Effect of different treatments on the flexural strength of fully versus partially stabilized monolithic zirconia.
BACKGROUND
Recent monolithic zirconia materials used for indirect restorations are predominantly fully stabilized zirconia with claims of enhanced optical properties. These restorations may behave differently from the conventional partially stabilized zirconia restorations, which may negatively affect some of the core properties required for restoration success.


OBJECTIVE
The purpose of this in vitro study was to evaluate and compare the effects of staining, airborne-particle abrasion, and artificial aging on the flexural strength of fully and partially stabilized zirconia material.


METHODS
Each partially stabilized monolithic zirconia (PSZ) and fully stabilized zirconia (FSZ) material and a zirconia core material (control) were prepared as bar-shaped specimens (2×2×25 mm) and divided into 6 groups (n=8/subgroup): regular sintering, vacuum sintering, stained, airborne-particle abrasion, artificially aged regular sintering, and artificially aged vacuum sintering. Critical load to fracture was determined for all groups by using monotonic uniaxial loading in accordance with International Organization for Standardization standard 6872. Data were analyzed using univariate analysis of variance, followed by the Tukey honest significant difference post hoc test (α=.05).


RESULTS
The control and PSZ (1034 and 1008 MPa) displayed a significantly higher (P<.05) flexural strength than FSZ (582 MPa). Airborne-particle abrasion significantly (P<.05) enhanced the strength of the control and PSZ (1413 and 1227 MPa) but significantly (P<.05) reduced the flexural strength of the FSZ (442 MPa). Staining, artificial aging, and vacuum sintering had no significant effects on any of the groups.


CONCLUSIONS
Fully stabilized zirconia may behave differently from conventional PSZ, especially with regard to airborne-particle abrasion, which may weaken the FSZ. The strength of PSZ is approximately double the strength of FSZ. Both of the zirconia materials showed resistance to artificial aging.
Assistant Professor, Department of Operative Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, NC. Electronic address: sulaiman@unc.edu.
Taiseer A
TA
Sulaiman
Assistant Professor, Department of General Practice, School of Dentistry, Virginia Commonwealth University, Richmond, Va.
Aous A
AA
Abdulmajeed
Doctoral student, Department of Prosthetic Dentistry and Turku Clinical Biomaterials Centre, Institute of Dentistry, University of Turku, Turku, Finland.
Khalil
K
Shahramian
Associate Professor and Laboratory Manager, Department of Prosthetic Dentistry and Turku Clinical Biomaterials Centre, Institute of Dentistry, University of Turku, Turku, Finland.
Lippo
L
Lassila
D003764:Dental Materials; D003799:Dental Stress Analysis; D008422:Materials Testing; D018583:Pliability; D013314:Stress, Mechanical; D015040:Zirconium
D003764:Dental Materials; D015040:Zirconium; C028541:zirconium oxide