Atomic force microscopy (AFM) has been used to investigate the surface morphology of polished dentin. In the studies of chemical conditioning (acid etching, bleaching), the morphology of polished dentin is of great importance and offers a controlled reference point for the correct and unambiguous assessment of morphological effects induced by subsequent chemical treatments. The characterization of polished dentin is required so as to permit reliable and normalized comparisons of various chemical modifications of dentin. AFM topographic data, over a fixed area of 1 mum x 1 mum, have been quantitatively analyzed and compared, using standard roughness descriptors such as the root mean square (RMS) of the surface height deviations. In addition, for a more general and complete description of surface roughness, Fourier transform analysis has been used to determine characteristic parameter values that fully describe the surface roughness in both vertical and lateral directions, independent of the feature size bandwidth considered. As a result, a confident spectral analysis interval has been assigned which ranges over the specific length scales of fibrous dentin structure. To understand how surface-polishing affect dentin roughness, and to evaluate its spatial extent of influence, AFM experiments were carried out on aluminum test surfaces which were prepared and imaged under the same conditions as the dentin samples.