Sometimes, prior to the placement of dental implants, there is a need to enhance the foundation of the alveolar, or "jaw", bone structure prior to implant placement. A solid bone foundation is required for "osseointegration" (or fusion of the implant to the bone). Only your surgeon can determine if this is necessary.
After tooth extraction , it may be necessary to place a bone graft into the socket to prevent bone loss. This generally needs 4 months of healing prior to the implant placement. Other times, the maxillary sinuses may need to be "lifted" to achieve proper bone height to receive implants. These types of procedures utilize a synthetic material that, when mixed with a small amount of the patient's blood, result in a complete regeneration of your own "native" bone within 4-6 months. These procedures are extremely easy on the patient as there is no need to "harvest" bone from elsewhere in the body to achieve the same end result.
When teeth have been missing for a long time and there has been tremendous "atrophy" of the bone, then it may become necessary to "build up" a larger volume of bone prior to implant placement. This would require harvesting bone from somewhere in your body, usually a small block from your jaw. For this, IV sedation may be used for comfort. In a small percentage of severe cases, large volumes of bone may be need to be harvested from the hip under general anesthesia in the hospital.
Oral and maxillofacial surgeons are specially trained in harvesting and placing bone grafts in the jaws. A consultation with a surgeon can determine which treatment options are available to you.