Evaluation of experimental cleanser solution of Ricinus communis: effect on soft denture liner properties

Objective: This study evaluated colour stability, hardness and roughness of soft denture liners after immersion in various cleansers. Materials and methods: Thirty specimens (14 mm x 4 mm) of Elite Soft Relining (ES) and Mucopren Soft (MS) were randomly immersed in distilled water at 37 degrees C, sodium hypochlorite 1%, and an experimental Ricinus communis solution (RC) for 7, 15 and 183 continuous days. Results: ANOVA (p < 0.05) and Tukey's test indicated that after T7 (mu =8.79 +/- 7.36); T15 (mu = 4.23 +/- 2.62) and T183 (mu = 8.78 +/- 3.16), MS presented a higher increase in hardness than ES. After T7, MS underwent an increase in roughness (mu = 0.09 +/- 0.80); ES underwent a decrease (mu = -0.08 +/- 0.16). RC caused the smallest variation in roughness. After T15, both materials presented an increase in roughness. After T183, ES (mu = -0.30 +/- 0.48) presented a higher roughness variation than MS (mu = -0.07 +/- 0.32). Hypochlorite caused an increase in roughness (mu = 0.02 +/- 0.19). Conclusion: After all periods ES presented higher colour alteration than MS; highest colour alteration was caused by hypochlorite. Both materials were more stable after immersion in RC.

Síntesi i propietats de vidres metàl•lics massissos i materials nanocomposites basats en Fe per aplicacions com a materials magnètics tous

Estudi realitzat a partir d’una estada a l’ Institut für Komplexe Materialien, Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, entre 2010 i 2011. S'ha explorat l'efecte de les condicions i influència dels elements d'aleació en la capacitat de formació de vidre, l'estructura i les propietats tèrmiques i magnètiques de vidres metàl•lics massissos i materials nanocristal•lins en base Fe. La producció d'aquests materials en forma de cintes de unes 20 micres de gruix ha estat àmpliament estudiada i s'ha vist que presenten unes propietats excel•lents com a materials magnètics tous. El propòsit general d'aquest projecte era l'obtenció de composicions òptimes amb alta capacitat de formar vidre i amb excel•lents propietats magnètiques com a materials magnètics tous combinat amb bones propietats mecàniques. El projecte prenia com a punt de partida l'aliatge [FeCoBSi]96Nb4 ja que és el que presenta millor capacitat de formar vidre i presenta una alta imantació de saturació i baix camp coercitiu. S'ha fet un estudi dels factors fonamentals que intervenen en la formació de l'estat vitri. La composició abans esmentada ha estat variada amb l'addició d'altres elements per estudiar com afecten aquests nous elements a les propietats, la formació de vidre i l'estructura dels aliatges resultants amb l'objectiu de millorar-ne les propietats magnètiques i la capacitat de formació de vidre. Entre altres s'ha usat el Zr, Mo, Y i el Gd per millorar la formació de vidre; i el Co i el Ni per millorar les propietats magnètiques a alta temperatura. S'han estudiat les relacions entre la capacitat de formació de vidre i la seva estabilitat tèrmica, la resistència a la cristal•lització i la estructura de l'aliatge resultant després del procés de solidificació. Per aquest estudi s'han determinat els mecanismes que controlen la transformació i la seva cinètica així com les fases que es formen durant el tractament tèrmic permetent la formulació de models predictius.

Use of Facial Protection to Prevent Reinjury During Sports Practice

The objective of the study was to report the prevention of facial reinjury of a volleyball player using a custom-made protective facial shield. A custom-made protective partial facial shield was fabricated using polymethylmethacrylate and was fitted with a soft lining material to provide additional comfort and protection to the injured area. Facial protection provides greater security against possible facial injuries and allows injured areas to recover during sports practice.

Effect of microwave disinfection on the hardness and adhesion of two resilient liners

