Effects of surface-active resins on dentin/composite bonds.

Effective dentin bonding systems based on para-PMDM diadduct of pyromellitic dianhydride and 2-hydroxyethyl methacrylate (HEMA) have been developed (Bowen et al., 1982). Para-PMDM, a solid of limited solubility, is usually applied from an acetone solution to dentin that has been preconditioned with acid and N-phenylglycine. The feasibility of using a liquid, surface-active bonding resin to substitute for or to supplement para-PMDM was explored. Mono(2-methacryloyloxy)ethyl phthalate (MMEP), a liquid, monofunctional homolog of para-PMDM (derived from the reaction of phthalic anhydride with HEMA) was used to formulate several bonding resin systems and solutions. Dentin surfaces were pretreated according to several variations of a three-step bonding protocol involving sequential application of 6.8 w/o ferric oxalate in 2.5 w/o HNO3, N-phenylglycine in acetone, and an experimental bonding resin before placement of a chemically cured composite restorative material. Tensile bond strengths were tested after 24 h storage in distilled water at 23 degrees C. The results suggest that solutions based on MMEP and/or para-PMDM in acetone or in other monomers, especially those containing HEMA, can effectively promote bonding to dentin. A new mechanism for the observed self-polymerization of MMEP or para-PMDM with N-phenylglycine is proposed.