Objectives: Adjustment of metal alloy framework of the porcelain-fused-to-metal crown by soldering minor marginal deficiencies may sometimes be needed. The crown margins are affected by high stresses in function. Therefore, bonding of the luting cement to crown margin is of importance. The aim of this study was to compare shear bond strengths of four luting cements to casting metal alloy and soldering metal alloy. Methods: Flame cast non-precious metal alloy (Wirobond C, Bego) and flame soldered metal alloy (Wirobond Solder, Bego) samples were ground flat (grit 1200) followed by air-abrasion with 50 µm aluminum oxide at 250 kPa. Polycarboxylate cement Durelon (3M ESPE), composite resin cements Panavia F (Kuraray), RelyX Unicem Applicap and RelyX ARC (3M ESPE) stubs (diameter: 3.6mm, height 5mm) were applied and bonded to the alloy substrate surface (n=8/group). After setting or polymerization by light activation of the cement, the samples were stored in water at 37^oC for 1 week. Shear bond strength of cements to alloy was measured. Differences were analyzed using multivariate analysis of variance ANOVA (p<0.05). Fracture surfaces were analyzed with scanning electron microscope (JSM 5500, JEOL).  Results: Mean shear bond strengths (± SD) were:

ANOVA showed differences between luting cements (p<0.001) where no difference between the metal alloy substrates was found (p<0.05). It was observed on the micrographs that debondings from substrate surface were adhesional. Conclusion: It was concluded that different luting cements varied considerably with respect to their bond strengths. There were no difference between the cast metal alloy and soldering metal alloy substrate on the bond strength.

The study was financially supported by The Finnish National Technology Agency (TEKES) and CIMO Fellowship Grant.