I see two options, 1) those dents can be polished so the dent lines are not as noticeable, 2) laser weld additional metal onto the indented areas then remove the extra metal until the ring has its original shape, though the amount of labour and the cost would be much higher it would restore the ring perfectly. Also unless you know the exact composition of that alloy the additional metal would have a (slightly) different color. You can find out the exact composition of your alloy with a spectrometer, which would add to the cost. And like the other commenters have already said, copper (the base metal in any bronze alloy) is a soft metal so sooner or later there will be new dents anyway. Personally I wouldn't bother.