Laser Irradiation Group Research Articles

Molecular biological and histological effects of Er:YAG laser irradiation on tooth movement.

The aim of this study was to evaluate the effects of a fiberotomy-like procedure using Er:YAG laser irradiation on the velocity of orthodontic tooth movement. To produce experimental tooth movement in rats, orthodontic force was applied to the upper first molars with a nickel-titanium closed coil. The right molars were irradiated with an Er:YAG laser while the non-irradiated left molars were used as controls. The rats were sacrificed at 4 weeks after the start of tooth movement and the distance between the mesial side of the second molar and the distal side of the upper first molar was measured on CT images. The amount of tooth movement was significantly greater in the irradiation group than in the control group. The TRAP-positive nuclei count at the pressure site was higher in the laser-irradiation group than in the control group. Expression of RANKL and ALP was higher at the mesial-coronal pressure site in the laser-irradiation group than in the control group. In addition, expression of OPG was higher at the pressure site in the control group than in the laser-irradiation group. These results suggest that a fiberotomy-like procedure using an Er:YAG laser stimulates osteoclasts and osteoblasts and may promote bone metabolism in the context of experimental tooth movement.

Antimicrobial photodynamic of blue LED for activation of curcumin extract (curcuma longa) on staphylococcus aureus bacteria, an in vitro study

Staphylococcus aureus (S.aureus) is a normal skin flora. In abnormal conditions, these bacteria can cause mild skin infections such as acne vulgaris and cellulitis folliculitis that attack the respiratory system causing severe infections such as pneumonia and empyema occur. Systemic treatment with antibiotics for a long time can cause resistance. Antimicrobial photodynamic therapy (aPDT) is a therapy that uses light sources, photosensitizer (PS) agents and oxygen. This study aims to determine the effectiveness of blue LED (400-450) nm to activate exogenous PS of curcumin extract in S.aureus in vitro. To determine the antibacterial effect of curcumin extract (Curcuma longa) on S.aureus bacteria with LED radiation, the distribution of samples was divided into four treatment groups, Group (S − K −) control group without any treatment, group (S− K +) control group with curcumin extract, group (S + K−) group with LED irradiation without curcumin extract, group (S + K +) laser irradiation group with curcumin extract. Bacterial growth is measured using Elisa Reader and Total Plate Count Method. The results showed that the LED energy density 16.19 J/cm2 was able to increase the percentage of bacterial mortality by (91.49 ± 0.01) % with curcumin extract and (44.88 ± 0.18) % without curcumin extract. So LED irradiation is able to activate curcumin extract to increase the percentage of S.aureus bacterial death.

Targeted Photothermal Therapy of Melanoma in C57BL/6 Mice using Fe3O4@Au Core-shell Nanoparticles and Near-infrared Laser.

Background: Gold nanoshells can be tuned to absorb a particular wavelength of light. As a result, these tunable nanoparticles (NPs) can efficiently absorb light and convert it to heat. This phenomenon can be used for cancer treatment known as photothermal therapy. In this study, we synthesized Fe3O4@Au core-shell NPs, magnetically targeted them towards tumor, and used them for photothermal therapy of cancer.Objective: The main purpose of this research was to synthesize Fe3O4@Au core-shell NPs, magnetically target them towards tumor, and use them for photothermal therapy of cancer. Material and Methods: In this experimental study, twenty mice received 2 × 106 B16-F10 melanoma cells subcutaneously. After tumors volume reached 100 mm3, the mice were divided into five groups including a control group, NPs group, laser irradiation group, NPs + laser group and NPs + magnet + laser group. NPs were injected intravenously. After 6 hours, the tumor region was irradiated by laser (808 nm, 2.5 W/cm2, 6 minutes). The tumor volumes were measured every other day. Results: The effective diameter of Fe3O4@Au NPs was approximately 37.8 nm. The average tumor volume in control group, NPs group, laser irradiation group, NPs + laser irradiation group and NPs + magnet + laser irradiation group increased to 47.3, 45.3, 32.8, 19.9 and 7.7 times, respectively in 2 weeks. No obvious change in the average body weight for different groups occurred. Conclusion: Results demonstrated that magnetically targeted nano-photothermal therapy of cancer described in this paper holds great promise for the selective destruction of tumors.

Photobiomodulation with single and combination laser wavelengths on bone marrow mesenchymal stem cells: proliferation and differentiation to bone or cartilage.