Statement of problem. Microwave irradiation has been suggested for denture disinfection. However, the effect of this procedure on the hardness and bond strength between resilient liners and denture base acrylic resin is not known.Purpose. This study evaluated the effect of water storage time and microwave disinfection on the hardness and peel bond strength of 2 silicone resilient lining materials to a heat-polymerized acrylic resin.Material and methods. Acrylic resin (Lucitone 199) specimens (75 X 10 X 3 mm) were stored in water at 37 degrees C (2 or 30 days) before bonding (n = 160). The resilient lining materials (GC Reline Extra Soft and Dentusil) were bonded to the denture base and divided into the following 4 groups (n = 10): Tests performed immediately after bonding (control); specimens immersed in water (200 mL) and irradiated twice, with 650 W for 6 minutes; specimens irradiated daily for 7 total cycles of disinfection; specimens immersed in water (37 degrees C) for 7 days. Specimens were submitted to a 180-degree peel test (at a crosshead speed of 10 mm/min) and the failure values (MPa) and mode of failure were recorded. Pretreatment and posttreatment hardness measurements (Shore A) of the resilient materials were also performed. Three-way analysis of variance, followed by the Tukey HSD test, was performed (alpha=.05).Results. The analysis revealed that, for all conditions, the mean failure strengths of GC Reline Extra Soft (0.95-1.19 MPa) were significantly higher (P<.001) than those of Dentusil (0.45-0.50 MPa). The adhesion of the liners was not adversely affected by water storage time of Lucitone 199 or microwave disinfection. All peel test failures were cohesive. There was a small but significant difference (P<.001) between the pretreatment (34.33 Shore A) and posttreatment (38.69 Shore A) hardness measurements.Conclusion. Microwave disinfection did not compromise the hardness of either resilient liners or their adhesion to the denture base resin Lucitone 199.

Cytotoxicity of denture base and hard chairside reline materials: a systematic review

Statement of problem. Adverse reactions to the materials used for the fabrication and reline of removable denture bases have been observed.Purpose. The purpose of this study was to systematically review the published literature on the cytotoxicity of denture base and hard reline materials.Material and methods. MEDLINE via PubMed, Google Scholar, and Scopus databases for the period January 1979 to December 2009 were searched with the following key words: (biocompatibility OR cytotoxic* OR allergy OR burning mouth OR cell culture techniques) and (acrylic resins OR denture OR monomer OR relin* OR denture liners). The inclusion criteria included in vitro studies using either animal or human cells, in which the cytotoxicity of the denture base and hard chairside reline resins was tested. Studies of resilient lining materials and those that evaluated other parameters such as genotoxicity and mutagenicity were excluded. Articles published in the English language and in peer-reviewed journals focusing on the cytotoxicity of these materials were reviewed.Results. A total of 1443 articles were identified through the search. From these, 20 studies were judged to meet the selection criteria and were included in the review. In the majority of the studies, continuous cell lines were exposed to eluates of specimens made from the materials, and mitochondrial activity was used to estimate cell viability. The tested acrylic resins were grouped according to 5 major categories: (1) heat-polymerized; (2) microwave-polymerized; (3) autopolymerizing; (4) light-polymerized; and (5) hard chairside reliners.Conclusions. This review provided some evidence that the heat-polymerized resins showed lower cytotoxic effects than autopolymerizing denture base acrylic resins and light or dual polymerized reline resins. However, because of the large number of variables in the reviewed literature, a definitive conclusion could not be drawn. (J Prosthet Dent 2012;107:114-127)

Effect of curing regime on the cytotoxicity of resin-modified glass-ionomer lining cements applied to an odontoblast-cell line

Objective: The aim of this in vitro study was to evaluate the cytotoxicity of resin-modified glass-ionomer lining cements submitted to different curing regimes and applied to an immortalized odontoblast-cell line (MDPC-23). Methods: Forty round-shaped specimens of each experimental material (Fuji Lining LC and Vitrebond) were prepared. They were light-cured for the manufacturers' recommended time (MRT = 30 s), under-cured (0.5 MRT = 15 s), over-cured (1.5 MRT = 45 s) or allowed to dark cure (0 MRT). Sterilized filter papers soaked with either 5 μL of PBS or HEMA were used as negative and positive control, respectively. After placing the specimens individually in wells of 24-well dishes, odontoblast-like cells MDPC-23 (30,000 cells/cm2) were plated in each well and incubated for 72 h in a humidified incubator at 37 °C with 5% CO2 and 95% air. The cytotoxicity was evaluated by the cell metabolism (MTT assay) and cell morphology (SEM). Results: Fuji Lining LC was less cytotoxic than Vitrebond (p < 0.05) in all the experimental conditions. However, the cytotoxicity of Fuji Lining LC was noticeably increased in the absence of light-curing while the same was not observed for Vitrebond. The length of light-curing (15, 30 or 45 s) did not influence the toxicity of both lining materials when they were applied on the odontoblast-cell line MDPC-23. Significance: The light-activation plays an important role in reducing the cytotoxicity of Fuji Lining LC. Following the manufacturer' recommendation regarding the light-curing regime may prevent toxic effect to the pulp cells. © 2005 Academy of Dental Materials.

