**7. Furcation involvement**

Definitive diagnosis of furcation involvement is made by clinical examination, which includes careful probing with a specially designed probe (e.g., Nabers). Radiographs are helpful, but root superimposition, caused by anatomic variations and/or improper technique, can obscure radiographic representation of furcation involvement. As a general rule, bone loss is greater than it appears in the radiograph. A tooth may present marked bifurcation involvement in one film but appear to be uninvolved in another. Radiographs should be taken at different angles to reduce the risk of missing furcation involvement [31].

The recognition of a large, clearly defined radiolucency in the furcation area is easy to identify but less clearly defined radiographic changes are often overlooked. To assist in the radiographic detection of furcation involvement, the following diagnostic criteria are suggested [32]:

