my personal opinion is that brass has a finite life-span. I wont touch anything that has..... problems. Its easy enough to replace. I would pitch the dented ones. I cant speak as to weather or not it is safe. Sorry
Willie T, Cases with deep dents will increase chamber pressure so I would have to agree with wisem2540 and ditch them. Cases with light dents won't affect chamber pressure much at all so if you stay on the light side of maximum, there won't be any problems.
My Mini-14 dents the cases but they aren't deep enough to worry about. In fact much of the dent comes out when the case is resized. When fired, pressure will fire form the case and totally remove the dent. Of course another will appear when the case is extracted.
Pictures would be nice ... we might be able to give you a more defined answer.
I had wondered the same thing when I noticed the small dents in almost all my cases that were fired in my Stag Model 1.
In the research I have done - small shallow dents should not be a problem. Mostly like caused by the cases hitting a sharp edge on the case deflector. I have seen cases that had very deep and sharp crease like dents and those I would probably pitch.
Here is a photo of the brass ejected from this particular weapon.
My mini did the same thing until I installed an adjustable gas block. Now it doesn't dent or throw the cases 50 feet any more. A reloading friend who helps me with my reloading doesn't worry about small dings like that except in his rounds he wants to drive tacks with.
They are not bad enough to cause a pressure problem. Those dents are in the same spot and look to be hitting something on the rifle as they are ejecting like a scope or ring (if you have one on the gun) or hitting the edge of the receiver as they are coming out. Check for an area on the gun if you see any brass markings where they are hitting.
I didn't double check once before starting to shoot my sr556 and had the regulator set at 3 (max). I was one position in from far right on the line and all my brass went in the woods. When I found it every case had a hell of a dent. Dialed it back to 1 and it leaves a mark from the defector but no huge dent.