Bonding of restorative materials to dentine: the present status in the United States

In the United States there is a new method for obtaining strong adhesive bonding between composite resins and both dentine and enamel. This experimental procedure has not reached commercial availability but several manufacturers are making preparations to supply it. The procedure comprises the sequential application of three compounds in solution. The first is an aqueous solution of ferric oxalate which conditions the dentine or enamel surface. The second is an acetone solution of a surface-active compound such as N-phenylglycine. After the acetone evaporates the excess compound is removed by the use of more solvent. The next step is the application of an acetone solution of a monomer that resembles the BIS-GMA used in composite resins but which has certain important differences. The short label for it is 'PMDM' because it is the reaction product of pyromellitic dianhydride and 2-hydroxyethylmethacrylate. When the volatile solvent quickly evaporates a thin layer of the PMDM remains on the treated dentine or enamel surface. Composite resins will then adhere strongly to these prepared surfaces, giving tensile adhesive bond strengths up to 14 MN/m2. Bond strengths of this magnitude have, on at least ten occasions, been sufficient to break pieces of dentine out of the surfaces of the extracted teeth during testing. The bond strengths to dentine obtained by this method in the laboratory are much higher than the strengths obtained with commercially available materials. The new technique is more complicated than those now in use. This creates a challenge to the dental manufacturers who must produce and supply these materials in a storage-stable form and who must provide directions that will lead to their proper use and the best results.(ABSTRACT TRUNCATED AT 250 WORDS)