The most common route for furcation involvement of the maxillary permanent first molar is from:

The loss of inter-radicular bone in the furcation of a maxillary molar may originate from the buccal, mesial, or distal surfaces of the tooth. The most common route for furcation involvement of the maxillary permanent first molar is from the mesial surface of the tooth. The image of furcation involvement is not as sharply defined around maxillary molars as it is around mandibular molars, because the palatal root is superimposed over the defect. However, this pattern of bone destruction is occasionally prominent and appears as an inverted “J-shape” radiolucency, with the hook of the “J” extending into the trifurcation (see Fig. E) or as a radiolucent triangle superimposed over the roots of the involved tooth with its apex pointing toward the furcation (see Fig. 20.10).