scholarly journals A FOTOPOLIMERIZAÇÃO DE COMPÓSITOS ODONTOLÓGICOS ALÉM DA POTÊNCIA LUMINOSA

2020 ◽  
Author(s):  
Thales Ribeiro de Magalhães Filho
Keyword(s):  
Great Power ◽  
Dental Composites ◽  
Angle Of Incidence ◽  
Scientific Evaluation ◽  
Light Power ◽  
Regular Distribution ◽  
Light Rays ◽  
Light Curing ◽  
The Difference ◽  
Regular Mode

O objetivo deste estudo foi mostrar que a potência da luz das unidades de fotopolimerização (LED) não é a única ou a propriedade mais importante para uma polimerização satisfatória de compósitos dentários. A distribuição regular e o ângulo de incidência dos raios de luz também são igualmente responsáveis por uma polimerização mais completa e profunda. Esta revisão de literatura mostra que avançamos o suficiente na potência da luz emitida pelos LEDs, mas no que diz respeito à regularidade e ângulo dos raios emitidos, ainda temos muito a avançar. Novos compósitos com cargas reflexivas e preocupações com a diferença de índice de refração entre as cargas e a matriz são importantes para melhorar essa polimerização, mas os LEDs com vários comprimentos de onda podem complicar ainda mais a distribuição regular dos raios de luz emitidos. Dispositivos com diferentes LEDs emitindo raios de luz com diferentes comprimentos de onda não distribuem essas ondas no modo regular. Portanto, parte da restauração pode estar sub polimerizada, tornando-se menos resistente aos esforços mastigatórios e à infiltração. O estudo também relembra propostas de avaliação científica dessa distribuição regular e conclui que os LEDs modernos emitem raios de luz com grande potência e irradiância, mas ainda são irregulares na distribuição dos raios de luz emitidos.Palavras-chave: fotopolimerização, conprimento de onda, irradiância, resina composta.PHOTOPOLIMERIZATION OF DENTAL COMPOSITES BEYOND THE LIGHT POWER EMITED BY LED LIGHT CURING UNITSABSTRACT:            The objective of this study was to show that light power of light curing units (LCU) is not the only or the most important property for a satisfactory polymerization of dental composites. Regular distribution and angle of incidence of the light rays are also equally responsible for a fuller and deeper polymerization. This literature review shows that we advanced enough in the power of light emitted by LCUs, but as regards the regularity and angle of the emitted rays, we still have much to advance. New composites with reflective fillers and concerns about the difference of refractive index between the fillers and the matrixare important help to improve this polymerization, but LCUs with several wavelengths can further complicate the regular distribution of emitted light rays. Devices with different LEDs emitting light rays with different wavelengths does not distribute these waves in a regular mode. Therefore, part of the restoration can be under polymerized, becoming less resistant to masticatory efforts and infiltration as well. The study also recalls proposals for scientific evaluation of this regular distribution and concludes that modern LCUs emit light rays with great power and irradiance, but are still irregular in the distribution of emitted light rays.Keywords: photopolymerization, wavelength, Irradiance, composite.

scholarly journals The Photoinitiators Used in Resin Based Dental Composite—A Review and Future Perspectives

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 470
Author(s):  
Andrea Kowalska ◽  
Jerzy Sokolowski ◽  
Kinga Bociong
Keyword(s):  
Current Knowledge ◽  
Biomechanical Properties ◽  
Degree Of Conversion ◽  
Dental Composite ◽  
Polymerization Process ◽  
Dental Composites ◽  
Dental Resin ◽  
Dental Resins ◽  
Light Curing

The presented paper concerns current knowledge of commercial and alternative photoinitiator systems used in dentistry. It discusses alternative and commercial photoinitiators and focuses on mechanisms of polymerization process, in vitro measurement methods and factors influencing the degree of conversion and hardness of dental resins. PubMed, Academia.edu, Google Scholar, Elsevier, ResearchGate and Mendeley, analysis from 1985 to 2020 were searched electronically with appropriate keywords. Over 60 articles were chosen based on relevance to this review. Dental light-cured composites are the most common filling used in dentistry, but every photoinitiator system requires proper light-curing system with suitable spectrum of light. Alternation of photoinitiator might cause changing the values of biomechanical properties such as: degree of conversion, hardness, biocompatibility. This review contains comparison of biomechanical properties of dental composites including different photosensitizers among other: camphorquinone, phenanthrenequinone, benzophenone and 1-phenyl-1,2 propanedione, trimethylbenzoyl-diphenylphosphine oxide, benzoyl peroxide. The major aim of this article was to point out alternative photoinitiators which would compensate the disadvantages of camphorquinone such as: yellow staining or poor biocompatibility and also would have mechanical properties as satisfactory as camphorquinone. Research showed there is not an adequate photoinitiator which can be as sufficient as camphorquinone (CQ), but alternative photosensitizers like: benzoyl germanium or novel acylphosphine oxide photoinitiators used synergistically with CQ are able to improve aesthetic properties and degree of conversion of dental resin.

