Thank you for your question.
As a 27 year old, you might be interested in the book:
GROWING A HEALTHY CHILD, SECRETS FROM A WISE OLD DOC
Are these lines something that you noticed in a certain light, and do they run top to bottom? If so, it sounds like they could be what we refer to craze lines. If they are craze lines, there is nothing to worry about. They are micro fractures in the enamel of the teeth and they are very common. Most of the time, people have them, they don't know because you can not see them. They start to become visible when the light hits them the right way, or if they pick up some staining. If they do pick up staining, you can do some teeth whitening to lighten them up again.
Hope this helps.
My best to you!
William F. Scott IV, DMD