Are all on four dental implants sufficient to prevent bone loss and the associated excessive aging of the face?

I have read several articles lately that promote the concept that a single lost tooth is enough to trigger bone loss. If that is true, how can all on four prevent bone loss (a concept that is routinely promoted in the dental industry)? Certainly four implants will not provide the same measure of pressure to the bone. Have I misunderstood what I read? Do all on four merely offer a partial solution to bone loss that can never compare with a full set of teeth?