Comparison of shear bond strength and interfacial fracture testing methodologies for quantifying adhesion of porcelain to titanium

Purpose: This study compared the shear bond strength (SBS) and strain energy release rate (G-value (J/m2) or interfacial toughness) testing methodologies for measuring the adhesion between porcelain and commercially pure titanium (CP Ti) with a chromium interlayer. Materials and Methods: Shear specimens consisting of porcelain discs (6 mm in diameter x 4 mm thickness) fired onto CP Ti plates grade II (10 mm x 10 mm x 1 mm). Strain energy release rate (G) specimens consisting of rectangular specimens of CP Ti plates grade II (8 mm x 30 mm x 1.5 mm) veneered by porcelain with the same dimensions as the CP Ti plates. The specimens in each test were divided into seven groups according to the electroplating treatment; Gr 1 (control without electroplating, n = 10); Gr 2 (5% w/v chromium nitrate solution for 30 minutes, n = 10); Gr 3 (5% w/v chromium nitrate solution for 60 minutes, n = 10); Gr 4 (5% w/v chromium nitrate solution for 120 minutes, n = 10); Gr 5 (10% w/v chromium nitrate solution for 30 minutes, n = 10); and Gr 6 (10% w/v chromium nitrate solution for 60 minutes, n = 10) and Gr 7 (10% w/v chromium nitrate solution for 120 minutes, n = 10). Each group was further equally divided into two subgroups according to the type of porcelain used. Two titanium-porcelains (Vita Titankeramik and Triceram) were applied to each subgroup (n = 5). The specimens were tested in shear and four point flexure in a universal testing machine. Failure types were examined by SEM. Data were analyzed using ANOVA and a Tukey\'s multiple comparison test. Results: The values obtained from the shear test were more scattered and poorly correlated. More reliable and reproducible results were obtained with the strain energy release rate test. SEM images showed that the chromium interlayer enhanced the adhesion between porcelain and titanium. Conclusion: Adhesion between porcelain and CP Ti can be improved by use of chromium interlayer prior to porcelain firing. Strain energy release rate is a more preferable test for quantifying adhesion than shear bond strength tests. Keywords: Adhesion, Shear bond strength, Strain energy release rate, Porcelain, Titanium, Chromium, Electroplating, Metal-ceramic