Fracture strength and microstructure of Y-TZP zirconia after different surface treatments

• Published in: The Journal of prosthetic dentistry Vol. 110; no. 4; pp. 274 - 280
• Main Authors: Song, Jin-Young, DDS, MSD, Park, Sang-Won, DDS, PhD, Lee, Kwangmin, PhD, Yun, Kwi-Dug, DDS, PhD, Lim, Hyun-Pil, DDS, PhD
• Format: Journal Article
• Language: English
• Published: United States Mosby, Inc 01.10.2013
• Subjects: Abrasion; Abrasion resistance; Aluminum Oxide - chemistry; Cementation - methods; Dental Bonding; Dental Etching - methods; Dental Materials - chemistry; Dental Polishing - methods; Dental Porcelain - chemistry; Dental Stress Analysis - instrumentation; Dental Veneers; Dentistry; Diamond - chemistry; Flexural strength; Heat treatment; Hot Temperature; Humans; Materials Testing; Microscopy, Electron, Scanning; Modulus of rupture in bending; Pliability; Stress, Mechanical; Surface Properties; Tetragonal zirconia polycrystals; X-Ray Diffraction; Yttria stabilized zirconia; Yttrium - chemistry; Zirconium - chemistry; Zirconium dioxide
• ISSN: 0022-3913; 1097-6841
• DOI: 10.1016/S0022-3913(13)60376-5

Statement of problem Airborne-particle abrasion of the inner and outer surfaces of an yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) core is used in an attempt to enhance the bond strength between the core and the veneering porcelain and to increase the surface area for cementation. However, airborne-particle abrasion introduces surface flaws that act as stress concentrators that may compromise the mechanical strength of the ceramic. Purpose The purpose of this study was to investigate the effect of airborne-particle abrasion and heat treatment on the microstructure, biaxial flexural strength, and reliability of Y-TZP zirconia ceramics before veneering and cementation. Material and methods Forty-eight disks (15 mm in diameter, 0.5 mm in thickness) of Y-TZP were divided into 6 groups. Three treatments (untreated, airborne-particle abrasion, and heat treatment after airborne-particle abrasion) were applied to the upper surfaces, and 2 treatments (untreated and airborne-particle abrasion) were applied to the lower surfaces to mimic the preparation for veneering and cementation. For airborne-particle abrasion, 110 μm Al2 O3 particles were used. The maximum load at fracture was calculated with a biaxial flexural strength test. The upper surfaces were facing the loading piston, and the lower surfaces were facing the supporting jig during testing. Results were analyzed with 2-way ANOVA (α=.05). The treated and fractured surfaces were observed with a scanning electron microscope. The relative content of the monoclinic phase was quantified with an x-ray diffraction analysis. Results The group with airborne-particle abraded lower surfaces showed significantly higher flexural strength than the untreated group ( P <.001). The SEM images of the airborne-particle abraded zirconia specimens showed rough and irregular surfaces. The fracture initiated from the tension side, which was opposite to the applied load. Conclusions Within the limits of this in vitro study, the results showed that airborne-particle abrasion of the lower surfaces increases the flexural strength of Y-TZP zirconia.