quick question- is caulking needed around replaced new tub fixtures?

we've installed a new tub, and tiled, and put in the new fixtures, the only thing left... take a shower!
so i was just curious, is it necessary to put silicone around where the fixtures meet the tiles? i can't seem to find anyone saying it's necessary, but stilll curious.
thx!!! ~jewels

I would say so. It would keep water from seeping behind the fixture and getting the backer material soaked and causing mold.

Many of the trim plates for the valves have a gasket - no caulk is needed. It just depends...