My 9 year old daughter has been a chronic thumb sucker since she was born.  A few months ago our dentist told us my daughter's thumb sucking was causing several problems with her permanent teeth which have been coming in recently and her mouth and jaw development.  He said she would need an appliance to help her stop if she couldn't do it on her own. 

I tried having her sleep wearing one of my old winter gloves on the hand that has her favorite thumb and it worked great.  She thought it was fun wearing the glove and it kept her from sucking her thumb all night.  I'd peek in on her periodically just to be sure.  After one month of this we visited the dentist and he said her teeth were already starting to straighten.  I could see the difference from the previous pictures he'd taken.  What had become a pretty large open bite had gotten much smaller and there were other positive changes as well. 

The dentist said to keep wearing the glove for 6 more months to make sure the habit is broken.  To keep it interesting for my daughter, I purchased some inexpensive ($6.50) soft, white gloves at a military surplus store for her to wear.  She likes them so much she sleeps in both of them and wears them around the house!  We also use a calendar to track her success.  She gets a sticker for each night she doesn't such her thumb and a prize once she accumulates a set number. 

Our previous dentist didn't think the thumb sucking was a problem since it was only at night.  I'm so glad I changed dentists and that we're now putting an end to the thumb sucking!