In vitro comparison of the force degradation of orthodontic intraoral elastics from different compositions

The synthetic intermaxillary elastic emerged as an alternative for clinical use in patients with latex sensitivity. However, there are disagreements about this elastic protocol use according to the force degradation. The aim of this study was to evaluate, in vitro, the forces generated by latex and synthetic elastics over time. Material and methods: Sample size of 840 elastics were used (420 latex and 420 synthetic), delivering medium strength (Dental Morelli®) with internal diameter of 1/8", 3/16", 1/4" and 5/16". The elastics were randomly divided into 7 groups according to the time of the force measuring and immersed into distilled water at 37°C. To measure the force in each group, the elastics were stretched in six progressive increases of 100% of its internal diameter with the aid of a testing machine Emic and measured up to 72 hours. Data were analyzed with SPSS 16.0, using one-way analysis of variance (ANOVA). Results: Immediate force level of synthetic elastics was statistically higher than latex elastics in all strains, for the same size. However, the latex elastics mean forceslightly decreased over time, while the synthetic elastics presented an abrupt decrease. Conclusion: In view of these findings, Sudanese homemade alcoholic beverages cause oral epithelial atypical changes, which lead to oral precancerous and cancerous lesions. OEFC is a useful procedure for detection and assessment of oral ET.

Avaliação dos elásticos ortodônticos intra-orais de látex e de borracha sintética: estudo in vitro e in vivo

Os elásticos ortodônticos intermaxilares sintéticos vem sendo cada vez mais utilizados, sendo principalmente indicados para pacientes que apresentam hiper-sensibilidade ao látex. Afim de avaliar e comparar o comportamento de elásticos de látex e sintéticos quanto a perda de força ao longo do tempo, este estudo foi realizado tanto in vitro quanto in vivo. Para o estudo in vitro foram avaliados 15 elásticos de cada material, para cada tempo: 0, 1, 3, 12 e 24 horas. No estudo in vivo, pacientes foram avaliados (N=15), utilizando elásticos de ambos os materiais (látex e sintético), nos mesmos tempos do estudo in vitro. Os elásticos foram transferidos para a máquina de ensaios mecânicos (EMIC DL-500 MF). Os valores da força gerada foram registrados após a distensão dos elásticos a uma distância de 25mm. Foi aplicado o teste t pareado para a amostra clínica e independente para a amostra laboratorial. Foi utilizada a análise de variância (ANOVA) para verificar a variação das forças geradas entre os tempos determinados e o teste post-hoc para identificar entre quais tempos houve diferença significativa. Quanto às forças iniciais geradas (zero hora), os valores para os elásticos sintéticos foram bastante semelhantes entre os estudos laboratorial e clínico e ligeiramente superiores aos dos elásticos de látex. Nos tempos subsequentes, as forças geradas pelos elásticos de látex apresentaram valores superiores. Em relação à degradação do material, ao final de 24 horas, maior percentual foi observado para os elásticos sintéticos, tanto in vitro quanto in vivo. A maior queda nos valores das forças liberadas pelos elásticos de ambos os materiais e nos estudos clínico e laboratorial, ocorreu entre os tempos de 0 e 1 hora, seguida de uma queda gradativa e progressiva até o tempo de 24 horas. Os elásticos de látex apresentaram um comportamento mais estável no período estudado em relação aos sintéticos, em ambos os estudos.

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.

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 comparativo da degradação de forças geradas por elásticos ortodônticos sintéticos e molas de níquel-titânio

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

In vitro comparison of the force degradation of orthodontic intramural elastic from different compositions

Introduction and Objective: The synthetic intermaxillary elastic emerged as an alternative for clinical use in patients with latex sensitivity. However, there are disagreements about this elastic protocol use according to the force degradation. The aim of this study was to evaluate, in vitro, the forces generated by latex and synthetic elastics over time. Material and methods: Sample size of 840 elastics were used (420 latex and 420 synthetic), delivering medium strength (Dental Morelli®) with internal diameter of 1/8”, 3/16”, 1/4” and 5/16”. The elastics were randomly divided into 7 groups according to the time of the force measuring and immersed into distilled water at 37°C. To measure the force in each group, the elastics were stretched in six progressive increases of 100% of its internal diameter with the aid of a testing machine Emic and measured up to 72 hours. Data were analyzed with SPSS 16.0, using one-way analysis of variance (ANOVA). Results: Immediate force level of synthetic elastics was statistically higher than latex elastics in all strains, for the same size. However, the latex elastics mean force slightly decreased over time, while the synthetic elastics presented an abrupt decrease. Conclusion: The synthetic elastic presented severe force degradation, jeopardizing the cost-benefit ratio, which indicates a higher replacement frequency. The latex elastic showed better mechanical performance in comparison to synthetic ones.

