The ability of a material to stick to dentine. Because traditional resin-based materials are hydrophobic and dentine, which is 70% organic, is also primarily hydrophilic, a bifunctional monomer such as HEMA is used which has a hydrophilic terminal capable of intimately bonding with the dentine surface and a hydrophobic terminal which can co-polymerize with the resin component of the restorative material. The surface layer of the dentine is usually first conditioned to remove the loose smear layer and some of the mineral content, to expose the collagen fibres. The adhesive agent can then form a micro-mechanical bond around the exposed dentine surface (hybrid layer).
Moszner N., Salz U., Zimmermann J. Chemical aspects of self-etching enamel-dentin adhesives: a systematic review. Dent Mater2005;21(10):895–910.