Smokeless powder is, as I read in my reloading manuals, funny stuff. The pressure it generates depends upon the volume in which it is contained. And it is, apparently, not a linear relationship. For example, we are warned that bullet setback, reducing case volume, in a high pressure cartridge can cause pressures to spike alarmingly.
This makes me cautious of anything other than the smallest of dents in a cartridge.
If I get a tiny dent in a cartridge, I'll fire it, provided that the dent has no sharp edge, and that there is no "tear" in the brass.
But if the dent reduces the volume of the case very much, I'm not messing with it. The cost of a cartridge isn't worth it. Probably would get away with it. But I don't like betting on probably.