In some teeth, there is more than one root canal. The root canal is the narrow tube, full of dental pulp that’s rich with blood vessels and nerves, that enters the bone and keeps the teeth firmly in place and vital. The front teeth usually only have one root canal, but the molars and premolars have two or three root canals that appear as a division in the root of the teeth. This division is called a furcation; when two roots are meeting, their juncture is called a bifurcation, and when three roots are present, it’s called a trifurcation. When bone has been lost, usually due to periodontal disease, at this area where the roots of the teeth converge, a furcation defect is present. Furcation defects vary in seriousness and also location or configuration; each of these factors is an important part of treatment planning. Their location in the mouth may be particularly hard to reach for effective cleaning, leading to furcation defects being ideal sites for periodontal pathogens. This increases the likelihood that these teeth will die or fall out, which often necessitates surgery to either graft the furcation defect closed, or to open a path through the soft tissue to allow greater access for cleaning and maintenance.
A tooth’s root trunk length is the distance between the cementoenamel junction, or the area where the cementum that covers the root of the tooth meets the enamel that covers its crown, and the entrance to the furcation. Depending on the tooth, the root trunk length is usually at least 3 mm and can be as long as 6 mm. This means that at least this amount of bone must be lost before a furcation becomes exposed. This measurement is one of several that are used to classify furcation defects. There are a few different classification systems for furcation involvement, most based on the 1953 classifications delineated by Irving Glickman. According to Glickman’s system, a Grade I furcation defect is characterized by the location of the periodontal pocket, which indicates incipient bone loss and subsequent furcation involvement. Grade II is characterized by the appearance of a minimal probeable area in the furcation entrance, while in Grades III and IV, this involvement is a clearly probeable tunnel that may or may not be occluded by soft tissue. A dental tool called a Nabers probe is used to mechanically check for furcation involvement, and cone beam technology has also been used to detect furcation involvement less invasively. The primary aim of any treatment is to eliminate bacteria from the exposed root surfaces and to determine the most effective anatomical approach for long-term plaque control in the area. For mild grades of furcation, treatment usually includes root scaling and polishing, along with possible root surface debridement or reshaping of the bone or tooth to allow better access for cleaning. In more severe cases, these treatments may also include guided tissue regeneration, tunnel preparation, or root resection. In the most severe cases, when attachment loss is significant and other treatments aren’t likely to yield positive outcomes, extraction of the tooth may be the only option.