There are many reasons for slow tooth replacement, which may be caused by improper diet, systemic diseases, retained milk teeth, or other reasons, patients need to consult a doctor in time for a clear diagnosis. 1. Improper diet: children like to eat soft and fine food, which will have a certain impact on the eruption of permanent teeth. Parents should let their children eat more coarse fiber and harder food during the period of tooth replacement. 2. Lack of nutrients: It may be caused by the lack of calcium, phosphorus and other nutrients, calcium, phosphorus and other nutrients are the nutrients needed by the teeth, lack of calcium and phosphorus and other elements will lead to poor development of the teeth, tooth replacement time is delayed, parents should encourage children to eat more fish, shrimp, milk and other foods. 3. Retained milk teeth: there may be reasons for retained milk teeth, milk teeth fall out slower, which will affect the normal eruption of teeth. At this time, you should consult a doctor in time for examination. There may also be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, give targeted treatment or treatment.