This chapter deals with dental histology, the study of the microscopic structure of dental tissues: enamel, dentine and cement. There are three important boundaries between them: the enamel–dentine junction (abbreviated to EDJ below), cement–dentine junction (CDJ) and cement–enamel junction (CEJ). Dental histology has considerable potential for archaeology. It can be used to determine age at death. Isolated tooth fragments from one individual can be matched up. A detailed growth sequence calibrated by a daily clock can be investigated. In some mammals, the enamel structure is so complex that it is possible to use it to unravel the course of evolution.
The main tools of dental histology are polarised light microscopy of thin sections and scanning electron microscopy (SEM). Most of the figures in this chapter come from one or the other. Increasingly, confocal light microscopy is being used as well. These are all described at the end of this chapter, together with methods for preparing specimens. The most useful unit of measurement for light microscopy is the micrometre – one micrometre (1 μm) is one thousandth of a millimetre. A human hair is about 100 μm thick, and so is the slice of tooth in most thin sections. In electron microscopy the nanometre is often used as well (1 nm is one tenth of a micrometre).
The inorganic components of dental tissues
Calcium phosphate minerals and their preservation
Living calcified tissues contain between 69% and 99% (by weight) of inorganic material.