Generalizability of the added benefits of guided tissue regeneration in the treatment of deep intrabony defects. Evaluation in a multi-center randomized controlled clinical trial

Background: Several studies have shown that GTR therapy of intrabony defect s results in significantly better outcomes than access flap alone. Most of the available data, however, have been produced in highly controlled resear ch environments by a small group of investigators. Generalizability of resu lts to different clinicians and different subject populations has not been evaluated so far. Methods: This parallel group study involved 143 patients recruited in a pra ctice-based research network of 11 offices in 7 countries. It was designed to evaluate: 1) the applicability of the documented added benefits of GTR i n the treatment of intrabony defects to different populations, and 2) the g eneralizability of the expected results to different clinicians. GTR was co mpared to access flap alone. Defects, one in each patient, were accessed wi th a previously described papilla preservation flap in both the test and co ntrol group. In addition, GTR sites received application of a bioabsorbable poly-D,L-lactide-co-glycolide membrane. A stringent plaque control regimen was enforced in all patients during the 1-year observation period. Outcome s included gains in clinical attachment (CAL) and reductions in probing dep th. Results: Observed gains in CAL were 2.18 +/- 1.46 mm for access flap and 3. 04 +/- 1.64 mm for the GTR-treated group. The treatment-associated differen ce was statistically significant (P = 0.03) after correcting for both cente r effect and defect anatomy. Among the various centers, a 1.73 mm differenc e in CAL gain was observed. This is a clinically relevant amount, which und erlines the significance of center variability in the outcome of periodonta l surgical procedures. A frequency distribution analysis of the obtained CA L gains indicated that GTR treatment of deep intrabony defects decreased, w ith respect to the access flap control, the probability of obtaining only a modest attachment gain at 1 year. Conversely, CAL gains of 4 mm or more we re observed in more than 40% of GTR-treated defects and in less than 20% of the controls (P < 0.0001). Conclusions: These data indicate that GTR therapy of deep intrabony defects performed by different clinicians on various patient populations resulted in both greater amounts and improved predictability of CAL gains than acces s flap alone.