Furcation Involvement Classifications: A Critical Appraisal and Proposal for a New System
Corresponding Author: Amar Bhochhibhoya, Department of Prosthodontics, TU Dental Teaching Hospital, Institute of Medicine, Maharajgunj, Kathmandu, Nepal, Phone: +977 9804320719, e-mail: firstname.lastname@example.org
Aim and objective: This article aims to emphasize the use of a new classification system with a review of the classification systems devised in the past along with their limitations.
Background: There is a lack of universal acceptance of single classification system for furcation involvement due to certain limitations and drawbacks. So, there is a need for a new approach to address the lacuna in the present classification systems. A thorough literature search was done in Medline/PubMed and Google Scholar to incorporate all the classification systems which have been proposed previously.
Review results: Different classifications have been proposed over different eras, the classification given by Glickman being the most common one. The proposed system is based on the site-specific clinical presentation of the furcation defects and takes into consideration the horizontal and vertical components of furcation as well as its exposure.
Conclusion: The present classification has been underscored which is entirely clinical in nature, avoiding the need for anaesthesia, radiographs and open surgeries. This simple and convenient system will assist the clinical practitioners to record the furcation invasion and aid to visualize the clinical picture of the involved tooth.
Clinical significance: This simple and convenient system will assist the clinical practitioners to record the furcation invasion and aid to visualize the clinical picture of the involved tooth.
How to cite this article: Shrestha R, Bhochhibhoya A. Furcation Involvement Classifications: A Critical Appraisal and Proposal for a New System. CODS J Dent 2021;13(1):11–17.
Source of support: Nil
Conflict of interest: None
Keywords: Classification, Furcation invasion, Proposal.
“Periodontitis is a chronic multifactorial inflammatory disease associated with dysbiotic plaque biofilms and characterized by progressive destruction of the tooth-supporting apparatus.”1 Treatment of periodontitis comprises a wide array of nonsurgical and surgical therapies. Regardless of the contemporary treatment options, therapy becomes additionally complex when the multirooted tooth is affected resulting in furcation exposure.2
A furcation invasion is defined as the extension of periodontitis or pulpitis into a trifurcation area.3 The pathogenesis of furcation invasion commences with the widening of the periodontal space and inflammatory exudation, eventually leading to the epithelial proliferation into the furcation area from the adjacent periodontal pockets.4 Furcation creates a potential niche for bacterial plaque, toxins and calculus accumulation. The anatomy and morphology of the furcation coupled with limited accessibility for instrumentation further increases the possibility of periodontitis. The complexity is heightened by the severe attachment loss resulting in a poor crown-to-root ratio and/or increased tooth mobility.5 In cases of furcation involved tooth, the risk of tooth loss is increased by 2.21–2.54 times in the maintenance phase than in teeth without furcation involvement.6,7
Furcation involvement is more common in maxillary molars than in mandibular molars,8 the prevalence being 25–52% in the maxillary molars and 16–35% in the mandibular molars.9,13 The first molars are more frequently involved than the second molars.14,15 According to the site, the distal of the maxillary 1st molar (53%) are invaded more commonly with the mesial of the maxillary 2nd molar being invaded the least (20%).8
Furcation involvement is a local factor that influences the prognosis of the associated tooth. It is rendered to be of utmost importance to determine the prognosis of the tooth and for the selection of the therapy.16 This, in turn, aids to claim insurance, to depict time and money invested in the tooth and to play a decisive role for the retention of the concerned tooth in cases of complete rehabilitation.17,19 The diagnosis of furcation invasion is made by clinical assessment, probing, transgingival probing, radiographic assessment and open flap procedure. Generally, Glickman’s Class I furcation lesions may be simply treated by scaling and root planing20 or furcationplasty, Class II by regenerative therapy,21,23 Class III and IV by extraction or resective therapy such as hemisection, root resection or tunnel preparation.20,24,26
A thorough literature search was done in Medline/PubMed and Google Scholar to incorporate all the classification systems which have been proposed previously. Many classifications have been described over the years which reveal the extensive researches being done in furcation. Among these classifications, the most commonly used is the Glickman’s classification. Different classifications have been summarised in Table 1:
|Glickman27||Grade I: Pocket formation into the furcation, but intact interradicular bone.
Grade II: Loss of interradicular bone and pocket formation but not extending through to the opposite side.
Grade III: Through-and-through lesion.
Grade IV: Through-and-through lesion with gingival recession, leading to a clearly visible furcation area.
|Goldman28||Grade I: Incipient lesion.
