Measurement of shrinkage of composite resin by laser speckle contrast analysis

The aim of this study was to evaluate the shrinkage of a microhybrid dental composite resin photo-activated by one LED with different power densities by means of speckle technique. The dental composite resin Filtek (TM) Z-250 (3M/ESPE) at color A(2) was used for the samples preparation. Uncured composite was packed in a metallic mold and irradiated during 20 s from 100 to 1000 mW cm(-2). For the photo-activation of the samples, it was used a LED prototype (Light Emission Diode) with wavelength centered at 470 nm and adjustable power density until 1 W cm(-2). The speckle patterns obtained from the bottom composite surfaces were monitored using a CCD camera without lens. The speckle field is recorded in a digital picture and stored by CCD camera as the carrier of information on the displacement of the tested surface. The calculated values were obtained for each pair of adjacent patterns and the changes in speckle contrast as a function of time were obtained from six repeated measurements. The speckle contrasts obtained from the bottom surface with 100 mW cm(-1) were smaller than those than the other power densities. The higher power densities provided the higher shrinkage.

Low-Level Laser Therapy and Calcitonin in Bone Repair: Densitometric Analysis

The aim of this work was to evaluate the association of low-level laser therapy (LLLT, 830 nm) and calcitonin in bone repair considering that bone healing remains a challenge to health professionals. Calcitonin has antiosteoclastic action and LLLT is a treatment that uses low-level lasers or light-emitting diodes to alter cellular function. Both are used to improve bone healing. Densitometry is a clinical noninvasive valuable tool used to evaluate bone mineral density (BMD). Sixty male rats were submitted to bone defect with a trephine bur, randomly divided into four groups of 15 animals each: control (C); synthetic salmon calcitonin (Ca); LLLT (La); LLLT combined with calcitonin (LaCa). Animals from Ca and LaCa received 2UI/Kg synthetic salmon calcitonin intramuscularly on alternate days after surgery. Animals from groups La and LaCa were treated with infrared LLLT (830 nm, 10mW, 20 J/cm(2), 6 s, contact mode). Five animals from each group were euthanized 7, 14, and 21 days after surgery and bone defects were analyzed by densitometry. Statistical analysis showed a significant difference in BMD values in LaCa group at 7 and 21 days (P = 0, 005). The results of the densitometric study showed that LLLT (830 nm) combined with calcitonin improved bone repair.

The Effectiveness of Low-Intensity Red Laser for Activating a Bleaching Gel and Its Effect in Temperature of the Bleaching Gel and the Dental Pulp

Statement of the Problem: The effectiveness of low-intensity red laser for activating a bleaching gel and its effect in pulp temperature was not investigated in dental literature. Purpose: The objective of this study was to assess the effectiveness of low-intensity red laser for activating a bleaching gel, as well as its effect in temperature of the bleaching gel and the dental pulp. Materials and Methods: Forty extracted bovine teeth were immersed in a solution of coffee 14 days for darkening. The initial colors were recorded by spectrophotometric analysis. The specimens were randomly distributed into two groups (N = 20): the control, which did not receive light and the experimental group that received light from an appliance fitted with three red light-emitting laser diodes (? = 660 nm). A green-colored, 35% H2O2based bleaching gel was applied for 30 minutes, and changed three times. After bleaching, the colors were again measured to obtain the L*a*b* values. Color variation was calculated (?E) and the data submitted to the non-paired t-test (5%). To assess temperature, 10 human incisors were prepared, in which one thermocouple was placed on the bleaching gel applied on the surface of the teeth and another inside the pulp chamber. Results: There was a significant difference between the groups (p = 0.016), and the experimental group presented a significantly higher mean variation (7.21 +/- 2.76) in comparison with the control group (5.37 +/- 1.76). There was an increase in pulp temperature, but it was not sufficient to cause damage to the pulp. Conclusion: Bleaching gel activation with low-intensity red laser was capable of increasing the effectiveness of bleaching treatment and did not increase pulp temperature to levels deleterious to the pulp. CLINICAL SIGNIFICANCE The application of a low-intensity red laser was effective for activating a bleaching gel with green dye, without any deleterious increases in pulpal temperature. (J Esthet Restor Dent 24:126134, 2012)

