Why wouldn't it numb?

I've just been to have a tooth pulled, and she gave me the maximum dose she could gove me, but I still felt pain in my tooth. I've had teeth out before, so I k ow you feel pressure and not pain. But I was very much still feeling pain. I dont think the dentist believed me, but I have been referred for gas and air.

Is there any reason why it still be felt? It is infected, so maybe the numbing doesn't work on the tooth?

Also any insite on how gas and air feels?