Furcation Involvement and Tooth Mobility

Core Review

Furcation Anatomy and Assessment

What is a furcation? A furcation is the anatomical area where the roots of a multi-rooted tooth diverge. The furcation entrance is the point where the roots begin to separate. The furcation roof (dome) is the internal concave area within the root complex.

Which teeth have furcations?

• Maxillary molars: Three furcations — buccal, mesial, distal
• Mandibular molars: Two furcations — buccal, lingual
• Maxillary first premolars (when two roots are fully separated): One furcation — mesial-distal (between buccal and lingual roots)
• Mandibular premolars and canines: Rarely have separate roots; furcation involvement is uncommon
• Maxillary second premolars: Typically single-rooted; furcation is rare

Furcation entrance location by tooth type:

Root trunk length: The distance from the CEJ to the furcation entrance. Longer root trunks mean more attachment loss is needed before the furcation becomes involved. Shorter root trunks mean the furcation becomes involved sooner.

Furcation anatomy challenges:

• Furcation entrances are narrower than the furcation interior
• Concavities and ridges exist within the furcation
• Accessory canals may be present in the furcation area
• Enamel projections (cervical enamel projections, CEPs) into the furcation area predispose to furcation involvement
• The furcation roof is a concave dome — extremely difficult to instrument

Glickman Furcation Classification

Class I — Incipient Furcation Involvement

• Clinical finding: The furcation concavity can be detected with a Nabers probe, but the probe does NOT enter the furcation significantly
• Horizontal bone loss: <3 mm into the furcation
• Radiographic appearance: Often not visible radiographically. The furcation may appear normal. A slight widening or "fuzziness" of the furcation area may be the earliest sign
• Gingival coverage: The furcation is covered by gingiva
• Treatment: Can usually be managed with non-surgical scaling and root debridement, though access is challenging. Furcation-specific instruments (Nabers scalers, mini-curettes, ultrasonic tips) improve debridement
• Prognosis: Generally good with thorough debridement and maintenance

Class II — Moderate Furcation Involvement (Cul-de-Sac)

• Clinical finding: The Nabers probe enters the furcation but CANNOT pass completely through to the opposite side
• Horizontal bone loss: ≥3 mm into the furcation, but bone remains on the opposite side of the furcation
• Radiographic appearance: May show a radiolucency at the furcation entrance. A triangular radiolucency between the roots may be visible on periapical radiographs. Often more visible on bitewing radiographs if the beam angle is favorable
• Gingival coverage: The furcation itself is still covered by gingival tissue (the "cul-de-sac" is beneath the gingiva)
• Treatment: Non-surgical debridement is more challenging; surgical access (open flap debridement) may improve access. Furcationplasty (odontoplasty/osteoplasty to widen the furcation entrance for better cleansability) may be considered
• Prognosis: More guarded than Class I; requires meticulous maintenance

Class III — Through-and-Through Furcation Involvement (Closed)

• Clinical finding: The Nabers probe can pass COMPLETELY through the furcation from buccal to lingual (or mesial to distal for maxillary molars)
• Horizontal bone loss: Complete — bone has been lost through the entire furcation
• Radiographic appearance: A distinct radiolucency is visible at the furcation. The furcation appears as a dark area between the roots. This is the first class that is clearly visible radiographically in most projections
• Gingival coverage: The furcation is STILL covered by gingival tissue. The probe passes through a tunnel, but when you look clinically, the furcation area appears covered by gingiva. The through-and-through communication is "closed" clinically
• Treatment: Surgical access often indicated. Options include furcationplasty, tunnel preparation (intentional maintenance of the through-and-through opening for cleansability), root resection (removal of one root), or extraction
• Prognosis: Significantly reduced. Long-term maintenance is challenging

Class IV — Through-and-Through Furcation Involvement (Exposed)

• Clinical finding: The furcation is CLINICALLY VISIBLE — the gingiva has receded and the furcation opening is exposed to the oral cavity. A probe passes through easily
• Horizontal bone loss: Complete
• Radiographic appearance: Same as Class III — through-and-through radiolucency
• Gingival coverage: NONE — the furcation entrance is visible (exposed to the oral environment)
• Treatment: Similar to Class III but even more challenging to maintain. Root resection, hemisection (for mandibular molars), or extraction are common treatment options
• Prognosis: Poor without surgical intervention

Key NBDHE distinctions between Class III and IV:

• Class III = through-and-through that you can PROBE but not SEE
• Class IV = through-and-through that you can SEE (gingival recession has exposed it)
• Both have through-and-through bone loss radiographically

Furcation Assessment Technique

1. Use a Nabers probe: A Nabers probe has a curved, calibrated working end specifically designed to enter and navigate furcations. Straight probes cannot adequately explore the furcation concavity

1. Access:
   • Buccal furcations: Approach from the buccal aspect. For maxillary molars, the buccal furcation is typically located slightly distal to the midline of the buccal surface
   • Mesial furcations (maxillary molars): Approach from the buccal aspect, angling the probe toward the mesial surface, slightly palatal to the mesial contact
   • Distal furcations (maxillary molars): Approach from the lingual/palatal, angling distally. Often the most difficult to access
   • Lingual furcations (mandibular molars): Approach from the lingual aspect

1. Technique: Gently insert the probe at the furcation entrance and explore horizontally. Determine (a) whether the probe can enter, (b) how far it enters, and (c) whether it can pass through to the opposite side

1. Record: Document the furcation class for each furcation at each involved tooth

Tooth Mobility

Definition: Tooth mobility is the degree of horizontal and/or vertical displacement of a tooth when force is applied. It reflects the remaining periodontal support and the presence of inflammation.

