Determinação do impacto da variação da viscosidade em resinas compostas auto-adesivas experimentais : adesão e propriedades reológicas

Dissertação para obtenção do grau de Mestre no Instituto Universitário Egas MonizObjetivos: Avaliar e comparar a resistência adesiva à dentina e a viscosidade, de diferentes resinas compostas auto-adesivas (RCA) flowable experimentais formuladas com diferentes monómeros funcionais e proporções de pó para líquido. Materiais e métodos: Foram produzidos 9 RCA, à base de dimetilacrilato de uretano (UDMA) e dimetacrilato de propileno glicol (PPGDMA), variando o monómero funcional (i.e., metacrilato de hidroxietilo, HEMA; glicerolfosfato dimetacrilato, GPDM; 10-metacriloiloxidecil dihidrogeno fosfato, 10-MDP) e a fase inorgânica híbrida, com vidros de bário e nanopartículas de sílica. Diferentes formulações foram alcançadas variando a proporção de pó e líquido, obtendo-se os rácios de 2.5, 2.2 e 1.9. A viscosidade das soluções não polimerizadas foi estudada através de um ensaio de escoamento (n=3), à temperatura ambiente com variação da taxa de cisalhamento de 0 a 100 s-1. As RCA foram analisadas em termos de capacidade de adesão à dentina. Inicialmente, 54 dentes humanos hígidos foram cortados e lixados de forma a expor a dentina. Foi realizada uma cavidade de cerca de 2 mm de altura, onde cada RCA foi colocada e polimerizada. De seguida, os dentes foram armazenados durante 24 h a 37 ºC. A resistência ao deslocamento adesivo foi estudada por perfilometria após um ensaio de desgaste por teste de raspagem (0.25 N, 1 N e 5 N, 10N, 15N e 30N, 4 mm amplitude, a 0.0875 mm/min) (n=3). Métodos de estatística descritiva e inferencial de modo a testar as hipóteses nulas formuladas, com recurso ao software SPSS v. 26.0 com nível de significância de 5% foram realizados. Resultados: O ensaio de viscosidade mostrou que todas as RCA experimentais, em todos os rácios testados, apresentaram comportamento não-newtoniano, ou seja, a medida que a força de cisalhamento aumentava, diminuía a viscosidade. Enquanto ao teste de arranhão, as resinas formuladas com os monómeros GPDM e HEMA, nos rácios de 2.5, descolaram-seda dentina com as forças de 30 N. Conclusão: O ensaio de viscosidade mostrou as resinas compostas auto-adesivas experimentais variavam em viscosidade devido não só ao rácio, mas também ao monómero funcional. A variação do monómero funcional nas resinas experimentais auto-adesivas, afeta significativamente a resistência a força de adesão destes materiais.Objectives: To evaluate and compare the dentin bond strength and viscosity of different experimental flowable self-adhesive composite resins (SCR) formulated with different functional monomers and powder to liquid ratios. Materials and methods: Nine RCA were produced, based on urethane dimethylacrylate (UDMA) and dimetacrilato de propileno glicol (PPGDMA), varying the functional monomer (i.e., hydroxyethyl methacrylate, HEMA; glycerol dimethacrylate, GPDM; 10-methacryloyloxydecyl dihydrogen phosphate, 10-MDP) and the hybrid inorganic phase, with barium glasses and silica nanoparticles. Different formulations were achieved by varying the proportion of powder and liquid, obtaining the ratios of 2.5, 2.2 and 1.9. Canforoquinone (CQ) was added to all RCA, as a photoinitiator. The viscosity of the unpolymerized solutions was studied through a flow test (n=3), at room temperature with variation of the shear rate from 0 to 100 s-1. The RCA were analyzed in terms of their ability to adhere to the dentin. Initially, 54 healthy human teeth were cut and sanded in order to expose the dentin. A cavity of about 2 mm in height was made in each dentin, where each RCA was placed and polymerized. The teeth were then stored with the RCA for 24 h at 37 °C. The surface roughness of the polymerized samples was studied by profilometry before and after a scratch test (0.25 N, 1 N , 5 N, 15 N e 30 N, 4 mm scratch width, at 0.0875 mm/min) (n=3). Descriptive and inferential statistical methods in order to test the null hypotheses formulated, using SPSS v. 26.0 software at 5% significance level were performed. Results: The admission test showed that all experimental self-adhesive composite resins, in all tested ratios, presented non-Newtonian behavior, that is, as the shear force increased, admission decreased. As for the scratch test, the resins formulated with GPDM and HEMA monomers in ratios of 2.5, detached from silk dentin with forces of 30 N. Conclusion: The viscosity test showed that the experimental self-adhesive composite resins varied in viscosity due not only to the ratio, but also to the functional monomer. The functional monomer variation in self-adhesive experimental resins significantly affects the resistance and bond strength of these materials

