Aging resistance of surface-treated dental zirconia

The influence of surface treatment on the low-temperature degradation (LTD) of tetragonal zirconia polycrystalline (TZP) is still unclear. Objectives. The effect of surface treatments on the LTD behavior of zirconia was investigated. Methods. Fully-sintered specimens of seven commercial dental zirconia (Aadva, GC; In CeramYZ, VITA; IPS e.max ZirCAD, Ivoclar Vivadent; LAVA Frame and LAVA Plus, 3M ESPE; NANOZR, Panasonic; ZirTough, Kuraray Noritake) were provided by the manufacturers with specimen dimensions of approximately 10 mm x 5 mm x 3 mm. For each zirconia grade, samples were kept 'as sintered' (untreated) or were subjected to one of the three surface treatments: rough polished, sandblasted with Al2O3, tribochemical silica sandblasted (n = 3/group). The tetragonal to monoclinic transformation was evaluated by X-ray diffraction at several intervals during LTD testing up to 40 h in steam in an autoclave (134 degrees C, 2 bar). Results. The five yttria-stabilized TZP (Y-TZP: Aadva, In-CeramYZ, IPS e.max ZirCAD, LAVA Frame, LAVA Plus) zirconia showed a similar trend in LTD behavior. The Al2O3 sand-blasted zirconia showed the highest monoclinic volume fraction. The as sintered (untreated) zirconia degraded faster than the surface-treated zirconia. Although the surface-treated ceria-stabilized TZP/alumina (Ce-TZP/Al2O3: NANOZR) zirconia had a higher initial monoclinic volume fraction compared to the Y-TZP zirconia, it showed a stronger aging resistance. The as sintered (untreated) Y-TZP/alumina (Y-TZP/Al2O3: ZirTough) zirconia showed a strong aging resistance, whereas the surface-treated Y-TZP/Al2O3 zirconia degraded slightly. Significance. Surface treatment improved the aging resistance of Y-TZP zirconia. Surface treatment did not affect the LTD behavior of Ce-TZP/Al2O3 zirconia, while surface treatment decreased the aging resistance of Y-TZP/Al2O3 zirconia. (C) 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.