For summaries of dentine histology see Jones and Boyde (1984), Bradford (1967), Frank and Nalbandian (1989), and Schmidt and Keil (1971). The main bulk of tissue in the crown and roots is called circumpulpal dentine. A thin peripheral layer, under the EDJ, is differentiated as mantle dentine, although it may be so thin as to be indistinguishable even under the microscope. Other distinct layers underlie the CDJ in the roots. Kuttler (1959) further divided dentine development into primary, secondary and tertiary phases. Primary dentine comprised the main period of tooth formation, secondary dentine (page 193) was a slow, regular continued formation, which lined the pulp chamber in adult life, and tertiary dentine patches were laid down to repair damage.

Cells and tubules

Odontoblasts

The cells of dentine are called odontoblasts. Each is cylindrical and 4–7 μm in diameter, with a long, fine process arising from the end, which tapers as it penetrates the full thickness of dentine. The process bears many tiny offshoots along its length, some of which interconnect with the offshoots of other processes. Odontoblasts secrete the initial predentine matrix and mineralize it to produce mature dentine. Once fully differentiated, they do not divide again and each remains viable for the whole life of the tooth.

Dentinal tubules

The odontoblast processes occupy dentinal tubules (Figure 7.1) that radiate out from the pulp chamber, tapering along their length and increasing in spacing (Table 7.1).