Prevention of toothbrushing abrasion of acid-softened enamel by CO(2) laser irradiation

Objective: The aim of the present study was to evaluate the effect of CO(2) laser irradiation (10.6 mu m) at 0.3 J/cm(2) (0.5 mu s; 226 Hz) on the resistance of softened enamel to toothbrushing abrasion, in vitro. Methods: Sixty human enamel samples were obtained, polished with silicon carbide papers and randomly divided into five groups (n = 12), receiving 5 different surface treatments: laser irradiation (L), fluoride (AmF/NaF gel) application (F), laser prior to fluoride (LF), fluoride prior to laser (FL), non-treated control (C). After surface treatment they were submitted to a 25-day erosive-abrasive cycle in 100 ml sprite light (90 s) and brushed twice daily with an electric toothbrush. Between the demineralization periods samples were immersed in supersaturated mineral solution. At the end of the experiments enamel surface loss was determined using a contact profilometer and morphological analysis was performed using scanning electron microscopy (SEM). For SEM analysis of demineralization pattern, cross-sectional cuts of cycled samples were prepared. The data were statistically analysed by one-way ANOVA model with subsequent pairwise comparison of treatments. Results: Abrasive surface loss was significantly lower in all laser groups compared to both control and fluoride groups (p < 0.0001 in all cases). Amongst the laser groups no significant difference was observed. Softened enamel layer underneath lesions was less pronounced in laser-irradiated samples. Conclusion: Irradiation of dental enamel with a CO(2) laser at 0.3 J/cm(2) (5 mu s, 226 Hz) either alone or in combination with amine fluoride gel significantly decreases toothbrushing abrasion of softened-enamel, in vitro. (C) 2011 Elsevier Ltd. All rights reserved.

Rehardening of acid-softened enamel and prevention of enamel softening through CO(2) laser irradiation

Objectives: The aims of the present study were to investigate whether irradiation with a CO(2) laser could prevent surface softening (i) in sound and (ii) in already softened enamel in vitro. Methods: 130 human enamel samples were obtained and polished with silicon carbide papers. They were divided into 10 groups (n = 13) receiving 5 different surface treatments: laser irradiation (L), fluoride (AmF/NaF gel) application (F), laser prior to fluoride (LF), fluoride prior to laser (FL), non-treated control (C); and submitted to 2 different procedures: half of the groups was acid-softened before surface treatment and the other half after. Immersion in 1% citric acid was the acid challenge. Surface microhardness (SMH) was measured at baseline, after softening and after treatment. Additionally, fluoride uptake in the enamel was quantified. The data were statistically analysed by two-way repeated measurements ANOVA and post hoc comparisons at 5% significance level. Results: When softening was performed either before or after laser treatment, the L group presented at the end of the experiments SMH means that were not significantly different from baseline (p = 0.8432, p = 0.4620). Treatment after softening resulted for all laser groups in statistically significant increase in SMH means as compared to values after softening (p < 0.0001). Enamel fluoride uptake was significantly higher for combined laser-fluoride treatment than in control (p < 0.0001). Conclusion: Irradiation of dental enamel with a CO(2) laser at 0.3J/cm(2) (5 mu s, 226 Hz) not only significantly decreased erosive mineral loss (97%) but also rehardened previously softened enamel in vitro. (C) 2011 Elsevier Ltd. All rights reserved.

The role of surface sealants in the roughness of composites after a simulated toothbrushing test

