The treatment, management and long-term retention of mandibular molar teeth exhibiting furcation invasions, or FIs, always have been a challenge to the discerning general dentist or dental specialist. This is especially true when the FI has progressed to a Class III furcation. For the purpose of this article, the definition of a Class III FI in a mandibular molar will follow that given by Glickman, as presented in the text by Carranza and Takei.1 They state: "In this type of furcation involvement the interradicular bone is completely absent, but the facial and lingual orifices of the furcation are occluded by gingival tissue, therefore the furcation opening cannot be seen clinically."1(p640) If gingival tissue is apical to the furcation opening and the probe can be passed without difficulty through the furcation and visibly observed in a clinical examination, then a Class IV FI is diagnosed.1 This article will focus on the management of the Class III mandibular molar FI.
With appropriate treatment, root caries in tunneled mandibular molars very well may be less a problem than earlier perceived.
During the past 20 years, there have been a variety of therapeutic approaches to managing Class III mandibular FIs. We will review these, discussing their advantages and disadvantages, then present a case report of a 23-year history of successful treatment with a tunneling procedure in a mandibular molar. The two sections to follow will present approaches to the management of Class III FI of mandibular molars. They are the nonsurgical or conservative method and the surgical or radical method, which is subdivided into total or partial tooth removal with replacement options, guided tissue regeneration, or GTR, and tunneling.
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THE NONSURGICAL OR CONSERVATIVE APPROACH
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The nonsurgical or conservative treatment of mandibular molars with Class III FIs has had a long history, dating back to the early 1950s. In a long-term retrospective study covering a range of 15 to 53 years of conservative treatment (median length of treatment, 22 years), Hirschfeld and Wasserman2 found that repeated instrumentation (subgingival scaling, root planing and gingival curettage) may be important in the long-term retention of mandibular molars with Class III FIs. They found the loss of 77 (10 percent) of 764 treated mandibular molars in 600 patients during this time. This conservative or nonsurgical approach to treatment has been referred to by Ramfjord3 as a blind or "closed" curettage.
Despite reported partial successes of nonsurgical furcation management, several researchers and clinicians since have given accounts for failure of subgingival instrumentation (closed curettage) in treating molar furcations. Bower4 stated that furcal openings of mandibular molars frequently are narrower than the blade of commonly used curettes. In a study of 103 mandibular molars, he found that 50 percent of the teeth had furcation entrances of .75 millimeters or less in width. Within this group, 63 percent of the limited openings occurred on the buccal furcations and 37 percent occurred on the lingual furcations. In this study, the curette blades used were between .75 and 1.0 mm in width. He concluded that owing to morphological complications present in the mandibular furcation, curettes used alone may not be adequate for root preparation, and narrower-diameter ultrasonic débridement tips may be more of an appropriate choice.4
A year later, Waerhaug5 summarized the clinical management of the furcation problem thus: "Subgingival plaque control in the furcation is a total failure because of the inability to gain proper access."
Although successes may continue to be seen or reported in the nonsurgical management of FIs of mandibular molars, innovative and investigative dental minds continually report on ways to either "eliminate," "close" or "open" the furcations of mandibular molars. The following section will explore these alternatives, if the conservative or nonsurgical approach fails to satisfy the patient’s or clinician’s goals.
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THE SURGICAL OR RADICAL APPROACH
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Total or partial tooth removal.
Total removal.
The total removal (extraction) of an involved mandibular molar with a through-and-through FI is one method of treatment. Saxe and Carman6 presented guidelines or indications for this approach. They listed the following conditions for tooth removal:
- – if the molar is unopposed and is the terminal tooth in the arch;
- – if the involved tooth is a solitary distal abutment with mobility;
- – if the offending molar is adjacent to a second molar and second bicuspid with adequate bone support.
Hamp and colleagues7 also stated that extraction is indicated when preserving the affected tooth would not improve the overall treatment plan, or when treatment of the furcation would result in an area that the patient could not clean readily.
