Sara Davis unpacks the dominance of mint flavoring in the world of dental hygiene:
It’s the sensation, more than the scent or the taste, that causes us to associate mint with clean mouths. Mint makes the mouth feel cold. That "fresh" sensation is a thermal illusion: the actual temperature of your mouth doesn’t change.
Mouths contain particular cells that that activate in the presence of hot or cold: the condition of extreme temperature "turns on" the cell, which then sends a message to the brain that the mouth is rather hot or rather cold. But menthol also "turns on" these cells, which send their message to the brain as directed, and we experience a coolness in the mouth that isn’t there.
By itself, mint doesn’t make the mouth a less suitable environment for germs; it’s the abrasives in toothpastes or the alcohols in mouthwashes that do the dirty work. But it’s easy to see how minty freshness became associated with cleanliness: the illusory change of temperature and the sharp, distinctive taste remind us more of cleaning agents than candy.