Journal of clinical laser medicine & surgery最新文献

Objective: The purpose of this study was to determine the effect of combined CO2 and Er:YAG laser irradiation on normal (NF) and keloid (KF) facial dermal fibroblast production of TGF-beta1 and bFGF.

Background data: Keloids produce excess collagen. TGF-beta1 is integral to the growth and stimulation of fibroblasts and collagen; bFGF inhibits collagen synthesis. TGF-beta1 and bFGF production influence wound healing and may be manipulated by laser irradiation.

Materials and methods: Human normal fibroblasts (NF) and keloid fibroblasts (KF) (2 x 10(4) cells/mL in serum-free media) were exposed to 1.7 J/pulse Er:YAG laser energy and CO2 delivered at either 3 or 5 W and at a duty cycle of 25%, 50%, or 100%. TGF-beta1 and bFGF were assayed using a quantitative ELISA.

Results: KF demonstrated a statistically significant mean population doubling time (PDT) when compared with NF (p=0.01). Irradiated KF and NF had longer PDTs than controls. All NF, excluding one irradiated group, and the three KF treated with 3 W secreted more bFGF than controls. Irradiated KF secreted less TGF-beta1 than controls. Significance was reached with the two groups exposed to 3 W at a duty cycle of 25% and 50% (p=0.04 and 0.05, respectively). All irradiated NF secreted less TGF-beta1 than controls.

Conclusion: The combined CO2 and Er:YAG laser increased the release of bFGF, which has been shown to promote tightly organized collagen bundles, and decreased the concentration of TGF-beta1, which has also been shown to promote fibrosis formation. This laser may have a future role in keloid treatment, as well as normal facial scar prevention.

Objective: The aim of this study was to assess histologically the effect of LLLT (lambda830 nm) on the repair of standardized bone defects on the femur of Wistar albinus rats grafted with inorganic bovine bone and associated or not to decalcified bovine cortical bone membrane.

Background data: Bone loss may be a result of several pathologies, trauma or a consequence of surgical procedures. This led to extensive studies on the process of bone repair and development of techniques for the correction of bone defects, including the use of several types of grafts, membranes and the association of both techniques. There is evidence in the literature of the positive effect of LLLT on the healing of soft tissue wounds. However, its effect on bone is not completely understood.

Materials and methods: Five randomized groups were studied: Group I (Control); Group IIA (Gen-ox); Group IIB (Gen-ox + LLLT); Group IIIA (Gen-ox + Gen-derm) and Group IIIB (Gen-ox + Gen-derm + LLLT). Bone defects were created at the femur of the animals and were treated according to the group. The animals of the irradiated groups were irradiated every 48 h during 15 days; the first irradiation was performed immediately after the surgical procedure. The animals were irradiated transcutaneously in four points around the defect. At each point a dose of 4 J/cm2 was given (phi approximately 0.6 mm, 40 mW) and the total dose per session was 16 J/cm2. The animals were humanely killed 15, 21, and 30 days after surgery. The specimens were routinely processed to wax, serially cut, and stained with H&E and Picrosirius stains and analyzed under light microscopy.

Results: The results showed evidence of a more advanced repair on the irradiated groups when compared to non-irradiated ones. The repair of irradiated groups was characterized by both increased bone formation and amount of collagen fibers around the graft within the cavity since the 15th day after surgery, through analysis of the osteoconductive capacity of the Gen-ox and the increment of the cortical repair in specimens with Gen-derm membrane.

Conclusion: It is concluded that LLLT had a positive effect on the repair of bone defect submitted the implantation of graft.

Objective: The aim of the present study was to investigate the transformations of red blood cells produced by low-intensity infrared laser radiation (810 nm).

Background data: Low-intensity (the output power of a laser device in the milliwatt range) laser radiation as a local phototherapeutic modality is characterized by its ability to induce non-thermic, nondestructive photobiological processes in cells and tissues. However, the exact theory concerning the therapeutic effects of laser biostimulation has not been developed.

Materials and methods: The suspensions of human erythrocytes in PBS (10% hematocrit) were irradiated with near-infrared (810 nm) therapy laser at different light doses (0-20 J) and light power (fluence rate; 200 or 400 mW) at 37 degrees C. As the parameters characterizing the cell structural and functional changes membrane acetylcholinesterase (AchEase) activity, the membrane potential, the level of intracellular glutathione, the level of products of membrane lipid peroxidation, and the cell osmotic stability were measured.

Results: It was found that near-infrared low-intensity laser radiation produced complex biphasic dose-dependent changes of the parameters of AchEase reaction in the dose-dependent manner: at smaller doses of radiation (6 J) the maximal reaction rate and Michaelis-Menten constant value decreased, and at higher radiation doses these parameters increased. No significant changes of erythrocyte stability, cellular redox state (reduced glutathione or lipid peroxidation product levels), or cell membrane electrochemical potential were observed.

Conclusion: Low-intensity near-infrared laser radiation (810 mn) produced AchEase activity changes, reflecting the effect of light on the enzyme due to energy absorption. Protein molecule conformational transitions and enzyme activity modifications in cells have been suggested as laser radiation-induced events.

Objective: The aim of this study was to compare the efficacy of root canal cleanliness with and without Nd:YAP laser and to assess the effect of the laser on the mineral content of the dentin.

Background data: A high degree of cleanliness of the canal when using the Nd:YAG laser has been shown while the laser is in contact with the canal wall. A new Nd:YAP laser has been studied recently, which is considered to be superior to the Nd:YAG with regard to antibactericidal ability due to its 1.34 micro m wavelength, which is in the infra-red range. This wavelength is absorbed better in water than that of Nd:YAG.