Grade II: Cul-de-sac lesion.
Grade III: Through-and-through lesion.
|Staffileno29||Class I: Furcations with a soft tissue lesion extending to furcal level but with minor degree of osseous destruction.
Class II: Furcations with a soft tissue lesion and variable degree of osseous destruction but not a through-and-through communication through the furca.
Class II F: Furcations with osseous destruction from facial aspect only.
Class II L: Furcations with osseous destruction from lingual aspect only.
Class II M: Furcations with osseous destruction from mesial aspect only..
Class II D: Furcations with osseous destruction from distal aspect only..
Class III: Furcations with osseous destruction with through-and-through communication.
|Easley and Drennan30||Class I: Incipient involvement, but there is no horizontal component to the furca.
Class II Type 1: Horizontal attachment loss into the furcation.
Class II Type 2: Vertical attachment loss into the furcation.
Class III: Through-and-through attachment loss into the furcation.
Type 1: Horizontal attachment loss into the furcation.
Type 2: Vertical attachment loss into the furcation.
|Hamp et al.16||Degree I: Horizontal attachment loss <3 mm.
Degree II: Horizontal attachment loss >3 mm not encompassing the total width of the furcation area.
Degree III: Horizontal through-and-through destruction of the periodontal tissue in the furcation area.
|Rosenberg46||HorizontalDegree I: Probing <4 mm.
Degree II: Probing >4 mm.
Degree III: Two or three furcations classified as degree II are found.
VerticalShallow: Slight lateral extension of an interradicular defect, from the center of the trifurcation in a horizontal direction.
Deep: Internal furcation involvement but not penetrating the adjacent furcation.
|Ramfjord and Ash35||Class I: Tissue destruction <2 mm (1/3 of tooth width) into the furcation.
Class II: Tissue destruction >2 mm (>1/3 of tooth width).
Class III: Through-and-through involvement.
|Goldman and Cohen31||Degree I: Involves furcation entrance.
Degree II: Involvement extends under the roof of furcation.
Degree III: Through-and-through involvement.
|Ricchetti, 1982||Class I: 1 mm of horizontal invasion.
Class Ia. 1–2 mm of horizontal invasion.
Class II: 2–4 mm of horizontal invasion.
Class IIa. 4–6 mm of horizontal invasion.
Class III: >6 mm of horizontal invasion.
|Tal and Lemmer15||Furcation involvement index (FII) scores:
Furcal rating 1: Depth of the furcation is 0 mm.
Furcal rating 2: Depth of the furcation is 1–2 mm.
Furcal rating 3: Depth of the furcation is 3 mm.
Furcal rating 4: Depth of the furcation is 4 mm or more.
|Tarnow and Fletcher40||For each class of horizontal classification (I–III), a subclass based on the vertical bone resorption was added:
Subclass A: 0–3 mm.
Subclass B: 4–6 mm.
Subclass C: >7 mm.
|Rateitschak et al.36||Degree 0: no furcation involvement
Degree I: Probing Attachment Level-Horizontal ≤3 mm
Degree II: Probing Attachment Level-Horizontal >3 mm, but the defect does not encompass the whole furcation.
Degree III: through and through furcation.
|Eskow and Kapin39||Furcation involvement is classified as grade I subclasses A, B, and C (vertical involvement):
Subclass A: Vertical destruction >1/3.
Subclass B: Vertical destruction of 2/3.
Subclass C: Vertical destruction beyond apical third of interradicular height.
|Fedi42||Glickman + Hamp classifications.
Grades are the same as Glickman’s classification (I–IV).
Grade II is subdivided into degrees I and II.
Degree I: Vertical bone loss 1–3 mm.
Degree II: Vertical bone loss >3 mm, but not communicate through-and-through.
|Grant et al.33||Class I: Involvement of the flute only.
Class II: Involvement partially under the roof.
Class III: Through-and-through loss.
|Basaraba32||Class I: Initial/incipient furcation involvement.
Class II: Partial/patent furcation involvement.
Class III: Patent furcation involvement that communicates with 2nd or 3rd furcation opening; i.e., communicating furcation involvement.
|Svadstrom8||Score 0: The furcation site not probeable.
Score 1: The root trunk coronal to the furcation entrance probeable.
Score 2: The tip of the probe passes horizontally into the furcation but does not reach to the center of the furcation area.
Score 3: The tip of the probe reaches to or beyond the center of the furcation area.
|Carnevale et al.37||Degree I: Horizontal attachment loss < 1/3.
Degree II: Horizontal attachment loss > 1/3.
