The normal teething order of baby is that: 2 pairs of the lower central incisors come out first, the upper central incisors followed, and then the upper second incisors which close to central incisors come out, and the following is lower second incisors. These 8 baby tooth come out when baby is 1-year-old. After 1-year-old, 1 pairs of lower first deciduous molars come out, and 1 pairs of upper first deciduous molars followed. And then the following is cynodont which is between lower second incisor and first deciduous molar, and then the upper cynodont comes out. The last 2 pairs are the upper and lower second deciduous molars, totally 20 of baby tooth will be come out at about 2 or 2.5 years old.

If children teething too late or the order of teething reversed, that may be a manifestation of rickets. The severe infection or hypothyroidism will also cause late teething.