The technique of phosphorescence quenching by O₂ (PQ) allows the non-invasive measurement of the partial pressure of oxygen in blood (pO₂^blood). This technique and its application to the investigation of the pO₂^blood in the microvasculature of the retina and optic nerve head (ONH) of two animal species is described. Using the imaging mode of PQ, 2-dimensional pO₂^blood maps were obtained to investigate the response of the pO₂^blood to various physiological stimuli in miniature pigs and the effect of experimental glaucoma in monkeys. Applied in its focal mode, PQ allows measurements of the pO₂^blood with a time resolution of 1 second and is adequate to investigate the pO₂^blood time course during light stimulation.

Thermal stimulation of single cells and cell layers is used for investigations of temperature associated processes like necrosis or apoptosis. Simulations of temperature distributions in layered structures on various substrates are presented. In order to verify the simulations a diode pumped IR-cw laser system was developed. The TEM₀₀ output beam at a wavelength of 2.8 micrometers was focused on biological material to compare visible effects with the calculations.

Background: Protein denaturation in the fs-ns time regime is of fundamental interest for high precision applications in laser tissue interaction. Conjugates of colloidal gold coupled to proteins are presented as a model system for investigating ultrafast protein denaturation. It is expected that irradiation of such conjugates in tissue using pico- up to nanosecond laser pulses could result in effects with a spatial confinement in the regime of single macromolecules up to organelles. Materials and Methods: Experiments were done with bovine intestinal alkaline phosphatase (aP) coupled to 15 nm colloidal Gold. This complex was irradiated at 527 nm/ 532 nm with a variable number of pico- and nanosecond pulses. The radiant exposure per pulse was varied from 2 to 50 mJ/cm² in the case of the picosecond pulses and 10 to 500 mJ/cm² in the case of the nanosecond pulses. Denaturation was detected as a loss of protein function with the help of the uorescence substrate 4MUP. Results and Discussion: Irradiation did result in a steady decrease of the aP activity with increasing radiant exposures and increasing number of pulses. Inactivations up to 80% using 35 ps pulses at 527 nm with 50 mJ/cm² and a complete inactivation induced by 16 ns pulses at 450 mJ/cm² are discussed. The induced temperature in the particles and the surrounding water was calculated using Mie's formulas for the absorption of the nanometer gold particles and an analytical solution of the equations for heat diffusion. The calculated temperatures suggest that picosecond pulses heat a molecular scaled area whereas nanosecond pulses could be used for targeting larger cellular compartiments. It is difficult to identify one of the possible damage mechanisms, i.e. thermal denaturation or formation of micro bubbles, from the dependance of the inactivation on pulse energy and number of applied pulses. Therefore experiments are needed to further elucidate the damage mechanisms. The observed inactivation dependencies on applied energy and radiant power can not be explained with one or two photon photochemistry. In conclusion, denaturing proteins irreversibly via nanoabsorbers using pico-/ nanosecond laser pulses is possible. The expected confinement of the heat to the nanoabsorbers suggests that denaturation of proteins with nanometer precision could be possible with this approach. However, the mechanism of protein inactivation, which is part of present investigations, is crucial for the precision of such nanoeffects.

One of the main reasons of low quality filling is breaking Ca-P balance in hard tissues. Our research was done with the purpose of studying the influence of low intensity lasers, diodic radiation, the newest filling and bonding systems on the processes of mineral metabolism in hard dental tissues while filling a tooth. 250 patients having caries and its compli-cations were examined and treated. Our complex research included: visual and instrumental examination, finding out the level of oral cavity hygiene, acid enamel biopsy, scanning electronic microscopy and X-ray spectrum microanalysis. Filling processes may produce a negative effect on mineral metabolism of hard dental tissues the latter is less pronounced when applying fluoride-containing filling materials with bonding systems. It has also been found that bonding dentin and enamel systems are designed for both a better filling adhesion (i.e. mechanical adhesion) and migration of useful microelements present in them by their sinking into hard dental tissues (i.e. chemical adhesion). Our research showed a positive influence of low intensity laser and diodic beams accompanying the use of modern filling and bonding systems on mineral metabolism of hard dental tissues.