Cu0.5Zn0.5Fe2O4 ferrite for application as a soft magnetic material

This work involved the synthesis and characterization of Cu0.5Zn0.5Fe2O4 ferrite powders prepared by combustion reaction for use as soft magnetic materials. The powders were characterized by nitrogen adsorption (BET), XRD, Rietveld refinement, SEM, TEM and magnetic measures. The results indicate that the combustion reaction yielded crystalline powders containing spinel ferrite as the primary phase and traces of Fe2O3 as secondary phase. The crystallite size and lattice microdeformation calculated from Rietveld refinements were 36 and 0.24 nm, respectively. The micrographic analysis revealed particles smaller than 100 nm and fine particle agglomerates. The particles were approximately spherical and their size, calculated by TEM, was 29 nm. The magnetic parameters indicated that the Cu-Zn ferrite powders presented closed hysteresis loops and soft magnetic properties. © (2012) Trans Tech Publications, Switzerland.

Análise fotoelástica da tensão entre diferentes tipos de sistemas de retenção em próteses obturadoras palatinas implanto-retidas ou não e com ou sem reembasamento “soft”

Pós-graduação em Odontologia - FOA

Peel bond strength of resilient liner modified by the addition of antimicrobial agents to denture base acrylic resin

In order to prolong the clinical longevity of resilient denture relining materials and reduce plaque accumulation, incorporation of antimicrobial agents into these materials has been proposed. However, this addition may affect their properties. Objective: This study evaluated the effect of the addition of antimicrobial agents into one soft liner (Soft Confort, Dencril) on its peel bond strength to one denture base (QC 20, Dentsply). Material and Methods: Acrylic specimens (n=9) were made (75x10x3 mm) and stored in distilled water at 37 degrees C for 48 h. The drug powder concentrations (nystatin 500,000U - G2; nystatin 1,000,000U - G3; miconazole 125 mg - G4; miconazole 250 mg - G5; ketoconazole 100 mg - G6; ketoconazole 200 mg - G7; chlorhexidine diacetate 5% - G8; and 10% chlorhexidine diacetate - G9) were blended with the soft liner powder before the addition of the soft liner liquid. A group (G1) without any drug incorporation was used as control. Specimens (n=9) (75x10x6 mm) were plasticized according to the manufacturers' instructions and stored in distilled water at 37 degrees C for 24 h. Relined specimens were then submitted to a 180-degree peel test at a crosshead speed of 10 mm/min. Data (MPa) were analyzed by analysis of variance (alpha=0.05) and the failure modes were visually classified. Results: No significant difference was found among experimental groups (p=0.148). Cohesive failure located within the resilient material was predominantly observed in all tested groups. Conclusions: Peel bond strength between the denture base and the modified soft liner was not affected by the addition of antimicrobial agents.

Modeling mechanical response of heterogeneous materials

Heterogeneous materials are ubiquitous in nature and as synthetic materials. These materials provide unique combination of desirable mechanical properties emerging from its heterogeneities at different length scales. Future structural and technological applications will require the development of advanced light weight materials with superior strength and toughness. Cost effective design of the advanced high performance synthetic materials by tailoring their microstructure is the challenge facing the materials design community. Prior knowledge of structure-property relationships for these materials is imperative for optimal design. Thus, understanding such relationships for heterogeneous materials is of primary interest. Furthermore, computational burden is becoming critical concern in several areas of heterogeneous materials design. Therefore, computationally efficient and accurate predictive tools are highly essential. In the present study, we mainly focus on mechanical behavior of soft cellular materials and tough biological material such as mussel byssus thread. Cellular materials exhibit microstructural heterogeneity by interconnected network of same material phase. However, mussel byssus thread comprises of two distinct material phases. A robust numerical framework is developed to investigate the micromechanisms behind the macroscopic response of both of these materials. Using this framework, effect of microstuctural parameters has been addressed on the stress state of cellular specimens during split Hopkinson pressure bar test. A voronoi tessellation based algorithm has been developed to simulate the cellular microstructure. Micromechanisms (microinertia, microbuckling and microbending) governing macroscopic behavior of cellular solids are investigated thoroughly with respect to various microstructural and loading parameters. To understand the origin of high toughness of mussel byssus thread, a Genetic Algorithm (GA) based optimization framework has been developed. It is found that two different material phases (collagens) of mussel byssus thread are optimally distributed along the thread. These applications demonstrate that the presence of heterogeneity in the system demands high computational resources for simulation and modeling. Thus, Higher Dimensional Model Representation (HDMR) based surrogate modeling concept has been proposed to reduce computational complexity. The applicability of such methodology has been demonstrated in failure envelope construction and in multiscale finite element techniques. It is observed that surrogate based model can capture the behavior of complex material systems with sufficient accuracy. The computational algorithms presented in this thesis will further pave the way for accurate prediction of macroscopic deformation behavior of various class of advanced materials from their measurable microstructural features at a reasonable computational cost.

