Human dental tissues: Advancement in virtual dental analysis

The subject of this doctoral dissertation concerns the usefulness of virtual analysis approach in studies of dental tissues and their defects. The real symmetry and perfect balance between opposite jaw halves and antagonistic teeth is not the reality in the masticatory system. The sample of Yuendumu Aboriginal people used in Paper I consists of complete maxillary and mandibular dental arch 3D models from 19 individuals (young and adult). The analysis was carried out on first molars from all quadrants and only individuals with similar levels of wear were selected (76 teeth in total). Virtual methods were applied in order to inspect the palatal arch asymmetries in relation to the alveolar bones inclination and consequently, the alteration of dental crown. Crown alteration (Enamel and Dentine) could be produced by several factors such as masticatory activity, pathological, anthropic and cultural alterations. However, anthropological studies are sometimes not able to distinguish differences among them without an interdisciplinary approach. Particularly, pathological alterations (pits and fissures) are extremely difficult to interpret without microscopy analysis. That is the reason why a virtual approach in dental studies is useful to understand and distinguish any natural or anthropic alteration. Two examples are shown in Paper II and Paper III where two dental treatments discovered in two Italian sites have been described: Villabruna specimen and Fredian shelters. The modern human specimen Villabruna (Paper II) from a burial in Northern Italy is the earliest evidence of dental therapeutic intervention on a Late Upper Paleolithic (ca. 14,000 yr BP). Using Scanning Electron Microscopy (SEM) we showed the presence of striations deriving from the manipulation of a large occlusal carious cavity of the lower right third molar. The striations have a “V’’-shaped transverse section and several parallel micro-scratches at their base, as typically displayed by cutmarks on teeth. Based on in vitro experimental replication and a complete functional reconstruction of the Villabruna dental arches, we confirmed that the identified striations and the associated extensive enamel chipping on the mesial wall of the cavity were produced ante-mortem by pointed flint tools during scratching and chiseling activities. Similar situation was identified at the Fredian shelter (Paper III). The two upper incisors display exposed pulp chambers with circumferential enlargement, chipped dentine on the cavity margins and striations on the cavity walls. Histochemical analysis of the material embedded at the bottom of the cavities revealed a conglomerate of vegetal fibers and probably hairs. Moreover, Fourier transform infrared spectroscopy (FTIR), energy dispersion X-ray spectroscopy (EDS), and Raman microscopy analysis of black residue adhering to the walls of both cavities is consistent with organic substances, specifically bitumen. A direct chronometric date for Fredian 5 confirms a Late Upper Paleolithic context (between 13,000-12,735 calendar years ago). Overall, our results are consistent with in vivo dental drilling to remove necrotic or infected pulp tissue (pulpitis) and the subsequent use of a composite, organic dental filling in the cavity. The conservation of human remains is the main interest of good anthropological research and any organic matter identified within a dental cavity needs to be conserved. This is the topic of paper IV: Letter to the Editor I had written in order to clarify the reason why we have decided to use three different methods (infrared spectroscopy (FTIR), energy dispersion X-ray spectroscopy (EDS), and Raman microscopy analysis) rather than gas-chromatography. Finally, when a tooth does not show any pathological alteration or exhibits a normal/slight wear pattern on the occlusal surface (wear stage 1-2, 3 Smith, 1974) it is possible to obtain information regarding taxonomy based on volume (3D) or areas (2D) of Enamel, Dentine (paper V, VI, VII. VIII) and morphometric analysis of teeth's root (paper IX). This thesis therefore strives to provide a contribution to understanding how virtual approach to dental studies can be used to increase the knowledge of dental tissues and their defects.