Assessment of force decay in orthodontic elastomeric chains: An in vitro study

Introduction: Elastomeric materials are considered important sources of orthodontic forces. Objective: To assess force degradation over time of four commercially available orthodontic elastomeric chains (Morelli, Ormco, TP and Unitek). Methods: The synthetic elastics were submerged in 37 oC synthetic saliva and stretched by a force of 150 g (15 mm - Morelli and TP; 16mm - Unitek and Ormco). With a dynamometer, the delivered force was evaluated at different intervals: 30 minutes, 7 days, 14 days and 21 days. The results were subjected to ANOVA and Tukey's test. Results: There was a force decay between 19% to 26.67% after 30 minutes, and 36.67% to 57% after 21 days of activation. Conclusions: TP elastomeric chains exhibited the smallest percentage of force decay, with greater stability at all time intervals tested. Meanwhile, the Unitek chains displayed the highest percentage of force degradation, and no statically significant difference was found in force decay between Ormco and Morelli elastomeric chains during the study period.

Estudo da degradação da força gerada por elásticos ortodônticos sintéticos

OBJETIVO: analisar separada e comparativamente cinco marcas comerciais de elásticos sintéticos (Morelli, Ormco, GAC, TP e Unitek) quanto à degradação da força gerada por estes em função do tempo, quando mantidos continuamente estirados em uma distância de 20mm. METODOLOGIA: as leituras das quantidades de força gerada pelos elásticos foram feitas nos intervalos 1/2, 1, 6, 12, 24, 48 horas; 7, 14, 21 e 28 dias. Construiu-se um gráfico de força versus tempo, onde se pôde observar significativa redução na quantidade de força liberada pelos elásticos na primeira hora de ativação. RESULTADOS: verificou-se uma redução na quantidade de força gerada pelos elásticos de 20,31 a 38,47% na primeira hora de testes e de 47,7 a 75,95% em 28 dias de estiramento constante. CONCLUSÕES: concluiu-se que todas as amostras das marcas comerciais estudadas sofreram significativa redução na quantidade de força liberada na primeira hora de ativação e que a média de força gerada em 21 e 28 dias de testes foi semelhante para todas as amostras pesquisadas.

Maximizing the utility of bio-based diisocyanate and chain extenders in crystalline segmented thermoplastic polyester urethanes: effect of polymerization protocol

High molecular weight semi crystalline thermoplastic poly(ester urethanes), TPEUs, were prepared from a vegetable oil-based diisocyanate, aliphatic diol chain extenders and poly(ethylene adipate) macro diol using one-shot, pre-polymer and multi-stage polyaddition methods. The optimized polymerization reaction achieved ultra-high molecular weight TPEUs (>2 million as determined by GPC) in a short time, indicating a very high HPMDI diol reactivity. TPEUs with very well controlled hard segment (HS) and soft segment (SS) blocks were prepared and characterized with DSC, TGA, tensile analysis, and WAXD in order to reveal structure property relationships. A confinement effect that imparts elastomeric properties to otherwise thermoplastic TPEUs was revealed. The confinement extent was found to vary predictably with structure indicating that one can custom engineer tougher polyurethane elastomers by "tuning" soft segment crystallinity with suitable HS block structure. Generally, the HPMDI-based TPEUs exhibited thermal stability and mechanical properties comparable to entirely petroleum-based TPEUs. (C) 2014 Elsevier Ltd. All rights reserved.

Comparison of DNA-extraction methods and Selective Enrichment broths on the detection of Salmonella Typhimurium in swine feces by polymerase chain reaction (PCR)

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

Search for Salmonella spp. in ostrich productive chain of Brazilian southeast region

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

Dependence of the electrical conductivity and elastomeric properties on sample preparation of blends of polyaniline and natural rubber

Blend films (free-standing) containing 20% in volume of polyaniline (PANI) in 80% of natural rubber (NR) were fabricated by casting in three different ways: (1) adding PANI-EB (emeraldine base) dissolved in N-methyl-2-pyrrolidone (NMP) to the latex (NRL), (2) adding PANI-EB dissolved in in-cresol to NR dissolved in xylol (NRD), (3) overlaying the surface of a pure NR cast film with a PANI layer grown by in situ polymerization (NRO). All the films were immersed into HCl solution to achieve the primary doping (protonation) of PANI before the characterization. The main goal here was to investigate the elastomeric and electrical conductivity properties for each blend, which may be applied as pressure and deformation sensors in the future. The characterization was carried out by optical microscopy, dc conductivity, vibrational spectroscopy (infrared absorption and Raman scattering), thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and tensile stress-strain curves. The results suggest that the NRL blend is the most suitable in terms of mechanical and electrical properties required for applications in pressure and deformation sensors: a gain of conductivity without losing the elastomeric property of the rubber. (c) 2005 Wiley Periodicals, Inc.

