When a tooth is lost, a whole series of events can begin to occur. Chewing on the affected side becomes more difficult and over time the remaining teeth can actually tilt and erupt into the open space.
Depending on the location of the missing tooth, we would most likely recommend either a dental implant, a bridge, or a partial denture.
All of these options have their benefits and drawbacks. If you would like more information your dentist can usually schedule a consultation to go over the specifics of your case.