Tooth decay and breakage in four-year-old babies may be related to tooth decay, commonly known as tooth decay, in most cases. If not treated in time, it may also lead to more serious complications, such as pulpitis and periapical inflammation. If you find that your baby has abnormal teeth, you should take your baby to the hospital for medical treatment in time, and after the diagnosis, choose the appropriate treatment method under the doctor’s suggestion, and do not give your baby medicine without permission.1. Etiology: tooth decay is mostly caused by bacterial infection, such as Streptococcus mutans, Actinomyces, Lactobacillus, etc. It is mainly caused by the bad habit of diet, if eating food with high sugar content and incomplete cleaning, the sugar can stay on the teeth and lead to the breeding of bacteria, thus causing tooth decay. At the early stage of the disease, there is no obvious cavity, and white plaque will appear on the surface of the tooth, and at the later stage, the cavity of the tooth will become bigger, which will lead to the tooth decay and break off; 2.Treatment: If there are symptoms, you should take your baby to the hospital for treatment in time, and you can use fluoride, such as sodium fluoride glycerin paste for treatment under the advice of the doctor. If the symptoms are more serious, repair treatment, such as silver amalgam filling, composite resin direct bonding restoration, inlay restoration, etc., can also be carried out under the advice of the doctor. If accompanied with pulpitis, periapical inflammation and other diseases, root canal treatment is also needed if necessary; 3. At the same time, parents should supervise baby to brush teeth at least twice a day and rinse mouth after meal to develop good hygiene habits, which can effectively control the generation of dental plaque and prevent tooth decay.