There is a small possibility that your daughters dental fixtures may set of the security scanner. But you could ask for a 'body/hand' search instead. You don't pass through the machine that way, but that said, it would mean an Officer man handling your daughter so that might not be a good idea.
I do not forsee any problems.....if she does go through the machine and sets the alarm off, you can easily make some sort of joke about it depending on her age.....say something like she has been picked out because they know she has been a good girl at school or something...anything to take her mind off why she set the alram off. But lets face it, it is only a short quiet beep these days, she may not even notice it.