How to explain this.
The fact that the patient WAS crying and needed "support", i.e. behavior management, is what the charges are based on. They were able to do a quick, successful job BECAUSE OF their expertise. They are entitled to be compensated for this. To an outsider, it didn't appear anything special was done, but it was.
If you read through some of the links posted, you'll see that Mom being in the room in and of itself is an accepted behavioral management technique. I'm sure there were others, but we only have Mom's take on it. I'd bet if the dentist could respond here, we'd hear others specific to the case.
I'm not sure why this is such a hot button issue for people.