Bleeding gums with only one tooth may be due to tooth decay, gingivitis and calculus. 1. Tooth decay: In daily life, consuming foods with high sugar content for a long time may lead to demineralization of teeth and formation of cavities, resulting in tooth decay. When the cavity is too big, it may stimulate the gums, leading to inflammation and congestion of the gums, and bleeding. 2. Gingivitis: usually due to infection, abnormal hormone levels and other factors that lead to inflammatory lesions on the edge of the gums, due to the stimulation of inflammation, which may lead to blood vessel hyperplasia and congestion in the gums, resulting in bleeding gums. 3. Calculus: Bleeding gums occur due to the irritation of the gums by inflammatory substances such as calculus. Bleeding gums of only one tooth may also be related to other reasons, a single symptom can not determine the specific cause, it is recommended to consult a doctor for examination in a timely manner.