4. Results: Observations and Photo catalogue

The following sections describe the observations made concerning both biological and non-biological diagenetic features, illustrated by micrographs. The histological indexes are reported in Table 2. In addition, results from SEM-analyses in the form of backscatter electron images (SEM-BSE) and elemental spectra (SEM-EDX) are presented.

Figure 2
Figure 2: Schematic drawing of the longitudinal cross-section of a tooth

4.1 Dental microanatomy

Before assessing diagnetic alterations, it is necessary to be familiar with the main micro-anatomical features of teeth as seen in histological thin-sections. Teeth consist of three different types of tissues: enamel, dentine and cementum, as seen in the schematic drawing in Figure 2. The bulk of the element is made up of dentine. The roots are covered with cementum and the crown is capped by enamel. Dentine is avascular and acellular but the tissue is perforated by long odontoblast processes connected to cells within the pulp cavity. These tubuli are similar in diameter to bone canaliculi and connect the dentine to the vascular system. The cementum is partially cellular, containing cementum-forming cells called cementocytes. The enamel is almost entirely inorganic and is a denser and more crystalline material than the other tissues (Hillson 1986). Figures 3 to 7 show micrographs that illustrate micro-anatomical features of teeth as seen in longitudinal cross-sections of whole teeth.

Figure 3
Figure 3: Acellular cementum and dentine. The asterisk marks what is called the granular layer of Tomes. Several interpretations exist for these structures. Recently it has been described as an enamel-like, hypermineralised zone containing little organics (Cherian 2011). Note the thinning of the dentinal tubuli close to the cementum and their fine lateral branches

Figure 4
Figure 4: Cellular cementum with cementocyte lacunae (arrow). These are the lacunae of the former cementocytes, collagen-producing cells that become entrapped in the extracellular matrix they excrete during cementogenesis. The canaliculi of cementocytes communicate but are not part of an inter-connected network that extends all the way to the surface, as is the case for bone. Nourishment is believed to occur by diffusion and the deeper cementocytes may not be vital. Most of the canaliculi point toward the tooth surface (Nanci 2003). The black asterisk marks the cementum surface and the white the granular layer of Tomes at the cemento-dentinal junction

Figure 5
Figure 5: The dentino-enamel junction appear as a well-defined scalloped border (asterisk)

Figure 6
Figure 6: Tufts (arrow) crossing the dentino-enamel junction (asterisk). Tufts appear as hair-thin brushes that branch out from the junction and into the enamel. The tufts contain greater concentrations of enamel proteins than the rest of the enamel (Nanci 2003)

Figure 7
Figure 7: Spindles (arrow) crossing the dentino-enamel junction (asterisk) are remains of odontoblast processes that become trapped when enamel formation begins (Nanci 2003)