Tissue engineering aims to take advantage of the ability of undifferentiated stem cells to differentiate into multiple cell types to repair damaged tissue. Photobiomodulation uses either lasers or light-emitting diodes to promote stem cell proliferation and differentiation. The present study aimed to investigate single and dual combinations of laser wavelengths on mesenchymal stem cells (MSCs). MSCs were derived from rabbit iliac bone marrow. One control and eight laser irradiated groups were designated as Infrared (IR, 810nm), Red (R, 660nm), Green (G, 532nm), Blue (B, 485nm), IR-R, IR-B, R-G, and B-G. Irradiation was repeated daily for 21days and cell proliferation, osseous, or cartilaginous differentiation was then measured. RT-PCR biomarkers were SOX9, aggrecan, COL 2, and COL 10 expression for cartilage and ALP, COL 1, and osteocalcin expression for bone. Cellular proliferation was increased in all irradiated groups except G. All cartilage markers were significantly increased by IR and IR-B except COL 10 which was suppressed by IR-B combination. ALP expression was highest in R and IR groups during osseous differentiation. ALP was decreased by combinations of IR with B and with R, and also by G alone. R and B-G groups showed stimulated COL 1 expression; however, COL 1 was suppressed in IR-B, IR-R, and G groups. IR significantly increased osteocalcin expression, but in B, B-G, and G groups it was reduced. Cartilage differentiation was stimulated by IR and IR-B laser irradiation. The effects of single or combined laser irradiation were not clear-cut on osseous differentiation. Stimulatory effects on osteogenesis were seen for R and IR lasers, while G laser had inhibitory effects.

Antimicrobial photodynamic therapy of Lactobacillus acidophilus by indocyanine green and 810-nm diode laser.

This study investigated the efficacy of photodynamic therapy (PDT) using EmunDo as a photosensitizer against Lactobacillus acidophilus. A gallium aluminum arsenide diode laser was used in this experiment (810 nm, CW). Standard suspensions of Lactobacillus acidophilus were divided into six groups by treatment: 1) EmunDo, 2) diode laser (100 mW, 90 s), 3) diode laser (300 mW, 30 s); 4) EmunDo + diode laser (100 mW, 90 s), 5) EmunDo + diode laser (300 mW, 30 s), 6) control (no treatment). Bacterial suspensions from each group were subcultured onto the surface of MRS agar plates immediately and 24 h after treatment, and the viable microorganisms of Lactobacillus acidophilus were counted. The data were analyzed by ANOVA and student's t-test at p < 0.05. There was a significant between-group difference in the number of Lactobacillus acidophilus colonies in cell cultures obtained at 24 h after treatment (p < 0.001). The viable counts were significantly lower in EmunDo and both PDT groups, as compared to the other groups (p < 0.05). In the control and laser-irradiated groups, the number of colonies increased significantly at 24 h compared to the immediately after treatment (p < 0.05), whereas in both PDT groups, the number of colonies showed a significant reduction after 24 h of therapy (p < 0.05). Under the conditions used in this study, L. acidophilus colonies were susceptible to PDT after sensitization with EmunDo and exposure to diode laser. These findings imply that PDT is capable to reduce cariogenic bacteria, potentially leading to more conservative cavity preparation.

Natural melanin-loaded nanovesicles for near-infrared mediated tumor ablation by photothermal conversion

Photothermal therapy requires a biocompatible material to absorb near-infrared (NIR) light and generate sufficient heat. Herein, we suggest natural melanin-loaded nanovesicles (melasicles) as photothermal therapeutic agents (PTA) for NIR mediated cancer therapy in vivo. The mean size of these melasicles was 140 ± 15 nm. They showed excellent colloidal stability. After irradiation from 808 nm NIR laser at 1.5 W cm−2, the melasicles showed good photothermal conversion efficiencies both in vitro and in vivo. In drug release study, laser irradiation increased fluidity of vesicle membrane due to photothermal generation from melanin. Initial drug release in the laser irradiation group was higher than that in the no laser irradiation group. After injecting the melasicles into tail veins of CT-26 bearing mice, tumors were suppressed or eliminated after irradiation at 1.5 W cm−2 for 5 min once or twice. These results suggest that melasicles could be used as attractive PTA for cancer therapy and localized drug release.

