表 1.

腭中缝形态特点分期与牙龄频数分布表

Frequency distribution of MPS stage and dental age

MPS stage	Dental age of left lower second premolar									Dental age of left lower second molar
	B	C	D	E	F	G	H	Total		B	C	D	E	F	G	H	Total
MPS, midpalatal suture.
1	1	1	13	21	29	30	11	106		1	3	37	16	18	27	4	106
2	0	0	5	8	18	17	13	61		0	0	11	15	8	18	9	61
3	0	0	1	5	46	124	109	285		0	0	6	12	42	136	89	285
4s1	0	0	0	0	6	62	195	263		0	0	0	2	8	65	188	263
4s2	0	0	0	0	2	14	261	277		0	0	0	1	0	18	258	277
5	0	0	0	0	1	2	81	84		0	0	0	0	0	4	80	84
Total	1	1	19	34	102	249	670	1 076		1	3	54	46	76	268	628	1 076