Severe dental fluorosis in child.?

fluorosis happens if the person gets too much fluoride, a toxic waste product left from aluminium production. Instead of having a safe place, they dump it into people. Tooth paste, water, dental products. Fluoride turns into calcium fluorid in the body and decay the bones, close the head bones of babies too early and calcify the pineal glant which produce the very important melatonin and serotonin. Prozac is pure fluoride and if you find it in water, it is a mass medication. The damage to the teeth is not reversible. 

Sounds like you are more obsessed with this than he is.  Leave him alone and don't mention it anymore.  He's only 10 and you'll screw him up if you keep this up.

Dentists deal with teeth not Doctors. Try one of those.

I assume you've spoken to dentists, not just doctors?

And also asked them why?

There may well be very valid reasons why teeth whitening treatments can't be used at his age.