AFM and SEM study of the effects of etching on IPS-Empress 2 (TM) 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(TM) glass cer amic. Twenty one IPS-Empress 2(TM) glass ceramic samples were made from IPS-Empre ss 2(TM) ingots through lost-wax, hot-pressed ceramic fabrication technolog y. All samples were highly polished and cleaned ultrasonically for 5 min in acetone before and after etching with 9.6% hydrofluoric acid gel. The etch ing times were 0, 10, 20, 30, 60, 90 and 120 s respectively. Microstructure was analysed by scanning electron microscopy (SEM) and atomic force micros copy (AFM) was used to evaluate the surface roughness and topography. Observations with SEM showed that etching with hydrofluoric acid resulted i n preferential dissolution of glass matrix. and that partially supported cr ystals 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 establi sh a relationship between surface roughness parameters (R,. RMS), and etchi ng time, for which r(2) > 0.94. This study demonstrates the benefits of combining two microscopic methods f or a better understanding of the surface. SEM showed the mode of action of hydrofluoric acid on the ceramic and AFM provided valuable data regarding t he extent of surface degradation relative to etching time. (C) 2001 Elsevie r Science B.V. All rights reserved.