Durable bonds at the adhesive/dentin interface: an impossible mission or simply a moving target?

Composite restorations have higher failure rates, more recurrent caries and increased frequency of replacement as compared to dental amalgam. Penetration of bacterial enzymes, oral fluids, and bacteria into the crevices between the tooth and composite undermines the restoration and leads to recurrent decay and failure. The gingival margin of composite restora tions is particularly vulnerable to decay and at this margin, the adhesive and its seal to dentin provides the primary barrier between the prepared tooth and the environment. The intent of this article is to examine physico-chemical factors that affect the integrity and durability of the adhesive/dentin interfacial bond; and to explore how these factors act synergistically with mechanical forces to undermine the composite restoration. The article will examine the various avenues that have been pursued to address these problems and it will explore how alterations in material chemistry could address the detrimental impact of physico-chemical stresses on the bond formed at the adhesive/dentin interface.

Avaliação do selamento de ápices radiculares retrobturados ou recobertos com diferentes materiais mediante infiltração marginal por corante e análise da interface em microscopia eletrônica de varredura

The purpose of this study was to evaluate the apical sealing ability and the marginal adaptation of five dental materials used in retrofillings or applied to the bevelled root surface. One hundred and forty extracted single rooted human teeth were used, divided into seven groups of twenty each. ln the first, second, third and fourth groups, the teeth were apicoectomized, submitted to cavity preparations and retrofilled with one of the following materiais: zinc free silver amalgam, a dentin bonding system plus composite resin, a glass ionomer cement ora compomer. In the fifth, sixth and seventh groups, the teeth were apicoectomized and capped on the bevelled root surface with one of the following materiais: a dentin bonding system plus composite resin, a glass ionomer cement or a compomer. Two specimens of each experimental group were evaluated for the marginal adaptation using scanning electron microscopy. The remaining 126 specimens were immersed in 2% methylene blue dye, stored for one week at 37ºC and the infiltration was evaluated with a stereomicroscope. The results showed that the glass ionomer cement presented the lowest values of marginal infiltration when used as retrofilling material, with a significant statistical difference when compared with the others tested materials. When used as apical capping, the glass ionomer cement and the compomer were equivalent and significantly better than the dentin bonding system plus composite resin. Using scanning electron microscopy, all the materials showed some slight adjustment problem. ln the retrofilling, the smallest marginal gaps were observed with the compomer and the dentin bonding system plus composite resin, while the largest were observed with the glass ionomer cement and zinc free silver amalgam. ln the apical capping, the smallest marginal gaps were observed with the compomer and the dentin bonding system plus composite resin and ...

Análise por computação gráfica das alterações produzidas em próteses totais superiores imersas diretamente em água e pela termociclagem

Objectives: This study aimed to assess dimensional changes in acrylic resin base and artificial teeth position after water storage and thermocycling using computer graphics measurements. Methods: Twenty-four waxed replicas were obtained from a previous upper complete denture. For linear measurements, points in cusps tips of left central incisor and second premolars and molars were marked in one of the prostheses with graphite and transferred to the others using an acrylic resin guide. The prostheses were scanned after waxing, polymerization and treatments and the images were exported to “AutoCad 2002 Today®” software for measurements. Results: There was no statistically significant difference in changes of each segment for each group and between the phases evaluated after polymerization and thermocycling. In groups I and III, the values after polymerization are higher than those after treatment, which suggests shrinkage while the prostheses in group II have expanded. Conclusion: The three groups exhibited artificial teeth movement after tests in comparison to the polymerized prosthesis. The prostheses submitted to water storage in kiln at 36ºC during seven days showed different behavior than the other groups.

Análise da interface adesiva entre pinos de fibra de vidro e dentina intrarradicular submetida à irrigação com diferentes agentes condicionantes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ensino de ciências e educação moral: uma interface de implicações mútuas

Nas teorias sociomorais que perpassam Piaget, Kohlberg e Habermas, encontramos subsídios para o ensino de Ciências que se estabelece na perspectiva da construção crítica do conhecimento e da desmistificação da visão de ciência, assim como, de forma correspondente, também encontramos nos pressupostos do ensino crítico e desmistificado de Ciências um conjunto de subsídios que potencializa o desenvolvimento moral e a dimensão ética discursiva. Neste artigo, compartilhamos com o leitor alguns de nossos argumentos em prol da existência dessa ainda subestimada interface de implicações mútuas entre Ensino de Ciências e Educação Moral, com a presença de relevantes subsídios teórico-práticos que uma área pode dar à outra. A expectativa é que as discussões apresentadas contribuam para a reflexão do trabalho docente, numa perspectiva de educação científica e moral baseada no processo de construção da autonomia do aluno.

