Noooooooooooooooo. I would not go to any dentist that stated I had to "hold down" my child while they clean their teeth!
An exam should suffice at this age! And discussion about how to brush her teeth, what type of toothpaste to use...etc.
Find another dentist!
Also, FYI....I've been to several ped. dentists that will not allow a parent to go back to the examination room with their child. I have always been an extremely educated parent and will ALWAYS be with my child at ANY medical appt, regardless of "office rules" of each doctor. I am my child's guardian and need to know every procedure, question, discussion between the doctor and my children.
Things happen when children are alone and unable to defend themselves. I am always cautious of the happenings of my children!
Never let any doctor, nurse,...etc. tell you that you are not allowed to be with your young child during the appointment!
Sorry about the soapbox; I just want parents to feel empowered and knowledgeable!