Effects of microstructural change of zirconia surface on tensile bond strength with resin cement / 대한치과재료학회지

ABSTRACT

This study was performed to evaluate the effects of microstructural change of zirconia surface on tensile bond strength with resin cement. The zirconia partially sintered block was cut into a size of 18 × 18 × 7 mm, and then the Zirface slurry (DMAX, Daegu, Korea) containing 15% and 30% zirconia was applied and followed by sintering at 1530 ℃ for 2 hours. Resin cement (PermaCem 2.0, DMG, Hamburg, Germany) was applied on zirconia specimen and polymerized to prepare an 18 × 18 × 14 mm block. In addition, for comparison of bond strength, specimens were prepared for the group that was polished and the group that was blasted at 3 atm using 110 µm alumina. Thereafter, all blocks were cut into a cross-sectional area of 1.0 × 1.0 mm to prepare 12 specimens. The specimens were immersed in distilled water at 37 ℃. for 10 days for aging treatment. A holder for tensile testing was attached to each of the specimens, and then a tensile force was applied at a crosshead speed of 0.5 mm/min to measure the fracture load. The fracture surfaces of each test piece was observed with a high-resolution field emission scanning electron microscope. Through the above tests, the following results were obtained. 1. On the blasted surface, zirconia grains were locally removed but on the Zirface treated surface, a porous microstructure was created on the zirconia surface. 2. Arithmetical mean deviation from the mean line ra was the highest in the blasted group and the lowest in the polished group, and as a result of Tukey analysis, there were statistically significant differences between all test groups (P<0.05). 3. The maximum tensile bond strength was 18.8±5.4 MPa in the Zirface 30% group, and as a result of Tukey analysis, there was a statistically significant difference from the other test groups (P<0.05). 4. As a result of observing the fracture surface after the tensile test with a high-resolution field emission scanning electron microscope, in the Zirface 30% group, cohesive fracture and interfacial fracture in the resin was observed, but the other test groups showed the interfacial fracture pattern. In conclusion, within the limits of this study, treating the zirconia surface with Zirface 30% to form a porous microstructure can contribute to the improvement of the bond strength between zirconia and resin cement.