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 χ(2) 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 (χ(2)=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.
目的： 调查分析2015年中国9个城市婴幼儿乳牙发育的现状及其规律。 方法： 采用横断面调查与回顾性研究相结合的方法，于2015年6至10月在北部地区的北京、哈尔滨、西安，中部地区的上海、南京、武汉以及南部地区的广州、福州、昆明9个城市对103 995名1~<36月龄婴幼儿进行调查，6月龄以内每个月龄1组，6~12月龄每2个月龄1组，12~24月龄每3个月龄1组，24~36月龄每6个月龄1组，每市每年龄组城区、郊区、男、女各150~200名。婴幼儿乳牙萌出状况和萌出数量通过现场测查获得，同时对已出牙婴幼儿的乳牙开始萌出年龄进行问卷调查。计算各年龄组乳牙萌出率，组间比较采用χ(2)检验，采用Probit概率单位回归方法计算乳牙萌出的百分位年龄。 结果： 9个城市共调查103 995名婴幼儿，城区52 346名（男26 228名、女26 118名），郊区51 649名（男25 912名、女25 737名）。2岁以内婴幼儿乳牙萌出率随年龄增长逐渐增加，各年龄组差异有统计学意义（χ(2)=85 913.868，P<0.01），从3~<4月龄0.3%（22/7 450）、6~<8月龄43.0%（3 227/7 503），至15~<18月龄99.9%（7 441/7 446）。乳牙萌出年龄为6.6（95%CI：6.5~6.7）月龄，第3~97百分位区间为4.1~10.6月龄。城区、郊区婴幼儿乳牙萌出年龄均为6.6（95%CI：6.5~6.7）月龄；男童略早于女童，分别为6.4（95%CI：6.3~6.5）月龄、6.7（95%CI：6.6~6.8）月龄；北部地区乳牙中位萌出年龄（6.2月龄）略早于中部（6.7月龄）和南部地区（6.9月龄）。乳牙萌出数量随着年龄增长而逐渐增多，8~<10月龄组中位数为2颗，12~<15月龄组达到8颗，30~<36月龄组基本出齐20颗。 结论： 乳牙萌出年龄无城郊差异，男童略早于女童，存在小幅地区差异；九市婴幼儿乳牙萌出年龄的第3~97百分位区间为4.1~10.6月龄，萌出数量随年龄增长呈现规律变化。.
Keywords: Child; Growth; Infant; Tooth, deciduous.