Can dentists and doctors really give you a mask filled with gas that makes you fall asleep?

Question

Here's what I was told by my friend: he went to the dentists to get his wisdom teeth out, and instead of being injected (which I've had quite enough of) they gave him a mask to put on. Apparently the mask was filled with a special gas, because they told him to count down from 10, and by the time he reached... 9... he was out cold, and then the next thing he knew, he was awake, and the procedure was done. Can and do they still do this? I'm sick of injections.

Answer 1

They're still going to give you injections...

gas alone won't do the job.

Answer 2

all you have to do is

think of a nice big cookie and some coffee