YAG Laser Irradiation Research Articles

Is the Fractional Laser Still Effective in Assisting Cutaneous Macromolecule Delivery in Barrier-Deficient Skin? Psoriasis and Atopic Dermatitis as the Disease Models.

Most of the investigations into laser-assisted skin permeation have used the intact skin as the permeation barrier. Whether the laser is effective in improving cutaneous delivery via barrier-defective skin is still unclear. In this study, ablative (Er:YAG) and non-ablative (Er:glass) lasers were examined for the penetration of peptide and siRNA upon topical application on in vitro skin with a healthy or disrupted barrier. An enhanced peptide flux (6.9 fold) was detected after tape stripping of the pig stratum corneum (SC). A further increase of flux to 11.7 fold was obtained after Er:YAG laser irradiation of the SC-stripped skin. However, the application of Er:glass modality did not further raise the flux via the SC-stripped skin. A similar trend was observed in the case of psoriasiform skin. Conversely, the flux was enhanced 3.7 and 2.6 fold after treatment with the Er:YAG and the Er:glass laser on the atopic dermatitis (AD)-like skin. The 3-D skin structure captured by confocal microscopy proved the distribution of peptide and siRNA through the microchannels and into the surrounding tissue. The fractional laser was valid for ameliorating macromolecule permeation into barrier-disrupted skin although the enhancement level was lower than that of normal skin.

CLINICAL EXPERIENCE OF USING SUBMILISECOND Nd:YAG-LASER RADIATION 1064 NM AND CREAM WITH 1% OF IVERMEKTIN FOR TREATMENT OF PAPULOPUSTULAR FORM OF ROSACEA

Rosacea is a polyethiological disease at the base of it progress is pathologically changed innervation of vessels of the skin of face - angioneurosis and it undergoes several stages of development. Initially, against the background of permanent extension, the vascular wall loses elasticity and the blood plasma penetrates it. Microcirculation disorders lead to hypostasis of tissues. This process leads to change of a biota of the face skin - to the uncontrollable growth of number of a Demodex tick, which is one of the ethyopathogenetics factor of promotion from erythemoteleangiectatic form to papulopustular. Etiological reasonable approach for therapy of papulopustular rosacea is a combination of external and physiotherapeutic methods of therapy. As medicamentous therapy for suppression of excess activity of a Demodex tick and its uncontrollable growth in our research we have taken the cream with 1% of Ivermektin. As a physiotherapeutic influence - the submilisecond Nd:YAG-laser radiation (1064 nm). This radiation influences at expanded vessels, sanifies pustules, moderate temperature increase in a derma to 41-42оС, leads to elimination of puffiness and stage-by-stage restructuring of collagen fibers.

Chemical Changes of Enamel Produced by Sodium Fluoride, Hydroxyapatite, Er:YAG Laser, and Combined Treatments

Occlusal pits and fissures of permanent molars are considered to have higher risk of developing caries. Enamel demineralization can be prevented by applying remineralizing agents, and their absorption increases with prior irradiation. This work evaluates the chemical changes produced by treating occlusal surfaces with sodium fluoride (NaF), hydroxyapatite-NaF-xylitol (HA-NaF-X), Er:YAG laser irradiation (L), and combinations thereof. Fifty enamel samples were randomly assigned to five groups (n=10): NaF, HA-NaF-X, L, L + NaF, and L + HA-NaF-X. The chemical composition of human enamel was evaluated before (BT) and after (AT) treatment using energy-dispersive X-ray spectroscopy (EDS) and expressed in atomic percentages (at%). For combined treatment groups, the products were applied after laser irradiation. The statistical analyses included a pairedt-test and ANOVA (p≤0.05). After treatment, a significant increase in F at% was observed in the NaF group (2.71 ± 1.41). The irradiated groups showed significant increases in Ca and P at% and the Ca/P ratio. The highest values occurred for L + NaF (30.44 ± 4.28 Ca at%, 11.97 ± 1.45 P at%, and 2.55 ± 0.22 Ca/P ratio). Er:YAG laser irradiation alone or in combined protocols increased the Ca and P content of dental enamel, in vitro.

The Rate of Demineralization in the Teeth Prepared by Bur and Er:YAG Laser.

