Development of primary teeth among infants and toddlers in nine cities of China in 2015 / 中华儿科杂志

ABSTRACT

Objective@#To investigate the status of the development of primary teeth and to identify the development patterns among infants and toddlers in nine cities of China in 2015.@*Methods@#Healthy children aged 1-<36 months were investigated by across-sectional survey and retrospective studies, which was carried out in 9 cities (Beijing, Harbin and Xi′an in northern China; Shanghai, Nanjing and Wuhan in central China; and Guangzhou, Fuzhou and Kunming in southern China) from June to October in 2015. Subjects (n=103 995) were divided into 14 age groups (1-<2, 2-<3, 3-<4, 4-<5, 5-<6, 6-<8, 8-<10, 10-<12, 12-<15, 15-<18, 18-<21, 21-<24, 24-<30, 30-<36 months). There were 150-200 boys and girls respectively in each group of urban and suburb areas in each city. The eruption status and the number of primary teeth were examined by the trained child health care physician or pediatrician on the spot. The timing of primary teeth eruption of children was retrospectively surveyed using a questionnaire. The prevalence of primary teeth was calculated and χ2 test was used for comparison of categorical data. Probit regression analysis was used to determine the median and percentile age of eruption of primary teeth.@*Results@#Totally 103 995 children aged 1-<36 months were investigated. There were 52 346 children in urban areas (boys 26 228, girls 26 118) and 51 649 children in suburb areas (boys 25 912, girls 25 737). The eruption rate of primary teeth in children under 2 years became higher with age and the difference among each age group was statistically significant (χ2=85 913.868, P<0.01), which was 0.3% (22/7 450) in 3-<4 months group, 43.0% (3 227/7 503) in 6-<8 months group and 99.9% (7 441/7 446) in 15-<18 months group. The eruption age of primary teeth was 6.6 months (95%CI 6.5-6.7 months), and the range of the 3rd to 97th percentile was 4.1-10.6 months. The eruption ages of primary teeth in urban and suburb areas children were 6.6 months (95%CI 6.5-6.7 months) and 6.6 months (95%CI 6.5-6.7 months) respectively. The eruption age of primary teeth was earlier in boys (6.4 months, 95%CI 6.3-6.5 months) than that in girls (6.7 months, 95%CI 6.6-6.8 months). The median eruption age of primary teeth was earlier in northern China (6.2 months) than that in central (6.7 months) and southern China (6.9 months). The eruption rate of primary teeth became higher with age, showing that the median number of primary teeth was 2 in 8-<10 months group, 8 in 12-<15 months group and 20 in 30-<36 months group.@*Conclusions@#The timing of eruption of primary teeth was similar between urban and suburb areas children and that of the boys was slightly earlier than that of the girls. There were slight differences among different regions in the eruption timing of primary teeth. The range of the 3rd to 97th percentile in the eruption age of primary teeth was 4.1-10.6 months and the number of primary teeth followed the regular development pattern with age.