The significance of enamel thickness in hominoid evolution has been plagued by the absence of nondestructive quantitative
analysis. The aim of this investigation was to use a nondestructive method of analysis to document the volume of enamel and
dentin, thereby providing a quantitative method for comparing both extant and extinct hominoid dentition. High-resolution
X-ray computer tomography (HRXCT) is a nondestructive technique for visualizing and quantifying the interior of objects such
as bone, teeth and minerals. HRXCT is also capable of obtaining digital information on their 3D geometries and volumetric
properties. HRXCT differs from conventional medical CT-scanning in its ability to resolve details as small as a few microns
in size, even when imaging objects made of high density materials like enamel and dentin. HRXCT also differs from micro-CT
in its ability to examine large specimens up to 1.5 meters, with higher energy sources (typically 125–450 keV) that make the
instrument capable of penetrating much denser objects including teeth and very heavily mineralized fossils. HRXCT offers several
advantages over both the medical and micro-CT systems. Hominoid teeth used in this study consisted of a collection of extant
hominoids as well as a number of fossil hominoids (Proconsul and Sivapithecus). HRXCT was used to obtain a data set of serially sectioned digitized images at a slice thickness of approximately 50 micrometers
per section. The digital images were analyzed, and 3D reconstructions allowed for the collection of volumetric data for coronal
enamel and dentin. HRXCT provides researchers with capabilities not found in other CT systems, which allows for a wider range
of specimens sizes, with customizable scanning parameters unique to each specimen type. Our results demonstrate that HRXCT
is an effective means by which volumetric data and 3D reconstruction of dental hard tissues are obtained from both extant
and extinct hominoid dentitions.
Keywords 3D reconstruction - HRXCT - enamel thickness - enamel and dentin volumes - hominoids