Operative dentistry: Caries of enamel

Dental tissues:
In mammalian teeth both of enamel and dentine are highly mineralised tissue one providing wear resistance and the other provides fracture resistance, respectively.
Enamel structure:
?Structurally, enamel is composed of millions of enamel rods or prisms, which are the largest structural components, as well as rod sheaths and a cementing inter-rod substance in some areas. The rods are densely packed and intertwined in a wavy spiraling course, and each extends from the DEJ to the external surface of the tooth.
?The structural components of the enamel rods or prism are millions of small, elongated apatite crystallites that are variable in size and shape. The crystallites are tightly packed in a distinct pattern of orientation that gives strength and structural identity to the enamel prisms.
?The long axis of the apatite crystallites within the central region of the head (body) is aligned almost parallel to the rod long axis, and the crystallites incline with increasing angles (up to 65 degrees) to the prism axis in the tail region. The susceptibility of these crystallites to acid, either from an etching procedure or caries, appears to be correlated with their orientation.
Enamel morphology & histology
?Enamel covers the anatomic crown of the tooth and varies in thickness in different areas.
?The enamel is thicker at the incisal area (nearly 2 mm) and occlusal area (2.3-2.5 mm) of a tooth, and it becomes progressively thinner until it terminates at the cementoenamel junction.
?Enamel is formed by cells called ameloblasts, which originate from the embryonic germ layer known as ectoderm.