When a child's permanent teeth appear, there's usually some push going on, hopefully in the right direction. Although any tooth can jostle its neighbors, the teeth that have the worst reputation are our third molars -- our wisdom teeth. They're the last to come out and often shove other teeth out of their way.
Most mouths can't usually accommodate wisdom teeth, and they end up pressuring the rest of the teeth, disrupting their alignment. They can often cause pain and swelling.
Routine X-rays, done when a person's around age 12, give us early warning of problem molars and tell us whether they need to be extracted. Wisdom teeth, like troublesome neighbors, everyone's a lot happier when they've moved out!