The effect of variation in etching times on dentin bonding.

Twelve extracted molars were assigned into four groups of three to observe how different etching times affect the depth of dentin demineralization and the thickness and morphology of the hybrid layer. The four groups were subjected to etching times of 5, 15, 30, and 60 seconds. To study the hybrid layer, another 27 molars were assigned into groups of nine; each group was etched using a different single-bottle bonding agent. In addition, each group was divided into three subgroups, with three different etching times of 5, 15, and 30 seconds. Following the bonding procedure, the specimens were bonded using Z100 composite and processed for observation using a scanning electron microscope. There was a direct correlation between etching time and depth of demineralized zone. The hybrid layer thickness correlated directly to the etching time. Increased etching time demineralized the dentin surface to a depth greater than resin monomers could penetrate, producing a thick, poorly infiltrated hybrid layer. Reducing etching time reduces the depth of the demineralized zone and may be effective for achieving complete penetration and for sealing the dentin surface.