Comportamento mecânico e adesivo de um compósito reforçado com fibras de vidro para a utilização como substrato em testes de laboratório

Abstract

The objective of the study was to obtain the mechanical and adhesive properties of a polymer reinforced by glass fiber (PRGF), and to compare it with the dentin (HD), aiming its application as a substrate in laboratory tests. Five discshaped samples of PRGF of dentin (n=5), with approximately 2 mm in thickness, were obtained to evaluate the density (using the Archimedes principle), and the elastic modulus and Poisson ratio (using an ultrasonic gauge). Ten GFRC samples were prepared for the Knoop hardness evaluation. Qualitative evaluation in scanning electron microscope and surface roughness were performed after the PRGF surface conditioning with 10% hydrofluoric acid for 15, 30, 45 and 60 seconds. Twenty PRGF and ten HD blocks, with 4-mm thickness, were obtained to evaluate their union with a feldspathic ceramic, using the microtensile bond strength test. Half of the PRGF blocks (n = 10) were conditioned (10% HF) for 15s, and half for 60s. Microbars with 1 mm 2 of area in the interface, composed by feldspathic ceramic, resin cement and substrate, were tested. Subsequently, 33 PRGF and 33 DH discs were obtained for the compression test. Slices (1.5-mm of thickness) of the feldspathic ceramic were cemented with resin cement to the substrates, and loaded to failure. The results were compared using 1-way Anova, Tukey test (α = 0.05) and Weibull analysis. PRGF had a mean density of 1.9 g/cm 3 , a mean Poisson ratio of 0.44, and a mean elastic modulus of 13.11 GPa, values statistically different than the dentin values. The mean hardness was 53.14. The hydrofluoric acid conditioning had visible effect on the PRGF surface, and resulted in a progressive increase on the surface roughness of the material related to the increase on the conditioning time. There was no difference between dentin and PRGF regarding to the adhesive strength to a feldspathic ceramic, irrespective the conditioning time. The mean bond strength values were between 10.9 and 9.6 MPa. The fracture load of a feldspathic ceramic cemented on the dentin (455.43 N) was higher compared to the load of the ceramic cemented on the PRGF (270.68 N).