Background: Cawood-Howell class IV atrophies, also known as "knife-edge" ridges, represent a serious horizontal defect, making the placement of regular implants challenging.Aim: To clinically and radiographically evaluate bone regeneration of severe horizontal bone defects with 3 years of follow-up.Materials and Methods: This study was designed as a single cohort, prospective clinical trial. Patients having horizontal bone width of 4 mm or less in the posterior mandible or maxilla were treated with resorbable collagen membranes and a 1:1 mixture of anorganic bovine bone (ABB) and autogenous bone. Implants were inserted and loaded 7 months later. Outcomes were implant and prosthetic survival rates, any biological and prosthetic complications, horizontal and volumetric bone dimensional changes measured on cone beam computer tomography (CBCT), peri-implant marginal bone level (MBL) changes measured on periapical radiographs, plaque index (PI), and bleeding on probing (BOP). Results: Eighteen patients received 55 implants. No patient dropped-out. No implant and prosthetic failures and no complications were recorded. Super imposition of pre and 7-month postoperative CBCT scans revealed an average horizontal bone gain of 5.03 ± 2.15 mm (95% CI: 4.13-5.92 mm). After 3 years, mean MBL was 1.15 ± 0.28 mm (95% CI 0.84-1.22 mm). The PI was 11.6%, and BOP was 5.2%. Conclusion: Within the limitations of the present study, high implant survival rate and high average bone augmentation seem to validate 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. K E Y W O R D S bone reconstruction, collagen membranes, GBR, horizontal GBR implant threads. All readable radiographs were displayed in an image analysis program (DFW2.8 for windows, Soredex) on a 24-in. LCD screen (iMac, Apple, Cupertino, California) and evaluated under standardized conditions (SO 12646:2004). The software has been calibrated for all single images using the known distance of two adjacent threads. Measurements of the mesial and distal bone crest level adjacent to each implant were made to the nearest 0.01 mm and averaged at patient level.
| Periodontal parametersPlaque index (PI), defined as plaque absent or present (0/1), and bleeding on probing (BoP), defined as absent or present bleeding on probing (0/1), were recorded 1 year after final prosthesis delivery and 3 years after final loading.Complications were evaluated and treated by the same clinician that performed the augmentation and implant placement procedure.Volumetric dimensional changes, as well as the peri-implant marginal bone level changes were evaluated by an expert radiologist not previously involved in the study. Another clinician (G.F.) not previously involved in the study, made all the others outcomes.