pediatrics
Physical Growth of Infants and Children
Tooth Eruption
Tooth eruption is variable (see table Tooth Eruption Times ), primarily because of genetic factors. On average, normal infants should have 6 teeth by 12 months, 12 teeth by 18 months, 16 teeth by 2 years, and all 20 teeth by 2½ years; deciduous teeth are replaced by permanent teeth between the ages of 5 years and 13 years. Eruption of deciduous teeth is similar in both sexes; permanent teeth tend to appear earlier in girls. Symptoms associated with tooth eruption are called Tooth eruption may be delayed by familial patterns or by conditions such as Hypophosphatemic Rickets , Teeth Teeth Number Number Age at Eruption* Age at Eruption* Deciduous (20 total) Deciduous (20 total) Lower central incisors 2 5–9 months Upper central incisors 2 8–12 months Upper lateral incisors 2 10–12 months Lower lateral incisors 2 12–15 months 1st molars† 4 10–16 months Canines 4 16–20 months 2nd molars† 4 20–30 months Permanent (32 total) Permanent (32 total) 1st molars† 4 5–7 years Incisors 8 6–8 years Bicuspids 8 9–12 years Canines 4 10–13 years 2nd molars† 4 11–13 years 3rd molars† 4 17–25 years * Varies greatly. † Molars are numbered from the front to the back of the mouth (see figure Identifying the Teeth ). The numbering system shown is the one most commonly used in the United States. 