The aim of this study was to analyse the influence of the artificial saliva on a three-dimensional (3-D) surface texture of contemporary dental composites. The representatives of four composites types were tested: nanofilled (Filtek Ultimate Body, FUB), nanohybrid (Filtek Z550, FZ550), microfilled (Gradia Direct, GD) and microhybrid (Filtek Z250, FZ250). The specimens were polymerised and polished by the multistep protocol (SuperSnap, Shofu). Their surface was examined, before and after 3 weeks' exposure to artificial saliva storage. The surface texture was analysed using the atomic force microscope (AFM). The obtained images were processed to calculate the areal autocorrelation function (AACF), anisotropy ratio Str (texture aspect ratio), and structure function (SF). The log-log plots of SF were used to calculate fractal properties, such as fractal dimension D, and pseudo-topothesy K. The analysis showed changes in surface anisotropy ratio Str values, which became higher, whereas the Sq roughness (root-mean-square) reduced after the artificial saliva storage. All the samples exhibited bifractal structure before the saliva treatment, but only half of them remained bifractal afterwards (GD, FZ250), whereas the other half turned into a monofractal (FUB, FZ550). The cube-count fractal dimension Dcc was found to be material- and treatment-insensitive.
Keywords: Areal autocorrelation function; atomic force microscopy; dental nanocomposite; fractal analysis; surface texture.
© 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.