RESUMO
In this article, the degradability by Aspergillus niger and Aspergillus clavatus of three bio-based polyurethane (PU) foams is compared to previous degradability studies involving a Pseudomonas sp. bacterium and similar initial materials (Spontón et al. in Int. Biodet. Biodeg. 85:85-94, 2013, https://doi.org/10.1016/j.ibiod.2013.05.019 ). First, three new polyester-polyurethane foams were prepared from mixtures of castor oil (CO), maleated castor oil (MACO), toluene diisocyanate (TDI), and water. Then, their degradation tests were carried out in an aqueous medium, and employing the two mentioned fungi, after their isolation from the environment. From the degradation tests, the following was observed: (a) the insoluble (and slightly collapsed) foams exhibited free hydroxyl, carboxyl, and amine moieties; and (b) the water soluble (and low molar mass) compounds contained amines, carboxylic acids, and glycerol. The most degraded foam contained the highest amount of MACO, and therefore the highest concentration of hydrolytic bonds. A basic biodegradation mechanism was proposed that involves hydrolysis and oxidation reactions.
Assuntos
Aspergillus , Poliésteres , Poliuretanos , Poliuretanos/química , Poliuretanos/metabolismo , Poliésteres/metabolismo , Aspergillus niger/metabolismo , Óleo de Rícino/química , ÁguaRESUMO
Resumo Este trabalho avaliou a padronização da força inicial liberada por elásticos ortodônticos em cadeia em diferentes lotes de fabricação de três marcas comerciais. Foram testadas 762 amostras de elásticos em cadeia incolores, tamanho médio, das marcas Morelli®, Uniden® e Eurodonto®. Os elásticos foram distribuídos em 6 diferentes grupos: Grupo M (Morelli), Grupo U (Uniden) e Grupo E (Eurodonto), com 2 lotes para cada grupo. Os elásticos foram mantidos em um "jig" de acrílico de 07 X 07 cm que foi fixado em uma base de madeira de 55 X 15 cm. Os elásticos foram ativados em 50% de seus comprimentos iniciais e as forças iniciais liberadas foram mensuradas através de um dinamômetro digital de precisão. Foram utilizados os testes de Kolmogorov-Smirnov e "t" de Student com 5% de significância para ambos os testes. Os resultados evidenciaram diferença significativa entre a força inicial média liberada de 336,84g e 270,72g dos lotes 1 e 2, respectivamente, da marca U. Não houve diferença significativa entre os lotes da marca M apresentando força inicial média de 310,31g e 312,77g e da marca E com forças iniciais médias de 378,42 e 377,91. Os grupos M,U e E apresentaram os percentuais de 8,7%, 4,3% e 11,4%, respectivamente, de amostras elásticas liberando força inicial considerada padronizada. Pode-se concluir que as marcas Morelli® e Eurodonto® apresentaram força inicial padronizada quando variações entre os lotes foram investigadas. Porém, todas as marcas comerciais apresentaram percentual muito baixo de amostras elásticas com força inicial padronizada, considerando o intervalo de confiança (AU)
Abstract This study evaluated the standardization of the initial strength delivered by elastomeric chains of different lots of fabrication of three commercial brands. 762 colorless middle size samples of elastomeric chains were tested of the brands Morelli®, Uniden® and Eurodonto®. The elastics were distributed in 6 different groups: Group M (Morelli), Group U (Uniden) and Group E (Eurodonto), with 2 lots for each group. The elastics were maintained in a "jig" of 07 x 07 cm acrylic one that was fixed in a 55 X 15 cm wooden base. The elastics were activated in 50% of his initial lengths and the released inicial force was measured through a digital precision dynamometer. Kolmogorov-Smirnov tests were used and Student "t" test with 5% of significantion for both tests. The results showed