Furcation involvement presents a special challenge to nonsurgical and surgical periodontal techniques, and the management of furcation involvement has to be approached from both periodontal and restorative perspectives. This chapter reviews the challenge posed by furcation involvement, and presents multiple approaches for treatment.
Case
A 44-year-old East Asian female was referred from a local dental hygiene school clinic for periodontal evaluation. She was concerned about the bone loss she had and that the supervising dentist at the hygiene clinic told her that she will lose all her teeth. She had no known medical conditions or allergies, and saw a physician for a check-up 3 or 4 years ago. She described that she had four uneventful pregnancies and that since the last one 5 years ago, her gums bled more frequently. For dental care, she did not see a dentist for about 20 years until she felt she needed a tooth cleaning and sought care at a dental hygienic clinic because of the low cost. Lately, she felt some discomfort when chewing and felt that some teeth (nos. 15, 23 to 25) had become loose. She explained that she brushes her teeth with a soft brush after every meal, and flosses once daily. When questioned, she explained that her husband noticed that she grinds her teeth at night.
Other than periodontal disease the extra and intraoral exams revealed no signs of disease. This was especially pronounced in the upper right quadrant, where tooth no. 3 had deep pocketing and a furcation involvement that appeared to be through-and-through from the mesial entrance to the distal entrance, and a deep buccal furcation entrance (Fig. 7.1).
Initial periodontal findings were as shown here for the upper right quadrant are as follows:
The patient was taught how to use interproximal brushes in the molar area, and scaling and root planning (SRP) was performed, which improved bleeding on probing, but did not otherwise improve the condition and allowed easier detection of furcation entrances:
Periodontal surgery was then performed, which cleaned and reshaped the furcation entrance to remove root concavities, and placed bone graft material. This reduced pocketing more and made the furcation involvement shallower, while also improving radiographic presentation (Fig. 7.1 c).
What can be learned from this case?
This case stresses the importance of comprehensive periodontal treatment in patients with furcation involvement as a combination of nonsurgical and surgical therapy usually is needed to manage furcation involvement. The goal in furcation management is not necessarily to eliminate a furcation involvement, but to be able to create a local environment with low probing depths that can easily be kept clean. While a regenerative approach was successful in reducing pockets and improving radiographic appearance, this case could benefit from further restorative and surgical treatment that improves the shape of the tooth.. However, the patient declined additional treatment, and the furcation involvement presents a long-term risk for continued disease.
Recognize the Effect of Furcation Involvement on Tooth Prognosis
As seen in this case, furcation involvement makes it more likely that pocketing persists after nonsurgical periodontal therapy. Furcation involvement also presents a long-term risk of recurrent periodontal disease activity.
Describing Furcation Involvement
While many furcation classification systems exist, the Glickmann classification is the most commonly used system. For surgical treatment planning, the following characteristics of a periodontally involved furcation are important.
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Association with a bone defect: Bone defects can benefit from regenerative procedures.
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Depth of the defect: Regeneration is more predictable for deep defects (>2 mm deep).
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Bony walls: For furcation involvement, the presence of bony walls may aid the retention of regenerative material and improve the likelihood of regeneration. Typically, bone defects at a buccal or lingual furcation have a single wall fronting the furcation entrance.
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Width of furcation entrance: Narrow (<1 mm) vs. wide:
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Narrow furcation entrances need to be widened surgically. If this is not possible, the chance of treatment success diminishes and extraction should be considered.
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Wide furcation entrances are more conducive to regeneration and SRP. A wide mandibular molar furcation may also allow tunneling of a furcation for oral hygiene access.
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Horizontal depth of furcation:
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Glickmann Class I, “shallow” Glickman Class II furcation: Bone loss in the furcation entrance does not protrude under the pulp chamber (about 1/3 tooth width from buccal/lingual side, or more with increasing age). Tooth shaping (odontoplasty, and biologic shaping) will likely not require root canal treatment.
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“Deep” Glickman Class II furcation: Bone loss in furcation extends under pulp chamber. Odontoplasty will likely require previous root canal therapy. More aggressive forms of tooth shaping such as root amputation or hemisection should be considered.
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Glickman Class III furcation: Chance of regeneration is much reduced.