In a previous study we have found that the photodynamic modality PUVB (8-methoxy-Psoralen + UVB) reduces luminal narrowing after arterial endovascular injury. We hypothesized that PUVB may modulate the arterial mechanical properties and tested this hypothesis by measuring the stress as a function of the strain in segments of carotid artery. Furthermore, we have investigated the potential for PUVB-induced cross-linking of extracellular matrix proteins by gel electrophoresis. It was found that both techniques were suitable for testing our hypotheses as evidenced by a statistically significant difference for the positive control. However, no differences between A) control, B) sensitizer only, C) light only and D) PUVB-treated samples could be found with respect to macro- and micro-mechanical properties. Therefore, the hypothesis that PUVB mediates its luminal narrowing reduction effect by directly changing the arterial mechanical properties should be rejected.

Background. Endocardial laser revascularization (ELR) is a new technique to treat patients with severe coronary artery disease (CAD) in a percutaneous approach. The results show a significant improvement of symptoms, but the mechanism of action is still unknown. One main theory is the angiogenesis for which Vascular Endothelial Growth Factor (VEGF) is the keypromotor. We investigated immunohistochemically the VEGF-expression after ELR in porcine hearts over a timeperiod of four weeks. Methods. ELR was performed with a single-pulse Thulium:YAG laser. 15 pigs were treated with ELR and the hearts were harvested at five timeperiods: directly (group I), 3 days (group II), 1 week (group III), 2 weeks (group IV) and 4 weeks (group V) after ELR. Each group consisted of three pigs. Immunohistochemically the VEGF-expression was assessed by staining with a polyclonal antibody against VEGF and cellcounting using an expression index (VEGF-EI) Results. A maximum of VEGF-expression was found three days (group II) after ELR with a VEGF-EI of 97%. At 1 week (group III) the VEGF-EI was similar high with 93%. Along the timecourse the index decreased to 22% at 4 weeks (groupV). Conclusions. Our findings show that ELR leads to an local upregulation of VEGF around the channels. The resulting angiogenesis could be the mechanism for the relief of angina.

Low-intensity laser therapy (LILT) with adequate wavelength, intensity, and dose can accelerate tissue repair. However, there is still disperse information about light characteristics. Several works indicate that laser polarization plays an important role on the wound healing process. This study was conducted to verify the degree of linear polarization in normal and pathological rat skin samples. Artificial burns about 6 mm in diameter were created with liquid N₂ on the back of the animals. The degree of polarization was measured in normal and pathological skin samples. It was verified that linearly polarized light can survive in the superficial layers of skin and it can be more preserved in skin under pathological condition when compared with health skin. The present study supports the hypothesis that polarized laser radiation can be used to treat open wounds and improve the healing.

Interstitial Laser Photocoagulation (ILP) is a method of destroying lesions in the center of solid organs without the need for open surgery. Under image guidance, up to four needles are inserted percutaneously into the tumor through which thin optic fibers are passed into the target lesion. Low power laser light from a semiconductor laser is delivered to gently coagulate the tissue. This dead tissue is subsequently resorbed by the body's normal healing processes. Follow up is achieved with ultrasound imaging. One study is described for assessing ILP for benign fibroadenomas. Fibroadenomas were treated to assess how laser treated breast tissue healed in the long term and we have shown that the necrosed tissue is resorbed without complications over a period of months. Nevertheless, by following treated fibroadenomas (up to 35mm diameter) with ultrasound measurement at 3, 6 and 12 months, in 14 patients, only one lesion was still detectable 12 months after ILP. In appropriate cases, ILP could be an attractive option, as it leaves no scars and should not change the shape or size of the breast. If the present studies are successful, the plan is for a multi-center trial of minimally invasive, thermal ablation of breast cancers.

