The Challenge of Furcations

Initial nonsurgical periodontal therapy and periodontal maintenance procedures for furcation areas can be challenging. Recognizing furcation anatomy and selecting the appropriate instruments are paramount for success in these areas. Use of the endoscope is particularly appropriate because tactile sense with an explorer alone is difficult due to root topography and tissue tone. The presence of furcation involvement seriously compromises the future prognosis of the tooth and makes detection by the dental hygienist at the earliest possible point during nonsurgical periodontal therapy imperative. These areas must be meticulously debrided (root planed) to enhance healing and improve longevity of the tooth and dentition.

CLASSIFICATION SYSTEMS

The morphology of the furcation is usually described by the entrance or roof and its distance from the cemento­enamel junction (CEJ), called the root trunk. Multiple systems are available to classify furcations. One of the most common systems is based on four grades.¹

Grade I furcation involves the soft tissues and is the earliest stage of involvement. The pocket is suprabony, increased pocket depth may be present, and radiographic changes are usually not detected.

In Grade II, the furcation has a horizontal component, can be accompanied by a vertical defect, and is usually, although not always, radiographically visible. It can affect one or more of the furcations on the same tooth, although these defects do not communicate (connect) to one another. With Grade III, the bone is not attached to the roof or dome of the furcation. Radiographically, a radiolucent area is visible at the roof of the furcation and a probe should pass through the furcation, depending on soft tissue location adjacent to the furcation.

Grade IV is when the soft tissue has receded and the interdental bone is destroyed. A periodontal probe is easily passed from one aspect of the tooth to another and the furcation is radiographically and clinically visible.

A standardization meeting with oral health professionals working in a clinical setting is valuable to assure calibrated periodontal charting of furcations during dental hygiene care. Accurate classification is significant because healing will be measured by referring to the initial and subsequent recordings of furcation location, classification, and corresponding pocket depth.

ANATOMY

The clinician should mentally visualize the location of the CEJ location in relation to the furcation, the presence of enamel projections, the width of the separation of the roots, the vertical and horizontal dimensions of the furcation, and the relationship of the gingiva to facilitate quality instrumentation.

The further away a furcation entrance is from the CEJ, the less likely it is to become diseased. However, once disease is present, the area will be more difficult to reach. A furcation area is suspected when as little as a 4 mm probe depth is recorded on a multirooted tooth with normal gingival contour. In some cases, especially mandibular molars, bifurcation is located only 3 mm from the CEJ and invasion can occur with attachment loss of 2 mm to 4 mm.

Enamel projections can be mistaken for calculus because they feel like round convex areas. Usually a periodontal pocket presents adjacent to the enamel projections because of retention of bacterial biofilm due to the convex area. Ninety percent of mandibular molars with isolated involvement of the furcation have enamel projections.² The overall prevalence of these projections is 28.6% in mandibular molars and 17% in maxillary molars.² Referral for surgical evaluation might be indicated for the area.

The width of the separation of roots is important in instrument selection. The mandibular second molar roots are not well separated, making detection and deposit removal difficult. First molar teeth only exhibit a .75 mm to 1 mm furcation entrance diameter, therefore, access with a probe or curet is limited.³ The smaller the furcation diameter, the poorer the prognosis is due to the difficulty with instrumentation.³ The blade face width of universal and area-specific curets is from .75 mm to 1.1 mm. This is why treating the furcation with nonsurgical therapy is so difficult, especially on maxillary teeth where the molar entrance diameter is from .5 mm to .75 mm or less.

The width and depth of the periodontal pocket in between the roots are also important aspects of instrumentation. The extent of the destruction determines if nonsurgical or surgical intervention is indicated. It also impacts the type of aid recommended for the patient’s self-care. Maxillary and mandibular molars are lost more often than single rooted teeth partially due to the presence of furcations.

In visualizing the internal concavities of furcation of first molar teeth (Figure 1), note that the depth of the concavities (from .1 mm to .7 mm) hinders deposit removal. The maxillary first molar also has root divergence of the buccal roots toward the palatal root. This divergence further limits access to the already narrow furcation entrance. The internal distance between the mesial and distal roots of mandibular first molars is also limited.³

Lastly, the location of the gingiva to the furcation entrance affects instrumentation and self-care for the patient. A furcation that is exposed because of loss of attachment is easier to access for instrumentation than if the furcation is occluded with gingiva. Sometimes surgical intervention is recommended to create an environment that can be cleansed by the patient and treated by an oral health professional.

