It is important to eat a healthy, well-balanced diet, including plenty of fruits and vegetables. Even if some foods are hard and crunchy — an apple, for instance — you can cut them into small pieces. Also remember, unless you can brush immediately afterward, sugary foods should be avoided.
With braces, white marks like these on teeth are the result of decalcification, and are permanent. If you don’t remove the plaque that collects around brackets, between teeth and under the gums, decalcification can be evident within four months.