I don't think anyone could stop her from selling them. The question is....is there a market for used hearing aids?
As for used dentures, well....there's an active market for them in a lot of places. In Morocco, we saw a "dentist" operating from a blanket in the square. His instruments were a bottle of paregoric and a pair of dental pliers. He'd pull teeth right there and give you a wad of paregoric-soaked cotton to chomp down on. Want some dentures? Step right up and choose from dozens of used uppers and lowers arrayed on the blanket. "Patients" would just sit down and try them on until they found something that fit.
He had a thriving optometric business on the side, too. Dozens of pair of used glasses for sale.
I suppose if you gave him a day or two, he could probably supply you with anything. You have to admire true entrepreneurs.