One current solution to managing the third condition of Saxe and Carman,6 which is becoming ever more acceptable for replacing single posterior teeth, is the endosseous titanium implant. Misch8 stated that of all available options for replacing single posterior teeth—a removable prosthesis, a resin-bonded fixed partial denture, three-unit fixed restorations, maintenance of the posterior space or endosseous implants—the single-tooth implant generally is the best choice. He concluded that the single-tooth implant exhibits the highest survival rate of the options given—with no reports, as of 1999, indicating the loss of an adjacent tooth with implant placement. Kinsel and colleagues9 also stated that the greater predictability of successful osseointegration of single molar-tooth implants over that of other treatment options is well-documented in the literature. The advantages of the single posterior endosseous implant are improved hygiene, decreased risk of dental caries, maintenance of bone and improved prosthesis longevity, and success rates as high as 97 percent.8
Partial removal.
A less irreversible treatment for a Class III mandibular FI is that of root amputation. This is the removal of one root of the affected molar, with the clinical crown left intact. Although this approach usually is reserved for molar bridge abutments, the clinical crown remains in situ for occlusal function. Another approach to the problem is hemisection, the total removal of the crown portion along with the selected root. Bühler10 stated that hemisection should be considered before every molar extraction, because this procedure can provide a good absolute biological cost savings with good long-term success. In addition, he reported that the failure rates of single-tooth alloplastic (titanium) implants and hemisections are not substantially different. The terms "root amputation" and "hemi-section" are known collectively as "root resection."11
Another approach to treating a Class III FI of a lower molar is called "bisectioning." The clinician splits the mandibular molar vertically through the furcation, without removing either half, leaving two separate roots that then are treated as bicuspids (a procedure termed "bicuspidization").12
Farshchian and Kaiser13 illustrated the success of a molar bisection with subsequent bicuspidization. They stated that the success of bicuspidization depends on three factors:
- – stability of, and adequate bone support for, the individual tooth sections;
- – absence of severe root fluting of the distal aspect of the mesial root or mesial aspect of the distal root;
- – adequate separation of the mesial and distal roots, to enable the creation of an acceptable embrasure for effective oral hygiene.
According to Newell,14 the advantage of the amputation, hemisection or bisection is the retention of some or all of the tooth. However, the disadvantage is that the remaining root or roots must undergo endodontic therapy and the crown must undergo restorative management.
The need for endodontic care before root resectioning or sectioning (bisectioning) has a long history in dentistry. It has remained today as a necessity in treating mandibular molars before the partial removal of their roots or separation of their crowns.15 However, failure to perform endodontic care first is not a contraindication for root resectioning, if it can be determined that a successful root canal filling is practical and possible.16 It has been shown that vital root resections are possible, especially in the maxilla, with symptoms not being manifested until several weeks after the placement of a sedative dressing of choice.17
Provisions also must be made to stabilize the remaining portion of the molar, unless it already serves as a bridge abutment. If an amputation is performed, temporary hypermobility may not be a reason to justify immobilization. According to Polson,18 splinting is necessary only if the mobility interferes with masticatory function or increases progressively. On the other hand, if a hemisection is performed, the remaining root may be used as an abutment for a small bridge; alternatively, it may remain as a single crown or be used as a telescopic crown.19 When a bisection is performed, each segment of the molar created by the bicuspidization should stand on its own, unaided by splinting.13
Guided tissue regeneration.
The principle of GTR was promulgated in the classic 1982 article by Nyman and colleagues20 for treatment of osseous defects in human periodontitis. GTR, as defined by the American Academy of Periodontology in its Glossary of Periodontal Terms, is the "regeneration of periodontal attachment through differential tissue responses. Barrier techniques, using materials such as expanded polytetrafluoroethylene, polyglactin, polylactic acid, calcium sulfate and collagen are employed in the hope of excluding epithelium and the gingival corium from the root in the belief that they interfere with regeneration."21(p44) This concept has been attempted in the treatment of Class III FIs of mandibular molars.
The success of GTR in restoring the lost attachment apparatus in mandibular Class III furcations has been limited, short-lived and fraught with problems. To achieve success of GTR in Class III mandibular FIs, researchers and clinicians have included all22,23 or just some of the following to ensure clinical success: citric acid root conditioning, placement of freeze-dried bone allografts, barrier membranes24–26 or coronal flap positioning.
