Determining the reproducibility of locating anatomical land marks on human skulls on CBCT for orthodontic measurements

Abstract

INTRODUCTION: The standard process of evaluating craniofacial structures on planar radiographs is being replaced by 3D evaluation using low dose cone beam tomography images. However, current 3D analyses are still using the traditional landmarks from the 2D analysis as references. In the world of 3D, the literature is lacking adequate landmarks that take advantage of the 3-dimensional nature of these 3D images. The objective of the study was to evaluate the reliability and reproducibility of identifying various landmarks specific to a CBCT. These landmarks include points from traditional cephalometric analysis and points which are uniquely found on CBCT. The landmarks were strategically selected in order to represent different parts of the skull utilized in three dimensional cephalometric measurements. METHODS: Fifty CBCT datasets of Skeletal Class I, normodivergent patients without any noticeable craniofacial deformities from a CBCT repository were included in the study. Landmarks were chosen from diverse parts of the skull that ranged from bony landmarks, foramina and the teeth using a 3d prototyping software, Mimics ® v18.0(Materialise, Leuvem Belgium). Three examiners relocated the landmarks three separate times. Coordinates were recorded in the x, y and z axes. Intra- and inter-examiner reliabilities were calculated using the interclass correlation coefficient (ICC) along with the demographic data. RESULTS: Bony protrusions such as the lingulae, and the crista galli or tips of the incisor teeth proved to be the most reproducible with the highest reliability between the three examiners readings. The vast majority of the landmarks had good (>.75) to excellent (>.9) mean ICC. CONCLUSION: Choosing different landmarks specific for CBCTs were found to have good to excellent reliability between examiners who are properly trained to find the points. These points may represent a new type of standard when determining landmarks for 3-D evaluation of the skull.