What radiographic feature appears as a dense line surrounding the tooth root?

• A. PDL space
• B. Enamel
• C. Alveolar crest
• D. Lamina dura

Answer: (D)

The dense line surrounding the tooth root on a radiograph is the lamina dura. This is the thin cortical bone lining the tooth socket (the wall of the alveolus) and it appears as a continuous radiopaque border around the root. Immediately next to this border is the periodontal ligament space, which looks like a radiolucent gap between the root and the lamina dura. Enamel covers the crown, not surrounding the root in the socket, and the alveolar crest refers to the top edge of the alveolar bone rather than a border around the root. In a healthy mouth, the lamina dura is a continuous, uniform line; changes in its appearance can indicate pathology.