In order to perform refractive surgery, fs-laser pulses were focused into animal cornea. During histo-pathological analysis by light- and transmission-electron-microscopy new side effects of fs-photodisruption were found. Due to the high intensities at the focal region, self focusing followed by further nonlinear effects is observed, leading to streak formation inside the cornea and several micro-breakdowns on the sub-micron scale. The nature and origin of these streaks are further investigated.

Ten human third molars were used in this in vitro study to analyze the depth of dentin modification induced by a Nd:YAG laser. This technique has been used as a procedure to treat dentin hypersensitivity to air and to mechanics stimulation. Five techniques of sample preparation were used in this work but just one of them preserves the area under study for observation. The samples were irradiated with 170mJ of energy per pulse and an average depth of 100 micrometers of modification of the dentin was observed under scanning electron microscopy (SEM).

The effects of laser irradiation on human and animal organisms have been intensively studied, but the mechanism of this effect is not well understood and discussed on the level of hypothesis. The effect of low-intensity laser irradiation (LILI) depends both on its physical parameters (wavelength, power density, time etc.) and on optical properites of irradiated tissues. The biological response on LILT started from the resonance absorption of irradiation by specific acceptors-enzymes, pigments and other biochemical structures containing in most cases chromophores. At the same time, distribution of absorbed energy between oscillated-excited states of atomic groups of macromolecules with following energy migration takes place too. Such effects induced changes in intensity of lipid peroxidation (LPO) and transitions of cell membrane confirmations with following changes of membrane enzyme activity (adenilate cyclase, ATPase) and ion permeability of membranes [1-3]. The effects of LILT on antioxidant system (AOS) of organism (the main components of this system are reduced glutathione (GSH) and enzymes - superoxiddismutase (SOD), catalase, glutathione-peroxidase (GP) [3]), have been described mainly for helium-neon laser (HNL) and are contradictory. From the other hand the irradiation by HNL induced activation of the AOS components [1 ,4]. It may be due to the activation of oxygen molecules by red light and, thereby, oxidative processes in tissues, or due to the effects on membrane functions, for example, membranes of red blood cells. At the same time, the effect of inhibition by this type of LILT or absence of any effect of LILT on AOS was shown by other researchers [4,5].

We have shown by experimental investigations that cellular surgery (microdissection, optoporation, and optoinjection) with Nd:YAG laser pulses of 1064 nm and 532 nm wavelength relies on nonlinear absorption leading to optical breakdown and plasma formation at the laser focus. The present study explores possibilities of refining the breakdown effects by employing shorter pulse durations and irradiances that generate plasmas below the threshold for shock wave and bubble formation. Optical breakdown in water at NA = 0.9 and NA = 1.3 was simulated numerically for wavelengths of 1064 nm, 532 nm and 355 nm, and pulse durations of 6 ns, 30 ps and 100 fs. We used a rate equation model that allows the calculation of the temporal evolution of the free electron density r during breakdown. r (t) could be followed separately for the free electrons generated by multiphoton ionization and avalanche ionization. We obtained excellent agreement between the calculated and measured threshold values for breakdown with 6-ns pulses. The simulations predict that the energy threshold for cellular surgery can be reduced by a factor of 350-2600 (depending on wavelength) when the pulse duration is reduced from 6 ns to 100 fs. The calculated breakdown energies for 100 fs pulses focused by an objective with NA = 1.3 are 0.6 nJ at 355 nm, 1.6 nJ at 532 nm, and 3.9 nJ at 1064 nm. With ns-pulses at 1064 nm, the breakdown threshold is very sharp, i. e. there is either no effect at all, or a dense plasma is formed causing a micro-explosion. With shorter wavelengths and pulse durations, the threshold is smoother, and electron densities may be produced that stay below the threshold for explosive vaporization and bubble formation. This creates the possibility of achieving highly localized plasma-mediated chemical or thermal changes in the cell. We conclude that both the reduced energy threshold and the smoother breakdown process with fs pulses bear a large potential for the refinement of intracellular surgery.

