Effect of cast rectifiers on the marginal fit of UCLA abutments

OBJECTIVES: This study assessed the effect of cast rectifiers on the marginal misfit of cast UCLA abutments compared to premachined UCLA abutments. The influence of casting and porcelain baking on the marginal misfit of these components was also investigated. METHODS: Two groups were analyzed: test group - 10 cast UCLA abutments, finished with cast rectifier and submitted to ceramic application; control group - 10 premachined UCLA abutments, cast with noble metal alloy and submitted to ceramic application. Vertical misfit measurements were performed under light microscopy. In the test group, measurements were performed before and after the use of cast rectifiers, and after ceramic application. In the control group, measurements were performed before and after casting, and after ceramic application. Data were submitted to statistical analysis by ANOVA and Tukey's test (a= 5%). RESULTS: The use of cast rectifiers significantly reduced the marginal misfit of cast UCLA abutments (from 25.68mm to 14.83mm;

Estágio atual e perspectivas dos sistemas de união

The establishment of adhesion of restorative materials has been replaced by tooth-conserving adhesive methods. However, dentin bonding is still a challenge, due to the great variation of dentin. Nowadays, there is an amount of adhesives systems, depending on how the steps are accomplished or simplified. There is a trend to move away from multicomponents bonding systems toward simplified; which reduces not only the clinical application time but also the sensitivity of the technique. In spite of this, the micromechanical bonding mechanism offered by the current adhesives must be analyzed under different aspects, in order to decrease a nanoleakage. Therefore, the aim of this review is approach the most recent concepts in adhesive systems and perspectives for the future.O tratamento restaurador com a preservação de estrutura dental está fundamentado na utilização dos sistemas adesivos. Entretanto, a adesão à dentina tem sido um grande desafio para os pesquisadores, por ser um substrato heterogêneo. Atualmente, existe no mercado uma infinidade de marcas comerciais de sistemas adesivos com diferentes composições, métodos de aplicação e número de passos clínicos. Muitas vezes são lançados e retirados rapidamente do mercado, não havendo tempo para uma adequada avaliação clínica. Todos, de uma forma geral, têm como objetivo reduzir o número de passos operatórios e a sensibilidade da técnica adesiva e por sua vez, a microinfiltração. Diante desse questionamento, esta revisão teve como objetivo abordar o estágio atual em que se encontram os sistemas adesivos e quais as perspectivas futuras

Resinas compostas: estágio atual e perspectivas

Os conceitos de promoção de saúde, prevenção e a estética sedimentam a Odontologia atual, que atravessa um período de constante progresso. O surgimento das técnicas adesivas e materiais restauradores são um exemplo disso, devendo porém, sua aplicação clínica ser sustentada por bases científicas conseguidas por meio de pesquisas envolvendo novas técnicas e materiais. Devido a isso a resina composta foi o material mais intensamente pesquisado na última década com o intuito de melhorar suas propriedades negativas. Existem hoje no mercado diversos tipos de resinas, surgidas durante esse processo evolutivo, cada uma tendo suas indicações e limitações. As resinas mais atuais têm demonstrado, que não apenas a quantidade de carga vem sendo alvo de estudos como também seu formato, composição e distribuição, na tentativa de incrementar suas propriedades físicas e ópticas. Por isso, têm se dado bastante enfoque em diversas áreas sempre com o intuito de proporcionar aos pacientes melhores resultados estéticos, biológicos e funcionais. A nanotecnologia, que consiste na manipulação e medida de materiais na escala de abaixo de 100 nanômetros é um exemplo da exploração de novas áreas. Apesar de termos em mãos esse verdadeiro arsenal de materiais, nenhuma resina composta atingiu excelência de um material restaurador ideal. Prevêem-se para o início do milênio, melhoras consideráveis nas formulações das resinas compostas atuais e das novas que surgirão no sentido de melhorar as propriedades dos compósitos resinosos ampliando assim sua indicação.In recent years the odontology suffered changes in some of its concepts, aesthetics and the search for conservatives treatments are part, nowadays, of the routine of the doctor’s offices and odontologic clinics. Because of this the composite resins was the material that has been more intensely searched in the last decade with intention to improve its negative properties. Types of resins, appeared during this evolutive process, each one having its indications and limitations. The most current resins have demonstrated, that not only the amount of load is theme for studies as well as its format, composition and distribution, in the attempt to develop its physical and optic properties. That is the reason why nowadays the nanotechnology, that consists of the manipulation and measure of materials in the scale below of 100 nanometers, is intensively being studied. These new materials present inorganic particles varying of 20-75nm, what diminishes the contraction of polymerization and it promotes satisfactory superficial smoothness. Although of having access to these new materials, no composite resin reached excellency of an ideal restoring material. They are foreseen for the beginning of the milenium, considerable improvements in the formularizations of current composite resins and the news that they will appear in the direction to improve the properties of the composite resins thus extending its indication

