GTR has a greater effect on probing measures of periodontal treatment than open flap debridement, including improved attachment gain, reduced pocket depth, less increase in gingival recession and more gain in hard tissue probing at re-entry surgery. However there is marked variability between studies and the clinical relevance of these changes is unknown. As a result, it is difficult to draw general conclusions about the clinical benefit of GTR. Whilst there is evidence that GTR can demonstrate a significant improvement over conventional open flap surgery, the factors affecting outcomes are unclear from the literature and these might include study conduct issues such as bias. Therefore, patients and health professionals need to consider the predictability of the technique compared with other methods of treatment before making final decisions on use. Since trial reports were often incomplete, we recommend that future trials should follow the CONSORT statement both in their conduct and reporting. 
There is therefore little value in future research repeating simple, small efficacy studies. The priority should be to identify factors associated with improved outcomes as well as investigating outcomes relevant to patients. Types of research might include large observational studies to generate hypotheses for testing in clinical trials, qualitative studies on patient-centred outcomes and trials exploring innovative analytic methods such as multilevel modelling. Open flap surgery should remain the control comparison in these studies.
Treatment of interproximal angular defects by guided tissue regeneration: 1 year follow-up.
The periodontal regeneration of interproximal bone defects of the posterior teeth produced by guided tissue regeneration (GTR), with expanded Polytetrafluoroethylene barrier membranes and conventional therapy, was clinically evaluated in 20 intrabony periodontal defects in 10 patients. The material included the presence of at least two proximal angular lesions for the same patient, probing pocket depth > or = 6 mm, bone defect depth > or = 3 mm, and 2-wall defects with crestal involvement relative to the tooth circumference ranging from 90 to 270 degrees. Healing was clinically evaluated by surgical re-entry of GTR-treated sites (10 sites) and debridement only sites (10 sites) 1 year after initial surgery following a strict plaque control regimen. A significant correlation was observed between probing depth reduction, attachment gain and defect depth (test sites); there was increased bone fill in GTR-treated lesions of 2.95 +/- 1.3 mm corresponding to a 69.4% improvement compared to control sites, and 1.3 +/- 1.0 mm corresponding to a 32% improvement (P < 0.0039). The results demonstrated that bone regeneration is highly reliable, as compared to conventional therapy, in cases of severe periodontal bone loss from posterior teeth provided that the principles of GTR are applied.