significant difference between the mean initial released force of 336.84g and 270.72g of lots 1 and 2, respectively, of brand U. There was no significant difference between lots of brand M presenting average initial force of 310.31g and 312.77g and brand E with initial forces of 378.42 and 377.91. Groups M, U and E presented the percentages of 8.7%, 4.3% and 11.4%, respectively, of elastic samples releasing initial strength considered standardized. It can be concluded that the Morelli® and Eurodonto® brands showed standardized initial strength when variations between lots were investigated. However, all commercial brands had a very low percentage of elastic samples with standardized initial strength, considering the confidence interval (AU)
Assuntos
Ortodontia Corretiva , Poliuretanos , ElastômerosRESUMO
The increasing morbidity and mortality of patients due to post-surgery complications of coronary artery bypass grafts (CABPG) are related to blood-material interactions. Thus, the characterization of the thrombogenicity of the biomaterial for cardiovascular devices is of particular interest. This research evaluated the anti-thrombogenic activity of polyurethanes-starch composites. We previously synthesized polyurethane matrices that were obtained from polycaprolactone diol (PCL), polyethylene glycol (PEG), pentaerythritol (PE), and isophorone diisocyanate (IPDI). In addition, potato starch (AL-N) and zwitterionic starch (AL-Z) were added as fillers. The anti-thrombogenic property was characterized by the clot formation time, platelet adhesion, protein absorption, TAT complex levels, and hemolysis. Additionally, we evaluated the cell viability of the endothelial and smooth muscle cells. Statically significant differences among the polyurethane matrices (P1, P2, and P3) were found for protein absorption and the blood clotting time without fillers. The polyurethanes composites with AL-Z presented an improvement in the anti-thrombogenic property. On the other hand, the composites with AL-Z reduced the viability of the endothelial cells and did not significantly affect the AoSCM (except for P1, which increased). These results classify these biomaterials as inert; therefore, they can be used for cardiovascular applications.
RESUMO
PURPOSE: This study compared the mechanical behavior of two fixation techniques used in three sections representing the sagittal split ramus osteotomy (SSRO) in polyurethane replicas that were divided into groups, according to type of section, and sub-groups according to type of fixation, simulating 11-mm advancement and 6º clockwise mandibular rotation. METHODS: Loads were applied in two regions, aiming at progressive application and consequent strength value, measured in kilogram-force in displacements of 1, 3, 5, and 7 mm, from the load application tip. Shapiro-Wilk test was performed, followed by two-way analysis of variance (ANOVA-2 way), and Bonferroni's multiple comparison. RESULTS: The results showed no statistically significant difference in the type of section and type of fixation used when load was applied to the inter-incisor region. However, when load was applied to the first molar region, statistically significant difference was observed in 1-mm displacement, in which section described by Epker with two modifications showed greater strength, regardless of type of fixation used (p = 0.007). CONCLUSION: In the application of load in the inter-incisor region, there was no statistical difference between the type of osteotomy and the type of fixation used. When applying loads to molars, there was a difference for the type of osteotomy, where the Epker osteotomy with 2 modifications presented greater resistance, regardless of the type of fixation used.