Properties of type IV plaster considering variation in the mold/model position during setting stage

Objective: To assess the influence of the position of the mold during the setting stage of type IV stone plaster Durone (Dentsply Ind. Com., Rio de Janeiro, Brazil), on the following properties: surface hardness and roughness. Methods: For the roughness test, two groups (n=6) in the form of pellets were prepared. In the first group, the surface of the base of the device was turned down during the plaster setting stage (N), in the second group this position was inverted, which has been described as an act of capsize it (E). For analysis, a roughness meter with reading precision of 0.01 μm was used. With regard to the hardness analysis, two groups with conical-shaped samples were obtained. The plasters were left to set under the same conditions of the mold/model position described for the previous experiment. Hardness measurement was performed in a durometer with a spherical penetrating tip for Rockwell readout. Three measurements were performed for each test specimen in both tests. Results: The hardness (N - 39.8, standard deviation = 3.3, E - 30.8, standard deviation = 5.6) and roughness data (N - 0.67, standard deviation = 0.17, E - 0.74, standard deviation = 0.13) submitted to the Student’s-t test (5%) showed no statistically significant differences for the roughness test (0.489), but showed statistically significant differences for the hardness test (0.014). Conclusion: The variation in the mold/model position influenced the final characteristics of the specimens in terms of hardness, since those obtained with the capsize technique showed lower surface hardness, whereas for roughness these differences were not statistically significant

Avaliação dos ciclos de polimerização da resina acrílica para base de prótese total

In the present work it was studied the behavior of four water bath curing cycles of heat activated acrylic resin considered as long duration (I – 65ºC for 30 min;50ºC for 23h and 30min; and 100º C for 1h; II- 50ºC for 24h and the rapid cycle), compared to the known long time curing cycle (9 hours for 72ºC) and short curing cycle (1 h for 65ºC; 30 min to elevate at 100º C and 1:00 to 100º C). Analysis consisted of observations and verification of the residual monomer, weight alterations, dimensional, dimensional lineal, porosity and hardness to determine material performance. The results pointed out that residual monomer presented statistical significant differences in the factor storage and interaction among the factors cycle X storage for weight alteration; statistical significant differences for the factor storage for lineal dimensional alterations, without significant differences for hardness. Porosity was verified in minimum degree in the cycle III and in appreciable amount in the cycle IVNo presente trabalho objetivou-se estudar o desempenho de 4 ciclos de polimerização das RAAT: ciclo I - 65°C por 30 min, 50°C por 23h e 30min e 100°C por 1 h; ciclo II - 50°C por 24h e 1 h a 65°C, 30 min para elevar a 100°C e 1 h a 1 00°C, com outros dois, rotineiramente indicados: ciclo III - 9h a 72°C e o ciclo IV – 1 h a 65°C, 30 min para elevar a 100°C e 1 h a 100°C. As observações, para que pudesse ser analisado o desempenho, foram: verificação do monômero residual, alterações de peso e dimensional linear, porosidade e dureza. Os resultados apontaram quanto ao monômero residual, diferenças significantes estatisticamente no fator ciclo; na alteração de peso, o fator armazenagem e a interação entre os fatores ciclo X armazenagem mostraram diferenças estatisticamente significantes; quanto a alteração dimensional linear, diferenças significantes estatisticamente foram observadas para o fator armazenagem; para a dureza não foram verificadas diferenças significantes e as porosidades não foram observadas nos ciclos I e II, no ciclo III em grau mínimo e em quantidade apreciável no ciclo I