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Background and aimPost-extraction resorption of the buccal wall of the alveolar ridge with minimal loss in ridge height results in knife-edged residual ridges that require hard tissue augmentation procedures. One possible treatment option for these defects is promoting the horizontal expansion of the crest using the ridge splitting technique introduced by Simion et al. in 1992, which presents the advantage of simultaneous implant placement and avoiding bone graft harvesting from secondary donor sites.This study aims at the comparison of the three-dimensional radiographic outcomes of ridges expanded using the splitting technique with two different flap approaches, either creating access with a mucosal flap with preservation of the periosteum attached to the buccal plate or performing a mucoperiosteal flap with denudation of the buccal bone.Materials and methodsPartially and fully edentulous patients with adequate height but an insufficient width (3 mm or less) underwent surgery for horizontal expansion of the maxillary crest and simultaneous implant placement or healing with horizontal spreaders. In group 1 a beveled incision was positioned palatal to the crest and a partial-thickness flap was dissected and reflected from the palate to the buccal of the alveolar ridge. The periosteum was preserved and not dissected to secure blood supply to the cortical bone. One horizontal (mid-crestal) and two vertical osteotomies were made with a piezoeletric unit to separate labial and palatal cortical bone plates. Then, the mobilized buccal bone plate was displaced in the buccal direction using horizontal spreaders and the expanded gap filled with a xenograft. In group 2 the crestal incision was followed by preparation of a mucoperiosteal full-thickness flap with complete denudation of the buccal bone. Ridge expansion procedures were similar to those described previously. In this case, guided bone regeneration consisted not only in filling of the expanded gap between cortical plates but also of lateral augmentation over the buccal bone plate with xenograft granules and a xenogeneic collagen barrier membrane. Radiographic follow-up of the patients was made by CBCT prior to surgery, 1 and 2 years post-operatory.ResultsWe present the results of 6 patients homogeneously distributed by the two groups. After a minimum 2 years of follow-up, no implants were lost and all prosthesis successfully loaded. The expansion technique allowed for the correction of the buccal concavity caused by horizontal ridge resorption, minimizing the morbidity related with second donor site and optimizing the prosthetic position of the restoration. Radiographically there is evidence of hard tissue stability in both approaches. The full thickness flap approach (group 2) presents higher bone volume gain.Conclusions and clinical relevanceClinically, the ridge splitting technique produces radiographically stable and predictable results, regardless of the flap approach. Performing the full thickness flap with lateral augmentation leads to higher buccal volume.