<unk>  is a grey, blue or black area of discoloration on the mucous membranes of the mouth, typically on the gums of the lower jaw. It is a healthcare caused lesion, due to entry of dental<unk>  into the soft tissues. It is common, painless, and benign, but it can be mistaken for melanoma.
Amalgam tattoo
Soot tattoo
Debulking
Circumcision
Cigarette burns
Tincture of benzoin
Scorpion sting
Indoor tanning