Without knowing the details, I think a knee jerk reaction to the procedure is maybe...and I emphasize MAYBE - not proper. A 5 year old is very likely to make a sudden movement that will cause her significant damage while the dentist is inside her mouth.
Having said that, I think the parent should indeed be in the room. That’s my main issue off the top.
Geez...bike helmets, strapping kids into dentist chairs, medicating them so they sit still in class...
I have no idea how several millennia of humans made it to adulthood...
When the father beats the hell out of the dentist, I hope they don’t file charges.