I agree with you saying that dentists aren't always sure of what they're doing or aren't prepared for unexpected changes. I had braces put on when I was about 10 years old. My teeth moved extremely fast, allowing me to not require headgear. By the time my braces came off, however, puberty was in full swing and my face was undergoing several changes. My mandible lengthened dramatically, giving me a sarah jessica parker "long face," and my right mandible grew slightly longer than my left one, causing my jaws to have an uneven appearance. I'm convinced that my orthodontist could have lessened these changes had he planned enough and noticed the changes as they occurred. But oh well, atleast my teeth came out straight, lol!