Miller Classification of Mobility:

Assessment technique: Use the blunt ends of two instruments (e.g., mirror handle and periodontal probe handle). Apply alternating pressure on the buccal and lingual surfaces of the tooth crown. Observe the degree of movement.

Physiologic mobility: All teeth have a small degree of physiologic mobility (0.1-0.2 mm) due to the viscoelastic properties of the periodontal ligament. This is normal and allows the tooth to absorb occlusal forces.

Pathologic mobility results from:

• Loss of alveolar bone support (periodontitis)
• Widening of the periodontal ligament space (inflammation, occlusal trauma)
• Root fracture
• Periapical pathology

Fremitus:

• Fremitus is palpable or visible movement of a tooth during FUNCTIONAL contact (when the patient taps or grinds their teeth together)
• It is assessed by placing a finger on the facial surface of the tooth while the patient closes into maximum intercuspation or performs excursive movements
• Classification: Class I (barely palpable/visible), Class II (easily palpable/visible), Class III (visible to the naked eye with significant movement)
• Fremitus indicates occlusal trauma — excessive forces are being applied to the tooth during function
• This is different from mobility: mobility is assessed by manual manipulation; fremitus is assessed during function

Important NBDHE distinction: Mobility is assessed AFTER resolution of inflammation (post-initial therapy), not before. Inflammation alone can increase mobility (reversible). To determine true mobility due to loss of support, reassess after scaling, root debridement, and inflammation resolution.

Role in Staging (AAP/EFP 2018)

Furcation and mobility findings are complexity factors that influence periodontitis staging:

• Furcation Class II or III: Complexity factor that elevates staging to Stage III (if CAL ≥5 mm and other criteria met)
• Tooth mobility ≥Class II: Complexity factor for Stage IV (secondary occlusal trauma)
• The presence of these factors may shift a case from Stage II to Stage III, or from Stage III to Stage IV, even if CAL and RBL thresholds for the higher stage are met

Clinical Significance and Treatment Implications

Furcation involvement and prognosis:

• Furcation-involved teeth have reduced long-term survival compared to non-furcated teeth
• Class I: Comparable to non-furcated teeth with good maintenance
• Class II: Reduced but acceptable with meticulous maintenance
• Class III/IV: Significantly reduced; 5-10 year survival rates are lower; often require surgical management or extraction

Treatment options by furcation class:

Mobility and treatment considerations:

• Class I mobility: Splinting not indicated; the tooth is generally stable
• Class II mobility without vertical displacement: Splinting may be considered if the patient reports discomfort during function, but is not routinely required
• Class III mobility: Splinting may be indicated for patient comfort and function; however, vertical mobility is a poor prognostic indicator
• Splinting stabilizes teeth but does NOT treat the underlying periodontal disease. It is adjunctive, not therapeutic

Clinical Application

Scenario: Tooth #3 (maxillary right first molar) in a 58-year-old patient. Assessment:

• Buccal furcation: Nabers probe enters 4 mm horizontally. Probe cannot reach the lingual aspect. Furcation is covered by gingiva. → Class II
• Mesial furcation: Probe enters 2 mm. → Class I
• Distal furcation: Not accessible with probe → likely Class I or less
• Mobility: Class I horizontal
• CAL: 6 mm at the mesial-buccal site
• Radiographic bone loss: ~45%

Staging impact: CAL ≥5 mm + Class II furcation → complexity factor for Stage III.

Treatment plan: Non-surgical scaling and root debridement with furcation-specific instruments (Nabers scalers, mini-Gracey curettes, thin ultrasonic tips). Re-evaluate at 4-6 weeks. If probing depths persist or worsen, consider surgical access (open flap debridement). The buccal Class II furcation is a site to watch closely at re-evaluation and maintenance.

Common Traps

• TRAP: Confusing Class III and Class IV furcations. Class III is through-and-through but gingiva still covers the furcation; Class IV is through-and-through with recession exposing the furcation.
• TRAP: Confusing mobility and fremitus. Mobility is passive (clinician manipulates); fremitus is active (patient functions/occludes).
• TRAP: Using a straight probe for furcation assessment. Nabers probe is needed for the curved anatomy.
• TRAP: Assessing mobility before inflammation resolution. Always reassess after non-surgical therapy; initial mobility may be inflammation-related and reversible.
• TRAP: Overlooking mesial and distal furcations on maxillary molars. These are harder to access than the buccal furcation but equally important.