Product Code: PIC2008_205
Surface Modification of Dental Hard Tissues using Pulsed Uv Lasers (Invited Presentation)
Rui Vilar, Instituto Superior Tecnico; Lisboa Codex Portugal
Victor Oliveira, Instituto Superior Técnico; Lisboa Portugal
Presented at PICALO 2008
In the presentation the surface texture, structural and chemical changes induced in human dental hard tissues (dentin and enamel) by laser processing with KrF excimer laser radiation will be analysed. In dentin, the evolution of surface topography depends on the orientation of the tubules in relation to the incoming laser beam and on the radiation fluence. For fluences larger than 1 J/cm2 the processed surface is flat and covered with a thin layer of resolidified material. For fluences in the range 0.5-1 J/cm2 the processed surface presents a columnar texture where the columns are essentially formed of peritubular dentin when the tubules are approximately perpendicular to the surface and remains flat if the tubules are tilted towards the surface. Enamel does not develop cone-like or columnar textures when laser processed, independently of the fluence used. A detailed study of the morphology and growth kinetics of the columnar texture reveals that completely developed cones form a Voronoi 2D network and that cone growth in function of the number of laser pulses is well described by the Johnson-Mehl-Avrami-Kolmogorov equation. Despite these topographic changes, the dentin is not significantly affected by the laser treatment. The laser radiation is preferentially absorbed by collagen, which is partially ablated from a very thin surface layer, but the mineral phase is not modified. On the basis of the results achieved the ablation mechanisms of denting will be discussed.
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