Reconstruction of Deficient Atrophic Ridges Using Guide Bone Regeneration Technique

patients will be informed of the nature of the research work and informed consent will be obtained then randomized in 2 groups. Mixture 1:1 autogenous and xenogenic bone covered with Polytetrafluoroethylene membrane control group and study group p covered with native collagen membrane. * Patients of both groups will be subjected to CBCT (diagnostic for upper arch), diagnostic wax-up and stent fabrication. * Intra operative procedures (for both groups) followed by CBCT will be taken for every patient after 4 months. Both the study and control group will receive: * In Recipient site, using 15C blade on Bard Parker handle incision of full thickness mucoperiosteal flap inorder to obtain, three-line pyramidal flap, reflection using mucoperiosteal elevator molt 9. * The defective site is reevaluated after its primary evaluation on CBCT using UNC (University of North Carolina) periodontal pr