A review of the literature was performed related to the frequency of closure of Grade II furcations with various regenerative therapies such as bone replacement grafts (BRG), coronally positioned flaps (CPF), guided tissue regeneration barriers (GTR), or open flap debridement (OFD). Fifty papers involving 1,016 furcations were evaluated. Complete furcation closure was reported only 20% of the time. Clinical change from Grade II to Grade I (partial furcation fill) was found in an additional 33% of the cases. Therefore, general improvement in clinical furcation status has been reported only about 50% of the time. The most effective furcation regenerative therapy was the combination of GTR plus BRG (91% overall positive). Similar overall positive results (88%) were achieved with nondemineralized allogeneic freeze-dried bone plus tetracycline without a barrier. The least effective therapy for regeneration in furcations was OFD (2% complete furcation closures and 13% partial furcation closures). If complete furcation closure is a primary goal of regenerative therapy, that goal would not appear to be commonly met.
Key words: furcations, regeneration, periodontal therapy
Management of moderate-advanced furcation invasions presents one of the major challenges in periodontal treatment.1-4 Teethwith furcation involvements undergo more extensive and rapid clinical probing attachment loss and are lost with greater frequency than are single-rooted teeth.2, 5, 6, 7, 8, 9 Grade I furcations are generally well managed with routine periodontal procedures, while Grade m furcations generally require more extensive therapy such as tunneling, root amputation or hemisection, or extraction. Grade II furcations present a common clinical problem that has perplexed clinicians for many years.
Several techniques have been proposed and promoted to treat and improve the prognosis of Grade II furcation-involved molars. Guided tissue regeneration (GTR) has recently excited the dental profession based on early reports of substantial attachment gain and bone fill in furcations. However, the primary ideal goal of furcation therapy is to retain the tooth intact and to completely close the furcation, thereby returning the local condition to one of anatomic normalcy, facilitating long-term supportive periodontal therapy, and improving the likelihood of tooth retention.
The purpose of this review article was to evaluate the literature and determine the frequency with which various regenerative therapies have been reported to achieve clinical closure of Grade II furcations.
Both a Medline and personal search of the literature revealed a multitude of papers related to regenerative furcation therapy in humans, from individual case reports to controlled clinical trials. The types of therapy evaluated were generally grouped into bone replacement grafts (BRG), coronally or laterally positioned flaps (CPF/LPF), guided tissue regeneration barriers (GTR), or open flap debridement (OFD) with appropriate subgroups. As long as data were presented that addressed evaluation of the clinical changes in Grade II furcations as a result of such regenerative therapy, a report was included in this review. Some papers that are often referenced or that maybe considered classics, but that did not address that concept of furcation closure, are included in the listing for completeness.13, 18, 23, 28, 32, 35, 41, 42, 45, 49, 53 Furcation closure for this analysis was graded as complete (no residual, clinical, probeable furcation or up to a 1 mm "dimple") or > 50% (partial furcation fill or change from Grade II to Grade I furcation involvement).Treatment of furcation Grades I and III was not analyzed.
Fifty papers involving 1,016 cases were evaluated. The data from the studies were combined for mete analysis and evaluated with the Statistical Analysis system analysis and graphics programs. The techniques used to analyze the data for the selected studies were as follows: (1) weighted means were computed for each group defined by the treatment category, considering the sample size for each study; (2) overall means were computed for complete fill cases, partial fill cases, and overall clinical furcation improvement (improvement of at least one furcation grade); and (3) standard errors were computed for the weighted means, and these were used to calculate 95% confidence intervals for each treatment group and for each condition (complete fill, overall clinical improvement).
The results of the analysis of the literature related to clinical closure of human Grade II furcations as a result of regenerative therapy are presented in Tables 1 and 2. In Table 1 the findings are listed chronologically and by type of therapy. Often comparative data were presented within a report, or combinations of treatments were performed.
It can be seen from Table 1 that the frequency of complete furcation closure varies from 0% to 100% for individual reports within each major treatment group. Overall, complete furcation closure was reported in approximately 20% of the cases, while a change to Grade I (partial furcation fill) was reported in about 33 % of the cases. Table 2 summarizes the studies according to general treatment method and ranks them by percentage of overall clinical improvement. The most effective furcation regenerative therapy reported was the combination of GTR (with GTPM) plus BRG (91% overall positive).Very similar overall positive results (88%) were achieved with nondemineralized FDBA plus tetracycline without a barrier. Other treatments with > 75% overall improvement were three other BRG groups. The least effective therapy for regeneration in furcations was OFD (2% complete furcation closures and 13% partial furcation closures).
