Anthocyanin incorporated dental copolymer: bacterial growth inhibition, mechanical properties, and compound release rates and stability by (1)h NMR

Objective. To evaluate bacterial growth inhibition, mechanical properties, and compound release rate and stability of copolymers incorporated with anthocyanin (ACY; Vaccinium macrocarpon). Methods. Resin samples were prepared (Bis-GMA/TEGDMA at 70/30 mol%) and incorporated with 2 w/w% of either ACY or chlorhexidine (CHX), except for the control group. Samples were individually immersed in a bacterial culture (Streptococcus mutans) for 24 h. Cell viability (n = 3) was assessed by counting the number of colony forming units on replica agar plates. Flexural strength (FS) and elastic modulus (E) were tested on a universal testing machine (n = 8). Compound release and chemical stability were evaluated by UV spectrophotometry and (1)H NMR (n = 3). Data were analyzed by one-way ANOVA and Tukey's test ( α = 0.05). Results. Both compounds inhibited S. mutans growth, with CHX being most effective (P < 0.05). Control resin had the lowest FS and E values, followed by ACY and CHX, with statistical difference between control and CHX groups for both mechanical properties (P < 0.05). The 24 h compound release rates were ACY: 1.33 μg/mL and CHX: 1.92 μg/mL. (1)H NMR spectra suggests that both compounds remained stable after being released in water. Conclusion. The present findings indicate that anthocyanins might be used as a natural antibacterial agent in resin based materials.

Structure, microstructure, and selected mechanical properties of Ti-Zr-Mo alloys for biomedical applications

New titanium alloys for biomedical applications have been developed primarily with the addition of Nb, Ta, Mo, and Zr, because those elements stabilize the β phase and they don’t cause cytotoxicity in the organism. The objective of this paper is to analyze the effect of molybdenum on the structure, microstructure, and selected mechanical properties of Ti-15Zr-xMo (x = 5, 10, 15, and 20 wt%) alloys. The samples were produced in an arc-melting furnace with inert argon atmosphere, and they were hot-rolled and homogenized. The samples were characterized using chemical, structural, and microstructural analysis. The mechanical analysis was made using Vickers microhardness and Young’s modulus measurements. The compositions of the alloys were sensitive to the molybdenum concentration, indicating the presence of α’+α”+β phases in the Ti-15Zr-5Mo alloy, α”+β in the Ti-15Zr-10Mo alloy, and β phase in the Ti-15Zr-15Mo and Ti-15Zr-20Mo alloys. The mechanical properties showed favorable values for biomedical application in the alloys presenting high hardness and low Young’s modulus compared with CP-Ti.

Effect of heat treatment on microstructure and mechanical properties of Ti-5wt-%Ni alloys for use as biomaterial

Titanium alloys are among the most important and frequently used class of biomaterials. In addition to biocompatibility, it is important that an implant material present satisfactory mechanical properties that allow long term use in the body. To improve such properties, different heat treatments are used, as well as doping with oxygen. The presence of interstitial oxygen in the crystal lattice causes deformation, increases the hardness, and causes modifications in anelasticity, thereby decreasing the elastic modulus. In this study, an alloy was prepared by arc melting precursor metals, heat and mechanically treated, and doped with oxygen, resulting in samples with different processing conditions. In each condition, the alloy was characterised in terms of amount of oxygen, X-ray diffraction, and optical microscopy. In addition, properties of the alloy, such as hardness and elastic modulus, were analysed.

Effects in mechanical properties and structure of the soil tillage with rotary paraplow

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effects in mechanical properties and structure of the soil after tillage with rotary paraplow

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Relationship between elastic and mechanical properties of dental ceramics and their index of brittleness

