ABSTRACT
A strong and stable bond between veneering materials and metal framework considerably promotes the aesthetic appearance and clinical longevity of a resin type restoration. Various adhesive metal primers have also been studied to enhance the bond strength of the composite resins to different metal surfaces. The purpose of the present study was to evaluate the shear bond strength of one laboratory composite resin bonded to a Ni-Cr alloy by means of two different methods. In this study, 24 wax disks were cast and divided into two equal groups. In the first group, a metal primer was applied to the casting surface, while an opaque porcelain material was used for the second group. After application of the veneering composite resin to the treated surfaces, the specimens were stored in a 37°C water bath for 15 days. At the end of this period, all the specimens were subjected to 1200 thermal cycles [5°C and 55 °C] and then tested for shear strength in a universal testing machine at a crosshead speed of 0.5 mm/min. Fractured specimens were examined, using a scanning electron microscope. The opaque porcelain group demonstrated higher bond strength [17.55 +/- 3.33 Mpa] in comparison to the metal primed surface [15 +/- 4.25 Mpa]. However, no statistically significant difference was found between the specimens treated with metal primer and those treated with opaque porcelain. The two alloy surface treatments exhibited mixed failures, however. While the nature of failure for opaque porcelain was predominately cohesive, the failure for the metal primed group was adhesive. It can be concluded that both techniques have potential to significantly improve resin-alloy shear bond strength