Microtensile Repair Bond Strength of a Composite After Accelerated Artificial Aging: Effect of the Air Abrasion, Bur, Er:YAG Laser, Two-Step Self-etch Bonding, and Universal Bonding Repair System: Repaired Bond Strength of Aged Composite

Introduction: Repair of old composite restorations is a conservative approach. This study sought to compare the effects of two adhesive systems on the bond strength of repaired composites prepared by three different surface treatments: erbium-doped yttrium aluminum garnet (Er:YAG) laser irradiation, air-abrasion, and bur preparation.Methods: Eight microhybrid (Polofil Supra, VOCO, Germany) composite resin blocks were fabricated. The blocks were aged and assigned to four groups as stated by the surface treatment: (I) air-abrasion (50 μ aluminum oxide particles), (II) diamond bur (fine grit), (III) Er:YAG laser (3 W output power, 300 mJ energy) and (IV) control. After surface treatment, the blocks were acid-etched and salinized. Each group was divided two subgroups, and the Clearfil SE Bond or All-Bond Universal was applied on their surface. Composite resin was bonded to the aged composites. The blocks were cut into eight samples, and the microtensile bond strength (MTBS) was measured.Results: The maximum MTBS was noted in the air-abrasion (25.1 + 6 MPa) group, followed by the Er:YAG laser (21.2 + 4.7 MPa). The mean MTBS in laser and air-abrasion groups was significantly higher than that in other groups (P < 0.05). The mean MTBS was not significantly different between the laser and air-abrasion groups (P > 0.05). Composite resin conditioning by All-Bond Universal in laser and air-abrasion groups yielded significantly higher MTBS than the Clearfil SE Bond (P < 0.05).Conclusion: All surface treatments created acceptable bond strength. The surface treatment of the aged composite by the Er:YAG laser or air-abrasion along with the application of silane and All-Bond Universal provide high bond strength