AFM and SEM study of the effects of etching on IPS-Empress 2™ dental ceramic

The aim of this study was to investigate the effects of increasing etching time on the surface of the new dental material, IPS-Empress 2™ glass ceramic. Twenty one IPS-Empress 2™ glass ceramic samples were made from IPS-Empress 2™ ingots through lost-wax, hot-pressed ceramic fabrication technology. All samples were highly polished and cleaned ultrasonically for 5 min in acetone before and after etching with 9.6% hydrofluoric acid gel. The etching times were 0, 10, 20, 30, 60, 90 and 120 s respectively. Microstructure was analysed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) was used to evaluate the surface roughness and topography. Observations with SEM showed that etching with hydrofluoric acid resulted in preferential dissolution of glass matrix, and that partially supported crystals within the glass matrix were lost with increasing etching time. AFM measurements indicated that etching increased the surface roughness of the glass-ceramic. A simple least-squares linear regression was used to establish a relationship between surface roughness parameters (Ra, RMS), and etching time, for which r2 > 0.94. This study demonstrates the benefits of combining two microscopic methods for a better understanding of the surface. SEM showed the mode of action of hydrofluoric acid on the ceramic and AFM provided valuable data regarding the extent of surface degradation relative to etching time. © Elsevier Science B.V. All rights reserved.