Obviously, the dishwasher will not clean out anything inside a bottle. However, temperatures in the rinse cycle of a dishwasher will run 195F, which will sanitize. As 'arturo7' stated, the best way to get a clean bottle is to rinse it thoroughly when the beer is poured. Obviously, if you get these bottles from somewhere else, you have to assume that the dregs have dried inside. Get that out by soaking in PBW or Oxi-Clean (I cannot use the latter, as my well water is too hard). Presumably you'll want the label off, to this will kill two birds. So when I'm ready to bottle, they're already clean. I do a twofold process. First I use a vinator to squirt Star San up inside each bottle; as I spray each one, it goes in the dishwasher. This process takes about 15 minutes. I plan it so I bottle the next day. When I get up, I immediately run the dishwasher, and then bottle when I get to it. This has worked for me for many batches with nary a problem.