Meloni SM, et al. - Since Cawood-Howell class IV atrophies, also known as “knife-edge” ridges, are a serious horizontal defect, challenging the placement of regular implants, researchers clinically and radiographically assessed bone regeneration of severe horizontal bone defects with 3 years of follow-up. Resorbable collagen membranes and a 1:1 mixture of anorganic bovine bone (ABB) and autogenous bone have been treated in patients with a horizontal bone width of 4 mm or less in the posterior mandible or maxilla. There have been no implant and prosthetic failures and no complications. Data reported that the mean marginal bone level was 1.15 ± 0.28 mm after 3 years. The plaque index was 11.6%, and bleeding on probing was 5.2%. Within the limitations of this study, the use of collagen resorbable membranes with a 1:1 mixture of particulate ABB and autogenous bone for the reconstruction of Cawood-Howell class IV alveolar ridge atrophies appears to validate high implant survival rate and high average bone augmentation.