Avaliação de diferentes tratamentos de superfície na resistência à flexão biaxial e nas características microestruturais e topográficas de uma cerâmica feldspática reforçada por leucita

Abstract

This study aimed to evaluate the influence of surface treatment on biaxial flexural strength, roughness, microstructure and composition of glass ceramics. Fifty-four ceramic disks (diameter: 12 mm; thickness: 1.2 mm) were obtained from leucitereinforced feldspathic CAD/CAM blocks (IPS Empress Cad Cerec, Ivoclar Vivadent). The discs were divided into three groups (n=18), according to the surface treatment: hydrofluoric acid 5% 20 s and silane (HF20); 5% hydrofluoric acid 60 sec and silane (HF60); and self-etching ceramic primer (P). For roughness analysis in a digital optical profile meter, microscopy and chemical analysis (energy dispersive X-rays – EDS) in a scanning electron microscope, analysis of the contact angle in a goniometer and knoop hardness in a microdurometer, three samples from each group were used. The remaining 15 were cemented on an epoxy resin disc (diameter: 12 mm; thickness: 2.3 mm), material analogous to dentin with dual resin cement, and drinks to mechanical fatigue (1.2 x 106 cycles, 50N, 3, 8 Hz) and the biaxial flexion test (1 mm/min; 1,000 Kgf). Biaxial flexural strength (MPa) and roughness (μm) data were submitted to oneway analysis of variance (ANOVA) and Tukey's test (5%). For HF20, the result was statistically superior to HF60 (p < 0.001); P was similar to the others. Weibull indicated that the most reliable treatment was P. Regarding the accommodation time, it was tolerated that the time of 60 s significantly increased the average value of surface roughness (p < 0.001), compared to 20 s. Surface micrographs indicated a greater change in the HF groups compared to the P groups. In the EDS, it was noted that the percentage of silica was high. Transient microscopies in the HF groups showed an increase in the innocence of the vitreous matrix and exposure of the other contents. As for the P group, a greater surface homogeneity is observed. In the evaluation of knoop hardness (HK), the highest value obtained was for the P group. For the analysis of the contact angle (º) the lowest degree found was for the HF60 group. It is concluded that the type of surface treatment interferes with the roughness and resistance of the ceramic treated with leucite when different settling times with HF are used. Thus, the self-etching ceramic primer can be a satisfactory alternative for etching the studied glass ceramic, as it promoted topographic changes without the need for HF acid.