A Cross-setional Survey On The Patterns Of Primary Teeth Eruption Of Children In Chongqing

Objective:This study aimed to obtain the patterns of primary teeth eruption by a cross-sectional survey in 0~40 months old children in Chongqing and to provide normal timetables of tooth eruption that are practical in general physical growth assessment.Methods:2581 of 0~40 months old healthy children were collected from Jan 2014 to Jan 2016. General information were recorded by primary child health care doctors, including age, gender, gestation age, birth weight, time and sequence of first primary tooth eruption, number of teeth and age of totally primary teeth emergence. SPSS version 22.0 was used to do data analysis.Results:(1)The median age for the first primary tooth eruption was 8months old [95%CI(2.7 12.7)], with the earliest time was 2 months old, the latest time was15 months old;The median age for 20 teeth emergence was 31 months old [95%CI(24.7 36.7)], with the earliest time was 23 months and the latest time was 35 months. The time of first tooth eruption was positively correlated with total teeth emergence(R=0.879, P < 0.05).Dental charts(number of tooth for age) of difference gender were obtained according to teeth eruption information.(2) The first primary tooth eruption was the incisor of mandible in 95.3% infants and was the incisor of maxilla in 4.6% infants, other position was rare.(3)During the period when teeth are actively emerging(number of teeth ≤16),the number of primary teeth might be calculated by formula: number of teeth=chronological age in months-age of first eruption in months+1. There was no statistical difference between the number of actual teeth and calculated by new formula(t=-2.957, P=0.00),the correlation coefficient was 0.972(P < 0.05).The number of actual teeth was different from calculated number according to old formula(number of teeth=chronological age in months-4 or 6), t=-10.705, P =0.00, although the correlation coefficient was 0.879(P<0.05).(4)Tooth generally developed later in males than in females(7.8±2.6 mos vs 7.5±2.46 mos,t=3.01, P =0.003).There was no difference on the time of first tooth eruption between preterm and term babies(7.8±2.33 mos vs 7.6±2.56 mos,t=0.50, P=0.61). And also birth weight had no effect on the time of eruption(P>0.05).Conclusion:Our survey obtains the general patterns of primary teeth eruption and dental charts in Chongqing. These charts provide normal and supplement datasets for evaluating child physical growth.