Many bonding agents are ______ to cells in vitro.

• A. Biocompatible
• B. Hypoxic
• C. Inert
• D. Cytotoxic

Answer: (D)

Bonding agents can release residual monomers and additives when they come into contact with cultured cells, and those substances can damage or kill cells in vitro. This cellular harm seen in laboratory tests is what cytotoxicity describes, making it the best fit for how these materials behave in a controlled cell culture setting. The unpolymerized methacrylates and solvents can diffuse into cells and disrupt metabolism or membranes, leading to reduced viability. In clinical situations, curing, dilution by bodily fluids, and tissue barriers can lessen these effects, so in vitro cytotoxicity doesn’t always directly predict how a material will perform in the mouth. Terms like biocompatible would imply no harm in the lab, inert would imply no interaction at all, and hypoxic refers to low oxygen conditions, which isn’t the issue here.