Effect of carbamide peroxide bleaching gel on composite resin flexural strength and microhardness

This study investigated the effect of 16% carbamide peroxide (Whiteness Perfect/FGM) on the Vickers microhardness and flexural strength of the restorative composites Filtek Z100 (hybrid), Filtek Z350 (nanofill), Brilliant (micro-hybrid) and Opallis (micro-hybrid). Discshaped (4×2 mm; n=5) and bar-shaped (12×2×1 mm; n=10) specimens of each restorative material were randomly divided into 2 groups: (G1) 16 weeks stored in distilled water; (G2) 16 weeks stored in distilled water, with 16% carbamide peroxide application during 6 h per day for the last 4 weeks. The mechanical properties were evaluated using a Vickers microhardness tester and a mechanical testing machine. Data were analyzed by twoway ANOVA and Tukey's (HSD) post-hoc test (α=0.05). Filtek Z100 presented the highest microhardness value, followed by Filtek Z350 and finally by Brilliant and Opallis (p=0.00). Filtek Z100 and Brilliant exhibited the highest flexural strength value, followed by Filtek Z350 and Opallis (p=0.00). Bleaching treatment decreased significantly microhardness of Brilliant and Opallis (p=0.00). The flexural strength of all studied materials was not affected by the home bleaching (p=0.28).

The 125 GeV boson: A composite scalar?

Assuming that the 125 GeV particle observed at the LHC is a composite scalar and responsible for the electroweak gauge symmetry breaking, we consider the possibility that the bound state is generated by a non-Abelian gauge theory with dynamically generated gauge boson masses and a specific chiral symmetry breaking dynamics motivated by confinement. The scalar mass is computed with the use of the Bethe-Salpeter equation and its normalization condition as a function of the SU(N) group and the respective fermionic representation. If the fermions that form the composite state are in the fundamental representation of the SU(N) group, we can generate such a light boson only for one specific number of fermions for each group. We address the uncertainties underlying this result, when considering the strong dynamics in isolation. © 2013 American Physical Society.

Influence of filler charge on gloss of composite materials before and after in vitro toothbrushing

Objectives: This study evaluated the gloss behaviour of experimental resin composites loaded with different filler percentages, immediately after polishing and after toothbrushing simulation. Methods: Sixteen disc-shaped specimens were fabricated for each different-charged composite (40%, 50%, 60%, 70% and 75%) and polished with SiC abrasive papers. Gloss measurements were made prior to simulated toothbrushing. The specimens were subjected to the simulation for 5, 15, 30 and 60 min using an electrical toothbrush with a standardized pressure while being immersed in a toothpaste/artificial saliva slurry. Results: Baseline composite gloss values ranged from 69.7 (40%) to 81.3 (75%) GU (gloss units) and from 18.1 (40%) to 32.3 (75%) GU after 1 h of brushing. Highest gloss values were obtained by 75%-charged resin, while the lowest values were obtained by the 40%-charged one. Conclusions: All tested materials showed a gloss decrease. However, the higher filler load a composite resin has, the higher gloss it can achieve. Clinical significance: Gloss of resin composite materials is an important factor in determining aesthetic success of anterior restorations, and this property may vary according to the filler charge of the restorative material. Higher filler load of a composite resin results in higher gloss values. © 2013 Elsevier Ltd. All rights reserved.

Cost-effective composite electrode for the fast voltammetric screening and determination of riboflavin (B2) and pyridoxine (B6) in pharmaceuticals

Different solid composites made by mechanical dispersions of graphite particles into heated paraffin (from 65 to 80% graphite, in mass) were prepared and assessed in order to optimize their use in electrochemical and electroanalytical procedures for bioanalysis. Besides these, composites were also evaluated by thermoanalytical techniques aiming to study their conservation and long-term stability (over eight months without special care), among others. Best results were found at 80% m/m graphite in paraffin. Such electrode combines low-cost, stability, sensitivity, ease of maintenance and clearance, besides the possibilities of manufacture in many different forms and shapes (with or without modifications) and applicability in a wide range of pH. Electrochemical studies by different voltammetric techniques involving vitamins from complex B (riboflavin and pyridoxine) leaded to a better understanding about their electrooxidative processes onto carbon-composite electrodes, specially regarding reversibility and pH-dependence. Data were also acquired and optimized with analytical purposes, being square-wave voltammetry in pH 4.2 chosen by its many advantages. Good linearity between peak responses as function of concentration were reached from 5 to 43 μmol L-1 for riboflavin (peak at -0.257 V) and up to 8.5 × 10-4 mol L -1 for pyridoxine (peak at +1.04 V), best studied conditions; limits of detection (at an S/N of 3) for both analites showed to be circa 1.0 mol L-1. Different commercial samples were analyzed for riboflavin (EMS® complex B syrup) and pyridoxine (Citoneurin 5000 Merck® ampoules) providing 96.6% and 98.7% recoveries, respectively.

