Bonding BisGMA to dentin--a proof of concept for hydrophobic dentin bonding

The use of TEGDMA as a diluent comonomer in the formulation of hydrophobic adhesives for ethanol wet-bonding is a concern, due to its leaching potential, higher water sorption, and bio-incompatibility. This study tested the hypothesis that hydrophobic bonding to acid-etched dentin may be accomplished with the use of ethanol-solvated BisGMA only. Phosphoric-acid-etched, oxalate-occluded, deep coronal dentin bonded under 20 cm water pressure with experimental BisGMA adhesives by ethanol wet-bonding exhibited tensile strengths that were not significantly different from that achieved with OptiBond FL bonded according to the manufacturer-recommended protocol, with similar acid-/base-resistant hybrid layers, resin tags, and nanoleakage distribution. Ethanol replacement of water-saturated dentin produced wider interfibrillar spaces, more extensive shrinkage of the collagen fibrils, and narrower hybrid layers. Experimental BisGMA adhesives provide the proof of concept that relatively hydrophobic resins may be coupled to acid-etched dentin by increasing its hydrophobic characteristics via ethanol replacement. They should be further optimized before clinical application.