INSTRUMENT SELECTION

An explorer 11/12 shaped like an area-specific curet with an extended shank is an ideal choice for shallow and deep pockets adjacent to furcations. Also, a curved explorer that is shaped like a universal curet is effective, especially in reaching the internal aspect of a Grade II or more furcation because of its long and thin working end. A 3A Explorer is another choice specifically designed for deep pockets (5 mm or greater). If periodontal probes are used to detect and classify furcations, their diameter (average is .6 mm) should be compared to the diameter of the furcation entrance to evaluate if access can be obtained.

The small diameter Hirschfeld file is a great instrument for tenacious deposit because of its ability to adapt to surfaces, although the curved internal surfaces of the furcation present a challenge in adapting files. Files might be indicated to initially fracture deposit, with final deposit removal facilitated by curets and/or ultrasonic precision thin inserts. Files are also used for burnished calculus and when ultrasonic instrumentation is contraindicated.

Curets with area specific shanks, particularly the posterior Gracey curets, are commonly used for furcations. Straight-shanked area-specific curets can also be used on each root of a multirooted tooth. Additionally, the mini-bladed and extended shank versions are appropriate for use with furcations. For example, the mini-bladed area-specific curets are ideal for the roof of the furcation and for depressions or concavities within the furcation. Extended shank curets are indicated for 5 mm pocket depth or greater because of the 3 mm longer shank length than the traditional area-specific as well as the narrower working end. The universal curet might also be a choice, especially one with a long, narrow working end. Diamond-coated instruments can also be used to finish surfaces in furcations and root depressions using very light pressure after curet use. They are used for polishing root surfaces, especially during endoscopic evaluation, and are not indicated for heavier deposit removal. Multidirectional strokes are recommended. Another option is furcation curets specifically designed for treating root concavities and furcations.

Subgingival ultrasonic inserts are effective for biofilm debridement and nontenacious deposit in furcations because of the small diameter and ability of the tip to function on two or more sides. The ball-end ultrasonic inserts and tips are specifically designed for furcations. At the end of the tip is an .8 mm ball that is adapted to the curvature of the furcation. Areas under the roof of the furcation are challenging to totally debride with the ultrasonic as well as internal depressions and grooves. Follow the use of the ultrasonic insert subgingivally with a curet, as needed.

INSTRUMENTATION

Treating each root as a separate tooth, if access permits, with a combination of horizontal, vertical, and oblique strokes is recommended. First, the distal surface is treated and then the buccal/lingual surface and mesial are instrumented, ensuring there are multiple overlapping strokes on the surfaces where the roots meet. Next concentrate on the concavity coronal to the furcation entrance by incorporating horizontal and oblique strokes with a toe-down approach where the internal portions of each root meet the root trunk (Figure 2). Use of a mini-bladed curet is a valuable option in this concavity.

Treating each root separately is not feasible if the gingiva occludes the furcation, the periodontal pocket is shallow, or the furcation entrance is barely detectable. Instead, treat the root with a combination of strokes and instruments using a toe-down approach to treat the concavity coronal to the furcation and the limited opening.

Maxillary molar mesial and distal furcations present a unique challenge. Access to mesial molar furcations is best from the lingual surface because the furcation entrance is located lingually and not directly in the midline. An area-specific mesial surface design and a universal instrument with a long terminal shank might work best in this area. The distal entrance, however, is located toward the midline of the tooth so approaching it with a distal area-specific and/or a universal curet from both the lingual and buccal provide equal access to the furcation. When furcation involvement is present on the maxillary proximal surfaces, extreme pivoting of instruments are indicated to reach the defect.

Plan how to select and implement different instruments for treatment of furcations. Strive to try new instruments to improve care and to incorporate life long learning into practice. Re-evaluation of the patient at a 4 to 6 week interval after initial nonsurgical periodontal therapy and during maintenance care is important to evaluate healing in the area(s). Also at these times the clinician has the opportunity to detect subgingival burnished deposit and assess the need for referral for surgical intervention for the patient’s long-term welfare.

REFERENCES

1. Newman MG, Takei H, Carranza FA, Klokkevold PR. Clinical Periodontology. Philadelphia: Saunders, 2006.
2. Masters DH, Hoskins, SW. Projection of cervical enamel into molar furcations. J Periodontol. 1964;35:49-53.
3. Bower RC. Furcation morphology relative to periodontal treatment. J Periodontol. 1979;50:23-27, 366-374.
4. Hodges K. Concepts in Nonsurgical Periodontal Therapy. Florence, Ky: Cengage Delmar Learning 1997:262, 310, 275.

From Dimensions of Dental Hygiene. February 2008;6(2): 34-36, 38.