We developed an interferometric technique in order to detect microbubble formation within porcine retinal pigment epithelial (RPE) cells ex vivo after short pulsed laser exposure (527nm, 350ns). The irradiated surface of the RPE tissue samples was monitored by a Michelson interferometer. The obtained interferometric transients revealed bubble dynamics and were compared to optoacoustic transients recorded simultaneously. This interferometric technique might be useful for in vivo dosimetry during selective RPE-treatment.

Q-switched TEM₀₀ thulium laser ((lambda) = 2.01 micrometers , 300 ns FWHM) induced bubble dynamics at a silica-water interface were investigated. In particular, bubble dynamics far above the Threshold Radiant Exposure (TRE) for bubble formation were studied. At this, different silica surfaces (all of standard optical quality) were used, at which particular TREs were measured. Irradiation parameters like pulse duration or beam diameter were kept constant. As reported recently, every silica surface provides different nucleation sites for bubble formation and thus shows a specific TRE. By means of a sensitive optical detection device bubble lifetimes at the interface were monitored as a function of radiant exposure. Measurements were performed with maximum radiant exposures of 330 mJ/mm² on four different silica surfaces. The TREs of the surfaces were preliminarily determined to lie between 38 mJ/mm² and 95 mJ/mm². Above 150 mJ/mm², bubble lifetimes were measured to be independent of the surface used and its particular TRE. An explanation for this behavior was found by fast flash photographs of the onset of bubble formation, revealing vanishing differences in the heterogeneous nucleation with increasing radiant exposure.

Objective: The selective damage of the retinal pigment epithelium (RPE) with repetitive microsecond(s) laser pulses is a new technique for the treatment of several retinal diseases. RPE can selectively be damaged by simultaneously sparing off the adjacent photoreceptor tissue. Objective of this study is to investigate whether optoacoustic (OA) transients occurring during irradiation might be used to control the invisible treatment effect. Setup: A train of frequency doubled Nd:YLF laser pulses (527 nm, 1.7microsecond(s) pulse length, 500Hz rep. rate) were applied via a laser slit lamp on porcine RPE samples. The acoustic transients were recorded with a broadband transducer. Results: At low radiant exposures (<100 mJ/cm²) we found a bipolar pressure transient due to thermo-elastic expansion of the RPE. The pressure waves from the individual pulses of one pulse train show nearly identical transients. The transients differ slightly from different sites on the sample. At higher radiant exposures (>150 mJ/cm²), the OA transients differ from pulse to pulse within a pulse train, which can be attributed to microbubble formation around the strong absorbing melanosomes inside the RPE cells. FFT spectra of the OA transients show slight differences in the frequency spectrum with the different radiant exposures.

A sensitive method for measuring the circular dichroism (CD) of living cells in visible-near IR region is developed. The changes in CD spectra from 250 to 780 nm of HeLa cell suspension after the first and second irradiation at 820 nm in dose 9 J/cm² are investigated. The CD spectrum of the intact cells is well structured and characterized by a positive signal in the UV (250-290 nm) and visible-near IR (500-780 nm) regions as well as by a negative signal in 300-450 nm region. Distinct maxima in the visible-near IR region are recorded at 566, 634, 680, 712, and 741 nm. As a rule, the peak circular dichroism signals decrease in the irradiated cells except of the area 750-770 nm. Peak positions (exception: the peak at 680 nm) shift as a rule to the long-wavelength direction. The most remarkable changes in peak positions as well as in CD signals are recorded in the region 750-770 nm: an appearance of the new peak at 767 nm after the first irradiation and its shift to 752 nm after the second irradiation. The peaks at 712 and 741 nm disappear after the irradiation. A new peak appears at 601 nm. It is assumed that the changes in the degree of oxidation of the chromophores of cytochrome c oxidase caused by the irradiation are accompanied by conformational changes in their vicinity. It can be suggested that these changes are occurring in Cu_B environment.

