This study was conducted to clinically and radiographically evaluate the effect of retaining mandibular overdenture, by retention silicon material, on the bone level of the abutment teeth. The patients were randomly divided into two groups A and B. All patients were treated by upper conventional complete dentures opposed by tooth supported lower complete overdentures. In group A, the overdenture abutment teeth were covered by post and copping carrying an attachment. Retention Silicon act as housing by relining the denture base in the area of the attachment. In group B, the overdenture abutment teeth were covered by post and copping only with no attachment mechanism. Radiographic evaluation was carried out by measuring the amount of change in alveolar bone height around the abutment teeth. The results of the study showed a significant alveolar bone loss around the abutment teeth in both groups. The group with attachment showed more alveolar bone loss. The amount of bone resorption was nearly 3 times more in the attachment group than the group without attachment by the end of the 6 months follow up period