After tooth extraction of a premolar or molar in mandibular flapless technique, guided bone regeneration is carried out. The cell is filled by a slow absorption material (Xenograft common use). The regeneration space is maintained by a resorbable membrane. To protect the membrane without tissue motion (technical flapless) placing a three-dimensional collagen matrix graft substitute gingival (Muccograft®) will be used. A CBCT preoperative be performed to verify the integrity of cortical and measure the height and width of the residual cavity. caliper measurements at the foot will also be performed during surgery in order to integrate also the thickness of the bone tables and gingival thickness.