Biostimulatory effects of low-level laser therapy on epithelial cells and gingival fibroblasts treated with zoledronic acid

Low-level laser therapy (LLLT) has been considered as an adjuvant treatment for bisphosphonate-related osteonecrosis, presenting positive clinical outcomes. However, there are no data regarding the effect of LLLT on oral tissue cells exposed to bisphosphonates. This study aimed to evaluate the effects of LLLT on epithelial cells and gingival fibroblasts exposed to a nitrogen-containing bisphosphonate - zoledronic acid (ZA). Cells were seeded in wells of 24-well plates, incubated for 48 h and then exposed to ZA at 5 μM for an additional 48 h. LLLT was performed with a diode laser prototype - LaserTABLE (InGaAsP - 780 nm ± 3 nm, 25 mW), at selected energy doses of 0.5, 1.5, 3, 5, and 7 J cm-2 in three irradiation sessions, every 24 h. Cell metabolism, total protein production, gene expression of vascular endothelial growth factor (VEGF) and collagen type I (Col-I), and cell morphology were evaluated 24 h after the last irradiation. Data were statistically analyzed by Kruskal-Wallis and Mann-Whitney tests at 5% significance. Selected LLLT parameters increased the functions of epithelial cells and gingival fibroblasts treated with ZA. Gene expression of VEGF and Col-I was also increased. Specific parameters of LLLT biostimulated fibroblasts and epithelial cells treated with ZA. Analysis of these in vitro data may explain the positive in vivo effects of LLLT applied to osteonecrosis lesions. © 2013 Astro Ltd.

Laser stimulated light reflection for TeO2-WO 3-Bi2O3 thin films with incorporated Si nanoparticles

A novel method of preparation of the Si nanoparticles (NPs) incorporated in tellurite TeO2-WO3-Bi2O3 (TWB) thin films is proposed. This mew method applies RF magnetron sputtering technique at room temperature. The incorporation of Si NP was confirmed by transmission electron microscopy (TEM); isolated Si NPs with diameters of around 6 nm are observed. Energy dispersive X-ray spectroscopy (EDS) was performed during TEM analysis in order to confirm the presence of Si NP and also the other elements of the thin film. The thin films are explored with respect to the photoinduced changes of the reflectivity within the 400-65 nm spectra range using a 10 ns pulsed Nd:YAG with power densities varying up to 400 MW/cm2 and beam diameter within the 3-5 mm range. The observed processes are analyzed within a framework of trapping level conceptions for the Si NP. The possible application of the discovered materials as optical sensitive sensors is proposed. © 2013 Elsevier B.V.

Avaliação do tratamento térmico em recobrimentos cerâmicos bioativos pelo método biomimético sobre titânio c.p. modificados pelo laser Nd:YAG

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Recobrimentos cerâmicos bioativos pelo processo sol-gel sobre Ti c.p. modificado por laser empregados em implantes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Soldagem em laminas finas de hastelloy c-276 por laser pulsado Nd:YAG

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Random laser action from flexible biocellulose-based device

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Laser stimulated piezoelectricity in Er3+ doped GeO2-Bi2O3 glasses containing silicon nanocrystals

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Implantes nanotopograficamente modificados pela ação do laser Yb-YAG

Titanium has proven its suitability as an implant material in surgery over many years. Excellent biocompatibility and corrosion resistance are outstanding features. Implant surfaces always causes concern and interest in scientific communities, due to its close relationship with the time required for osseointegration. Surface modification can be performed by several methods, being laser irradiation one of them. Titanium implants with two different surfaces were inserted in rabbits: Group I (G-I: machined surface, control group), and group II (G-II: laser irradiated, test group) being processed 30 and 60 days after surgery for histological analysis. Surface characterization was performed with SEM-EDS, contact angle measurement, and mean roughness (Ra) parameters. Surface analysis in the GII group showed a nanomorphology affected by melt and quick solidification zones following laser irradiation (SEM), as well as total wettability and Ra mean values significantly higher than in the G-I group. The laser treatment resulted in a homogenized, porous surface, with increased surface area and volume. Histological analysis of bone-implant contact linear extension (BIC) showed better results in G-II at 30 days (39.26 ± 18.23 and 68.41 ± 13.68 for G-I and G-II groups, respectively). Titanium implants modified by laser irradiation showed important features that may accelerate early osseointegration.

Can an LED-laser hybrid light help to decrease hydrogen peroxide concentration while maintaining effectiveness in teeth bleaching?