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Presence of root surface abnormalities such as cervical enamel projection, pearls, ridges:
Challenges Associated with Furcation Involvement
The increased risk of periodontal disease progression of furcation-involved teeth is related to the anatomy of multirooted teeth.
Furcation Anatomy
Any multirooted tooth is at risk for furcation involvement, along with teeth prone to having root deep root concavities:
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Maxillary 1st and 2nd molars: Mid-buccal, distolingual, and mesiolingual furcation entrances.
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Mandibular 1st and 2nd molars: Mid-buccal and mid-lingual furcation entrances.
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Maxillary premolars (especially the 1st) have mesial and distal root concavities.
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Mandibular incisors have mesial and distal root concavities.
The risk for periodontal disease involvement depends on the length of the root trunk, which is the segment of the tooth between the cemento-enamel junction (CEJ) and the furcation entrance. Short root trunks create a risk for early furcation involvement as it takes little attachment or bone loss to expose the furcation to the oral cavity (Fig. 7.2 a).
Fig. 7.2 Furcation characteristics that are associated with furcation involvement. (a) Root trunk configurations can range from short to long, and teeth where the furcation entrances is located in the coronal third of the root are likely to have furcation involvement even with minor attachment/bone loss. (b) Average dimensions of furcation entrances impede use of curettes and often preclude successful nonsurgical treatment of teeth with furcation involvement. (c) Various tooth root surface abnormalities may prevent additional obstacles to SRP furcation entrances. (d) Root surface defects are commonly associated with persistent deep pocketing at furcation entrances. An example is this small enamel pearl near furcation entrance of no. 15 observed during surgery.
The buccal furcation entrance is closest to the CEJ on all molars, making it the easiest to detect. On average, furcation entrances are about 3 mm apical to the CEJ in mandibular molars and almost 5 mm apical to the CEJ in maxillary molars.
The size of the furcation varies considerably between individual teeth. The width of a furcation entrance typically ranges from 0.5 mm near the roof of the furcation to 3 mm at the widest aspect, and the angle created by the tooth roots usually is about 15 to 30 degrees. The depth of the furcation area is about 7–8 mm for molars (from one side to another furcation entrance) and about 3 ½ mm for premolars. For comparison, the blade of a typical new standard-size Gracey curette is 0.9 mm wide and 4 mm long. This makes it difficult to fully clean some furcation entrances with curettes (Fig. 7.2 b) as the blade cannot reach the roof of the furcation, and surrounding tissue usually blocks full entry of the blade into the furcation.
In addition to the limited size of the furcation, root surface abnormalities can make it difficult to access furcation entrances (Fig. 7.2 c) and often are the main contributing factor that leads to local furcation involvement. Root surface abnormalities associated with furcation involvement can include any of the following:
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Cervical enamel projections: Small wedge-shaped tongues of enamel pointed at the furcation entrance, and found on about 80% of all molars with furcation involvement. Most commonly found at mandibular 1st molars, followed by maxillary 1st molars and 2nd molars. Cervical enamel projections are difficult to detect clinically or radiographically, and usually found at surgery.
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Enamel pearls are round, smooth enamel islands on the root surface and can contain dentin and even pulp. Enamel pearls are found in up to 10% of molars and are most common on maxillary first and second molars. Since enamel pearls do not support periodontal attachment, exposure of an enamel pearl by a periodontal pocket results in sudden attachment loss by several millimeters, and they are often associated with severe localized periodontal breakdown.1
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Cementicles are usually found as clusters of small sharp projections on a root surface, and sometimes are associated with molar furcation entrances.
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Bifurcation ridges are dentinal ridges that run across the roof of a furcation entrance and create niches where plaque can hide. There are commonly found on teeth which also have cervical enamel projections.
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Furcation and root concavities: Almost all mandibular molars have root concavities on the mesial and distal root, and these concavities are about 0.4–0.9 mm deep. On maxillary molars, the mesiobuccal root usually contains a root concavity that may be up to 0.7 mm deep, whereas the palatal root is usually convex and the distobuccal root has a flat profile toward the furcation entrance. Given the restricted space of a furcation entrance, root concavities are very difficult to clean completely.
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Accessory root canals opening into the furcation area of molars are found in about half of molars, and may be involved in furcation involvement of teeth with pulpal necrosis.
