Metal chloride primers for bonding dentine with tri-n-butylborane-initiated luting agents

Objectives: The bonding of resin to dentine is dependent largely on surface modifications. The purpose of the present study was to test the hypothesis that a role of the metal chlorides used as primers is to initiate polymerization of resin at the resin–dentine interface, thereby affecting bond strength. Methods: Nine primers were evaluated, comprising aqueous 2-hydroxyethyl methacrylate (HEMA) solutions containing AlCl3, CeCl3, CoCl2, CuCl2, FeCl3, NiCl2, MgCl2, SnCl2 or ZnCl2, respectively. One of the two luting agents (Super-Bond resin) consisted of methyl methacrylate (MMA), 4-methacryloyloxyethyl trimellitate anhydride (4-META) and tri-n-butylborane (TBB) initiator. The other luting agent (MMA–TBB resin) consisted of MMA and TBB without 4-META. Extracted bovine teeth were ground to expose the dentine, etched with an aqueous solution of 10% phosphoric acid, primed, and then bonded with stainless-steel rods; tensile bond strengths were determined after 1-day immersion in water. Data were analysed by ANOVA and Duncanʹs new multiple range test (P<0.05). Results: Four of the metal chlorides (CuCl2, FeCl3, MgCl2 and ZnCl2) enhanced the bond strengths of MMA–TBB resin to dentine. With Super-Bond resin, maximum bond strengths of 15.6 MPa and 19.0 MPa were recorded with primer containing 2.0×10−5 mol g−1 FeCl3 and 2.0×10−6 mol g−1 CuCl2, respectively. Conclusions: Bonding techniques, combining the use of either cupric primer or ferric primer with 10% phosphoric acid etchant may be suitable for application in seating resin-bonded prostheses with TBB-initiated luting materials.