The study's aim was to assess long-term bone healing associated with two different xenografts in an experimental model of parietal bone defects in rats. We surgically created two symmetrical, full-thickness, parietal bone defects 5 mm in diameter in each of 12 rats, which were then divided randomly into three groups (eight defects per group): group 1, defects filled were with Gen Os; group 2, defects were filled with Gel 40; and group 3 (control) defects were left empty. There was substantial bone formation in group 1, but no to minimal bone formation was seen in the other groups. Significant differences were observed between groups 1 and 2 and groups 1 and 3 (p < 0.05 for both). Gen Os and Gel 40 were both osteoconductive and biocompatible. Based on the long-term outcomes in our study, Gen-Os xenograft is more conducive to bone regeneration, but further studies are required.