Comparison of shear bond strength of orthodontics brackets on composite resin restorations with different surface treatments

INTRODUÇÃO: frequentemente, os pacientes ortodônticos apresentam restaurações de resina composta; no entanto, existem poucos estudos que avaliam a melhor forma de colagem ortodôntica nessa situação. OBJETIVO: o objetivo do presente trabalho foi avaliar a força adesiva de braquetes ortodônticos em restaurações resinosas com tratamento de superfície. MÉTODOS: foram utilizados 51 incisivos inferiores bovinos divididos aleatoriamente em três grupos. No grupo controle (GC), os braquetes foram colados em esmalte dentário; nos grupos experimentais com tratamento (GCT) e sem tratamento (GST), os braquetes foram colados em restauração de resina previamente realizada, diferenciando-se pelo tratamento de superfície com broca diamantada. Os dentes foram incluídos em tubos de PVC com resina acrílica autopolimerizável. O ensaio de cisalhamento foi executado em máquina universal de ensaios Emic. Os grupos foram submetidos à ANOVA com pós-teste de Tukey para verificação da diferença estatística entre os grupos (α = 0,05). RESULTADOS: GC (6,62MPa) e GCT (6,82MPa) apresentaram resultados semelhantes, enquanto o GST (5,07MPa) obteve resultados estatisticamente menores (p < 0,05). CONCLUSÃO: conclui-se que a melhor técnica de colagem de braquetes ortodônticos em restaurações de resina composta é a de realização de desgaste sobre a superfície.

Comparison of Physicochemical Surface Conditioning Methods for Adhesion of bis-GMA Resin Cement to Particulate Filler Composite and Surface Characterization

This study compared the effect of physicochemical surface conditioning methods on the adhesion of bis-GMA-based resin cement to particulate filler composite (PFC) used for indirect dental restorations. PFC blocks (N (block)=54, n (block)=9 per group) were polymerized and randomly subjected to one of the following surface conditioning methods: a) No conditioning (Control-C), b) Hydrofluoric acid (HF)etching for 60s (AE60), c) HF for 90s (AE90), d) HF for 120s (AE120), e) HF for 180s (AE180), and f) air-abrasion with 30 mu m silica-coated alumina particles (AB). The conditioned surfaces were silanized with an MPS silane, and an adhesive resin was applied. Resin composite blocks were bonded to PFC using resin cement and photo-polymerized. PFC-cement-resin composite blocks were cut under coolant water to obtain bar specimens (1mmx0.8mm). Microtensile bond strength test (mu TBS)was performed in a universal testing machine (1mm/min). After debonding, failure modes were classified using stereomicroscopy. Surface characterization was performed on a set of separate specimen surfaces using Scanning Electron Microscopy (SEM), X-Ray Dispersive Spectroscopy (XDS), X-Ray Photoelectron Spectroscopy (XPS), and Fourier Transform-Raman Spectroscopy (FT-RS). Mean mu TBS (MPa) of C (35.6 +/- 4.9) was significantly lower than those of other groups (40.2 +/- 5.6-47.4 +/- 6.1) (p<0.05). The highest mu TBS was obtained in Group AB (47.4 +/- 6.1). Prolonged duration of HF etching increased the results (AE180: 41.9 +/- 7), but was not significantly different than that of AB (p>0.05). Failure types were predominantly cohesive in PFC (34 out of 54) followed by cohesive failure in the cement (16 out of 54). Degree of conversion (DC) of the PFC was 63 +/- 10%. SEM analysis showed increased irregularities on PFC surfaces with the increased etching time. Chemical surface analyses with XPS and FT-RS indicated 11-70% silane on the PFC surfaces that contributed to improved bond strength compared to Group C that presented 5% silane, which seemed to be a threshold. Group AB displayed 83% SiO2 and 17% silane on the surfaces.

New biphasic mono-component composite material obtained by partial oxypropylation of bacterial cellulose

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Photodegradation of phenol red on a Ni-doped niobate/carbon composite

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

Resin composite characterizations following a simplified protocol of accelerated aging as a function of the expiration date

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Polymer Matrix-Based Piezoelectric Composite for Structural Health Monitoring

Structural health monitoring (SHM) refers to the procedure of assessing the structure conditions continuously so it is an alternative to conventional nondestructive evaluation (NDE) techniques [1]. With the growing developments in sensor technology acoustic emission (AE) technology has been attracting attention in SHM applications. AE are characterized by waves produced by the sudden internal stress redistribution caused by the changes in the internal structure, such as fatigue, crack growth, corrosion, etc. Piezoelectric materials such as Lead Zirconate Titanate (PZT) ceramic have been widely used as sensor due to its high electromechanical coupling factor and piezoelectric d coefficients. Because of the poor mechanical characteristic and the lack in the formability of the ceramic, polymer matrix-based piezoelectric composites have been studied in the last decade in order to obtain better properties in comparison with a single phase material. In this study a composite film made of polyurethane (PU) and PZT ceramic particles partially recovered with polyaniline (PAni) was characterized and used as sensor for AE detection. Preliminary results indicate that the presence of a semiconductor polymer (PAni) recovering the ceramic particles, make the poling process easier and less time consuming. Also, it is possible to observe that there is a great potential to use such type of composite as sensor for structure health monitoring.

