A stain or a small cavity?!
Question: A stain or a small cavity?
Answers:
Hi
They might be vertical cracks in the teeth most people have small cracks from clenching there teeth and crushing ice. These cracks do pick up stains from coffee and tea, you should be fine, as long as they are not sore, next visit to the dentist get them to show you with the blue ultra violet light, (it makes them easy to see).
All Dental Options
It COULD possibly be the start to a cavity, but then again, it could just be a stain. The only way you would know for sure is to go to the dentist. They'll give you an X-Ray, and if they find decay, they'll most likely drill and fill your tooth.