A method for studying dental crown and apex position statistics

Human dental arch shape and arch shape variability are investigated using Computed Tomography pictures of 62 patients. Both crown level and radicular apex level data are considered. For each patients, four axial sections parallel to the occlusal plane are selected, in order to be representative of crown and apex part of the dental arches, both in the maxilla and the mandible. Tooth landmarks are located on each of these planes. After standardization of landmark positions, it is seen that landmarks relative to a given tooth cluster into ”‘subclouds”’. Tranforming datapoints into polar coordinates, it is possible to approximtely follow mesio-distal and bucco-lingual directions. It is found that in a direction close to the mesio-distal one, crown subclouds are (for most teeth) significantly narrower than apex subclouds. This is possibly a manifestation of interproximal contact at crown level.