D1 Structural Diagnosis

Topic

The structural diagnosis assesses the physical integrity of dental and supporting tissues: dental enamel, dentin, root cementum, the periodontal ligament, and alveolar bone. To evaluate the physical integrity of these tissues, the structural diagnosis employs various imaging and measurement methods, each sensitive to a different aspect of the same set of dental and supporting tissues.

The most widely used methods are periapical and panoramic radiography; these reveal alveolar bone loss, the depth to which a carious lesion has penetrated the tooth, and the condition of the root apices at the root ends.

Unlike periapical and panoramic radiography, which provide only a two-dimensional projection of the alveolar bone, cone-beam computed tomography allows for a three-dimensional assessment, revealing the bone's internal structure across all three spatial dimensions rather than just its projected silhouette.

To detect a carious lesion before it is visible to the naked eye, two optical methods are also available that examine dental enamel in different ways: fiber-optic transillumination detects a lesion based on differences in the amount of light passing through the enamel, while a laser fluorescence-based method detects the same lesion by measuring the fluorescence emitted by demineralized enamel tissue when illuminated by a laser.

Periapical and panoramic radiography are able to distinguish between different tissues because each tissue's radiopacity—the extent to which it blocks X-rays—is proportional to its density and effective atomic number: the denser the tissue and the higher its effective atomic number, the more radiopaque it appears on the radiograph. Alveolar bone loss revealed by radiography is measured in millimeters, using the distance between the tooth's cemento-enamel junction and the alveolar bone crest as a reference: the greater this distance, the greater the alveolar bone loss in that area.

The degree of dental enamel demineralization is determined quantitatively via a surface microhardness test: the more demineralized the enamel, the lower the measured surface microhardness, as mineral loss renders the enamel softer and more susceptible to scratching.

Collectively, these methods yield a consistent set of variables measured across dental and supporting tissues: radiopacity, bone mineral density, periodontal pocket depth, carious lesion depth, and enamel microhardness. Based on these measured variables, the structural diagnosis establishes derived values—such as the degree of bone loss, a stage classifying the severity of a carious or erosive lesion, and a structural safety factor—that summarize the physical integrity retained by the tooth and its supporting tissues in the face of potential failure.

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