The Effects of Ion Sputtering on Dentin and its Relation to Depth Profiling

Characterization of the dentin surface and the dentin/adhesive interface is fundamental to investigations concerning adhesive bonding to dentin. It has been shown that good adhesive bonding depends on both the structure and composition of the dentin surface. A combination of ion sputter etching and Auger electron spectroscopy can be used to obtain surface composition and elemental depth profiles at interfaces. This investigation was conducted to examine the changes induced in human dentin by ion sputtering under conditions commonly encountered during depth profiling. The sputtering was conducted with argon ions at 7.5 keV and an ion flux ranging from 1018-1019 ions/m 2s. The amount of material sputtered was calculated from profilometer measurements of the sample surface. The surface composition was monitored by Auger electron spectroscopy. The results indicate that, under these conditions, collagen was removed at a much faster rate than hydroxyapatite, causing the surface composition of dentin to change during the sputtering process. The sputter yields for hydroxyapatite and collagen were found to be 5 and 28 atoms/ion, respectively, at a sputter angle of 45°. At a sputter angle of 29°, the yields were 2 and 25 atoms/ion, respectively. Both the changes in composition of dentin and the measured sputter rates are in agreement with the behavior predicted by a theoretical model for two phase materials (Blaise, 1978; Blaise et al., 1978).