Class III furcation involvement is defined as what?

• A. Through-and-through destruction of periodontal tissue in the furcation
• B. Greater than 3 mm but not through the furcation
• C. Less than 3 mm into furcation
• D. No furcation involvement

Answer: (A)

Furcation involvement classifications describe how far periodontal destruction has reached into the furcation area of a multirooted tooth. Class III means the destruction is through-and-through in the furcation, so a probe can pass completely from one side of the furcation to the other. This indicates advanced interradicular bone loss, which may be obscured by soft tissue if there’s no gingival recession. It’s more severe than the incipient horizontal involvement (Class I) and the partial, non-through involvement (Class II), and it differs from a furcation that is exposed clinically only when recession is present (Class IV). The other options describe measurements in millimeters or no furcation involvement, which do not define this level of furcation destruction.