CYTOTOXICITY OF RETROFILL MATERIALS

Dentin bonding agents reduce microleakage and enhance marginal adaptio n of composite resin restorations. These characteristics are advantage s for their use as an endodontic retrofilling material. Because these materials will be in direct contact with vital tissues, their cytotoxi c potential must be evaluated before clinical use. It was the purpose of this study to evaluate the cell cytotoxicity of amalgam, Caulk Univ ersal 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 suspens ion in 60-mm culture dishes at 37-degrees-C in 5% CO2. Twelve millilit ers of a medium-agarose mixture containing 1 % neutral red vital stain were overlayed onto the cell layer and allowed to solidify. The mater ials were directly exposed to the agarose overlays by inverting 6.0-mm diameter polypropylene capsules containing the cured and liquid sampl e materials either immediately (0 time) or after placement in phosphat e-buffered saline with 1% gentamicin for 7, 15, or 30 days. Cytotoxici ty was determined by measuring the zone of killed cells around the sam ple 24 h after placement on the agarose. Cytotoxicity was determined b y 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, exce pt amalgam and the Tenure components. The dentin bonding primers showe d a mean zone of inhibition of 13.2 mm and the cleansers a 40.0-mm zon e. 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 zon es of inhibition, with the Tenure A and B solutions showing a mean zon e 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 ca n be concluded that some dentin bonding agents are cytotoxic as evalua ted by these studies. With most agents, however, cytotoxicity decrease d over time.