Although various adhesive resins for dentin have been developed and used clinically, most attention has been directed to adhesion-promoting monomers and pre-treatment agents. The role of polymerization initiator systems in bonding has been overlooked. The purpose of this work was to study the role of initiators from the viewpoint of interfacial initiation of polymerization in dentin bonding. The bond strength between dentin and methyl methacrylate resin was significantly improved by a possible interfacial initiation with (1) the combination of ferric chloride, adsorbed onto dentin, and oxidized tri-n-butylborane (TBBO) and (2) the addition of tertiary butyl peroxymaleic acid (containing a carboxylic acid group, which has an affinity with dentin) to chemically- or light-activated initiator systems.

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Counterion activity coefficients in solutions of dextran sulfate with and without added salts were determined potentiometrically by using a cation‐exchange membrane and a sodium glass electrode. Dextran sulfate was shown to interact with monovalent cations in the order of preference: K+ > Cs+ > Na+ > Li+, whereas no specificity was found for bivalent cations. On the basis of light‐scattering measurements, the expansion of the dextran sulfate polyion in solutions of alkali metal salts was found to fall in the same order as the counterion activity coefficients in salt‐free solutions. It was also shown that the dextran sulfate polyion assumes a more extended conformation in magnesium chloride solution than in calcium chloride. These results were substantiated by measurements of solution viscosities.

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