Implants can be used to replace a single tooth or all teeth in a jaw. And as I have already mentioned, implants can be employed to replace no teeth. That is the case when an orthodontist is trying to align your teeth and wants accelerated movement.
The minimum number of implants required depends on the number of teeth to be replaced. Replacement of one or two tooth requires just one implant. A greater number of teeth in adjacent locations can be replaced with a single fixed bridge using two implants. A full bridge replacement can be applied using four, six, or eight implants in the upper jaw, and five or more in the lower jaw. Note that not all 16 teeth are needed in a jaw, rather only 7 teeth in each jaw (28 in total) will suffice. Why we don’t we replace missing third molars? This is because third molars usually don’t play any active role in mastication and speech. Therefore, dentists do not usually replace them.
So, coming back to the question, you can replace as many teeth as you want to replace. If you need a single tooth replacement, you can get a crown. In case you need replacement more than two teeth, your dentist can give you a partial denture or a bridge. Finally, complete dentures can also be attached to implants for the replacement of all missing teeth in a jaw.