I noticed a dent on my 2-year-old Abus Gamechanger 2.0. It’s not been crashed, so this must have occurred during storage or transport, but I am not sure.
This is my only road helmet and has seen around 12,000km. I can’t feel any squishiness around the dent.
It’s likely Ok, especially if there is no changes in the inner areas of the dent. That said, if it was mine I’d ditch it simply to be on the safe side.
If I had a helmet with a dent like that it would definitely be on my mind when riding. The subsequent loss of enjoyment would be enoough to make me buy a new helmet.