Oh my God.... please don't EVER take your son back to that horrid horrid human. EVER. Not only does she not have any people skills, she is un-informed and unprofessional.
First of all, there are some dentists that don't let parents back there because the parents can make it worse for the kids and the parents can be hard to deal with and distracting. However, he's your little guy.... so you need to do what is best.
PLENTY of little kids are put under general anesthesia all the time and are fine. Pick the lesser of 2 evils. I would probably go under general anesthesia... if you go with someone who has worked with kids it won't be a problem.
Call the University of Medicine and Dentistry of New Jersey, umdnj, NJDS.
110 Bergen Street Newark, NJ 07103
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Their professors have probably taught 1/2 the Dentists in the state. They should be able to refer you.
They might be able to see him. Lots of people don't want to go to a college to have work done. But if you can take a little extra time it's actually the BEST care because they are supervised and they are doing their absolute best and follow all the rules step by step.
Good luck.