Table 2 Residual stain scores of the apically facing thread surfaces for the different instruments and the defects for the surgical approach (a) and non-surgical approach (b)

 Gracey curette

1.31 ± 0.42 A

1.41 ± 0.45 A

1.32 ± 0.38 A

1.00 (0.5)

1.50 (0.5)

1.25 (0.5)

 Ultrasound

1.48 ± 0.41 A

1.34 ± 0.36 A

3.09 ± 1.07 B

1.50 (0.5)

1.50 (0.5)

2.75 (1.5)

 Air powder abrasion

1.25 ± 0.39 A

1.34 ± 0.49 A

2.79 ± 1.18 B

1.00 (0.5)

1.00 (0.5)

2.75 (2.0)

 Gracey curette

1.38 ± 0.16 A

1.3 ± 0.15 A

1.1 ± 0.15 CE

1.5 (0.25)

1.25 (0.25)

1.0 (0.25)

 Ultrasound

1.4 ± 0.17 A

1.09 ± 0.17 C

1.09 ± 0.12 CE

1.5 (0.25)

1.0 (0.06)

1.0 (0.25)

 Air powder abrasion

2.82 ± 0.47 B

1.96 ± 0.55 D

2.7 ± 0.7 BF

2.75 (0.656)

1.81 (0.75)

2.5 (0.91)