Influence of the hydrostatic pulpal pressure on droplets formation in current etch-and-rinse and self-etch adhesives: A video rate/TSM microscopy and fluid filtration study

Objectives. The aim of this study was to investigate the droplet formation using a real-time/confocal microscopy technique, when different self-etching and etch-and-rinse adhesives were applied in the presence or absence of pulpal pressure. Resin-dentin permeability (%P) was also evaluated. Methods. Optibond FL, Silorane adhesive, Scotchbond 1XT, G-Bond and DC-Bond were bonded in the presence or in absence of simulated pulpal pressure. A fluid-transport model was used to measure the water permeability through resin-bonded dentin. Half of the specimens bonded in the presence of the hydrostatic pulpal pressure (20 cm H2O) were light cured, whereas the remnant half received no light curing. The same was done with the half of the specimens bonded under no pulpal pressure. The specimens were investigated under a confocal TSM. Results. Optibond FL and G-Bond had the lowest dentin permeability. Optibond FL adhesive showed few water droplets on the polymerized external surface and within the resin-dentin interface. G-Bond showed static interfacial globular-like droplet formation. DC-Bond and Scotchbond 1XT were the most water permeable adhesives both in the presence and in absence of pulpal pressure. A dynamic interfacial non-globular-like droplet formation was observed. Severe droplet formation was observed on the polymerized external surface. Significance. The presence of the pulpal pressure may cause increasing in fluid filtration and droplet formation in simplified adhesives containing HEMA. The adhesives containing 4-META (G-Bond) may be affected by static phase separation but by very low osmotic droplets formation and water permeability. The three-step adhesives are less affected by these problems. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.