Effects of different Er,Cr:YSGG laser parameters on dentin shear bond strength and interface morphology: an in vitro study

The aim of this in vitro study is to evaluate the effect of Er,Cr:YSGG laser parameters, specifically power (Watt) and frequency (Hertz), throughout both, shear bond strength (SBS) and dentin-composite interface morphology, when using laser etch as an alternative to acid etching with a “two-step” total etch adhesive. Thirty-six human sound molars were mounted on acrylic blocks, randomly divided into six groups, six teeth into each group, where five teeth were selected for the SBS test, and one sectioned for the scanning electron microscope (SEM) analysis. Teeth were sliced occlusally to expose a flattened dentin surface, then grouped according to various treatments: control group, only treated with phosphoric acid etchant; and groups 1–5, only treated with Er,Cr,:YSGG laser irradiating at 3 W/25 Hz, 3 W/50 Hz, 4 W/25 Hz, 4 W/50 Hz, and 5 W/75 Hz respectively. The adhesive was applied followed by composite build up. SBS test was carried out using a universal testing machine. The resin-dentin interface was analyzed utilizing a SEM. The control group showed the highest SBS values (11.38 ± 2.03 Mpa). Group 5 (5 W/75 Hz) was the second highest (8.46 ± 1.82 Mpa), yet the highest among the entire laser-irradiated groups, showing a marginal/borderline significance with the control group (P = 0.044). Group 3 (4 W/25 Hz) came second through the laser samples (7.41 ± 0.97 Mpa). SEM analysis manifested premier retentive composite dentin interface among the control group and groups 5 and 3. When applying Er,Cr,:YSGG laser solely for dentin etching, adjusting the settings to a power of 5 W and frequency at 75 Hz will lead to optimum results regarding both SBS and interface morphology.

Photodynamic therapy using talaporfin sodium induces heme oxygenase-1 expression in rat malignant meningioma KMY-J cells.

Photodynamic therapy (PDT) using talaporfin sodium (TS) is tumor cell-selective less invasive therapy for the treatment of malignant glioma. We previously demonstrated that PDT using TS (TS-PDT) treatment exhibits anti-tumor activity against not only glioblastoma cells but also malignant meningioma cells. In general, various stress response proteins have been reported to affect the sensitivity determination for anticancer agents against tumor cells. However, the relationship between the therapeutic effect of TS-PDT and stress response systems in tumor cells is not adequately investigated. In this study, we investigated the gene expression of stress response proteins, including Sod1, Cat1, Gstp1, Gpx1, Nqo1, and Hmox1, in rat malignant meningioma KMY-J cells after treatment of TS-PDT. TS-PDT treatment significantly decreased the cell viability when compared with the no laser irradiation group. In morphological observation, TS at 25.6 µM treatment exhibited a significant cytotoxic effect after 12 hr of laser irradiation to KMY-J cells. After 3 and 6 hr of TS-PDT treatment, mRNA expression of heme oxygenase-1 (HO-1, encoded by Hmox1) was significantly increased by TS-PDT treatment. We also demonstrated that zinc protoporphyrin IX (ZnPPIX), a HO-1 inhibitor, significantly augmented the cytotoxic effect of TS-PDT treatment. These data suggest that HO-1 induction may contribute to a protective response against TS-PDT treatment in the malignant meningioma cells and may attenuate the therapeutic effect for TS-PDT treatment.

Effects of laser acupoint irradiation on energy metabolism of brain tissue of rats with cerebral ischemia-reperfusion

The protective effect and mechanism of low-intensity laser acupoint irradiation on focal cerebral ischemia-reperfusion (CIR) injury in rats were investigated. Male Sprague-Dawley rats were randomly divided into a sham group, a CIR model (model) group, and a model plus laser irradiation (laser) group. The focal CIR model was induced by middle cerebral artery occlusion in all except the rats in the sham group. After modeling, the Baihui, Mingmen, and left Zusanli points of the rats in the laser group were irradiated with 15 mW using a semiconductor laser, and each point was irradiated for 15 min once a day for 7 d. The treatments used in the sham and model groups were the same as in the laser group except that the laser output power was zero. After treatment, the expressions of serum superoxide dismutase (SOD) activity and serum malonaldehyde (MDA) content, the expression of growth-associated protein (GAP-43), the activities of succinic dehydrogenase and lactic dehydrogenase in brain tissue, were measured. The results showed that acupoint irradiation with a semiconductor laser can improve energy metabolism, enhance the expression of GAP-43, increase the levels of expression of serum SOD, and decrease the serum MDA content in a rat model of focal CIR, suggesting the mechanism for reduction of CIR injury.