Assuntos
Placas Ósseas , Osteotomia Sagital do Ramo Mandibular , Humanos , Osteotomia Sagital do Ramo Mandibular/métodos , Parafusos Ósseos , Fenômenos Biomecânicos , Modelos Anatômicos , Mandíbula/cirurgiaRESUMO
O objetivo do presente estudo in vitro é investigar possíveis alterações nas propriedades mecânicas de alinhadores transparentes de poliuretano (PU). Em um estudo piloto, amostras de alinhadores foram submetidas à Espectroscopia Raman antes e depois de irradiações de UV e de LED, e os resultados demonstraram evidente alteração da estrutura molecular. Em virtude disso, foi levantada a hipótese de que as radiações também provoquem alterações nas propriedades mecânicas. Foram confeccionados trinta alinhadores, pela empresa Align Technology Inc. (Invisalign ®), distribuídos em três grupos de dez alinhadores cada. Um grupo controle não sofreu irradiação, e os outros dois grupos foram irradiados: um com radiação UV dentro de uma câmara construída para esse tipo de experimento e um terceiro grupo com radiação LED por fotopolimerizador específico. Os grupos foram definidos, as irradiações foram efetuadas sob sigilo por um operador e as identificações, armazenadas em envelopes lacrados, somente foram reveladas após a conclusão dos testes e tabulação dos dados obtidos. Para avaliação das propriedades mecânicas, neste caso resistência à deformação, utilizou-se uma máquina de ensaio universal para o teste de carga. Os alinhadores foram preenchidos com gesso, com um alívio que deixou livres as áreas a serem testadas. O teste de tensão mostrou que tendo como referência o grupo controle, os alinhadores submetidos à radiação UV tornaram-se menos rígidos e os submetidos à radiação LED tornaram-se mais rígidos. O teste de H de Kruskal-Wallis foi realizado e evidenciou não haver diferença estatisticamente significativa na carga aplicada nas amostras dos diferentes grupos. O mesmo teste foi utilizado para avaliar a diferença entre a deformação ocorrida e o módulo de elasticidade nos três grupos. A hipótese nula foi rejeitada em ambos os testes, considerando o nível de 5% de significância, o que assegura que há uma diferença significativa entre os três grupos quanto à irradiação de UV ou LED. Ainda assim, para uma avaliação mais minuciosa utilizou-se o teste de Mann-Whtiney comparando os grupos dois a dois. O resultado apontou que as irradiações aplicadas neste estudo são responsáveis pelas diferenças estatísticas apresentadas. (AU)
The aim of the present in vitro study is to investigate possible changes in the mechanical properties of transparent polyurethane (PU) aligners. In a pilot study, specimens of aligners were subjected to Raman Spectroscopy before and after UV and LED irradiation, and the results showed evident alteration of the molecular structure. Because of this, it was hypothesized that the radiations also cause changes in the mechanical properties. Thirty aligners were made by Align Technology Inc. (Invisalign®), distributed in three groups of ten aligners each. A control group was not irradiated, and the other two groups were irradiated: one with UV radiation inside a chamber built for this type of experiment, and the third group with LED radiation by a specific photopolymerizer. The groups were defined, the irradiations were done under confidentiality by an operator and the identifications, stored in sealed envelopes, were only revealed after the completion of the tests and tabulation of the data obtained. To evaluate the mechanical properties, in this case resistance to deformation, a universal testing machine was used for the load test. The aligners were filled with plaster, with a relief that left free the areas to be tested. The tension test showed that taking the control group as reference, the aligners submitted to UV radiation became less rigid and those submitted to LED radiation became more rigid. The Kruskal-Wallis H test was performed and showed that there was no statistically significant difference in the load applied to the samples of the different groups. The same test was used to evaluate the difference between the deformation occurred and the modulus of elasticity in the three groups. The null hypothesis was rejected in both tests, considering the 5% significance level, which ensures that there is a significant difference between the three groups regarding UV or LED irradiation. Even so, for a more detailed evaluation the Mann-Whtiney test was used, comparing the groups two by two. The result pointed out that the irradiations applied in this study are responsible for the statistical differences presented (AU)
Assuntos
Aparelhos Ortodônticos Removíveis , Poliuretanos , Análise Espectral Raman , Radiação , Raios Ultravioleta , Testes MecânicosRESUMO
Several efforts have been dedicated to the development of lignin-based polyurethanes (PU) in recent years. The low and heterogeneous reactivity of lignin hydroxyl groups towards diisocyanates, arising from their highly complex chemical structure, limits the application of this biopolymer in PU synthesis. Besides the well-known differences in the reactivity of aliphatic and aromatic hydroxyl groups, experimental work in which the reactivity of both types of hydroxyl, especially the aromatic ones present in syringyl (S-unit), guaiacyl (G-unit), and p-hydroxyphenyl (H-unit) building units are considered and compared, is still lacking in the literature. In this work, the hydroxyl reactivity of two kraft lignin grades towards 4,4'-diphenylmethane diisocyanate (MDI) was investigated. 31P NMR allowed the monitoring of the reactivity of each hydroxyl group in the lignin structure. FTIR spectra revealed the evolution of peaks related to hydroxyl consumption and urethane formation. These results might support new PU developments, including the use of unmodified lignin and the synthesis of MDI-functionalized biopolymers or prepolymers.