Materials and methods: Fourteen extracted single rooted premplars were divided into two groups. In group 1, canals were cleaned, instrumented, and shaped with K files. In group 2, initial preparation was done using K files and completed with a Nd:YAP laser. Teeth were then split longitudinally and submitted to scanning electron microscopy.

Results: The cleanliness of the laser-treated teeth was significantly greater than teeth treated with K files alone (p < 0.05). No difference in Ca and P content was detected when the use of K files was compared to the use of laser.

Conclusion: It appears that the Nd:YAP laser improves the cleanliness of the root canal. However, since the Nd:YAP laser serves as an addition to K files, its clinical value for replacing conventional root canal instrumentation remains to be determined.

Objective: The aim of our study was to explore the wavelength dependence of welding efficacy. Ex vivo samples of human and porcine aorta and skin tissues were investigated using a tunable Cr(4+):yttrium aluminum garnet (YAG) laser.

Background data: Tissue welding is possible using laser light in the NIR spectral range. Collagen bonding in the tissue induced by thermal, photothermal, and photochemical reactions-or a combination of all of these-is thought to be responsible for tissue welding. Laser tissue welding (LTW) has gained success in the laboratory using animal models. Transition from laboratory to clinical application requires the optimization of welding parameters.

Materials and methods: A near-infrared (NIR) Cr(4+):YAG laser was used to weld ex vivo samples of human and porcine aorta and skin at wavelengths from 1430 to 1470 nm. Welding efficacy was monitored by measuring the tensile strength of the welded tissue and the extent of collateral tissue damage. Tensile strengths were measured using a digital force gauge. Changes in tissue morphology were evaluated using optical and scanning electron microscope (SEM). Fluorescence imaging of the welded areas was also used to evaluate molecular changes following tissue welding.

Results: Full-thickness tissue bonding was observed with porcine aorta samples. No collateral damage of the aorta samples was observed. Tissue denaturation was observed with human aorta, human skin, and porcine skin samples. The optimum tensile strength for porcine and human aorta was 1.33 +/- 0.15 and 1.13 +/- 0.27 kg/cm2, respectively, at 1460 nm, while that for porcine and human skin was 0.94 +/- 0.15 and 1.05 +/- 0.19 kg/cm2, respectively, achieved at 1455 nm. The weld strength as a function of wavelength demonstrated a correlation with the absorption spectrum of water. Fluorescence imaging of welded aorta and skin demonstrated no significant changes in collagen and elastin emission at the weld site.

Conclusion: The observation that welding strength as a function of wavelength follows the absorption bands of water suggests that absorption of light by water plays a significant role in laser tissue welding.

Objective: The purpose of this study was to determine the effect of pulse frequencies of low-level laser therapy (LLLT) on bone nodule formation in rat calvarial cells in vitro.

Background data: Various photo-biostimulatory effects of LLLT, including bone formation, were affected by some irradiation factors such as total energy dose, irradiation phase, laser spectrum, and power density. However, the effects of pulse frequencies used during laser irradiation on bone formation have not been elucidated.

Materials and methods: Osteoblast-like cells isolated from fetal rat calvariae were irradiated once with a low-energy Ga-Al-As laser (830 nm, 500 mW, 0.48-3.84 J/cm2) in four different irradiation modes: continuous irradiation (CI), and 1-, 2-, and 8-Hz pulsed irradiation (PI-1, PI-2, PI-8). We then investigated the effects on cellular proliferation, bone nodule formation, alkaline phosphatase (ALP) activity, and ALP gene expression.

Results: Laser irradiation in all four groups significantly stimulated cellular proliferation, bone nodule formation, ALP activity, and ALP gene expression, as compared with the non-irradiation group. Notably, PI-1 and -2 irradiation markedly stimulated these factors, when compared with the CI and PI-8 groups, and PI-2 irradiation was the best approach for bone nodule formation in the present experimental conditions.

Conclusion: Since low-frequency pulsed laser irradiation significantly stimulates bone formation in vitro, it is most likely that the pulse frequency of LLLT an important factor affecting biological responses in bone formation.

Objective: We determined the effect of polychromatic light-emitting diodes (LED) in burn healing of non-diabetic and streptozotocin-induced diabetic rats.

Background data: LEDs were used as the light source for phototherapy.

Materials and methods: The polychromatic LED is a cluster of 25 diodes emitting photons at wavelengths of 510-543, 594-599, 626-639, 640-670, and 842-879 nm with 272-mW output power. Age-matched, male Sprague-Dawley rats (n = 30) were used. Streptozotocin (70 mg/kg) was used for diabetes induction. Rat weight, hyperglycemia, and glycosuria were monitored for the first 3 days and weekly thereafter. Rats were anesthetized and shaved after 1 week of diabetes. Burn areas of 1.5 +/-.03 cm2 were created using a metal rod pre-heated up to 600 degrees C that was applied for 2 sec. Diabetic and non-diabetic rats were randomized into the following treatment groups: control, 5, 10, 20, and 30 J/cm2. Light treatment commenced after burn infliction and was repeated three times per week. Burn areas were measured daily.

Results: Burn healing was impaired significantly during diabetes by -46.17%. Polychromatic LED treatment using 5, 10, 20, and 30 J/cm2 incident doses influenced healing by 6.85%, 4.93%, -4.18%, and -5.42% in the non-diabetic rats; and 73.87%, 76.77%, 60.92%, and 48.77% in the diabetic rats, relative to their controls, respectively.

Conclusion: The effect of polychromatic LED in non-diabetic rats was insignificant; however, it simulated the trend of stimulation and inhibition seen using low-level lasers. Significant stimulation observed in the diabetic rats demonstrated the usefulness of polychromatic LED in diabetic burn healing.