A clinical perspective on dentin adhesives

The newer generation of dentin adhesives has changed the practice of restorative dentistry. Two features common to most of the bonding restorative materials are the ability to alter, through the use of acidic etching agents, the surface of the dentin and the ability to completely wet and re-infiltrate the altered dentin surface with a hydrophilic polymerizable monomer. The acidic etchants remove or break up the smear layer, partially demineralize and/or alter the mineral in the first few microns of the dentin surface, and expose the collagen fibril network. The hydrophilic adhesive monomers that contain both acidic and methacrylate groups on the same molecule are bifunctional in nature. These monomers are able to infiltrate the demineralized dentin due to their hydrophilic nature and polymerize to encapsulate the exposed collagen fibers. Available products can be divided into two broad categories: systems that contain a low concentration of adhesive monomer diluted in a volatile solvent and systems that use adhesive resins of moderate to high viscosity. Knowledge of the features and properties of dentin adhesives provides the needed rationale for the protocol of application and the proper choice of materials in restorative dentistry.