<s>[INST] hi, doctor ... i am 22 years old ... i have a crown in my front tooth(probably when i was 13 or 14 years old) .... but just noticed that through out my gums there are black lines .... even in the lower part ... i have not really noticed since when .... i have no pain .... but this really got me scared .... hoping  for a reply,sincerely [/INST] Hi, Thanks for asking the query, Gingival pigmentation is he main cause of black gums around teeth. Gums with poor oral hygiene may also cause gums to turn black. Smoking and use of certain medication can also cause blackish gums. Visit to a Dentist and get the checkup done. Some Periodontist now offer cosmetic bleaching procedures to lighten the appearance of your gingival. This can also be improved by some surgical procedures in which the outer layer of gums is removed surgically. Hope you find this as helpful, Regards... </s>