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  • Title: [Timing of permanent tooth emergence and its association with physical growth among children aged from four to seven years in nine cities of China].
    Author: Zhang YQ, Li H, Wu HH, Zong XN.
    Journal: Zhonghua Er Ke Za Zhi; 2020 Mar 02; 58(3):206-212. PubMed ID: 32135592.
    Abstract:
    Objective: To investigate the timing of permanent tooth emergence and its association with physical growth among children aged 4-7 years in 9 cities of China, and to analyze the trend of permanent teeth development. Methods: According to a stratified cluster sampling design, a cross-sectional survey on the timing of permanent tooth emergence children aged 4-7 years was carried out in 9 cities (Beijing, Harbin and Xi'an in northern China; Shanghai, Nanjing and Wuhan in central China; Guangzhou, Fuzhou and Kunming in southern China) from June to October in 2015. A total of 37 973 children (19 035 boys and 18 938 girls) were recruited and were divided into different age groups (4.0-<4.5, 4.5-5.0, 5.0-5.5 and 6.0-<7.0 years of age). The situation of the exfoliation of primary teeth and the eruption of permanent teeth were investigated. Height and weight were measured using the standardized methods. Z-scores of physical growth indicators were calculated using the growth standards for Chinese children in 2009. Probit regression analysis was used to determine the median and percentile age of transition from deciduous to permanent teeth. Chi-square test was used for comparison of categorical data and t test was used for comparison of measurement data between boys and girls, urban and suburban as well as among different ages and regions. Meanwhile, the data from the national survey on physical growth and development of children under 7 years of age in 9 cities of China in 1995 were used to analyze the trends of the permanent teeth development. Results: The rate of transition from deciduous to permanent teeth in 37 973 children aged 4-7 years was higher with age, which was 0.6% (42/7 568) in 4.0-<4.5 years of age group, 30.3% (2 295/7 583) in 5.5-<6.0 years of age group, and 74.5% (5 680/7 627) in 6.0-<7.0 years of age group. The rates of transition from deciduous to permanent teeth in boys were all lower than those of girls except for children aged 4.0-<4.5 years (all P<0.01). The rate of transition from deciduous to permanent teeth in urban children was higher than that in suburban children for older than 5.5-6.0 years of age group in boys and older than 4.5-5.0 years of age group in girls, which was 74.2% (1 427/1 924) in urban boys aged 6.0-<7.0 years and 69.2% (1 305/1 885) in suburban boys aged 6.0-<7.0 years (χ(2)=11.446, P<0.01). The age of transition from deciduous to permanent teeth was 6.00 (95%CI: 5.98-6.01) years and the range of the 3-97 percentile was 4.88-7.11 years of age. The median permanent tooth emergence age of girls was lower than that of boys (5.94 vs. 6.06 years) and the median age of urban children was lower than that of suburban children (5.94 vs. 6.05 years). The median permanent tooth emergence age of southern Chinese children (6.05 years) was higher than that of northern (5.97 years) and central Chinese children (5.97 years). The weight for age Z-scores (WAZ), height for age Z-scores (HAZ) and body mass index for age Z-scores (BMIZ) of children with transition from deciduous to permanent teeth (0.35±1.17, 0.32±1.00, 0.23±1.16) were significantly higher than those of children without transition from deciduous to permanent teeth (0.03±1.13, 0.03±1.02, 0.04±1.13, t=20.81,21.67,12.09, all P<0.05). In comparison with the data in 1995, data in 2015 showed that the rate of transition from deciduous to permanent teeth was higher, for example, the rate of urban boys aged 6.0-<7.0 years group was 63.8% (1 146/1 796) in 1995, and increased to 74.2% (1 427/1 924) in 2015 (χ(2)=46.748, P<0.01). The median permanent tooth emergence age decreased by 0.24 years in 2015 as compared with that in 1995. Conclusions: The development of permanent teeth is earlier in girls than in boys, earlier in urban children than in suburban children and slightly delay in southern children than in central and northern Chinese children. In addition, the development of permanent teeth, which is related to the physical growth, slightly accelerate in China during the past 20 years. 目的： 探讨中国9个城市（简称九市）4~7岁儿童乳恒牙替换及其与体格生长的关系，分析恒牙发育长期变化趋势。 方法： 采用分层整群抽样的方法，以4~7岁儿童为调查对象，于2015年6—10月在北京、哈尔滨、西安（北片），上海、南京、武汉（中片），广州、福州、昆明（南片）九市进行横断面调查，共37 973名儿童，其中男19 035名，女18 938名。6岁以下每6个月为1组，6~<7岁1岁为1组。现场检查乳牙脱落、恒牙萌出情况，测量身高、体重等，并依据2009年中国儿童生长标准计算体格指标Z分值。采用Probit概率单位回归方法计算换牙年龄。不同性别、地区、年龄分组组间比较采用χ(2)检验或t检验。并利用1995年中国九市儿童体格发育调查中乳恒牙替换相关数据，分析恒牙发育的长期变化趋势。 结果： 九市37 973名儿童随着年龄增长换牙率逐渐增加，从4.0~<4.5岁的0.6%（42/7 568）增长至5.5~<6.0岁的30.3%（2 295/7 583），6.0~<7.0岁达到74.5%（5 680/7 627）。除4.0~4.5岁组外，无论城郊男童换牙率均低于女童（P均<0.05）；城区换牙率（男5.5~<6.0岁、女4.5~<5.0岁组之后）略高于郊区，如6.0~<7.0岁组男童城郊分别为74.2%（1 427/1 924）、69.2%（1 305/1 885）（χ(2)=11.446，P<0.01）。九市儿童换牙年龄为6.00（95%CI: 5.98~6.01）岁。换牙年龄的第3~97百分位变化范围为4.88~7.11岁。女童中位换牙年龄（5.94岁）早于男童（6.06岁）；城区（5.94岁）早于郊区（6.05岁）；北片（5.97岁）、中片地区（5.97岁）略早于南片地区（6.05岁）。已换牙儿童体重、身高、体质指数Z分值均高于未换牙儿童（0.35±1.17比0.03±1.13、0.32±1.00比0.03±1.02、0.23±1.16比0.04±1.13，t=20.81、21.67、12.09，P均<0.05）。与1995年相比，2015年5.0岁以后儿童换牙率明显提高，如城区男童6.0~<7.0岁组1995年为63.8%（1 146/1 796），2015年提高至74.2%（1 427/1 924）（χ(2)=46.748，P<0.01）；中位换牙年龄2015年较1995年提前0.24岁。 结论： 九市4~7岁儿童换牙年龄女童早于男童，城区早于郊区，北、中片早于南片地区。换牙早晚与体格生长水平有关。近20年换牙年龄存在小幅提前趋势。.
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