RESEARCH AND EDUCATION Does airborne-particle abrasion before, rather than after, zirconia sintering lead to higher mechanical strength even under aging challenge? Samira Branco Martins, DDS, MSc, a Flávia Zardo Trindade, DDS, MSc, PhD, b Márcio de Sousa Góes, Lic Chem, MSc, PhD, c Gelson Luis Adabo, DDS, MSc, PhD, d Lívia Nordi Dovigo, DDS, MSc, PhD, e and Renata Garcia Fonseca, DDS, MSc, PhD f The use of yttria-stabilized tetragonal zirconia polycrystals (Y-TZPs) has increased because of their biocompatibility 1 and excellent mechanical proper- ties. 2,3 However, as this material does not contain a glassy matrix, etching with hydrofluoric acid does not roughen the surface sufficiently to provide micromechanical interlocking for adhesive bonding. 4,5 Furthermore, zir- conia is a relatively inert mate- rial with low surface energy and wettability, 6,7 which hin- ders its interaction with the materials used for cementation. For these reasons, different surface treatments have been proposed to improve the zir- conia/resin cement bonding mechanism. Among them, airborne-particle abrasion has been widely applied, being a straightforward and effective a Doctoral student, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University (UNESP), Araraquara, Brazil. b Post-doctoral Fellow, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University (UNESP), Araraquara, Brazil. c Associate Professor, Institute of Chemistry, Federal University of Latin American Integration (UNILA), Foz do Iguaçu, Brazil. d Full Professor, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University (UNESP), Araraquara, Brazil. e Assistant Professor, Department of Social Dentistry, São Paulo State University (UNESP), School of Dentistry, Araraquara, Brazil. f Associate Professor, Department of Dental Materials and Prosthodontics, Araraquara Dental School, São Paulo State University (UNESP), Araraquara, Brazil. ABSTRACT Statement of problem. Information concerning the effect of airborne-particle abrasion before zirconia sintering on its strength after aging is lacking. Purpose. The purpose of this in vitro study was to determine the influence of airborne-particle abrasion moment (before or after zirconia sintering), particle size, and aging on the mechanical strength of a yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic. Material and methods. Four hundred presintered zirconia disks were allocated to nonabraded (control) and abraded groups with 50 mm or 120 mm Al 2 O 3 particles before (50/BS or 120/BS) or after sintering (50/AS or 120/AS). The disks were aged by storing them in distilled water for 24 hours at 37  C (24 h) (control); mechanical cycling (MC) (1×10 6 cycles; 2 Hz; 100 N); hydrothermal aging (HA) (134  C; 0.2 MPa; 20 hours); or by both methods (MC+HA), totaling 20 groups (n=20). The specimens were subjected to biaxial flexural strength (BFS) testing. Fractographic analysis was performed to identify the fracture origin. Tetragonal to monoclinic transformation was determined by X-ray diffraction. The BFS data (MPa) were analyzed by 2-way ANOVA and the Games-Howell post hoc test (a=.05). Weibull statistics was also applied. Results. The BFS and characteristic strength (s0) of the 120/AS groups were significantly higher compared with the other abraded groups and statistically similar or higher compared with the respective nonabraded groups. In contrast, the 120/BS/24 h and all the 50/BS groups presented the lowest values. In all groups, the initial defect had its origin on the tensile stress side. Neither airborne-particle abrasion nor aging (except for the 50/AS/MC+HA) reduced the zirconia reliability compared with the respective controls. Abrading the zirconia in its presintered stage or after sintering increased the monoclinic phase content, and the sintering process eliminated this phase. Conclusions. Airborne-particle abrasion before zirconia sintering yields an inferior performance compared with that after sintering under aging challenges. The BFS and s0 were strongly determined by the particle size and airborne-particle abrasion moment, while aging mainly acted in the nonabraded zirconia or when this material was abraded before sintering. (J Prosthet Dent 2020;123:155-62) THE JOURNAL OF PROSTHETIC DENTISTRY 155