Here is some information from on implants from the office I used to work at:

A dental implant is a titanium implant post anchored into the jawbone as replacement for a missing natural tooth root and into which an artificial tooth is attached. The implant is held in place by new born growth stimulated by the anchor. The outcome is a very strong and stable tooth that is like a natural tooth. Generally, the placement of dental implants involves two separate surgical procedures. First, the titanium implant is placed into the jawbone. The implant itself is not visible and may need months for the bone and implant to heal together, a process called osseointegration. After osseointegration, your surgeon will perform a simple procedure to uncover the implant and attach a small post. This will serve as an anchor upon which your general dentist will place the artificial tooth. In some cases treatment may require only one surgical procedure and patients can have teeth placed almost immediately.