Effect of thermal cycling on denture base and autopolymerizing reline resins

Objective This study evaluated the fracture toughness (FT) of denture base and autopolymerizing reline resins, with and without thermocycling (T). Material and Methods Specimens of each material (denture base acrylic resin - Lucitone 550 – L; autopolymerizing reline resins - Ufi Gel Hard–UH, Tokuyama Rebase II-TR, New Truliner–NT and Kooliner-K), were produced, notched and divided into two groups (n=10): CG (control group of autopolymerizing reline resins and L): FT tests were performed after polymerization; TG (thermocycled group): FT tests were performed after T (5°C and 55°C for 5,000 cycles). Results: Results (MPa.m1/2) were analyzed by two-way ANOVA and Tukey's test (p=0.05). L exhibited the highest FT mean values in both groups (CG - 2.33; TG - 2.17). For the CG groups, NT showed the highest FT (1.64) among the autopolymerizing reline resins, and K the lowest (1.04). After T, when the autopolymerizing reline resins were compared, a statistically significant difference in FT was found only between the NT (1.46) and TR (1.00). Conclusions Thermocycling increased the FT of K and did not influence the FT of L, UH, TR and NT

Dinâmica do crescimento de árvores dominantes em povoamentos clonais de Tectona grandis Linn. F.

O objetivo deste trabalho foi avaliar a dinâmica das árvores dominantes na classificação da capacidade produtiva de sítios florestais e verificar se a estrutura sugerida por Schumacher é estatisticamente indicada para descrever o crescimento em altura dominante de árvores clonais de teca. Para este fim foram abordadas duas distintas formas de classificação de árvore dominante. Uma primeira que fixa estas árvores na primeira medição da parcela de inventário florestal, sendo, portanto, uma única classificação durante toda a rotação do povoamento. Uma segunda que classifica uma árvore dominante em cada medição da parcela, e posterior cálculo da altura médias das arvores dominantes. Nesta pesquisa os dados foram originados do monitoramento contínuo de 121 parcelas de campo, com idade variando de 1,1 a 8,1 anos, de plantios comerciais de Tectona grandis Linn. F, localizados na região centro-sul do estado de Mato Grosso.  Para fins de comparação das duas abordagens do estudo, foram utilizadas as estatísticas de coeficiente de determinação (R²) e o erro padrão em escala percentual. As estatísticas dos modelos foram complementadas pela análise da estabilidade das parcelas na rotação do povoamento, e também pela identidade das curvas. As estatísticas de ambos os métodos de classificação foram muito próximas, com R² de 0,9950 e 0,9953, e erro padrão residual de 22,56 e 21,48%. Quanto à estabilidade, o modelo de Schumacher, para ambos os métodos, classificou como estável mais de 90% das parcelas utilizadas no estudo. E sobre a identidade das curvas, pôde-se inferir que ambas as curvas de sítios foram similares na classificação da capacidade produtiva. Portanto, foi possível concluir que não existe diferença estatística entre as curvas de sítios quando consideradas as diferentes classificações de árvores dominantes, o que comprova a hipótese de que árvores dominantes se mantém dominantes durante toda a rotação florestal

Effect of thermal cycling on denture base and autopolymerizing reline resins

OBJECTIVE: This study evaluated the fracture toughness (FT) of denture base and autopolymerizing reline resins, with and without thermocycling (T). MATERIAL AND METHODS: Specimens of each material (denture base acrylic resin - Lucitone 550 - L; autopolymerizing reline resins - Ufi Gel Hard-UH, Tokuyama Rebase II-TR, New Truliner- NT and Kooliner-K), were produced, notched and divided into two groups (n=10): CG (control group of autopolymerizing reline resins and L): FT tests were performed after polymerization; TG (thermocycled group): FT tests were performed after T (5ºC and 55ºC for 5,000 cycles). RESULTS: Results (MPa.m((1/2))) were analyzed by two-way ANOVA and Tukey's test (p=0.05). L exhibited the highest FT mean values in both groups (CG - 2.33; TG - 2.17). For the CG groups, NT showed the highest FT (1.64) among the autopolymerizing reline resins, and K the lowest (1.04). After T, when the autopolymerizing reline resins were compared, a statistically significant difference in FT was found only between the NT (1.46) and TR (1.00). CONCLUSIONS: Thermocycling increased the FT of K and did not influence the FT of L, UH, TR and NT

