Effects Of Argon Laser Irradiation Research Articles

Study The effect of Annealing and Argon Laser Irradiation on the optical properties of SnO2 Thin film

In this research we study the effect of Argon Laser Irradiation and annealing on the some optical properties of SnO2 Thin film . These films were prepared by chemical spray pyrolysis method. The film thickness was 1500 A°. optical properties such as (Reflection, Energy band gab, Absorption coefficient, Refractive index, and extinction coefficient) as a function of photon energy have been studied within the wavelength range (300-900) nm, using (u v-visible) Spectrophotometer, before and after irradiation and annealing. it is found that the optical properties were change .

Effects of Argon laser irradiation on polar excitations in frog sciatic nerve

Since the mechanisms underlying the effects of low-power laser irradiation on the nervous system remain unclear, we examined whether such irradiation can influence ionic channels of the nerve membrane using the law of polar excitation in isolated frog sciatic nerve. Using 43 frogs (Xenopus laevis), nerve preparations were stimulated at 0.5/second using a 10-millisecond pulse at supramaximal intensity. Ar+ laser irradiation (457, 488, 514 nm; 50, 75, 100 mW) was applied for 30 minutes to the portion between the anode and cathode stimulating electrodes. Ar+ laser irradiations (457, 488 nm; 50 mW) blocked the generation of anode-break-excitation, rather than cathode-make-excitation. Such a selective effect occurred when applying a blocker of hyperpolarization-activated cation current (Ih) channel, ZD7288. Ar+ laser irradiation may influence Na+ channels in addition to Ih channels.

The effects of argon laser irradiation on enamel decalcification: An in vivo study

Enamel decalcification is a significant problem in orthodontic patients. The argon laser has been shown to reduce decalcification during an acidic challenge in vitro. The purpose of this study was to investigate the in vivo effects of argon laser irradiation on enamel decalcification during orthodontic treatment. Nine volunteers whose treatment plans included 4 first premolar extractions were enrolled in the study. The 36 extracted premolars were assigned to 1 of the following 4 groups: group 1, control group with no treatment; group 2 (pumice-laser), teeth were pumiced for 3 seconds and treated with a 325 mW, 5-mm diameter laser beam for 60 seconds; group 3 (pumice-etch-laser), teeth were pumiced for 3 seconds, acid-etched with 30% phosphoric acid for 30 seconds, and treated for 60 seconds with laser; and group 4 (laser only), teeth were treated for 60 seconds with laser. A specially designed (oversized) orthodontic band was fitted on each of the premolars to create a pocket for decalcification. The bands were cemented in place for 5 weeks. After extraction, the teeth were sectioned and examined under polarized light microscopy. Images of lesions were digitally analyzed and measured. Average lesion depths were calculated from 3 depth measurements recorded 10 μm apart. Average lesion area was calculated with the aid of imaging analysis software. Data were analyzed with analysis of variance (P <.05) and Student t tests. Significant differences were found in lesion depth (P <.001) and lesion area (P <.01) among the 4 test groups. The average lesion depths were 15.93 ± 9.31 μm (control), 6.45 ± 8.70 μm (pumice-laser), 1.71 ± 4.82 μm (pumice-etch-laser), and 1.34 ± 3.80 μm (laser only). The average lesion areas were 1028.67 ± 725.68 μm2 (control), 555.49 ± 948.20 μm2 (pumice-laser), 79.91 ± 226.03 μm2 (pumice-etch-laser), and 55.71 ± 157.59 μm2 (laser only). The average lesion depth in the laser-only group was reduced by 94.1% and the average lesion area was reduced by 94.4% when compared with the control group. In the pumice-etch-laser group, the average lesion depth was reduced by 89.1% and the average lesion area was reduced by 92.2% when compared with the control group. There were no significant differences in lesion depth and lesion area between maxillary and mandibular teeth (P <.06 and P <.08, respectively) and between the teeth on the right and left sides (P <.68 and P <.55, respectively). These results show that argon laser irradiation is effective in reducing enamel decalcification during orthodontic treatment. Pumicing and etching do not appear to reduce the effect of laser on enamel solubility. (Am J Orthod Dentofacial Orthop 2002;122:251-9)

Effect of argon laser irradiation on shear bond strength of orthodontic brackets: An in vitro study

Argon lasers, due to their significant time savings over conventional curing lights, are being investigated for use in bonding orthodontic brackets. They are also being investigated for their ability to confer demineralization resistance on enamel. The purpose of this study was to evaluate the effects of argon laser irradiation on bond strength at 3 different laser energies (200, 230, and 300 mW) and at 3 unique time points of laser application (before, during, or after bracket placement). One hundred-fifty human posterior teeth were divided into 9 study groups and 1 control group. After debonding, the adhesive remnant index was scored for each tooth. There was no evidence of an effect of energy level on bond strength, P =.903, or of an interaction between timing of bracket placement and energy level, P =.858. When combining data across energy levels, the mean bond strength was significantly different between all 3 bracket placement groups, P <.001. In addition, the mean bond strength of teeth lased after bonding was significantly higher than the control group, P <.05. There were no statistically significant differences between adhesive remnant index scores among the 10 groups. Lasing the enamel before or after bonding does not adversely affect bond strength. Use of the argon laser to bond orthodontic brackets can yield excellent bond strengths in significantly less time than conventional curing lights, while possibly making the enamel more resistant to demineralization. (Am J Orthod Dentofacial Orthop 2000;118:274–9)

Effect of argon laser irradiation on instrumented root canal walls.

