Influence of surface and heat treatments on the flexural strength of a glass-infiltrated alumina/zirconia-reinforced dental ceramic.
OBJECTIVE
The purpose of this study was to investigate the influence of sandblasting, grinding, grinding orientation and polishing before and after heat treatment, on the flexural strength of a glass-infiltrated alumina/zirconia-reinforced dental ceramic (In-Ceram Zirconia).


METHODS
The uniaxial flexural strength was calculated on 160 bar-shaped specimens (20 x 4 x 1.2mm) divided equally into eight groups as follows: sandblasted; sandblasted heated; polished; polished heated; ground parallel to the tensile axis; ground parallel heated; ground perpendicular; and ground perpendicular heated. Data were analyzed with multiple regression analysis, one-way ANOVA and Tukey's pairwise multiple comparisons and Weibull analysis. The treated and fractured surfaces were observed with SEM. The relative content of the monoclinic phase was quantified with an X-ray diffraction analysis.


RESULTS
A thin layer of glass was present on the surface of the specimens after heat treatment and contributed to an improvement of the flexural strength. Surface treatment (not followed by heat treatment) generated phase transformation which, however, was not sufficient to avoid strength degradation caused by the flaws introduced with the surface treatments. Sandblasting caused the most marked strength degradation. Polishing alone increased the reliability, but did not improve the strength. The orientation of grinding in respect of the direction of the tensile stresses did not influence the ultimate tensile strength.


CONCLUSIONS
The present study suggests that any surface treatment performed on In-Ceram Zirconia should always be followed by heat treatment to avoid strength degradation.
Guazzato
Massimiliano
M
Biomaterials Science Research Unit, Faculty of Dentistry, University of Sydney, United Dental Hospital, Surry Hills, NSW 2010, Australia. mgua2483@mail.usyd.edu.au
Albakry
Mohammad
M
Quach
Linda
L
Swain
Michael V
MV
D000537:Aluminum Oxide; D000704:Analysis of Variance; D018360:Crystallography, X-Ray; D003775:Dental Polishing; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D004548:Elasticity; D005898:Glass; D006358:Hot Temperature; D008422:Materials Testing; D008669:Metallurgy; D018583:Pliability; D012044:Regression Analysis; D018709:Statistics, Nonparametric; D013499:Surface Properties; D016019:Survival Analysis; D013718:Tensile Strength; D015040:Zirconium
D003776:Dental Porcelain; C070870:In-Ceram; D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide