In dentistry, a furcation defect is a term used to describe bone loss, usually a result of periodontal disease, affecting the base of the root trunk of a tooth where two or more roots meet. The extent and configuration of the defect are factors in both diagnosis and treatment planning.[1]
Because of its importance in the assessment of periodontal disease, a number of methods of classification have evolved to measure and record the severity of furcation involvement; most of the indices are based on horizontal measurements attachment loss in the furcation.
Grade I – Incipient furcation involvement, with any associated pocketing remaining coronal to the alveolar bone; primarily affects the soft tissue. Early bone loss may have occurred but is rarely evident radiographically.
Grade II – There is a definite horizontal component to the bone loss between roots resulting in a probeable area, but bone remains attached to the tooth so that multiple areas of furcal bone loss, if present, do not communicate.
Grade III – Bone is no longer attached to the furcation of the tooth, essentially resulting in a through-and-through tunnel. Because of an angle in this tunnel, however, the furcation may not be able to be probed in its entirety; if cumulative measurements from different sides equal or exceed the width of the tooth, however, a grade III defect may be assumed. In early grade III lesions, soft tissue may still occlude the furcation involvement, though, making it difficult to detect.
Grade IV – Essentially a super grade III lesion, grade IV describes a through-and-through lesion that has sustained enough bone loss to make it completely probeable.
In 2000, Fedi, et al. modified Glickman’s classification to include two degrees of a grade II furcation defect:[3]
Grade II degree I – exists when furcal bone loss possesses a vertical component of >1 but <3mm.
Grade II degree II – exists when furcal bone loss possesses a vertical component of >3mm, but still does not communicate through-and-through.
In 1975, Sven-Erik Hamp, together with Lindhe and Sture Nyman, classified furcation defects by their probeable depth.
Class I – Furcation defect is less than 3 mm is depth.
Class II – Furcation defect is at least 3 mm in depth (and thus, in general, surpassing half of the buccolingual thickness of the tooth) but not through-and-through (i.e. there is still some interradicular bone attached to the angle of the furcation. The furcation defect is thus a cul-de-sac.
Class III – Furcation defect encompassing the entire width of the tooth so that no bone is attached to the angle of the furcation.[3]
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