A reverse smile line observed on a panoramic radiograph is most likely caused by which positioning issue?

• A. The chin position was too high
• B. The chin position was too low
• C. The tongue was not pressed to the palate
• D. The patient wore a necklace

Answer: (A)

Panoramic imaging relies on placing the jaws within the machine’s focal trough so the curved line of the teeth is recorded accurately. When the chin is positioned too high, the mandible sits upward in the focal trough and the anterior teeth move outside the ideal imaging zone. This projection reversal makes the line formed by the incisal edges curve in the opposite direction from a normal “smile line,” producing a reverse smile line on the radiograph. Other listed issues cause different artifacts: not pressing the tongue to the palate mainly creates a radiolucent band over the anterior palate, jewelry creates stray metal artifacts, and chin positioning that’s too low distorts the image in other ways rather than specifically creating a reverse line.