Naber’s probe

Assessment instruments

Furcation Nabers probe and furca classification

According to the glossary of terms of the American Academy of Periodontology, a furcation involvement exists when periodontal disease has caused attachment loss and resorption of bone into the bi- or trifurcation area of a multi-rooted tooth.

Various classification systems have been proposed to describe furcation lesions.

  1. Classification of the horizontal component of furcation involvement

In 1975 Hamp, Nyman and Lindhe proposed a classification system referring to the horizontal attachment loss which is based on three classes:

Class I: horizontal attachment loss < 3 mm of the total width of the furcation area

Class II: horizontal attachment loss > 3 mm but not encompassing the total width of the furcation area

Class III: “through and through” destruction of the periodontal tissue in the furcation area

Naber’s probe is used to determine the extent of the horizontal attachment loss in furcations.

Nabers color-coded probe

Color coded furcation probe
Silver and black increments of 3 mm
Used for probing furcation lesions to evaluate severity of horizontal furcation involvement

How to assess furcation involvement with Naber’s probe?

Step I

Assessment of possibility of furcation involvement

Possibility of furcation involvement by detecting the probing depth (PD) with the periodontal probe. Clinical attachment loss of 5mm may be indicative of possible furcation involvement on moral teeth.

Analysing periapical (PA) or panoramic (OPG), bone rarefication or radiolucency in furcation area may indicate furcation involvement.

Step II

Identifying access to the furcation

Maxillary molar teeth have three accesses to furcation:

Buccal access: usually positioned close to the midline of the tooth

Mesial access: positioned closer to the palatal root – use palatal embrasure to access the mesial furcation

Distal access: positioned at the midpoint of distal surface – may use both buccal and/or palatal embrasure to access the distal furcation

Maxillary first premolars have two accesses to furcation: mesial and distal

Mandibular molars have two accesses to furcation:

Buccal and lingual access to furcation, both close to the midline of the teeth

Step III

Identification of the correct end for the corresponding furcation.

While the correct end of the probe is identified, the terminal shank of the probe must be more or less parallel to the occlusal surface of the tooth being examined.

Step IV

Probing technique

Walk the probe in coronal-apical direction from distal to mesial line angles, first use short and then longer vertical strokes to insert the probe deeper into the pocket. Once the probe engages the furcation, apply pressure in horizontal direction to insert the probe into the furcation.


Step V

Assess horizontal involvement/attachment loss

Pilloni & Rojas. Furcation Involvement Classification: A Comprehensive Review and a New System Proposal. Dent. J. 2018, 6, 34; doi:10.3390/dj6030034

2. Classification of the vertical component of furcation involvement

A sub-classification referring to the vertical bone loss from the furcation fornix was introduced by Tarnow and Fletcher (1984) to complement the horizontal classification (I–III):

Subclass A: vertical bone loss 3 mm or less

Subclass B: vertical bone loss from 4 to 6 mm

Subclass C: bone loss from the fornix of 7 mm or more

Periapical (PA) radiogram is used to determine the extent of the vertical attachment loss in furcations.

Step I: Identify fornix of the furcation on PA radiogram

Step II: Divide root length into thirds (measured from the fornix) – cervical, middle and apical

Step III: Identify the level of bone in the furcation

Step IV: Assess the location of the bone loss in the furcation with respect to the root thirds

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