Table 2. Means and standard deviations of shear bond strengths in the studied groups (in MPa).
| Groups | N | Mean (MPa) | Std. Deviation | Min (MPa) | Max (MPa) |
| 1 | 15 | 20.22 a | 5.12 | 11.96 | 31.68 |
| 2 | 15 | 32.29 b | 5.42 | 25.39 | 44.09 |
| 3 | 15 | 29.14 b | 3.43 | 22.13 | 35.47 |
| 4 | 15 | 35.51 b | 4.41 | 25.49 | 44.56 |
| 5 | 15 | 33.77 b | 4.67 | 26.63 | 42.22 |
| 6 | 15 | 27.79 b | 5.70 | 18.37 | 37.88 |
Group 1: control; group 2: air abrasion; group 3: Er:YAG laser; group 4::diamond bur + phosphoric acid; group 5: HF acid; group 6: bulk. Different letters in a column indicate the statistically significant differences at α=0.001 between the two groups.