8.1 Introduction

Management of teeth with furcation involvement (FI) has always been a challenge for the clinician. Multi-rooted teeth are difficult to treat and maintain due to the complex anatomy that enhances plaque accumulation and limits access for instrumentation and oral hygiene [1]. In addition, tooth-related factors such as enamel projections (Fig. 8.1) and accessory pulpal canals contribute to FI [2]. Unfortunately, furcation lesions respond differently to periodontal treatment than do flat surfaces [3]. Furthermore, longitudinal studies of periodontal therapy have demonstrated that the prognosis for teeth with FI is worse following traditional scaling, and they are at higher risk of future attachment loss [4].

The grade of FI is an effective factor in determination of the course of treatment and prognosis [5]. Diagnosis of FI is based on clinical examination with a Nabers probe, with the use of two-dimensional radiographs serving as an adjunct. According to a recent systematic review, cone beam computed tomography (CBCT) has high accuracy for furcation involvement detection [6]. However, there is limited evidence to support and justify the use of CBCT for the diagnosis and treatment of teeth with FI at this time [7]. Treatment planning of teeth with FI remains a difficult process for the clinician. This chapter will review and discuss the diverse therapeutic modalities for teeth with FI.

8.2 Resective Therapy

Root resective therapy is a well-known treatment modality for the management of teeth with advanced FI. The main resective procedures utilized to treat FI include root amputation, hemisection, and bicuspidization. Over the years, the use of these techniques has decreased considerably. Some of the possible reasons of this decrease are the reported complications and failure rates and the fact that more predictable therapies such as periodontal regeneration and dental implants are available.

Survival rates of teeth with FI have been published in the literature with heterogenous results. A recent investigation on the retention of molars after root resective therapy over an observational period of 30 years reported a median survival of 20 years and a cumulative survival rate of 90.6% at 10 years that decreased considerably thereafter. The complications that led to tooth extraction included periodontal problems (50%), endodontic problems (26.7%), and caries (16.7%) [8]. If this therapy is selected, it is important to understand that a long-term successful outcome relies on case selection and adequate maintenance, as well as endodontic and restorative treatment [9]. One of the disadvantages of this technique is that after extraction of the root, alveolar bone resorption occurs, leading to a decrease in ridge height and width [10]. This could result in an alveolar ridge deformity and food impaction under the prosthesis and may also compromise the site for future dental implant placement. To decrease the possibility of these complications, guided bone regeneration (GBR) could be used after root extraction to minimize ridge remodeling [9]. Nevertheless, this interesting combination technique (root amputation with GBR) needs to be further studied.

Root resective therapy could be a good treatment option when implant placement is not feasible or needs to be postponed, in cases of severe furcation involvement that cannot be regenerated and in situations that the tooth must be strategically maintained as an abutment of a prosthesis. Another treatment modality for the management of FI is biologic shaping. This technique was introduced as an alternative to traditional crown lengthening and possible use during osseous resective surgery for the treatment of periodontal disease. This procedure removes tooth surface irregularities including concavities, grooves, cementoenamel projections, and FI [11]. In the treatment of FI, class I and II furcation lesions may be decreased or eliminated, and by consequence oral hygiene and maintenance are facilitated. This technique is described in the chapter by Melker et al., in this volume.

8.3 Regenerative Therapy

The scientific literature indicates that regeneration is a more effective surgical approach for treatment of FI in comparison to non-regenerative approaches and is discussed below [12–16].

8.3.1 Guided Tissue Regeneration (GTR) vs. Open Flap Debridement (OFD)

A systematic review and meta-analysis by Murphy and Gunsolley compared GTR to OFD for treatment of intrabony defects and FI. The results of this study revealed that the GTR group had statistically significant higher horizontal defect fill (0.8 mm) and vertical attachment level (VAL) gain (0.86 mm) compared to the OFD group [17]. Another systematic review and meta-analysis by Jepsen et al. evaluated the treatment of FI by regeneration vs. OFD. Fourteen studies were included based on the inclusion criteria. The authors concluded that GTR is a better treatment approach for class II mandibular (mean difference, 1.5 mm) and maxillary molar (mean difference, 1.05 mm) defects [18]. Reynolds et al. assessed bone replacement grafts vs. OFD for treatment of intrabony defects and FI. From this systematic review, they concluded that bone replacement grafts are more effective than non-regenerative treatments such as OFD for FI treatment and intrabony defects [16]. The long-term survival rate associated with GTR has been reported to be as high as 83–100% after 5–12 years, which is better than other treatment modalities such as OFD, tunneling, root amputation, and hemisection [19].

