ABSTRACT
O uso de protetores bucais na prática de esportes tem ampliado espaço no contexto da prevenção de traumas bucais, bem como apresentado melhoria no desempenho ao longo de sua história. O objetivo deste trabalho foi avaliar o comportamento do complexo bucodentoalveolar por meio do método dos elementos finitos. O estudo partiu de um modelo em formato esterolitográfico oriundo de uma tomografia computadorizada, o qual foi convertido para um modelo 3D pelo programa Rhinoceros® versão 4.0, sem protetor bucal (controle) e com protetor bucal de 4,0 mm de espessura em EVA (copolímero de etileno e acetato de vinila), os quais receberam duas cargas diferentes (500, 1000 N) no programa ANSYS® v.12 em regime quase estático e de caráter elástico linear. Pudemos observar que houve um padrão de comportamento das estruturas envolvidas quanto à dissipação das tensões geradas e ao se comparar o modelo controle com o modelo provido de protetor bucal houve uma absorção das tensões geradas em até 50%, permitindo confirmar a ação do protetor bucal em literatura e tornando o seu uso imperativo durante a prática de esportes, em especial as modalidades de maior contato.
The use of mouthguards in the practice of sports has expanded space in the prevention of oral trauma, and has presented performance improvement over its history. The aim of this study was to evaluate the behavior of complex dento alveolar buccal through the finite element method. The study was based on a template stereolitographic format come from a CT scan, which was converted to a 3D model by the program Rhinoceros® version 4.0, without a mouthguard (control) and mouthguard 4.0 mm thick copolymer of ethylene and vinyl acetate (EVA), which received two different loads (500, 1000 N) in ANSYS® v.12 under quasi-static linear and elastic character. We noticed that there was a pattern of behavior of the structures involved about the dissipation of tensions generated, and when the model was compared with the control model fitted with a mouthguard there was an absortion of the stresses generated in up to 50%, allowing to confirm the action of the mouthguard in literature and making its use mandatory for the practice of sports, especially the arrangements for closer contact.
ABSTRACT
The aim of this study was to investigate the water sorption behavior of cellulose II:SiO2 composites and to determine the influence of silicification on this property. These composites were prepared by spray-drying at a cellulose II:SiO2 ratio of 98:2, 95:5, 90:10 and 80:20. The nonlinear models of Guggenheim-Anderson-de Boer (GAB), Generalized D'Arcy and Watt (GDW) and Hailwood & Horrobin (HH), were used for the characterization and analysis of the isotherms. The infrared and powder X-rays characterization showed no signs of chemical modification or change in the polymorphic form of cellulose II by SiO2. The parameters derived from these models indicated that only a 20 percent level of silicification was able to hinder the water sorption properties of cellulose. Silicon dioxide was the most hydrophobic material since it had a lower ability to form hydrogen bonds with water than cellulose II. This finding was reflected in a delayed compact disintegration time when high levels of silicification (20 percent) and compression pressures higher than 120 MPa were used.
O objetivo deste estudo é investigar o comportamento de sorção de água a partir de misturas de celulose II e SiO2 e determinar a influência da silicificação nesse processo. Estas misturas foram preparadas por nebulização (spray-drying) usando misturas de celulose II e SiO2 nas proporções de 98:2, 95:5, 90:10 e 80:20. Os modelos não-lineares de Guggenheim-Anderson-de Boer (GAB), "Generalized" D'Arcy e Watt (GDW) e Hailwood & Horrobin (HH) foram utilizados para caracterização e análise das isotermas. As misturas foram caracterizadas por infravermelho e raio-X e os resultados não mostraram indicativo de modificação química ou polimórfica da celulose II em combinação com SiO2. Os parâmetros derivados desses modelos indicaram que as propriedades de sorção de água da celulose foram prejudicadas apenas quando empregado um nível de silicificação de 20 por cento. O dióxido de silício foi o material mais hidrofóbico, provavelmente por possuir uma menor capacidade de formar pontes de hidrogênio com a água quando comparado com a celulose II. Este resultado foi refletido em redução no tempo de desintegração, especialmente quando altos níveis de silicificação (20 por cento) e força de compressão (acima de 120 Mpa) foram utilizados.
Subject(s)
Water/chemistry , Crystallization , Cellulose/analysis , Cellulose/adverse effects , Silicon Dioxide/adverse effects , Chemical Phenomena , Absorption , Adsorption , Cotton Fiber , Isotherm , Models, ChemicalABSTRACT
The use of an upper endoscope has been considered as a back-up method in case of incomplete caecal intubation. We compared caecal intubation rates between colonoscopic examinations done with a standard colonosope and those in which a standard gastroscope was used, to determine if routine colonosocpies could be performed with gastrocope if no colonoscope is available. A prospective comparative study, analyzing continuous date was designed to evaluate the usefulness of a standard gastroscope in a group of outpatients with indication for colonoscopy in colorectal cancer screening. At total of 170 adult patients were randomly assigned to two similar study groups. All examinations were performed by a single endoscopist. Our primary end point was to achieve caecal intubation. Successful caecal intubation was achieved in 162 patients that fulfilled our inclusion criteria. 83 patients in the colonoscope and 79 in the gastroscope group. Failure of caecal intubation was similar in male and female patients in both groups [p- 0.34]. Caecal intubation failure rates were similar in both study groups. We used the gastroscope as a first line method or routine colonosocpies and found no statistical difference between the colonoscope and gastroscope groups. If these results can be verified in larger mulicenter studies, it may be possible in the future, to work with only one endoscope for both upper and lower digestive tract examinations in small centers, particularly in developing countries