45° REFLECTOMETRY OF SEMICONDUCTOR QUANTUM WELLS

2001 ◽  
Vol 15 (17n19) ◽  
pp. 683-687
Author(s):  
A. SILVA-CASTILLO ◽  
F. PEREZ-RODRIGUEZ
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Growth Direction ◽  
Angle Of Incidence ◽  
Near Surface ◽  
New Information ◽  
Difference Formula ◽  
Exciton Polaritons ◽  
The Difference ◽  
First Time

We have applied the 45° reflectometry for the first time to study exciton-polaritons in quantum wells. The 45° reflectometry is a new polarization-modulation technique, which is based on the measurement of the difference [Formula: see text] between the p-polarization reflectivity (Rp) and the squared s-polarization reflectivity [Formula: see text] at an angle of incidence of 45°. We show that [Formula: see text] spectra may provide qualitatively new information on the exciton-polariton modes in a quantum well. These optical spectra turn out to be very sensitive to the zeros of the dielectric function along the quantum-well growth direction and, therefore, allow to identify the resonances associated with the Z exciton-polariton mode. We demonstrate that 45° reflectometry could be a powerful tool for studying Z exciton-polariton modes in near-surface quantum wells, which are difficult to observe in simple spectra of reflectivity Rp

Ultra-fast light curing dental composites with minimal monomer elution

2013 ◽  
Vol 29 ◽  
pp. e95
Author(s):  
L. Randolph ◽  
G. Leloup ◽  
W.M. Palin ◽  
J.G. Leprince
Keyword(s):  
Dental Composites ◽  
Light Curing ◽  
Fast Light

Aerodynamic Data for Two Variants of Root Turbine Blade Sections for a 54″ Turbine Rotor Blade

2014 ◽  
Author(s):  
David Šimurda ◽  
Martin Luxa ◽  
Pavel Šafařík ◽  
Jaroslav Synáč ◽  
Bartoloměj Rudas
Keyword(s):  
Limit Load ◽  
Axial Direction ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Angle Of Incidence ◽  
Flow Angle ◽  
Turbine Rotor Blade ◽  
Blade Cascade ◽  
The Difference ◽  
Kinetic Energy Loss

Aerodynamic investigations were performed on planar blade cascades representing two alternative root sections of rotor blades 54″ in length with straight fir-tree root. Each of the variants was designed for different number of blades in the rotor. This paper presents the results of measurements showing the dependency of the kinetic energy loss coefficient and the exit flow angle on the exit isoentropic Mach number and the angle of incidence. Images of the flow fields are also presented. The experimental data is analyzed to assess and document the difference between the two root section designs. Results show that requirement of straight fir tree root leading to high design incidence angles significantly limit operation range. Also in case of root sections with high exit Mach numbers a limit load conditions are an issue. In order to utilize available pressure drop blade cascade throat/pitch ratios should be kept as high as possible which favorites variant with lower number of blades and higher outlet metal angle (relative to axial direction).

Orientational Movements of the Foot of Littorina Species in Relation to the Plane of Vibration of Polarized Light

1961 ◽  
Vol 38 (1) ◽  
pp. 213-224
Author(s):  
G. H. CHARLES
Keyword(s):  
Polarized Light ◽  
Angle Of Incidence ◽  
Virtual Absence ◽  
Lens Aperture ◽  
Light Rays ◽  
Stimulation Of

1. Littorina littoralis (L.), L. saxatilis (L.), L. neritoides (L.) and L. littorea (L.) responded to the plane of vibration (e vector) of polarized light directly incident upon their eyes in the virtual absence of any substrate reflexions. Photonegative winkles orientated parallel with the plane of vibration and photopositive individuals at right angles to this plane. 2. Decrease of the angle of incidence towards zero of polarized light rays incident upon the lens aperture of Littorina littoralis completely destroyed the ability to orientate to the plane of vibration. This can be explained on the basis of a Fresnel reflexion/refraction mechanism of orientation. 3. Unilaterally blinded Littorina littoralis gave just as good an orientation to vertical rays of polarized light as winkles with intact vision. 4. It is concluded that the eyes of Littorina species are capable of detecting the plane of vibration of polarized light directly incident from above by means of a Fresnel reflexion/refraction mechanism, and that orientation does not depend on balanced stimulation of the two eyes.

