5 years old children need to fill tooth decay, most of the teeth in the mouth of 5 years old children are milk teeth, individual children with early development will erupt the first permanent molar and mandibular milk incisor, the enamel of milk teeth is thin, caries progresses faster, if not timely repair will develop into pulpitis, causing severe pain, affect the chewing function and cause insufficient nutrition intake of the whole body. When pulpitis progresses to periapical inflammation, it will affect the permanent tooth germ below the baby teeth, resulting in late eruption of permanent teeth and even misalignment of teeth and other misshapen jaws. Due to the high salivary secretion in the mouth of the child, it is best to use a rubber barrier to isolate the wetness during the repair.