All you need to know about fluoridation is set out in this recently published report. Apparently there's a bit of legislation which requires these reports to be published every four years, so this is a government sponsored piece of research. But it's well designed (an ecological study on a very large scale) and well written up.
No startling new findings - fluoride reduces caries, more so in deprived areas, and doesn't cause hip fractures, kidney stones, bone cancer or the proliferation of little green men. (But that won't stop the opponents of fluoridation from claiming that it does.)