Introduction: The present in vitro study evaluated the recurrence rate of caries following cavity preparations with bur (conventional technique) and irradiation by Erbium:Yttrium- Aluminum-Garnet (Er:YAG) laser through micro hardness test. Methods: A total of 72 human extracted molars were randomly divided into 3 groups and class 5 cavities were prepared on them with 3 different methods: G1) conventional bur, G2) Er:YAG laser irradiation alone and G3) laser irradiation + laser treatment. The specimens were immersed in the artificial caries solution with pH of 2.0 and 5.0 (12 days) and then immersed in re-mineralizing solution with pH of 7.0 (25 days). The specimens were longitudinally sectioned and their Vickers micro hardness was determined. Data were statistically analyzed by means of three-way analysis of variance (ANOVA) and Tukey multiple comparisons tests. Results: The micro hardness of the samples was affected by substrate type (enamel and dentin) and low values were achieved in dentin (P<0.001). Moreover, no significant difference was observed between preparation methods by bar and laser irradiation alone (P ≤0.499). Although laser irradiation + laser treatment decreased micro hardness of enamel compared to other methods. In dentin samples, different methods of preparation showed no significant effect on micro hardness (P ≤0.874). Conclusion: Due to the similar values of micro hardness following G1 and G2, it seems that Er:YAG laser alone is as much effective as the conventional bur to prevent recurrence caries. However, because of the high prices of laser instruments, bur preparations can be done commonly.

Properties of Al- and Ga-doped thin zinc oxide films treated with UV laser radiation

This paper reports the Nd:YAG laser irradiation treated modified properties of aluminum (Al) and gallium (Ga) co-doped zinc oxide (ZnO) (AGZO) films prepared on Si-substrate via combined sol–gel and spin-coating method. The impact of varying laser energy (150–200 mJ) on the structure, morphology, electrical and optical properties of such AGZO films were determined. Laser-treated samples were characterized using various analytical tools. Present techniques could achieve a high-quality polycrystalline films compared with those produced via conventional high temperature processing. AGZO films irradiated with third harmonics UV radiation (355 nm) from Nd:YAG laser source revealed very low resistivity of 4.02 × 10− 3 Ω cm. The structural properties grain size was calculated firm the X-ray diffraction spectra using the Scherrer equation that increased from 12.7 to 22.5 nm as the annealing laser energy increased from (150–200) mJ. The differences in crystallinity and orientation are explained in terms of the thermal effect caused by laser irradiation. (FESEM) images have been demonstrated that Nd:YAG laser annealing can significantly improve the crystallinity level, densification, and surface flatness of sol–gel derived AGZO thin films that occurred as a result of laser processing. Synthesized AGZO films displayed favorable growth orientation along (101) lattice direction. AGZO films with energy band gap of 3.37–3.41 eV were obtained. Results on the crystallinity, surface morphology, roughness, bonding vibration, absorption, photoluminescence, and resistivity of the laser-irradiated films were analyzed and discussed.

Morphological and chemical changes in human deciduous dentin after phosphoric acid, self-etching adhesive and Er: YAG laser conditioning.

The morphological and chemical changes in deciduous dentin produced by different conditioning protocols were evaluated in this in vitro study. Eighty primary dentin samples were divided into eight groups (n = 10): G1, acid etching; G2, self-etching adhesive; G3, G4, Er: YAG laser irradiation at 25.5 and 38.2 Jcm-2 , respectively; 10 Hz and spray irrigation. Groups 5, 6, 7, and 8 were irradiated at previous densities, and then phosphoric acid or self-etching adhesive conditioning was applied. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to evaluate chemical and morphological changes. Paired t-test and One-way ANOVA were used for statistical analysis (p ≤ 0.05). All samples showed different morphology with specific characteristics according to the conditioning protocol. Changing element concentration values are expressed in atomic percent (at %). After conditioning, there were statistically significant differences (p ≤ 0.05) for p at% and Ca/P in all groups; highlighting the following additional findings by group: G1, G7, and G8 showed changes in all elements studied, G2 presented a decrease in C at% and increased Ca at%, G3 and G4 exhibited at% changes in C, trace elements and Ca. Furthermore, G5 showed at% changes in O and trace elements; while G6 changes were observed on C at%, O at% and trace elements at%. Dentin morphology and chemical composition varied in accordance with the conditioning protocol, with characteristics specific for each one that could have clinical implications for the retention and bond strength performance of adhesive materials.

