The reason for black gums may be the following: 1, congenital factors caused by the gums are born with more internal melanin cell deposits, which will make the gums black, just like some people are born with a very white complexion, while others are born with a very dark complexion is a reason. 2, the presence of heavy metal poisoning in the body, in this case to go to the hospital for systematic examination and diagnosis. 3, long-term smokers will have black gums. 4, due to poor intra-oral hygiene, resulting in the accumulation of tartar on the edge of the gums, thus causing the gums to blacken. The tartar is dark brown and the large amount of tartar accumulated in the periodontal pockets will make the gums appear black, in this case go to the hospital for ultrasonic cleaning treatment. 5, if it is a tooth local gum margin blackening, most of them are caused by the tooth having a metal crown or a metal porcelain crown restoration.