Bond Strength of Veneering Resin to Alloy Using Four Adhesives

Objectives: Several chemical bonding systems have been used in Prosthodontics to promote veneering composite resin adhesion to metal framework. The purpose of the present study was to evaluate the shear bond strength of a photocured composite (Sinfony) to a Ni-Cr alloy (Heraenium) using 4 alloy surface bonding agents. Materials and Methods: 48 wax disks were cast and embedded in acrylic resin. The discs were divided in two equal groups. In the first group (A) the alloy surface was sandblasted using 50mm Al2O3, while the specimens of the second group (B) were sandblasted with 250mm Al2O3. Each group was divided into four subgroups of 6 samples. On each subgroup the following bonding agents were used respectively: Metal Photo Primer (A1, B1), Metal Primer II (A2, B2), Link (A3, B3) and Tender Bonding (A4, B4). All specimens were thermocycled (5000 c, 5 and 55¨¬C) and subjected to shear test in a universal testing machine according to ISO 10774. Fracture values were statistically analysed using the two-way ANOVA. The debonded surfaces were observed under an optical microscope to determine failure mode. Results: A statistically significant difference was found between group A and group B (p<0,05) with higher shear bond strength for group A. The subgroup showing the highest bond strength was A2 (17.4±2.2 MPa). All tested subgroups showed statistical significant differences except for A1 with A4. The modes of failure which were observed in this study were a combination of adhesive and cohesive type. Conclusions: The appropriate alloy surface treatment can significantly improve the resin-alloy shear bond strength. Metal Primer II with 50 surface sandblasting exhibited the highest shear bond strength among all the tested materials.