The effects of laser exposure on mineralized tissues like enamel have been explored for years as a technique to remove caries and for dental hard-tissue preparation. However the efficiency of this technique has been questioned. In this work, six freshly-extracted third molars were irradiated by a superpulse of CO₂ laser, generally used in Transmyocardio Revascularization, and submitted to Scanning Electron Microscopy (SEM) analyzes. The cavities caused by laser irradiation on the dental tissues were analyzed considering its shape and depth. The CO₂ superpulse presented a high efficiency in the removal of dental mass and no sign of carbonized tissue was found on the ablated surface. All cavities generated by laser irradiation presented a conic shape with average depth depending on energy density applied.

In the past years, lasers have become a special tool in dentistry. To study the effects of laser apicoectomy compared to the conventional surgical treatment, freshly-extracted single-root teeth were used, submitted to traditional endodontic treatment and divided into four groups: Group I, conventional apicoectomy using diamond burs; Group II, the same treatment as Group I, however, with a 15 second orthophosphoric acid application; Group III Er:YAG laser cut (10 Hz - 400 mJ); and finally, Group IV Er:YAG laser cut (10 Hz - 400 mJ) and surface treatment with Nd:YAG laser (10 Hz - 2 W). The samples were submitted to 2,5 % blue methylene dye solution, at 25 degree(s)C and 37 degree(s)C for 36 h and 18 h, respectively, and analyzed under optical microscope. The results show that Group II had the higher permeability of all the groups and Group IV had the lower one, due to the successful Nd:YAG laser surface treatment.

A novel detection method for malignant tumour detection through specific accumulation of far-red emitting photosensitisers, has been developed. The set-up, based on He-Ne (633 nm) excitation was tested with phantom malignancies models using photosensitisers on chicken tissue. Intensity vs. depth of tissue measurements as well as photobleaching measurements were performed. Point by point fluorescence imaging indicated that the formation size is not significantly distorted with respect to depth of location.

The results of application of photodynamic diagnostics (PDD) and photodynamic therapy (PDT) for diagnosis and treatment of premalignant lesions and malignant tumours of different tissues were presented. In the period 1998-2000 a total of 314 patients were diagnosed with use of different methods of PDD and a total of 78 patients were treated with use of PDD. On the basis of obtained result we consider PDD and PDT to be sensitive, efficient and non-invasive methods of diagnostics and therapy of malignant lesions.

In the recent years (delta) -aminolevulinic acid ((delta) -ALA) a precursor for the endogenous production of protoporphyrin IX (PPIX) has gained importance in the Photodynamic Therapy (PDT) of superficial and early-stage cancers. Though (delta) -ALA is present naturally in the cells, systemic administration of exogenous (delta) -ALA leads to the production of intracellular endogenous PP IX in both the tumor and the normal cells, but with varying concentration. However, the PPIX is accumulated more in the tumor tissues as the fast growing tumor cells take up the administered (delta) -ALA more than the normal cells. As the therapeutic efficacy of PDT is dependent on the post (delta) -ALA incubation time, at which the tumor to normal ratio of the PPIX concentration is high, the concentration of the PPIX in the normal and the tumor site were estimated using fluorescence spectroscopy. However, the estimation of the PPIX concentration during/after PDT is mandatory, as the PDT dosimetry is dependent on the sensitizer concentration at the target of interest. The observed variation in the concentration of PPIX in the tumor site with respect to the unexposed normal surrounding tissues, may be attributed to the diffusion of PPIX from the surrounding normal tissues to the tumor site, across the concentration gradient. Based on this a mathematical model has been proposed, to estimate the rate parameter for the diffusion of PPIX from the surrounding normal tissues in to the tumor tissue (K_m), due to photobleaching during PDT at two different fluence. The K_m value at two different fluences, 57.6 and 36 J/cm2 are estimated as 5.444+/- 1.186 and 3.221+/- 0.957, respectively. Further, the rate parameter for the cleavage and efflux of (delta) -ALA (K₁), and the rate parameter for the evasion of the PPIX from the tumor tissues during PDT (K_t), were also estimated by fitting the experimental data to the developed mathematical model. The estimated parameters will be utilized to estimate the exact concentration of PPIX in the tumor tissues for a better PDT efficacy.

