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Radiology · single question

A panoramic radiograph shows a flat or inverted (reverse) smile line. What positioning error caused this?

  1. The patient was positioned too far forward on the bite block
  2. The patient's chin was tipped too far upward
  3. The patient's head was rotated to one side
  4. The patient's chin was tipped too far downward
Show answer and explanation

Correct answer: B. The patient's chin was tipped too far upward

  • A. Forward positioning narrows and blurs the anterior teeth (they sit outside the focal trough).
  • B. CORRECT. Raising the chin (Frankfort plane angled upward) FLATTENS or REVERSES the occlusal plane curve, superimposes the hard palate over the maxillary root apices, and can obscure the maxillary anterior region. Correct positioning has the Frankfort plane parallel to the floor and the ala-tragus line angled slightly down, producing a gentle upward smile curve.
  • C. Head rotation produces unequal magnification, with the ramus and posterior teeth wider on one side than the other.
  • D. Chin too far DOWN produces an exaggerated (excessively curved) smile line and crowds the condyles toward the edges of the film.

Note: Chin up = flat/reverse smile. Chin down = exaggerated smile. Too far forward = narrow anteriors. Too far back = wide, blurry anteriors.

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