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The Effect of Cooling Times on the Bonding Between Porcelain and Metal Alloys Fabricated by Different Techniques: In Vitro Study

Aim: The aim of this study was to evaluate the effect of different cooling times on shear bond strength between cobalt–chromium metal frameworks fabricated by different techniques and veneering porcelain. Materials and Methods: One hundred twenty cobalt–chromium metal ceramic samples were obtained by three different techniques (casting, milling, and laser sintering). During the porcelain firing, fast and slow cooling protocols were applied. Ten specimens from each group were determined for all groups. The shear bond strength of the metal ceramic samples was measured by a universal testing machine with a constant crosshead speed of 0.5 mm/min. One sample from each group was evaluated by the scanning electron microscopy analysis in terms of surface change and fracture morphology. Variance analysis and Tukey test were used to analyze statistically significant differences between groups. Results: It was seen that the difference between the bond strengths of the metal frameworks obtained by different techniques was statistically significant (P < .05). All groups except for difference between the bond strengths of all the frameworks metal groups with G-Ceram porcelain were statistically significant (P < .05). The best bond strengths that were statistically significant were fast cooling G-Ceram (19.65 ± 2.65 MPa) with metal frameworks fabricated by laser sintering, fast cooling with metal framework fabricated by milling Noritake (19.17 ± 2.91 MPa), and the metal framework fabricated by casting was found to be slow cooling Noritake (12.99 ± 2.08 MPa) were seen. Conclusion: The porcelain cooling times had significant effect on the shear bond strength of porcelain to casting, milling and laser sintering alloys.