This study was designed to examine the aging effect on bone formation induced by recombinant human BMP-2 (rhBMP-2) combined with polylactate-polyglycolate-copolymer/gelatine sponge complexes ( PGS) at palatal subperiosteal sites (N=72) in 36 Wister strain male rats, at 10 weeks, 30 weeks and 70 weeks of age. The rats at each age were divided into three groups: no implant (CN) , PGS implant alone