One year old baby teeth yellow, may be related to dental caries, plaque, tetracycline teeth and other reasons. 1. Dental caries: under the action of bacteria, diet and other factors leading to the destruction of hard tissues of the teeth, yellowing of the teeth can occur. 2. Dental plaque: due to oral bacteria attached to the surface of the teeth, if the plaque is not removed in time, the plaque and the deposits attached to it will gradually calcify, and yellow tartar can be formed. 3. Tetracycline teeth: the use of tetracycline antibiotics during pregnancy or infancy can cause yellow teeth in children. Parents are advised to take their babies to the hospital in time to clarify the cause, and if treatment is needed, standardized treatment should be carried out under the guidance of the doctor to avoid delaying the condition.