Normal Radiographic Appearance of Teeth
Enamel, Dentin, Cementum, Pulp
The teeth are comprised of four basic anatomic structures: enamel, dentin, cementum, and the pulp (Figure 1). The enamel is the layer of mineralized tissue covering the crown of the tooth, which has the highest level of calcified content, approximately 95%.1As a result, the enamel appears highly radiopaque (white) on dental images. Underlying the dense enamel layer is the dentin. The dentin, less calcified than enamel with about 75% mineralized content, composes the majority of the tooth.1 It appears less radiopaque than the enamel due to its lesser mineral content. The dentinoenamel junction (DEJ) is the distinct interface between the enamel and dentin in the coronal aspect of the tooth, while the cementoenamel junction (CEJ) is the interface at the cervical region of the tooth where the crown intersects with the root(s). The cementum covers the root of the tooth but cannot be distinguished from dentin radiographically.2 Finally, the pulp, located in the center of the tooth, contains the nerve and blood supply. The pulp cavity consists of the pulp chamber and pulp canals. The canals are narrow linear structures that extend from the broader pulp chamber and terminate at the end of the root(s). Pulpal anatomy varies, appearing more linear in anterior teeth, while in posterior teeth, the pulp appears like a miniature tooth within the tooth itself. As a non-calcified structure, the pulp appears radiolucent (black) on radiographic images. The size of the dental pulp varies with maturity, appearing larger in children (Figure 2) and more diminished in adults as they age.3
Bitewing radiograph displaying enamel, dentin, and pulp structures.
Periapical radiograph of posterior primary and developing permanent teeth.