Antibacterial Effect of Surface Pretreatment Techniques against Streptococcus Mutans.

The aim of this study was to evaluate the antibacterial surface pretreatment methods against Streptococcus mutans within the infected dentin surface using a tooth cavity model. Seventy-two cavities were prepared on caries-free third molars (n = 8). After sterilization, teeth were inoculated with S. mutans for 48 h. One cavity of each tooth was used to evaluate the infection. Following inoculation, infected cavity surfaces were treated either with (1) Er:YAG Laser (1W; 5x5s, Smart 2940D Plus, Deka Laser), (2) Ozone (80s; HealOzone, Kavo), (3) ErYAG-Ozone combination, (4) Er:YAG-Ozone-CHX combination, (5) Chlorhexidine (CHX), (6) Clearfil Protect Bond (PB), (7) potassium-titanyl-phosphate (KTP) Laser (1W; 60 s, SMARTLITE D, Deka Laser), (8) KTP-Ozone combination, and (9) KTP-Ozone-CHX. Standardized amounts of dentin chips were obtained from the cavity walls, and the number of bacteria recovered was counted. Kruskal-Wallis test was used for statistical analyzes. Both sole antibacterial materials, CHX or Protect Bond application, exhibited the most effective antibacterial activity with 125 and 156 CFU is an acronym of "colony forming unit" usullay mentioned by acronym. (CFU/ml), respectively, among the groups evaluated (P < 0.05). Er:YAG laser irradiation and its combinations with other antibacterial surface pretreatment applications also inhibited the bacterial growth with, respectively, 1444, 406, and 294 CFU/ml bacterial recovery being more efficient than KTP laser irradiation and ozone combinations. As an alternative device with photodynamic effects, Er:YAG and KTP laser irradiations and their further combinations during the cavity pretreatment procedure with chlorhexidine and ozone treatments exerted antibacterial effect against S. mutans, whereas chlorhexidine and antibacterial dentin bonding application solely have the highest antibacterial effects.

Variation on Molecular Structure, Crystallinity, and Optical Properties of Dentin Due to Nd:YAG Laser and Fluoride Aimed at Tooth Erosion Prevention.

This in vitro study evaluated the compositional, crystalline, and morphological effects promoted by Nd:YAG laser on root dentin, and verified the effects of laser and topical acidulated phosphate fluoride application (APF-gel) on dentin erosion. 180 bovine dentin slabs were randomized into 4 groups (n = 45): G1–untreated, G2–APF-gel (1.23% F−, 4 min), G3–Nd:YAG (1064 nm, 84.9 J/cm2, 10 Hz), and G4–APF-gel application followed by Nd:YAG laser irradiation. The compositional, crystalline, and morphological effects promoted by treatments were investigated on five samples of each experimental group. The other samples were submitted to a 5-day, 10-day, or 15-day erosive and abrasive demineralization and remineralization cycling in order to create erosion lesions. The area and depth of lesions, as well as the optical attenuation coefficient, were assessed, and all data were statistically analysed (p < 0.05). Nd:YAG laser promoted the reduction of carbonate, the formation of tetracalcium phosphate, as well as the melting and recrystallization of the dentin surface. Laser significantly decreased the area and depth of erosion lesions and altered the optical attenuation coefficient when compared to untreated and APF-gel groups, but the association of APF-gel and laser did not promote an additional effect. Nd:YAG laser irradiation can be a promissory treatment to prevent dentin erosion and the abrasion process.

Study of Stark broadening of Li i 460 and 497 nm spectral lines with independent plasma diagnostics by Thomson scattering

We present results of experimental and theoretical studies of the Stark broadening of the Li i 460 nm spectral line with forbidden components and of the isolated 497 nm line. Plasma was induced by Nd:YAG laser radiation at 1064 nm with pulse duration ∼4.5 ns. Laser-induced plasma was generated in front of the alumina pellet, with some content of Li2CO3, placed in a vacuum chamber filled with argon under reduced pressure. Plasma diagnostics was performed using the laser Thomson scattering technique, free from assumptions about the plasma equilibrium state and its composition and so independently of plasma emission spectra. Spatially resolved spectra with Li lines were obtained from the measured, laterally integrated ones applying the inverse Abel transform. The Stark profiles were calculated by computer simulation method assuming a plasma in the local thermodynamic equilibrium. Calculations were performed for experimentally-inferred electron densities and temperatures, from 1.422 × 1023 to 3.55 × 1022 m−3 and from 1.96 eV to 1.04 eV, respectively. Our studies show very good agreement between experimental Stark profiles and those computer simulated.

