Today I'm recovering from a big sleepy-bye dental adventure yesterday. Extractions of two broken crowns, a root canal prep for another crown, and various other Very Scary Things. I am grateful that they pampered me. (No one in this area does laughing gas, and my previous dentist moved to Perth...)
I became very dental phobic as a young kid, and several years of secret teen rebelliousness (ie. not brushing often) resulted in massive amounts of silver fillings in my early 20s, which set me on a path to oral destruction. Being needle phobic doesn't help either.
Unfortunately, I found the more gentle/kind wave of younger dentists way too late in life to cure me of my phobias, but nitrous oxide was the only way to get me through some the really difficult years, and having all those awful silver fillings replaced by the newer technologies. Mind you, gas never works as well as that very first time; my current dentist likens laughing gas to heroin. Your second or third, or any subsequent hit, will never be as... glorious as that first one. (Ah, I still remember. 80s dentistry hurt, but you just didn't care.)
So, yeah, yesterday's general anaesthetic experience was actually very civilized, and my mouth is surprisingly okay. They were removing roots, since the crowns had already broken away - "mechanical" failure rather than decay, but that wasn't totally reassuring - so what would have been awful even with nitrous oxide, is blissfully not even a memorythanks to the full anaesthetic.