Table 1 Test groups and surface treatments

Group A

Etched with 4% hydrofluoric acid gel for 30 s, rinsed for 1 m, air dried for 10 s + and sandblasted with air-abrasion (110 µm Al₂O₃) for 20 s, with 4 bar pressure, distance of 10 mm

Group B

Er:YAG laser applied energy level was 150 mJ with 10-Hz frequency for 45 s, pulse width 300 μS + and sandblasted with air-abrasion (110 µm Al₂O₃) for 20 s, with 4 bar pressure, distance of 10 mm

Group C

Er:YAG laser applied energy level was 150 mJ with 10-Hz frequency for 45 s., pulse width 300 μS + and etched with 4% hydrofluoric acid gel for 30 s, rinsed for 1 m, air dried for 10 s