Effect of antimicrobial photodynamic therapy (aPDT) on the sterilization of infected dentin in vitro.

The aim of this study was to evaluate the bactericidal effect of antimicrobial photodynamic therapy (aPDT) on an infected dentin model. Dentin plates were prepared from extracted human molars and infected through immersion in a solution of Streptococcus mutans. The nine experimental groups consisted of two laser irradiation groups (650nm laser: 650 laser and 940nm laser: 940 laser), two photosensitizer groups (methylene blue: MB, and azulenocyanine: Azc), four aPDT groups (650nm laser irradiation of MB: 650 laser-MB, 650nm laser irradiation of Azc: 650 laser-Azc, 940nm laser irradiation of MB: 940 laser-MB and 940nm laser irradiation of Azc: 940 laser-Azc) and a control. The bactericidal effects on each group were evaluated by colony count and adenosine triphosphate (ATP) assays. Based on the results of the colony count assay, the 650 laser-MB and 940 laser-MB groups formed significantly fewer colonies than the other experimental groups. Significantly fewer colonies were observed in the 940 laser-Azc group than in the control, but significant differences in the numbers of colonies were not observed between the 650 laser-Azc and control groups. The 940 laser group formed slightly fewer colonies than the 650 laser group, but the difference was not significant. In addition, the number of colonies in the MB group was significantly less than the number in the Azc group. The results of the ATP assay were similar to those of the colony count assay. aPDT with MB showed a significant bactericidal effect on dentin plates infected with S. mutans.

Semiconductor laser irradiation improves root canal sealing during routine root canal therapy.

ObjectiveTo evaluate the effect of semiconductor laser irradiation on root canal sealing after routine root canal therapy (RCT).MethodsSixty freshly extracted single-rooted human teeth were randomly divided into six groups (n = 10). The anatomic crowns were sectioned at the cementoenamel junction and the remaining roots were prepared endodontically with conventional RCT methods. Groups A and B were irradiated with semiconductor laser at 1W for 20 seconds; Groups C and D were ultrasonically rinsed for 60 seconds as positive control groups; Groups E and F without treatment of root canal prior to RCT as negative control groups. Root canal sealing of Groups A, C and E were evaluated by measurements of apical microleakage. The teeth from Groups B, D and F were sectioned, and the micro-structures were examined with scanning electron microscopy (SEM). One way ANOVA and LSD-t test were used for statistical analysis (α = .05).ResultsThe apical sealing of both the laser irradiated group and the ultrasonic irrigated group were significantly different from the control group (p<0.5). There was no significant difference between the laser irradiated group and the ultrasonic irrigated group (p>0.5). SEM observation showed that most of the dentinal tubules in the laser irradiation group melted, narrowed or closed, while most of the dentinal tubules in the ultrasonic irrigation group were filled with tooth paste.ConclusionThe application of semiconductor laser prior to root canal obturation increases the apical sealing of the roots treated.

Pulsed low-level infrared laser alters mRNA levels from muscle repair genes dependent on power output in Wistar rats

Satellite cells are present in skeletal muscle functioning in the repair and regeneration of muscle injury. Activation of these cells depends on the expression of myogenic factor 5 (Myf5), myogenic determination factor 1(MyoD), myogenic regulatory factor 4 (MRF4), myogenin (MyoG), paired box transcription factors 3 (Pax3), and 7 (Pax7). Low-level laser irradiation accelerates the repair of muscle injuries. However, data from the expression of myogenic factors have been controversial. Furthermore, the effects of different laser beam powers on the repair of muscle injuries have been not evaluated. The aim of this study was to evaluate the effects of low-level infrared laser at different powers and in pulsed emission mode on the expression of myogenic regulatory factors and on Pax3 and Pax7 in injured skeletal muscle from Wistar rats. Animals that underwent cryoinjury were divided into three groups: injury, injury laser 25 Mw, and injury laser 75 mW. Low-level infrared laser irradiation (904 nm, 3 J cm−2, 5 kHz) was carried out at 25 and 75 mW. After euthanasia, skeletal muscle samples were withdrawn and the total RNA was extracted for the evaluation of mRNA levels from the MyoD, MyoG, MRF4, Myf5, Pax3, and Pax7 gene. Pax 7 mRNA levels did not alter, but Pax3 mRNA levels increased in the injured and laser-irradiated group at 25 mW. MyoD, MyoG, and MYf5 mRNA levels increased in the injured and laser-irradiated animals at both powers, and MRF4 mRNA levels decreased in the injured and laser-irradiated group at 75 mW. In conclusion, exposure to pulsed low-level infrared laser, by power-dependent effect, could accelerate the muscle repair process altering mRNA levels from paired box transcription factors and myogenic regulatory factors.