The aim of this study was to compare the bleaching efficacy of 35% hydrogen peroxide and 15% hydrogen peroxide with nitrogen-doped titanium dioxide catalysed by an LED-laser hybrid light. We studied 70 patients randomized to two groups. Tooth shade and pulpal sensitivity were registered. Group 1: 15% hydrogen peroxide with nitrogen-doped titanium dioxide. Group 2: 35% hydrogen peroxide. Both groups were activated by an LED-laser light. No significant differences were seen in shade change immediately, one week or one month after treatment (p > 0.05). Differences were seen in pulpal sensitivity (p < 0.05). The use of an LED-laser hybrid light to activate 15% hydrogen peroxide gel with N_TiO2 permits decreasing the peroxide concentration with similar aesthetic results and less pulpal sensitivity than using 35% hydrogen peroxide for bleaching teeth.

High final energy of low-level gallium arsenide laser therapy enhances skeletal muscle recovery without a positive effect on collagen remodeling

The aim of this study was to evaluate the effects of a Gallium Arsenide (GaAs) laser, using a high final energy of 4.8J, during muscle regeneration after cryoinjury. Thirty Wistar rats were divided into three groups: Control (C, n=10); Injured (I, n=10) and Injured and laser treated (Injured/LLLT, n=10). The cryoinjury was induced in the central region of the tibialis anterior muscle (TA). The applications of the laser (904nm, 50mW average power) were initiated 24h after injury, at energy density of 69Jcm(-1) for 48s, for 5days, to two points of the lesion. Twenty-four hours after the final application, the TA muscle was removed and frozen in liquid nitrogen to assess the general muscle morphology and the gene expression of TNF-, TGF-, MyoD, and Myogenin. The Injured/LLLT group presented a higher number of regenerating fibers and fewer degenerating fibers (P<0.05) without changes in the collagen remodeling. In addition, the Injured/LLLT group presented a significant decrease in the expression of TNF- and myogenin compared to the injured group (P<0.05). The results suggest that the GaAs laser, using a high final energy after cryoinjury, promotes muscle recovery without changing the collagen remodeling in the muscle extracellular matrix.

Reparo ósseo em scaffolds de TI6AL4V sinterizados pela tecnologia de sinterização direta de metais a laser (DMLS) submetidos a tratamento de superfície associado à aplicação de ultrassom de baixa intensidade (LIPUS)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo clínico-histológico da quelite actímica crônica tratada por dois protocolos de laser de CO2 de baixa morbidade

Objetivo: Este ensaio clínico-histológico teve por meta avaliar a resposta terapêutica de dois protocolos de reconhecida baixa morbidade em passagem única. Métodos: Pacientes com queilite actínica crônica multicêntrica (n=40) comprovada pela microscopia foram randomicamente submetidos a dois protocolos de laser de CO2 pulsátil através de modelo comparativo bilateral (protocolo de pulsos de 350 mJ, 3,5 W, amplitude de 0,1s versus protocolo de pulsos de 250 mJ, 5 W, amplitude de 0,05s). Realizou-se em 26 pacientes análise comparativa dos níveis de atipia epitelial de espécimes de biópsia entre o status quo e o período pós-operatório de ambos os protocolos e entre si. Foram avaliados outros fenômenos do espectro da doença. Resultados: Houve presença clínica pós-operatória de lesões em 10% dos pacientes para cada protocolo e uma significante redução dos níveis de atipia epitelial (p<0,001), por vezes completa. Conclusão: Não houve diferença de resultados entre os protocolos estudados (p> 0,05).

Time-of-flight two-photon photoemission spectromicroscopy with femtosecond laser radiation