EFFECT OF SUBSTRATE TEMPERATURE ON THE GROWTH OF COPPER OXIDE THIN FILMS DEPOSITED BY PULSED LASER DEPOSITION TECHNIQUE

The effect of substrate temperature on growth of pulsed laser deposited copper oxide thin films has been investigated by employing Nd: YAG laser (532[Formula: see text]nm, 6[Formula: see text]ns, 10[Formula: see text]Hz) irradiation at a fluence of 8.2[Formula: see text]J/cm2. XRD analysis reveals that copper oxide films deposited at room temperature are amorphous in nature, whereas films deposited at higher substrate temperatures are polycrystalline in nature. SEM and AFM analyses revealed that films deposited at substrate temperatures, ranging from room temperature to 300[Formula: see text]C are comprised of large sized clusters, islands and particulates, whereas uniform films with an appearance of granular morphology and distinct bump formation are grown at higher substrate temperatures of 400[Formula: see text]C and 500[Formula: see text]C. The optical bandgap of deposited films is evaluated by UV-VIS spectroscopy and shows a decreasing trend with increasing substrate temperature. Four point probe analysis reveals that electrical conductivity of the deposited films increases with increase in the substrate temperature, and is maximum for highest growth temperature of 500[Formula: see text]C. It is revealed that growth temperature plays a significant role for structure, texture, optical and electrical behavior of copper oxide thin films. The surface and structural properties of the deposited films are well correlated with their electrical and optical response.

Long-term effect of Er:YAG laser on adhesion to caries-affected dentin

This study investigated the long-term effect of Er:YAG laser pretreatment on the adhesion of a self-etch adhesive system to caries-affected dentin (CAD). Ninety human dentin specimens were submitted to Streptococcus mutans biofilm cariogenic challenge (7 days) to obtain artificial CAD lesions (4 × 5 mm). Groups were defined by the surface pretreatment [no pretreatment; 80 mJ, 2 Hz, 50 μs, − 13.33 J/cm2; or 50 mJ, 10 Hz, 50 μs, − 8.33 J/cm2], substrate [sound (SD) or CAD], and storage [24 h or 1 year]. Different tests were performed: microshear bond strength (μSBS), adhesive (AL) and hybrid (HL) layer’s nanohardness test, and as well as a morphological analysis, by scanning electron microscopy (SEM) of the adhesive interface. Three-way ANOVA and Tukey’s multiple comparison tests (α = 0.05) showed that CAD had lower μSBS values than SD after 1 year despite surface pretreatments (p = 0.00). AL nanohardness test revealed that specimens’ hardness decreased after 1 year (p = 0.00). The HL produced had lower nanohardness in CAD than in SD, which decreased over time for all surface pretreatments (p = 0.00). SEM analysis revealed that all adhesive interfaces, especially in CAD, degraded after 1 year. Caries-affected dentin did not seem to be an adequate substrate for bonding. Er:YAG laser irradiation did not influence adhesion to CAD and SD.

Effect of Different Laser Treatments on the Bond Strength of Intracanal Fiber Posts Cemented with a Self‐Adhesive Resin Cement

