Effects of exposure to 4-META/MMA-TBB resin on pulp cell viability

Adhesive restorative systems have expanded the range of possibilities for direct pulp-capping technique, with evidences of clinical success in vital pulp therapy. However, quite few studies have described the direct responses of pulp cells following the application of resinous materials to pulp exposure. To address this issue, effects of exposure to an adhesive resin, 4-methacryloxyethyl trimellitate anhydride/methyl methacrylate-tri-n-butyl borane (4-META/MMA-TBB) resin on cellular activity were investigated in an established rat dental pulp cell line (RPC-C2A). RPC-C2A cells were cultured on normal plastic plates or the disks prepared from 4-META/MMA-TBB resin (Super Bond C&B) in a-MEM containing 10% FBS. After 3, 7 and 14 days, DNA content and alkaline phosphatase (ALP) activity were measured. Total RNA in each group was extracted and RT-PCR analysis was performed. Moreover, the live cell ratio was also evaluated by cytotoxicity assay after treatment with various concentrations of 4-META/MMA-TBB. At day 3, 7 and 14, amount of DNA and ALP activity of the cells on normal plastic plates and the one on the 4-META/MMA-TBB were comparable. Cells of both groups expressed mRNA of type I collagen (Coll), ALP, osteopontin (OPN), osteocalcin (OC), and bone morphogenetic protein (BMP-2). Furthermore, 4-META/MMA-TBB (10(-1)% or less) did not influence dead cell ratio in the confluent state. According to the results of these in vitro studies, exposure to this resinous material would not induce cytotoxic response in the pulp cells.