Did you ever find out what it is? I have the same visible signs. 4 of my bottom teeth on the inside. the dark lines start from gums and thing out as they reach the top of the teeth. I am experiencing no pain, my bottom teeth are close together so I hope it's a stain from poor flossing.
Well its been a year since my last visit....so I'm thinking I will deff make an appoint within the next couple of months. But yeah, i dont have no pain or bleeding or sorness in any of my teeth. I think they just might need a good dental type cleaning and they should be good again. Thanks!
it could be just staining. i would ask during my next dental appointment but as long as you are symptom free i wouldnt make a special trip (unless you dont go regularly).