Age-Related Metabolic Pathways Changes in Dental Follicles: A Pilot Study

Aging is not a matter of choice; it is our fate. The “time-dependent functional decline that affects most living organisms” is coupled with several alterations in cellular processes, such as cell senescence, epigenetic alterations, genomic instability, stem cell exhaustion, among others. Age-related morphological changes in dental follicles have been investigated for decades, mainly motivated by the fact that cysts and tumors may arise in association with unerupted and/or impacted teeth. The more we understand the physiology of dental follicles, the more we are able to contextualize biological events that can be associated with the occurrence of odontogenic lesions, whose incidence increases with age. Thus, our objective was to assess age-related changes in metabolic pathways of dental follicles associated with unerupted/impacted mandibular third molars from young and adult individuals. For this purpose, a convenience sample of formalin-fixed paraffin-embedded (FFPE) dental follicles from young (<16 y.o., n = 13) and adult (>26 y.o., n = 7) individuals was selected. Samples were analyzed by high-performance liquid chromatography-mass spectrometry (HPLC-MS)-based untargeted metabolomics. Multivariate and univariate analyses were conducted, and the prediction of altered pathways was performed by mummichog and Gene Set Enrichment Analysis (GSEA) approaches. Dental follicles from young and older individuals showed differences in pathways related to C21-steroid hormone biosynthesis, bile acid biosynthesis, galactose metabolism, androgen and estrogen biosynthesis, starch and sucrose metabolism, and lipoate metabolism. We conclude that metabolic pathways differences related to aging were observed between dental follicles from young and adult individuals. Our findings support that similar to other human tissues, dental follicles associated with unerupted tooth show alterations at a metabolic level with aging, which can pave the way for further studies on oral pathology, oral biology, and physiology

Brown Spider (Loxosceles genus) Venom Toxins: Tools for Biological Purposes

Venomous animals use their venoms as tools for defense or predation. These venoms are complex mixtures, mainly enriched of proteic toxins or peptides with several, and different, biological activities. In general, spider venom is rich in biologically active molecules that are useful in experimental protocols for pharmacology, biochemistry, cell biology and immunology, as well as putative tools for biotechnology and industries. Spider venoms have recently garnered much attention from several research groups worldwide. Brown spider (Loxosceles genus) venom is enriched in low molecular mass proteins (5–40 kDa). Although their venom is produced in minute volumes (a few microliters), and contain only tens of micrograms of protein, the use of techniques based on molecular biology and proteomic analysis has afforded rational projects in the area and permitted the discovery and identification of a great number of novel toxins. The brown spider phospholipase-D family is undoubtedly the most investigated and characterized, although other important toxins, such as low molecular mass insecticidal peptides, metalloproteases and hyaluronidases have also been identified and featured in literature. The molecular pathways of the action of these toxins have been reported and brought new insights in the field of biotechnology. Herein, we shall see how recent reports describing discoveries in the area of brown spider venom have expanded biotechnological uses of molecules identified in these venoms, with special emphasis on the construction of a cDNA library for venom glands, transcriptome analysis, proteomic projects, recombinant expression of different proteic toxins, and finally structural descriptions based on crystallography of toxins

Avaliação in vitro da citotoxicidade de monômeros, plastificante e produtos de degradação liberados a partir de resinas para reembasamento imediato

O presente estudo teve como objetivo avaliar o efeito citotóxico dos monômeros isobutil metacrilato (IBMA) e 1,6 – Hexanediol dimetacrilato (1,6 – HDMA), do plastificante di-n-butil ftalato (DBP), e dos produtos de degradação ácido metacrílico (AM) e ácido benzóico (AB) sobre células L929. Esses compostos foram testados em faixas de concentrações liberadas, em um período de 30 dias, por materiais reembasadores rígidos, previamente quantificadas em estudos anteriores. O efeito citotóxico foi verificado por meio dos testes de MTT e 3H-timidina, após as células terem sido expostas às substâncias testadas nas concentrações estabelecidas. A classificação da citotoxicidade foi baseada na viabilidade celular em relação ao controle (células expostas ao meio sem as substâncias testadas). A atividade de síntese de DNA foi inibida por todos os compostos. Os resultados do presente estudo demonstraram que o teste de 3H-timidina foi mais sensível que o teste de MTT e que os compostos avaliados mostraram diferentes níveis de citotoxicidade in vitro. A atividade da desidrogenase mitocondrial diminuiu nas células tratadas com os monômeros, o plastificante e o produto de degradação AM; porém, para o AB, a maioria das concentrações testadas não apresentou efeito citotóxico.The aim of this study was to evaluate the cytotoxic effect of the monomers 1,6 – hexanediol dimethacrylate (1,6 - HDMA) and isobutyl methacrylate (IBMA), the plasticizer di-n-butyl phthalate (DBP), and the degradation by-products methacrylic acid (MA) and benzoic acid (BA) on L929 cells. These compounds were tested in the range of concentrations released in 30 days from hard chairside reline resins that were quantified in previous investigations. Cytotoxic effects were assessed by using MTT and 3H - thymidine assays after the cells had been exposed to the test compounds at the given concentrations. Cytotoxicity was rated based on cell viability relative to controls (cells exposed to medium without test substances). The results presented in this study demonstrated that the 3H-thymidine assay was more sensitive than the MTT assay, and all compounds tested showed varying degrees of cytotoxic effect in vitro. DNA synthesis activity was inhibited by all compounds. Mitochondrial dehydrogenase activity decreased in cells treated with monomers, plasticizer and MA by-product, whereas no cytotoxic effect was observed on contact with BA at the majority of concentrations tested.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

