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.

Cutaneous Collagenous Vasculopathy: A Rare Form of Microangiopathy Successfully Treated with a Combination of Multiplex Laser and Optimized Pulsed Light with a Review of the Literature.

Cutaneous collagenous vasculopathy (CCV) is a rare idiopathic microangiopathy of the cutaneous vasculature characterized histologically by the presence of dilated small blood vessels with flat endothelial cells and thickened walls containing hyaline material in the upper dermis. We report an elderly patient presenting with an extensive form of CCV involving the trunk, upper and lower limbs. She was treated with Multiplex PDL 595-nm/Nd:YAG 1,064-nm laser and optimized pulsed light. This approach, which has never been reported for CCV so far, resulted in a striking and almost complete clearance of the widespread lesions. We here review our knowledge about CCV and therapeutic options available with a survey of the literature.

Evaluation of the Morphological Characteristics of Laser-Irradiated Dentin

OBJECTIVE The aim of this study was to investigate the effect of different energy settings of Er:YAG laser irradiation on dentin surface morphology with respect to the number of opened dentinal tubules. BACKGROUND DATA An ideally prepared dentin surface with opened dentinal tubules is a prerequisite for adhesive fixation. No study, however, has yet compared the numbers of opened dentinal tubules with regard to statistical differences. METHODS Conventional preparations using a bur with or without additional acid etching acted as control groups. Dentin specimens were prepared from human third molars and randomly divided into eight groups according to the energy settings of the laser (1, 1.5, 4, 6, 7.5, and 8 W) and two controls (bur and bur plus acid etching). After surface preparation, dentin surfaces were analyzed with a scanning electron microscope, and the number of opened dentinal tubules in a defined area was counted. RESULTS The control groups showed smooth surfaces with (bur plus acid etching) and without opened dentinal tubules (bur), whereas all laser-irradiated surfaces showed rough surfaces. Using the energy setting of 4 W resulted in significantly more opened dentinal tubules than the conventional preparation technique using the bur with additional acid etching. In contrast, the energy setting of 8 W showed significantly fewer opened dentinal tubules, and also exhibited signs of thermal damage. CONCLUSIONS The Er:YAG laser with an energy setting of 4 W generates a dentin surface with opened dentinal tubules, a prerequisite for adhesive fixation.

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.

Chemical composition of waters from the Black Sea

Concentrations of sulfate ions at three depths in the water column of the Black Sea were studied during cruises of the GOIN (State Oceanographic Institute) Sevastopol' Division in 1983 and 1985. Results were compared with data from earlier studies. Obtained data indicate pronounced lateral and temporal variation in the SO4/Cl ratio.

Measured Stark widths of several spectral lines of Pb III

The Stark full widths at half of the maximal line intensity (FWHM, ω) have been measured for 25 spectrallines of PbIII (15 measured for the first time) arising from the 5d106s8s, 5d106s7p, 5d106s5f and 5d106s5g electronic configurations, in a lead plasma produced by ablation with a Nd:YAG laser. The optical emission spectroscopy from a laser-induced plasma generated by a 10 640 Å radiation, with an irradiance of 2 × 1010 W cm− 2 on a lead target (99.99% purity) in an atmosphere of argon was analysed in the wavelength interval between 2000 and 7000 Å. The broadening parameters were obtained with the target placed in argon atmosphere at 6 Torr and 400 ns after each laser light pulse, which provides appropriate measurement conditions. A Boltzmann plot was used to obtain the plasma temperature (21,400 K) and published values of the Starkwidths in Pb I, Pb II and PbIII to obtain the electron number density (7 × 1016 cm− 3); with these values, the plasma composition was determined by means of the Saha equation. Local Thermodynamic Equilibrium (LTE) conditions and plasma homogeneity has been checked. Special attention was dedicated to the possible self-absorption of the different transitions. Comparison of the new results with recent available data is also presented.

Development of Robotized Laser Welding Applications for Joining Thin Sheets

Laser Welding (LW) is more often used in manufacturing due to its advantages, such as accurate control, good repeatability, less heat input, opportunities for joining of special materials, high speed, capability to join small dimension parts etc. LW is dedicated to robotized manufacturing, and the fabrication cells are using various level of flexibility, from specialized robots to very flexible setups. This paper features several LW applications using two industrially-scaled manufacturing cells at UPM Laser Centre (CLUPM) of Polytechnical University of Madrid (Universidad Politécnica de Madrid). The one dedicated to Remote Laser Welding (RLW) of thin sheets for automotive and other sectors uses a CO2 laser of 3500 W. The second has a high flexibility, is based on a 6-axis ABB robot and a Nd:YAG laser of 3300 W, and is meant for various laser processing methods, including welding. After a short description of each cell, several LW applications experimented at CLUPM and recently implemented in industry are briefly presented: RLW of automotive coated sheets, LW of high strength automotive sheets, LW vs. laser hybrid welding (LHW) of Double Phase steel thin sheets, and LHW of thin sheets of stainless steel and carbon steel (dissimilar joints). The main technological issues overcame and the critical process parameters are pointed out. Conclusions about achievements and trends are provided.