Charge injection in an LED with a hybrid composite as the emissive layer

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis and Study of the Photophysical Properties of a New Eu3+ Complex with 3-Hydroxypicolinamide

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The influence of the region between residues 220 and 344 and beyond in Phrixotrix railroad worm luciferases green and red bioluminescence

To find the regions having a major influence on the bioluminescence spectra of railroad worm luciferases, we constructed new chimeric luciferases switching the fragments from residues 1-219 and from 220-545 between Phrixotrix viviani (PxvGR; λmax = 548 nm) green light-emitting luciferase and Phrixothrix hirtus (PxhRE; λmax = 623 nm) red light-emitting luciferases. The emission spectrum (λmax = 571 nm) and KM for luciferin in the chimera PxRE220GR (1-219, PxhRE; 220-545, PxvGR) suggested that the region above residue 220 of PxvGR had a major effect on the active site. However, switching the sequence between the residues 226-344 from PxvGR luciferase into PxhRE (PxREGRRE) luciferase resulted in red light emission (λmax = 603 nm), indicating that the region 220-344 by itself does not determine the emission spectrum. Furthermore, the sequence before residue 220 of the green-emitting luciferase is incompatible for light emission with the sequence above residue 220 of PxhRE. These results suggest that the fragments before and after residue 220, which correspond to distinct subdomains, may fold differently in the green- and red-emitting luciferases, affecting the active site conformation.

Photo-oxidation of polyphenylenevinylene chains in Langmuir-Blodgett and cast films

Poly(p-phenylene vinylene) (PPV) derivatives are well known for their applications in polymer light emitting diodes (PLEDs). These derivatives are highly susceptible to photooxidation though, which is mainly caused by the scission of the vinyl double bond on the polymer backbone. In this work, we show that Langmuir-Blodgett (LB) films are less degraded than cast films of a PPV derivative (OC1OC6-PPV). Both films had similar thickness (∼50 nm) to allow for a more realistic comparison. Photodegradation experiments were carried out by illuminating the films with white light from a halogen lamp (50W, 12 V), placed at a fixed dstance from the sample. The decay was monitored by UV-Vis and FTIR spectroscopies. The results showed that cast films are completely degraded in ca. 300 min, while LB took longer times, ca. 1000 min, i.e. 3 times the values for the cast films. The degradation process occurs in at least two stages, the rates of which were calculated assuming that the reaction follows a first order kinetics. The characteristic times for the first stage were 3.6×10-2 and 1.3×10-3 min-1 for cast and LB films, respectively. For the second stage the characteristic times were 5.6×10-2 and 5.0×10 -3 min-1. The differences can be attributed to the more compact morphology in the LB than in the cast films. With a compact morphology the diffusion of oxygen in the LB film is hampered and this causes a delay in the degradation process.

Background interference on the color of dental composite materials with different thickness by digital contrast

In this work the color dependence of resin composites with the background color was evaluated. The objective was to measure since what thickness the color of the sample stops being influenced by the color of the background over which the resin is placed and the methodology used in experiment was based in analyzing the contrast of digital images of the sample over a black background. The results shown that since 0.8 mm the images contrast becomes almost constant; it prove that since this thickness the color of resin composite depends on the optical resin properties only. The experiment was repeated under three conditions of luminosity to evaluate the influence of it on the image contrast and the results obtained were identical.

Bacterial cellulose from glucanacetobacter xylinus: Preparation, properties and applications

This chapter deals with the cellulose produced by the Glucanacetobacter xylinus strain, called bacterial cellulose, which is a remarkably versatile biomaterial usable in wide variety of domains, such as papermaking, optics, electronics, acoustics, and biomedical devices. Its unique structure shows entangled ultrafine fibers, which provide excellent mechanical strength, besides biodegradability, biocompatibility, high water-holding capacity, and high crystallinity. Some of its applications are described, such as complementary nutrition (. nata de coco), artificial temporary skin for wounds and burns, dental aid, artificial blood vessels and micronerve surgery, DNA separation, composite reinforcement, electronic paper, light emitting diodes, and fuel cell membranes. © 2007 Elsevier Ltd. All rights reserved.