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Restorations near the furcation entrances can provide an additional locus of plaque collection, and interproximal restorations are associated with an increased risk of furcation involvement.
The effect of these anatomic factors poses several risks to dental treatment, and ultimately tooth survival at the following levels.
Oral Hygiene
At a very basic level, furcation involvement produces concavities and corners on a root surface that may not be accessible to tooth brush bristles, and floss will skip over these concavities as demonstrated in Chapter 5. While interproximal brushes may be able to reach into shallow root concavities, deep, wedge-shaped furcation involvement is beyond the reach of an interproximal brush. While rubber-tipped interproximal stimulators and toothpicks may reach into facial furcation involvement, they also cannot completely clean a furcation entrance, especially if it contains dentin ridges and grooves. Therefore, furcation entrances tend to retain plaque, which leads to a greater likelihood of gingival inflammation, which in turn favors localized attachment and bone loss.
Scaling and Soot Planning
Furcation anatomy is a major impediment to scaling and root planing, as the furcation in about 50–60% of molars is smaller than the blade of a curette. Since the roof of a furcation is almost invariably pointed and narrower than a curette, it is nearly impossible to completely scale and root plane a Class II or Class III furcation involvement with a curette. Ultrasonics tend to do better since the ultrasonic tip is smaller than a curette blade. However, since even the round tip of an ultrasonic insert may not completely fit into a furcation groove, the only solution to make a furcation cleansable is to reshape the roof into a wider round structure with diamond burs.
Abscess Risk
Exposed furcation entrances can become the nidus for a periodontal abscess as they present a small space that can be easily enclosed by soft tissue, and a study found that almost 90% of periodontal abscesses on multirooted teeth were associated with furcation involvement.
Surgical Access
Furcation involvement also poses a surgical challenge since successful periodontal surgery depends on the ability to thoroughly scale and root plane a root surface, which is difficult to accomplish in furcation involvement as already described. In addition, the interproximal location of most furcation entrances makes it challenging to scale and root plane these entrances, place bone graft or place a barrier membrane that can seal these furcation entrances. Consequently, regenerative approaches work less predictably on interproximal furcation involvement of maxillary molars compared to buccal and lingual furcation involvement.
Restoration
Placing a restorative margin on the convex, inward sloping dentin/cementum surface of a furcation entrance is more difficult that placing it in sound enamel coronal to the CEJ. It is also difficult for a laboratory technician to create good marginal fit of metal castings into these areas. Porcelain tends to slump onto margins placed into furcation entrances leading to overhanging restorations unless corrected by the lab technician or dentist prior to crown placement. Moreover, furcation involvement poses a risk for tooth preparation as it is easy to perforate the gingival floor of a cavity preparation overlying a furcation entrance. This then makes it extremely difficult to apply and seal off the cavity preparation with a matrix band, which then produces amalgam or resin overhangs into the furcation entrance.
Effect on Prognosis
While furcation involvement definitely increases the risk of periodontal disease and worsens prognosis, periodontal therapy can maintain teeth with furcation involvement for years. Survival ranges from 77–93% over 10 years after the surgical treatment of the furcation.2 For comparison, the 10-year survival rate of teeth after root canal treatment ranges between 74 and 97%.
Even hopeless teeth with “through-and-through” furcation involvement can occasionally be successfully treated and retained with regenerative therapy.3 It is also possible to maintain these teeth and hold off tooth loss for about 5 to 10 years on average4 with either tunneling procedures that provide oral hygiene access for diligent patients, or with resective procedures that eliminate a diseased root and maintain the function of the tooth. Therefore, teeth with furcation involvement should not be extracted without considering the cost of tooth replacement versus maintaining the tooth with periodontal therapy.
Develop Strategies for Managing Furcation Involvement
Generally, the following strategies exist for treating teeth with furcation involvement:
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Reduce pocketing and reshape tooth (Fig. 7.3).
