15. If the furcation is visible and the Nabers furcation probe can pass through the furcation to the opposite side, the periodontitis has progressed to a _______ furcation involvement.
A. Class III B. Class II C. Class I D. Class IV
15. If the furcation is visible and the Nabers furcation probe can pass through the furcation to the opposite side, the periodontitis has progressed to a _______ furcation involvement.
A. Class III B. Class II C. Class I D. Class IV