Functional Anatomy in a Hasanlu (Iran) Dentition: Scallops at the Dentin-Enamel Junction

Abstract

Dental records offer some of the most valuable information for tracing evolution and for verifying identity postmortem (Hillson 1996). The dentinenamel junction (DEJ) is the intersection of two hard structures, dentin and enamel (Brauer, Marshall, and Marshall 2010). The type I, type III and von Korff collagen fibers acting at the junction give stability to the tooth (Lin, Douglas, and Erlandsen 1993; Bishop, Malhotra, and Yoshida 1991; Ohsaki and Nagata 1994). It is thought that a larger scallop area allows for more of the type I fibers to attach to enamel, which would confer stability to the DEJ (Lin, Douglas, and Erlandsen 1993). In this paper, vertical cross sections of the maxillary teeth of a Hasanlu individual's scallops were analyzed by measuring the scallop areas from the cross sections. Canines were found to have a larger log(area) distribution than incisors, molars and premolars. The comparisons of the individual teeth indicated that the log(area) scallop sizes were in most instances the same across the entire dentition. However, the left canines were found to have log(area) values different from right premolar 3, left molar 2, right incisor 2 and right premolar 4. This suggests that it is important to consider individual teeth when making comparisons across the dentition, as right canines did not show significant differences in cases in which left canines did. When the locations of the various scallops within an individual tooth were compared, there were not any patterns indicative of a relationship. This could mean that scallop development within a tooth is unique to an individual, as 11 suggested by Gustafon (1961). Future studies should take into account the various locations in the individual tooth, as scallop areas can vary by location. Comparing the scallop locations of the antimeric pairs showed that there were significant differences in log(area) not only between the labial locations of the canines but also between the mesial and mesial occlusal locations in the second molars. These differences in scallop sizes could be due to the differential development of scallops in these regions. It was also possible that the similarities in most of the antimeric pair locations were a result of the similar architecture of the antimeres at the DEJ. Furthermore, even though there were quadratic, linear and quartic relationships observed, none of these relationships appeared in antimeric pairs. Since only one cross section was taken, the relationship may not have been observed in one of the antimeres. In sections of the teeth where there were lines of best fit for the data, it is likely that the bending of the DEJ dictated the production of scallops. A 3D section of enamel, similar to the one used by Brauer et al., should be used to compare the incremental spacing of the scallops along the length of the DEJ (2010).