause discrepancies in the measurements.