<s>[INST] I have a dark ring on the gum line that encircles one of my back molars. It is not sensitive, gum lines are healthy, and there is no pain associated. I did floss it really well yesterday and a small popcorn kernel came out and it has been weeks since i had popcorn. Any thoughts? [/INST] Hello thanks for consulting at Chat Doctor,the dark ring on the gum line could be tartar/calculus present.which appears as black line,you need oral prophylaxis- scaling and polishing,you also need to do gum massage with the pulp of your finger,do salt water gargle thrice daily,nothing to worry, also get an Iowa radiograph. To check for alveolar bone loss,consult a periodontist for a check-up and treatment.hope it helps,take care. </s>