Shear bond strength of metallic and ceramic brackets using color change adhesives.

OBJECTIVE: To determine the shear bond strength of orthodontic brackets using color change adhesives that are supposed to aid in removing excess of bonding material and compare them to a traditional adhesive. METHODS: Ninety metallic and ninety ceramic brackets were bonded to bovine incisors using two color change adhesives and a regular one. A tensile stress was applied by a universal testing machine. The teeth were observed in a microscope after debonding in order to determine the Adhesive Remnant Index (ARI). RESULTS: The statistical analysis (ANOVA, Tukey, and Kruskall-Wallis tests) demonstrated that the mean bond strength presented no difference when metallic and ceramic brackets were compared, but the bond resistance values were significantly different for the three adhesives used. The most common ARI outcome was the entire adhesive remaining on the enamel. CONCLUSIONS: The bond strength was similar for metallic and ceramic brackets when the same adhesive system was used. ARI scores demonstrated that bonding with these adhesives is safe even when ceramic brackets were used. On the other hand, bond strength was too low for orthodontic purposes when Ortho Lite Cure was used.

Shear bond strength of metallic and ceramic brackets using color change adhesives

OBJECTIVE: To determine the shear bond strength of orthodontic brackets using color change adhesives that are supposed to aid in removing excess of bonding material and compare them to a traditional adhesive. METHODS: Ninety metallic and ninety ceramic brackets were bonded to bovine incisors using two color change adhesives and a regular one. A tensile stress was applied by a universal testing machine. The teeth were observed in a microscope after debonding in order to determine the Adhesive Remnant Index (ARI). RESULTS: The statistical analysis (ANOVA, Tukey, and Kruskall-Wallis tests) demonstrated that the mean bond strength presented no difference when metallic and ceramic brackets were compared but the bond resistance values were significantly different for the three adhesives used. The most common ARI outcome was the entire adhesive remaining on the enamel. CONCLUSIONS: The bond strength was similar for metallic and ceramic brackets when the same adhesive system was used. ARI scores demonstrated that bonding with these adhesives is safe even when ceramic brackets were used. On the other hand, bond strength was too low for orthodontic purposes when Ortho Lite Cure was used.

OBJETIVO: determinar a resistência adesiva à tração de braquetes ortodônticos usando resinas coloridas que se propõem a ajudar na remoção do excesso de material adesivo e compará-las com um adesivo tradicional. MÉTODOS: Noventa braquetes metálicos e 90 cerâmicos foram colados com dois adesivos coloridos e com um adesivo tradicional em incisivos inferiores bovinos, sendo aplicada tração com uma máquina de ensaios universal. Após a descolagem, os dentes foram observados em microscópio para a determinação do índice de adesivo remanescente (ARI). RESULTADOS: a análise estatística (testes ANOVA, de Tukey e de Kruskall-Wallis) demonstrou que a força de união média foi significativa entre os adesivos usados. Os ARIs mais comuns foram aqueles onde o adesivo permaneceu no esmalte. CONCLUSÃO: a resistência adesiva foi similar entre braquetes metálicos e cerâmicos quando o mesmo adesivo foi usado. Os resultados do ARI demonstraram que esses adesivos são seguros, mesmo com o uso de braquetes cerâmicos. A resistência adesiva foi muito baixa para Ortodontia no grupo colado com Ortho Lite Cure.

Influence of heating rate on the microstructure of glass foams.

In the present study, glass foams made of ground soda-lime glass obtained from transparent glass bottles and dolomite were investigated. The objective of this paper was to evaluate the influence of the heating rate on the microstructure of the obtained material and on its properties. The technological characterization of the ceramic bodies involved the determination of the volumetric expansion and average diameter of the pore. The microstructure was investigated by optical microscopy and scanning electron microscopy. Experimental results showed that the heating rate influenced both the volumetric expansion and the average diameter of the pore. Lower heating rates resulted in lower volumetric expansions since more CO(2) escaped from within the ceramic body.

Recycling of iron foundry sand and glass waste as raw material for production of whiteware.

The purpose of this study was to evaluate the production feasibility of triaxial whiteware using sand from cast iron moulds as a raw material instead of silica, and recycled glass in place of feldspar. Formulations were prepared using sand, glass waste, and white-firing clay such that only 50% of the composition was virgin material (clay). The ceramic bodies were formed by pressing and fired at different temperatures (between 1100 and 1300 degrees C). Specimens were characterized in terms of green density prior to firing; and their flexural strength, linear shrinkage, and water absorption were measured after firing. The microstructure was determined by scanning electron microscopy. Possible environmental impacts of this recycling process were also evaluated, through solubility and leaching tests, according to Brazilian standards. Gaseous emissions during the firing process were also analysed. The results showed that it is possible to produce triaxial ceramics by using such alternative raw materials.