Table 3.

The results of the multivariate logistic regression analysis

Variables	All		Urban		Rural		P interaction
	OR (95% CI)	P	OR (95% CI)	P	OR (95% CI)	P
Age (year)
12	Ref.
13	1.030 (0.881, 1.201)	0.704	1.057 (0.854, 1.308)	0.609	1.011 (0.808, 1.265)	0.924	0.777
14	1.216 (1.044, 1.415)	0.012	1.075 (0.869, 1.329)	0.507	1.419 (1.139, 1.768)	0.002	0.075
15	0.699 (0.596, 0.821)	< 0.001	0.755 (0.605, 0.941)	0.013	0.646 (0.510, 0.818)	< 0.001	0.345
Gender
Male	Ref.
Female	0.968 (0.866, 1.081)	0.559	0.941 (0.806, 1.099)	0.443	0.986 (0.840, 1.157)	0.863	0.681
Only child
No	Ref.
Yes	1.236 (1.072, 1.425)	0.004	1.228 (1.037, 1.453)	0.017	1.333 (0.950, 1.870)	0.096	0.671
Father’s Education level
≤ 9 years	Ref.
10–12 years	0.897 (0.768, 1.047)	0.167	0.902 (0.732, 1.111)	0.331	0.859 (0.678, 1.087)	0.206	0.762
≥ 13 years	0.926 (0.726, 1.181)	0.537	0.896 (0.670, 1.199)	0.461	1.015 (0.630, 1.635)	0.950	0.662
Unclear	0.959 (0.757, 1.216)	0.729	0.797 (0.565, 1.123)	0.194	1.182 (0.843, 1.656)	0.332	0.108
Mother’s Education level
≤ 9 years	Ref.
10–12 years	1.022 (0.859, 1.216)	0.807	0.994 (0.794, 1.243)	0.956	1.053 (0.795, 1.396)	0.718	0.751
≥ 13 years	0.902 (0.693, 1.173)	0.440	0.868 (0.644, 1.172)	0.356	1.199 (0.643, 2.235)	0.567	0.360
Unclear	0.993 (0.785, 1.257)	0.956	1.002 (0.709, 1.414)	0.993	0.993 (0.715, 1.379)	0.968	0.973
Daily frequency of tooth brushing
< 2 times/d	Ref.
≥ 2 times/d	0.915 (0.817, 1.025)	0.124	0.871 (0.745, 1.018)	0.083	0.983 (0.831, 1.163)	0.844	0.301
Dental floss
Non daily	Ref.
Daily	0.936 (0.779, 1.125)	0.484	0.817 (0.648, 1.031)	0.088	1.246 (0.920, 1.689)	0.155	0.031
Regular annual dental check-up
No	Ref.
Yes	0.870 (0.763, 0.993)	0.038	0.826 (0.691, 0.986)	0.035	0.942 (0.774, 1.147)	0.552	0.328
Calculus level
≤ 10%	Ref.
> 10% and ≤ 30%	5.490 (4.882, 6.175)	< 0.001	4.556 (3.869, 5.365)	< 0.001	6.765 (5.699, 8.031)	< 0.001	0.001
> 30%	15.803 (12.552, 19.896)	< 0.001	15.413 (11.094, 21.413)	< 0.001	16.852 (12.161, 23.354)	< 0.001	0.706