The effects of exposure time on the surface microhardness of three dual-cured dental resin cements

This study evaluated the exposure time of light-curing of the polymers used for cementation on microhardness test in different storage times. The polymers (specifically called resin cements) were RelyX ARC, RelyX U100, and SET. Five specimens of each group were prepared and photo-polymerized with exposure times of 20 s and 180 s, using a LED polymerization unit with wavelength of 440 ~ 480 nm and light output was consistently 1,500 mW/cm2. The Vickers hardness test was performed in a MMT-3 Microhardness Tester. Data were submitted to ANOVA and Tukey's test (α = 0.05). The values of RelyX ARC showed statistically significant difference to groups with light exposure when considering only chemical cure (p < 0.05). The groups with light exposure (20 s and 180 s) showed no significant difference between them (p > 0.05). The RelyX U100 cured only chemically showed statistically significant difference between 48 h and 7 days (p < 0.05). The SET resin cement showed no significant difference to groups without light exposure for all storage times (p > 0.05). The values of hardening of the dual-cured resin cements improved after setting by light and chemical activation demonstrating the importance of light curing. © 2011 by the authors.

Composição de cores através da calibração radiométrica e fotométrica de LEDs: Teoria e experimento

In the present work, the basic concepts of radiometric, photometric and colorimetric calibration are presented, which were applied to three light-emitting diodes (LEDs) used to compose the different color sensations that the human eye perceives in the visible region of the electromagnetic spectrum. In this sense, an experimental setup comprising a LED drive circuit and a home-made integrating sphere was assembled for the initial radiometric and photometric calibration as well as to obtain a set of intensity and spectral combinations associated to different colorimetric CIE (Commission Internationale de l'Eclairage) coordinates. The reader can, therefore, understand, in a simple manner, the process of color composition inside a color monitor or display picture element (pixel ). © Sociedade Brasileira de Física.

Photodynamic antimicrobial therapy of curcumin in biofilms and carious dentine

Photodynamic therapy (PDT) is a technique that involves the activation of photosensitizers by light in the presence of oxygen, resulting in the production of reactive radicals that are capable of inducing cell death. The present study evaluated the susceptibility of Streptococcus mutans and Lactobacillus acidophilus to PDT grown as multi-species in the biofilm phase versus in dentine carious lesions. A brain-heart infusion culture medium supplemented with 1 % glucose, 2 % sucrose, and 1 % young primary culture of L. acidophilus 108 CFU/mL and S. mutans 108 CFU/mL was used to develop multi-species biofilms and to induce caries on human dentine slabs. Five different concentrations of curcumin (0.75, 1.5, 3.0, 4.0, and 5.0 g/L) were used associated with 5.7 J/cm2 light emission diode. Four different groups were analyzed L-D- (control group), L-D+ (drug group), L+D- (light group), and L+D+ (PDT group). ANOVA/Tukey's tests were conducted to compare groups. A significant reduction (p <0.05) in cell viability was observed in the biofilm phase following photosensitization with all curcumin concentrations tested. To achieve significant bacterial reduction (p <0.05) in carious dentine, it was necessary to utilize 5.0 g/L of curcumin in association with blue light. No significant reduction was found for L-D+, supporting the absence of the drug's dark toxicity. S. mutans and L. acidophilus were susceptible to curcumin in the presence of blue light. However, due to light penetration and drug diffusion difficulties, these microorganisms within dentine carious lesions were less affected than they were in the biofilm phase. © 2013 Springer-Verlag London.

Locomoção visualmente guiada na transposição de obstáculos: efeitos de amostras visuais estáticas e dinâmica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise da microfenda axial em cavidades classe V restauradas com resina composta e polimerizadas com diferentes fontes de luz. Estudo pela microscopia eletrônica de varredura

Pós-graduação em Ciências Odontológicas - FOAR

Desenvolvimento e caracterização de dispositivos luminescentes híbridos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)