A: Second adult molars and moderate dental needs make for the ideal Invisalign candidate. It’s appealing for kids who are sensitive to metal-mouth jokes, and it avoids sore mouth and gums. But treatment can lengthen if the removable trays are lost by a child who takes them out often. With braces, the orthodontist is in control, which can mean more effective treatment. But a mouth full of brackets and wires can make brushing and flossing hard, leading to poor hygiene. The verdict: If your child is pretty conscientious, go Invisalign. But a forgetful kid may have to grin and bear braces.