Effect of grain size on the monoclinic transformation, hardness, roughness, and modulus of aged partially stabilized zirconia.
OBJECTIVE
Low-temperature-degradation (LTD) has been reported to cause property changes in yttria-tetragonal zirconia polycrystals (Y-TZP). The current study measured monoclinic phase transformation of Y-TZP with different grain sizes and corresponding property changes due to artificial aging.


OBJECTIVE
the grain size of aged Y-TZP will not influence its transformation, roughness, hardness or modulus of elasticity.


METHODS
Four groups of Y-TZP were examined with differing grain sizes (n=5). The line intercept technique was used to determine grain sizes on SEM images (100,000×). Artificial aging was accomplished by autoclaving at 2 bar pressure for 5 h. X-ray diffraction (30 mA, 40 kV) was used to measure tetragonal to monoclinic transformation (t→m). Surface roughness analysis was performed using a non-contact surface-profilometer. Nano-hardness and modulus of elasticity were measured using nano-indentation.


RESULTS
SEM analyses showed different grain sizes for each sample group (0.350 μm, 0.372 μm, 0.428 μm, and 0.574 μm). The fraction of t→m transformation increased as grain size increased; furthermore, aging of zirconia caused increased roughness. Modulus and hardness after aging displayed no significant correlation or interaction with grain size.


CONCLUSIONS
Smaller grains caused less transformation, and aging caused increased roughness, but grain size did not influence the amount of increased surface roughness. Future studies are needed to determine the effects of grain size on the wear and fracture properties of dental zirconia.
Department of Restorative Sciences, Biomaterials Division, University of Alabama at Birmingham School of Dentistry, 1919 7th Ave S, SDB 604, Birmingham, AL 35294, United States; Department of Materials Science and Engineering, University of Alabama at Birmingham School of Engineering, Hoehn Engineering Building, HOEHN 115A, 1075 13th Street South, Birmingham, AL 35294-4440, United States. Electronic address: tjlucas@uab.edu.
Thomas J
TJ
Lucas
Department of Restorative Sciences, Biomaterials Division, University of Alabama at Birmingham School of Dentistry, 1919 7th Ave S, SDB 604, Birmingham, AL 35294, United States.
Nathaniel C
NC
Lawson
Department of Materials Science and Engineering, University of Alabama at Birmingham School of Engineering, Hoehn Engineering Building, HOEHN 115A, 1075 13th Street South, Birmingham, AL 35294-4440, United States.
Gregg M
GM
Janowski
Department of Restorative Sciences, Biomaterials Division, University of Alabama at Birmingham School of Dentistry, 1919 7th Ave S, SDB 604, Birmingham, AL 35294, United States.
John O
JO
Burgess
D003764:Dental Materials / Q000737:chemistry*; D055119:Elastic Modulus; D006244:Hardness; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D018583:Pliability; D013314:Stress, Mechanical; D013499:Surface Properties; D014961:X-Ray Diffraction; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
D003764:Dental Materials; D015019:Yttrium; D015040:Zirconium; C028541:zirconium oxide; C091417:yttria
Aging; Grain size; LTD; Transformation; Zirconia