Objectives: To evaluate the influence of two surface sealants (BisCover/Single Bond) and three application techniques (unsealed/conventional/co-polymerization) on the roughness of two composites (Filtek Z250/Z350) after the toothbrushing test. Methods: Seventy-two rectangular specimens (5 mm x 10 mm x 3 mm) were fabricated and assigned into 12 groups (n = 6). Each sample was subjected to three random roughness readings at baseline, after 100,000 (intermediate), and 200,000 (final) toothbrushing strokes. Roughness (R) at each stage was obtained by the arithmetic mean of the reading of each specimen. Sealant removal was qualitatively examined (optical microscope) and classified into scores (0-3). Data were analyzed by Student`s paired t-test, two-way ANOVA/Tukey`s test, and by Wilcoxon, Kruskal-Wallis and Miller`s test (alpha = 0.05). Results: Z250 groups at baseline did not differ statistically from each other. Unsealed Z350 at baseline had lower R values. All the unsealed groups presented gradual decrease in R from baseline to final brushing. From baseline to the inter-mediate stage, Z250 co-polymerized groups presented a significant reduction in R (score 3). Conventionally sealed groups had no significant changes in R (scores 2-0.8). From baseline to the intermediate stage, the conventionally sealed Z350 Single Bond group had an increase in R (score 1.5). In the final stage, all the conventionally sealed groups presented a reduction in R (scores 0.7-0). Co-polymerized Single Bond groups had a significant reduction in R (scores 2.5-2.7), and co-polymerized BisCover groups an increase in R (scores 2.8-3). Conclusions: At any brushing stage, sealed composites presented superior performance when compared with unsealed composites. (C) 2009 Elsevier Ltd. All rights reserved.

Finite-Element Analysis of Stress on Dental Implant Prosthesis

Background: Understanding how clinical variables affect stress distribution facilitates optimal prosthesis design and fabrication and may lead to a decrease in mechanical failures as well as improve implant longevity. Purpose: In this study, the many clinical variations present in implant-supported prosthesis were analyzed by 3-D finite element method. Materials and Method: A geometrical model representing the anterior segment of a human mandible treated with 5 implants supporting a framework was created to perform the tests. The variables introduced in the computer model were cantilever length, elastic modulus of cancellous bone, abutment length, implant length, and framework alloy (AgPd or CoCr). The computer was programmed with physical properties of the materials as derived from the literature, and a 100N vertical load was used to simulate the occlusal force. Images with the fringes of stress were obtained and the maximum stress at each site was plotted in graphs for comparison. Results: Stresses clustered at the elements closest to the loading point. Stress increase was found to be proportional to the increase in cantilever length and inversely proportional to the increase in the elastic modulus of cancellous bone. Increasing the abutment length resulted in a decrease of stress on implants and framework. Stress decrease could not be demonstrated with implants longer than 13 mm. A stiffer framework may allow better stress distribution. Conclusion: The relative physical properties of the many materials involved in an implant-supported prosthesis system affect the way stresses are distributed.

Bringing people back in: Grassroots approach to peace in Bosnia-Nerzegovina

Peacemaking in Bosnia-Herzegovina is a controversial subject that engaged the political energies of the international community for several years without resolution. While international efforts at peacemaking warrant a critique in their own right, the assumptions that lie behind popular perceptions of peacemaking must also be examined. This article explores the proposition that the promotion of multi-ethnic contact between Bosnian people is at least as important as elections or the reconstruction of political institutions. Indeed, the restoration and development of inter-ethnic relationships, especially at grassroots level, is essential for the establishment of sustainable peace. This article thus focuses on the roles of NGOs (Non-governmental organisations) active at the grassroots level in Bosnia, such as the Centre for Drama Education in Mostar, Project Firefly in Brcko, and the CARE Welcome Project in Sarajevo, which represent a grassroots form of peacemaking that incorporates local knowledge and understandings of the conflict within peace projects.

