Preschool Behavior: Thumb Sucking

I was 13 when I finally stopped sucking my thumb. That's not a typo, folks. Thirteen. (And yes, in fact, I can say orally fixated, thank you very much.)

It surprised me, since I had been such a devoted thumb-sucker, that neither of my kids developed the habit as babies. Until now.

The past few nights, Ben has been sucking his thumb at bedtime. He's a few months past his third birthday. I talked to his favorite preschool teacher today, and she said that there is one dedicated thumb-sucker in the class, and that yes, she had noticed Ben was starting to do that at naptime, but no, she couldn't think of any other big changes in him over the past couple of weeks, aside from the fact that he's growing more and more comfortable there: talking more, playing all the time, happy and smiling rather than keeping to himself.

So now, of course, I'm wondering where this is coming from. I'm totally disinclined to make a big deal out of it, since he's braces-bound no matter what (thanks, genetics), and because I know that breaking a habit like that is really hard to do until the kid is motivated to do it himself. But on the other hand, I'm concerned that this new "habit" has a deeper meaning, and that if I continue to be a laid-back mama, I'm going to be missing an opportunity to intervene in some larger emotional issue.

My bet is that I'm dealing with nothing more than a little boy who recently had his bottles taken away from him because all that milk was likely causing his constipation. My bet is that he's just replacing the bottles with his thumb, especially at bedtime, because he's simply not getting his sucking quota met during the day. But what if my bet on this preschool behavior is off? What if I'm missing some big nasty thing that this is a sign of? How do I know I'm not screwing up, big time, just because my own thumb sucking didn't amount to anything big?