Hot-spots during the calcination of MCM-41:a SAXS comparative analysis of a soft mesophase

The phenomenon of microscopic hot-spots, during the calcination of MCM-41, was investigated by quantifying the magnitude of the temperature increase during the calcination of a soft MCM-41 mesophase using a SAXS comparative study. This was performed by thermally treating a soft material that was detemplated via Fenton chemistry followed by equilibrating and drying in a low-surface-tension solvent (n-butanol or N,N-dimethylformamide); these samples have limited structural shrinkage. The resulting samples were thermally treated at increasing temperatures, and the structural shrinkage was compared with that of the directly calcined material. By comparing the structural shrinkage, it was found that the microscopic temperature increase would fall between 190 and 250 C, as deduced from N,N-dimethyl-formamide and n-butanol. The order of magnitude of the temperature increase appears to be consistent with the well-known glow effect. It is, however, substantially higher than the experimentally determined macroscopic temperature increase. Several aspects are discussed to interpret this difference. © 2013 Elsevier B.V.

Mechanochemistry for Active Materials and Devices

The coupling of mechanical stress fields in polymers to covalent chemistry (polymer mechanochemistry) has provided access to previously unattainable chemical reactions and polymer transformations. In the bulk, mechanochemical activation has been used as the basis for new classes of stress-responsive polymers that demonstrate stress/strain sensing, shear-induced intermolecular reactivity for molecular level remodeling and self-strengthening, and the release of acids and other small molecules that are potentially capable of triggering further chemical response. The potential utility of polymer mechanochemistry in functional materials is limited, however, by the fact that to date, all reported covalent activation in the bulk occurs in concert with plastic yield and deformation, so that the structure of the activated object is vastly different from its nascent form. Mechanochemically activated materials have thus been limited to “single use” demonstrations, rather than as multi-functional materials for structural and/or device applications. Here, we report that filled polydimethylsiloxane (PDMS) elastomers provide a robust elastic substrate into which mechanophores can be embedded and activated under conditions from which the sample regains its original shape and properties. Fabrication is straightforward and easily accessible, providing access for the first time to objects and devices that either release or reversibly activate chemical functionality over hundreds of loading cycles.

While the mechanically accelerated ring-opening reaction of spiropyran to merocyanine and associated color change provides a useful method by which to image the molecular scale stress/strain distribution within a polymer, the magnitude of the forces necessary for activation had yet to be quantified. Here, we report single molecule force spectroscopy studies of two spiropyran isomers. Ring opening on the timescale of tens of milliseconds is found to require forces of ~240 pN, well below that of previously characterized covalent mechanophores. The lower threshold force is a combination of a low force-free activation energy and the fact that the change in rate with force (activation length) of each isomer is greater than that inferred in other systems. Importantly, quantifying the magnitude of forces required to activate individual spiropyran-based force-probes enables the probe behave as a “scout” of molecular forces in materials; the observed behavior of which can be extrapolated to predict the reactivity of potential mechanophores within a given material and deformation.

We subsequently translated the design platform to existing dynamic soft technologies to fabricate the first mechanochemically responsive devices; first, by remotely inducing dielectric patterning of an elastic substrate to produce assorted fluorescent patterns in concert with topological changes; and second, by adopting a soft robotic platform to produce a color change from the strains inherent to pneumatically actuated robotic motion. Shown herein, covalent polymer mechanochemistry provides a viable mechanism to convert the same mechanical potential energy used for actuation into value-added, constructive covalent chemical responses. The color change associated with actuation suggests opportunities for not only new color changing or camouflaging strategies, but also the possibility for simultaneous activation of latent chemistry (e.g., release of small molecules, change in mechanical properties, activation of catalysts, etc.) in soft robots. In addition, mechanochromic stress mapping in a functional actuating device might provide a useful design and optimization tool, revealing spatial and temporal force evolution within the actuator in a way that might also be coupled to feedback loops that allow autonomous, self-regulation of activity.

