Temperature rise in cavities prepared by high and low torque handpieces and Er : YAG laser

Objective The aim of this study was to compare intrapulpal temperature increases produced by a high-speed high-torque (speed-increasing) handpiece, a high-speed low-torque handpiece (air-turbine) and an Er: YAG (Erbium: Yttrium-Aluminum-Garnet) laser. Subject and methods Thirty bovine incisors were reduced to a dentine thickness of 2.0 mm. Class V preparations were prepared to a depth of 1.5 mm, measured with a caliper or by a mark on the burs. A thermocouple was placed inside the pulp chamber to determine temperature increases (C). Analysis was performed on the following groups (n = 10) treated with: G1, low-torque handpiece; G2, high-torque handpiece; and G3, Er: YAG laser (2.94 mu m at 250 mJ/4 Hz), all with water cooling. The temperature increases were recorded with a computer linked to the thermocouples. Results The data were submitted to ANOVA and Tukey statistical test. The average temperature rises were: 1.92 +/- 0.80 degrees C for G1, 1.34 +/- 0.86 degrees C for G2, and 0.75 +/- 0.39 degrees C for G3. There were significant statistical differences among the groups (p = 0.095). All the groups tested did not have a change of temperature that exceeds the threshold of 5.5 degrees C. Conclusion Temperature response to the low and high torque handpieces seemed to be similar, however the Er: YAG laser generated a lower temperature rise.

Nd:YAG Laser Irradiation effect on apical intracanal dentin-a microleakage and SEM evaluation

The purpose of this in vitro study was to evaluate the effect of neodymium:yttrium-aluminum-garnet (Nd:YAG) laser irradiation on intracanal dentin surface by SEM analysis and its interference in the apical seal of filled canals. After endodontic treatment procedures, 34 maxillary human incisors were randomly assigned to 2 groups. In the negative control group (n=17), no additional treatment was performed and teeth were filled with vertically condensed gutta-percha; in the laser-treated group (n=17), the root canals were irradiated with Nd:YAG laser (1.5 W, 100 mJ, 15 Hz) before filling as described for the control group. Two specimens of each group were prepared for SEM analysis to evaluate the presence and extent of morphological changes and removal of debris; the other specimens were immersed in 0.5% methylene blue dye (pH 7.2) for 24 h for evaluation of the linear dye leakage at the apical third. SEM analysis of the laser-treated group showed dentin fusion and resolidification without smear layer or debris. The Student's t-test showed that the laser-treated group had significantly less leakage in apical third than the control group. Within the limitations of this study, it may be concluded that the morphological changes on the apical intraradicular dentin surface caused by Nd:YAG laser resulted in less linear dye apical leakage.

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

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effects of laser beam energy on the pulsed Nd:YAG laser welding of thin sheet corrosion resistant materials

The aim of this study was to value the possibility to join, for pulsed Nd:YAG laser welding, thin foils lap joints for sealing components in corrosive environment. Experimental investigations were carried out using a pulsed neodymium: yttrium aluminum garnet laser weld to examine the influence of the pulse energy in the characteristics of the weld fillet. The pulse energy was varied from 1.0 to 2.5 J at increments of 0.25 J with a 4 ms pulse duration. The base materials used for this study were AISI 316L stainless steel and Ni-based alloys foils with 100 mu m thickness. The welds were analyzed by electronic and optical microscopy, tensile shear tests and micro hardness. The results indicate that pulse energy control is of considerable importance to thin foil weld quality because it can generate good mechanical properties and reduce discontinuities in weld joints. The ultimate tensile strength of the welded joints increased at first and then decreased as the pulse energy increased. In all the specimens, fracture occurred in the top foil heat-affected zone next to the fusion line. The microhardness was almost uniform across the parent metal, HAZ and weld metal. A slight increase in the fusion zone and heat-affected zone compared to those measured in the base metal was observed. This is related to the microstructural refinement in the fusion zone, induced by rapid cooling of the laser welding. The process appeared to be very sensitive to the gap between couples.

