CYTOTOXICITY OF RETROFILL MATERIALS

Dentin bonding agents reduce microleakage and enhance marginal adaption of composite resin restorations. These characteristics are advantages for their use as an endodontic retrofilling material. Because these materials will be in direct contact with vital tissues, their cytotoxic potential must be evaluated before clinical use. It was the purpose of this study to evaluate the cell cytotoxicity of amalgam, Caulk Universal Bond, Gluma, 35% HEMA, Morita Clearfil, Scotchbond 2, Super EBA, Tenure, and Tenure 5-4. VERO cells were grown in RPMI-1640 medium and cell monolayers were prepared by incubating 15 ml of the cell suspension in 60-mm culture dishes at 37-degrees-C in 5% CO2. Twelve milliliters of a medium-agarose mixture containing 1 % neutral red vital stain were overlayed onto the cell layer and allowed to solidify. The materials were directly exposed to the agarose overlays by inverting 6.0-mm diameter polypropylene capsules containing the cured and liquid sample materials either immediately (0 time) or after placement in phosphate-buffered saline with 1% gentamicin for 7, 15, or 30 days. Cytotoxicity was determined by measuring the zone of killed cells around the sample 24 h after placement on the agarose. Cytotoxicity was determined by measuring the zones of cell inhibition at 24 h and at 7, 15, and 30 days. Initially, all of the materials were found to be cytotoxic, except amalgam and the Tenure components. The dentin bonding primers showed a mean zone of inhibition of 13.2 mm and the cleansers a 40.0-mm zone. Amalgam demonstrated increasing cytotoxicity: 0.0 mm at 24 h to 12.0 mm at 30 days. The resin components displayed zones of inhibition of 14.9 mm at 24 h, decreasing to 7.1 mm at 30 days. Tenure's Visar seal and the experimental dentin bonding agent Tenure 5-4 exhibited no zones of inhibition, with the Tenure A and B solutions showing a mean zone of inhibition of 7.3 mm at 24 h, falling to 0.0 mm at 30 days. HEMA (35%), when tested alone, showed a mean zone of 16.7 mm at 24 h. It can be concluded that some dentin bonding agents are cytotoxic as evaluated by these studies. With most agents, however, cytotoxicity decreased over time.