Estudo comparativo das propriedades de ionômeros de vidro comerciais - uma contribuição científica.

Abstract

Glass-ionomer cements (GIC) are composed of a mixture of silicon and aluminum oxides together with fluoride in an aqueous solution of a polyalkenoic acid. Through a set of acid-base reactions, a salt forms in a hydrogel matrix that acts as a stabilizer of the cement. They are widely used in dentistry and also in medicine, however, there is necessity of research on the compositions of these materials in order to obtain a better clinical performance. So the purpose of this study was the characterization of commercial GICs: OG GIC and VM GIC, in order to observe the morphology, chemical composition, crystal structure and the degree of hydrophilicity of these materials. To compare the experimental data, four experimental compositions of GICs were developed: GICs A, B, C and D. All cements were characterized by techniques of Fourier-transform infrared Spectroscopy (FTIR), x-ray diffraction (XRD), analysis of surface tension (TS), scanning electron microscopy (SEM) and energy dispersive spectrometry by x-ray (XRD). Through x-ray diffraction the commercial GICs did not exhibit any peaks of the crystalline phase; however, for experimental GICs the presence of crystalline phases was confirmed. In infrared spectroscopy showed the typical bands of these materials. The fluoride appeared in experimental GICs between 460 and 400 cm- 1 and commercial GICs around 900 cm"1. The C=C, C=0 and Si-0 bonds appeared more intense in all experimental GICs, but in the commercial GICs these bands are more tenuous. Bands attributed to the presence of water were found in the range of 3400 to 3600 cm"1 and 640 cm"1 for experimental GICs, however for commercial GICs these bands were situated from 3400 to 3600 cm"1, related to the presence of carboxylic groups. In the tests of surface tension (TS), both cements were hydrophilic with angles near 60°, but among commercial GICs, VM GIC showed lower hydrophilic character. For the experimental GICs, the values were statistically equal; however, GIC B showed less hydrophilic character. The analysis by scanning electron microscopy and energy dispersive spectrometry by x-ray revealed that among the commercial GICs, VM GIC showed greater interaction between solid and liquid and experimental GICs presented only a subtle liquid-solid interaction showing a significant difference in energy between the surface phases.