New laser technology and future applications

Metal Material Processing Using Femtosecond Lasers: Theories, Principles, and Applications

Metal material processing using femtosecond lasers is a useful technique, and it has been widely employed in many applications including laser microfabrication, laser surgery, and micromachining. The basic mechanisms of metal processing using femtosecond lasers are reviewed in this paper and the characteristics and theory of laser processing are considered. In addition to well-known processes, the recent progress relating to metals processing with femtosecond lasers, including metal material drilling, metal ablation thresholds, micro/nano-surface modification, printed circuit board (PCB) micromachining, and liquid metal (LM) processing using femtosecond lasers, is described in detail. Meanwhile, the application of femtosecond laser technology in different fields is also briefly discussed. This review concludes by highlighting the current challenges and presenting a forward-looking perspective on the future of the metal laser processing field.

The Contribution of Cell Imaging to the Study of Anterior Pituitary Function and Its Regulation

Advances in the knowledge of the neuroendocrine system are closely related to the development of cellular imaging and labeling techniques. This synergy ranges from the staining techniques that allowed the first characterizations of the anterior pituitary gland, its relationship with the hypothalamus, and the birth of neuroendocrinology; through the development of fluorescence microscopy applications, specific labeling strategies, transgenic systems, and intracellular calcium sensors that enabled the study of processes and dynamics at the cellular and tissue level; until the advent of super-resolution microscopy, miniscopes, optogenetics, fiber photometry, and other imaging methods that allowed high spatiotemporal resolution and long-term three-dimensional cellular activity recordings in living systems in a conscious and freely moving condition. In this review, we briefly summarize the main contributions of cellular imaging techniques that have allowed relevant advances in the field of neuroendocrinology and paradigm shifts that have improved our understanding of the function of the hypothalamic-pituitary axes. The development of these methods and equipment is the result of the integration of knowledge achieved by the integration of several disciplines and effort to solve scientific questions and problems of high impact on health and society that this system entails.

High-Peak-Power Sub-Nanosecond Mode-Locking Pulses Generated by a Dual-Loss-Modulated QML Laser with AOM and SnSe2

In order to investigate the pulse modulation potential of SnSe2 in all-solid-state lasers, an active and passive dual-loss-modulated (APDM) Q-switched and mode-locking (QML) Nd:YVO4 laser was realized by employing an acousto-optic modulator (AOM) and a 5.9 nm thick SnSe2 saturable absorber (SA). The significant pulse compression ability of SnSe2 film was found experimentally, and sub-nanosecond mode-locking pulses with large peak power were obtained. The average output power, pulse energy, and pulse width versus the pump power were measured. With a pump power of 8.5 W, 242 ps mode-locking pulses with a pulse peak power of 231.4 kW were realized successfully. The experimental results also show that the SnSe2-based APDM QML laser has great potential in generating sub-nanosecond pulses with large peak power and high stability.

Evaluation of the Effect of Various Powers of the Diode Laser in Microcrack Formation in the Wall of the Dental Root Canal by Scanning Electron Microscope (SEM)

Background:

The laser is utilized for the removal of the smear layer, cleaning and disinfecting the dental canal. Recently, diode laser has been offered with a wavelength of (635-980nm) for cleaning and disinfecting the dental root canal.

Objective:

There is not adequate evidence for microcrack formation when using diode lasers with different powers. Therefore, the present study was conducted in order to analyze various powers of a diode laser in microcrack formation in dental root canals.

Methods:

In this experimental study, 100 mandibular incisor teeth that were extracted because of periodontal disease were selected. Using stereo-microscope, the presence of crack and fracture of the root was evaluated before and after canal instrumentation. Then, samples were randomly divided into 10 groups (10 samples in any group) based on different powers of laser and canal to be humid or dry under laser radiation. The laser was utilized for 10s puls within three iterated times. The samples were cross-sectioned after disinfection with a diode laser at 3 and 6mm length from the dental apex. Sections were observed under a scanning electron microscope and images were taken.