RESUMO
Bio-derived furan- and diacid-derived cyclic carbonates have been synthesized in high yields from terminal epoxides and CO2 . Furthermore, four highly substituted terpene-derived cyclic carbonates were isolated in good yields with excellent diastereoselectivity in some cases. Eleven new cyclic carbonates derived from 10-undecenoic acid under mild reaction conditions were prepared, providing the corresponding carbonate products in excellent yields. The catalyst system also performed the conversion of an epoxidized fatty acid n-pentyl ester into a cyclic carbonate under relatively mild reaction conditions (80 °C, 20â bar, 24â h). This bis(cyclic carbonate) was obtained in high yields and with different cis/trans ratios depending on the co-catalyst used. An allyl alcohol by-product was only observed as a minor product when bis(triphenylphosphine)iminium chloride was used as co-catalyst. Finally, two cyclic carbonates were used as building blocks for the preparation of non-isocyanate poly(hydroxy)urethanes by reaction with 1,4-diaminobutane.
RESUMO
Purpose The biomechanical properties of the polyurethanes implant material derived from castor oil plant (Ricinus communis) were evaluated in a noncritical bone defect model in rat tibia. Methods After three weeks of the implant application, the tibias were tested by means of the biomechanical three-point flexion test and resistance, rigidity, energy at maximum load and maximum energy were evaluated. Nonparametric statistical analysis was performed. Results It was found that the group that received the implant behaved the same as the intact control group and also showed a significant increase in maximum load compared to the spontaneous repair group. Conclusions Our results indicate that the tibias with the implant material in a noncritical bone defect recover normal biomechanical parameters in less time than spontaneously.(AU)
Assuntos
Animais , Ratos , Ricinus , Fenômenos Biomecânicos , Doenças Ósseas/veterinária , Próteses e Implantes/veterinária , PoliuretanosRESUMO
ABSTRACT Purpose The biomechanical properties of the polyurethanes implant material derived from castor oil plant (Ricinus communis) were evaluated in a noncritical bone defect model in rat tibia. Methods After three weeks of the implant application, the tibias were tested by means of the biomechanical three-point flexion test and resistance, rigidity, energy at maximum load and maximum energy were evaluated. Nonparametric statistical analysis was performed. Results It was found that the group that received the implant behaved the same as the intact control group and also showed a significant increase in maximum load compared to the spontaneous repair group. Conclusions Our results indicate that the tibias with the implant material in a noncritical bone defect recover normal biomechanical parameters in less time than spontaneously.
Assuntos
Animais , Ratos , Próteses e Implantes , Ricinus , Poliuretanos , Tíbia/cirurgiaRESUMO
In the present work, the synthesis of segmented polyurethanes functionalized with catechol moieties within the hard or the soft segment is presented. For this purpose, a synthetic route of a new catechol diol was designed. The direct insertion of this catechol-free derivative into the rigid phase led to segmented polyurethanes with low performance (σmax ≈ 4.5 MPa). Nevertheless, when the derivative was formally located within the soft segment, the mechanical properties of the corresponding functionalized polyurethane improved considerably (σmax ≈ 16.3 MPa), owing to a significant increase in the degree of polymerization. It is proposed that this difference in reactivity could probably be attributed to a hampering effect of this catecholic ring during the polyaddition reaction. To corroborate this hypothesis, a protection of the aromatic ring was carried out, blocking the hampering effect and avoiding secondary reactions. The polyurethane bearing the protected catechol showed the highest molecular weight and the highest stress at break described to date (σmax ≈ 66.1 MPa) for these kind of catechol-functionalized polyurethanes. Therefore, this new approach allows for the obtention of high-performance polyurethane films and can be applied in different sectors, benefiting from the molecular adhesion introduced by the catechol ring.