The bond strength of laser-sintered dental alloy to porcelain

Even though base metal dental alloys are less expensive than traditional noble alloys, their use is limited because of difficulties experienced during casting and laboratory processing. A newly developed system for laser-sintering base metals might be a promising technique for manufacturing dental crowns. Objective: To compare shear bond strengths of cast Ni-Cr (Wiron 99, Bego, Germany) and Co-Cr (WBC 9581, Bego) alloys and the laser-sintered Co-Cr alloy. Methods: Cast bar specimens of both alloys were prepared using a broken-arm centrifugal casting machine. Laser-sintered specimens were prepared from the Co-Cr alloy (PM 100, Phenix^TM Systems, Clermont-Ferrand, France). Opaque and body porcelain (VMK 95, Vita Zahnfabrik, Germany) layers were applied on the alloy specimens (N = 10 for each group). The metal-ceramic specimens were loaded in shear using a universal testing machine and crosshead speed of 0.50 mm/min until fracture occurred. ANOVA followed by the Tukey HSD multiple comparison test (alpha = 0.05) was used for statistical analysis. Fractured specimens were observed with a stereomicroscope to classify the type of failure. Results: While the mean shear bond strength was highest for the cast Ni-Cr metal-ceramic specimens (81.6 ± 14.6 MPa), this bond strength was not significantly different (P > 0.05) from that for the cast Co-Cr metal-ceramic specimens (72.9 ±14.3 MPa) and laser-sintered Co-Cr metal-ceramic specimens (67.0 ± 14.9 MPa). All metal-ceramic specimens prepared from cast Ni-Cr and Co-Cr alloys exhibited a mixed mode of cohesive and adhesive failure, whereas 5 of the metal-ceramic specimens prepared from the laser-sintered Co-Cr alloy exhibited the mixed failure mode and 5 specimens exhibited cohesive failure in the porcelain. Conclusions: The new laser-sintering technique for Co-Cr alloy appears promising for dental applications, but additional studies on properties and biocompatibility of the laser-sintered alloy are needed before its acceptance into dental laboratory practice.