As you grow older your enamel will start to grow thinner. When this happens your dentin (the underlying layer of your tooth) will start to show through. This is what commonly makes your teeth look darker in color. Of course, there are also other reasons why your teeth may start looking darker as you grow older.
Why Teeth Turn Black
Healthy teeth won't ever turn this color. In fact, you can rest “assured” that if your tooth does turn black, then it's suffered some internal damage – typically in the form of decay or a cavity. One of the most common reasons we see teeth turn black is due to a pulp infection that kills a tooth. When you properly take care of your teeth (regularly brushing with a soft bristle toothbrush and fluoridated toothpaste after flossing then rinsing with mouthwash and seeing us twice a year), this shouldn't happen.
Why Teeth Turn Brown
You may notice your teeth turn brown when you don't take the time to brush plaque off them on a regular basis. This is because the plaque in your mouth will break down your tooth enamel. When this happens, you'll notice that brown stains and cavities will start to form on your teeth.
Tooth decay (a.k.a. cavities) does range in severity. In the beginning, it's usually quite treatable. However, if you leave it untreated, it can really wreak havoc in your mouth – ranging from severe pain to tooth loss. Fortunately, this isn't as big of a problem as it was just a few decades ago.
However, it really shouldn't be a problem at all if you take good care of your oral hygiene and avoid sweet foods and drinks as much as possible. If you still end up with a cavity and we catch it in time, we can simply fill it and you can retain your tooth, which is why maintaining routine dental checkups is so important.