The objective of the study was to examine whether argon laser has a property to remove debris and smear layer from root canal walls. Twelve endodontically treated human maxillary molar teeth with three root canals were divided into two groups of six teeth. The first group was left unlased as a control; in the second group the root canals were irradiated by argon laser (laser parameters were set at 1 W and pulse duration and pulse frequency fixed at 0.05 s and 5 Hz). After the usual root canal preparation and lasing had been carried out, the teeth were decoronated, bisected longitudinally, observed with a scanning electron microscope and evaluated as to how clean the surfaces of root canal walls were. In most cases control teeth presented surfaces with debris covering the root canals, obscuring the dentinal tubules. Only 1 of 18 specimens was free of debris. In the lased group, root canal surfaces free of debris and vaporized pulpal tissue remnants were observed in 13 of 18 specimens. The results showed significant statistical differences between the control group and the lased groups (P < 0.001). These results suggested that argon laser irradiation has an efficient cleaning effect on instrumented root canal surfaces.

Argon laser irradiation to the semicircular canal.

In order to elucidate the effects of argon laser irradiation on the lateral semicircular canal of the guinea pig, the vestibular labyrinth was histologically studied after irradiation, using the conventional celloidin method. Irrigation of the external meatus with ice water was used to evaluate the function of the semicircular canal by recording caloric nystagmus. When irradiation was performed, a laser probe was approximated to the lateral canal, 0.5 to 1 mm away from the surface of the canal. Each time, power applied was 1.0 W on the dial of the laser machine. The duration of irradiation was 0.5 s. The lateral canal was irradiated one to 15 times. Twenty-five to 87 days after irradiation, the temporal bones were fixed in Heidenhein-Susa solution, removed, and subjected to celloidin processing. The irradiated bony wall of the lateral canal demonstrated charring. Lucent areas were observed around and under the charred area. The semicircular duct showed shrinkage with disappearance of the trabecular mesh. New bone formation was observed along the endosteum of the irradiated area. The lateral canal was completely occluded by ossification with or without fibrosis when sufficient energy was applied. The anterior and posterior canals were normal. Caloric tests using 5 mL of ice water for 5 s failed to elicit nystagmus on the irradiated side.

Phototoxicity of argon laser irradiation on biofilms of Porphyromonas and Prevotella species

Species of Prevotella (Pr.) and Porphyromonas (Po.) and other microorganisms were cultivated as biofilms on agar medium and examined for their susceptibility to argon laser irradiation (continuous mode; wavelengths, 488–514 nm; fluences, 20–200 J cm −2). Fluences of 35 to 80 J cm −2 inhibited biofilm growth in Po. endodontalis, Po. gingivalis, Pr. denticola, Pr. intermedia, Pr. melaninogenica and Pr. nigrescens. A fluence of 70 J cm −2 did not affect biofilm growth in species of Bacillus, Candida, Enterobacter, Proteus, Pseudomonas, Staphylococcus and Streptococcus. The phototoxic effects of argon laser irradiation against Prevotella and Porphyromonas species were: (1) caused by the radiation alone; (2) modified by biofilm age; (3) dependent on the presence of atmospheric oxygen; (4) influenced by medium supplements of hemin, hemoglobin and blood; (5) greater when compared with other microbial species; (6) demonstrated without augmentation with an exogenous photosensitizer; and (7) apparently unrelated to the protoporphyrin content of the cells. Overall, these in vitro findings suggest that low doses of argon laser radiation may be effective in the treatment and/or prevention of clinical infections caused by biofilm-associated species of Prevotella or Porphyromonas.

Effects of argon laser irradiation with 38% Ag(NH3)2 F on the permeability of root canal wall dentin

Effects of argon laser irradiation with 38% Ag(NH₃)₂ F on the permeability of root canal wall dentin

Argon Laser Irradiation in Root Surface Caries: in Vitro Study Examines Laser’S Effects

Recent research shows that laser irradiation can improve enamel's resistance to caries. This in vitro study examines the effects of argon laser irradiation on root surface caries. Treated surfaces seemed more resistant to an artificial caries medium than control surfaces.

Effects of Argon Laser Irradiation on the Utricular Macula

Effects of Argon Laser Irradiation on the Utricular Macula

Effect of argon laser irradiation on rabbit aortic smooth muscle: evidence for endothelium independent contraction and relaxation.

