| Objective: To investigate the patterns of primary teeth eruption in full-term healthy children in Chongqing and to verify the formula of the number of primary teeth and the age of children.Methods: Questionnaire survey,physical examination and telephone follow-up were performed to collect the general information(including gender,gestational age,birth date,birth weight and birth height)and the information(including age,number and location of tooth eruption)of primary teeth eruption of 76 children aged 0~4 months without tooth eruption.The mean ± standard deviation was used to describe the eruption age of primary teeth.Morover,independent sample t test,paired sample t test,single sample t test,variance analysis and spearman correlation were also involved in data analysis.Results: 1.Totally 76 children were involved in this survey,including47 boys and 29 girls.The birth weight was less than 2500 g in 2 cases,2500~4000g in 68 cases,and > 4000 g in 6 cases.The average age ofchildren was(13.67±1.35)months at the end of follow-up and(2.20±0.77)months at the beginning of enrollment.At the end of follow-up,there were 70 cases with 8 primary teeth and 6 cases with more than 8 primary teeth.2.The ages and sequence of primary teeth eruption in children were as follows:(7.34±1.48)months for mandibular central incisor,(9.25±1.35)months for maxillary central incisor,(10.93±1.54)months for maxillary lateral incisor,(12.63±1.73)months for mandibular lateral incisor.3.The interval of eruption time between central incisors and lateral incisors was3.4 months(95% CI: 3.2~3.6),while that between lateral incisors and first deciduous molars was 2.3 months(95% CI: 1.0~3.7).4.There was no significant gender difference in the eruption time of primary teeth(P>0.05).5.The time of the first primary tooth eruption was negatively correlated with birth weight(r=-0.313,P<0.05),but not with birth height(P>0.05).There was no significant difference in the eruption age of first primary tooth among different birth weight groups(P>0.05).6.The number of actual teeth of children aged 9 months,10 months,11 months and 12 months was different from calculated number according to the old formula(number of primary teeth=chronological age in months-4 or 6)(P=0.000).But there was no statistical difference between the number of actual teeth and calculated by the new formula(number of primary teeth=chronological age in months-age of first eruption in months+1)(P>0.05).Conclusion: 1.The mean ages of primary teeth eruption of full-termhealthy children in Chongqing are as follows: 7.34 months for mandibular central incisor,9.25 months for maxillary central incisor,10.93 months for maxillary lateral incisor,12.63 months for mandibular lateral incisor.2.The interval of eruption time between central incisors and lateral incisors is3.4 months on average,while that between lateral incisors and first deciduous molars is 2.3 months on average.3.The new formula(number of primary teeth=chronological age in months-age of first eruption in months+1)can estimate the number of primary teeth of children more accurately than the old one(number of primary teeth=chronological age in months-4 or 6). |