Degradação de forças dos elasticos intermaxilares ortodônticos sintéticos

This study aimed to evaluate the force degradation of synthetic elastics over time using dynamic biomechanical tests in order to find clinical parameters of what size of elastic and frequency of exchange should be used in orthodontic therapy. It was used 240 elastics of Dental Morelli, sizes 1/8", 3/16", 1/4 "and 5/16", medium force, divided in four groups. In each group was measured forces at different times, from immediate to 72 hours after immersion in water at 37°C and incubated stretched to 600% of its initial inner diameter. Tensile tests were performed on a universal testing machine EMIC DL2000 submerged in distilled water maintained at 37°C. Data were analyzed using SPSS version 16.0, by the Analysis of Variance (One-Way) with Tukey´s post test. There was a greater increase in pattern of force decay of immediate measurement until 24 hours in all sizes of synthetic elastics, from which it was observed a decrease in force progressively smaller, with the exception of 5/16´´ elastic with a maximum force decay occurred at 12h. It was concluded that: the elastic synthetic Dental Morelli suffered significant force degradation over time, with reduction of approximately 70% of the initial force during 24 hours of stretching, followed by a progressively smaller decrease; the amount of stretch for a ideal force in intermaxillary therapies depends on the distance between the points of attachment of elastic, being necessary to consult the tables to choose the size, force and frequency of replacement.

Thermal decomposition of the synthetic hydrotalcite iowaite

The thermal stability and thermal decomposition pathways for synthetic iowaite have been determined using thermogravimetry in conjunction with evolved gas mass spectrometry. Chemical analysis showed the formula of the synthesised iowaite to be Mg6.27Fe1.73(Cl)1.07(OH)16(CO3)0.336.1H2O and X-ray diffraction confirms the layered structure. Dehydration of the iowaite occurred at 35 and 79°C. Dehydroxylation occurred at 254 and 291°C. Both steps were associated with the loss of CO2. Hydrogen chloride gas was evolved in two steps at 368 and 434°C. The products of the thermal decomposition were MgO and a spinel MgFe2O4. Experimentally it was found to be difficult to eliminate CO2 from inclusion in the interlayer during the synthesis of the iowaite compound and in this way the synthesised iowaite resembled the natural mineral.

The Behavior of Hydroxyl Units of Synthetic Goethite and its Dehydroxylated Product Hematite

The behavior of the hydroxyl units of synthetic goethite and its dehydroxylated product hematite was characterized using a combination of Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) during the thermal transformation over a temperature range of 180-270 degrees C. Hematite was detected at temperatures above 200 degrees C by XRD while goethite was not observed above 230 degrees C. Five intense OH vibrations at 3212-3194, 1687-1674, 1643-1640, 888-884 and 800-798 cm(-1), and a H2O vibration at 3450-3445 cm(-1) were observed for goethite. The intensity of hydroxyl stretching and bending vibrations decreased with the extent of dehydroxylation of goethite. Infrared absorption bands clearly show the phase transformation between goethite and hematite: in particular. the migration of excess hydroxyl units from goethite to hematite. Two bands at 536-533 and 454-452 cm(-1) are the low wavenumber vibrations of Fe-O in the hematite structure. Band component analysis data of FTIR spectra support the fact that the hydroxyl units mainly affect the a plane in goethite and the equivalent c plane in hematite.

An Improved Synthetic Route to the Potent Angiogenesis Inhibitor Benzyl Manα(1→3)-Manα(1→3)-Manα(1→3)-Manα(1→2)-Man Hexadecasulfate

An improved synthetic route to α(1→3)/α(1→2)-linked mannooligosaccharides has been developed and applied to a more efficient preparation of the potent anti-angiogenic sulfated pentasaccharide, benzyl Manα(1→3)-Manα(1→3)-Manα(1→3)-Manα(1→2)-Man hexadecasulfate, using only two monosaccharide building blocks. Of particular note are improvements in the preparation of both building blocks and a simpler, final deprotection strategy. The route also provides common intermediates for the introduction of aglycones other than benzyl, either at the building block stage or after oligosaccharide assembly. The anti-angiogenic activity of the synthesized target compound was confirmed via the rat aortic assay.

