Based on radiographic appearance, what is the observed relationship between the CEJ and the roof of the furcation in molars?

• A. A short waist distance (<2 mm)
• B. A moderate waist distance (2–3 mm)
• C. A long waist distance (≥4 mm)
• D. No measurable waist distance

Answer: (C)

In molars, the furcation roof sits below the level of the CEJ on a radiograph, so the vertical gap between the CEJ and the furcation roof—the waist—tends to be several millimeters. This typical separation yields a long waist distance, about 4 mm or more. That’s why the best description is a long waist distance (≥4 mm). Shorter gaps would imply the furcation is much closer to the CEJ than is usually seen, and expecting no measurable waist doesn’t fit the normal radiographic anatomy of molars.