Photobiomodulation Triple Treatment in Peripheral Nerve Injury: Nerve and Muscle Response.

Muscle preservation or decrease in muscle degeneration and progressive atrophy are major challenges in patients with severe peripheral nerve injury (PNI). Considerable interest exists in the potential therapeutic value of laser phototherapy (photobiomodulation) for restoring denervated muscle atrophy and for enhancing regeneration of severely injured peripheral nerves. As previously published, the laser phototherapy has a protective and immediate effect in PNI. Laser phototherapy in the early stages of muscle atrophy may preserve the denervated muscle by maintaining creatinine kinase (CK) activity and the amount of acetylcholine receptor (AChR). In the present study, the effectiveness of triple treatment laser phototherapy, namely, applied simultaneously at three areas: injured area of the peripheral nerve, corresponding segments of the spinal cord, and corresponding denervated muscle (triple treatment), was evaluated for the treatment of incomplete PNI in rats with the ultimate goal of achieving improved limb function. Forty-five days after the sciatic nerve insult, all rats regained normal walking (functional sciatic index values returned to baseline); however, the long laser irradiation (7 min) group presented the fastest recovery as opposed to short laser irradiation (3 min). A histological evaluation of the nerves revealed that long laser irradiation led to a higher amount of neuronal fibers that were larger than 4 μm (543 ± 76.8, p < 0.01) than short irradiation (283 ± 35.36). A histological evaluation of muscular atrophy showed that long laser irradiation evolved with significantly less muscle atrophy (8.06% ± 1.23%, p < 0.05) than short irradiation (24.44% ± 7.26%). The present study and our previous investigations showed that the laser phototherapy increases biochemical activity and improves morphological recovery in muscle and, thus, could have direct therapeutic applications on muscle, especially during progressive atrophy resulting from PNI.

Zirconia Surface Treatment by Different Output Powers of Er: YAG Laser and Sandblasting: SEM Evaluation

Background: Application of zirconia in dentistry has increased due to its good properties. Since zirconia is not possible to be etched, evaluation of the other methods of surface treatment is important. Objectives: The aim of this study was to evaluate zirconia surfaces treated by different output powers of Er: YAG laser and sandblasting technique by scanning electron microscope (SEM). Materials and Methods: 15 specimens were prepared of 3Y-TZP ceramic material. After polishing of all the samples, divided into 5 groups; control group, 1.5 W Er: YAG laser irradiated group, 2.5W Er: YAG laser irradiated group, 3.5 W Er: YAG laser irradiated and sandblasted group. Then SEM image of each group were prepared and analyzed. Results: The SEM images of study groups showed there is no significant difference between control group and laser groups at × 3000, but at the more magnifications (× 15000 and × 60000), with increasing laser power, surface roughness and deformation of crystals increases. SEM of Sandblasted group showed a change in surface texture with the formation of microretentive grooves and deformation of zirconia crystals shape. Conclusions: By increasing the Er: YAG laser power on zirconia ceramics, the surface roughness increases but not impressive. Application of sandblasting technique on zirconia provides greater surface roughness than Er: YAG laser treatment. 1.5 W (150 mJ) Er: YAG laser radiation has no significant effect on surface morphology of zirconia but 2.5 W (250 mJ) and 3.5 W (350 mJ) outputs, change the surface morphology.