The purpose of the study was to verify the effects of a number of materials' parameters (crystalline content; Young's modulus, E; biaxial flexure strength, sigma(i); Vickers hardness, VH; fracture toughness, K-Ic; fracture surface energy, gamma(f); and index of brittleness, B) on the brittleness of dental ceramics. Five commercial dental ceramics with different contents of glass phase and crystalline particles were studied: a vitreous porcelain (VM7/V), a porcelain with 16 vol% leucite particles (d.Sign/D), a glass-ceramic with 29 vol% leucite particles (Empress/E1), a glass-ceramic with 58 vol% lithium-disilicate needle-like particles (Empress 2/E2), and a glass-infiltrated alumina composite with 65 vol% crystals (In-Ceram Alumina/IC). Discs were constructed according to manufacturers' instructions, ground and polished to final dimensions (12 mm x 1.1 mm). Elastic constants were determined by ultrasonic pulse-echo method. sigma(i) was determined by piston-on-3-balls method in inert condition. VH was determined using 19.6 N load and K-Ic was determined by indentation strength method. gamma(f) was calculated from the Griffith-Irwin relation and B by the ratio of HV to K-Ic. IC and E2 showed higher values of sigma(i), E, K-Ic and gamma(f), and lower values of B compared to leucite-based glass-ceramic and porcelains. Positive correlations were observed for sigma(i) versus K-Ic, and K-Ic versus E-1/2, however, E did not show relationship with HV and B. The increase of crystalline phase content is beneficial to decrease the brittleness of dental ceramics by means of both an increase in fracture surface energy and a lowering in index of brittleness. (C) 2012 Elsevier Ltd and Techna Group Sri. All rights reserved.

Effects of curing protocol and storage time on the micro-hardness of resin cements used to lute fiber-reinforced resin posts

Objectives: To determine the micro-hardness profile of two dual cure resin cements (RelyX - U100 (R), 3M-ESPE and Panavia F 2.0 (R), Kuraray) used for cementing fiber-reinforced resin posts (Fibrekor (R) - Jeneric Pentron) under three different curing protocols and two water storage times. Material and methods: Sixty 16mm long bovine incisor roots were endodontically treated and prepared for cementation of the Fibrekor posts. The cements were mixed as instructed, dispensed in the canal, the posts were seated and the curing performed as follows: a) no light activation; b) light-activation immediately after seating the post, and; c) light-activation delayed 5 minutes after seating the post. The teeth were stored in water and retrieved for analysis after 7 days and 3 months. The roots were longitudinally sectioned and the microhardness was determined at the cervical, middle and apical regions along the cement line. The data was analyzed by the three-way ANOVA test (curing mode, storage time and thirds) for each cement. The Tukey test was used for the post-hoc analysis. Results: Light-activation resulted in a significant increase in the microhardness. This was more evident for the cervical region and for the Panavia cement. Storage in water for 3 months caused a reduction of the micro-hardness for both cements. The U100 cement showed less variation in the micro-hardness regardless of the curing protocol and storage time. Conclusions: The micro-hardness of the cements was affected by the curing and storage variables and were material-dependent.

Influence of the relative amounts of crystalline and amorphous phases on the mechanical properties of polyamide-6 nanocomposites

The relative amounts of amorphous and crystalline ?- and a-phases in polyamide-6 nanocomposites, estimated from the deconvolution of X-ray diffraction peaks using Gaussian functions, correlates with their mechanical, thermomechanical, and barrier properties. The incorporation of organoclay platelets (Cloisite 15A and 30B) induced the crystallization of the polymer in the ? form at expense of the amorphous phase, such that 12 wt % of Cloisite is enough to enhance the mechanical and the thermomechanical properties. However, higher nanofiller loads were necessary to achieve good barrier effects, because this property is mainly dependent on the tortuous path permeation mechanism of the gas molecules through the nanocomposite films. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Influence of the substitutional solute on the mechanical properties of Ti-Nb binary alloys for biomedical use

Titanium alloys are widely used in the manufacture of biomedical implants because they possess an excellent combination of physical properties and outstanding biocompatibility. Today, the most widely used alloy is Ti-6Al-4V, but some studies have reported adverse effects with the long-term presence of Al and V in the body, without mentioning that the elasticity modulus value of this alloy is far superior to the bone. Thus, there is a need to develop new Ti-based alloys without Al and V that have a lower modulus, greater biocompatibility, and similar mechanical strength. In this paper, we investigated the effect of Nb as a substitutional solute on the mechanical properties of Ti-Nb alloys, prepared in an arc-melting furnace and characterized by density, X-ray diffraction, optical microscopy, hardness and elasticity modulus measurements. The X-ray and microscopy measurements show a predominance of the α phase. The microhardness values showed a tendency to increase with the concentration of niobium in the alloy. Regarding the elasticity modulus, it was observed a nonlinear behavior with respect to the concentration of niobium. This behavior is associated with the presence of the α phase.

