Over time, your teeth can go from white to not-so-bright for a number of reasons.
Food and drink
Coffee, tea and red wine are some major staining culprits. What do they have in common? Intense colour pigments called chromogens that attach to the white, outer part of your tooth (enamel).
Two chemicals found in tobacco create stubborn stains: tar and nicotine. Tar is naturally dark. Nicotine is colourless until it’s mixed with oxygen. Then, it turns into a yellowish, surface-staining substance.
Below the hard, white outer shell of your teeth (enamel) is a softer area called dentin. Over time, the outer enamel layer gets thinner with brushing and more of the yellowish dentin shows through.
If you’ve been hit in the mouth, your tooth may change colour because it reacts to an injury by laying down more dentin, which is a darker layer under the enamel.
Tooth darkening can be a side effect of certain antihistamines, antipsychotics and high blood pressure medications. Young children who are exposed to antibiotics like tetracycline and doxycycline when their teeth are forming (either in the womb or as a baby) may have discoloration of their adult teeth later in life. Chemotherapy and head and neck radiation can also darken teeth.
How does teeth whitening work?
Teeth whitening is a simple process. Whitening products contain one of two tooth bleaches (hydrogen peroxide or carbamide peroxide). These bleaches break stains into smaller pieces, which makes the colour less concentrated and your teeth brighter.
Does whitening work on all teeth?
No, which is why it’s important to talk to your dentist before deciding to whiten your teeth, as whiteners may not correct all types of discoloration. For example, yellow teeth will probably bleach well, brown teeth may not respond as well and teeth with grey tones may not bleach at all. Whitening will not work on caps, veneers, crowns or fillings. It also won’t be effective if your tooth discoloration is caused by medications or a tooth injury.