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Table 6 Independent t-tests comparing the clinical crown height for the normal wear and severe wear subsets measured by the clinical crown height for the combined four groups

From: Quantitative measures of gingival recession and the influence of gender, race, and attrition

Tooth class

Group

n

Mean

SD

t

p

U6

Normal wear

107

6.75

1.09

0.10

0.923

Severe wear

12

6.71

1.25

U5

Normal wear

110

7.21

1.00

2.29

0.023*

Severe wear

16

6.62

0.69

U4

Normal wear

109

8.20

0.94

3.21

0.002*

Severe wear

9

7.18

0.52

U3

Normal wear

110

10.11

1.13

3.68

0.000*

Severe wear

18

9.09

0.84

U2

Normal wear

106

8.89

1.00

3.16

0.002*

Severe wear

11

7.88

1.13

U1

Normal wear

97

10.41

1.12

3.13

0.002*

Severe wear

22

9.63

0.72

L6

Normal wear

78

6.78

0.92

2.31

0.023*

Severe wear

44

6.40

0.77

L5

Normal wear

104

7.50

0.84

3.56

0.001*

Severe wear

17

6.66

1.25

L4

Normal wear

107

8.37

0.83

3.52

0.001*

Severe wear

10

7.40

0.87

L3

Normal wear

103

10.00

1.28

4.14

0.000*

Severe wear

29

8.93

0.99

L2

Normal wear

102

8.42

1.02

3.04

0.003*

Severe wear

23

7.72

0.86

L1

Normal wear

97

8.41

1.01

4.65

0.000*

Severe wear

26

7.37

1.04

  1. *p < .05, comparing the clinical crown between the normal wear and severe wear subgroups and showing the significant differences for all tooth classes due to a decrease in the clinical crown height in the severe wear group—a false positive value
  2. Reprinted with permission from Eltink et al. [17, 27]