Socket Augmentation: Rationale and Technique (Part 3)

Guided Bone Regeneration (GBR) 

Cases in which the buccal plate is absent or was lostduring exodontia require a different approach.
GBR techniques associated with or without immediate implant placement are required to treat these ridge
defects. A delayed implant placement approach is indicated when primary stability of the implant cannot be predictably achieved, particularly in sockets of bi- or multirooted teeth.
In these cases GBR techniques, such as the “sandwich bone augmentation,” are indicated (Wang et al. 2004b).

Abd El Salam El Askary, Fundamentals of Esthetic Implant Dentistry, 2007