Results:

The frequency of microcracks is increased at the distance of (3-6mm) from the dental apex by an increase in laser power level from 2 to 4w (P<0.05). Similarly, results showed that the probability of microcrack formation under dry condition than the humid condition at the distance of 3mm from the dental apex might increase to 6.606 times and at the distance of 6mm from the dental apex increase to 4.978 times more.

Conclusion:

The optimal power of diode laser in the wavelength of (980nm) for cleaning and disinfecting of the root canal with the minimum damage on hard periodontium tissue is 1.5w.

A quantitative evaluation of the use of medical lasers in German hospitals

The laser has become an integral part of modern medicine, procedures based on this technique have found their way into a multitude of medical disciplines. There is, however, no data available on the detailed quantitative development of laser use in the medical sector. This fact gave rise to the idea of the present study, which analyzed the raw data of the quality report of German hospitals with respect to this subject. Over the 9 years of report, a steady increase in the cumulative number of cases was evident, although not all body regions in which the medical laser is used followed this trend. The CO₂ laser was found to be the most commonly applied laser, even though a large spectrum of different laser types is used. Based on the present study, the importance of the laser for medical purposes can be confirmed.

Antimicrobial Photodynamic Therapy Protocols on Streptococcus mutans with Different Combinations of Wavelengths and Photosensitizing Dyes

The aim of the study is to test the application of different laser wavelengths, with and without different photosensitizing dyes on different types of cultures. Laser irradiation was realized on Streptococcus mutans in both solid and liquid culture media in continuous mode at three different fluences (10, 20, and 30 J/cm2) with a red diode (650 nm) with toluidine blue dye, a blue-violet diode (405 nm) with curcumin dye, and a green diode (532 nm) with erythrosine dye. Without a photosensitizer, no growth inhibition was obtained with the red diode at any fluence value. Inhibition rates of 40.7% and 40.2% were obtained with the blue diode and green diode. The blue diode laser used with curcumin obtained results in terms of growth inhibition up to 99.26% at a fluence of 30 J/cm2. The red diode laser used with toluidine blue obtained results in terms of growth inhibition up to 100% at fluences of 20 and 30 J/cm2. The KTP (potassium-titanyl-phosphate) laser used with erythrosine was able to determine a complete growth inhibition (100%) at the different fluence values. The combination of a laser and its proper color may dramatically change the results in terms of bactericidal effect. It will be interesting to confirm these data by further in vivo studies.

Non-Ionizing Radiation in Swedish Health Care-Exposure and Safety Aspects

The main aim of the study was to identify and describe methods using non-ionizing radiation (NIR) such as electromagnetic fields (EMF) and optical radiation in Swedish health care. By examining anticipated exposure levels and by identifying possible health hazards we also aimed to recognize knowledge gaps in the field. NIR is mainly used in health care for diagnosis and therapy. Three applications were identified where acute effects cannot be ruled out: magnetic resonance imaging (MRI), transcranial magnetic stimulation (TMS) and electrosurgery. When using optical radiation, such as class 3 and 4 lasers for therapy or surgical procedures and ultra-violet light for therapy, acute effects such as unintentional burns, photo reactions, erythema and effects on the eyes need to be avoided. There is a need for more knowledge regarding long-term effects of MRI as well as on the combination of different NIR exposures. Based on literature and after consulting staff we conclude that the health care professionals' knowledge about the risks and safety measures should be improved and that there is a need for clear, evidence-based information from reliable sources, and it should be obvious to the user which source to address.

Effect of different wavelengths and dyes on Candida albicans: In vivo study using Galleria mellonella as an experimental model

BACKGROUND

Studies on photodynamic inactivation against microorganisms had a great development in recent years. The aim of this work was to test the application of different laser wavelengths with or without different photosensitizing dyes on Candida albicans cells in vitro and in photodynamic therapy protocols in vivo in larvae of Galleria mellonella.

