Adhesive bonding to dentin with ferrous chloride primers and tri-n-butylborane-initiated luting agents

A variety of surface modifications with metal chlorides has been used to enhance the bond of resins to dentin. This study investigated the effectiveness of ferrous chloride in terms of the initiation of polymerization in dentin bonding. The efficacy of experimental dentin primers was evaluated via the bonding of two luting agents to dentin. The 16 primers evaluated were ferrous chloride (FeCl2) aqueous solutions, eight with and eight without 35% 2-hydroxyethyl methacrylate (HEMA). The concentrations of FeCl2 in the primers ranged from 2.0 x 10(-6) to 5.0 x 10(-4) mol/g. One luting agent (Super-Bond C&B) consisted of methyl methacrylate (MMA), 4-methacryloyloxyethyl trimellitate anhydride (4-META), and tri-n-butylborane (TBB) initiator. The other luting agent was prepared with MMA and TBB, but without 4-META. Bovine dentin surfaces were flattened, etched with an aqueous solution of 10% phosphoric acid, primed, and then bonded with stainless steel rods. Tensile strengths of the bonded specimens were measured after one-day immersion in water. Tensile testing revealed that the bond strength was influenced by the application of FeCl2 and/or HEMA. The maximum bond strength of 33.0 MPa was recorded with the use of primer containing FeCl2 and HEMA in MMA-TBB resin. In the case of Super-Bond, only surface treatment of dentin with aqueous primers containing 5.0 x 10(-5) to 2.0 x 10(-4) mol/g ferrous chloride resulted in bond strength values above 22.0 MPa. This bonding technique, combining the use of ferrous chloride primer with Super-Bond resin, may potentially be applied for seating resin-bonded restorations.