A cross-sectional study on the association between vitamin D levels and caries in the permanent dentition of Korean children

Table 1 Characteristics of the subjects

Variables	Classification	N^a	%^b
Sex	Female	788	46.6
	Male	900	53.4
	Total	1688	100.0
Age (years)	10	531	31.1
	11	583	33.4
	12	574	35.4
	Total	1688	100.0
Household income	Low	375	24.9
	Middle	882	53.1
	High	414	22.0
	Total	1671	100.0
Frequency of tooth brushing (per day)	≤ 1	211	12.8
	2	969	58.1
	3	426	25.3
	≥ 4	73	3.8
	Total	1679	100.0
Vitamin D^c (two classification)	< 50 nmol	1038	61.7
	≥ 50 nmol	650	38.3
	Total	1688	100.0
Vitamin D^c (four classification)	< 25 nmol	66	4.4
	≤ 25 to < 50 nmol	972	57.3
	≤ 50 to < 75 nmol	588	35.0
	≥ 75 nmol	62	3.3
	Total	1688	100.0
Caries experience in permanent dentition	No	827	48.3
	Yes	861	51.7
	Total	1688	100.0
Permanent first molar caries experience	No	867	50.8
	Yes	821	49.2
	Total	1688	100.0