Gums have black like bruises to consider with poor hygiene habits, but also may be the emergence of dental calculus, wisdom teeth, pericoronitis and other diseases. 1. bad hygiene habits, usually have bad habits, often do not pay attention to personal oral hygiene, foreign objects hurt the gums, there may be black like bruises in the gums symptoms. 2. Dental calculus, some patients appear after dental calculus due to dental calculus attached to the teeth, may lead to changes in the color of the gums, so there will be black gums like bruising symptoms. 3. Wisdom teeth pericoronitis, some patients appear wisdom teeth pericoronitis, due to the pericoronary part of the more food residues remain, bacterial growth after corrosion of the teeth may lead to all the symptoms. Usually must pay attention to personal oral hygiene, keep a light diet.