New York Cosmetic Dentist, Dr. Elisa Mello has provided Indulge the following information for getting whiter teeth at any age:

20’s
What’s happening?
Dark foods and drinks might be causing your teeth to yellow. Skipped your daily floss? Teeth may have plaque, making them prone to temporary stains because substances stick to plaque (this is why teeth discolor after a glass of red wine or coffee).
Treatment:
Whitening toothpastes can help with surface stains, but choose one with baking soda and peroxide. Baking soda helps reduce acid in the mouth to curb stains while peroxide lightens. To keep plaque under control, have regular checkups at the dentist, floss daily and brush with an electric toothbrush.

30’s
What’s happening?
In addition to surface stains, you’re now contending with internal stains (as teeth age, the inside portion turns yellow). Everyday wear thins the exterior of the teeth, so more of the dark interior shows. Chewing ice, clenching your jaw and grinding your teeth all exacerbate the problem.
Treatment:
To erase stubborn stains, peroxide needs to stay on teeth longer, so try a peroxide rinse and whitening toothpaste to break up stains. Your best bet for lifting internal stains: a home whitening kit that you leave on for 30 minutes, twice a day for 10 days. If you bleach teeth for months instead of weeks, you can damage them, making your smile look “blue transparent”.

40’s+
What’s happening?
Cumulative damage causes sensitivity and exposes more of the yellow interior. Teeth become sponge-like, soaking up stains and darkening faster. Aging and some medications dry the mouth. With less saliva, teeth are more vulnerable to discoloration.
Treatment:
Continue using bleaching treatments and brush with a whitening toothpaste designed for sensitive teeth. Also try to stimulate saliva by chewing on sugarless gum. Saliva makes teeth shiny so they look brighter.