Morphological comparison of the enamel–dentine junction and outer enamel surface of molars using a micro-computed tomography technique

Abstract

BackgroundThe basement membrane between the inner enamel epithelium and the dental mesenchyme in the tooth germ is preserved in a fully formed tooth crown as the enamel­–dentine junction (EDJ). The outer enamel surface (OES) is a culmination of enamel deposition above this basement membrane. The EDJ and OES are used extensively in studies of systematics and phylogenetic reconstructions. However, some studies have reported that the morphological features of EDJ and OES are not always consistent. The micro-computed tomography (µCT) technique was recently used to reveal the inner and outer structures in three dimensions, leading to a detailed morphological comparison of the EDJ and OES. HighlightIn this review, we present the µCT-based comparative studies of EDJ and OES morphologies using four morphological indicators: metric, variability, nonmetric traits, and shape descriptors. The results suggested that EDJ and OES morphologies were generally highly correlated but that enamel thickness can affect their morphological correspondence. ConclusionA detailed comparison of EDJ and OES using µCT will contribute to our understanding of the phylogenetic relationships among fossil records and evolutionary changes in dental characteristics from the developmental perspective.