The reason why older people's teeth are so yellow is because the outer white tooth enamel wears down over time and then exposes the darker, naturally yellow inner layer called dentin.
Years of chewing, brushing and acid wear make the hard outer tooth enamel thinner and the inner dentin layer grows thicker and more yellow as you get older.
Microscopic cracks in the aging tooth enamel also trap dark pigments from tea, coffee, wine and food and smoking or using tobacco also leaves deep yellow and brown stains on your teeth.
Even certain blood pressure medications, antihistamines and dry mouth can alter your tooth color over time.
Teeth can be healthy but not white as it is normal to not have perfectly white teeth and having perfectly white teeth is not always a sign of healthy teeth.
It's sometimes unhealthy to have perfectly white teeth but not always unhealthy to have perfectly white teeth.
It's not always bad if your teeth are pure white, although having teeth with a pure, unnaturally bright white shade is rarely natural.
Healthy teeth are actually normally an off white, light gray or even slightly yellowish color because the hard outer tooth enamel is also somewhat translucent, which allows the naturally yellow inner layer also known as "dentin" to show through.
Everyone does have a unique natural tooth color that is determined by genetics and thickens of the tooth enamel.
Having off white or even slightly yellow teeth are completely healthy.
The illusion of white teeth, where you often seek sparkling white teeth in media are often a result of cosmetic bleaching, veneers or even digital editing and not standard human biology.
A person with bright white teeth may still have hidden gum disease, cavities or even receding gums.
And conversely, having teeth that are slightly stained or yellow can be structurally very strong and healthy teeth.
There are also risks involved when forcing pure whiteness on your teeth which include tooth enamel wear, tooth sensitivity, and some temporary pain or lasting sensitivity from over the counter whitening.
Achieving a blindingly white shade of teeth often requires use of aggressive chemical bleaching or abrasive products.
And overusing teeth whitening gels or teeth whitening strips can damage the microscopic structure of the tooth enamel, which leads to sharp tooth sensitivity and even irritated gums.
So if your teeth are not pure white they are not always unhealthy and having pure white teeth can be unhealthy in some cases.
Perfect teeth whiteness does not equal perfect tooth health as teeth naturally come in a range of natural shades that is very normal.