Geography's emerging cross-disciplinary links: Process, causes, outcomes and challenges

In Australian universities the discipline of Geography has been the pace-setter in forging cross-disciplinary links to create multidisciplinary departments and schools, well ahead of other disciplines in humanities, social sciences and sciences, and also to a greater extent than in comparable overseas university systems. Details on all cross-disciplinary links and on immediate outcomes have been obtained by surveys of all heads of departments/schools with undergraduate Geography programs. These programs have traced their own distinctive trajectories, with ramifying links to cognate fields of enquiry, achieved through mergers, transfers, internal initiatives and, more recently, faculty-wide restructuring to create supradisciplinary schools. Geography's `exceptionalism' has proved short-lived. Disciplinary flux is now extending more widely within Australian universities, driven by a variety of internal and external forces, including: intellectual questioning and new ways of constituting knowledge; technological change and the information revolution; the growth of instrumentalism and credentialism, and managerialism and entre-preneurial imperatives; reinforced by a powerful budgetary squeeze. Geographers are proving highly adaptive in pursuit of cross-disciplinary connections, offering analytical tools and selected disciplinary insights useful to non-geographers. However, this may be at cost to undergraduate programs focussing on Geography's intellectual core. Whereas formerly Geography had high reproductive capacity but low instrumental value it may now be in a phase of enhanced utility but perilously low reproductive capacity.

A disciplina de história da educação em perspectiva histórica : da Faculdade de Filosofia, Ciências e Letras à Universidade Federal do Espírito Santo (1951-2000)

A pesquisa analisa da constituição histórica da disciplina História da Educação ministrada na Faculdade de Filosofia Ciências e Letras do Estado do Espírito Santo, posteriormente incorporada a Universidade Federal do Espírito Santo entre os anos de 1951 e 2000. Investiga a constituição histórica da disciplina, as transformações programáticas, legais e institucionais referentes à disciplina de História da Educação, como também as abordagens historiográficas, periodizações e os conceitos de tempo, história e educação. A fundamentação teórica e metodológica articula-se dialogicamente a partir das construções conceituais e metodológicas de Carlo Ginzburg e Mikhail Bakhtin. A partir dos conceitos de polifonia e dialogismo, comum a ambos, investigou-se as vozes e diálogos impressos nas narrativas da disciplina de História da Educação e seu ensino, sejam em camadas mais superficiais ou profundas, encontradas no corpus documental consultado e analisado, que correspondem a: programas de ensino, transparências, leis, estruturas curriculares, documentos de departamento; resenhas e fichamentos de textos, bibliografia obrigatória e complementar, avaliações e entrevistas. Procurou-se no corpus documental dados aparentemente negligenciáveis – pistas, indícios e sinais – remontar uma realidade histórica complexa e não experimentável diretamente. Ao investigar historicamente a trajetória da disciplina História da Educação e seu ensino a partir dos parâmetros legais, programáticos e institucionais, foi possível perceber que as mudanças mais profundas operadas na disciplina não se originam das legislações e reestruturações curriculares, mas dos locais de produção e socialização do conhecimento histórico. Durante o período analisado, as duas esferas de produção historiográficas que mais influenciaram nas abordagens, periodizações e conceitos de tempo, história e educação da disciplina História da Educação do curso de pedagogia pesquisado foram: a editora responsável pela publicação e divulgação dos Manuais de História da Educação da coleção Atualidades Pedagógicas (1951-1979) e os Programas de Pós-graduação em Educação e História (1980 - 2000). Entre 1951 e finais de 1970 observa-se a influência dos Manuais de História da Educação, na organização e programação do ensino de História da Educação e uma abordagem filosófica voltada para a história das ideias pedagógicas e análises do pensamento de filósofos e educadores sobre a educação e respectivas inserções em doutrinas filosóficas europeias. A partir de 1980 as abordagens de cunho econômico, político e ideológico dos contextos históricos educativos passaram a predominar nos programas de ensino das disciplinas de História da Educação I e II, e vigoraram até meados nos anos de 1990. Na disciplina de História da Educação I a abordagem é marcada por análises do contexto de produção e organização das classes sociais; com relação à disciplina História da Educação II, até meados de 1995, trata da educação brasileira. A partir da abordagem fundamentada na Teoria da Dependência após 1995, os documentos consultados começam a mostrar outras marcas que sugerem uma abordagem voltada para a dimensão política e social, abordando a História da Educação Brasileira, a partir dos movimentos sociais e seus respectivos projetos educacionais.