I switched dentists to one closer to home recently.  I had a filling go
bad and he recommended getting an overlay instead of just replacing the
metal filling.  The problem is that I have never felt comfortable with
chewing on that side and, recently, ran my fingernail along the top of
the tooth and found one spot that give a little twinge, like touching a
nerve but it doesn't make me jump out of my chair.  The slight pain
goes away immediately, never lingering

The dentist thinks I may have a high spot and it's aggravating a nerve
there and has honed it down but two days later, I still feel the
twinge.  It doesn't feel real bad like shooting down into my gums so it
doesn't sound like it needs a root canal.  Not that I would know but my
wife, who has had one, told me you 'know' when you need a root canal.