I have had unbelievable dental problems my whole life, mostly due to having celiac disease - which I did not find out I had until this year. The worst pain I experienced was once, about 30 years ago, when a tooth's nerve died. I could not get to a dentist that day, so I drank a pint of Jack Daniels straight down which helped somewhat. Having a dead nerve sucks. Instead of being sensitive to cold, it's extremely sensitive to heat. If this happens, then you KNOW you've got a serious problem.

On another happy note:
I read a story, years ago about a dental patient getting the shot of Novocain in the back of the mouth. The dentist missed the mark by a little, and injected the Novocain into the base of the patient's brain. The person went into a coma and died shortly thereafter. This is a good anecdote to tell people that are nervous about going to the dentist, lol.