How low-level laser therapy can change mechanical properties of cells.

Low level laser therapy is used as a treatment of several conditions, including inflammatory processes and wound healing. Possible changes in mechanical properties of cells, caused by illumination, are investigated with optical magnetic twisting cytometry (OMTC), which is a technique used to evaluate mechanical properties in cell culture. Ferromagnetic micro beads are bound to cell cytoskeleton, the beads are magnetized vertically and a horizontal twisting magnetic field is applied causing a torque that moves the beads and deforms the cell, the beads rotate and displace. Based on the lateral displacement of the beads, elastic shear and loss moduli are obtained. Samples of human bronchial epithelial cell culture were divided in two groups: one was illuminated with a 660 nm red laser, 30 mW power, 0.75 W/cm2 irradiance, during different time intervals, and the other one, the control group, was not illuminated. The values of the mechanical constants of the cells of the control group showed a tendency of increasing with the time out of the incubator. On the other hand, the illuminated group showed constancy on the behavior of both moduli, keeping the normal conditions of the cell culture. Those results indicate that illumination can induce cells to homeostasis, and OMTC is sensitive to observe departures from the steady conditions. Hence, OMTC is an important technique which can be used to aggregate knowledge on the light effect in cell cytoskeleton and even on the low level laser therapy mechanisms in inflammatory processes and/or wound healing.

How low-level laser therapy can change mechanical properties of cells.

Low level laser therapy is used as a treatment of several conditions, including inflammatory processes and wound healing. Possible changes in mechanical properties of cells, caused by illumination, are investigated with optical magnetic twisting cytometry (OMTC), which is a technique used to evaluate mechanical properties in cell culture. Ferromagnetic micro beads are bound to cell cytoskeleton, the beads are magnetized vertically and a horizontal twisting magnetic field is applied causing a torque that moves the beads and deforms the cell, the beads rotate and displace. Based on the lateral displacement of the beads, elastic shear and loss moduli are obtained. Samples of human bronchial epithelial cell culture were divided in two groups: one was illuminated with a 660 nm red laser, 30 mW power, 0.75 W/cm2 irradiance, during different time intervals, and the other one, the control group, was not illuminated. The values of the mechanical constants of the cells of the control group showed a tendency of increasing with the time out of the incubator. On the other hand, the illuminated group showed constancy on the behavior of both moduli, keeping the normal conditions of the cell culture. Those results indicate that illumination can induce cells to homeostasis, and OMTC is sensitive to observe departures from the steady conditions. Hence, OMTC is an important technique which can be used to aggregate knowledge on the light effect in cell cytoskeleton and even on the low level laser therapy mechanisms in inflammatory processes and/or wound healing.

Experimental analysis of fiber reinforced cementitious matrix (FRCM) confined masonry columns

The increasing use of Fiber Reinforced methods for strengthening existing brick masonry walls and columns, especially for the rehabilitation of historical buildings, has generated considerable research interest in understanding the failure mechanism in such systems. This dissertation is aimed to provide a basic understanding of the behavior of solid brick masonry walls unwrapped and wrapped with Fiber Reinforced Cementitious Matrix Composites. This is a new type of composite material, commonly known as FRCM, featuring a cementitious inorganic matrix (binder) instead of the more common epoxy one. The influence of the FRCM-reinforcement on the load-carrying capacity and strain distribution during compression test will be investigated using a full-field optical technique known as Digital Image Correlation. Compression test were carried on 6 clay bricks columns and on 7 clay brick walls in three different configuration, casted using bricks scaled respect the first one with a ratio 1:2, in order to determinate the effects of FRCM reinforcement. The goal of the experimental program is to understand how the behavior of brick masonry will be improved by the FRCM-wrapping. The results indicate that there is an arching action zone represented in the form of a parabola with a varying shape according to the used configuration. The area under the parabolas is considered as ineffectively confined. The effectively confined area is assumed to occur within the region where the arching action had been fully developed.