Treatment of periodontal disease with an Er,Cr:YSGG laser in rats exposed to cigarette smoke inhalation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Longitudinal evaluation of bond strength to enamel of dental adhesive systems associated with Nd:YAG laser

Objectives: This study evaluated the durability of bond strength to enamel using total-etch (Single Bond/SB) and self-etch (Clearfil SE Bond/CSEB) adhesives associated with neody-mium: yttrium-aluminu- garnet (Nd:YAG) laser irradiation through the uncured adhesives.Methods: Bovine incisors were worn to expose an area of enamel and were divided into four groups: group 1 (control) SB + polymerization; group 2 (control) CSEB + polymerization; group 3 (laser) - B + Nd:YAG laser (174.16 J/cm(2)) + polymerization; and group 4 (laser) CSEB + Nd:YAG (174.16 J/cm(2)) + polymerization. Blocks of composite were fabricated and stored for 24 hours or 12 months, sectioned into beams, and submitted to microtensile tests. Results were analyzed by three-way analysis of variance (ANOVA) (adhesive, technique, and storage time) and Tukey tests.Results: ANOVA revealed significant differences for adhesive 3 technique and technique 3 storage time (p<0.05). The mean values (MPa) for interaction adhesive x technique (standard deviation) were as follows: SB/control = 35.78 (6.04)a; SB/laser = 26.40 (7.25)b, CSEB/control = 26.32 (5.71)b, CSEB/laser = 23.90 (7.49)b. For interaction technique x storage time the mean values were as follows: control/24 hours = 32.58 (6.49)a; control/12 months = 29.52 (8.38)a; laser/24 hours = 29.37 (5.71)a; laser/12 months = 20.92 (6.5)b. Groups with the same letters showed no statistically significant differences.Conclusion: Scanning electron microscope analysis showed evident areas of micromorphological alterations in lased samples after 12 months of water storage. Nd: YAG laser irradiation of enamel through unpolymerized totaletch adhesive significantly reduced bond strength compared with the control. Bond strength decreased when enamel samples irradiated with Nd: YAG laser through unpolymerized adhesives were stored in water for 12 months.

Comparison of Laser Versus Sclerotherapy in the Treatment of Lower Extremity Telangiectases: A Prospective Study

BACKGROUND Lower extremity telangiectasia affects approximately 40% of women. The demand for aesthetic treatment of these veins continues to grow. Few studies have compared laser and sclerotherapy to treat leg telangiectasias. OBJECTIVE To compare the efficacy of conventional sclerotherapy and neodymium-doped yttrium aluminum garnet (Nd:YAG) laser in the treatment of leg telangiectasias. METHODS AND MATERIALS Thirty women were enrolled in the study. One leg was randomly assigned laser treatment and the other sclerotherapy with 75% glucose solution. All patients were photographed before and after treatment. The applying physician and two independent observers rated photographic improvement of the treated areas. Complications and adverse effects were noted during follow-up. Patients answered a questionnaire that addressed pain, clearing of the vessels, and satisfaction with the results. RESULTS There was a significant difference between the modes of treatment regarding pain. Twelve patients using laser and 16 using sclerotherapy considered the clearing of the vessels to be good to excellent after three sessions of both laser and scleratherapy. Mean scores after photographic assessment were 7.9 for laser and 7.0 for sclerotherapy. CONCLUSION Lower extremity telangiectases may be treated equally well using Nd:YAG 1064-nm laser or conventional sclerotherapy.

Single-shot electron bunch length measurements using a spatial electro-optical autocorrelation interferometer

A spatial, electro-optical autocorrelation (EOA) interferometer using the vertically polarized lobes of coherent transition radiation (CTR) has been developed as a single-shot electron bunch length monitor at an optical beam port downstream the 100 MeV preinjector LINAC of the Swiss Light Source. This EOA monitor combines the advantages of step-scan interferometers (high temporal resolution) [D. Mihalcea et al., Phys. Rev. ST Accel. Beams 9, 082801 (2006) and T. Takahashi and K. Takami, Infrared Phys. Technol. 51, 363 (2008)] and terahertz-gating technologies [U. Schmidhammer et al., Appl. Phys. B: Lasers Opt. 94, 95 (2009) and B. Steffen et al., Phys. Rev. ST Accel. Beams 12, 032802 (2009)] (fast response), providing the possibility to tune the accelerator with an online bunch length diagnostics. While a proof of principle of the spatial interferometer was achieved by step-scan measurements with far-infrared detectors, the single-shot capability of the monitor has been demonstrated by electro-optical correlation of the spatial CTR interference pattern with fairly long (500 ps) neodymium-doped yttrium aluminum garnet (Nd:YAG) laser pulses in a ZnTe crystal. In single-shot operation, variations of the bunch length between 1.5 and 4 ps due to different phase settings of the LINAC bunching cavities have been measured with subpicosecond time resolution.

Planar magneto-photonic and gradient-photonic structures : crystals and metamaterials.