In this paper a novel diode laser system for photodynamic therapy is demonstrated. The system is based on linear spatial filtering and optical phase conjugate feedback from a photorefractive BaTiO₃ crystal. The spatial coherence properties of the diode laser are significantly improved. The system provides an almost diffraction limited output which is efficiently coupled into a 50 micrometers core diameter fiber. The optical power transmitted through the fiber is increased by a factor of six when the feedback is applied to the diode laser. 85 percent of the power from the freely running laser diode is extracted in a high-quality beam and 80 percent of the output power is extracted through the fiber. The power transmitted through the fiber scales linearly with the power of the laser diode, which means that a laser diode emitting 1.7 W multi-mode radiation would provide 1 W of optical power through a 50 micrometers core diameter fiber. The system is compact, portable, stable, and easy to operate.

The effectiveness of photodynamic therapy (PDT) as an adjuvant treatment for diverse malignant tumors has been investigated in numerous studies. The therapeutic success and extent of side effects of PDT is mainly determined by the applied photosensitizer (PS) and laser energy. Adjuvant intraoperative photodynamic therapy (AIOPDT) using the PS mTHPC (meso-Tetrahydroxyphenylchlorin) causes selective tumor cell death when combined with laser irradiation of a PS specific wavelength (652 nm). Our study proved AIOPDT as an efficient modality to significantly increase postoperative recurrence-free survival after R1/R2 resection of a subcutaneously implanted soft tissue sarcoma in mice. We used mTHPC in a dose of (0,3 mg/kg BW) and a laser light energy of 5 Joule (irradiation time: 50 seconds). First results showed an increase of postoperative recurrence-free survival (Median: 103 days) in 5 animals treated with AIOPDT compared to a control group of 7 animals (Median: 20 days). The tissue specific accumulation of mTHPC was determined by point spectrofluorometry and showed a 2.28 higher PS-accumulation in the tumor center, tumor bed (1.5) and overlying skin (3.8) compared to muscle tissue (1.0) as reference parameter. Our first experimental data recommend AIOPDT to be an efficient adjuvant method to prolonge recurrence-free survival after tumor resection.

The present study evaluates the impact of the fluence rate of red light irradiation ((lambda) = 650 nm) on photodynamic efficacy in mTHPC-sensitized HT29 and Colo26 spheroids. Photocytotoxicity, computed as product of the cell yield and plating efficiency, increased progressively when the fluence rate was reduced from 90 to 30 mW cm^-2 in both types of spheroids. The observed photocytotoxicity was mainly due to an immediate rather than a delayed cell death for HT29 spheroids. An opposite effect was observed for Colo26 spheroids. The plausible explanations could be the difference in penetration of mTHPC into the spheroids as well as their heterogeneous structure.

Efficacy of PDT with new chlorin e6 photosensitizer (BLC 1010) has been tested in 72 cancer patients. 44 patients (61 %) achieved a complete response and 39 % of the patients a partial response (28 patients, including 15 patients treated for palliation). Rapid elimination of BLC 1010 from the organism solves the problem of skin phototoxicity encountered in PDT up to now. This property together with its high tumor to normal ratio makes it a promising photosensitizer for PDT. Further advantage is that portable diode lasers with proper wavelength are available.