Computação gráfica: ferramenta didática de comunicação, design e produção

This paper aims to show some advantages brought by the computer graphics and inter-disciplinary communication within the academic institution UNESPBauru, using it as a teaching tool in undergraduate engineering and design. The communication in the classroom could be reconfigured through the adoption of new technologies by drawing a parallel between old and new programmatic contents, setting goals and parameters to improve communication between teacher and student, transferring and sediment of the given content and increasing production in quantity and complexity of work undertaken by students. As an example of computer graphics use, this work presents a final graduation work that was successful in the market, "Teardrop Trailer Caracol", as result of the final adoption of CAD technology as a teaching tool, design and production.

Projeto ergonômico de assento para tratores, utilizando-se dos recursos da computação gráfica

Regardless its power rate, the tractors are the most used source in operations of tillage. Thus, due to the expansion of cultivated areas and the need of striking application of technologies to meet the advance of agribusiness, it has been shown that these machines are concentrated during the work periods, the physical and mechanical actions to perform the activity. So, it's possible to realize that the time of physical exposures and the operational decision-making are related with the job station comfort. In regard to what was mentioned, this paper's main objective is to design an ergonomically viable seat to furnish the operational requirements of the tractor driver, using the new CAD / CAE technologies in order to provide optimal comfort to the relationship between human being and machines.

GeoGebra e o método de Briot & Bouquet para a resolução gráfica de equações cúbicas

In the mid-nineteenth century, french mathematicians Briot and Bouquet have proposed an intriguing graphical method for solving cubic equations "depressed" - the third degree equations that do not have the quadratic term. The proposal is simple geometric construction, though based on an ingenious algebra. We propose here the verification and testing graphical method through an instructional sequence using the software GeoGebra also present the ingenious algebraic development that resulted in this graphic method for determination of real roots of a cubic equation of the type x³ + px + q = 0 where p and q are real numbers. The method states that these solutions are summarized in the abscissas of the points of intersection of the circumference containing the origin and the center C (-q/2, 1-p/2) with the parable y = x².

Uma proposta de formação continuada de professores de ciências e matemática na interface do agir comunicativo e das questões sociocientíficas

The objective of this paper is to present a theoretical proposal for the training of teachers of mathematics and science at the interface of communicative action and socio-scientific issues. In this paper we argue for the need for a continuous training of teachers if we are to be interested in developing the scientific training of students from the public school system. To form communicatively competent students, by the end of schooling, becomes necessary the training of argumentatively competent teachers. Therefore, we believe that the theory of communicative action by Jurgen Habermas, will cooperate to this end.

Problemas ergonômicos enfrentados por profissionais de enfermagem em ambientes hospitalares: aspectos da interface trabalhadores x equipamentos

The ergonomic design seeks to establish parameters to improve the interface between the technologies (products, systems and environments) and between man (users). Among the many factors involved, there are the activities performed in hospital settings, both by patients and by clinical staff. Accordingly, efforts have been demonstrated biomechanical with a leading occupational problem, especially regarding the transfer of patients.

Problemas ergonômicos enfrentados por profissionais de enfermagem em ambientes hospitalares: aspectos da interface trabalhadores x equipamentos

The ergonomic design seeks to establish parameters to improve the interface between the technologies (products, systems and environments) and between man (users). Among the many factors involved, there are the activities performed in hospital settings, both by patients and by clinical staff. Accordingly, efforts have been demonstrated biomechanical with a leading occupational problem, especially regarding the transfer of patients.

Algumas potencialidades didáticas do setor trigonal na interface entre história e ensino de matemática

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Bond strength and Raman analysis of the zirconia-feldspathic porcelain interface

The test groups were experimental zirconia, Zirkonzahn zirconia, and Schuetz zirconia. Blocks of partially sintered zirconia were cut into disks (n=20) and then veneered with a feldspathic porcelain. Half of the specimens from each group (n=10) were incubated in 37°C water for 24 hours, and the other half were thermocycled. All the specimens were then subjected to shear testing. The fractured areas were analyzed with optical stereomicroscopy and classified as adhesive, cohesive, or an adhesive-cohesive failure. Spectral patterns were examined to detect bands related to the zirconia and feldspathic porcelain phases. The shear strength data were submitted to 2-way ANOVA. Results No significant differences in shear bond strength were observed among the 3 groups, regardless of whether or not the specimens were thermocycled. Adhesive failures were the most prevalent types of failure (70%). Raman spectra were clearly distinguished for all the materials, which showed the presence of tetragonal and monoclinic phases. Conclusions The controlled production of the experimental zirconia did not influence the results of the bond strength. Raman analysis suggested a process of interdiffusion by the presence of peaks associated with the zirconia and feldspathic ceramics.

A percepção visual visando a continuação gráfica na repetição modular do design de superfície

This article narrates from experiences in the classroom, the use of visual perception in the search for the solution of a basic problem of modular repetition, embodied by the lack of continuity in the elements that shape the design surface. Although Wong (1998) approach emphasizes the intuitive and intellectual approach as different parameters for building visual compositions, we list both as participants in the same focus, where the solution starts from the sensory stimulation.