Abstract : This randomized clinical trial evaluated the histological and radiographical characteristics of bone regeneration after horizontal alveolar ridge augmentation using two different surgical approaches. The study randomized 20 patients into two groups: split-bone block group and cortico-cancellous bone block group. The grafts were obtained from the mandibular symphysis in both groups. Radiographic bone density of the augmented sites was measured by CBCT scans at baseline and 6 months post-operatively. A bone biopsy was taken at 6 months post-operatively before implant placement. Histological evaluation showed significant differences in bone tissue percentage between the groups. The split-bone block group had a higher mean percentage (61.80%) than the cortico-cancellous block graft group (46.90%). Radiographic bone density at 6 months post-operatively also differed significantly between the groups, with the split-bone block group showing a higher mean density (P = 0.000). Within the limitations of our study, we found that the split-bone block graft yielded superior bone regeneration quality than the cortico-cancellous block graft.