Dowels work too if you've got them. I use that method for concrete too, since I find tapcons frequently fail to grab. Drill out the concrete hole larger than the screw. Shove a dowel or a bunch of toothpicks/splinters into the hole, then drive the tapcon or a wood screw in. Holds like crazy since the wood conforms to the concrete wall imperfections. Might rot over time though. Maybe plastic is better.