Guess who isn't doing well in reading comprehension. Re-read her
paragraph (which you nicely quoted).

In the book "where there is no dentist" it details nicely what is the
anaesthetic procedure -- and also that lower back teeth can be
miserable to try and numb. When I had my root canal, the specialist
didn't put in the needle for the outside gum, he just did the across
the mouth under the lower teeth needle. I noticed he'd forgotten, but
he didn't look like he was interested. He did seem concerned that each
time he poked me with the file I bounced off the ceiling.

Shari wrote:

There are other, more potent anesthetics (such as articaine).  Still,
sometimes you get a bad batch of anesthetic or it's just a bad day.
You haven't said what tooth this is; in my experience this is most
likely to happen in lower molars.  Also, if the nerve is in trouble it
may become more difficult to numb.  If you are getting significant
syptoms in the tooth this possibility should be checked out.

Steve

I don't numb easy either. I had some dental work on some top teeth and my
dentist push into the bone above my tongue to numb the soft tissue. That
works...

I had two teeth pulled one time without numbing...