I had dentistry done without anasthetic once, which was probably a stupid thing to do. But the assistant observed that even my fingers didn't twitch, which were folded together across my front. What I did was focus really hard to a point between my eyes (with my eyes closed), and sense my breath through my nose, and work at simply not responding to any pain sensation, no matter how bitter it became. Seemed to work. But I'd be interested as well to see if anyone knows whether this is a known focus point, or not.