Table 2 Comparison of categorical outcome variables in relation to the smoking type over 4 time points of study follow-up period

Gingival color

Cig.

F (%)

E

F (%)

None

F (%)

Cig.

F (%)

E

F (%)

None

F (%)

Cig.

F (%)

E

F (%)

None

F (%)

Cig.

F (%)

E

F (%)

None

F (%)

Red

20 (100)

20 (100)

20 (100)

2 (10)

9 (45)

0

4 (21)

7 (37)

2 (10)

5 (25)

9 (45)

2 (10)

Pink

18 (90)

11 (55)

20 (100)

15 (79)

12 (63)

18 (90)

15 (75)

11 (55)

18 (90)

χ²-value; p-value

–

–

–

6.307; 0.043*

Gingival consistency

14 (70)

10 (50)

17 (85)

2 (10)

9 (45)

0

4 (21.1)

9 (47.4)

2 (10)

5 (25)

10 (50)

2 (10)

Edematous firm

6 (30)

10 (50)

3 (15)

18 (90)

11 (55)

20 (100)

15 (78.9)

10 (52.6)

18 (90)

15 (75)

10 (50)

18 (90)

χ²-value; p-value

5.70; 0.058

14.92; 0.001

7.06; 0.029

8.04; 0.018*

Plaque index

0

9 (45)

7 (35)

0

16 (80)

13 (65)

20 (100)

15 (79)

13 (68.4)

18 (95)

16 (80)

13 (65)

19 (95)

1

11 (55)

13 (65)

20 (100)

4(20)

7 (35)

0

4 (21)

6 (31.6)

1 (5)

4 (20)

7 (35)

1 (5)

χ²-value; p-value

11.42; 0.003

8.24; 0.016

–

–

BOP

Yes

13 (72)

13 (76.5)

16 (88.9)

3 (15)

2 (10)

0

5 (26.3)

9 (47.4)

2 (10.5)

6 (30)

10 (50)

2 (10)

No

5 (28)

4 (23.5)

2 (11.1)

17 (85)

18 (90)

20 (100)

14 (73.7)

10 (52.6)

17 (89.5)

14 (70)

10 (50)

18 (90)

χ²-value; p-value

1.64; 0.441

–

–

7.62; 0.022*