Yes. One implant per tooth is not needed and one can actually have as few as four implants to replace all of the upper or lower teeth. There are a variety of options for the type of bridge, which can either be removable or fixed in place.
All-on-4 is a trademarked treatment procedure that essentially involves replacement of all missing teeth in one jaw by using only 4 implants. This procedure is especially beneficial in patients who have lost a lot of bone in the back areas of the mouth.