RESUMO
In this paper, we monitor the setting reaction of commercial glass ionomer cements using a laser speckle technique and adopting a spatial approach in the analysis of recorded speckle images. Experimental results showed that spatial contrast and speckle grain size increased as two studied cements underwent their setting reactions. After combining two geometrical configurations to measure the intensities of backscattered and transmitted light, we concluded that the increase in speckle grain size was caused by an increase in size of the scattering centers, since cement components aggregate and hence transition from a Rayleigh to a Mie scattering regime. Finally, two main phases were distinguished in the hardening process, as reported in the literature; however, the technique we propose has the advantage of easily identifying these two phases. The analysis of a single speckle image offers multiple advantages over the temporal analysis of a series of speckle images, in particular due to the low number of images recorded and a far shorter image processing time.
RESUMO
Glass ionomer cements (GIC) originated in the mid-twentieth century with the rising demand for dental materials to be biocompatible and cost-effective. Due to their unique ability to bond to tooth structure, coupled with their fluoride-releasing potential, GIC are widely used in pediatric dentistry. However, the curing kinetics of these materials are not extensively documented. In this study, we show that dynamic laser speckle is an efficient method for monitoring the acid-base reaction that occurs during the self-setting of conventional GIC. Plotted temporal correlation curves, showing the degree of similarity between several recorded speckle patterns, indicate that the GIC kinetics reaction slows down during the curing phenomenon. Furthermore, the numerical fit of the temporal correlation curves with a Lorentzian profile gives the characteristic times of the reaction and reveals two phases during GIC hardening.