Methods: In 24 patients with advanced periodontitis 39 intrabony defects were treated by the guided tissue regeneration technique using expanded polytetrafluoroethylene (n = 6) or bioabsorbable barriers (n = 32). Clinical parameters were assessed and 39 triplets of standardized radiographs were taken before, 6, and 24 months after surgery. Using a computer-assisted analysis the depth, width, and angle of the bony defects were measured.Results: Statisti-cally significant vertical attachment gains (CAL-V: 3.16 ± 1.63 mm / 3.29 ± 1.64 mm; P = 3 mm) intrabony defects bony fill was more pronounced than in wide and shallow defects (P Schlagwörter: Knochentaschen, GTR, Defektwinkel, Defektweite