View photos of the medicinal plant Bistorta bistortoides [Polygonum bistortoides] (American bistort), profiled in Medicinal Plants of the Western Mountain States.

A passage from Medicinal Plants of the Western Mountain States:

Use a decoction of Bistort as a tightening mouth and gum rinse. Symptomatically, it addresses spongy and bleeding gums and mouth sores/ulceration (canker sores). Pharyngitis suffers will also derive relief from the gargled warm tea. Likewise, individuals suffering from sinusitis, especially if the situation is chronic with mucus discharge, will benefit from the isotonic nasal wash made with the root tea.