There are two ways of looking at hair restoration and hair restorer products.  The first is as a way to keep what hair you still have.  This is what most hair loss products focus on.  How can we keep what hair there is left and not lose any more.  Topical solutions such as those containing the FDA approved drug Minoxidil work on this premise.  The drug inhibits the levels of DHT in the blood from causing the death of the hair follicles.  This is really fairly successful.
The other job for a hair restorer is to bring back hair that has already fallen out causing a bald spot.  Most hair loss remedies will not do anything to bring hair follicles back to life once they have been rendered in effective by the DHT.  The drug Finasteride has shown some re-growth but not massive amounts over a large area of the head.  At this point about the only option is to get hair implants where hair follicles are removed from one area of the scalp and inserted into the bad spot.