To evaluate the influence of laser-activated irrigation by Er:YAG and Er:YSGG (LAI) protocols and Nd:YAG laser irradiation on the bond strength of self-adhesively cemented fiber posts to root canal dentine. The study sample consisted of 84 human single-rooted permanent teeth instrumented with ProTaper Next technique. After obturation, post space preparations were created for fiber-reinforced composite posts. The prepared specimens were divided according to the laser treatment of the post space preparations: group 1: LAI (Er:YAG) + saline solution (pulse energy: 20 mJ, repetition rate: 15 Hz); group 2: LAI (Er:YAG) + QMiX solution (pulse energy: 20 mJ, repetition rate: 15 Hz); group 3: LAI (Er,Cr:YSGG) + saline solution (pulse energy: 62.5 mJ, 20 Hz); group 4: LAI (Er,Cr:YSGG) + QMiX (pulse energy: 62.5 mJ, 20 Hz); Nd:YAG laser (pulse energy: 100 mJ, 10 Hz). Fiber-reinforced posts were cemented with a self-adhesive cement. The bond strength was evaluated by the push-out bond strength test, and the mode of failure was determined under a stereomicroscope. Kruskal-Wallis test was used for the intergroup comparative analysis with 5% level of significance. The highest bond strength was recorded in the Er:YAG + QMiX group (mean 3.401 MPa) (p < 0.05), followed by the Er,Cr:YSGG and the Er:YAG + saline solution (mean 1.111 MPa and 1.094 MPa, respectively), which did not differ significantly (p = 0.232). The irradiation with the Nd:YAG laser caused similar bond strength as the Er,Cr:YSGG + QMiX (p = 0.942). All laser protocols enhanced the bond strength of the self-adhesive cement in root canals compared to only saline irrigation. The bond strength of the self-adhesive cement depended on the laser parameters and irrigant used for the LAI.

Investigation of field emission properties of laser irradiated tungsten

Nd:YAG laser irradiation of Tungsten (W) has been performed in air at atmospheric pressure for four laser fluences ranging from 130 to 500 J/cm2. Scanning electron microscope analysis revealed the formation of micro and nanoscale surface features including cones, grains, mounds and pores. Field emission (FE) studies have been performed in a planar diode configuration under ultra-high vacuum conditions by recording I–V characteristics and plotting corresponding electric field (E) versus emission current density (J). The Fowler–Nordheim (FN) plots are found to be linear confirming the quantum mechanical tunneling phenomena for the structured targets. The irradiated samples at different fluences exhibit a turn-on field, field enhancement factor β and a maximum current density ranging from 5 to 8.5 V/µm, 1300 to 3490 and 107 to 350 µA/cm2, respectively. The difference in the FE properties is attributed to the variation in the nature and density of the grown structures at different fluences.

Habitual growth and its influence on the properties of anilinium perchlorate (AP) single crystal for nonlinear optical device applications

The habit of the semi organic nonlinear optical material anilinium perchlorate (AP) crystallized from different solvents, such as n-hexane, acetonitrile, toluene, acetone, ethanol, methanol and water were studied. Solubility of AP in above mentioned solvents at different temperatures was determined by gravimetric method. Crystals were grown by controlled solvent evaporation method. Solution with different solvents having different chemical nature and polarity yielded crystals with different habits, such as needle, platelet, bar, pyramidal cuboid, pyramidal cubic square and cuboid. The AP crystal shows predominant growth behaviour along its (2 0 \(\bar{1}\)) direction irrespective of the solvent used. The AP crystal grown from different solvents were found to crystallize in orthorhombic system with space group P212121. Optical transmittance of the grown crystals was studied using UV–Vis–NIR spectrophotometer. The FWHM of the AP crystal was found to be 65.7 arc s by high resolution X-ray diffraction study. The effective nonlinearity of the AP crystal grown is 2.8 times greater compared to that of the standard KH2PO4 crystal. The laser damage threshold of the crystals grown from various solvents were assessed using 1064 nm ND:YAG laser radiation. The relative SHG efficiency of AP is found to increase with the quality of the crystal.

Nd: YAG laser irradiation effects on structural and magnetic properties of Ni1+xZrxFe2–2xO4 nanoparticles

The effect of 112mJ Nd: YAG laser irradiation on structural, morphological, infrared and magnetic properties of Ni1+xZrxFe2–2xO4 spinel ferrite nanoparticles has been systematically investigated in the present work. The sol-gel auto combustion synthesis method was successfully executed for the synthesis of the present system. All the samples were characterized by X-ray diffraction technique (XRD), scanning electron microscopy (SEM) and infrared spectroscopy (IR) technique. The magnetic properties of the present samples were measured by pulse field hysteresis loop technique. All the properties were measured for laser irradiated samples as well, to understand the effect of irradiation on the properties. The single-phase cubic spinel structure was confirmed by X-ray diffraction patterns of all samples and the disordered structure was observed for irradiated samples. The two principle absorption bands in IR spectra also confirm the formation of the spinel structure. Spherical and agglomerated morphology was observed for Zr4+ substituted nickel ferrite, whereas scratched morphology was observed for the irradiated samples. The grain size confirms the nanocrystalline nature, the crystallite size also evident the same. The magnetic parameters decreased after Zr4+ ion doping and strongly influenced by the irradiation.

