Depending on how large they are, you can trim the dead growth off now...but real soon, arborvitae should not be pruned after Aug. 15 or so. If the branches are not broken, they should shape up, you can kind of fluff them up with your hands, just return them to their normal shape. Do not take off growth down to the bare branches though...they will not regrow from there, try to leave a good healthy amount of foliage. Of course prune them all over for shape at the same time, do not just prune off the bad stuff. Good Luck, Helen.