Nothing prevents wires from entering your tires. They'll go right through the Conti Gatorskins, Bontrager Hardcases, Specialized Armadillos, and other flat resistant tires, though they provide much more resistance to wires than racing tires.

Wires often break off when they enter your tire, so make sure you get all of them out -- this can be tricky since you might not be able to feel the tiny bits stuck in your tire with your fingers, but they'll work their way back into the tube after awhile and puncture it again. I find a sharp blade to be indispensable for digging embedded wires out.

The Schwalbe Marathon Plus are much more resistant to wire flatting due to the blue layer, but those tires are so slow and heavy it's like riding in sand.