Laserterapia de baixa intensidade no manejo da dor provocada por separadores elastoméricos: uma revisão integrativa

Introduction: The use of elastomeric separators during orthodontic treatment can cause pain and low-level laser therapy has been used to manage this outcome. Objective: To present the evidence on the effect of low-level laser therapy in the management of pain caused by the use of elastomeric separators. Methods: An integrative review of clinical studies was carried out in the PubMed, Web of Science, Scopus, BVS, SciELO and clinicaltrials.gov databases using a PICo strategy developed with descriptors, including studies published in the last ten years, without language restriction. 68 articles were tracked and 12 were reviewed. Literature review: Considering laser therapy, most studies used gallium and aluminum arsenide (Ga-Al-As), with a wavelength between 808nm and 940nm, as well as power between 40.6mW and 200mW. The visual analog scale (VAS) was used by most studies to measure the pain. Two studies did not find significant differences in low-level laser therapy in pain caused by elastomeric separators, eight studies found significant differences between the intervention, control and placebo groups (when used) and two studies were not fully conclusive and pointed out partial statistical differences between the groups in question. The application techniques were too heterogeneous in the studies included in this review and do not allow a quantitative synthesis. Conclusion: The low-level laser therapy can demonstrate beneficial effects in reducing pain caused by elastomeric separators. However, it is not yet possible to determine the best application technique.

The Effect of Photobiomodulation on Distraction Osteogenesis

Distraction osteogenesis (DO) is a surgical procedure to increase bone height in different body parts. DO includes a surgical incision, wherein the bone is cut and a device is installed for further separation of the two ends by gradual unscrewing of the device screw. New bone gradually forms and fills the gap, and the bone height increases as such. Photobiomodulation (PBM) or low-level laser therapy (LLLT) enhances the formation of soft and hard tissue such as bone and can, therefore, accelerate the process of DO and shorten the duration of different surgical phases of DO such as latency, activation, and consolidation. Different laser types with variable exposure settings and protocols have been used for this purpose. The gallium-aluminum-arsenide (GaAlAs) diode laser is the most commonly used laser type for LLLT. This study reviews 18 published articles on the effects of LLLT on DO and summarizes their findings to further elucidate this topic.

First principles calculations of Al AsxP1-x ternary nanocrystal alloying composition

III-V zinc-blende AlP, AlAs semiconductors and their alloy Aluminum Arsenide phosphide Al AsxP1-x ternary nanocrystals have been investigated using Ab- initio density functional theory (Ab-initio-DFT) at the generalized-gradient approximation (GGA) level with STO-3G basis set coupled with large unit cell method (LUC). The dimension of crystal is found around (1.56 – 2.24) nm at a function of increasing the sizes (8, 16, 54, 64) with different concentration of arsenide (x=0, 0.25, 0.5, 0.75 and 1) respectively. Gaussian 03 code program has been used throughout this study to calculate some of the physical properties such as the electronic properties energy gap, lattice constant, valence and conduction band as well as density of state. Results show that the lattice constant increases with the increasing in the arsenide concentration in the alloy. The total energy, cohesive energy, electron affinity and ionization potential as well as ionicity for these concentrations have been reported.

Оптические свойства InGaAs/InAlAs метаморфных наногетероструктур для фотопреобразователей лазерного и солнечного излучения

Reflectance spectroscopy has been used to determine the refractive indices of nanoscale In_ x Al_ y Ga_1– x – y As and In_ x Al_1– x As layers with indium and aluminum concentrations x = 0.21–0.24 and y = 0, 0.1, and 0.2 on specially created Bragg-reflector heterostructures at wavelengths in the range 700–2000 nm. It was demonstrated that the method based on an analysis of the auto- and cross-correlation coefficients of the wavelength derivatives of the dependence of the reflectance of structures of this kind in order to determine the dispersion curves of the materials forming a reflector. It was found that raising the concentration of indium in InGaAs and AlInAs leads to a substantial rise in the refractive index, with a preserved spectral run of the refractive indices, which is characteristic of gallium arsenide and aluminum arsenide.

Understanding band gaps of solids in generalized Kohn–Sham theory

The fundamental energy gap of a periodic solid distinguishes insulators from metals and characterizes low-energy single-electron excitations. However, the gap in the band structure of the exact multiplicative Kohn–Sham (KS) potential substantially underestimates the fundamental gap, a major limitation of KS density-functional theory. Here, we give a simple proof of a theorem: In generalized KS theory (GKS), the band gap of an extended system equals the fundamental gap for the approximate functional if the GKS potential operator is continuous and the density change is delocalized when an electron or hole is added. Our theorem explains how GKS band gaps from metageneralized gradient approximations (meta-GGAs) and hybrid functionals can be more realistic than those from GGAs or even from the exact KS potential. The theorem also follows from earlier work. The band edges in the GKS one-electron spectrum are also related to measurable energies. A linear chain of hydrogen molecules, solid aluminum arsenide, and solid argon provide numerical illustrations.