I don’t think you can prove it, unless it is something they need immediately. Most children don’t get braces until their adult teeth come in. And that usually has most to do with genetics more than if you used a bottle past the major age of 12 months. My son just stopped using a bottle at 26 months. His teeth are fine. He saw a dentist, and her prediction was that his bottom teeth wouldn’t need braces, because of great spacing, but he already has tight spacing with his top teeth. Both my husband and I had braces, and our son seems to have my upper teeth (his two front teeth are identical to mine..one semi overlaps the other, even with braces, I never wore my retainer.) So, we know we’re doomed to kids needing braces. I talk on a lot of forums with parents. Most people whose kids need extensive dental work have been told it’s just crappy luck. None of them let their kids eat tons of junk, but some kids are more susceptible to bacteria that gives cavities.