Table 2.

Univariate and stepwise logistic regression on possible risk factor for calculus

Factor	Univariate					Stepwise
	p value	OR	95% CI for OR		p value	OR	95% CI for OR
Gender
Male	< 0.001	1.26	1.23	1.29	< 0.001	1.26	1.22	1.30
Femalea
Age	< 0.001				< 0.001
12		0.57	0.55	0.59	< 0.001	0.55	0.53	0.57
13		0.66	0.64	0.68	< 0.001	0.64	0.62	0.67
14		0.81	0.79	0.84	< 0.001	0.80	0.77	0.83
15a
Region	< 0.001				< 0.001
East		0.74	0.72	0.76	< 0.001	0.82	0.79	0.85
West		1.50	1.45	1.54	< 0.001	1.39	1.34	1.45
Centrala
Living place
Urban	0.001	0.96	0.94	0.98	.069	1.02	1.00	1.06
Rurala
Ethnic group
Han	< 0.001	0.66	0.64	0.69	.001	0.92	0.88	0.97
Minoritya
Family structure
One-child family	< 0.001	0.68	0.66	0.69	< 0.001	0.78	0.76	0.81
With siblingsa
Father education	< 0.001				.002
Middle school		1.86	1.78	1.94	.001	1.11	1.04	1.17
High school		1.40	1.35	1.45	.085	1.04	0.99	1.10
Universitya
Mother education	< 0.001				< 0.001
Middle school		1.90	1.82	1.98	< 0.001	1.21	1.14	1.28
High school		1.39	1.34	1.44	.001	1.09	1.04	1.15
Universitya
Brush teeth
Yes	< 0.001	0.61	0.58	0.63	< 0.001	0.69	0.66	0.73
Noa
Dental floss
Yes	< 0.001	0.67	0.64	0.69	< 0.001	0.78	0.75	0.82
Noa
Smoking
Yes	< 0.001	1.59	1.51	1.68	.009	1.08	1.02	1.15
Noa
Oral health knowledge					< 0.001
0–3		1.25	1.21	1.29	< 0.001	1.10	1.06	1.14
4–5		1.24	1.20	1.27	< 0.001	1.13	1.09	1.16
6–8a
Oral health attitude
Negative	0.001	1.04	1.02	1.07
Positivea
Constant					< 0.001	3.30

^aReference category