Table 1 The measurements of gingiva thickness (mm) before PAOO and 6-month after surgery

1 mm coronal to CEJ

0.86 ± 0.32

1.04 ± 0.39

0.19 ± 0.27

 < 0.001***

CEJ

1.17 ± 0.33

1.48 ± 0.46

0.31 ± 0.35

 < 0.001***

1 mm apical to CEJ

1.00 ± 0.29

1.28 ± 0.34

0.28 ± 0.33

 < 0.001***

2 mm apical to CEJ

0.91 ± 0.31

1.24 ± 0.35

0.33 ± 0.40

 < 0.001***

3 mm apical to CEJ

0.83 ± 0.26

1.12 ± 0.30

0.30 ± 0.30

 < 0.001***

4 mm apical to CEJ

0.75 ± 0.22

1.09 ± 0.31

0.33 ± 0.29

 < 0.001***

all sites

0.91 ± 0.32

1.21 ± 0.38

0.30 ± 0.33

 < 0.001***