What characterizes a class I furcation?

A class I furcation is characterized by the presence of a concavity that can be detected with a periodontal probe, but the probe cannot enter the furcation area. This means that while there is some loss of periodontal attachment that allows detection of the concavity, it does not progress to the point where the probe can pass through the furcation.

This classification is important in understanding the extent of periodontal disease and potential treatment options. It helps dental hygienists and clinicians assess the severity of the periodontal involvement and plan accordingly. The parameters defined in class I furcation help to differentiate it from other classes, such as class II where the probe can penetrate but does not completely pass through, and class III where it can pass completely through the furcation. Class I does not involve clinically visible recession, which is another distinction that helps to define its characteristics.