Publication

Abstract : In the present paper, the influence of tubule orientation and areal density on the development of surface textures by excimer laser processing of dentin is analysed. Disks of dentin 2 mm thick were extracted from caries-free human teeth by cross-sectional cutting above the pulp cavity, polished and fixed using standard procedures. The samples were laser-processed using 100 laser pulses of 248 nm wavelength radiation at a fluence of 1 J/cm2, pulse duration of 30 ns and pulse frequency of 5 Hz. The surface texture after processing depends on the angle between the tubules and the laser beam. In inner dentin, where tubules are parallel to the laser beam, cone-like artefacts form, considerably increasing surface roughness. The cones are constituted by partially melted peritubular dentin and develop because the ablation rate of peritubular dentin is lower than the ablation rate of surrounding intertubular dentin. The areal density of cones is roughly identical to the areal density of tubules except when the tubule density is high enough to allow adjacent cones to coalesce. In outer dentin, where tubules are tilted with respect to the laser beam, the surface remains flat. The reason for this orientation dependence is that, when tubules are tilted towards the laser beam, preferential removal of intertubular dentin will expose an increased area of underlying peritubular dentin to laser radiation preventing cone development.