Lateral Cephalogram Positioning — ORE Part 1 MCQ
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Correct answer: B — Frankfort plane horizontal, teeth in centric occlusion, lips at rest
The standard position for lateral cephalometric radiography in orthodontic assessment requires three key elements: (1) Frankfort plane horizontal—this is the reference plane formed by the porion (upper margin of external auditory meatus) and orbitale (lowest point of orbital rim), positioned parallel to the ground to ensure reproducible measurements and accurate cephalometric analysis; (2) teeth in centric occlusion—this captures true dental-skeletal relationships and is essential for assessing malocclusion severity and treatment planning; (3) lips at rest—a natural, relaxed state avoiding lip strain that would distort soft tissue outline. This positioning is the international standard for orthodontic diagnosis. Option A (head tilt) introduces rotational error; Option C (mouth open) prevents assessment of occlusal relationships; Option D (natural head position with lips apart) is vague and incorrect regarding mouth position; Option E (tilted Frankfort plane) violates standardisation necessary for sequential comparison. The standardised position allows accurate cephalometric analysis, valid inter- and intra-examiner reproducibility, and comparison with population norms.
Reference: Cephalostat for cephalometric roentgenography (US Patent 4,760,591, 1978) and Head orienting device for cephalometric X-rays (US Patent 4,088,893, 1978); also established in orthodontic practice per FGDP/BDA guidance. Positioned consistent with international orthodontic standards documented in systematic reviews of lateral cephalometric methodology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5363936/