Measurement of Radiant Energy using Pyroelectric Polymer/Ceramic Composite

Monitoring non-ionizing radiant energy is increasingly demanded for many applications such as automobile, biomedical and security system. Thermal type infrared (IR) sensors can operate at room temperature and pyroelectric materials have high sensitivity and accuracy for that application. Working as thermal transducer pyroelectric sensor converts the non-quantified thermal flux into the output measurable quantity of electrical charge, voltage or current. In the present study the composite made of poly(vinylidene fluoride) -PVDF and lead zirconate titanate (PZT) partially recovered with polyaniline (PAni) conductor polymer has been used as sensor element. The pyroelectric coefficient p(T) was obtained by measuring the pyroelectric reversible current, i.e., measuring the thermally stimulated depolarization current (TSDC) after removing all irreversible contribution to the current such as injected charge during polarization of the sample. To analyze the sensing property of the pyroelectric material, the sensor is irradiated by a high power light source (halogen lamp of 250 W) that is chopped providing a modulated radiation. A device assembled in the laboratory is used to change the light intensity sensor, an aluminum strip having openings with diameters ranging from 1 to 10 mm incremented by one millimeter. The sensor element is assembled between two electrodes while its frontal surface is painted black ink to maximize the light absorption. The signal from the sensor is measured by a Lock-In amplifier model SR530 -Stanford Research Systems. The behavior of the output voltage for an input power at several frequencies for PZT-PAni/PVDF (30/ 70 vol%) composite follows the inverse power law (1/ f) and the linearity can be observed in the frequency range used.

Composite interval mapping and mixed models reveal QTL associated with performance and carcass traits on chicken chromosomes 1, 3, and 4

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

Adhesive bonding of resin composite to various titanium surfaces using diferente metal conditioners and a surface modification system

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

Evaluation of bond strength and thickness of adhesive layer according to the techniques of applying adhesives in composite resin restorations

Adhesive restorations have increasingly been used in dentistry, and the adhesive system application technique may determine the success of the restorative procedure. The aim of this study was to evaluate the influence of the application technique of two adhesive systems (Clearfil SE Bond and Adper Scotchbond MultiPurpose) on the bond strength and adhesive layer of composite resin restorations. Eight human third molars were selected and prepared with Class I occlusal cavities. The teeth were restored with composite using various application techniques for both adhesives, according to the following groups (n = 10): group 1 (control), systems were applied and adhesive was immediately light activated for 20 seconds without removing excesses; group 2, excess adhesive was removed with a gentle jet of air for 5 seconds; group 3, excess was removed with a dry microbrush-type device; and group 4, a gentle jet of air was applied after the microbrush and then light activation was performed. After this, the teeth were submitted to microtensile testing. For the two systems tested, no statistical differences were observed between groups 1 and 2. Groups 3 and 4 presented higher bond strength values compared with the other studied groups, allowing the conclusion that excess adhesive removal with a dry micro-brush could improve bond strength in composite restorations. Predominance of adhesive fracture and thicker adhesive layer were observed via scanning electron microscopy (SEM) in groups 1 and 2. For groups 3 and 4, a mixed failure pattern and thinner adhesive layer were verified. Clinicians should be aware that excess adhesive may negatively affect bond strength, whereas a thin, uniform adhesive layer appears to be favorable. (Quintessence Int 2013;44:9-15)

Bond strength of composite to dentin: effect of acid etching and laser irradiation through an uncured self-etch adhesive system

This study evaluated the effect on micro-tensile bond strength (mu-TBS) of laser irradiation of etched/unetched dentin through an uncured self-etching adhesive. Dentinal surfaces were treated with Clearfil SE Bond Adhesive (CSE) either according to the manufacturer's instructions (CSE) or without applying the primer (CSE/NP). The dentin was irradiated through the uncured adhesive, using an Nd: YAG laser at 0.75 or 1 W power settings. The adhesive was cured, composite crowns were built up, and the teeth were sectioned into beams (0.49 mm(2)) to be stressed under tension. Data were analyzed using one-way ANOVA and Tukey statistics (alpha = 5%). Dentin of the fractured specimens and the interfaces of untested beams were observed under scanning electron microscopy (SEM). The results showed that non-etched irradiated surfaces presented higher mu-TBS than etched and irradiated surfaces (p < 0.05). Laser irradiation alone did not lead to differences in mu-TBS (p > 0.05). SEM showed solidification globules on the surfaces of the specimens. The interfaces were similar on irradiated and non-irradiated surfaces. Laser irradiation of dentin through the uncured adhesive did not lead to higher mu-TBS when compared to the suggested manufacturer's technique. However, this treatment brought benefits when performed on unetched dentin, since bond strengths were higher when compared to etched dentin.