Re: According to the dentist my son has six cavities. What should I do?

"..and always sent me to the same root canal dentist. Never had a cavity until I was 18, in the Marine Corps."

Oh yes, those "Marine Corps" dentists.  They're actually sailors.  While in the Corps I had a tooth pulled by a Navy dentist who then installed a bridge to replace it.  The bridge lasted about 10 years.  The SOB was simply practicing on me getting ready for civilian life.  He'd been drafted (as my Navy dentist brother-in-law had been during that era) and was simply playing games looking for guys to practice on knowing that if he screwed up nobody would ever touch him.

My tooth didn't need pulling any more than did my big toe.  If that tooth really needed work I'm sure either just a plain filling would have worked or a root canal at worst.

I agree that second opinions with X rays are the way to go.