Accelerated aging characteristics of three yttria-stabilized tetragonal zirconia polycrystalline dental materials

• Published in: The Journal of prosthetic dentistry 2012-10, Vol.108 (4), p.223-230
• Main Authors: Flinn, Brian D., PhD, deGroot, Dirk A., BSc, Mancl, Lloyd A., PhD, Raigrodski, Ariel J., DMD, MS
• Format: Article
• Language: English
• Subjects: Aging; Ceramics - chemistry; Crystallography; Dental Materials - chemistry; Dental Stress Analysis - instrumentation; Dentistry; Flexural strength; Hot Temperature; Humans; Lava; Materials Testing; Microscopy, Electron, Scanning; Modulus of rupture in bending; Pliability; Pressure; Steam; Sterilization - instrumentation; Stress, Mechanical; Surface Properties; Tetragonal zirconia polycrystals; Time Factors; Transformations; Water; X-Ray Diffraction; Yttria stabilized zirconia; Yttrium - chemistry; Zirconium - chemistry
• ISSN: 0022-3913; 1097-6841
• DOI: 10.1016/S0022-3913(12)60166-8

Statement of problem Concerns have been expressed about the effect of aging on the mechanical properties of zirconia. Purpose The purpose of this study was to assess the accelerated aging characteristics of 3 commercially available yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) materials by exposing specimens to hydrothermal treatments at 134°C, 0.2 MPa and 180°C, 1.0 MPa in steam. Material and methods Thin bars of Y-TZP from 3 manufacturers, Lava, Zirkonzahn, and Zirprime, n=30 for each brand (22 × 3 × 0.2 mm), were cut and ground from blocks and sintered according to the manufacturer's specifications. Control specimens (n=10) for each brand were evaluated in the as-received condition. Experimental specimens were artificially aged at standard autoclave sterilization conditions,134°C at 0.2 MPa (n=5 per group at 50, 100, 150, and 200 hours) and standard industrial ceramic aging conditions, 180°C at 1.0 MPa (n=5 per group at 8, 16, 24, 28, and 48 hours). Tetragonal to monoclinic transformation was measured by using X-ray diffraction (XRD) for all groups. Flexural strength was measured in 4-point bending (ASTM1161-B) for all groups. Fracture surfaces were examined by scanning electron microscopy (SEM). Data were analyzed as a function of aging time. The statistical comparisons were based on the log value and 2-way ANOVA with heteroscedasticity-consistent standard errors used to compare mean strength among conditions (α=.05). Results After 200 hours at 134°C and 0.2 MPa, flexural strength (SD) decreased significantly from 1156 (87.6) MPa to 829.5 (71) MPa for Lava; 1406 (243) MPa to 882.7 (91) MPa for Zirkonzahn; and 1126 (92.4) MPa to 976 (36.4) MPa for Zirprime with P