Enhancing Fracture Toughness of Dental Zirconia through Incorporation of Nb into the Surface.

BACKGROUND

Our previous study found that the addition of pentavalent cations like niobium (Nb) to yttria-stabilized zirconia increased fracture toughness but also raised the coefficient of thermal expansion (CTE), and opacity also increased undesirably. A new surface treatment is required to boost fracture toughness without altering CTE or translucency.

METHODS

The surfaces of pre-sintered 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) and 4.2 mol% yttria-stabilized partially stabilized zirconia (4.2Y-PSZ) were treated with a Nb sol solution containing NbO nanoparticles. After drying and sintering, a high-Nb-content surface layer formed with a depth of approximately 1 mm.

RESULTS

The Nb content in this surface layer matched that of a bulk material with 1 mol% NbO. The tetragonality of the surface zirconia increased, enhancing the surface fracture toughness without changing the CTE or translucency.

CONCLUSIONS

Adding Nb near the surface improved the fracture toughness without affecting the CTE or translucency. This method could strengthen zirconia prostheses, allowing more reliable dental restorations.