Control del colapso del colágeno: sistemas autograbadores / Control of the collagen network collapse: self-etching bonding systems

Con el grabado ácido se obtiene un frente de desmineralización con un grosor diferente y mayor que el frente de infiltración de la resina, dando lugar al colapso del colágeno. Para solventar el problema aparecieron los sistemas autograbadores que a medida que desmineralizan van infiltrando la dentina. Se caracterizan los autograbadores dentro de los sistemas adhesivos y se analizan las fuerzas de adhesión que producen y los factores de que depende la profundidad de desmineralización de sus imprimadores (AU)

When dentin is etching the former (depth of dentin demineralization) excess the latter (depth of dentin diffusion / impregnation), a zone of hydroxyapatite depleted collagen fibers is left exposed, i.e., not resin infiltrated and nonhybridized. To avoid this, one option are the self-etching dentin bonding systems, that decalcify the inorganic component and infiltrate the collagen fibers at the same time by the action of acidic primers. In this article, the selfetching systems are characterized, and, their interfacial bond strength and the depth of demineralization of acidic primers are analysed (AU)

Bonding of resin to dentin. Interactions between materials, substrate and operators.

OBJECTIVES: The general aim of this thesis was to identify and study factors that affect bonding between resin and dentin, including operator variability. MATERIALS AND METHODS: Bonding sites were generated in vivo and in vitro and compared using SEM. The effects of experimental water- or acetone-based primers on shear bond strength to dentin were studied in vitro. Fourier transform infrared spectroscopy was used to establish any detrimental effects from water on polymerization by determining the degree of conversion of thin films of resin. The interaction between phosphoric acid and dentin was analyzed by measuring calcium leaching by use of atomic absorption spectroscopy. Bond strength of composite resin was measured to dentin with various degrees of demineralization. Gap formation adjacent to composite restorations in standardized dentin cavities was studied in vitro by confocal microscopy. RESULTS: A similar morphological appearance was found for bonding sites generated in vitro vs. in vivo. An acetone-based primer was more dependent on a moist bonding technique than was a water-based system. However, water might influence bonding by interfering with the polymerization of the resin. Calcium leaching from dentin can be predicted by use of a solubility phase diagram. No correlation could be established between calcium leaching and bond strength. Gap formation was more dependent on the operator than the choice of material. A simplified all-in-one adhesive showed less operator variability compared to more complex bonding systems. CONCLUSIONS: In vitro bond testing may well indicate the outcome of in vivo trials. The solvents used in bonding agents will influence the performance and, presumably, technique sensitivity. Water rinse time after etching might be a more important consideration than etch time. In spite of the relative importance of the results presented above, the outcome of the multi-operator trial could not be predicted.

In vitro study on the fatigue limit of single-lap joints.

Lasting adhesion between attachment and tooth is an essential prerequisite for all adhesive techniques in dentistry. However, the maximum static fatigue load is only one material-related parameter for the quality of this adhesion. Another parameter is the dynamic loading capacity of a bonded joint, which was determined in the present study for Dual adhesive resin by means of fatigue testing. This revealed a significant correlation between the recorded static and dynamic fatigue load and the gap width, which varied between 0.01 mm, 0.15 mm and 0.5 mm in the experimental setup. At 18.8 MPa, the median gap width of 0.15 mm yielded the highest static resistance, with a dynamic resistance 15% below this figure. Both the smaller and the larger gap showed significantly lower static fracture strengths (0.01 mm: 13.6 MPa; 0.5 mm: 13.7 MPa), whereas a dynamic load on the 0.01 mm bond, in contrast to the 0.5 mm bond, led to only a 5% reduction in bonding strength.

The science of bonding: from first to sixth generation.

BACKGROUND: Adhesive dentistry has revolutionized restorative dental practice during the past 30 years. Improved adhesive materials have made resin-based composite restorations more reliable and long-standing. CLINICAL IMPLICATIONS: This article reviews the evolution of bonding from the first generation to current bonding materials. It discusses the composition and effectiveness of the various iterations. Current products are highlighted to improve clinical use and performance of the materials.

Resistências de uniäo de cinco cimentos utilizados em ortodontia / Bond strength of five cements for orthodontic use

A resistência de uniäo de cinco cimentos disponíveis no mercado e utilizados na fixaçäo de bráquetes ortodônticos (Concise Ortodôntico, Fuji Ortho LC, Vitremer, Dyract e Transbond XT) foi estudada. Foram utilizados 50 dentes pré-molares superiores humanos, hígidos, recém extraídos, conservados em soluçäo de Cloramina T a 1 por cento e água até o momento de sua utilizaçäo. Os dentes tiveram suas raízes seccionadas em nível da junçäo cemento-esmalte, sendo posteriormente incluídos em resina epóxica, com auxílio de matrizes de silicona, e depois armazenados em água deionizada até o momento da fixaçäo dos bráquetes. Previamente à fixaçäo foi realizada profilaxia com pasta de pedra pomes e água, utilizando-se taça de borracha em motor de baixa rotaçäo. Os materiais foram utilizados de acordo com as instruçöes dos respectivos fabricantes. Após fixaçäo dos bráquetes, os corpos de prova foram armazenados em água deionizada à 37ºC durante 24 horas. Os testes de cisalhamento foram realizados com auxílio de uma Máquina de Ensaios Universal Kratos, com velocidade de 0,5mm/minuto. Os resultados foram analisados estatisticamente, o que permitiu concluir que: a) todos os cimentos atingiram valores aceitáveis à prática ortodôntica; b) com exceçäo dos grupos Concise Ortodôntico x Transbond XT e Fuji Ortho LC x Transbond XT, houve diferença estatística significante entre todos os outros grupos, c) as falhas adesivas ocorreram, na maioria das vezes (66 por cento), na interface cimento/bráquete