G.S.
H., i just got my parenting magzine [march 2008 edition] and they talk about this subject. they say that it doesn't mean something's wrong. they say that it is a self comforting habit. like pacifiers. they do say to let your child's dentist know so that they can watch for tooth wear. they recommend to help your child break the habit by gently reminding them to not do it, distract them from chewing by changing what they are doing at the moment [probably zoning out while they are] and by giving them something else to chew on like pretzels, carrots, basically anything hard and crunchy to satisfy their urge. also my daughter did this and could ruin a new shirt or coat in an hour. her dr. said that sometimes it can indicate a attention deficate [sp?] disorder and they do it when bored or anxious. so changing what she was doing at the moment worked best. she still chews on her pen caps, and did do some damage to her teeth. but now she is in her late teens and is able to stop herself when she recognizes the behavior. hope this is of some help or at least you know you aren't alone!