In dentistry, a furcation defect is 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.
A tooth with a furcation defect has typically reduced prognosis owing to the difficulty of rendering the furcation area free from periodontal pathogens. For this reason surgical periodontal treatment may be considered to allow vision and access to the furcation.
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 of 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:
- 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.
- 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.
- Ammons, WF; Harrington, GW: Furcation, The Problem and Its Management. In Newman, Takei, Carranza, editors: Carranza's Clinical Periodontology, 9th Edition. Philadelphia: W.B. Saunders Co. 2002. page 826-7.
- Knowles, J; Burgett, F; Nissle, R: Results of periodontal treatment related to pocket depth and attachment level, Eight years. J Perio 1979; 50:225.
- Vandersall, DC: Concise Encyclopedia of Periodontology Blackwell Munksgaard 2007