As explained in the FAQ, bone disappears when it's not used (if no tooth is present). Sometimes before an implant can be placed, bone needs to be added to the site and allowed to regenerate. The bone can be taken from another site in the mouth or other sources can be used. This bone graft acts as a scaffold for your own bone to grow across, regenerate and calcify. As the new bone matures, the bone graft material resorbs (slowly dissolves away). A large percent of the time, a membrane is used to guide the graft to grow to the new bone in the proper way. This is called Guided Bone Regeneration (GBR). Many different membranes are available to achieve the desired result.

A bone graft may or may not be done at the same time the implant is placed, depending on the individual situation. If it is determined that they need to be performed at separate visits, the length of time between them is normally 4 to 8 months, again depending on what type of bone the graft will be placed in.