The surface of zirconia-based dental ceramic restorations require preparation prior to adhesive cementation. The purpose of this study was to assess the influence of airborne-particle abrasion with different sizes of alumina particles (50 μm, 110 μm, or 250 μm) on the mechanical strength of zirconia-based ceramics’ frameworks and on the extent of phase transformations. A fracture resistance test was performed. The central surface of the frameworks was subjected to a load [N]. The identification and quantitative determination of the crystalline phase present in the zirconia specimens was assessed using X-ray diffraction. The Kruskal–Wallis one-way analysis of variance was used to establish significance (α = 0.05). The fracture resistance of zirconia-based frameworks significantly increases with an increase in the size of alumina particles used for air abrasion: 715.5 N for 250 μm alumina particles, 661.1 N for 110 μm, 608.7 N for 50 μm and the lowest for the untreated specimens (364.2 N). The X-ray diffraction analysis showed an increase in the monoclinic phase content after air abrasion: 50 μm alumina particles—26%, 110 μm—40%, 250 μm—56%, and no treatment—none. Air abrasion of the zirconia-based dental ceramics’ surface with alumina particles increases the fracture resistance of zirconia copings and the monoclinic phase volume. This increase is strongly related to the alumina particle size.

A B S T R AC TIntroduction: The loss of retention of zirconia-based fixed partial dentures (FPDs) is one of the most frequently reported failures. Objectives: The purpose of this study was to evaluate the shear bond strength (SBS) of four resin cements to zirconia after air-borne particle abrasion with alumina of different grades and application of respective primers incorporating organophosphate monomers. Material and methods: The 443 cuboid-shape zirconia specimens (Ceramill Zi; Amann Girrbach AG) were divided into 16 research groups, according to the chemo-mechanical modification: air-abrasion with alumina particles of 50 μm, 110 μm or 250 μm grade, no treatment and application of primers and resin cements: Clearfil Ceramic Primer/Panavia F2.0 (Kuraray Medical), Monobond Plus/Multilink Automix (Ivoclar Vivadent AG), AZ-Primer/ResiCem (Shofu), Z-Prime Plus/Duo-Link (Bisco). After storage in 37 ± 1°C distilled water for 24 hours, the SBS test was conducted (Zwick/Roell Z005; Zwick GmbH&Co.KG) at 1 mm/min crosshead speed to failure. Specimens were subjected to fractographic analysis at ×2.5 and ×35 magnification (Seliga Auctus; Seliga Microscopes Sp.z o.o.; SEM S-4700; Hitachi High-Technologies Corporation). Statistical significance was established with the Wilcoxon signed-rank test and the Kruskal-Wallis one-way analysis of variance (p = 0.05). Results: The highest SBS values of zirconia to resin cement were obtained for Z-Prime Plus/DuoLink and after 50 μm alumina air-abrasion (6.87-14.15 MPa). However, the alumina particle grade was insignificant. A significant decrease in the SBS was observed for untreated specimens (4.60-8.24 MPa). The failure mode in untreated specimens was mainly adhesive, while in sandblasted it was cohesive and mixed. Conclusions: The chemo-mechanical treatment of zirconia surface before adhesive cementation is crucial to obtain satisfactory values of shear bond strength to resin cements.

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