The timing of teething in infants is related to the location of the teeth and varies individually. In general, the mandibular milk incisors begin to erupt in May and June, the mandibular milk lateral incisors and maxillary milk incisors around July, the maxillary milk lateral incisors in September, the mandibular first milk molar in December, the maxillary first milk molar in 14, the mandibular milk cusp in 16, the maxillary milk cusp in 18, the mandibular second milk molar in 20, and the maxillary second milk molar in 24. The eruption of milk teeth, in general, occurs earlier in the lower jaw than in the upper jaw, and the teeth of the same name are symmetrical from left to right, following the pattern of appearing at the same time, first up and then down.