Alveolar ridge augmentation procedures allow restoring jaw defects due to teeth extractions, periodontal diseases, trauma, or outcomes from a previous surgery. This case report describes a patient suffering from Fibrous Dysplasia of the right upper maxilla surgically reconstructed by fibula free flap. In 2003, four dental implants were placed in the 1.2, 1.3, 1.5, and 1.6 areas. Twelve years later, the onset of peri-implantitis led to the failure of osseointegration with consequent thinning of the fibula flap. To avoid the risk of fracture and to restore the bone volumes necessary for a new implant-prosthetic rehabilitation, we used heterologous biomaterials in combination with a non-reabsorbable membrane, according to the Guided Bone Regeneration (GBR) technique. GBR was performed using the Equimatrix® natural bone mineral matrix, Cytoplast™ Ti-150, a non-reabsorbable titanium-reinforced membrane, and four fastening screws to pin the membrane. After six months, the membrane was removed and two Zimmer® implants 3.7 × 13 mm were placed in the 1.1 and 1.2 areas. A fixed implant-supported prosthesis with a custom-milled titanium bar screwed to the implants was made. Computed tomography (CT) six months after GBR showed a good bone regeneration of 1.5 cm mesiodistal (MD), 1.8 cm buccopalatal (BP), and 2.8 cm in height. The main difficulty of this clinical case concerns the low predictability of success of GBR on a maxillary reconstructed area with a free fibula flap: there is no previous evidence in the literature. Clinical and radiographic exams nowadays show that there is no macroscopic bone reabsorption; however, further research is needed to obtain more information.