Some causes of dark spots on the gums are melanin pigmentation, amalgam tattoos, smoker's melanosis, some medical conditions and oral malignant melanoma, according to the Oral Cancer Foundation. Most dark spots that appear on the gum, such as amalgam tattoos and melanin pigmentation, are harmless, while others are more serious.
Melanin pigmentation spots can be due to an excess of melanin production. Amalgam tattoos are caused when small particles of silver from the removal of a filling migrate to the gum area. Smokers can also develop these dark spots that are called smoker's melanosis, states Medscape.
Dark pigmentation spots can also be caused by medical conditions, such as Addison's disease and Peutz-Jeghers syndrome (PJS). PJS is a hereditary disorder in which intestinal polyps occur, and a symptom is the formation of brown to black spots on areas that include the gums, notes the National Institutes of Health's MedlinePlus. There is a risk of polyps becoming malignant. The most serious condition associated with gum spots is malignant oral melanoma, which requires treatment.