Femtosecond laser ablation of bovine cortical bone

Abstract

We study the surface topographical, structural, and compositional modifications induced in bovine cortical bone by femtosecond laser ablation. The tests are performed in air, with a Yb:KYW chirped-pulse-regenerative amplification laser system (500 fs, 1030 nm) at fluences ranging from 0.55 to 2.24 J/cm2. The ablation process is monitored by acoustic emission measurements. The topography of the laser-treated surfaces is studied by scanning electron microscopy, and their constitution is characterized by glancing incidence x-ray diffraction, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and micro-Raman spectroscopy. The results show that femtosecond laser ablation allows removing bone without melting, carbonization, or cracking. The structure and composition of the remaining tissue are essentially preserved, the only constitutional changes observed being a reduction of the organic material content and a partial recrystallization of hydroxyapatite in the most superficial region of samples. The results suggest that, within this fluence range, ablation occurs by a combination of thermal and electrostatic mechanisms, with the first type of mechanism predominating at lower fluences. The associated thermal effects explain the constitutional changes observed. We show that femtosecond lasers are a promising tool for delicate orthopaedic surgeries, where small amounts of bone must be cut with negligible damage, thus minimizing surgical trauma.

Femtosecond laser ablation of enamel

“…(5) and using the incubation coefficient value found in the present work (0.68 AE 0.08), single pulse ablation thresholds of 3.0 and 2.7 J∕cm 2 , respectively, were obtained, in good agreement with our result. The calculated value of the incubation coefficient 0.68 AE 0.08 is in good agreement with the value reported by Cangueiro et al 28 for bone. 31 This difference could be explained by the much shorter pulse duration and reduced wavelength of the laser used by Ji et al, 31 but Rode et al 29 found a single pulse ablation threshold of 2.2 J∕cm 2 using laser parameters similar to Ji et al (805-nm laser wavelength and 92-fs pulse duration).…”

“…The Raman spectra of the enamel specimens, normalized to the strongest peak, at 960 cm −1 , which corresponds to the ν 1 vibration of the phosphate group in hydroxyapatite, 28 are shown in Fig. 8.…”

“…8. 37 The peak at 1070 cm −1 , which corresponds to the ν 1 vibration of the carbonate group, 28,38 is also observed due to the partial replacement of hydroxyl and phosphate anions by the carbonate anion. 37 The peak at 1070 cm −1 , which corresponds to the ν 1 vibration of the carbonate group, 28,38 is also observed due to the partial replacement of hydroxyl and phosphate anions by the carbonate anion.…”

“…19 Another approach to reduce thermal effects is using UV lasers. 28 Therefore, no energy is transferred to the lattice during the laser pulse and most of the absorbed radiation energy is spent on the ablation process and carried away by the ablated material. The ablation mechanism is predominantly photochemical for intertubular dentin and photothermal for peritubular dentin.…”

Human Mesenchymal Stem Cell Behavior on Femtosecond Laser-Textured Ti-6Al-4V Surfaces

“…The fluence was calculated on the basis of the laser beam radius at e -2 of the maximum intensity of the Gaussian radiation intensity distribution, estimated using the D-squared method [20]. The laser beam was focused by a 100 mm focal length lens on a spot with a diameter of 338 ± 10 μm at e -2 at the surface of the specimen.…”