Influence of Silica-Lasing Method on the Bond Strength of Composite Resin to Ni-Cr Alloy: Comparison of CO2 and Nd:YAG Lasers

In this study silica-coated alumina particles (Cojet sand) were irradiated by CO2 laser and Nd:YAG laser with the intention of stabilization on the metal surface and bond strength to composite resin was evaluated.
Forty Ni-Cr cylindrical specimens were fabricated. The bonding surface of all specimens was airborne-particle abraded using 50 µm aluminum oxide particles. Specimens were divided into four groups that received the following surface treatments: 1-airborne-particle abrasion alone (A.A); 2- airborne-particle abrasion with Cojet sand; 3-metal surface coated with Cojet sand and irradiated by Nd:YAG laser (CJ-Lased-Nd:YAG); 4- metal surface coated with Cojet sand and irradiated by CO2 laser (CJ-Lased-CO2). Composite resin was applied on metal surfaces. Specimens were thermocycled and tested in shear mode in a universal testing machine. The mode of failure was determined, and two specimens in each group were examined by scanning electron microscopy and wavelength dispersive X-ray spectroscopy. The shear bond strength values were analyzed using ANOVA and Tukey’s tests (α=0.05).
Si-CO showed significantly higher shear bond strength in comparison to other groups (P0.05). In Si-CO group, the failure mode was mostly cohesive; but other groups showed adhesive failure in the metal-composite interface.
Silica-lasing with Cojet sand and irradiation of Nd:YAG or CO2 laser is not an effective method in improving metal-composite bond strength.