Responses of He-Ne laser irradiation on agronomical characters and chlorogenic acid content of brinjal (Solanum melongena L.) var. Mattu Gulla

Exposure to laser irradiation on seeds brings about the changes in agronomical characteristics of the plants. Solanum melongena L. var. Mattu Gulla, a variety of brinjal is of high economic value due to its unique colour and flavour. The aim of the study was to understand the influence of Helium-Neon (He-Ne) laser irradiation on agronomical characters of Solanum melongena L. var. Mattu Gulla in the field conditions. Various growth characteristics including seed germination percentage, survival rate, plant height, number of branches, and flowers and fruits were estimated during different developmental stages of the brinjal. In addition, the chlorogenic acid content of fruits obtained from the laser irradiated seeds were quantified using reversed-phase high-performance liquid chromatography (RP- HPLC). The plants from the seeds irradiated with different doses (20, 25 and 30J/cm2) of He-Ne laser showed significant enhancement on the growth characteristics when compared to the non-irradiated control groups. He-Ne laser irradiation also improved the yield characteristics of the plants significantly in in vivo conditions in comparison with control group. 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed using methanolic extract of matured fruit of Mattu Gulla on HepG2 and fibroblast cell lines. The IC50 values of fruit extract from laser irradiated groups were found to be similar to non-irradiated control groups. Chlorogenic acid content was found to be higher in 20J/cm2 and lower in 30J/cm2 treated fruit tissue. The current study thus elucidates the role of He-Ne laser as a biostimulator on brinjal var. Mattu Gulla not only in the in vitro conditions but also in the in vivo field conditions.

Effect of the transdermal low-level laser therapy on endothelial function

The effect of low-level laser therapy (LLLT) on the cardiovascular system is not fully established. Since the endothelium is an important endocrine element, establishing the mechanisms of LLLT action is an important issue.The aim of the study was to evaluate the effect of transdermal LLLT on endothelial function.In this study, healthy volunteers (n = 40, age = 20–40 years) were enrolled. N = 30 (14 female, 16 male, mean age 30 ± 5 years) constituted the laser-irradiated group (LG). The remaining 10 subjects (6 women, 4 men, mean age 28 ± 5 years) constituted the control group (CG). Participants were subjected to LLLT once a day for three consecutive days. Blood for biochemical assessments was drawn before the first irradiation and 24 h after the last session. In the LG, transdermal illumination of radial artery was conducted (a semiconductor laser λ = 808 nm, irradiation 50 mW, energy density 1.6 W/cm2 and a dose 20 J/day, a total dose of 60 J). Biochemical parameters (reflecting angiogenesis: vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), angiostatin; antioxidative status: glutathione (GSH) and the nitric oxide metabolic pathway: symmetric dimethylarginine (SDMA), asymmetric dimethylarginine (ADMA) and l-arginine) were assessed. In the LG, a significant increase in GSH levels and considerable decrease in angiostatin concentration following the LLLT were observed. No significant differences in levels of the VEGF, FGF, SDMA, ADMA were observed.LLLT modifies vascular endothelial function by increasing its antioxidant and angiogenic potential. We found no significant differences in levels of the nitric oxide pathway metabolites within 24 h following the LLLT irradiation.

Protective effect of low level laser irradiation on liver ischemia-reperfusion injury in rats

Objective To investigate the protective effect of low level laser irradiation on liver ischemia-reperfusion injury (HIRI) in rats. Methods Forty-five health male Sprague-Dawley rats were randomly divided into three groups: Sham group, ischemia-reperfusion group (Control group) and 1ow level laser irradiation group (LLLI group). After the hepatic inflow was occluded for 30 min and reperfused for 90 min, serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were determined, and the liver specimen were obtained for the determination of superoxide dismutase (SOD) activities and malondialdehyde (MDA) contents and for microscopic examinations. Results As compared with the Sham group, the levels of ALT [(577.98±134.65) U/L, (233.11±108.23) U/L], AST [(1 213±314.8) U/L, (563.32±289.77) U/L], LDH [(2 985.96±478.88) U/L, (1 086.24±1 068.31) U/L], MDA [(106.87±30.34) U/L, (54.23±20.37) U/L)] in Control group and LLLI group was significantly increased (P<0.05), and the activity of SOD [(33.15±3.51) U/L, (59.11±7.01) U/L] was significantly lower than in Sham group (P<0.05). As compared with the Control group, the levels of ALT, AST, LDH and MDA in LLLI group were significantly reduced (P<0.05), and the activity of SOD was significantly elevated (P<0.05). Conclusion LLLI has a protective effect on rat livers against ischemia-reperfusion injury, which is related with antioxidation. Key words: Low level laser irradiation; Liver ischemia; Reperfusion injury; Superoxide dismutase; Malondialdehyde

