The clinical case involved a patient with significant horizontal volumetric contraction of the edentulous ridge in area 4.6 following dental element avulsion due to extensive periapical injury. Analysis of the initial clinical situation was performed by three-dimensional radiographic investigation using mandibular Cone Beam CT (CBCT). Both CBCT sections and three-dimensional volumetric reconstruction showed the major bony defect at tooth element 4.6. The surgery began with making primary incisions in area 4.6 to expose the horizontal bone defect, followed by grafting the site with collagen-preserved bone graft of equine origin cortical-cancellous mix granules. The Flex Cortical Sheet was then properly placed at the graft site, curved to cover the area and stabilized by pins and fixation screws, followed by pericardial membrane.