Dark spots on the teeth of a 4 year old baby could be caries or pigmentation. Different causes should choose different treatment. 1. Dental caries: caries formation of black spots by brushing can not be brushed off, and will form a “hole”, which is the need to find a professional dentist for treatment, removal of decayed material after the use of glass ionomer or resin filling, especially 4-year-old baby teeth from the replacement of the baby teeth is still relatively early, it is recommended to the hospital in a timely manner for treatment. 2. Hyperpigmentation: black spots caused by hyperpigmentation are usually attached to the surface of the teeth, which makes the surface of the teeth not smooth, and facilitates the formation and adhesion of plaque, and makes it easy for dental caries to occur. Therefore, it can be treated by timely brushing, tooth surface polishing, ultrasonic cleaning and other methods. Therefore, it is recommended that 4-year-old babies with black spots on their teeth should first go to regular hospitals for examination to determine the cause before receiving professional treatment methods.