Efficacy of uncommon surface treatment methods on titanium in order to improve bond strengths for adhesive cementation

The aim of this study is to comparison of effects of uncommon surface treatments, especially new alternatives on the adhesive strength between resin and titanium surfaces. Fifty-five titanium disks were prepared and they were separated into 5 groups as follows: (1) Control group; (2) Tribochemical treatment group in the laboratory; (3) Tribochemical treatment group in the clinic; (4) Acid etch group; and (5) Nd:YAG Laser-irradiated group. Surface roughness of the specimens was measured using a profilometer, and the topographic patterns were observed by scanning electron microscope. After these tests, resin cement was applied to the titanium samples. Shear bond test was performed via a universal testing machine at a crosshead speed of 0.5 mm/minute. In addition, the correlation between the surface roughness and bond strength was checked using Spearman correlation test (0.01 level). The highest surface roughness value was observed for the acid etch group (1.53 μm). The highest mean shear bond strength was recorded with the tribochemical procedure group in the laboratory (13.74 MPa) and the lowest with the control group (3.69 MPa). A positive correlation was found between the bond strength and surface roughness for all groups. All of the surface treatment methods that were used in present study increased the bond strength between resin and titanium except for the laser group.

Effects of Laser Treatment on the Bond Strength of Differently Sintered Zirconia Ceramics.

The purpose of this study was to investigate the effects of carbon dioxide (CO2) and Erbium-doped yttrium aluminum garnet (Er:YAG) laser irradiations on the shear bond strength (SBS) of differently sintered zirconia ceramics to resin cement. Eighty zirconia specimens were prepared, sintered in two different periods (short = Ss, long = Ls), and divided into four treatment groups (n = 10 each). These groups were (a) untreated (control), (b) Er:YAG laser irradiated with 6 W power for 5 sec, (c) CO2 laser with 2 W power for 10 sec, (d) CO2 laser with 4 W power for 10 sec. Scanning electron microscope (SEM) images were recorded for each of the eight groups. Eighty composite resin discs (3 × 3 mm) were fabricated and cemented with an adhesive resin cement to ceramic specimens. The SBS test was performed after specimens were stored in water for 24 h by an universal testing machine at a crosshead speed of 1 mm/min. Data were statistically analyzed with two way analysis of variance (ANOVA) and Tukey honest significant difference (HSD) test (α = 0.05). According to the ANOVA, the sintering time, surface treatments and their interaction were statistically significant (p < 0.05). Although each of the laser-irradiated groups were significantly higher than the control groups, there was no statistically significant difference among them (p > 0.05). Variation in sintering time from 2.5 to 5.0 h may have influenced the SBS of Yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics. Although CO2 and Er:YAG laser irradiation techniques may increase the SBS values of both tested zirconia ceramics, they are recommended for clinicians as an alternative pretreatment method.

Structural and Morphological Changes in Human Dentin after Ablative and Subablative Er:YAG Laser Irradiation.

This study investigated the influence of Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser on microhardness, chemical composition and subsurface morphology of dentin cavity walls. Forty sound human premolars were selected and randomly assigned into four groups. Class V cavities were prepared either with an Er:YAG laser (groups 1 and 2; 15 Hz, 250 mJ for enamel, 10 Hz, 200 mJ for dentin) or with a high speed handpiece (groups 3 and 4). The specimens in groups 1 and 3 served as the control, whereas those in groups 2 and 4 were exposed to subablative laser irradiation following cavity preparation (10 Hz, 50 mJ). After bisecting the specimens, one half was subjected to microhardness assessment and the other half was evaluated by SEM-EDS analysis. Microhardness was significantly greater in the specimens prepared by both ablative and subablative laser irradiation (group 2) than that of the bur-prepared cavities (groups 3 and 4) (P < 0.05). The quantity of calcium ion was significantly greater in cavities prepared by the Er:YAG laser (groups 1 and 2) compared to that of the bur cavities (groups 3 and 4) (P < 0.05). Subablative irradiation improved microhardness and weight percentage of calcium ion in both laser and bur cavities, but the difference was not significant compared to that of the relevant control group (P > 0.05). Cavity preparation with an Er:YAG laser could be considered as an alternative to the conventional method of drilling, as it enhances the mechanical and compositional properties of lased dentin, especially when combined by subablative irradiation.