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Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 548
Author(s):  
Anca Mesaroș ◽  
Michaela Mesaroș ◽  
Smaranda Buduru

Background: Since fixed orthodontic treatment is widely spread and one of its inconveniences is bracket removal, as this affects enamel integrity as well as being a cause of discomfort to the patient, studies have searched for the most adequate bracket removal technique, many of them focusing on using laser-technology. Methods: Our review focused on articles published investigating methods of orthodontic bracket removal using laser technology in the last 30 years. Results: 19 relevant studies were taken into consideration after a thorough selection. Different types of laser devices, with specific settings and various testing conditions were tested and the investigators presented their pertinent conclusions. Conclusions: Most studies were performed using ceramic brackets and the best results in terms of prevention of enamel loss, temperature stability for the tooth as well as reduced chair time were obtained with Er:YAG lasers.


2022 ◽  
Author(s):  
Le Anh Duc ◽  
Pham Minh Hieu ◽  
Nguyen Minh Quang

Abstract The material yttrium aluminum oxide (Y3Al5O12) is one of the materials commonly used in laser devices. For application in optical devices, it is necessary to produce ultra-precise surface quality, however, Y3Al5O12 material belongs to the group of difficult-to-machine materials with high brittleness and hardness. Therefore, it is very difficult to ensure that the main criterion when finishing this material to produce a quality surface in the nanometer form with the ability to remove the material is very difficult. To solve this problem, this work provided a new chemical - mechanical polishing mixture. The proposed polishing mixture of ZrO2, Na2SiO3–5H2O, and MgO abrasives has a weight ratio of 8%, 5% and 1% respectively, with the remainder being deionized water. The surface result after polishing is obtained with a material removed rate of 38 (nm/min) along with an ultra-smooth surface produced with Ra = 0.41 nm. With the help of X-ray photoelectron spectroscopy (XPS) method before and after polishing by CMS, the reaction mechanisms were elucidated. Analytical results show that Y3Al5O12 material produces YOOH and AlOOH in Na2SiO3 solution, then combines with –Si–OH to form (Y-Si) and (Al-Si) with significantly reduced hardness compared to other Y3Al5O12 materials, these products combine with MgO to form montmorillonites (3MgO–Al2O3–3SiO2–3Y2O3–5Al2O3). With this formation, the surface layer of Y3Al5O12 material becomes soft and is easily removed by ZrO2 abrasive particles under the influence of mechanical polishing, resulting in superfine surfaces are generated from the proposed CMS model.


2022 ◽  
Vol 11 (1) ◽  
Author(s):  
Shuki Enomoto ◽  
Tomoya Tagami ◽  
Yusuke Ueda ◽  
Yuta Moriyama ◽  
Kentaro Fujiwara ◽  
...  

AbstractLead-halide perovskites are highly promising for various optoelectronic applications, including laser devices. However, fundamental photophysics explaining the coherent-light emission from this material system is so intricate and often the subject of debate. Here, we systematically investigate photoluminescence properties of all-inorganic perovskite microcavity at room temperature and discuss the excited state and the light–matter coupling regime depending on excitation density. Angle-resolved photoluminescence clearly exhibits that the microcavity system shows a transition from weak coupling regime to strong coupling regime, revealing the increase in correlated electron–hole pairs. With pumping fluence above the threshold, the photoluminescence signal shows a lasing behavior with bosonic condensation characteristics, accompanied by long-range phase coherence. The excitation density required for the lasing behavior, however, is found to exceed the Mott density, excluding the exciton as the excited state. These results demonstrate that the polaritonic Bardeen–Cooper–Schrieffer state originates the strong coupling formation and the lasing behavior.


