Sidnei Paciornik

Push-out Bond Strength of Resilon/Epiphany and Resilon/Epiphany Self-Etch to Root Dentin

INTRODUCTION The present study was designed to investigate the bond strength produced by Epiphany and Epiphany SE to root canal dentin. METHODS A sample of 36 human upper canines was prepared and assigned to experimental groups (n = 12), designated as group 1, Resilon/Epiphany; group 2, Resilon/Epiphany SE; and group 3, AH Plus/gutta-percha. After the filling procedures, each tooth was prepared for push-out assessment by using root slices of 1-mm thickness. Loading was performed on a universal testing machine at a speed of 0.5 mm/min. One-way analysis of variance and Tukey test for multiple comparisons were used to compare the results among the experimental groups. RESULTS AH Plus/gutta-percha root fillings showed significantly higher push-out bond strength than both Resilon/Epiphany and Resilon/Epiphany SE (P < .05). There was no significant difference between Epiphany/Resilon and Epiphany SE/Resilon (P > .05). CONCLUSIONS Under the present in vitro conditions, the adhesiveness quality to root dentin promoted by both Epiphany sealers is compromised even when teeth with simple anatomic features were obturated under well-monitored laboratory conditions.

Critical appraisal of published smear layer-removal studies: methodological issues

The smear layer phenomenon has been extensively addressed over the past 3 decades. However, there still are unanswered questions on this issue and the main responsible factor is the qualitative and nonreproducible character of most in vitro smear layer removal studies. The methodological reasons that led to the current lack of reliable conclusions on procedures aiming to remove the smear layer are comprehensively addressed. The limitations and outcomes related to different assessment methods are discussed as well. General speaking, the results by score-based conventional SEM studies are not trustworthy and reproducible. Computational routines able to automatically extract quantitative data of dentin morphology are necessary to minimize the human bias. An ideal experimental model should have a longitudinal observational character, in which a given dentin area can be observed at different times. The use of flat dentin samples should be avoided because of the influence of gravity as well as root canal anatomy on the final result of the chelating process. The experimental model also needs to take into consideration the amount and distribution of sclerotic dentin and irregular secondary dentin, otherwise the final results can be compromised. Inasmuch as there is a clear lack of scientific standard, simple comparative SEM evaluations are pointless at the present moment. The ideal experimental model to assess smear layer removal is not currently available. Therefore, further research efforts should be directed to the development of and testing of new methodological approaches to be used in the smear layer removal studies. The improvement of the experimental models is a requirement to draw up optimized clinical guidelines for the chemical treatment of the root dentin.

Strong effect on dentin after the use of high concentrations of citric acid: An assessment with co-site optical microscopy and ESEM

OBJECTIVES To perform a longitudinal analysis of the effect of four substances (citric acid at 1%, 5% and 10% concentrations and 17% EDTA) on dentin. METHODS Sixteen human molars had their crowns removed exposing cervical root dentin. A grinding procedure was used to produce a standardized smear layer and to create a smooth surface for analysis. Environmental scanning electron microscopy (ESEM) was used for qualitative observations while co-site optical microscopy (CSOM) and image analysis (IA) provided a quantitative comparison of the effect of the substances for several experimental times from 15 to 300s. The methods allowed the observation of the same areas after each experimental time. The open tubule area fraction was measured for several CSOM image fields, at each experimental time, for the four substances. Thus, it was possible to follow the phenomenon and quantitatively analyze the effect of the substances. Kolmogorov-Smirnov, Kruskal-Wallis H and Wilcoxon signed-ranks (with Bonferroni correction) tests were used to analyze the data. The level of significance was set at p<0.05. RESULTS The CA solutions showed the greatest chelating effect, which was proportional to concentration (EDTA: 9.4-32.8% (15-300s); 1% CA: 21.1-32.2% (15-300s); 5% CA: 32.4-43.1% (15-300s); 10% CA: 35.1-39.5% (15-30s). Erosive effects were observed on inter and peritubular dentin for 5% CA and 10% CA after 60s. SIGNIFICANCE ESEM allowed a detailed qualitative comparison of the effect of the four substances. CSOM and IA provided a quantitative comparison method with good statistical significance. Future studies should focus on the consequences of dentin erosion caused by citric acid.

Automatic Classification of Graphite in Cast Iron

A method for automatic classification of the shape of graphite particles in cast iron is proposed. In a typical supervised classification procedure, the standard charts from the ISO-945 standard are used as a training and validation population. Several shape and size parameters are described and used as discriminants. A new parameter, the average internal angle, is proposed and is shown to be relevant for accurate classification. The ideal parameter sets are determined, leading to validation success rates above 90%. The classifier is then applied to real cast iron samples and provides results that are consistent with visual examination. The method provides classification results per particle, different from the traditional per field chart comparison methods. The full procedure can run automatically without user interference.

AVALIAÇÃO DO EFEITO DE NANOPARTÍCULAS DE TiO2 COM MORFOLOGIA 1D NAS CINÉTICAS DE SORÇÃO DE HIDROGÊNIO DO MgH2

* Contribuição técnica ao 72o Congresso Anual da ABM – Internacional e ao 17o ENEMET Encontro Nacional de Estudantes de Engenharia Metalúrgica, de Materiais e de Minas, parte integrante da ABM Week, realizada de 02 a 06 de outubro de 2017, São Paulo, SP, Brasil. AVALIAÇÃO DO EFEITO DE NANOPARTÍCULAS DE TiO2 COM MORFOLOGIA 1D NAS CINÉTICAS DE SORÇÃO DE HIDROGÊNIO DO MgH2 * Anderson de Farias Pereira Sidnei Paciornik Dilson Silva dos Santos Paula Mendes Jardim Resumo Estudos recentes sugerem que a produção de nanocompósitos de MgH2 com nanomateriais de morfologia 1D baseados em TiO2 produzidos via moagem reativa promovem aumento significativo na cinética de absorção-dessorção de hidrogênio deste material, o que favoreceria sua aplicação em tecnologias de armazenamento de hidrogênio em estado sólido. A proposta deste trabalho é avaliar o efeito da energia de moagem na integridade das nanopartículas e seu desdobramento nas cinéticas de sorção do material. Para tal, amostras de MgH2 com 5%p. de nanobastões de TiO2 (NR-550) foram produzidas em moinho de bolas planetário a 100, 200 e 300 rpm, respectivamente. Difração de Raios X (DRX) foi utilizada para caracterizar a estrutura cristalina e Microscopia Eletrônica de Transmissão (MET) associada com EDS para analisar o tamanho e morfologia dos catalisadores em meio ao hidreto. Os resultados até o momento indicam que o processo de moagem a 100 rpm não ocasionou variação significativa na distribuição de tamanho e razão de aspecto comparado ao aditivo puro (com valor médio de 35 nm e 2,70 respectivamente). Ensaios de cinética de sorção de hidrogênio ainda estão em andamento. Palavras-chave: MgH2;TiO2;Nanomateriais 1D; Armazenamento de Hidrogênio.

Pattern recognition in the characterization of the mesostructure of bamboo

Using digital image processing and pattern recognition techniques, a supervised classification procedure of bamboo vascular bundles was developed and tested on polished cross sections of bamboo culms from four different species. Results obtained for same species samples were similar and were consistent with visual observations.