Overtime your teeth change color due to food and drink, age, medication, trauma, and tobacco usage. Coffee, wine, and tea are the main drinks that will make your teeth darker.
Also, over time and through brushing, your enamel will get thinner and more of your yellowish dentin will show through. This also happens with trauma to the mouth area as your teeth react to the injury by producing more dentin.
Medications can darken your teeth such as antihistamines and high blood pressure medications.
Your dentist will work with you to find out the best teeth whitening solution for you. Depending on your lifestyle, schedule, medical issues, and teeth status, your dentist may suggestion one or more teeth whitening options.