Remember when your teeth were bright white? Just look at some old photos – what happened to that sparkly smile? Despite your best efforts to brush and floss regularly, there are structural changes that make teeth appear more yellow as we grow older. First, the outer coating of the tooth (the enamel) gradually becomes thinner. The layer underneath (the dentin) becomes thicker. The dentin is naturally a yellow/brown color so as the enamel thins, the color of the dentin begins to show through more and more. The enamel thins out because of wear and tear and acidic foods.
In addition, once the dentin is exposed, foods that stain the teeth are more easily absorbed by dentin than by enamel. There is also a natural laying down of secondary dentin that affects the light-transmitting property of teeth, resulting in a gradual darkening of the teeth as we age.
Some of the color change is unavoidable. But other causes, like dry mouth and acid reflux, can be treated. Other causes to be avoided are excess sugar, acids and alcohol, bulimia and tooth grinding and clenching. Some foods also discolor the teeth: blackberries, grapes, tea, coffee and red wine. Tobacco will also certainly stain the teeth, as well as contributing to gum disease.