The antidiabetics tolbutamide, glibenclamide, and glipizide, and the diuretics bendroflumethiazide, butizide, furosemide, hydrochlorothiazide, and trichlormethiazide were investigated for potential phototoxicity in the HaCaT cell line. The cells were incubated with the drugs and then exposed to UVA1 irradiation. The effects of the antioxidants L-ascorbic acid, and (alpha) -tocopherol on oxidative DNA damage were assessed. Bendroflumethiazide, furosemide, hydrochlorothiazide, trichlormethiazide, or tolbutamide induced dose-dependent phototoxicity. Cells incubated with bendroflumethiazide, tolbutamide, and glibenclamide, and irradiated with UVA1 demonstrated an increased oxidative DNA damage. Pre-treatment with L-ascorbic acid, or (alpha) -tocopherol, suppressed the UVA-induced DNA damage in cells incubated with 1 mM of bendroflumethiazide, furosemide, glibenclamide, glipizide, tolbutamide, and trichloromethiazide, further implying the involvement of reactive oxygen species in the phototoxic DNA damage. These results may indicate a link between phototoxic and photocancerogenic potential of the sulfonamide-derived oral antidiabetic and diuretic drugs, as it has previously been recognized for psoralen, chlorpromazine, and fluoroquinolones. Excessive exposure to UV light may be deleterious for patients treated with these drugs.

The work is devoted to an analysis of pre-clinical and clinical experiments on photodynamic action of HeNe laser radiation in aggregate with a cation thiazinium dye Methylene Blue (MB) on a mix of pathogenic and conditionally pathogenic aerobic bacteria being activators of pyoinflammatory diseases of oral cavity. Concentration of photosensitizes at which there is no own bactericidal influence on dying microflora, and parameters of influence at which the efficiency of irradiated microflora defeat reaches 99 % are determined.

At present, foolproof methods are needed for control of low-power light biomedical effects. Transmission spectra of whole blood from 108 patients were recorded before and after action of low-intensity He-Ne laser and extracorporal UV irradiation. We have observed changes in the blood transmission spectrum caused by oxygen saturation changes in venous blood. It has shown that He-Ne laser irradiation more selectively acts to venous blood than extracorporal UV irradiation.

Laser-induced interstitial thermotherapy was performed in 29 patients with recurrent nodular and multinodular goiter, and in 3 patients with recurrent inoperable thyroid cancer. There were used transcutaneous puncture under ultrasonic control, diode lasers with wavelength 805, 980, and 1060 nm, quartz monofibers, special computerized thermometer with microthermocouples. Disappearance or significant reduction of nodes in the most goiter cases, and regress of tumor in the cancer cases were marked during observation period (0.5 - 2.5 years).

Laser osteoperforation, previously studied in experiment in rabbits at treatment for acute purulent osteomyelitis (Privalov V. et.al., SPIE Proc., v.3565., pp. 72-79), was applied in clinic to 36 patients with chronic purulent osteomyelitis and to 6 patients (children) with acute haematogenic osteomyelitis. Diode lasers of 805 and 980 nm wavelength were used. There was achieved full recovery in all acute cases, and stable remission in chronic cases during all the observation period (1 - 2.5 years).

The B ²(Sigma) ⁺->X²(Sigma) ⁺ violet band emission spectrum of CN following laser ablation of type I collagen was exploited for the estimation of the transient temperature of the plasma plume and consequently of the sample surface considering thermodynamic equilibrium. The temperature dependence upon experimental parameters, such as laser intensity and wavelength as well as delay of gated detection was obtained. The temperature was found to increase with increasing laser intensity and decrease with increasing gated time delay and laser wavelength.

Fifteen human embedded third molars were used in this in vitro study to evaluate the effects of two bleaching products associated or not with Argon laser application. The samples received a cervical-apical cut and were longitudinally cut into 4 parts resulting in 75 specimens. These parts were divided at random into 5 groups and submitted to the traditional power bleaching procedure for enamel. Group 1 was separated as a control group. Group 2 was exposed to 37 % carbamide peroxide bleaching solution and developed with an Argon laser application. The same solution was used in Group 3 but the bleaching was developed with an halogen lamp irradiation. 35 % carbamide peroxide were used in Groups 4 and 5. One was developed as Group 2 and the other as Group 3. The samples were analyzed under a photoreflectance experiment. We observed that Group 2 presented more white spectra than Group 3. However, Groups 4 and 5 showed the same results independent of the use of the laser or the halogen lamp for the light curing. Comparing both bleaching products, the 35 % carbamide peroxide was more efficient on its purposes than the other one.