Table 1 Characteristics of the participants (n = 1655)

 Sex

Boys

817

27

3.3

Girls

838

26

3.1

0.46

 Grade

Low (1st–3rd)

829

17

2.1

High (4th–6th)

826

36

4.4

0.01

 Skipping breakfast

No

1547

46

3.0

Yes

108

7

6.5

0.05

 Eating alone at dinner

No

1635

51

3.1

Yes

20

2

10.0

0.13

 Number of treated teeth

≤ 2

1021

25

2.4

≥ 3

634

28

4.4

0.02

Father’s BHPS

Not poor (2–7)

1527

47

3.0

Poor (0–1)

77

6

7.2

0.05

Mother’s BHPS

Not poor (2–7)

1583

51

3.1

Poor (0–1)

19

2

9.5

0.14

Father’s Internet and game use at home, h/day

< 2 h

1416

39

2.8

0.02

≥ 2 h

239

14

5.9

Mother’s Internet and game use at home, h/day

< 2 h

1566

49

3.1

≥ 2 h

89

4

4.5

0.32

Perceived family affluence

Affluent

447

7

1.6

Neither

794

26

3.3

No

414

20

4.8

0.03

Mother’s employment status

Full-time

672

22

3.3

Part-time

742

19

2.6

Unemployment

241

12

5.0

0.18

Number of after school activities

≥1

1330

33

2.5

0

325

20

6.2

0.001