Improving Fracture Resistance of 5Y-PSZ-Based Three-Unit Bridge Prostheses.

Purpose: To investigate the effect of BruxZir Steel treatment on the fracture resistance of zirconia threeunit bridges prepared using 5Y-PSZ-based zirconia blanks.

Materials and methods: Three-unit zirconia bridges were milled using CAD/CAM from homogeneous bisque zirconia blanks (5Y-PSZ-based) supplied by various manufacturers and sintered. Fracture resistance was analyzed with dynamic loading. For each zirconia blank, the fracture resistance of the sintered test restoration (cementation surface treated with BruxZir Steel) was compared to the sintered control restoration (untreated cementation surface). Finite element analysis (FEA) was used to analyze the stress distribution on the three-unit bridge under an axial load.

Results: The fracture resistance of the test restorations was significantly higher than that of the control restorations for all manufacturers considered in this study (P < .05). Furthermore, the restoration made of BruxZir Esthetic treated with BruxZir Steel had the highest fracture resistance compared to the other restorations. In addition, the three-unit bridge restorations prepared from 5Y-PSZ-based zirconia blanks exhibited differences in grain size and fracture toughness depending on the presence or absence of BruxZir Steel treatment. The locations of high stresses under FEA correlated well with the fracture locations in the corresponding experimental test. FEA also demonstrated the improved performance of the BruxZir Steel-treated sample compared to the control.

Conclusions: The fracture resistance of 5Y-PSZ-based BruxZir Steel-treated three-unit bridges was significantly higher (min = 30%, max = 198%) than the control.