Radiographic Considerations Before the Endodontic Treatment Is Initiated
A correct diagnosis is the foundation of an effective treatment plan, and in endodontics, the dental radiograph is an indispensable diagnostic tool. Interpreting images on a radiograph requires an understanding of anatomy, tissue physiology and pathophysiology, and radiographic physics. It is for this reason that these topics will be briefly reviewed in this chapter dealing with the radiographic expression of endodontic disease. Furthermore, they will be discussed as they relate to two-dimensional or standard radiography. While three-dimensional radiography, as generated by cone beam tomography, has been shown to be more effective in imaging endodontic disease than standard radiography (Patel et al., 2009; Scarfe et al., 2009), it has yet to achieve wide acceptance in everyday clinical practice. This is not to imply that it is not in use in some dental practices, only that the current expense associated with its purchase and the special knowledge associated with the interpretation of its images has limited its use. At present, it is found primarily in dental specialty offices and teaching institutions.
Anatomy of Dental Tissues
Teeth are composed primarily of dentin, with an enamel cap over the coronal portion and a thin layer of cementum over the root surface. Tooth enamel is the hardest and most highly mineralized substance of the body and with dentin, cementum, and dental pulp is one of the four major parts of the tooth.
Enamel appears more radio-opaque than other tissues because of its 90% mineral component that causes greater attenuation of X-ray photons.
The dentine will have 70% mineral content. It is less radio-opaque than enamel; its radio-opacity is similar to bone, and the enamel–dentinal junction appears as a distinct interface separating these two structures (Torneck, 1998).
The dentin–pulp complex, the periodontium and the bone of the maxilla and mandible constitute the endodontic tissues (Figure 5.1). The dentin–pulp complex is a specialized connective tissue with dentin-forming capabilities that define what is referred to radiographically as the pulp space (Figure 5.2A,B). The pulp space, in turn, is divided into the pulp chamber or coronal pulp space, and the root canal, or radicular pulp space. The dentin–pulp complex receives its blood supply via channels that extend through the dentin wall of the tooth root from the periodontium (Torneck, 1998). The major channel is called the apical foramen and is located at or near the anatomical end of the root or apex. It is usually, but not exclusively, the largest of the vascular channels. However, despite its relatively large size when compared to the other vascular channels, it is difficult to image on a radiograph for most adult teeth. The other vascular channels present in the dentin are referred to as accessory and lateral canals. These are found at different sites along the root surface, as well as in the furcation area of multirooted teeth. Channels in close proximity to the apical foramen are often called accessory canals while those located more coronally are called lateral canals. Lateral canals vary in size from very small (0.1 mm) to sizes that approach that of the apical foramen (0.4 mm). Varying methods in identifying the presence of lateral canals in anatomical studies have led to varying reports in their incidence. Suffice it to say that most teeth have one or more canals of this type and that they can play a significant role in/>