Degree of conversion and microhardness of bulk-fill dental composites polymerized by LED and QTH light curing units

2020 ◽  
Vol 62 (1) ◽  
pp. 107-113
Author(s):  
Maryam Pirmoradian ◽  
Tabassom Hooshmand ◽  
Siavash Jafari-Semnani ◽  
Foroogh Fadavi
Keyword(s):  
Degree Of Conversion ◽  
Dental Composites ◽  
Light Curing ◽  
Qth Light

Flow past finite cylinders of constant curvature

2018 ◽  
Vol 837 ◽  
pp. 896-915 ◽  
Author(s):  
Jessica K. Shang ◽  
H. A. Stone ◽  
A. J. Smits
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Vortex Shedding ◽  
Angle Of Incidence ◽  
Number Range ◽  
Independence Principle ◽  
Laminar Wake ◽  
The Difference ◽  
Visualization Experiments ◽  
Local Angle

Wake visualization experiments were conducted on a finite curved cylinder whose plane of curvature is aligned with the free stream. The stagnation face of the cylinder is oriented concave or convex to the flow at $230\leqslant Re_{D}\leqslant 916$, where $Re_{D}$ is the cylinder Reynolds number and the curvature is constant and ranges from a straight cylinder to a quarter-ring. While the magnitude of the local angle of incidence to the flow is the same for both orientations, the contrast in their wakes demonstrates a violation of a common approximation known as the ‘independence principle’ for curved cylinders. Vortex shedding always occurred for the convex-oriented cylinder for the Reynolds-number range investigated, along most of the cylinder span, at a constant vortex shedding angle. In contrast, a concave-oriented cylinder could exhibit multiple concurrent wake regimes along its span: two shedding regimes (oblique, normal) and two non-shedding regimes. The occurrence of these wake regimes depended on the curvature, aspect ratio and Reynolds number. In some cases, vortex shedding was entirely suppressed, particularly at higher curvatures. In the laminar wake regime, increasing the curvature or decreasing the aspect ratio restricts vortex shedding to smaller regions along the span of the cylinder. Furthermore, the local angle of incidence where vortex shedding occurs is self-similar across cylinders of the same aspect ratio and varying curvature. After the wake transitions to turbulence, the vortex shedding extends along most of the cylinder span. The difference in the wakes between the concave and convex orientations is attributed to the spanwise flow induced by the finite end conditions, which reduces the generation of spanwise vorticity and increases the incidence of non-shedding and obliquely shedding wakes for the concave cylinder.

The Research on the Universities Counselor’s Profession and Competence

2010 ◽  
Vol 171-172 ◽  
pp. 752-755
Author(s):  
Hong Chun Zhu ◽  
Zhi Gang Zhou
Keyword(s):  
Statistical Analysis ◽  
Career Development ◽  
Evaluation System ◽  
Sample Survey ◽  
Scientific Evaluation ◽  
The Difference ◽  
The Impact

In the investigation of the universities counselor’s contradiction and bepuzzlement in work and competence, this paper obtain the following results by sample survey of counselors and statistical analysis of profession and competence. Counselors own identity on their career will affect the counselor’s ability. The awareness of the importance of counselor’s ability is by the impact of different occupations. And the difference of this understanding in turn will affect the career development of counselors. The development law of the universities counselor’s profession and competence is explored. According to the analysis and the research, a scientific evaluation system for counselor’s ability is established, which is consistent with the needs of counselors, and is the key to building professionalism for the counselors.

Study of some Dental Biomaterials Properties Using an Original Software Application

2013 ◽  
Vol 587 ◽  
pp. 121-127 ◽  
Author(s):  
Vasile Prejmerean ◽  
Laura Silaghi-Dumitrescu ◽  
Doina Prodan ◽  
Cristina Prejmerean ◽  
Marioara Moldovan
Keyword(s):  
Digital Images ◽  
Dental Materials ◽  
Dental Composites ◽  
Software Application ◽  
Color Changes ◽  
Color System ◽  
The Difference ◽  
Aluminum Plates ◽  
Statistical Results ◽  
Cielab Color

The aim of the present study is to measure the optical properties of dental materials, color and translucency, as well as their radiopacity using digital images. To do this, an original software application implementing two functions has been developed. Determining the radiopacity amount of certain areas of the materials is achieved by interpolating the values of ten aluminum plates used as reference. The study of this property is achieved by interpreting the statistical results and graphs displayed. The translucency value was calculated as the difference of the CIELab color system values for two digital images representing the same material on white and black background, respectively. In order to evaluate the color changes of the biomaterials, the samples were immersed in coffee, wine and orange juice. The application has been tested on several experimental materials based on bioceramics, dental composites and giomers, and the results are similar to the ones obtained using other evaluation methods.

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