In the future, both the specific material and the general approach should be useful in enriching the responsive functionality of soft elastomeric materials and devices. We anticipate the development of new mechanophores that, like the materials, are reversibly and repeatedly activated, expanding the capabilities of soft, active devices and further permitting dynamic control over chemical reactivity that is otherwise inaccessible, each in response to a single remote signal.

Magnetization studies of binary and ternary Co-rich phases of the Co-Si-B system

CoB, CO(2)B, CoSi, Co(2)Si and CO(5)Si(2)B phases can be formed during heat-treatment of amorphous co-Si-B soft magnetic materials. Thus, it is important to determine their magnetic behavior as a function of applied field and temperature. In this study, polycrystalline single-phase samples of the above phases were produced via arc melting and heat-treatment under argon. The single-phase nature of the samples was confirmed via X-ray diffraction experiments. AC and DC magnetization measurements showed that Co(2)Si and CO(5)Si(2)B phases are paramagnetic. Minor amounts of either Co(2)Si or CoSi(2) in the CoSi-phase sample suggested a paramagnetic behavior of the CoSi-phase, however, it should be diamagnetic as shown in the literature. The diamagnetic behavior of the CoB phase was also confirmed. The paramagnetic behavior of CO(5)Si(2)B is for the first time reported. The magnetization results of the phase CO(2)B have a ferromagnetic signature already verified on previous NMR studies. A detailed set of magnetization measurements of this phase showed a change of the easy magnetization axis starting at 70K, with a temperature interval of about 13K at a very small field of 1 mT. As the strength of the field is increased the temperature interval is enlarged. The strength of field at which the magnetization saturates increases almost linearly as the temperature is increased above 70K. The room temperature total magnetostriction of the CO(2)B phase was determined to be 8 ppm at a field of 1T. (C) 2010 Elsevier B.V. All rights reserved.

Effect of repeated cycles of chemical disinfection on the roughness and hardness of hard reline acrylic resins

Objective: The aim of this study was to assess the effect of repeated cycles of five chemical disinfectant solutions on the roughness and hardness of three hard chairside reliners. Methods: A total of 180 circular specimens (30 mm x 6 mm) were fabricated using three hard chairside reliners (Jet; n = 60, Kooliner; n = 60, Tokuyama Rebase II Fast; n = 60), which were immersed in deionised water (control), and five disinfectant solutions (1%, 2%, 5.25% sodium hypochlorite; 2% glutaraldehyde; 4% chlorhexidine gluconate). They were tested for Knoop hardness (KHN) and surface roughness (mu m), before and after 30 simulated disinfecting cycles. Data was analysed by the factorial scheme (6 x 2), two-way analysis of variance (anova), followed by Tukey`s test. Results: For Jet (from 18.74 to 13.86 KHN), Kooliner (from 14.09 to 8.72 KHN), Tokuyama (from 12.57 to 8.28 KHN) a significant decrease in hardness was observed irrespective of the solution used on all materials. For Jet (from 0.09 to 0.11 mu m) there was a statistically significant increase in roughness. Kooliner (from 0.36 to 0.26 mu m) presented a statistically significant decrease in roughness and Tokuyama (from 0.15 to 0.11 mu m) presented no statistically significant difference after 30 days. Conclusions: This study showed that all disinfectant solutions promoted a statistically significant decrease in hardness, whereas with roughness, the materials tested showed a statistically significant increase, except for Tokuyama. Although statistically significant values were registered, these results could not be considered clinically significant.

Real-time rheology of actively growing bacteria

The population growth of a Staphylococcus aureus culture, an active colloidal system of spherical cells, was followed by rheological measurements, under steady-state and oscillatory shear flows. We observed a rich viscoelastic behavior as a consequence of the bacteria activity, namely, of their multiplication and density-dependent aggregation properties. In the early stages of growth (lag and exponential phases), the viscosity increases by about a factor of 20, presenting several drops and full recoveries. This allows us to evoke the existence of a percolation phenomenon. Remarkably, as the bacteria reach their late phase of development, in which the population stabilizes, the viscosity returns close to its initial value. Most probably, this is caused by a change in the bacteria physiological activity and in particular, by the decrease of their adhesion properties. The viscous and elastic moduli exhibit power-law behaviors compatible with the "soft glassy materials" model, whose exponents are dependent on the bacteria growth stage. DOI: 10.1103/PhysRevE.87.030701.