Join Date: Oct 2003
Location: Perth, Western Austral, Australia.
It's not a good idea to continue using that helmet. A scrape measuring 2"x3" is huge on a helmet. Apart from that, helmets are made from plastics or composite materials, not metal, and they don't dent, they just weaken and fracture.
You can continue to use that helmet, but you can't expect it to protect your head properly next time you crash. It was an expensive and very good helmet, but it's done its job and it's time to replace it.
Having said that, it's your head, not mine, and in the past I have been guilty of wearing a helmet after many drops/falls/kicks-down-the-road, and waaaay past its use-by date.