Assessment of GBR in Augmentation of Horizontally Atrophic Maxillary Ridge Using Collagen Membrane Versus Using Titanium Mesh

patients with atrophic maxillary ridge \< 4 mm will be selected in this study for augmentation for future implant placement. The full thickness flap will be elevated including one extra tooth on each side of the edentulous area or if completely edentulous 5 mm on each side.. the bone bed will be prepared by cleaning any debris and Multiple decortication holes will be performed with a 2.0 mm round bur. the harvested bone from the chin is then mixed with the xenograft with ratio 1:1 and then put on the recipient site and will be covered with a collagen membrane with the Sausage technique (intervention group) and the other group the graft will be covered with titanium mesh (control group). flap is repositioned and sutured. followup for 6 months and then CBCT is done. Reopening after 6 months, core biopsy is taken by a 2 mm thickness trephine from the healed augmented bone at the site of implant placement and will be sent for histomorphometric analysis and the bone thickness (buccolingual ) dimension is measured using a caliper and from the CBCT (cone beam CT) the bone width gain will be calculates and recorded. postoperative complications( infection, wound dehiscence or membrane exposure) will be monitored and recorded.