8.3.2 Membrane vs. No Membrane

A systematic review published by Kinaia et al. compared the effectiveness of GTR using a resorbable membrane vs. OFD, non-resorbable membrane vs. OFD, and resorbable membrane vs. non-resorbable membrane for treatment of FI. This study concluded that GTR with resorbable membrane has significantly better vertical clinical attachment level (VCAL) gain in comparison to OFD (mean combined difference, 0.88 mm) and greater reduction in vertical pocket depth (VPD) (mean combined difference, 0.73 mm), greater horizontal bone fill (HBF) (mean combined difference, 0.98 mm), and vertical bone fill (VBF) (mean combined difference, 0.78 mm). For non-resorbable membranes in GTR, better results were reported compared to OFD in terms of VPD reduction (mean combined difference, 0.75 mm), VCAL gain (mean combined difference, 1.41 mm), HBF (mean combined difference, 1.16 mm), and VBF (mean combined difference, 0.58 mm). This study indicated that resorbable membranes were better than non-resorbable membranes in vertical bone fill for the treatment of FI [14].

8.3.3 Combination Therapy: GTR + Bone Graft

A meta-analysis performed by Chen et al. assessed GTR with or without bone grafting for the treatment of class II FI. In mandibular molars, it was shown that VCAL was significantly better using GTR with bone graft compared to OFD (weighted mean difference, 1.53 mm), while GTR with bone graft was a better treatment option than GTR alone (weighted mean difference, 0.47 mm). Regarding maxillary furcations, GTR and bone graft were better than GTR alone (0.86 mm in favor of GTR and bone graft vs. GTR alone). Therefore, this analysis concluded that GTR and bone grafting are the best treatment modality for class II FI [15].

8.3.4 Biologic Agents

Recently more attention has focused on the use of biologic agents such as enamel matrix derivative (EMD), recombinant human platelet-derived growth factor-BB (rhPDGF-BB), and autologous plasma concentrates for regenerative treatment of FI.

8.3.5 Enamel Matrix Derivative (EMD)

In a randomized control trial (RCT) by Casarin et al., the application of EMD was compared to OFD for treatment of FI. It was concluded that EMD therapy promoted a reduction in the number of proximal furcations presenting a diagnosis of class II after 24 months of treatment compared with OFD therapy [20]. A second RCT compared the use of EMD to a membrane. The EMD group showed significantly more improvement in horizontal furcation defect (HFD) than the membrane group [21]. Unfortunately, there are few RCTs on the use of EMD for treatment of FI at this time.

8.3.6 Recombinant Human Platelet-Derived Growth Factor-BB (rhPDGF-BB)

Nevins et al. evaluated effects of rhPDGF-BB on FI treatment in a RCT. They compared rhPDGF-BB with OFD and reported significant CAL gain and PD reduction in the test group compared to baseline (P < 0.001) but demonstrated no significant differences between the test and control groups. In the other hand, Howell et al. reported significant radiographic bone height gain with the use of rhPDGF-BB at 9 months compared to OFD (54% BF vs. 12% BF). The authors concluded that application of rhPDGF-BB is beneficial for treatment of intrabony defects and FI [22–24].

8.3.7 Autologous Plasma Concentrates (PCs)

Autologous PCs have been utilized in periodontal regeneration and treatment of FI alone or in combination with grafting materials with the aim to enhance the healing capacity of soft and hard tissues. The rationale behind the use of PCs is to capitalize on the polypeptide growth factors (PGFs) such as PDGF (platelet-derived growth factor), transforming growth factor-β (TGF-β), and insulin-like growth factor (IGF) contained in the concentrates. These growth factors have an important role in chemotaxis and cell proliferation and differentiation [25]. There is limited evidence regarding the use of PCs alone for the treatment of FI. This section will focus on the use of PC alone due to the confounding factors when utilized in combination with grafting materials and/or membranes.