METHODS

Laser application was realized on C. albicans cells suspended in saline solution or cultured on solid medium for the in vitro study, and in a model of G. mellonella candidal infection for the in vivo study. Three wavelengths (650, 405, and 532nm) were used in continuous mode with different values of applied fluences: 10, 20 and 30J/cm² for the in vitro study and 10J/cm² for the in vivo study, without and with photosensitizing dyes.

RESULTS

No growth inhibition was obtained on yeast cells in saline solution without photosensitizers. The maximum inhibition of growth (100%) was obtained with 405nm diode laser and curcumin at any used fluence. No growth inhibition was observed for yeast cells cultured on solid medium after laser application without dyes. An inhibition was observed after laser application when curcumin and erythrosine were added to the medium. The survival curves of G. mellonella larvae infected with C. albicans with or without the different dyes and after laser application showed a statistically significant difference (p<0.001) in comparison with the proper control groups.

CONCLUSIONS

These results show the efficacy of photodynamic inactivation exploiting a suitable combination of light and dyes against C. albicans and the potential of photodynamic therapy for the treatment of candidal infections.

Photodynamic Therapy in Dentistry

Photodynamic therapy (PDT), also known as photoradiation therapy, phototherapy, or photochemo-therapy, involves the use of a photoactive dye (photosensitizer) that is activated by exposure to light of a specific wavelength in the presence of oxygen. The transfer of energy from the activated photosensitizer to available oxygen results in the formation of toxic oxygen species, such as singlet oxygen and free radicals. These very reactive chemical species can damage proteins, lipids, nucleic acids, and other cellular components. Applications of PDT in dentistry are growing rapidly: the treatment of oral cancer, bacterial and fungal infection therapies, and the photodynamic diagnosis (PDD) of the malignant transformation of oral lesions. PDT has shown potential in the treatment of oral leukoplakia, oral lichen planus, and head and neck cancer. Photodynamic antimicrobial chemotherapy (PACT) has been efficacious in the treatment of bacterial, fungal, parasitic, and viral infections. The absence of genotoxic and mutagenic effects of PDT is an important factor for long-term safety during treatment. PDT also represents a novel therapeutic approach in the management of oral biofilms. Disruption of plaque structure has important consequences for homeostasis within the biofilm. Studies are now leading toward selective photosensitizers, since killing the entire flora leaves patients open to opportunistic infections. Dentists deal with oral infections on a regular basis. The oral cavity is especially suitable for PACT, because it is relatively accessible to illumination.

Image analysis and processing methods in verifying the correctness of performing low-invasive esthetic medical procedures

Background

Efficacy and safety of various treatments using fractional laser or radiofrequency depend, to a large extent, on precise movement of equipment head across the patient’s skin. In addition, they both depend on uniform distribution of emitted pulses throughout the treated skin area. The pulses should be closely adjacent but they should not overlap. Pulse overlapping results in amplification of irradiation dose and carries the danger of unwanted effects.

Methods

Images obtained in infrared mode (Flir SC5200 thermovision camera equipped with photon detector) were entered into Matlab environment. Thermal changes in the skin were forced by CO₂RE laser. Proposed image analysis and processing methods enable automatic recognition of CO₂RE laser sites of action, making possible to assess the correctness of performed cosmetic procedures.

Results

80 images were acquired and analyzed. Regions of interest (ROI) for the entire treatment field were determined automatically. In accordance with the proposed algorithm, laser-irradiated L_i areas (ROI) were determined for the treatment area. On this basis, error values were calculated and expressed as percentage of area not covered by any irradiation dose (δ_o) and as percentage area which received double dose (δ_z). The respective values for the analyzed images were δ_o=17.87±10.5% and δ_z=1.97±1.5%, respectively.

Conclusions

The presented method of verifying the correctness of performing low-invasive esthetic medical (cosmetic) procedures has proved itself numerous times in practice. Advantages of the method include: automatic determination of coverage error values δ_o and δ_z, non-invasive, sterile and remote-controlled thermovisual mode of measurements, and possibility of assessing dynamics of patient’s skin temperature changes.