Midinfrared ablation of dentin with the Vanderbilt FEL
Absorption spectra of 0.1 - 0.2 mm thick, dehydrated sections of human teeth were measured in the transmission mode with a Bruker FT-IR spectrometer from 2.5 - 20 μm. Absorption peaks for amide I, II and III, carbonate and phosphate were identified. Craters were ablated in dentin and enamel using a tunable FEL at 6.45 μm at various fluences. Pulse duration: 3 μs; spot size (Gaussian, FWHM): 300 μm; repetition rate: 10 Hz. Crater depth and width were measured from digitized optical images. Ablation rates were computed from crater depth and volume data. Selected specimens were examined with scanning electron microscopy to determine ablation surface characteristics. Depth of thermal damage and dentinal tubule morphology were estimated from SEM examination of fractures through ablation sites. Functions describing crater depth vs. number of pulses (quadratic function) were not the same as crater volume vs. number of pulses (linear function). Crater depth decreases with successive pulses, concurrently, the crater width increases. Thus, each pulse removes approximately a constant volume. Material was observed to flow through the dentinal tubules during and after ablation. Patent tubules on crater walls and floor were observed with SEM. Ablation rates in dentin were approximately 3× those in enamel at 6.45 μm. Ablation rates and surface characteristics varied across wavelengths from 5.8 to 8.0 μm.
Harris, DM; Reinisch, L; Edwards, GS; Yessik, MJ; Ashrafi, S; Santos-Sacchi, J
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