Can I keep a toothpaste that helps whiten teeth in my mouth for a long time (w/o eating or drinking)?

Will it help further whiten my teeth? Or do the same if I had just brushed my teeth and rinsed it out then?
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your teeth won't get whiter. no toothpaste will whiten your teeth to a level where you can see the difference with your bare eyes, that's how minimal the whitening effect of toothpastes is. but, if you keep the toothpaste in your mouth, you'll benefit from the fluoride in it. you'll give the fluoride more time to get into your enamel to make your teeth stronger. that'll decrease your likelihood of getting cavities :)
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