Author(s):  
Lea Kraft ◽  
Ralf Petzold ◽  
Rodrigo Suarez-Ibarrola ◽  
Arkadiusz Miernik

Abstract The aim of this work was to compare the fragmentation efficiency of a novel, pulsed Thulium solid-state laser (p-Tm:YAG) to that of a chopped Thulium fibre laser (TFL) and a pulsed Holmium solid-state laser (Ho:YAG). During the fragmentation process, we used a silicone mould to fixate the hemispherical stone models under water in a jar filled with room-temperature water. Each laser device registered the total energy applied to the stone model to determine fragmentation efficiency. Our study examined laser settings with single pulse energies ranging from 0.6 to 6 J and pulse frequencies ranging from 5 to 15 Hz. Similar laser settings were applied to explicitly compare the fragmentation efficiency of all three devices. We experimented with additional laser settings to see which of the three devices would perform best. The fragmentation performance of the three laser devices differed statistically significantly (p < 0.05). The average total energy required to fragment the stone model was 345.96 J for Ho:YAG, 372.43 J for p-Tm:YAG and 483.90 J for TFL. To fragment the stone models, both Ho:YAG and p-Tm:YAG needed similar total energy (p = 0.97). TFL’s fragmentation efficiency is significantly lower than that of Ho:YAG and p-Tm:YAG. Furthermore, we found the novel p-Tm:YAG’s fragmentation efficiency to closely resemble that of Ho:YAG. The fragmentation efficiency is thought to be influenced by the pulse duration. TFL’s shortest possible pulse duration was considerably longer than that of Ho:YAG and p-Tm:YAG, resulting in Ho:YAG and p-Tm:YAG exhibiting better fragmenting efficiency.


2021 ◽  
Vol 11 (22) ◽  
pp. 10539
Author(s):  
Aleksandr Tarasov ◽  
Hong Chu

This review describes new engineering solutions for Ti:Sapphire lasers obtained at Laseroptek during the development of laser devices for dermatology and aesthetic medicine. The first device, PALLAS, produces 311 nm radiation by the third harmonic generation of a Ti:Sapphire laser, which possesses similar characteristics to excimer laser-based medical devices for skin treatments. In comparison to excimer lasers, Ti:Sapphire laser services are less expensive, which can save ~10% per year for customers compared to initial excimer laser costs. Here, the required characteristics were obtained due to the application of a new type of diffraction grating for spectral selection. The second device, HELIOS-4, based on the Ti:Sapphire laser, produces 300 mJ, 0.5 ns pulses at 785 nm for tattoo removal. The characteristics of HELIOS-4 exceed those of other tattoo removal laser devices represented in the medical market, despite a simple and inexpensive technical solution. The development of the last laser required the detailed study of a generation process and the investigation of the factors responsible for the synchronization of the generation in Ti: Sapphire lasers with short (several millimeters) cavities. The mechanism that can explain the synchronization in such lasers is suggested. Experiments for the confirmation of this concept are conducted and analyzed.


2021 ◽  
Vol 906 (1) ◽  
pp. 012054
Author(s):  
Irina Galchenko ◽  
Janusz Kozubal ◽  
Zbigniew Muszyński ◽  
Rasaq Lawal ◽  
Marek Wyjadlowski ◽  
...  

Abstract The description of the surface topography of building structures is important for contact tasks, bond strength and rheological processes monitoring. The determination of surface parameters is carried out using increasingly sophisticated methods and techniques, such as laser profilometer, laser scanner, confocal microscope or short range photogrammetry. The research is aimed at evaluating the mobile surface test device for quality control and failure prevention, also the authors have addressed the possibility of using inexpensive profile measuring laser equipment to obtain a geostatistical description of the surface parametrics. It is the support of creation of new measurement apparatus that is the impetus for this work for the selection of optimal laser device. It is possible to deduce from the paper how the density of measurements taken and the accuracy of height estimation in the profile affect the parameters of the semivariogram model. With the proper choice of device it is easier correctly estimate the strength parameters of the joint of concrete or soil-concrete structures. The relevance of the correctly performed measurement is proved by the link between the strength parameters of the contact surfaces and its geostatistical description. In order to assess the quality of the mapping, a spherical theoretical model with a corresponding generated surface was used as a reference. The measuring laser devices with various mapping accuracy and depth measurement precision were tested, also for description fractal dimension of results. The measurement accuracy of the depth parameter has the greatest influence for determination of the remaining parameters of the surface roughness.