Laser shock peening without absorbent coating (LSPwC) effect on 3D surface topography and mechanical properties of 6082-T651 Al alloy

The influence of nanosecond laser pulses applied by laser shock peening without absorbent coating (LSPwC) with a Q-switched Nd:YAG laser operating at a wavelength of λ = 1064 nm on 6082-T651 Al alloy has been investigated. The first portion of the present study assesses laser shock peening effect at two pulse densities on three-dimensional (3D) surface topography characteristics. In the second part of the study, the peening effect on surface texture orientation and micro-structure modification, i.e. the effect of surface craters due to plasma and shock waves, were investigated in both longitudinal (L) and transverse (T) directions of the laser-beam movement. In the final portion of the study, the changes of mechanical properties were evaluated with a residual stress profile and Vickers micro-hardness through depth variation in the near surface layer, whereas factorial design with a response surface methodology (RSM) was applied. The surface topographic and micro-structural effect of laser shock peening were characterised with optical microscopy, InfiniteFocus® microscopy and scanning electron microscopy (SEM). Residual stress evaluation based on a hole-drilling integral method confirmed higher compression at the near surface layer (33 μm) in the transverse direction (σmin) of laser-beam movement, i.e. − 407 ± 81 MPa and − 346 ± 124 MPa, after 900 and 2500 pulses/cm2, respectively. Moreover, RSM analysis of micro-hardness through depth distribution confirmed an increase at both pulse densities, whereas LSPwC-generated shock waves showed the impact effect of up to 800 μm below the surface. Furthermore, ANOVA results confirmed the insignificant influence of LSPwC treatment direction on micro-hardness distribution indicating essentially homogeneous conditions, in both L and T directions.

Superplastic deformation of directionally solidified nanofibrillar Al2O3-Y3Al5O12-ZrO2 eutectics

Nanofibrillar Al2O3–Y3Al5O12–ZrO2 eutectic rods were manufactured by directional solidification from the melt at high growth rates in an inert atmosphere using the laser-heated floating zone method. Under conditions of cooperative growth, the ternary eutectic presented a homogeneous microstructure, formed by bundles of single-crystal c-oriented Al2O3 and Y3Al5O12 (YAG) whiskers of ≈100 nm in width with smaller Y2O3-doped ZrO2 (YSZ) whiskers between them. Owing to the anisotropic fibrillar microstructure, Al2O3–YAG–YSZ ternary eutectics present high strength and toughness at ambient temperature while they exhibit superplastic behavior at 1600 K and above. Careful examination of the deformed samples by transmission electron microscopy did not show any evidence of dislocation activity and superplastic deformation was attributed to mass-transport by diffusion within the nanometric domains. This combination of high strength and toughness at ambient temperature together with the ability to support large deformations without failure above 1600 K is unique and shows a large potential to develop new structural materials for very high temperature structural applications.

Residual stress distribution in ferritic-austenitic steel joints made by laser welding

The present investigation addresse the influence of laser welding process-ing parameters used for joining dis-similar metals (ferritic to austenitic steel), on the induced residual stress field. Welding was performed on a Nd:YAG laser DY033 (3300 W) in a continuous wave (CW), keyhole mode. The base metals (BM) employed in this study are AISI 1010 carbon steel (CS) and AISI 304L austenitic stainless steel (SS). Pairs of dissimilar plates of 200 mm x 45 mm x 3 mm were butt joined by laser welding. Different sets of parameters were used to engineer the base metals apportionment at joint formation, namely distinct dilution rates. Residual strain scanning, carried out by neutron diffraction was used to assess the joints. Through-thickness residual stress maps were determined for the laser welded samples of dis-similar steels using high spatial reso-lution. As a result, an appropriate set of processing parameters, able to mi-nimize the local tensile residual stress associated to the welding process, was found.

Overall vs. local mechanical behaviour of ferritic austenitic steel joints made by laser welding

The present investigation addresses the overall and local mechanical performance of dissimilar joints of low carbon steel (CS) and stainless Steel (SS) thin sheets achieved by laser welding in case of heat source displacement from the weld gap centreline towards CS. Welding was performed on a Nd:YAG laser DY033 (3300 W) in a continuos wave (CW), keyhole mode. The tensile behavior of the joint different zones assessed by using a video-image based system (VIC-2D) reveals that the residual stress field, together with the positive difference in yield between the weld metal and the base materials protects the joint from being plastically deformed. The tensile loadings of flat transverse specimens generate the strain localization and failure in CS, far away from the weld.

Thermoelectric assessment of laser peening induced effects on a metallic biomedical Ti6Al4V

Laser peening has recently emerged as a useful technique to overcome detrimental effects associated to another well-known surface modification processes such as shot peening or grit blasting used in the biomedical field. It is worth to notice that besides the primary residual stress effect, thermally induced effects might also cause subtle surface and subsurface microstructural changes that might influence corrosion resistance. Moreover, since maximum loads use to occur at the surface, they could also play a critical role in the fatigue strength. In this work, plates of Ti-6Al-4V alloy of 7 mm in thickness were modified by laser peening without using a sacrificial outer layer. Irradiation by a Q-switched Nd-YAG laser (9.4 ns pulse length) working in fundamental harmonic at 2.8 J/pulse and with water as confining medium was used. Laser pulses with a 1.5 mm diameter at an equivalent overlapping density (EOD) of 5000 cm-2 were applied. Attempts to analyze the global induced effects after laser peening were addressed by using the contacting and non-contacting thermoelectric power (TEP) techniques. It was demonstrated that the thermoelectric method is entirely insensitive to surface topography while it is uniquely sensitive to subtle variations in thermoelectric properties, which are associated with the different material effects induced by different surface modification treatments. These results indicate that the stress-dependence of the thermoelectric power in metals produces sufficient contrast to detect and quantitatively characterize regions under compressive residual stress based on their thermoelectric power contrast with respect to the surrounding intact material. However, further research is needed to better separate residual stress effects from secondary material effects, especially in the case of low-conductivity engineering materials like titanium alloys.