RESUMEN
Novel silica-based infiltrations on the surface of zirconia have the potential to improve their bondability, allowing for the etching/silane adhesive bonding technique. Nonetheless, adhesively bonded joints are subject to mixed tensile and shear stresses when the restoration is in occlusal service. Thus, we aimed to investigate the effect of 2 novel silica-based infiltrations on the interfacial toughness of adhesively bonded zirconia using the Brazil nut method, which allows for controlled types of stresses to be applied at the interfaces. In total, 150 3Y-TZP (In-Ceram YZ; Vita) Brazil nuts were machined and randomly assigned to 3 groups: C, control (air abraded); SG, sol-gel silica infiltration; and GI, glass infiltration. SG specimens were immersed twice in silicic acid for 20 min and dried (100°C, 1 h). GI specimens were presintered (1,400°C, 1 h) before a glass powder slurry was applied to the intaglio surface. All specimens were then sintered (1,530°C, 2 h). Following adhesive bonding (Panavia F 2.0, Kuraray) and water storage (37°C) for 10 d, the Brazil nuts were subdivided into groups baseline and aged (40,000 thermal cycles between 5°C and 55°C, with a dwell time of 30 s). The Brazil nuts were subjected to axial-loading tests using various inclinations (precrack angle with load direction): Θ = 0°, 5°, 10°, 15°, or 25°, which define the stress type at the interface, from pure tension (0°) to increasing levels of shear. Under pure tension (0°), GI yielded superior interfacial fracture energy, SG and C were similar, and aging had no effect. Under predominantly shear stresses (25°), aging significantly decreased interfacial fracture energy of C and SG, while GI remained stable and was superior. The glass infiltration of the zirconia intaglio surface increases its adhesive bonding interfacial toughness. The sol-gel silica infiltration method requires improvement to obtain a homogeneous surface infiltration and an enhanced bond strength.
Asunto(s)
Recubrimiento Dental Adhesivo , Resinas Sintéticas , Dióxido de Silicio , Circonio , Óxido de Aluminio , Cerámica , Ensayo de Materiales , Cementos de Resina , Estrés Mecánico , Propiedades de SuperficieRESUMEN
OBJECTIVE: The aim of this study was to evaluate silica infiltration into dental zirconia (VITA In-Ceram 2000 YZ, Vita Zahnfabrik) and its effects on zirconia's surface characteristics, structural homogeneity and bonding to a resin cement. METHODS: Infiltration was performed by immersion of the pre-sintered zirconia specimens in silica sols for five days (ZIn). Negative (pure zirconia specimens, ZCon-) and positive controls (specimens kept in water for 5 days, ZCon+) were also performed. After sintering, the groups were evaluated by X-ray diffraction (XRD), grazing angle X-ray diffraction (DRXR), scanning electron microscopy (SEM), contact angle measurements, optical profilometry, biaxial flexural test and shear bonding test. Weibull analysis was used to determine the Weibull modulus (m) and characteristic strength (σ0) of all groups. RESULTS: There were no major changes in strength for the infiltrated group, and homogeneity (m) was also increased. A layer of ZrSiO4 was formed on the surface. The bond strength to resin cement was improved after zirconia infiltration, acid conditioning and the use of an MDP primer. CONCLUSION: The sol-gel method is an efficient and simple method to increase the homogeneity of zirconia. Infiltration also improved bonding to resin cement. CLINICAL SIGNIFICANCE: The performance of a zirconia infiltrated by silica gel improved in at least two ways: structural homogeneity and bonding to resin cement. The infiltration is simple to perform and can be easily managed in a prosthesis laboratory.