Comparative evaluation of antibacterial effect of nanoparticles and lasers against Endodontic Microbiota: An in vitro study.

BackgroundPresent study was conducted with the aim of evaluating antimicrobial efficacy of silver (AgNP) and gold nanoparticles (AuNP) with and without Nd: YAG laser (L) irradiation against experimentally inoculated Enterococcus faecalis in infected human root dentin.Material and Methods120 extracted single rooted human teeth were prepared and inoculated with E. faecalis for 24 hrs. The teeth were then randomly divided into 4 experimental group: AgNPs group: irrigation for 3minutes with 50 μl of 100 ppm, the AuNPs group: irrigation with 50 μl of 100 ppm, the AgNPs & Nd: YAG lasers group: irrigation with 50 μl of 100 ppm + irradiation with 1.5W laser for 60 seconds, the AuNPs & Nd: YAG lasers group: irrigation with 50 μl of 100 ppm + irradiation with 1.5W laser for 60 seconds. One control group consisting of 2% CHX irrigation for 3 minutes was also there (n = 20). The specimens were collected from the canal before and after irrigation, and colony forming units were observed.ResultsSignificant difference was found among all the groups in comparison to the control group (p<0.05). The greatest reduction in CFU’s was observed with combination of AgNPs & Nd: YAG lasers group.Conclusions AgNPs in combination with Nd: YAG laser irradiation has the potential to be used as root canal disinfectant. Key words:Antibacterial efficacy, gold, silver, nanoparticles, lasers, solid-state.

Effect of sandblasting, silica coating, and erbium: Yttrium-Aluminum-Garnet laser treatment on the shear bond strength of self-adhesive resin cement to alumina ceramics.

The aim of this study was to investigate the different surface treatments on the bond strength of self-adhesive resin cement to high-strength ceramic. Ninety aluminum oxide ceramic (Turkom-Ceramic Sdn. Bhd., Kuala Lumpur, Malaysia) specimens were produced and divided into nine groups to receive the following surface treatments: control group, no treatment (Group C), sandblasting (Group B), silica coating (Group S), erbium: yttrium-aluminum-garnet (Er:YAG) laser irradiation at 150 mJ 10 Hz (Group L1), Er:YAG laser irradiation at 300 mJ 10 Hz (Group L2), sandblasting + L1 (Group BL1), sandblasting + L2 (Group BL2), silica coating + L1 (Group SL1), and silica coating + L2 (Group SL2). After surface treatments, surface roughness (SR) values were measured and surface topography was evaluated. Resin cement was applied on the specimen surface, and shear bond strength (SBS) tests were performed. Data were statistically analyzed using one-way ANOVA and Tukey's multiple comparisons at a significance level of P < 0.05. Group S, SL1, and SL2 showed significantly increased SR values compared to the control group (P < 0.05); therefore, no significant differences were found among the SR values of Groups B, BL1, BL2, L1, and L2 and the control group (P > 0.05). Group S showed the highest SBS values, whereas the control group showed the lowest SBS values. Silica coating is the most effective method for resin bonding of high strength ceramic, but Er:YAG laser application decreased the effectiveness.

Effect of Er:YAG laser energy densities on thermally affected dentin layer: Morphological study.