In the field of photonics, two new types of material structures, photonic crystals and metamaterials, are presently of great interest. Both are studied in the present work, which focus on planar magnetic materials in the former and planar gradient metamaterials in the latter. These planar periodic structures are easy to handle and integrate into optical systems. The applications are promising field for future optical telecommunication systems and give rise to new optical, microwave and radio technologies. The photonic crystal part emphasizes the utilization of magnetic material based photonic crystals due to its remarkable magneto-optical characteristics. Bandgaps tuning by magnetic field in bismuth-gadolinium-substituted lutetium iron garnet (Bi0.8 Gd0.2 Lu2.0 Fe5 O12) based one- dimensional photonic crystals are investigated and demonstrated in this work. Magnetic optical switches are fabricated and tested. Waveguide formulation for band structure in magneto photonic crystals is developed. We also for the first time demonstrate and test two- dimensional magneto photonic crystals optical. We observe multi-stopbands in two- dimensional photonic waveguide system and study the origin of multi-stopbands. The second part focus on studying photonic metamaterials and planar gradient photonic metamaterial design. We systematically study the effects of varying the geometry of the fishnet unit cell on the refractive index in optical frequency. It is the first time to design and demonstrate the planar gradient structure in the high optical frequency. Optical beam bending using planar gradient photonic metamaterials is observed. The technologies needed for the fabrication of the planar gradient photonic metamaterials are investigated. Beam steering devices, shifter, gradient optical lenses and etc. can be derived from this design.

MAGNETO-PHOTONIC CRYSTALS FOR OPTICAL SENSING APPLICATIONS

Among the optical structures investigated for optical sensing purpose, a significant amount of research has been conducted on photonic crystal based sensors. A particular advantage of photonic crystal based sensors is that they show superior sensitivity for ultra-small volume sensing. In this study we investigate polarization changes in response to the changes in the cover index of magneto-optic active photonic band gap structures. One-dimensional photonic-band gap structures fabricated on iron garnet materials yield large polarization rotations at the band gap edges. The enhanced polarization effects serve as an excellent tool for chemical sensing showing high degree of sensitivity for photonic crystal cover refractive index changes. The one dimensional waveguide photonic crystals are fabricated on single-layer bismuth-substituted rare earth iron garnet films ((Bi, Y, Lu)3(Fe, Ga)5O12 ) grown by liquid phase epitaxy on gadolinium gallium garnet substrates. Band gaps have been observed where Bragg scattering conditions links forward-going fundamental waveguide modes to backscattered high-order waveguide modes. Large near-band-edge polarization rotations which increase progressively with backscattered-mode order have been experimentally demonstrated for multiple samples with different composition, film thickness and fabrication parameters. Experimental findings are supported by theoretical analysis of Bloch modes polarization states showing that large near stop-band edge rotations are induced by the magneto-photonic crystal. Theoretical and experimental analysis conducted on polarization rotation sensitivity to waveguide photonic crystal cover refractive index changes shows a monotonic enhancement of the rotation with cover index. The sensor is further developed for selective chemical sensing by employing Polypyrrole as the photonic crystal cover layer. Polypyrrole is one of the extensively studied conducting polymers for selective analyte detection. Successful detection of aqueous ammonia and methanol has been achieved with Polypyrrole deposited magneto-photonic crystals.

Treatment of lower extremity telangiectasias in women by foam sclerotherapy vs. Nd:YAG laser: a prospective, comparative, randomized, open-label trial.

BACKGROUND Telangiectasias of the lower extremities are very common. There are no blinded, randomized, controlled clinical trials comparing laser modalities with the gold standard sclerotherapy, while the few available studies encompass small patients cohorts. OBJECTIVE This prospective, randomized, open-label trial compares the efficacy of sclerotherapy with polidocanol vs. long-pulsed neodymium-doped yttrium aluminium garnet (Nd:YAG) laser in the treatment of leg telangiectasias. PATIENTS AND METHODS Fifty-six female patients with primary leg telangiectasias and reticular veins (C1A or S Ep AS 1 PN ) were included in the study. One leg was randomly assigned to get treatment with the multiple synchronized long-pulsed Nd:YAG laser, while the other received foam sclerotherapy with polidocanol 0.5%. The patients were treated in two sessions at intervals of 6 weeks. The patients were evaluated by the handling physician after 6 weeks and 6 months. Two investigators assessed blindly at the end of the study the photographs for clearing of the vessels using a six-point scale from 1 (no change) to 6 (100% cleared). Patients reported about pain sensation and outcome satisfaction. RESULTS According to the handling dermatologist, at the last follow-up, there was an improvement of 30-40% with a median of 3 (IQR 2) and a good improvement of 50-70% with a median of 4 (IQR 2) after laser treatment and sclerotherapy respectively. In contrast, according to the blinded investigators, there was a median of 5 (IQR 1) with a very good improvement of >70% after both therapies. Improvement was achieved more quickly by sclerotherapy, although at the last follow-up visit there was no difference in clearance between the two groups as assessed by the blinded experts (P-value 0.84). The degree of patient's satisfaction was very good and similar with both therapeutic approaches. There was a significant difference (P-value 0.003) regarding pain perception between the types of therapy. Laser was felt more painful than sclerotherapy. CONCLUSION Telangiectasias of the lower extremities can be successfully treated with either synchronized long-pulsed Nd:YAG laser or sclerotherapy. The 1064-nm long-pulsed Nd:YAG laser is associated with more pain and is suitable especially in case of needle phobia, allergy to sclerosants and in presence of small veins with telangiectatic matting, while sclerotherapy can also treat the feeder veins.

