Effects of pigment, disinfection, and accelerated aging on the hardness and deterioration of a facial silicone elastomer

The failure of facial prostheses is caused by limitations in their flexibility and durability. Therefore, we evaluated the effects of disinfection and aging on Shore A hardness and deterioration of a facial silicone with different pigmentations. Twenty samples with addition of each pigment (ceramic (C), make-up (M)) and without pigment (L) were made. For each pigment type and no pigment, 10 samples were subjected to two types of disinfectant solution (soap (S) and Efferdent (E)), totaling sixty samples. The specimens were disinfected three times per week for 60 days, and subjected to accelerated aging for 1008 h. The hardness of the facial silicone was measured with a durometer, and its deterioration was evaluated by obtaining the weight difference over time. Both the hardness and weight of the samples were measured at baseline, after chemical disinfection, and periodically during accelerated aging (252, 504, and 1008 h). Deterioration was calculated during the periods between baseline and chemical disinfection, and between baseline and each aging period. The results were analyzed using three-way repeated measures ANOVA and the Tukey's HSD Post-hoc test (alpha = 0.05). Specifically, samples containing pigment exhibited significantly higher hardness and deterioration values than those lacking pigment (P < 0.05). In addition, period of time (disinfection and accelerated aging) statistically increased the hardness and deterioration values of the silicone (P < 0.05). It can be concluded that both pigment and time statistically affected the hardness and deterioration of the silicone elastomer. (c) 2012 Elsevier Ltd. All rights reserved.

Chromatic stability of acrylic resins of artificial eyes submitted to accelerated aging and polishing

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evaluation of the Shore A Hardness of Silicone for Facial Prosthesis as to the Effect of Storage Period and Chemical Disinfection

The failure of facial prostheses is caused by limitations in the properties of existing materials, especially flexibility and durability. Therefore, this study evaluated the Shore A hardness of silicone used for fabrication of facial prostheses, Silastic MDX4-4210, according to the influence of storage period, daily disinfection, and 2 types of pigmentation. Thirty specimens were fabricated and divided in 3 groups: colorless, pigmented with makeup, and pigmented with iron oxide. Analysis of results was assessed on a Shore A hardness meter immediately, 6 months, and 1 year after fabrication of specimens, following the guidelines of the American Society for Testing and Materials. The hardness values were statistically analyzed by the Tukey test. The silicone exhibited an increase in hardness with time. However, the hardness was stable from 6 months to 1 year. It was concluded that the silicone is within the values of Shore A hardness reported in the literature, regardless of the storage period, pigmentation, and chemical disinfection.

Aortic aneurysm surgery: problems and innovations

Um longo caminho foi percorrido desde as primeiras intervenções cirúrgicas feitas para o tratamento do aneurisma de aorta abdominal. Ao longo deste tempo, várias inovações foram criadas, no sentido de reduzir a invasividade dos procedimentos e melhorar sua segurança e durabilidade. Nesta revisão, são discutidos os principais e recentes avanços em intervenções sobre aneurismas aórticos, incluindo a restauração aórtica endovascular, a cirurgia aórtica videolaparoscópica, as técnicas híbridas convencionais e endovasculares, as técnicas combinadas videolaparoscópicas e endovasculares, bem como as perspectivas futuras, tanto para aorta torácica como abdominal. Diante de tantas transformações e evolução, o cirurgião vascular moderno terá que ter sua mente aberta para as novidades e desenvolver capacitação ampla com diferentes técnicas para proporcionar a melhor opção terapêutica para seus pacientes.

Ceramic materials in dentistry: historical evolution and current practice

Dental ceramics are presented within a simplifying framework allowing for facile understanding of their development, composition and indications. Engineering assessments of clinical function are dealt with and literature is reviewed on the clinical behaviour of all-ceramic systems. Practical aspects are presented regarding the choice and use of dental ceramics to maximize aesthetics and durability, emphasizing what we know and how we know it.

Associational life and local development in two Nicaraguan villages

Includes bibliography

Effect of different disinfectants on the microhardness and roughness of acrylic resins for ocular prosthesis

Background: Ocular prosthesis materials should have specific properties for their indication and durability; therefore, it is important to investigate their physical behaviour when affected by several disinfectants. Objectives: This study evaluated the influence of different disinfecting solutions on the microhardness and surface roughness of acrylic resins for ocular prosthesis. Materials and Methods: Fifty samples simulating ocular prostheses were fabricated with N1 resin and colourless resin and divided (n = 10) according to the disinfectant used: neutral soap, Opti-free, Efferdent, 1% hypochlorite (HYC) and 4% chlorhexidine (CHX). Samples were stored in saline solution at 37°C and disinfected during 120 days. Both microhardness and roughness were investigated before, after 60 days and 120 days of disinfection and storage. Microhardness was measured using a microhardner and the roughness with a roughness device. Results: N1 resin showed lower microhardness when compared with colourless resin (p < 0.05). HYC and CHX groups exhibited the highest change of microhardness and roughness values (p < 0.05). An increase in roughness and reduction in microhardness of ocular acrylic resins were observed after both periods of disinfection and storage (p < 0.05). Conclusion: Both disinfection/storage periods affected the microhardness and roughness values of the samples. © 2012 The Gerodontology Society and John Wiley & Sons A/S.

