Black lines on inner side of upper molar teeth. it was minor but now i am feeling black spot on innerside of all teeth(6) from the left molar side.

Addison's Disease?: The list of what could be causing this is extensive. Something know as Addison's Disease would be on the list as well as heavy metal ingestion and MANY others. Best to see your healthcare provider for full evaluation. Lesions must be seen, felt and sometimes biopsied in order to give you the proper diagnosis. Hope this helps. Best of luck. Dr R

Diet related: many possibilities, but black lines due to stain on teeth is commonly found in tea drinkers and those eating Indian foods. If you are feeling the stain, get it checked.

Guess: Without being able to examine you it would be pure conjecture. May be a line of tarter, stain from an old silver filling, fractures that are staining with time, or so many other possible causes. Yours is just one of the many reasons that regular dental examinations are important. Bite the bullet. Call a Dentist for an examination. You'll be glad you did.