I agree! I had my root canal complete 2 months ago. (in 2 appointments) I was given 4 shots of novocaine just to be sure from my dentist because it was my very first time getting a filling. Can you believe that! 21 and never had a cavity.
Anyways, I had the topical ointment first and then 4 shots, 2 around the tooth, 1 farther back by the jaw joints (ouch!!) and 1 by the middle of my front teeth (bottom) I was good and numb and didnt feel a single thing. I was so happy! Sore after it all wore off (1.5 hours for the work and another 4 for it to wear off)
The second appointment when I went back to have the tooth permanently packed and filled he gave me just the topical and 2 injections. 15 minutes into the procedure I was tapping his leg and he gave me 2 more shots.
For a regular filling I could probably do it on just the 2 but for the RC I for sure need more. I'm fine after that though. My dentist does use the gas but I never asked for it.
If you dentist does use it he should be willing to let you have it for your RC.
Good luck, I hope you have a speedy recovery.