A quantitative and qualitative evaluation of reports of clinical trials published in six Brazilian dental journals indexed in the Scientific Electronic Library Online (SciELO)

INTRODUCTION: Open access publishing is becoming increasingly popular within the biomedical sciences. SciELO, the Scientific Electronic Library Online, is a digital library covering a selected collection of Brazilian scientific journals many of which provide open access to full-text articles.This library includes a number of dental journals some of which may include reports of clinical trials in English, Portuguese and/or Spanish. Thus, SciELO could play an important role as a source of evidence for dental healthcare interventions especially if it yields a sizeable number of high quality reports. OBJECTIVE: The aim of this study was to identify reports of clinical trials by handsearching of dental journals that are accessible through SciELO, and to assess the overall quality of these reports. MATERIAL AND METHODS: Electronic versions of six Brazilian dental Journals indexed in SciELO were handsearched at www.scielo.br in September 2008. Reports of clinical trials were identified and classified as controlled clinical trials (CCTs - prospective, experimental studies comparing 2 or more healthcare interventions in human beings) or randomized controlled trials (RCTs - a random allocation method is clearly reported), according to Cochrane eligibility criteria. CRITERIA TO ASSESS METHODOLOGICAL QUALITY INCLUDED: method of randomization, concealment of treatment allocation, blinded outcome assessment, handling of withdrawals and losses and whether an intention-to-treat analysis had been carried out. RESULTS: The search retrieved 33 CCTs and 43 RCTs. A majority of the reports provided no description of either the method of randomization (75.3%) or concealment of the allocation sequence (84.2%). Participants and outcome assessors were reported as blinded in only 31.2% of the reports. Withdrawals and losses were only clearly described in 6.5% of the reports and none mentioned an intention-to-treat analysis or any similar procedure. CONCLUSIONS: The results of this study indicate that a substantial number of reports of trials and systematic reviews are available in the dental journals listed in SciELO, and that these could provide valuable evidence for clinical decision making. However, it is clear that the quality of a number of these reports is of some concern and that improvement in the conduct and reporting of these trials could be achieved if authors adhered to internationally accepted guidelines, e.g. the CONSORT statement

Effects of Soft Denture Liners on L929 Fibroblasts, HaCaT Keratinocytes, and RAW 264.7 Macrophages

The effects of six soft liners (Ufi Gel P (UG), Sofreliner S (SR), Durabase Soft (D), Trusoft (T), Coe Comfort (CC), and Softone (ST)) on L929, HaCat, and RAW 264.7 cells were investigated. Eluates (24 and 48 h) from the materials were applied on the cells and the viability, type of cell death, and morphology were evaluated. Cells were also seeded on the specimens' surfaces (direct contact) and incubated (24 or 48 h), and viability was analyzed. Controls were cells in culture medium without eluates or specimens. For cell viability, no significant differences were found among materials or between extraction periods, and the liners were noncytotoxic or slightly cytotoxic. Morphology of RAW 264.7 cells was altered by the 24 h eluates from CC and D and the 48 h eluates from SR, CC, and D. The 24 and 48 h eluates from all materials (except T) increased the percentages of L929 necrotic cells. For direct contact tests, the lowest cytotoxicity was observed for UG and SR. Although eluates did not reduce viability, morphology alterations and increase in necrosis were seen. Moreover, in the direct contact, effects on viability were more pronounced, particularly for D, T, CC and ST. Thus, the use of UG and SR might reduce the risk of adverse effects.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq