Per Wikipedia
Dilute sodium hypochlorite (i.e. a mild bleach) is the main constituent of several brands of denture cleanser.
Other ingredients include such chemicals as:
sodium bicarbonate – or baking soda, which alkalizes the water, cleaning the dentures.
citric acid – removes stains.
sodium perborate
sodium polyphosphate
potassium monopersulfate – cleaning and bleaching agent
EDTA