At the beginning of the milk teeth, the milk arch is ovoid, the teeth are closely aligned, and there is generally no gap. As we grow older, the jawbone develops and grows, the size of the teeth remains the same, and an extensive gap gradually appears in the anterior part of the dentition. The appearance of gaps in the milk tooth arch is also closely related to the development of the permanent tooth germ, and the jawbone increases in size as the permanent tooth germ develops. Especially after the age of 5 years, the anterior teeth and the sixth molar start to grow and erupt, the jawbone grows rapidly, and the gap between the anterior teeth expands rapidly. This gap is conducive to the eruption and alignment of permanent teeth, but not necessarily a gap between the milk teeth, permanent teeth are normal, such as permanent teeth are too large, milk teeth, permanent teeth replacement can still appear crowded. On the contrary, sometimes there is no gap between the milk teeth, but the permanent teeth are not too large and the jawbone development is normal, and the teeth can be arranged normally after replacement. After the formation of the milk teeth, the milk teeth are constantly changing in growth and development. Generally, in the anterior region, there is a gap between the teeth due to growth and development at the age of 3 to 6 years, but there is no certain type of gap, which is generally called a growth gap. According to recent studies, there are also gaps that appear at the time of the milk teeth or there are always no gaps. Another phenomenon is the appearance of gaps in the proximal and distal centers of the maxillary milk cuspids, generally referred to as primate gaps. The child’s family should not be overly concerned as this is just a normal phenomenon that occurs during the transition period when the baby teeth become permanent. There is no need for too much intervention.