As described in Chapters 4 and 5, enamel and dentine are marked by microscopic features which preserve evidence of their formation sequence, including a record of disturbances to their development. On the surface are the defects of enamel hypoplasia (Definition Box 7). In microscope sections, there is variation in the prominence of the brown striae of Retzius (but see page 174), often distinguished as accentuated lines or Wilson bands. In the dentine, there may be poorly mineralised bands marked by interglobular spaces (page 104) that are sometimes associated with a deviation of the EDJ and with defects of enamel hypoplasia.

One possible source of confusion is inherited enamel defects, some of which form part of an inherited syndrome affecting several parts of the body and some which are due to factors which affect the teeth alone, such as mutations in the gene which codes for enamel matrix protein. The latter are grouped together as amelogenesis imperfecta and they include both hypoplastic and hypocalcification defects. They yield no information relevant to this book and are so rare (no more than 1.4 per 1000 people) that they are unlikely to be encountered in fossils. In addition, they are recognisable because they tend to affect the whole dentition.