AFM and SEM study of the eects of etching on IPS-Empress 2 TM dental ceramic X.-P. Luo, N. Silikas, M. Allaf, N.H.F. Wilson, D.C. Watts * University of Manchester Dental School, Higher Cambridge Street, Manchester M15 6FH, UK Received 16 November 2000; accepted for publication 21 March 2001 Abstract The aim of this study was to investigate the eects of increasing etching time on the surface of the new dental material, IPS-Empress 2 TM glass ceramic. Twenty one IPS-Empress 2 TM glass ceramic samples were made from IPS-Empress 2 TM 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% hydro¯uoric acid gel. The etching times were 0, 10, 20, 30, 60, 90 and 120 s respectively.MicrostructurewasanalysedbyscanningelectronmicroscopySEM)andatomicforcemicroscopyAFM) was used to evaluate the surface roughness and topography. Observations with SEM showed that etching with hydro¯uoric 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 R a , RMS), and etching time, for which r 2 > 0:94. This study demonstrates the bene®ts of combining two microscopic methods for a better understanding of the surface. SEM showed the mode of action of hydro¯uoric acid on the ceramic and AFM provided valuable data re- garding the extent of surface degradation relative to etching time. Ó 2001 Elsevier Science B.V. All rights reserved. Keywords: Atomic force microscopy; Scanning electron microscopy SEM); Ceramics; Surface roughening; Etching 1. Introduction Recently, a newly developed IPS-Empress 2 TM dental ceramic incorporating lithium di-silicate crystal has been introduced. This ceramic exhibits material properties which include high strength, excellent aesthetics, marginal integrity, and etch- ability. The latter property permits adhesive bonding to the underlying tooth structure by per- mitting micro-mechanical interlocking of dual- curing resins within surface features [1,2]. The lithium di-silicate glass ceramic, combined with a sintered glass ceramic layering technique, permits the fabrication of veneers, crowns and all ceramic bridges that demonstrate properties similar to those of natural teeth. Compared to other high strength all-ceramics such as zirconium, alumina sintered ceramics), IPS-Empress 2 TM has excellent translucency and may be applied via an adhesive Surface Science 491 2001) 388±394 www.elsevier.com/locate/susc * Corresponding author. Tel.: +44-161-275-6749; fax: +44- 161-275-6748. E-mail address: david.watts@man.ac.uk D.C. Watts). 0039-6028/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII:S0039-602801)01301-2