While this is arguably the least harmful category on our list of teens' oral habits, it still comes with its fair share of troubles. Teenagers are known for nervous habits like gnawing on pen caps and biting fingernails [source: Leung, et. al]. Sigmund Freud might have said that such behaviors represent a dysfunctional oral fixation, but the most likely causes of chewing non-food items are boredom, anxiety or stress [source: Tanaka, et. al].
While these oral habits are common, they come with a variety of consequences. For starters, many inanimate objects -- and even hands -- can be covered in germs. It's unhygienic to put such things in your mouth, and it can lead to infections. There's also the risk of dental problems. Chewing and biting non-food items can lead to broken teeth and injured gums. If you catch your teen continually putting things in his or her mouth, discourage it.
Believe it or not, a healthy alternative may be chewing gum. Although many schools don't allow kids to chew gum in class, the practice does have some benefits. Sugar-free chewing gum can help alleviate dry mouth and bad breath, and may even help prevent tooth decay [source: WorldDental.org]. And, in fact, the act of chewing gum can help reduce stress and improve mood and focus [source: McGonigal].
The next oral habit is a lot more grown up.