2021 ◽  
Vol 2075 (1) ◽  
pp. 012015
Author(s):  
Abdullah Taha Ali ◽  
W. Maryam ◽  
Yu-Wei Huang ◽  
H.C. Hsu ◽  
Naser M. Ahmed ◽  
...  

Abstract The random laser was investigated in gold-doped Zinc Oxide nanorods (Au-doped ZnO NRs) under a range of pumping power 0.25 - 4.66 mW. The Au-doped ZnO NRs prepared by chemical bath deposition (CBD) on the ZnO seed layer, were pre-coated on glass substrate using radio frequency magnetron sputtering (Rf-sputtering). The morphological of Au-doped ZnO NRs shows a hexagonal and strong vertically alignment against the substrate. The Energy dispersive spectroscopy (EDX) spectrum and elemental mapping results confirmed that Au atoms (at.%) are doped and spread over the ZnO NRs. More interestingly, the random laser of Au-doped ZnO shows a redshift of ~38 nm. This study showed the ability of using doping as a tuning parameter in the random laser, also provided an emphasis on Au-doped ZnO NRs as suitable options for controllable random laser devices.


2021 ◽  
Vol 6 (3) ◽  
pp. 134-142
Author(s):  
Uppalapati Vishwaja ◽  
Sindhuja Panthangi ◽  
Chavva Lakshmi Charan Reddy ◽  
Mattapudi Basavaiah Babu ◽  
Srivalli Podili

A novel SWEEPS® Er:YAG laser modality was recently introduced with the purpose of improving the disinfecting and activating efficacy of SSP laser assisted endodontic procedures by permitting the generation of primary and secondary shock waves throughout the complicated root canal system. The SWEEPS method greatly improves the efficacy of removing debris and medications from the root canal system. In the most current Er:YAG dental laser devices, the complimentary combination of SSP and SWEEPS® technology constitutes a distinct solution for modern endodontics. The aim of this review is to: (i) Offer the most relevant data on a novel SWEEPS (shock wave enhanced emission photoacoustic streaming) technology, its relative advantages, with an emphasis on single-pulse SSP laser-assisted irrigation and dual pulse SWEEPS technology; (ii) Provide recommendations for the use of SWEEPS technology in Endodontics based on current evidence; (iii) Highlight the areas in which more research is required.


Author(s):  
Mehmet Yilmaz ◽  
Julia Esser ◽  
Lea Kraft ◽  
Ralf Petzold ◽  
August Sigle ◽  
...  

Abstract Purpose The aim of this study was to compare the enucleation performances of four different types of laser devices in an ex-vivo experiment: a novel, pulsed Tm:YAG solid-state laser evaluation model (p-Tm:YAG), chopped thulium fibre laser (TFL), low-power Ho:YAG laser (LP-Ho:YAG), and a high-power Ho:YAG laser (HP-Ho:YAG). Methods Our primary aim was to endoscopically separate the fascial layers of a porcine belly using laser fibres within a time period of 60 s. The size of a “tissue pocket” was assessed numerically. The enucleation characteristics reflecting the surgeon’s experience were evaluated via the NASA Task Load Index (TLX) questionnaire and a questionnaire based on Likert scale. Results HP-Ho:YAG achieved with the available laser settings the largest overall “tissue pocket” (31.5 cm2) followed by p-Tm:YAG (15 cm2), TFL (12 cm2), and LP-Ho:YAG (6 cm2). The coagulation performances of p-Tm:YAG and TFL were rated the best. In the performance evaluation by the Likert questionnaire, HP-Ho:YAG (average score of 4.06) was rated highest, followed by p-Tm:YAG (3.94), TFL (3.38), and LP-Ho:YAG (3.25). The evaluation of the NASA-TLX performance questionnaire revealed average scores for HP-Ho:YAG, LP-Ho:YAG, TFL and p-Tm:YAG of 4.38, 4.09, 3.92 and 3.90, respectively. Conclusion We are the first to compare different laser devices and settings in an ex-vivo study. We found that the surgeons were most satisfied with the HP-Ho:YAG laser device, followed by the p-Tm:YAG. These findings could be highly relevant for future research and for the practical utilisation of laser systems in endourology.


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