Periodontal and peri-implant wound healing following laser therapy

Laser irradiation has numerous favorable characteristics, such as ablation or vaporization, hemostasis, biostimulation (photobiomodulation) and microbial inhibition and destruction, which induce various beneficial therapeutic effects and biological responses. Therefore, the use of lasers is considered effective and suitable for treating a variety of inflammatory and infectious oral conditions. The CO2 , neodymium-doped yttrium-aluminium-garnet (Nd:YAG) and diode lasers have mainly been used for periodontal soft-tissue management. With development of the erbium-doped yttrium-aluminium-garnet (Er:YAG) and erbium, chromium-doped yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers, which can be applied not only on soft tissues but also on dental hard tissues, the application of lasers dramatically expanded from periodontal soft-tissue management to hard-tissue treatment. Currently, various periodontal tissues (such as gingiva, tooth roots and bone tissue), as well as titanium implant surfaces, can be treated with lasers, and a variety of dental laser systems are being employed for the management of periodontal and peri-implant diseases. In periodontics, mechanical therapy has conventionally been the mainstream of treatment; however, complete bacterial eradication and/or optimal wound healing may not be necessarily achieved with conventional mechanical therapy alone. Consequently, in addition to chemotherapy consisting of antibiotics and anti-inflammatory agents, phototherapy using lasers and light-emitting diodes has been gradually integrated with mechanical therapy to enhance subsequent wound healing by achieving thorough debridement, decontamination and tissue stimulation. With increasing evidence of benefits, therapies with low- and high-level lasers play an important role in wound healing/tissue regeneration in the treatment of periodontal and peri-implant diseases. This article discusses the outcomes of laser therapy in soft-tissue management, periodontal nonsurgical and surgical treatment, osseous surgery and peri-implant treatment, focusing on postoperative wound healing of periodontal and peri-implant tissues, based on scientific evidence from currently available basic and clinical studies, as well as on case reports.

Evaluation of different types of enamel conditioning before application of a fissure sealant

The aim of the study was to compare fissure sealant quality after mechanical conditioning of erbium-doped yttrium aluminium garnet (Er:YAG) laser or air abrasion prior to chemical conditioning of phosphoric acid etching or of a self-etch adhesive. Twenty-five permanent molars were initially divided into three groups: control group (n = 5), phosphoric acid etching; test group 1 (n = 10), air abrasion; and test group 2, (n = 10) Er:YAG laser. After mechanical conditioning, the test group teeth were sectioned buccolingually and the occlusal surface of one half tooth (equal to one sample) was acid etched, while a self-etch adhesive was applied on the other half. The fissure system of each sample was sealed, thermo-cycled and immersed in 5% methylene dye for 24 h. Each sample was sectioned buccolingually, and one slice was analysed microscopically. Using specialized software microleakage, unfilled margin, sealant failure and unfilled area proportions were calculated. A nonparametric ANOVA model was applied to compare the Er:YAG treatment with that of air abrasion and the self-etch adhesive with phosphoric acid (α = 0.05). Test groups were compared to the control group using Wilcoxon rank sum tests (α = 0.05). The control group displayed significantly lower microleakage but higher unfilled area proportions than the Er:YAG laser + self-etch adhesive group and displayed significantly higher unfilled margin and unfilled area proportions than the air-abrasion + self-etch adhesive group. There was no statistically significant difference in the quality of sealants applied in fissures treated with either Er:YAG laser or air abrasion prior to phosphoric acid etching, nor in the quality of sealants applied in fissures treated with either self-etch adhesive or phosphoric acid following Er:YAG or air-abrasion treatment.