Dentin bonding in perspective.

Forming a bond to dentin has been a great challenge. Dentin is a vital tissue composed of organic material and water in addition to the inorganic content. Operative procedures on dentin produce a loosely-bound surface of unorganized material known as the "smear layer". For optimum bonding to occur, this layer needs to be removed or altered. A dentin bonding agent should be biocompatible and should form an instantaneous bond, strong enough to resist the forces of polymerization shrinkage, fInishing · procedures and thermal expansion and contraction. The bond should be stable and impervious over time. The clinical procedures should be convenient, with minimal "technique sensitivity" and should attain a consistently superior bond. Excitement surrounds the latest generation of dentin bonding agents which now show in vitro bond strengths approaching those of etched enamel. One system utilizes hydrophilic and hydrophobic monomers. Hydroxyethyl methacrylate (HEMA) and maleic acid are used to solubilize the dentin surface before coating it with resin bonding agent. Another system uses a treatment sequence starting with aluminum oxalate as a mordant, followed by a surface active compound such as N-phenylglycine and glycidyl methacrylate in acetone, and then by an acetone solution of PMDM (the adduct of pyromellitic acid dianhydride and 2hydroxyethyl methacrylate). For some years; a third system has been available in Europe. This system cleanses dentin with ethylene diamine tetra acetic acid (EDTA), then primes it with an aqueous mixture of HEMA and glutaraldehyde (Gluma).