Half an hour? Oooh, I doubt that.
My dentist always underestimates. He'll say 2 hours, and the assistants will schedule for 3, and it'll end up being 3.5.
I had mine out, and I've had numerous root canals, composites, new bridges, you name it, and I've never been put under or gassed. The most I ever did was take Valium because he said it'd make the painkiller last longer, but I didn't notice any effects. My dentist has this DVD thing with a headset, so at least I have something to do, although I can't hear it half the time with all the drills, and they knock the headset as they work. All in all, lots of fun.
Of course, I don't have any fears of dentists, which is awesome because I need so much done.
The cost of the work hurts me more than the work itself, heh.
Anyway, if you're awake, you don't feel anything besides the general feeling like someone's yanking on your jaw, which they totally are. I mean, it doesn't hurt or anything, not with the local. I'm probably kind of warped because I like knowing what they're doing. And I like being able to hold them accountable for anything they say or do because hey, I'm aware of it all.
After I had mine out, I drove home and hung out on the computer. You're not supposed to smoke, but I did, anyway. I never had a lot of pain, just a sort of ache. I was taking that drug that's steroids and Tylenol together, anyway, so that helped. I swelled a bit, enough that people commented, but I didn't even notice it myself until it was pointed out. Of course, you're stuck with soup and soft stuff for a little while, which isn't the end of the world, unless you're trying to go out to eat at work and can't find anything like that.
Like in all things, life goes on. You can be terrified beforehand and all, but before you know it, you're home, and it's done. Reality is rarely as bad as we make it out to be in our minds.
FYI, I've heard from people who've thrown up after being put under, and they had to be driven home and were all groggy and messed up for a while, so being knocked out doesn't sound like a total cake walk, either. It's not like you're going to be walking out of there in the same condition you were in when you walked in.