Degree III: Horizontal through-and-through destruction.
|Hou et al.44||Classification based on root trunk length and horizontal and vertical bone loss.
Types of root trunk:Type A: Furcation involving cervical third of root length.
Type B: Furcation involving cervical third and cervical two thirds of root length.
Type C: Furcation involving cervical two thirds of root length. Class I: Horizontal loss of 3 mm.
Class II: Horizontal loss >3 mm.
Class III: Horizontal “through-and-through” loss. Sub-class ‘a’: Suprabony defect. Sub-class ‘b’: Infrabony defect.
|Nevins and Cappetta34||Class I: Incipient or early loss of attachment.
Class II: A deeper invasion and loss of attachment that does not extend to a complete invasion.
Class III: Complete loss of periodontium extending from buccal to lingual surface. Diagnosed radiographically and clinically.
|Glossary of periodontal terms3||Class I: Minimal but notable bone loss in furcation.
Class II: Variable degree of bone destruction but not extending completely through furcation.
Class III: Bone resorption extending completely through furcation.
|Walter et al.38||Degree 0: Furcation not accessible with a periodontal probe.
Degree I: Horizontal loss of periodontal tissue support up to 3 mm.
Degree II: Horizontal loss of support exceeding 3 mm, but no more than 6 mm.
Degree II–III: Horizontal loss of support exceeding 6 mm, but no detectable ‘‘through and through’’ destruction.
Degree III: Horizontal ‘‘through and through’’ destruction of the periodontal tissue in the furcation.
|Fugazzotto45||Class I: Entrance into the furcation proceeds less than half of the horizontal dimension of the tooth.
Class II: Entrance into the furcation proceeds greater than half of the horizontal dimension of the tooth.
Class III: Entrance into the furcation proceeds along the complete horizontal dimension of the tooth, connecting both the buccal and lingual furcation entrances.
Subclass a: Loss of attachment apparatus along less than 25% of the vertical component of the furcation of the tooth.
Subclass b: Loss of attachment apparatus along more than 25% but less than 50% of the vertical component of the furcation of the tooth.
Subclass c: Loss of attachment apparatus along more than 50% of the vertical component of the furcation of the tooth.
|Tonetti et al.41||Subclass A: Attachment loss/bone loss extending to the coronal third of the root.
Subclass B: Attachment loss/bone loss extending to the middlethird of the root.
Subclass C: Attachment loss/bone loss extending to the apical third of the root.
|Pilloni and Rojas48||NEI: The furcation lesion is not clinically exposed. The horizontal attachment loss is 2 mm or less.
NEII: The furcation lesion is not clinically exposed. The horizontal attachment loss is 3 mm or more.
NEIII: The furcation lesion is not clinically exposed. The horizontal attachment loss is total, with through and through opening of the furcation.
EI: The furcation lesion is clinically exposed. The horizontal attachment loss is 2 mm or less.
EII: The furcation lesion is clinically exposed. The horizontal attachment loss is 3 mm or more.
EIII: The furcation lesion is clinically exposed. The horizontal attachment loss is total, with through and through opening of the furcation.
|Rasperini et al.2||A1: Horizontal loss of periodontal support < 3 mm of the width of the tooth with vertical attachment/bone loss extending to the coronal third of the root.
A2: Horizontal loss of periodontal support < 3 mm of the width of the tooth with vertical attachment/bone loss extending to the middle third of the root.
A3: Horizontal loss of periodontal support < 3 mm of the width of the tooth with vertical attachment/bone loss extending to the apical third of the root.
B1: Horizontal loss of periodontal support ≥3 mm of the width of the tooth, but not through and through, with vertical attachment/bone loss extending to the coronal third of the root.
B2: Horizontal loss of periodontal support ≥3 mm of the width of the tooth, but not through and through, with vertical attachment/bone loss extending to the middle third of the root.
B3: Horizontal loss of periodontal support ≥3 mm of the width of the tooth, but not through and through, with vertical attachment/bone loss extending to the apical third of the root.
C1: Horizontal through and through destruction of the periodontal attachment with vertical attachment/bone loss extending to the coronal third of the root.
C2: Horizontal through and through destruction of the periodontal attachment with vertical attachment/bone loss extending to the middle third of the root.
C3: Horizontal through and through destruction of the periodontal attachment with vertical attachment/bone loss extending to the apical third of the root.
Besides these, the furcation involvement chart proposed by Muller and Eger in 199918 shows substantial success in depicting the nature and extent of the furcation involvement.