A randomized clinical trial evaluated the effectiveness of autologous platelet-rich plasma (PRP) in the treatment of mandibular degree II furcation defects compared with OFD using a split-mouth approach. There was a statistically significant difference in all clinical and radiographic parameters at furcation sites treated with PRP as compared to OFD alone. However, there was incomplete closure of the furcation in both groups [26]. Another randomized clinical trial from the same institution evaluated the effectiveness of platelet-rich fibrin (PRF) alone in the treatment of mandibular degree II furcation defects compared with OFD using a split-mouth approach. At 9 months postoperatively, all the clinical and radiographic parameters showed statistically significant improvement at the sites treated with PRF as compared to OFD. An important finding of this study is that 66.7% of FI defects treated with PRF had complete clinical closure [27]. Interestingly, a randomized clinical trial compared the use PRP or PRF alone to OFD in the treatment of mandibular degree II furcation defects. Clinical and radiographic parameters demonstrated statistically significantly improvement for both PCs as compared to OFD. However, there was no statistically significant difference between the PRP and PRF groups [28]. The limited current evidence shows improvement in clinical and radiographic parameters that could be beneficial in the treatment of FI. However, further clinical and histologic studies are needed to confirm the regeneration potential of autologous PCs.

8.3.8 Class II Furcation Involvement

In 2015, Graziani evaluated OFD for the treatment of class II FI by a systematic review of RCT studies. They assessed tooth survival and change in the horizontal clinical attachment level (HCAL), vertical clinical attachment level (VCAL), reduction of pocket probing depth (PPD), recession increase (REC), horizontal bone level (HBL), and vertical bone level (VBL). The weighted mean differences for HCAL were 0.96 mm [CI: (0.60, 1.32), p < 0.001] and 0.55 mm [CI: (0.00, 1.10), p = 0.05] for VCAL gain. PPD reduction over 6 months was 1.38 mm [CI: (0.91, 1.85), p < 0.01]. The authors concluded that the clinical performance of conservative surgery, such as OFD, in the treatment of furcation defects may represent a valid cost-effective treatment solution for class II, particularly mandibular defects, mainly when other therapeutic options are not applicable either for anatomical or patient-related factors [29].

The current systematic review from American Academy of Periodontology (AAP) regeneration workshop assessed the available evidence for effectiveness of different regenerative approaches. Avila-Ortiz et al. selected 150 articles of which 6 were systematic reviews, 109 were clinical trials, 27 were case series, and 8 were case reports. In this review, they examined specific clinical scenarios and revealed that regenerative approaches are predictable treatment options for class II furcation (Fig. 8.2a–d) defects on the buccal, mesial, and distal of maxillary molars and buccal and lingual of mandibular molars. However, regeneration for class III molars is not predictable based on current evidence [12].

According to a consensus report from the AAP Regeneration Workshop and based on available evidence, it was concluded that “(1) Regeneration has been demonstrated histologically and clinically for the treatment of Class II furcation defects (2) Although periodontal regeneration has been demonstrated histologically for the treatment of mandibular Class III defects, the clinical evidence is limited to one case report (3) Evidence supporting regenerative therapy in maxillary Class III furcation defects in molars and premolar furcation defects is limited to clinical case reports, which reported unpredictable outcomes; and (4) In Class I furcation defects, regenerative therapy may be beneficial in certain clinical scenarios, although most Class I furcation defects may be successfully treated with non-regenerative approaches” [30].

8.3.9 Endoscope

The use of an endoscope in periodontology was proposed to overcome the limitations of closed scaling and root planing (SRP). This device was designed to explore and visualize subgingival deposits and serve as an adjunct in SRP thanks to magnification of the root surface (24–28×) and visualization through a monitor [31]. Ultrasonic scalers, curettes, explorers, and probes have been modified for use with the dental endoscope. Due to the difficulties encountered during instrumentation, the use of an endoscope could theoretically serve as a useful adjunctive tool for treatment of molars with FI. Unfortunately, the literature is scarce. A study on multi-rooted teeth showed that the use of an endoscope provided no significant improvement in calculus removal when used as an adjunct to SRP [32]. Even though furcations can be visualized with this device, the ability to instrument this area is difficult due to anatomy and limited access [33]. However, endoscope therapy could be effective around single-rooted teeth, but not as effective for multi-rooted teeth [34, 35]. Further clinical studies reporting on clinical parameters are needed to justify the use of the endoscope in the nonsurgical treatment multi-rooted teeth.

