It is normal for babies to have upper teeth over lower teeth, but if the teeth are deeply overjetted, it is an abnormal condition and requires orthodontic treatment. In general, the upper teeth cover the lower teeth, the upper and lower teeth intersect each other, forming a close and extensive contact, the entire periodontal tissues as well as the teeth are subjected to uniform stress to withstand the occlusion. Normal teeth itself is the need for upper teeth to cover the lower teeth, generally under normal circumstances, there is 1/3 of the coverage, if the upper and lower teeth can be evenly contacted, there is a normal occlusal relationship, do not need special treatment. If the baby’s upper and lower teeth cover more than 1/3 of the surface, there is abnormal contact, wrapped too much or have a forward convexity, belongs to the deep overjet, is an abnormal situation, need to be corrected and treated. If your baby has deep overjet, you should go to a regular hospital for orthodontic treatment.