Identify radiographic landmark: radiopaque border just above the maxillary dentition on standard maxillary molar view.

Identify radiographic landmark: radiopaque border just above the maxillary dentition on standard maxillary molar view.

• A. Zygomatic arch.
• B. Floor of the maxillary sinus.
• C. Nasal cavity floor.
• D. Inferior border of orbit.

Answer: (B)

The border you see as a radiopaque line just above the maxillary teeth on a standard maxillary molar view is the floor of the maxillary sinus. The maxillary sinus sits above the roots of the upper molars, so its bony floor appears as a distinct, continuous radiopaque line that demarcates the top boundary of the sinus cavity, while the interior of the sinus remains radiolucent. This makes the sinus floor a reliable landmark for orientation on this radiograph. The other structures listed don’t form this specific border in that location: the zygomatic arch is more lateral and higher up, the nasal cavity floor is in a different midline region, and the inferior border of the orbit is superior and medial relative to the molar area.

The border you see as a radiopaque line just above the maxillary teeth on a standard maxillary molar view is the floor of the maxillary sinus. The maxillary sinus sits above the roots of the upper molars, so its bony floor appears as a distinct, continuous radiopaque line that demarcates the top boundary of the sinus cavity, while the interior of the sinus remains radiolucent. This makes the sinus floor a reliable landmark for orientation on this radiograph. The other structures listed don’t form this specific border in that location: the zygomatic arch is more lateral and higher up, the nasal cavity floor is in a different midline region, and the inferior border of the orbit is superior and medial relative to the molar area.