Simultaneous determination of three synthetic glucocorticoids by differential pulse stripping voltammetry with the aid of chemometrics

A novel voltammetric method for simultaneous determination of the glucocorticoid residues prednisone, prednisolone, and dexamethasone was developed. All three compounds were reduced at a mercury electrode in a Britton-Robinson buffer (pH 3.78), and well-defined voltammetric waves were observed. However, the voltammograms of these three compounds overlapped seriously and showed nonlinear character, and thus, it was difficult to analyze the compounds individually in their mixtures. In this work, two chemometrics methods, principal component regression (PCR) and partial least squares (PLS), were applied to resolve the overlapped voltammograms, and the calibration models were established for simultaneous determination of these compounds. Under the optimum experimental conditions, the limits of detection (LOD) were 5.6, 8.3, and 16.8 µg l-1 for prednisone, prednisolone, and dexamethasone, respectively. The proposed method was also applied for the determination of these glucocorticoid residues in the rabbit plasma and human urine samples with satisfactory results.

Raman spectroscopic study of the uranyl carbonate mineral čejkaite and its comparison with synthetic trigonal Na4[UO2(CO3)3]

Raman and infrared spectroscopies were used to characterise two samples of triclinic ejkaite Na4[UO2(CO3)3] and its synthetic trigonal analogue. The v3 (UO2)2+ mode is not Raman active, whereas both the v3 and v1 (UO2)2+ modes are infrared active. U--O bond lengths in uranyls were calculated from the spectra obtained and compared with bond lengths derived from crystal structure analyses. From the higher number of bands related to the uranyl and carbonate vibrations, the presence of symmetrically distinct (UO2)2+ and (CO3)2- units in both structures is proposed.

Thermal analysis of synthetic reevesite and cobalt substituted reevesite (Ni,Co)6Fe2(OH)16(CO3)•4H2O

The mineral reevesite and the cobalt substituted reevesite have been synthesised. The d(003) spacings of the minerals ranged from 7.54 to 7.95 Å. The maximum d(003) value occurred at around Ni:Co 0.4:0.6. This maximum in interlayer distance is proposed to be due to a greater number of carbonate anions and water molecules intercalated into the structure. The stability of the reevesite and cobalt doped reevesite was determined by thermogravimetric analysis. The maximum temperature of the reevesite occurs for the unsubstituted reevesite and is around 220°C. The effect of cobalt substitution results in a decrease in thermal stability of the reevesites. Four thermal decomposition steps are observed and are attributed to dehydration, dehydroxylation and decarbonation, decomposition of the formed carbonate and oxygen loss at ~807 °C. A mechanism for the thermal decomposition of the reevesite and the cobalt substituted reevesite is proposed.

Osteogenic induction of human bone marrow-derived mesenchymal progenitor cells in novel synthetic polymer-hydrogel matrices

The aim of this project was to investigate the in vitro osteogenic potential of human mesenchymal progenitor cells in novel matrix architectures built by means of a three-dimensional bioresorbable synthetic framework in combination with a hydrogel. Human mesenchymal progenitor cells (hMPCs) were isolated from a human bone marrow aspirate by gradient centrifugation. Before in vitro engineering of scaffold-hMPC constructs, the adipogenic and osteogenic differentiation potential was demonstrated by staining of neutral lipids and induction of bone-specific proteins, respectively. After expansion in monolayer cultures, the cells were enzymatically detached and then seeded in combination with a hydrogel into polycaprolactone (PCL) and polycaprolactone-hydroxyapatite (PCL-HA) frameworks. This scaffold design concept is characterized by novel matrix architecture, good mechanical properties, and slow degradation kinetics of the framework and a biomimetic milieu for cell delivery and proliferation. To induce osteogenic differentiation, the specimens were cultured in an osteogenic cell culture medium and were maintained in vitro for 6 weeks. Cellular distribution and viability within three-dimensional hMPC bone grafts were documented by scanning electron microscopy, cell metabolism assays, and confocal laser microscopy. Secretion of the osteogenic marker molecules type I procollagen and osteocalcin was analyzed by semiquantitative immunocytochemistry assays. Alkaline phosphatase activity was visualized by p-nitrophenyl phosphate substrate reaction. During osteogenic stimulation, hMPCs proliferated toward and onto the PCL and PCL-HA scaffold surfaces and metabolic activity increased, reaching a plateau by day 15. The temporal pattern of bone-related marker molecules produced by in vitro tissue-engineered scaffold-cell constructs revealed that hMPCs differentiated better within the biomimetic matrix architecture along the osteogenic lineage.