Time-of-flight photoemission spectromicroscopy was used to measure and compare the two-photon photoemission (2PPE) spectra of Cu and Ag nanoparticles with linear dimensions ranging between 40 nm and several 100 nm, with those of the corresponding homogeneous surfaces. 2PPE was induced employing femtosecond laser radiation from a frequency-doubled Ti:sapphire laser in the spectral range between 375 nm and 425 nm with a pulse width of 200 fs and a repetition rate of 80 MHz. The use of a pulsed radiation source allowed us to use a high-resolution photoemission electron microscope as imaging time-of-flight spectrometer, and thus to obtain spectroscopic information about the laterally resolved electron signal. Ag nanoparticle films have been deposited on Si(111) by electron-beam evaporation, a technique leading to hemispherically-shaped Ag clusters. Isolated Cu nanoparticles have been generated by prolonged heating of a polycrystalline Cu sample. If compared to the spectra of the corresponding homogeneous surfaces, the Cu and Ag nanoparticle spectra are characterized by a strongly enhanced total 2PPE yield (enhancement factor up to 70), by a shift (about 0.1 eV) of the Fermi level onset towards lower final state energies, by a reduction of the work function (typically by 0.2 eV) and by a much steeper increase of the 2PPE yield towards lower final state energies. The shift of the Fermi level onset in the nanoparticle spectra has been explained by a positive unit charge (localized photohole) residing on the particle during the time-scale relevant for the 2PPE process (few femtoseconds). The total 2PPE yield enhancement and the different overall shape of the spectra have been explained by considering that the laser frequency was close to the localized surface plasmon resonance of the Cu and Ag nanoparticles. The synchronous oscillations induced by the laser in the metal electrons enhance the near-zone (NZ) field, defined as the linear superposition of the laser field and the field produced in the vicinity of the particles by the forced charge oscillations. From the present measurements it is clear that the NZ field behavior is responsible for the 2PPE enhancement and affects the 2PPE spatial and energy distribution and its dynamics. In particular, its strong spatial dependence allows indirect transitions through real intermediate states to take place in the metal clusters. Such transitions are forbidden by momentum conservation arguments and are thus experimentally much less probable on homogeneous surfaces. Further, we investigated specially tailored moon-shaped small metal nanostructures, whose NZ field was theoretically predicted, and compared the calculation with the laterally resolved 2PPE signal. We could show that the 2PPE signal gives a clear fingerprint of the theoretically predicted spatial dependence of the NZ field. This potential of our method is highly attractive in the novel field of plasmonics.

High-Speed Laser Processing of Thin Single and Multi-Layer Films

Theoretical models are developed for the continuous-wave and pulsed laser incision and cut of thin single and multi-layer films. A one-dimensional steady-state model establishes the theoretical foundations of the problem by combining a power-balance integral with heat flow in the direction of laser motion. In this approach, classical modelling methods for laser processing are extended by introducing multi-layer optical absorption and thermal properties. The calculation domain is consequently divided in correspondence with the progressive removal of individual layers. A second, time-domain numerical model for the short-pulse laser ablation of metals accounts for changes in optical and thermal properties during a single laser pulse. With sufficient fluence, the target surface is heated towards its critical temperature and homogeneous boiling or "phase explosion" takes place. Improvements are seen over previous works with the more accurate calculation of optical absorption and shielding of the incident beam by the ablation products. A third, general time-domain numerical laser processing model combines ablation depth and energy absorption data from the short-pulse model with two-dimensional heat flow in an arbitrary multi-layer structure. Layer removal is the result of both progressive short-pulse ablation and classical vaporisation due to long-term heating of the sample. At low velocity, pulsed laser exposure of multi-layer films comprising aluminium-plastic and aluminium-paper are found to be characterised by short-pulse ablation of the metallic layer and vaporisation or degradation of the others due to thermal conduction from the former. At high velocity, all layers of the two films are ultimately removed by vaporisation or degradation as the average beam power is increased to achieve a complete cut. The transition velocity between the two characteristic removal types is shown to be a function of the pulse repetition rate. An experimental investigation validates the simulation results and provides new laser processing data for some typical packaging materials.

Laser driven proton acceleration and beam shaping

In the race to obtain protons with higher energies, using more compact systems at the same time, laser-driven plasma accelerators are becoming an interesting possibility. But for now, only beams with extremely broad energy spectra and high divergence have been produced. The driving line of this PhD thesis was the study and design of a compact system to extract a high quality beam out of the initial bunch of protons produced by the interaction of a laser pulse with a thin solid target, using experimentally reliable technologies in order to be able to test such a system as soon as possible. In this thesis, different transport lines are analyzed. The first is based on a high field pulsed solenoid, some collimators and, for perfect filtering and post-acceleration, a high field high frequency compact linear accelerator, originally designed to accelerate a 30 MeV beam extracted from a cyclotron. The second one is based on a quadruplet of permanent magnetic quadrupoles: thanks to its greater simplicity and reliability, it has great interest for experiments, but the effectiveness is lower than the one based on the solenoid; in fact, the final beam intensity drops by an order of magnitude. An additional sensible decrease in intensity is verified in the third case, where the energy selection is achieved using a chicane, because of its very low efficiency for off-axis protons. The proposed schemes have all been analyzed with 3D simulations and all the significant results are presented. Future experimental work based on the outcome of this thesis can be planned and is being discussed now.