Last week, the Food and Drug Administration effectively banned the antibacterial chemical triclosan from soaps.

But you can you still find it in your toothpaste.

That’s because the best-selling toothpaste brand, Colgate Total, convinced the F.D.A. that the benefit of triclosan in toothpaste outweighs any risks.

Toothpastes that contain triclosan have been “demonstrated to be effective at reducing plaque and gingivitis,” said Andrea Fischer, an F.D.A. spokeswoman. Before approving the toothpaste in 1997, the agency requested that the Colgate-Palmolive company conduct toxicology studies, and the F.D.A. ultimately decided it was safe and effective.

“Based on scientific evidence, the balance of benefit and risk is favorable for these products,” Ms. Fischer said on Tuesday.