Comparison of Ceramic Bonding to Cobalt-Chromium, Zirconia and Nickel-Chromium Alloys Fabricated Using of Various Techniques

The purpose of this study was to evaluate the characteristics of the ceramic bonding to cobalt-chromium (Co-Cr) alloys fabricated by casting, milling, and additive manufacturing, compared with zirconia and nickel-chromium. One hundred specimens (N = 100), prepared with the dimensions of 25 × 3 × 0.5 mm³, were assigned to five groups (n = 20): presintered milled Co-Cr (Group M), additively manufactured Co-Cr (Group SLM), cast Co-Cr (Group C), presintered zirconia (Group Zi), and cast Ni-Cr (Group Ni). The bar specimens were prepared to receive porcelain on their central area (8 × 3 mm²) of one side of each alloy strip. Only half of the specimens from each group were exposed to thermocycling (5°C-55°C for 5000 times). All specimens were placed in a bending device. Specimen surface morphology was examined by scanning electron microscopy. The bonding values between materials and the aging treatment effect groups were compared with two-way ANOVA. Variances were compared using the Levene test, the Bonferroni adjustment was used for multiple pairwise comparisons. The shape (m) and scale (σ₀) parameters of the two-parameter Weibull distribution values were calculated. Thermocycling did not affect the results of all the groups tested (p = 0.237). Statistical difference was found between the Co-Cr groups, and between groups Ni and Zi when compared to groups C and SLM (p < 0.001). Ni had the lowest adhesion values and cast Co-Cr the highest. A statistical difference was found between the three Co-Cr groups (p < 0.001), with the highest ceramic adhesion found in Group C and the lowest found in Group M. All specimens from Groups M, C, and Ni showed adhesive failures, whereas mixed failures were observed in Groups Zi and SLM. The fit of the maximum-likelihood line was a poor fit in the distribution of the aged SLM group (p < 0.010). Ceramic adhesion and failure types varied with the alloy choice and the manufacturing technique.