Plasmid-based controls to detect rpoB mutations in Mycobacterium tuberculosis by quantitative polymerase chain reaction-high-resolution melting

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

Dynamic mechanical properties for polyurethane elastomers applied in elastomeric mortar

Dynamic mechanical properties of a polyurethane (PU) elastomer and a mortar processed with the same elastomer (modified polytetramethylene ether glycol (PTMEG)) were studied. The results obtained showed that the liquid aromatic amine ETHACURE (R) 300, used as cure agent, can be used to substitute the aromatic amine MOCA (R), which is usually used as cure agent in high performance elastomers. The resulting mortar produced with ETHACURE (R) 300 presents similar dynamic-mechanical thermal properties when compared with MOCA (R). However, dynamic-mechanical thermal analysis studies showed that the mortar developed with ETHACURE (R) 300 presents some advantages such as the low values of tan d, indicating a good capacity of recovery of the strain after retreating an applied force. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Variable parameter and double sampling (X)over-bar charts in the presence of correlation: The Markov chain approach

The general assumption under which the (X) over bar chart is designed is that the process mean has a constant in-control value. However, there are situations in which the process mean wanders. When it wanders according to a first-order autoregressive (AR (1)) model, a complex approach involving Markov chains and integral equation methods is used to evaluate the properties of the (X) over bar chart. In this paper, we propose the use of a pure Markov chain approach to study the performance of the (X) over bar chart. The performance of the chat (X) over bar with variable parameters and the (X) over bar with double sampling are compared. (C) 2011 Elsevier B.V. All rights reserved.

Correlation between API 50 CH and multiplex polymerase chain reaction for the identification of vaginal lactobacilli in isolates

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

A polymerase chain reaction for the detection of Brucella canis in semen of naturally infected dogs

The objective was to evaluate a PCR assay for the detection of Brucella canis in canine semen, comparing its performance with that of bacterial isolation, serological tests and PCR assay of blood. Fifty-two male dogs were examined clinically to detect reproductive abnormalities and their serum was tested by the rapid slide agglutination test, with and without 2-mercaptoethanol (2ME-RSAT and RSAT, respectively). In addition, microbiological culture and PCR assays were performed on blood and semen samples. The findings of the semen PCR were compared (Kappa coefficient and McNemar test) to those of blood PCR, culture of blood and semen, RSAT, and 2ME-RSAT. Nucleic acid extracts from semen collected from dogs not infected with B. canis were spiked with decreasing amounts of B. canis RM6/66 DNA and the resulting samples subjected to PCR. In addition, semen samples of non-infected dogs were spiked with decreasing amounts of B. canis CFU and the resulting suspensions were used for DNA extraction and amplification. of the 52 dogs that were examined, the following tests were positive: RSAT, 16 (30.7%); 2ME-RSAT, 5 (9.6%); blood culture, 14 (26.9%); semen culture, 11 (21.1%); blood PCR, 18 (34.6%); semen PCR, 18 (34.6%). The PCR assay detected as few as 3.8 fg of B. canis DNA experimentally diluted in 444.9 ng of canine DNA (extracted from semen samples of noninfected dogs). In addition, the PCR assay amplified B. canis genetic sequences from semen samples containing as little as 1.0 x 10(0) cfu/mL. We concluded that PCR assay of semen was a good candidate as a confirmatory test for the diagnosis of brucellosis in dogs; its diagnostic performance was similar to blood culture or blood PCR. Furthermore, the PCR assay of semen was more sensitive than the 2ME-RSAT or semen culture. Examination of semen by PCR should be included for diagnosis of brucellosis prior to natural mating or AI; in that regard, some dogs that were negative on serological and microbiological examinations as well as blood PCR were positive on PCR of semen. (c) 2007 Elsevier B.V. All rights reserved.

A polymerase chain reaction for detection of Brucella canis in vaginal swabs of naturally infected bitches

A PCR assay for the detection of Brucella canis in canine vaginal swab samples was evaluated, comparing its performance with that of bacterial isolation, serological tests, and a blood PCR assay. One hundred and forty-four female dogs were clinically examined to detect reproductive problems and they were tested by the rapid slide agglutination test, with and without 2-mercaptoethanol (2ME-RSAT and RSAT, respectively). In addition, microbiological culture and PCR were performed on blood and vaginal swab samples. The results of the vaginal swab PCR were compared to those of the other tests using the Kappa coefficient and McNemar test. of the 144 females that were examined, 66 (45.8%) were RSAT positive, 23 (15.9%) were 2ME-RSAT positive, 49 (34.02%) were blood culture positive, 6 (4.1%) were vaginal swab culture positive, 54 (37.5%) were blood PCR positive, 52 (36.2%) were vaginal swab PCR positive, and 50.69% (73/144) were positive by the combined PCR. The PCR was able to detect as few as 3.8 fg of B. canis DNA experimentally diluted in 54 ng of canine DNA, extracted from vaginal swab samples of non-infected bitches. In addition, the PCR assay amplified B. canis genetic sequences from vaginal swab samples containing 1.0 x 10(0) cfu/mL. In conclusion, vaginal swab PCR was a good candidate as a confirmatory test for brucellosis diagnosis in bitches suspected to be infected, especially those negative on blood culture or blood PCR; these animals may be important reservoirs of infection and could complicate attempts to eradicate the disease in confined populations. (C) 2007 Elsevier B.V. All rights reserved.

Adaptation and evaluation of polymerase chain reaction for Brucella ovis detection in semen, urine and organs of rams experimentally infected

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