A new therapeutic system using purified recombinant human platelet-derived growth factor-BB (rhPDGF-BB) in combination with a biocompatible, osteoconductive, synthetic scaffold beta-tricalcium phosphate (ß-TCP) has recently been shown in a large-scale, prospective, blinded, randomized clinical trial to safely and effectively treat advanced periodontal osseous defects. A significant gain in clinical attachment level was observed 3 months postsurgery for sites treated with 0.3 mg/mL rhPDGF-BB + ß-TCP versus ß- TCP + buffer (active control), with this trend continuing at 6 months postsurgery. Additionally, sites treated with 0.3 mg/mL rhPDGF-BB + ß-TCP also had significantly greater radiographic linear bone gain and percent defect fill at 6 months postsurgery than sites that received bone substitute with buffer. Representative cases from the clinical trial were followed to assess their ability to maintain the initial effect of treatment observed at 6 months. At 18 or 24 months postsurgery, with the same clinical and radiographic measurement techniques used as were performed at the 6-month time point for the clinical trial, these cases demonstrated maintenance of the clinical attachment level for all but one case, with all cases demonstrating substantial increases in linear bone gain and percent bone fill versus measurements obtained at 6 months postsurgery. Substantial radiographic changes in the appearance of the defect fill were observed for both rhPDGF-BB treatment groups, consisting of increased radiopacity and bone trabeculation, indicative of increased mineralization and maturation of the bone observed 6 months postsurgery.