Table 8 Logistic regression analyses of odds for tooth wear among Central China adolescents

 Never

1

1

 Rarely

1.2

0.811

 Sometimes

1.7

1.070

 Often

2.5

1.415

 Never/rarely

1

1

 1–2 times weekly

0.7

0.441

 3–4 times weekly

0.4

0.280

  > 5 times weekly

0.4

0.205

 Never

1

1

 Rarely

1.4

0.915

 Sometimes

2.2

0.947

 Often

11.1

1.209

 Never

1

1

 Rarely

1.8

1.223

 Sometimes

1.1

0.558

 Often

1.0

0.298

 Both

1

1

 Left

1.6

0.992

 Right

2.2

1.289

Frequency of brushing

 Twice or more daily

1

1

 Once or less daily

1.5

1.012

Duration of brushing

  > 2 min

1

1

  ≤ 2 min

1.5

1.039