When your chainring...

[Gooby]

... looks like this, get a new one!

[Beyond Rational]

That's hardly run in

[M400 NBL]

I've had a new crankset fitted because the teeth on the largest chainring were leaning considerably. It got a bit embarrassing when the chain came off 2 or 3 times to and from work.If you use your bike only on the road, I'd recommend a conker block (if that's the right way to describe a small close ratio rear cassette) because it looks like you would make use of the extra speed available.If you do go down that route you may as well have a larger road bike crankset and and derailleur.

[red355]

just use the big ring

[arryb]

What's wrong with that??

[matt-ITR]

The missing tooth is probably supposed to be there. Lots of (middle and big) chainrings have them to aid pickup.

I have seen alot worse... but it does need replacing

[Saddle bum]

Chainrings and cassettes get worn 'cos of knackered chains.

For 10-speed set-ups:
Shimano chain = 1500-2000 miles
Campag - 2000-2500

Others about the same.