So sorry it took me so long to get back to this post...
Well, the short answer is no, I don't personally know how to determine just by looking at the UID's teeth or their dental charts (CHARTS, not x-rays) how to determine if they had orthodontic care in their lifetime. BUT...often it is on the reports I rec'v. that a forensic odontologist has notated from THEIR exam. Usually that info. is paired w/ documentation, like, they can tell where teeth may have been pulled to allow more room for the teeth to spread out, or jaw re-alignment procedures have been completed over time to correct irregular bite patterns, etc. If one is looking at a lifetime of x-rays from a person who is missing that they are trying to compare, they can check for changes to the roots over the years.
As far as it being rare to have "perfect" straight, white teeth w/ no fillings and no orthodontic work...well, I happen to have been one of those persons until my mid-twenties!
![Stick Out Tongue :p :p](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
I don't know why...it certainly wasn't genetics! But I just didn't have any straightening needed, and didn't have a cavity until my twenties. I didn't really think of it as rare. Maybe it is...you know how it is if you live with somehting, it just seems normal for you!
Such seems to be the case with P. Lav. as well. They put her as closer to the lower end of the 17-22 age range, w/ great teeth.