In vitro, freshly set resin composites often cause what level of cytotoxicity to cells over 24-72 hours?

• A. Severe
• B. Moderate
• C. Minimal
• D. None

Answer: (B)

Freshly set resin composites release unreacted monomers that can be cytotoxic to cultured cells, especially in the first days after curing. Because polymerization isn’t complete at the moment of setting, residual monomers such as TEGDMA, BIS-GMA, UDMA, and HEMA diffuse into the surrounding environment. In a 24–72 hour window, this leaching is enough to noticeably affect cell viability, producing a moderate level of cytotoxicity in many in vitro systems. The effect is typically not catastrophic because some monomer release has declined as curing progresses and because culture conditions dilute and detoxify some of the substances, so cells are affected but not universally destroyed. Hence, moderate cytotoxicity is the most consistent finding for freshly set resin composites over that timeframe.