Twelve patients were selected for this study, suffering from cystic lesions in the mandible or maxilla and were free from any systemic disease. The patients were divided into two groups:- Group A:- involved six patients in which the cystic lesions were enucleated and the bony cavities were obliterated with Bio-Gen® putty graft material. Group B :- involved six patients in which after enucleation of the cystic lesions the bony cavities were left to be filled with the normal blood clot and used as a control group. The cases were followed up both clinically and radiographically using periapical radiographs films by paralling technique with aluminum step wedge after 2weeks,4weeks, 6weeks,8 weeks postoperatively for wound and bone healing . Bio-Gen® putty are chemically treated xenogenic equine bone substitute in which the organic part was treated by series of enzymatic reactions (deantigenation). Bio-Gen®putty was used in six cases in this study(consisting the study group) to fill their cystic osseous cavities postoeratively. Increase in relative bone density was detected by indirect digital radiograph and this was statistically significant. On the other hand, in the control group, there was a limited increase in relative bone density at follow-up intervals and this was statically insignificant.