Graphs of mete analysis results are shown in Figures A and B. The vertical dotted line represents the overall mean for all cases based on the clinical outcome criteria evaluated. The means for the treatment categories have been plotted along with 95% confidence intervals. The sample size for each group is also indicated. If there was only one study in a treatment category, there are no confidence intervals. The relative position of the means right or left of the dotted line representing the overall success percentage allows for comparison of more versus less successful treatments. Treatments whose confidence intervals overlap are not significantly different. Except for those categories that included only one study and have no confidence interval, all of the groups have overlapping confidence intervals and are not significantly different from each other.
Despite the initial excitement of periodontists related to the reports of Pontoriero et al.25 with GTR barriers alone and Schallhorn and McClain26 with GTR barriers in combination with BRGs, their degree of success in achieving furcation closure has not been consistently achieved by others. One might question whether some few millimeters of "fill" or either "open" or "closed" clinical attachment gain that does not substantially change the character, anatomy, or maintainability of a furcation is worth the extra time, expense, and on occasion, morbidity, associated with regenerative techniques.
A review of Tables 1 and 2 and Figures A and B suggests that all of the regenerative techniques reported in the literature yield essentially equal (albeit modest) results. It must be acknowledged, however, that there are many factors that may influence the results of regenerative therapy in furcations. The reports reviewed did not always specify such factors as relative height of the proximal bone, separation of the involved roots, length of the root trunk, mobility, zone of keratinized gingiva, level of plaque control, intensity of follow-up care, etc.60 Complicating the analysis of the reports presented in this review was that in many studies, with results reported in mean millimeters of vertical or horizontal fill, it was impossible to determine whether this amount of fill caused any significant clinical change in the individual furcation status. This is apparent by the many question marks found in Table 1. In several cases, clinical change in furcation status could be determined only from the discussion section of the manuscripts, and in one study, while the discussion reported that "four sites were completely closed," it was not possible to determine whether these were experimental or control sites.33
Comparisons among these reports also were complicated by the different methods of posttreatment evaluation and by what is considered complete fill. We gave the investigators the benefit of the doubt in many cases in which they reported complete fill, but the data or illustrations suggested otherwise. While in most reports complete fill meant that no residual detectable furcation involvement was present, others accepted the presence of a 1 mm "dimple" as complete fill (Table 1). For this reason, we elected to include as complete fill any furcation with < 1 mm of horizontal probing depth.
As seen in Table 2, treatment with GTPM barriers alone results in complete furcation fill only about 25% of the time, and > 50% fill (or improvement of one furcation grade) approximately 37% of the time. About one-third of all the Grade II furcations reported as achieving "complete fill" with GTPM alone were from the Pontoriero et al. study.25 If the results of this one study are excluded, the success rate for GTPM alone in achieving complete furcation closure drops to 19%. While GTPM use has become the "gold standard" for GTR therapy and fill of furcations, many other approaches have shown similar positive results. Use of other types of barriers yields comparative complete (25% GTPM vs. 15% others) and partial (37% GTPM vs. 36% others) furcation fill.
The most effective furcation regenerative therapy reported to date is the combination of a GTR barrier plus BRG (91% overall positive). So far, only the GTPM barrier has been used in this manner, but other barrier materials may well yield similar results when used in this combination. Very similar overall positive results (88%) were achieved with nondemineralized allogeneic freeze-dried bone plus tetracycline without a barrier in localized juvenile periodotitis cases. BRGs as a group achieve similar results as did GTR barriers as a group (21% complete, 35% partial, and 55% overall improvement with BRGs vs. 20% complete, 36% partial, and 56% overall improvement with GTR barriers). By far the least effective therapy for regeneration in furcations is OFD. Complete furcation closure was rarely reported (2%) with this technique, and even partial furcation closures were infrequent (13%).
The reports were treated with methodology for mete analysis. This process addresses some concerns, such as giving equal weight to case reports and controlled clinical studies, and other case selection variables. There is an assumption in combining studies for mete analysis that all experimental interventions are equal. While this is a problem, it is thought that the technique offers more advantages than the traditional reviews. The criteria for judging studies are not always consistent, and eliminating "bad" studies may bias the results. Therefore, the best approach is presumably to include all the studies in the analysis. This is less of a problem than eliminating certain studies.61
The findings of this review suggest that much more research is needed in several areas to improve the consistency and predictability of achieving furcation closure. Among the variables to be investigated are root surface management, internal furcation anatomy, progenitor cell manipulation, bioactive molecules, epithelial exclusion, reinfection, and regenerative biomaterials.
In conclusion, if the goal of periodontal therapy is to effect some positive change in Grade II furcations, this usually can be accomplished to a limited degree. However, if the goal is more ideal and aimed at complete furcation closure, this clinical endpoint does not appear to be accomplished on a regular basis. More research aimed at identifying significant variables and facilitating complete regeneration in Grade II furcations is needed.