Darkening in the teeth is often caused by imbibing liquids such as tea, wine, and coffee, though the general process of aging can also play a role. Morning breath is usually caused by plaque on the teeth, around the gums, and on the tongue. To have a better chance at stopping morning breath in its tracks, before you go to bed, you should brush your teeth, floss, and try to clean your tongue with your toothbrush. Numerous factors such as trauma, vigorous brushing, smoking, and consumption of spicy foods can contribute to the development of canker sores.