Clinical Satisfaction and Quality of Ceramic Fixed Dentures

It is known that several factors can affect the clinical success and durability of fixed partial dentures. Therefore, the aim of the present study was to present a literature review about the longevity, clinical success, and quality, as well as, patients' and dental surgeons' satisfaction of ceramic fixed dentures. High rate of patients' satisfaction has been observed in relation to the esthetic of ceramic crowns. In addition, the literature has shown that dental ceramics can be used in several clinical situations with high success rate and longevity. Despite of failures and complications of ceramic restorations, nowadays, with the improvement of mechanical properties of such materials, ceramic crowns present a favorable prognosis and can be used in several clinical situations with high success rate, clinical quality, and great patients' satisfaction. © 2013 The American Ceramic Society.

Social cohesion: inclusion and a sense of belonging in Latin America and the Caribbean. Summary

Includes bibliography

Impact strength and abrasion resistance of high strength concrete with rice husk ash and rubber tires

The paper discusses the application of High Strength Concrete (HSC) technology for concrete production with the incorporation of Rice Husk Ash (RHA) residues by replacing a bulk of the material caking and rubber tires with partial aggregate volume, assessing their influence on the mechanical properties and durability. For concrete with RHA and rubber, it was possible to reduce the brittleness by increasing the energy absorbing capacity. With respect to abrasion, the RHA and rubber concretes showed lower mass loss than the concrete without residues, indicating that this material is attractive to be used in paving. It is thus hoped that these residues may represent a technological and ecological alternative for the production of concrete in construction works.

Vibration Control Applied in a Semi-Active Suspension using Magneto Rheological Damper and Optimal Linear Control Design

In this paper we study the behavior of a semi-active suspension witch external vibrations. The mathematical model is proposed coupled to a magneto rheological (MR) damper. The goal of this work is stabilize of the external vibration that affect the comfort and durability an vehicle, to control these vibrations we propose the combination of two control strategies, the optimal linear control and the magneto rheological (MR) damper. The optimal linear control is a linear feedback control problem for nonlinear systems, under the optimal control theory viewpoint We also developed the optimal linear control design with the scope in to reducing the external vibrating of the nonlinear systems in a stable point. Here, we discuss the conditions that allow us to the linear optimal control for this kind of non-linear system.

Analysing the fate of nanopesticides in soil and the applicability of regulatory protocols using a polymer-based nanoformulation of atrazine

For the first time, regulatory protocols defined in the OECD guidelines were applied to determine the fate properties of a nanopesticide in two agricultural soils with contrasting characteristics. The nanoformulation studied had no effect on the degradation kinetics of atrazine indicating that (1) the release of atrazine from the polymer nanocarriers occurred rapidly relative to the degradation kinetics (half-lives 36-53 days) and/or that (2) atrazine associated with the nanocarriers was subject to biotic or abiotic degradation. Sorption coefficients, derived from a batch and a centrifugation technique at a realistic soil-to-solution ratio, were higher for the nanoformulated atrazine than for the pure active ingredient. Results indicate that the nanoformulation had an effect on the fate of atrazine. However, since the protocols applied were designed to assess solutes, conclusions about the transport of atrazine loaded onto the nanocarriers should be made extremely cautiously. The centrifugation method applied over time (here over 7 days) appears to be a useful tool to indirectly assess the durability of nanopesticides under realistic soil-to-solution ratios and estimate the period of time during which an influence on the fate of the active ingredient may be expected. More detailed investigations into the bioavailability and durability of nanopesticides are necessary and will require the development of novel methods suitable to address both the "nano" and "organic" characteristics of polymer-based nanopesticides.

Non-conventional cement-based composites reinforced with vegetable fibers: a review of strategies to improve durability

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

Chromatic stability of acrylic resins of artificial eyes submitted to the accelerated aging and polishing

Esthetics and durability of materials used to fabricate artificial eyes has been an important issue since artificial eyes are essential to restore esthetics and function, protect the remaining tissues and help with patients' psychological therapy. However, these materials are submitted to degrading effects of environmental agents on the physical properties of the acrylic resin. OBJECTIVE: This study assessed the color stability of acrylic resins used to fabricate sclera in three basic shades (N1, N2 and N3) when subjected to accelerated aging, mechanical and chemical polishing. MATERIAL AND METHODS: Specimens of each resin were fabricated and submitted to mechanical and chemical polishing. Chromatic analysis was performed before and after accelerated aging through ultraviolet reflection spectrophotometry. RESULTS: All specimens revealed color alteration following polishing and accelerated aging. The resins presented statistically significant chromatic alteration (p<0.01) between the periods of 252 and 1008 h. CONCLUSIONS: Both polishing methods presented no significant difference between the values of color derivatives of resins.

Marginal deterioration of the silicone for facial prosthesis with pigments after effect of storage period and chemical disinfection

The failure of facial prostheses is caused by limitations in the properties of existing materials, especially flexibility and durability. Therefore, this study evaluated the marginal deterioration of a silicone used for fabrication of facial prostheses (Silastic MDX4-4210, Dow Corning Corporation, Midland, MI, USA) according to the influence of artificial aging, daily disinfection, and 2 types of pigmentation. Thirty specimens were fabricated and subdivided in 6 groups: without pigmentation, pigmented with make-up powder and iron oxide, and evaluated with and without the action of the disinfectant. Analysis of marginal deterioration was performed on a scanning electron microscope (magnification, ×5000) immediately 6 months and 1 year after fabrication of specimens, following the guidelines of ASTM International. After visual analysis of the photomicrographs, it was noticed that all groups presented marginal deterioration and alterations in surface texture with time. The use of disinfection did not contribute to the marginal deterioration of polymer (silicone), regardless of the pigmentation and artificial aging.