Fig. 7.3 Treatment planning for furcation involvement other than maintenance “as is” or extraction. If a tooth presents with furcation involvement, deep pocketing and it is desired to keep tooth and improve it with treatment, the next step is nonsurgical periodontal treatment including oral hygiene instruction and SRP. If this fails to resolve pocketing, regenerative surgery should be attempted first for deep infrabony pockets suitable for regeneration as it may improve the condition. If regeneration is not indicated, or did not resolve pocketing, osseous surgery combined with odontoplasty should reshape tooth and surrounding bone of teeth with shallow Class II or I defects. If the furcation has a deep horizontal depth on a maxillary molar, root amputation may eliminate the furcation involvement. For mandibular molars, tunneling can provide oral hygiene access on teeth with shallow root trunks and divergent roots. Otherwise, hemisection can remove the furcation roof in mandibular molars by either removing a root or transforming each half of the tooth into a premolar-like tooth. Hemisection, root amputation, and odontoplasty require a new full coverage restoration for each retained tooth. Root canal therapy and core build-up typically are required after hemisection and root amputation, and may be needed after odontoplasty.
Maintenance “as is”
Maintenance “as is” is the least invasive treatment. Indications are as follows:
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Patient finished SRP, but other initial therapy is still in progress.
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Patient refuses other treatment and understands risk of new disease, tooth loss.
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No other treatment is feasible and patient wants to keep tooth “as is,” understands the compromised nature of tooth and accepts the risk of eventual tooth loss.
If any of these indications apply, routine periodontal maintenance every 3–4 months should be performed. If the tooth with furcation involvement is maintainable, tooth loss is unlikely.
The advantage of this treatment is that it is the least invasive option, and allows further treatment when necessary along with staving off extraction and tooth replacement.
The disadvantage of this treatment is that it only provides definite “treatment” if there is no disease associated with the furcation. In most clinical situations with active disease, periodontal maintenance is just a stop-gap procedure until more definite treatment can be performed.
Extraction
A definite treatment for furcation involvement is extraction. Although hopeless teeth are usually extracted, specific indications for extraction of teeth with furcation involvement include the following:
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Periodontal therapy is unlikely to improve prognosis of tooth and chance of success is too low for patient and dentist. This usually applies to teeth with:
The advantage of this approach is that it will eliminate teeth at risk for future periodontal disease at a low initial cost, and it is a useful approach for simplifying periodontal treatment in arches containing second and third molars with furcation involvement.
The major disadvantage with this approach is the loss of occlusal function and bone that comes with tooth extraction. Tooth replacement is most likely necessary for any teeth other than 2nd or 3rd molars. Tooth replacement is costly with implant therapy the most expensive dental treatment. Moreover, restorations replacing missing teeth most likely need periodic replacement, and pose a risk for recurrent disease. Therefore, for most patients, the goal of dental therapy should be to maintain natural teeth as long as possible.
Combined Pocket Reduction and Tooth Shaping Approach
The goal should be to preserve most teeth with furcation involvement with periodontal and restorative therapy. Indications for the tooth in question are as follows:
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Tooth is of importance to the patient and overall treatment (especially first molars).
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Patient is willing to undergo procedures and willing to maintain teeth long term.
The advantage of this method is that it preserves teeth and function at a relatively low cost and facilitates long-term periodontal maintenance. There is no real disadvantage to this approach.
Pocket-reduction Strategy
Initially, pocket reduction should be attempted with nonsurgical therapy including oral hygiene and SRP, even though this will likely not resolve the furcation involvement. It will, however, simplify the remaining treatment through better gingival health.
For oral hygiene, the following may be effective:
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End-tufted tooth brush for very wide, exposed buccal, and distalmost furcation entrances.
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Small interproximal brushes for insertion into wide, exposed furcation entrances.
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Rubber-tipped stimulators (i.e., GUM Stimudent) for narrow furcation entrances.
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Oral irrigators (with subgingival tip, if available) for any furcation involvement.
For SRP, the following instrumentation may be useful:
Commonly, nonsurgical techniques will not reduce pocketing associated with a furcation entrance. Regenerative techniques should be attempted next, especially if the furcation entrance is associated with a large bone defect. In most cases, this will create a smaller, shallower furcation involvement that is easier to manage for definite treatment, and regenerative treatment is unlikely to worsen furcation involvement. For this reason, regenerative surgery should even be attempted at nonmobile teeth with accessible Class III furcation involvement as long as the patient is willing to undergo this procedure.
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