Resin adhesion to carious dentin.

PURPOSE: To investigate the microtensile bond strength (microTBS) of a self-etching priming adhesive system to normal, caries-affected and caries-infected dentin, and to observe the ultrastructure of the resin-dentin interface by transmission electron microscopy (TEM). MATERIALS AND METHODS: Twelve extracted human molar teeth with deep occlusal caries were stained with caries detector solution and ground flat occlusally. The red-stained soft dentin was classified as caries-infected. The surrounding discolored dentin was classified as caries-affected dentin. The surrounding normal dentin served as a control. The entire flat surface was bonded with Clearfil Liner Bond 2V (CV) and covered with resin composite to form a composite crown 5 mm high. One day later the specimens were serially sectioned vertically into multiple slabs 0.8 mm thick. Under microscopic observation, the specimens were divided into normal or caries-infected or caries-affected dentin. These regions were isolated by cutting away the remaining dentin to form hour-glass shapes with the smallest surface area at the test site. After measuring the areas, the specimens were fixed to a microtensile tester and pulled under tension to failure. Additional slabs that were not used for bond strength tests were processed for TEM. Bond strength data were analyzed by Kruskal-Wallis one-way ANOVA and Student-Newman-Keuls multiple comparisons. RESULTS: The microTBS of CV to normal, caries-affected and caries-infected dentin were 45 +/- 10 MPa, 30 +/- 10 MPa, 10 +/- 5 MPa, respectively. TEM images showed that CV formed thin hybrid layers that were less than 1 microm thick in normal dentin, but that were between 6-8 microm thick in caries-affected dentin. Bacteria were only sparsely observed in the dentin tubules of bonded caries-affected dentin. However, in caries-infected dentin, an unusual interface was seen in which carious bacteria within disorganized non-banded collagen fibrils could be seen embedded by the adhesive. The hybrid layer in caries-infected dentin was found to be 30-60 microm thick.

Resin diffusion through demineralized dentin matrix / Difusäo de resina através da matriz de dentina desmineralizada

Este trabalho focaliza os aspectos que podem afetar a permeabilidade de resinas adesivas na matriz de dentina desmineralizada durante o desenvolvimento do processo adesivo. Os efeitos da umidade de superfície, respectivamente aos sistemas adesivos e aos problemas relacionados com a formaçäo incompleta da camada híbrida säo apresentados

Comparative SEM and TEM observations of nanoleakage within the hybrid layer / Observações comparativas SEM e TEM da infiltração dentro da camada híbrida

Must adhesive interface studies have involved SEM demonstration of the penetration of adhesive resins into desmineralized dentin surfaces with subsequent creation of hybrid layers. Nanoleakage is a term that describes the diffusion of small ions or molecules within the hybrid layer in the absence of gap formation. The present microscopic study examined the nanoleakage of the hybrid layer using a silver nitrate staining technique. Adhesive dentin sandwiches, which were immersed in a silver nitrate solution, were prepared for both SEM and TEM examination using both the Clearfil Liner Bond and All-Bond 2 adhesive systems. Both systems demonstrated silver accumulation within the hybrid layers. Clearfil Liner Bond System showed scattered silver particles at the bottom two-thirds of the hybrid layer by both SEM and TEM observation, whereas All-Bond 2 revealed stained fiber-like structures within the full thickness of the hybrid layer. To evaluate the quality of the hybrid layer, the utilization of tracer molecules such as silver nitrate that are detectable by both SEM and TEM is proposed. It is important to determine the location and morphology of these nanometer-sized porosities that may permit the hydrolysis of collagen fibers and degradation of adhesive monomers

Determinaçäo da resistência adesiva a dentina através de um dispositivo de micro-traçäo / Bond strengh to dentine determine by a new develloped micro-tensile testing device

A resistência de uniäo a dentina DO Scotchbond MP e Variglass foi determinada utilizando-se um novo método do ensaios por micro-traçäo. Esta nova metodologia permite testar a resistência adesiva a pequenas áreas através do desgaste de secçäo transversal dos espécimes até 0,5 milímetros quadrados. A principal observaçäo deste estudo foi que a resistência a traçäo foi dependente da superfície da área adesiva. As superfícies adesivas variaram de 0,5 a 5,0 milímetros quadrados o que é muito menor do que as superfícies adesivas utilizadas rotineiramente em testes de laboratório. Uma relaçäo inversa entre a resistência a traçäo e a área de superfície adesiva foi observada para ambos os materiais. Quando utilizaram-se as menores áreas, Scotchbond MP atingiu valores de até 46 MPa e Variglass resultou em valores de até 34 MPa