Furcation involvement is a complication of advanced gum disease affecting multi-rooted teeth, such as molars. The furcation is the anatomical area where the roots of a tooth diverge from the main body, known as the root trunk. When periodontal disease causes the supporting bone to recede, this junction becomes exposed to bacteria, creating a defect that is difficult to clean and preserve.
The Anatomy of Furcation
The furcation area is the base of the tooth crown where the root structure begins to split into individual roots. Anterior teeth typically have a single root and lack a furcation area. Posterior teeth, such as mandibular (lower) molars, usually have two roots (bifurcation), while maxillary (upper) molars typically have three roots (trifurcation).
The section of the tooth from the gumline to the point where the roots separate is called the root trunk. The point of separation is the furcation entrance, which is usually a narrow opening, often one millimeter or less in diameter. This small, complex anatomy makes the area highly susceptible to plaque accumulation once the surrounding bone is lost.
Progression of Furcation Involvement
The cause of furcation involvement is the long-term presence of bacterial plaque and calculus, which triggers periodontitis. This chronic inflammation gradually destroys the ligaments and alveolar bone anchoring the tooth. Bone loss begins high on the root surface and progresses downward toward the apex.
As the supporting bone recedes, it eventually resorbs the bone directly between the diverging roots. Once the bone level drops below the furcation entrance, the area is considered “involved,” forming a deep, irregular pocket. This pocket harbors bacteria that are nearly impossible to remove, accelerating the destruction and making the furcation defect a significant risk factor for tooth loss.
Classifying the Severity
Dentists use a standardized grading system to measure the extent of bone loss in the furcation area. Severity is determined by how far a specialized curved instrument, called a Nabers probe, can penetrate horizontally. This classification system uses degrees to describe the extent of horizontal tissue destruction, which is necessary for treatment planning.
The prognosis for the tooth decreases significantly with each increase in grade:
- Class I: The probe detects a slight horizontal groove or concavity but cannot penetrate more than three millimeters into the defect (an incipient lesion).
- Class II: The probe extends more than three millimeters horizontally into the furcation, indicating significant bone loss, but it does not pass completely through to the opposite side of the tooth (a cul-de-sac defect).
- Class III: This is a through-and-through defect where the Nabers probe passes completely from one side to the other, signifying that the inter-radicular bone is entirely destroyed.
- Class IV: This is a through-and-through defect where the furcation entrance is clearly visible because the overlying gum tissue has receded.
Treatment Approaches
Treatment aims to eliminate bacterial infection, smooth root surfaces, and create an anatomy that allows for effective patient plaque control. The chosen method relates directly to the severity of the involvement and the prognosis of the tooth. Early-stage Class I defects are often managed with non-surgical periodontal therapy, such as scaling and root planing, to clean the exposed root surfaces below the gumline.
Minor Surgical Procedures
For Class I and shallow Class II defects, a minor surgical procedure called odontoplasty or furcationplasty may be performed. This involves reshaping the tooth structure by removing small amounts of material to widen or smooth the furcation entrance, making the area easier for the patient to clean.
When the defect is deeper, regenerative procedures like Guided Tissue Regeneration (GTR) may be used, typically for Class II defects. GTR encourages the growth of new bone and tissue using barrier membranes and bone graft materials.
Advanced Surgical Procedures
Advanced Class II or Class III defects often require more radical surgical intervention to save the tooth. Procedures include root resection, where one root is surgically removed while leaving the crown and remaining roots intact, or hemisection, where a molar is cut in half and the diseased half is extracted.
If bone loss is extensive, or the tooth is deemed non-restorable (such as many Class III or Class IV involvements), the ultimate treatment is extraction to prevent further disease progression.