Table 3.

Changes of prevalence of primary teeth eruption in different age groups. n refer to the number of children whose primary teeth had erupted, % refer to the prevalence of primary teeth eruption in the age group.

Age group	1995		2005		2015		P value
	n	%	n	%	n	%
1 m ~	0	0.0	0	0.0	0	0.0	–
2 m ~	0	0.0	0	0.0	0	0.0	–
3 m ~	12	0.2	12	0.2	21	0.3	0.145
4 m ~	182	2.6	158	2.5	197	2.7	0.557
5 m ~	834	11.8	753	12.1	979	13.6	0.001
6 m ~	2932	40.9	2662	42.1	3227	43.0	0.011
8 m ~	5752	80.5	5081	80.5	6144	81.9	0.036
10 m ~	6776	95.1	5990	96.2	7204	96.3	0.000
12 m ~	7109	99.4	6246	99.4	7478	99.5	0.905
15 m ~	7197	100.0	6298	100.0	7441	99.9	–
18 m ~	7200	100.0	6241	100.0	7514	100.0	–
21 ~  < 24 m	7200	100.0	6211	100.0	7355	99.9	–