Efeito das técnicas de inserção e ativação da resina composta sobre a microinfiltração e microdureza Effect of techniques of composite resin insertion and polymerization on microleakage and microhardness

O objetivo deste trabalho foi avaliar a influência da técnica de ativação e de inserção da resina composta sobre a microinfiltração marginal e microdureza em restaurações classe II. Foram preparadas 180 cavidades que foram divididas em 6 grupos: G1 - incremento único + ativação convencional; G2 - incrementos vestíbulo-linguais + ativação convencional; G3 - incremento único + ativação "soft-start"; G4 - incrementos vestíbulo-linguais + ativação "soft-start"; G5 - incremento único + ativação progressiva; G6 - incrementos vestíbulo-linguais + ativação progressiva. Todas as cavidades foram restauradas com o sistema Z100/Single Bond (3M). Após 1.000 ciclos térmicos (5 e 55ºC), os espécimes foram imersos em solução aquosa de azul de metileno a 2%, por 4 horas e a microinfiltração foi avaliada. Metade dos espécimes foram incluídos em resina de poliestireno e a microdureza Knoop foi avaliada. Após o teste Kruskal-Wallis, não foi observada diferença significativa (p > 0,05) entre todas as técnicas de ativação e de inserção quanto à microinfiltração. Quanto à microdureza, após os testes análise de variância (2 fatores) e Tukey, não houve diferença significativa entre as técnicas restauradoras empregadas (p > 0,05), porém a ativação progressiva (G5 e G6) apresentou menor dureza Knoop (p < 0,05): G1 = 144,11; G2 = 143,89; G3 = 141,14; G4 = 142,79; G5 = 132,15; G6 = 131,67. Concluiu-se que as técnicas de ativação e de inserção da resina composta não afetaram a microinfiltração, mas ocorreu uma diminuição na microdureza do material quando a ativação progressiva foi utilizada.<br>The aim of this study was to evaluate the influence of techniques of composite resin polymerization and insertion on microleakage and microhardness. One hundred and eighty class II cavities were prepared in bovine teeth and assigned to six groups: G1 - bulk filling + conventional polymerization; G2 - bucco-lingual increments + conventional polymerization; G3 - bulk filling + soft-start polymerization; G4 - bucco-lingual increments + soft-start polymerization; G5 - bulk filling + progressive polymerization; G6 - bucco-lingual increments + progressive polymerization. All cavities were restored with the Z100/Single Bond system (3M). After thermocycling, the samples were immersed in 2% methylene blue dye solution for 4 hours. Half of the samples were embedded in polystyrene resin, and Knoop microhardness was measured. The Kruskal-Wallis test did not reveal statistical differences (p > 0.05) between the polymerization and insertion techniques as to microleakage. Regarding microhardness, the two-way ANOVA and the Tukey test did not reveal statistical differences between the restorative techniques (p > 0.05), but progressive polymerization (G5 and G6) was associated with smaller Knoop microhardness values (p < 0.05): G = 144.11; G2 = 143.89; G3 = 141.14; G4 = 142.79; G5 = 132.15; G6 = 131.67. It was concluded that the evaluated polymerization and insertion techniques did not affect marginal microleakage, but a decrease in microhardness occurred when progressive polymerization was carried out

The complex of Diplodia species associated with Fraxinus and some other woody hosts in Italy and Portugal

Studies on the taxonomy and phylogeny of Diplodia have been hampered by the lack of an ex-type culture linked to the holotype of D. mutila, which is the type of the genus. In this study a large collection of Diplodia strains, obtained from ash and other woody hosts showing V-shaped cankers and branch dieback, were identified based on morphological characters and DNA sequence data from ITS and EF1-α loci. Results of combined morphological and phylogenetic analyses showed that the Fraxinus isolates from Italy, the Netherlands, Portugal and Spain belong to three distinct species namely Diplodia fraxini, Diplodia mutila and Diplodia subglobosa sp. nov. An epitype was designated for Diplodia mutila, with associated ex-epitype cultures. The name D. fraxini is re-instated and a neotype designated. Two species, Diplodia seriata and Diplodia pseudoseriata were reported for the first time on Fraxinus spp

Clinical studies of dental erosion and erosive wear

Item does not contain fulltextWe define erosion as a partial demineralisation of enamel or dentine by intrinsic or extrinsic acids and erosive tooth wear as the accelerated loss of dental hard tissue through the combined effect of erosion and mechanical wear (abrasion and attrition) on the tooth surface. Most experts believe that during the last decade there has been a significant increase in the prevalence and severity of erosive tooth wear, particularly in adolescents. Even when erosive wear occurs in its milder forms, this is a matter of concern, as it may compromise the integrity of an otherwise healthy dentition in later life. The erosive wear process is complicated and modified by many chemical, behavioural and associated processes in the mouth. If interventions are to be developed it is therefore important that in vivo methods are developed to assess the outcomes of the erosion and erosive wear processes and the effects of interventions upon them. This paper discusses potential methods of investigating erosion and erosive wear in vivo and the difficulties associated with clinical studies

Adaptive Sampling of Large Deviations

International audienceWe introduce and test an algorithm that adaptively estimates large deviation functions characterizing the fluctuations of additive functionals of Markov processes in the long-time limit. These functions play an important role for predicting the probability and pathways of rare events in stochastic processes, as well as for understanding the physics of nonequilibrium systems driven in steady states by external forces and reservoirs. The algorithm uses methods from risk-sensitive and feedback control to estimate from a single trajectory a new process, called the driven process, known to be efficient for importance sampling. Its advantages compared to other simulation techniques, such as splitting or cloning, are discussed and illustrated with simple equilibrium and nonequilibrium diffusion models