8.3.10 Laser Therapy

The use of lasers in the treatment of periodontal disease has been controversial. According to the 2018 AAP best evidence consensus on the efficacy of laser therapy on the treatment of periodontitis, lasers show similar or slightly improved clinical outcomes when utilized as an adjunct to mechanical therapy. In addition, when utilized as adjunct to periodontal surgery, most of the evidence suggest no additional benefit [36].

In regard to the use of lasers for the treatment of FI, the literature is very limited as the majority of the available literature does not report if laser-treated sites included lesions with FI. In a double-blind RCT, clinical parameters and bacterial reduction of class II furcation lesions treated with conventional SRP only or SRP followed by neodymium:yttrium-aluminum-garnet (Nd:Yag) laser were evaluated. The results demonstrated that Nd:YAG laser significantly reduced the total bacteria colony-forming units (CFU) immediately after irradiation. However, there were no significant differences in bacterial reduction or clinical parameters between both groups at 6 weeks [37]. To date only one human histologic study showed some evidence of furcation regeneration following the use of an Nd:YAG laser (Fig. 8.3a, b) [38]. A few animal studies have assessed the use of lasers for the treatment of FI. A study in dogs investigated the use of a CO₂ laser for the treatment of experimentally induced class III furcation defects. This study showed that the use of laser promoted regeneration was superior to GTR and SRP in terms of attachment gain [39]. Another dog study investigated the effect of an erbium-doped yttrium aluminum garnet (Er:Yag) laser in experimentally induced periodontitis in the furcation as compared to traditional debridement. New bone formation was significantly greater in the laser group. However, both groups showed similar amounts of cementum formation and connective tissue attachment [40]. Lastly, a study of experimentally induced periodontitis in rats showed greater bone formation in the furcation area when an erbium, chromium:yttrium-scandium-gallium-garnet (Er, Cr:YSGG) was utilized for subgingival treatment [41]. In regard to human studies, a split-mouth clinical trial was conducted to assess the clinical efficiency of an Er,Cr:YSGG laser in the treatment of FI classes II and III as compared to manual subgingival debridement at 6 and 12 weeks. This study concluded that the use of an Er,Cr:YSGG laser significantly decreased PD and BOP, as well as the pain score [42]. In summary, further studies are needed to justify the use of lasers in the treatment of FI.

8.3.11 Photodynamic Therapy

Photodynamic therapy (PDT) is a noninvasive therapeutic method that has been utilized in periodontology as an adjunct to mechanical debridement during initial phase, nonsurgical therapy, and maintenance phase. In theory, PDT could serve as an adjunct to the treatment of teeth with FI due to the limited access for instrumentation. This technique consists of light-mediated activation of a photoactivable nontoxic chemical agent, such as toluidine or methylene blue, that is applied into the pocket. The lethal photosensitization of microorganisms causes changes in the bacterial membrane and DNA damage [43]. The main advantage of this technique is that it possesses an antimicrobial effect without the side effects associated with systemic antibiotics and the risk of microbial resistance [44]. According to the current evidence, when PDT is utilized as an adjunct to mechanical therapy, modest improvements in probing depths and clinical attachment levels can be obtained [36]. Unfortunately, there is a limited number of studies regarding the use of PDT in the treatment of FI. A histomorphometric study evaluating the effect of PDT on furcal bone loss in rats with experimentally induced periodontitis showed that the group treated with PDT demonstrated less bone loss as compared to other groups [43]. In contrast, a randomized clinical trial showed that PDT did not provide additional improvements in terms of clinical parameters in the treatment of class II furcation lesions. However, PDT demonstrated a reduction in periodontopathogens and pro-inflammatory cytokines [45]. Further clinical studies with longer follow-up periods are necessary to justify the use of this therapy for the treatment of FI.

