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.
The use of collagen membrane barriers in conjunction with combined demineralized bone-collagen gel implants in human infrabony defects.
The present study evaluated the clinical efficacy of a combined graft of autolysed antigen-extracted allogeneic (AAA) bone and microfibrillar collagen (Zyderm) covered with a resorbable collagen membrane in human infrabony defects. The results were compared at 1 year with debrided controls, AAA bone grafts alone, combined AAA bone-collagen grafts (without membrane), and debrided defects covered only with collagen membranes. Ten adult patients having moderate periodontitis and one or more radiographically detectable angular defects probing 6 mm to 7 mm in each quadrant were included. Preoperative measurements of clinical attachment, probing depth, and recession were taken and compared at 1 year following surgery. Measurements at the time of surgery and at 1 year re-entry evaluated osseous defect fill and crestal changes. Each patient received the 5 treatment modalities. Treatment results per patient were used for a series of 2-way analyses of variance. When a significant difference was found, a Student-Newman-Keuls multiple range test was used to determine which treatments were statistically different (0.05 probability level) from each other. All treatment modalities showed improvement over the debrided controls. Similar advantages to using bone-collagen grafts with and without membranes were found in reducing probing depths and gaining new attachment. Significant differences were found when comparing the multifaceted bone graft collagen-membrane technique to all others in achieving superior defect fill. Ninety three percent of all defects treated resulted in 50% or greater fill.