Horizontal augmentation of deficient alveolar ridges: advances in guided bone regeneration

The periosteum is highly vascularized, no-elastic collagen-rich connective tissue containing osteoblasts and stem cells. In the double-flap incision for GBR, separating mucosa from periosteum increases flap elasticity, and the periosteal pocket adds an internal layer that stabilizes the membrane and limits apical graft migration.

Guided bone regeneration (GBR) has become a gold standard in bone regeneration for localized ridge augmentation either prior to or in conjunction with implant placement. It is a well-documented technique in the literature that ensures repeatable and clinically predictable outcomes. The GBR procedure involves the use of a space-maintaining scaffold in the form of a bone graft and blood clot, protected by a cell occlusive membrane. The primary role of the membrane is to exclude soft tissue and stabilize the regenerative site. Bone regeneration is facilitated through initial blood clot formation and immobilization of the graft during the healing process. Stabilization of the graft–membrane complex and appropriate soft tissue management are critical to ensuring predictable new bone formation. The double-flap incision (DFI) design was developed as an alternative to periosteal releasing incision (PRI) for flap advancement. The key step is to separate the mucosal tissue from the periosteal layer (approximately 0.3 mm thick), leaving the periosteum attached to the underlying bone. However, isolation of the periosteum from the mucosa increase the flap elasticity while maintaining the supraperiosteal blood vessels which enables to easily accomplishing primary wound closure without stretching the flap and jeopardizing blood supply of the flap at the margins. This, in turn, reduces the risk of complications with post-operative healing. Moreover, the creation of a periosteal pocket contributes an internal periosteal layer, which enhances membrane stability and restricts apical  migration of the graft material. Lateral migration of the graft is further prevented by the periosteal sutures, which provide double suture limbs on either side of the lateral aspect of the membrane, thereby enhancing graft stability. These sutures also reduce marginal flap tension, similar to the suspended external–internal sutures described by De Stavola et al. The main limitation of this approach is its technique sensitivity, requiring a steeper learning curve compared to conventional methods.