Adsorption onto tooth enamel — the biological interface and its modification

Abstract

The purpose of this study was to provide further information on several aspects of bioadhesion at the enamel surface. In the first part of the article the artificial modification of dental enamel is illuminated. The interaction of hydroxyapatite, which is the main constituent of tooth enamel, and tooth enamel with different kinds of carboxylic acids was investigated by Fourier transform IR spectrometry, scanning electron microscopy and X-ray photoelectron spectroscopy (XPS). The XPS spectra clearly reveal that the surface treatment substantially increases the relative intensities of Ca, P and O with respect to the surface of the polished enamel reference. In the second part of the article the examination of the natural modification of dental enamel by atomic force microscopy (AFM) is reported. This study was performed to evaluate the use of the aforementioned techniques in examining the surface of the native dental enamel and the protein layer (salivary pellicle) adsorbed in vivo on dental enamel as well. Enamel test pieces were attached to the buccal surfaces of the upper first molar teeth in two adults using removable intraoral splints. The splints were carried intraorally over periods ranging from 1 min to1 h. Pellicle structures could be identified by AFM on intraorally exposed specimens as compared to nonexposed enamel surfaces. The surface of the adsorbed salivary pellicle was characterised by a dense globular appearance. The diameter of the globulelike protein aggregates varied between 100 and 250 nm. This study indicates that the combination of microscopic and spectroscopic techniques is a powerful tool for high-resolution examination of enamel and the salivary pellicle surface structure.