On a panoramic radiograph (patient on levothyroxine + hydrochlorothiazide), the indicated linear structure (a radiopaque ridge on the buccal/posterior mandible) is most likely:

Correct answer: B. External oblique ridge

• A. The mylohyoid line is on the lingual/internal aspect of the mandible.
• B. Correct (keyed). The external oblique ridge is a radiopaque line running down the anterior border of the ramus onto the buccal mandible.
• C. The inferior alveolar canal is a radiolucent (tube-like) channel, not a ridge.
• D. The mental foramen is a small rounded radiolucency near the premolars, not a linear ridge.