The one variable that pervades all the studies is the vertical height of bone loss within the Class III FI. Tarnow and Fletcher27 described a subclassification system of furcation classification based on the vertical measurement of bone loss, from the roof or fornix of the furcation to the level of interradicular bone. They are subclass A, a vertical loss of 0 to 3 mm; subclass B, a vertical loss of 4 to 6 mm; and subclass C, a vertical loss of 7 mm or more. Pontoriero and colleagues25 stated that vertical bone loss of more than 3 mm will limit the success of any attempt at GTR of mandibular molars with Class III FIs. Thus, any Class III mandibular furcation with a vertical subclassification of B or C would not be indicated for a GTR procedure.
This last disclaimer most likely has promulgated the statement that very often two or more GTR surgical procedures may be needed to produce additional therapeutic benefits in converting a Class III FI to a Class II FI or better.24 Those reported case studies showing the use and benefit of GTR in mandibular Class III FIs have claimed success by using the terms "furcation closure,"22 "soft-tissue closure,"22,25 "limited success"23 or "complete resolution."24 These coined phrases do not meet or satisfy the definition of GTR as stated by the American Academy of Periodontology in 200121 or match the success of the first human GTR procedure in 1982.20
Garrett and colleagues23 succinctly summarized the GTR approach to treating the mandibular Class III FI thus: "Present available methods do not provide satisfactory results for the majority of cases."
Tunneling.
Tunneling is a periodontal surgical procedure that creates access for patient cleaning and maintenance within the furcal area of a molar tooth that has incurred severe attachment loss owing to periodontal disease. The technique of tunneling has been adequately discussed by several authors.28,29 However, the surgery will be successful only if the following anatomical and clinical features of the molar are present:
- – divergent mesial and distal roots, to allow post-surgical furcal maintenance and cleaning7,16;
- – a short root trunk, which places the root fornix closer to the cementoenamel junction16;
- – proximal bone support, to compensate for any osteoplasty, ostectomy or both when the clinician is establishing harmonious osseous topography in the furcal area (both buccal and lingual)29;
- – an adequate presurgical crown:root ratio, greater than 1:1;
- – either no or minimal tooth mobility that could not be managed by minor occlusal adjustment.
Thus, tunneling is accomplished through a combination of odontoplasty, osteoplasty, ostectomy and associated soft-tissue surgery.28,29 In maxillary molars, it often is accompanied by root resection to make a cleansable bifurcated tooth; in mandibular molars, a Class III furcation is transformed into a Class IV furcation.1 Mandibular molars are most amenable to tunneling.16
A big advantage of tunneling over amputation, hemisection or bisection is the absence of any need for endodontic therapy, for reconstruction of the crown or for an extensive financial commitment.16 Tunneling, however, does have several disadvantages as well: potential development of root caries, sensitivity, exposure of patent lateral canals that will require endodontic therapy in the future, and the requirement that a patient have good manual dexterity to maintain optimal oral hygiene. In addition, mandibular teeth to be tunneled must have sufficient divergent roots to permit interradicular cleansing.16
Hamp and colleagues,7 in a five-year study in which they treated 310 furcated teeth, found that four of seven tunneled teeth developed caries. On the other hand, in a retrospective study of 156 tunneled maxillary and mandibular teeth, Hellden and colleagues30 found that 75 percent of the teeth were caries-free after 8.9 years. More recently, Little and colleagues31 found that 84 percent of tunneled molars (five maxillary and 13 mandibular) were caries-free at six years after treatment.
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CASE REPORT
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The case presented here was reported first in 1983 as a 10-year follow-up of a tunneling procedure of a mandibular right first molar.32 Ten years earlier, the necessary soft-tissue surgery, osteoplasty and ostectomy were performed on a 56-year-old man by one of the authors (R.J.D.). Effective plaque control using pipe cleaners and subsequent interdental-brush débridement of the tunnel had kept the molar root caries-free for 10 years (Figure 1
).
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ABSTRACT
THE NONSURGICAL OR CONSERVATIVE...