To study the effect of argon laser irradiation on vascular smooth muscle reactivity, ring segments of rabbit thoracic aorta were mounted isometrically in Krebs bicarbonate buffer. Laser irradiation was performed via a 200-micron core optical fibre interfaced with an argon ion gas laser. Laser irradiation at powers greater than 1.0 watt (W) (n = 34) produced contraction in each case, regardless of the duration of exposure. Conversely, irradiation at powers less than 0.1 W (n = 41) consistently produced relaxation. When the power employed ranged from 0.1 to 1.0 W (n = 100), the typical response consisted of a combination of low amplitude contraction and relaxation. At each power level, the responses observed were independent of the presence or absence of intact endothelium, assessed functionally by the response to acetylcholine and anatomically by scanning electron microscopy. Recordings of tissue temperature profiles performed during continuous-wave laser irradiation suggest that the findings observed in this study may be explained by a combination of heat induced contraction and light induced relaxation. At powers greater than 1.0 W, heat generated by laser irradiation is predominant, causing contraction. At powers less than 0.1 W, light predominates over heat, causing relaxation. When the power range is intermediate between these values, the heterogeneous response recorded reflects the combination of light and heat. In all cases, contraction and relaxation are endothelium independent.

Application of argon laser to the inner ear.

The effects of argon laser irradiation on the inner ear were studied morphologically. The stria vascularis showed focal coagulation, vesicle formation, perforation and atrophy after irradiation through the otic capsule. These changes vary according to the power and duration of irradiation. Atrophy of the stria vascularis can be produced without injuring the organ of Corti, by suitable application of the laser beam. The round window membrane transmits the argon laser. Tissues in the hook region and a part of the lower basal turn demonstrated changes of varying degree. Loss of the nerve fibres was observed in the osseous spiral lamina, which was fractured and dislocated. Irradiation through the stapedectomized oval window destroyed the macula sacculi without rupturing the saccular wall.

アルゴンレーザーのヒトリンパ球に及ぼす影響

Cytogenetic effects of argon laser irradiation were studied on human lymphocytes in terms of sister chromatid exchange. Argon laser irradiation of up to 300 Joule/cm2 caused increase in SCE. The increment was more prominent when G1 lymphocytes were irradiated than GO cells. Slight suppression of the cell cycle progression was observed by laser irradiation. Although precise mechanism is still unclear, possible chromosomal damage relating to the cell division was suspected.

Cytogenetic Effects of Argon Laser Irradiation on Chinese Hamster Cells

The cytogenetic effects of argon laser light on V79 Chinese hamster cells were studied. Irradiation with a defocused continuous beam from an argon laser at doses of 100 to 400 J/cm2 had dose-related cytostatic and cytocidal effects. Cell cycle analysis by flow cytofluorometric measurement indicated that argon laser irradiation induced a temporary block at the G2 + M phase. The survival curve after laser irradiation was exponential without an initial shoulder and the D0 value (34% lethal dose) was calculated as 170 J/cm2. A significant increase in sister chromatid exchange was observed after laser irradiation. Laser irradiation also induced chromatid and chromosome aberrations, most of which were breaks and gaps. These chromosomal changes are probably not an artifact of the experimental procedures such as the use of phenol red and antibiotics or spontaneously emitted uv light. No mutation at the Na+/K+-dependent ATPase locus was induced by argon laser irradiation. Although the mechanism by which an argon laser beam induces cytogenetic damage remains to be investigated, the possible involvement of hyperthermia seemed to be excluded.

アルゴンレーザーの染色体に及ぼす影響

In order to study possible cytogenetic effects of argon laser irradiation, V79 Chinese hamster fibroblasts were irradiated with a defocused argon laser beam (100-400 J/cm2). Inhibition of cell growth was observed dose dependently. Flow-cytofluorometric analysis indicated the blockage of cell cycle progression at G2+M phase. Chromosomal effects were investigated by sister chromatid exchange and chromosomal aberration, both of which were elevated dose dependently. Mutation was not induced in ouabain locus. These cytological changes were not due to elevation of temperature during irradiation or experimental artifacts such as the possible phototoxic effects of Kanamycin or phenol red in the culture medium or spontaneous emission of UV light of the laser. These results indicate that the argon laser irradiation at high doses probably induces damage at the chromosomal level.

Argon Laser照射の培養細胞に与える影響 (1)

Effect of argon laser irradiation on cultured cell was investigated. From the point of morphological and growth curve examination, Argon laser irradiation alone did not make any significant change at energy density tested this time.(1.6-102.0 J/cm2 )Argon laser irradiation on Acridine Orange pretreated cells showed marked suppression of growth and cell death at the moderate concentrations of AO (1μg/ml).The mechanism of combined AO and Laser irradiation is unknown but nucleic acid and lysosomal level damage is suspected.