8.3.12 Local Antimicrobials

The use of local antimicrobials as an adjunct to subgingival debridement in deep and recurrent pockets has demonstrated improvements in clinical parameters (PD reduction and CAL gain) [46]. However, there is no evidence to support the use of local antimicrobials in furcation lesions during initial or supportive periodontal therapy (SPT). Human studies have found that the use of tetracycline fibers in conjunction with SRP in class II mandibular furcations during SPT did not show CAL gain [47]. Further, the use of locally delivered doxycycline did not enhance any improvement in furcation lesions [48] or reduced the frequency of reinstrumentation up to 12 months at furcation sites [49]. Subgingival ultrasonic instrumentation irrigated with essential oils (EO) or chlorhexidine does not improve clinical parameters, with the exception of BOP, which was reduced by the use of EO [50]. Similarly, the use of topically applied polyvinylpyrrolidone and iodine (PVP-I) during initial therapy in class II furcation lesions did not provide any clinical benefit [51].

8.3.13 Systemic Antimicrobials

The adjunctive effect of systemic antimicrobials on the treatment of periodontitis has been widely studied. Meta-analyses have demonstrated that there is additional PPD reduction and CAL gain when systemic antibiotics are used in conjunction with mechanical therapy [52, 53]. It could be assumed that this combination therapy could have a beneficial effect on teeth with FI. To the best of our knowledge, the adjunctive effect of systemic antibiotics at furcation sites has been addressed in only one study that evaluated the clinical effect of amoxicillin and metronidazole as an adjunct to mechanical debridement. In spite of the fact that there was a significant attachment gain and decrease in PPD and BOP, the change of furcation degrees was small. Therefore, the use of systemic antimicrobials did not show a clinically relevant benefit in the treatment of FI [54].

8.3.14 Statins

Statins are mainly utilized as lipid-lowering drugs to prevent cardiovascular disease. In addition, these drugs also possess properties relevant to the treatment of periodontitis [55]. Statins are anti-inflammatory [56], antimicrobial [57], and antioxidative [58], and they also have anabolic and anti-resorptive effects in the bone [59–61]. Due to the aforementioned effects, these drugs have been used as an adjunct to nonsurgical and surgical periodontal therapy for the treatment of periodontitis and intrabony defects. Systematic reviews and meta-analyses have found significant additional clinical and radiographic improvements when locally delivered [55, 62]. However, there is a paucity of data in regard to the use of statins for the treatment of FI. A recent RCT evaluated the effect of rosuvastatin (RSV) gel combined with autologous PRF and hydroxyapatite (HA) bone graft in the surgical treatment of mandibular class II furcation defects as compared to OFD + placebo gel and OFD + PRF + HA. There were statistically significant differences among the groups; the use of 1.2 mg in situ gel with PRF and HA bone graft showed greater PD reduction, horizontal and vertical CAL gain, IBD reduction, and bone defect fill [63]. Another RCT investigated the efficacy of 1.2% RSV and 1.2% ATV gel as an adjunct to SRP for the treatment of class II furcation defects. Both statin gels were applied at the time of SRP and at a 6-month recall appointment. The RSV group showed significant improvement in PD reduction, vertical and horizontal CAL gain, and defect depth reduction as compared to the ATV group [64]. The use of RSV appears to be promising in the treatment of FI. However, further studies are required.

8.3.15 Prognosis

Several studies have assessed the risk factors associated with the longevity of multi-rooted teeth. In these studies, particular attention was given to the degree of FI in relation to the risk of molar loss. A retrospective study of multi-rooted teeth in patients that received active and SPT found that class I FI was not associated with tooth loss when compared to teeth with no FI. However, FI class II (Fig. 8.4), FI class III (Fig. 8.5), smoking, and lack of compliance represented risk factors for molar tooth loss, especially in combination [65]. It is important to point out that this group of patients was treated with a variety of therapeutic approaches including OFD, periodontal regeneration, tunneling, and root resection. Another retrospective study evaluated the long-term prognosis factors for the loss of molars with different degrees of FI during SPT. In contrast to the previous study, this group was treated with conservative non-regenerative treatment. FI, bone loss, mobility, pocket depth, and age were strong predictors of tooth loss. Molars with FI class III and advanced bone loss presented a worst prognosis. However, long-term retention of periodontally compromised molars was achieved [66].

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