This study compared the microshear bond strength (µSBS) to end and side of enamel rod bonded by four adhesives including two total etch adhesives and two self-etch adhesives.

Crown segments of extracted human molars were cut mesiodistally. The outer buccal or lingual surface was used as specimens cutting the ends of enamel rods, and inner slabs used as specimens cutting the sides of enamel rods.

They were assigned to four groups by used adhesives: Group 1 (All-Bond 2), Group 2 (Single Bond), Group 3 (Tyrian SPE/One-Step Plus), Group 4 (Adper Prompt L-Pop). After each adhesive was applied to enamel surface, three composite cylinders were adhered to it of each specimen using Tygon tube. After storage in distilled water for 24 hours, the bonded specimens were subjected to µSBS testing with a crosshead speed of 1 mm/minute. The results of this study were as follows;

1. The µSBS of Group 2 (16.50 ± 2.31 _MPa) and Group 4 (15.83 ± 2.33 _MPa) to the end of enamel prism was significantly higher than that of Group 1 (11.93 ± 2.25 _MPa) and Group 3 (11.97 ± 2.05 _MPa) (p < 0.05).

2. The µSBS of Group 2 (13.43 ± 2.93 _MPa) to the side of enamel prism was significantly higher than that of Group 1 (8.64 ± 1.53 _MPa), Group 3 (9.69 ± 1.80 _MPa), and Group 4 (10.56 ± 1.75 _MPa) (p < 0.05).

3. The mean µSBS to the end of enamel rod was significantly higher than that to the side of enamel rod in all group (p < 0.05).