The promotion of adhesion by the infiltration of monomers into tooth substrates.

The effectiveness of 4-methacryloxyethyl trimellitate anhydride (4-META) on the adhesion of an acrylic rod with etched dentine and enamel was studied. Etching of tooth substrates with a 10% citric acid-3% ferric chloride solution prior to the adhesion proved effective. Monomers with both hydrophobic and hydrophilic groups like 4-META promoted the infiltration of monomers into the hard tissue. The infiltrated monomers polymerized in situ and good adhesion with the tooth substrates took place. The tensile adhesive strength was 18 MPa on the etched dentine. Scanning electron microscopic studies suggested that the monomers possess affinity with the hard tissue. The good adhesion was not provided by the interlocking at the tubules as had been considered previously.