Physical and chemical composition of dentin is subject to modification when irradiated with Er:YAG laser. Temperature rise causes water evaporation and micro-mechanical ablation of dentin. The misuse of laser parameters could affect negatively dentin collagen fibers leading to failure in bonded composite restorations. The aim of this in vitro study was to evaluate the effect of Er:YAG laser radiation at different levels of energy on the morphology of thermally affected dentin layer. Forty-eight freshly extracted human third molars were randomly divided into six groups (n = 8). In all groups, except for the control groups, dentin was subject to irradiation with H02 handpiece Er:YAG laser in non-contact mode (SSP mode = 50 µs; 10 Hz; speed of 1 mm/second; air 6 mL/min; and water 4 mL/min) with the following levels of energy (40, 60, 80, 100, and 120 mJ) respectively. Teeth were sliced longitudinally. Photo-ablated cavities were observed. The cavity depth and dentin fiber collagen deterioration were measured. Laser irradiation increased the depth of dentinal crater from 46.57 µm to 178.2 µm, when energy level increased from 40 mJ to 120 mJ. A superficial black layer, representing dentinal affected collagen fibers, was present in all groups except for control group. When comparing the thickness of the black layer, there was no significant difference between groups. It increased at 40 mJ to 28.17 µm then decreased to 15.19 µm at 60 mJ and then increased again for 80 mJ to 19.93 µm, 100 mJ to 22.87 µm and 120 mJ to 28.53 µm. Only one group (60 mJ) showed low values and significant difference as compared to the other irradiated groups, when multiple comparisons tests (ANOVA) were made using Newman-Keuls test. Dentin organic matrix presented the minimum alteration when Er:YAG laser is used specifically at an appropriate level of energy (60 mJ).

Synthesis, growth, structural modeling and physio-chemical properties of a charge transfer molecule: Guanidinium tosylate

An organic nonlinear optical material, guanidinium tosylate was synthesized adopting slow evaporation method and the crystals were harvested from aqueous methanolic medium with dimensions 13 × 9 × 3 mm3. Constitution of crystalline material was confirmed by single crystal X-ray diffraction study. The title compound crystallizes in the monoclinic crystal system with space group P21/c. The UV–vis–NIR spectral study of the grown crystal exhibits high transparency of 80% in the entire visible region with lower cut-off wavelength at 282 nm. Optimized molecular geometry of the grown crystal was obtained using density functional theory (DFT) and the frontier energy gaps calculated from the DFT aids to understand the charge transfer taking place in the molecule. The dielectric properties were studied as a function of temperature and frequency to find the charge distribution within the crystal. The titular compound is thermally stable up to 230 °C assessed by thermogravimetric and differential thermal analysis. Anisotropy in the mechanical behavior was observed while measuring for individual planes. The laser induced surface damage threshold of the grown crystal was measured to be 0.344 GW/cm2 for 1064 nm Nd:YAG laser radiation. Z-scan technique confirms the third-order nonlinear optical property with the ascertained nonlinear refractive index (n2), nonlinear absorption coefficient (β) and third order nonlinear susceptibility (χ(3)). Optical limiting study divulges that the transmitted output power step-up linearly with the increase of the input power at lower power realms and saturates from the threshold 24.95 mW/cm2 and amplitude 0.23 mW/cm2.

Biological effects of Er:YAG laser irradiation on the proliferation of primary human gingival fibroblasts.

We investigated the biological effects of Er:YAG laser (2940-nm; DELight, HOYA ConBio, Fremont, California) irradiation at fluences of 3.6, 4.2, 4.9, 6.3, 8.1 or 9.7 J cm-2 at 20 or 30 Hz for 20 or 30 seconds on primary human gingival fibroblasts (HGFs). Irradiation at 6.3 J cm-2 promoted maximal cell proliferation, determined by WST-8 assay and crystal violet staining, but was accompanied by lactate dehydrogenase release, on day 3 post-irradiation. Elevation of ATP level, Ki67 staining, and cyclin-A2 mRNA expression confirmed that Er:YAG affected the cell cycle and increased the number of proliferating cells. Transmission electron microscopy showed alterations of mitochondria and ribosomal endoplasmic reticulum (ER) at 3 hours post-irradiation at 6.3 J cm-2 , and the changes subsided after 24 hours, suggesting transient cellular injury. Microarray analysis revealed up-regulation of 21 genes involved in heat-related biological responses and ER-associated degradation. The mRNA expression of heat shock protein 70 family was increased, as validated by Real-time PCR. Surface temperature measurement confirmed that 6.3 J cm-2 generated heat (40.9°C post-irradiation). Treatment with 40°C-warmed medium increased proliferation. Laser-induced proliferation was suppressed by inhibition of thermosensory transient receptor potential channels. Thus, despite causing transient cellular damage, Er:YAG laser irradiation at 6.3 J cm-2 strongly potentiated HGF proliferation via photo-thermal stress, suggesting potential wound-healing benefit.