"Hot" tooth - Myths or Reality?

I came across the following posts on a dental board and was wondering
what the general take on this subject is:

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MaryAnn
posted 07-27-2005 10:09 PM
I've heard stories of people who have had root canals on abcessed teeth
that required up to 20 shots to barely get numb. I've also heard that
dentists don't perform root canals until the infection clears up
because the anesthesia won't work at all. Why is that?

..
Jeffrey L. Wissot, DDS
posted 07-28-2005 07:07 PM
Popular myths. RTCs can, and should be initiated despite acute symptoms
for a safer, more predictable course of treatment.
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Myths or reality? (I realize that the 20 shots statement is a bit of an
exaggeration, but generally speaking?).

.