The classifications proposed previously have added insight to the knowledge of furcation, but are not complete in itself. The classifications given by Glickman,27 Goldman,28 Staffileno,29 Easley and Drennan,30 Goldman and Cohen,31 Basaraba,32 Grant et al. 33 Svardstrom and Wennstrom,8 Nevins and Cappetta,34 GPT3 are narrative in nature. Ramfjord and Ash,35 Hamp et al.,16 Rateitschack,36 Carnevale,37 and Walter et al.38 have considered only the horizontal involvement whereas Eskow and Kapin,39 Tarnow,40 Tal and Lemmer15 and Tonetti et al.41 have considered only the vertical involvement. Both horizontal and vertical components have been included in the classifications given by Fedi,42 Richhetti,43 Hou et al.,44 Fugazzotto45 and Rosenburg.46 Considerations of tooth diameter,39,40 the height of the root trunk,44 the number of remaining bony walls,47 the exposure of the furcation48 have been advocated.
Some of the classifications do not clearly state the categorization of the furcations. They have classified furcation invasion as less than a certain figure, for example, less than two-third or more than two-third, but do not make an attempt to classify the furcation which is equal to two-third.16,35,37,39,46 Classifications have also been done on the basis of radiographic images.38,41 In such cases overlapping of the structures in the maxillary molars creates difficulty in the diagnosis.
Proposed New Classification (Shrestha’s Furcation Index)
This system advocates clinical assessment and classification of furcation defects without the need of anaesthesia, radiographs and surgery. Clinical probing provides fairly accurate dimensions of the furcation involvement and has the advantages of being simple, practical and least expensive among all methods.19
Although open flap surgeries provide the best picture of the furcation, they are not justified for the measurement of furcation depth. Open flap surgeries cause unnecessary discomfort owing to the reentry surgery, which also has possible traumatic effects.49 Vertical and horizontal components have been found to be 0.9–1.1 mm deeper during open flap measurements and probing bone levels.49 This may be due to inter-operator variability during measurement or a more ambitious curettage with unintentional removal of bone effects.49
The proposed furcation index is greatly influenced by the Smith’s index of recession.50 This index tries to overcome limitations of previous classification systems and gives a clear picture of the furcation involvement and ensures that important factors such as the site involved, the horizontal component, the vertical component and the furcation exposure, have been taken into consideration.
Similar to the recession index, the proposed index consists of a letter, followed by two digits separated by a dash and ended with an asterisk, when indicated. The first letter of the proposed classification denotes the site of the furcation involvement. This makes examining of the furcation from all possible sides obligatory. Most classifications do not include this element, which fails to give the complete picture of the clinical presentation. The letters used are M for mesial, B for buccal, D for distal, L for lingual. This specifies the particular site of the furcation involvement and the letters can be easily used for any tooth, including premolars, maxillary molars with two roots or mandibular molars with three roots.
The first digit denotes the horizontal involvement of the furcation (Fig. 1) and the second denotes the vertical component (Fig. 2), the horizontal component always precedes the vertical component. This sequence emphasizes the fact that the actual complexity of the furcation is greatly influenced by the horizontal component rather than the vertical component.
The measurements are made according to the procedure defined by Mealey,17 with some modifications. For the horizontal component, a calibrated Naber’s probe with 3 mm marking is inserted into the periodontal pocket along the root surface to locate the initial fluting of the furcation and the distance between the CEJ and furcation fluting is measured (a). It is then inserted and curved till obstruction is felt (b). The horizontal component of the furcation is recorded to the nearest millimeter as the difference between a and b. It is then classified according to the criteria as mentioned in Table 2.
|0||No horizontal component|
|1||Furcation involvement <3 mm|
|2||Furcation involvement ≥3 mm but not through and through|
|3||Through and through involvement of the furcation|
In cases of through and through lesions, the obstruction is not felt, whereas in exposed furcation, the measurement is made directly from the initial fluting of the furcation. For the confirmation of through and through involvement, use of two probes is encouraged.
