When one or more teeth are lost, the remaining bone and gum tissue slowly reabsorbs into the body, causing the supporting bone around the missing teeth to shrink. A ridge augmentation is a type of bone graft that is performed when the jaw is not wide enough to support implants.  The supporting bone height can reduce by at least one millimeter around the site of the tooth after extraction. This can make placing and restoring implants difficult or impossible.  A ridge augmentation and preservation procedure performed at the time of extraction prevents bone loss. If this procedure is not performed at the time of extraction, it may have to be performed later on to develop the required bone mass and density for implants.