Binders, Moisturizers, Preservatives, and Colors
The remaining ingredients in toothpaste perform functions unrelated to cleaning the teeth. Toothpastes need something to keep the solid and the liquid ingredients together, and a binding agent performs this function. Most such agents are some form of cellulose, a gel, or an extract of seaweed. Without the binder, the toothpaste would separate into a liquid portion and a sort of mush and would have to be stirred, like paint, before each use.
In addition, moisturizers keep the toothpaste from drying out. The most commonly used moisturizers are glycerin and sorbitol.
Whenever the cap is left off the toothpaste tube, molds or bacteria can get inside. Most manufacturers add a preservative such as methylparaben or propylparaben to the toothpaste to prevent the microbes' growth.
To make toothpaste visually appealing, manufacturers add coloring agents, which usually are food colorings. Some coloring agents are natural, and others are artificial. White, pink, green, and blue are the favored colors of toothpaste. White toothpastes often contain titanium dioxide, a brilliant white pigment used in some paints, to make the toothpaste appear whiter and brighter.