For the vertical component, a straight probe with 1 mm marking is inserted into the periodontal pocket along the root surface to locate the initial fluting of the furcation and the distance between the CEJ and furcation fluting is measured (a). The probe is inserted apically until resistance is felt and the distance from CEJ to the vertical depth is noted (c). The vertical component of the furcation is recorded to the nearest millimeter as the difference between a and c. It is then classified according to the criteria mentioned in Table 3.
|0||No vertical component|
|1||Furcation involvement of 1–3 mm|
|2||Furcation involvement of 4–6 mm|
|3||Furcation involvement of ≥7 mm|
The vertical component of the index is followed by an asterisk, which denotes the presence of exposure of the furcation area. In case of non-exposure, the asterisk is omitted. As explained by Tarnow and Fletcher, the consideration of the vertical component is essential as the prognosis of the tooth will definitely be different although being equally probeable in a horizontal plane.40 It aids in the determination of the choice of treatment of root separation, resection, regeneration or extraction.41
Even if there is no furcation involvement, the index should be noted as M0-0, B0-0, D0-0. This will remind the operator not to miss the different sites of the furcations present in a single tooth. The essence of the index is in the recognition of the furcation involvement.
Example: For a maxillary molar the M1-0, B 1-1*, D 1-1 would be the complete index. This indicates less than 3 mm of horizontal involvement in the mesial aspect with no vertical involvement, less than 3 mm of horizontal and vertical component in the buccal and distal aspects with furcation exposure in the buccal aspect.
There is a lack of universal acceptance of single classification system for furcation involvement due to certain limitations and drawbacks. So, there is the need for a new approach to address the lacuna in the present classification systems. The proposed system is based on the site-specific clinical presentation of the furcation defects and takes into consideration the horizontal and vertical components of furcation as well as its exposure. This simple and convenient system will assist the clinical practitioners to record the furcation invasion and aid to visualize the clinical picture of the involved tooth.
It is a site-specific index that would provide qualitative and quantitative information about the furcation and is more objective in its choice of clinical criteria and methodology. Criteria are clear, easy, quickly learned, and is reproducible. It is simple enough to be practicable under a wide variety of field conditions and can be adopted for epidemiological studies. The data offers a rapid appreciation of furcation involvement and understanding of prognosis of the tooth and its treatment needs.
The classification will also help to determine the treatment of the furcation lesion. The treatment options are traditionally determined by the horizontal component of the furcation:
For Score 1: Scaling and root planing, Furcationplasty
For Score 2: Furcationplasty, Regeneration, Tunneling, Root separation and resection
For Score 3: Tunneling, Root separation, and resection, Extraction
But the above treatment options should be modified by the involvement of the vertical component of the furcation.
For Score 1: If the vertical component is deep, regeneration should be considered even if there is less horizontal involvement.
For Score 2: The vertical involvement will determine the invasiveness of the treatment. For less vertical involvement, Furcationplasty, Regeneration should be considered. Regeneration should be recommended when the interproximal bone is coronal to the furcation defect.2 If there is greater involvement of the vertical component, tunneling and root resection must be considered.
For Score 3: Extraction should only be chosen in case of greater vertical involvement of the furcation.
The acknowledgment of the furcation exposure will help to predict the treatment outcome. It has been inferred that scaling and root planing would be more effective in case of clinically visible furcation.48
Overestimation and underestimation are highly probable. Inter and intra-examiner differences exist in measurements of furcation dimensions. The accuracy of probing varies according to the operator’s technique, accessibility to furcation and the ability of the patient to open the mouth.4 Accessibility is hindered by broad contact areas and the presence of neighboring teeth in proximal furcation.
The horizontal readings are subjected to inaccuracy due to geometry when using a curved probe. A change in horizontal depth of 1 mm at tip is smaller than at 1 mm at the edge of the stent.49 But, the use of Naber’s probe is still recommended because a curved probe facilitates access to furcation area, which is influenced by the position of the gingival margin relative to root trunk length, sloping of fornix aperture, and shape of the roof of furcation dome.49
The index does not address factors which are directly involved in furcation involvement such as root concavities, bifurcation ridges, and cervico-enamel projections. Narrow entrances restrict the passage of the probe, which might lead to recording errors. The reference point, the initial fluting of the furcation, may show inaccurate measurement. Other sources of error include interference from calculus, presence of an overhanging restoration or crown contours.51
Different classification systems have evolved in periodontology for furcation invasion. Continuous refinement of these systems with supplementary input provides a broader insight to the practitioner and consequently aids in diagnosis, treatment, prognosis and recording of the disease under consideration. The present classification is the result of an attempt to enhance communication about the detailed information of the furcation invasion to the practitioner. It is easy to use, simple, convenient, and serves as a practical tool both for clinical and research purposes.
The proposed system is based on the site-specific clinical presentation of the furcation defects and takes into consideration the horizontal and vertical components of furcation as well as its exposure.
Rejina Shrestha http://orcid.org/0000-0001-5019-8308
Amar Bhochhibhoya http://orcid.org/0000-0003-2324-5468
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