Which statement best describes the anatomy of a Grade II furcation defect?

• A. It can be probed into the furcation but cannot pass through
• B. It cannot be probed into the furcation
• C. It extends through to the opposite side of the tooth
• D. It involves three walls of bone

Answer: (A)

Probing into the furcation area to assess horizontal bone loss between roots is how we classify furcation defects. A Grade II furcation defect means there is horizontal loss that creates a definite furcation entrance, so a probe can be inserted into the furcation, but the path cannot extend through to the opposite side of the tooth—there’s still some bone remaining separating the openings from the other side. This distinguishes it from a through-and-through defect, where the probe can pass from one side of the furcation to the other, and from an incipient or shallow involvement, where the furcation entrance isn’t accessible for probing. The option describing three walls of bone isn’t the defining feature here; the grade focuses on whether probing into the furcation is possible and whether it can pass through.