Furcation Involvement and Mobility Index
_________________________________________
Furcation Index
Stage 1 (F1):
Furcation 1 involvement exists when a periodontal probe extends less than half way under the crown in any direction of a multirooted tooth with attachment loss.
Stage 2 (F2):
Furcation 2 involvement exists when a periodontal probe extends greater than half way under the crown of a multirooted tooth with attachment loss but not through and through.
Stage 3 (F3):
Furcation exposure exists when a periodontal probe extends under the crown of a multirooted tooth, through and through from one side of the furcation out the other.