Bonding behavior of restorative materials in primary teeth submitted to erosive challenge − Evidence from an in vitro study

Purpose: To evaluate bond stability of restorative materials to eroded primary teeth after aging. Methods: 120 primary molars were assigned into 12 groups, in according to substrate – enamel or dentin, precondition of substrate – sound or eroded, and restorative material – resin composite/adhesive system-RC, high-viscosity glass ionomer cement–HVGIC or resin-modified GIC–RMGIC. Eroded groups were subjected to erosive challenge prior to bonding procedures. Polyethylene tubes were placed on flat surfaces of substrates and filled up with one of materials. After 24 h, half of the specimens were submitted to microshear bond strength (BS) test, and the other half after 12 months. Results: Generally, sound substrates resulted in higher BS values than eroded ones, with exception of HVGIC that obtained similar performance in both substrates. Furthermore, the storage period negatively influenced BS values for RC groups on dentin assessment. The other groups did not show reduction in BS values after 12 months. RC showed better bonding performance than others materials. Conclusion: Previously eroded substrates result in the worst performance of RC and RMGIC. Moreover, the water storage affects the bonding stability of RC to dentin. On the other hand, HVGIC is not affected by precondition of substrate neither storage

Transport of solutes through calix[4]pyrrole-containing cellulose acetate films

Films of cellulose acetate containing different concentrations of meso-octamethyl-porphyrinogen (calix[4]pyrrole) were prepared and characterized using UV-vis and FTIR spectroscopy, DSC and SEM. Incorporation of calix[4]pyrrole into cellulose acetate leads to a decrease in the degree of hydrophilicity of the polymeric matrix. However, a slight increase in the percentage of water uptake of the polymer is found with an increase of the initial amount of calix[4]pyrrole in the composite composition. This effect can be related to the plasticizing effect that the calix[4]pyrrole provokes in the cellulose acetate. A comparative study of transport parameters of oxygen and some non-associated electrolytes (sodium, copper(II) and nickel chlorides) was carried out. The diffusion coefficients of molecular oxygen through cellulose acetate films decrease with an increase of the concentration of calix[4]pyrrole in the composite films. The transport (diffusion and permeation) of the above mentioned electrolytes through a set of composite films shows a decrease of permeability and diffusion coefficients with an increase of calix[4]pyrrole concentration. Such behaviour is typical of systems where interactions between the polymer and diffusing species occur. However, from the analysis of the distribution coefficient, it was found that those interactions are only dependent on the calix[4]pyrrole content for 2:1 electrolytes.http://www.sciencedirect.com/science/article/B6TWW-4NFR5CN-3/1/c8e93beea778c4b90e5b2ead92581bb